- Email: [email protected]
Post-thoracotomy epidural vs paravertebral analgesia
Bririslz Jocrriiul o j Ailcresthesin 84 (2): 289-95 (2000)
Correspondence Post-thoracotomy analgesia
epidural
vs
paravertebral
Richardson J, Sabanathan S. Jones J, Shah RD, Cheema S, Mearns AJ. A prospective, randomized comparison of preoperative and continuous balanced epidural o r paravertebral bupivacaine on post-thoracotomy pain, pulmonary function and stress responses. B r j Anoesth 1999; 83:
387-92 Tejwani GA, Rattan AK, McDonald IS. Role of spinal opioid receptors
1992; 36: 7 0 4
Romer HC, Russell GN. A survey o f the practice of thoracic epidural analgesia in the United Kingdom. Anaesthesia I998 53: I0 12-27 Ready LB, Loper KA, Nessly M, W i l d L. Postoperative epidural morphine is safe o n surgical wards. Anesthesiology I99 I ; 75: 453-6
Editor,-I am grateful to Dr Wang for the interest in our study. I appreciate the points he has made, but I must try to justify our choice of epidural regimen. To some extent, better pain relief may have been provided by addition of an opioid to epidural bupivacaine. Pain relief at rest may have been enhanced, but I am doubtful that pain on movement or coughing would have been affected sufficiently to improve pulmonary function (our primary outcome variable). Pain is the most important factor responsible for the post-thoracotomy impairment of pulmonary function' and bedside spirometry is a good indicator of the dynamic capabilities of a chosen analgesic regimen.' I would argue that to undertake research into thoracic or upper abdominal pain without studying pulmonary function is to render the data of lower quality. Pain scores and opioid requirements, which are often the main study outcome variables, are 'soft' data and have little comparative meaning. Pain scores on coughing are better but what exactly is a 'cough'? Is it clearing of the throat or clearing of lung base secretions'? The difference in chest wall movement and hence post-thoracotomy pain exacerbation between these two manoeuvres could be great. I have found only one prospective, randomized study which used a combination of local anaesthetic (bupivacaine) and a opioid (fentanyl) for post-thoracotomy pain and studied spirometric function.' Values were reduced to 50-60% of baseline throughout the study. which are inferior to our values using plain epidural bupivacaine. Opioids are primarily c-fibre inhibitors. In the presence of a large chest wound with severe soft tissue, bony, ligamentous and intercostal nerve damage, pain generation with movement (i.e., with respiration) is probably mediated via intercostal A-delta fibres, although the sympathetic, vagal and phrenic afferents may also be involved.' As opioid receptors are absent from these fibres.5 opioids cannot be expected to provide pain relief with respiration. Administering these drugs by different routes (e.g., neuraxially) does not alter their pharmacology. In my view. it disadvantages the postoperative patient (as opposed to the obstetric patient) if use is made of synergy between epidural local anaesthetic and opioid to allow a reduction in the amount of local anaesthetic. From neurophysiological and neuroendocrine perspectives, I subscribe to the view that the greatest block density possible is the essential starting point if outcomes are to be improved. We need to define clearly our postoperative analgesic goals. Is pain relief per se adequate or should we aim to facilitate chest physiotherapy and postoperative pulmonary function? I am sure that only through the latter can we improve outcome. I do wonder if the analgesia which follows systemic or neuraxial lipophillic opioid administration comes entirely from suppression of sighing and deep breathing. inhibition of the cough reflex and through sedation which attenuates the desire for movement. Provocatively, I have put this question to many speakers at
0 The Board of Management and Trustees of the British Journal of Anaesthesia 2000
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Editor.-I read with interest the article by Richardson and colleagues on post-thoracotomy pain.' The authors compared thoracic paravertebral bupivacaine (bolus of 0 . 5 6 followed by infusion of 0.5%) with thoracic epidural bupivacaine (bolus of 0.25% followed by infusion of 0.25%). Both groups received PCA morphine. The paravertebral group had significantly lower pain scores. better preservation of respiratory function, lower incidence of chest infections, and less nausea, vomiting and hypotension. Thus the authors concluded that with these regimens, paravertebral block was superior to epidural bupivacaine. As many believe that thoracic epidural can provide superior analgesia. these are impressive findings. 1 feel it is important to emphasize that Richardson and colleagues uscd 0 . 2 5 9 bupivacaine without opioids in the epidural group, which is an uncommon practice. A combination of local anaesthetic and opioid administered epidurally has been shown to be synergistic.' Even though the optimal drug combination has yet to be determined, 91% of anaesthetists in the UK use a combination of bupivacaine with either fentanyl or diamorphine.' Choosing to administer only local anaesthetic epidurally effectively handicapped the epidural group in comparison with the paravertebral group. It is conceivable that a combination of an opioid and dilute 0. I % bupivacaine would have resulted in a significantly better outcome in the epidural group. The authors reasoned against using a local anaesthetic-opioid combination regimen for the epidural group on the basis that all patients returned to the general ward and they were unsure how to provide additional rescue opioid analgesia, as a combination of neuraxial and systemic opioids (for example) is known to be a major risk factor of respiratory depression. It is worth noting that 39% of respondents to a survey of thoracic epidural analgesia practice allowed patients to return to a general ward without specific additional nursing resources.' Inadequate analgesia with a correctly placed epidural catheter can generally be managed with an epidural top-up; systemic opioids are usually not needed. The use of epidural morphine, including top-ups, has been shown to be safe on surgical wards.' Paravertebral analgesia is an attractive alternative to epidural analgesia: it is a relatively easy technique and is free of the risk of major neurological injury. We need a study comparing the two methods of analgesia where each technique is individually optimized. Otherwise I am left wondering whether paravertebral analgesia is really as good or maybe even better than thoracic epidural.
in the antinociceptive interactions between intrathecal morphine and bupivacaine. Anesth Anolg I992 84: 726-34 Mouisse J. Hasenbros M, Gielen M, et of. Epidural bupivacaine, sufentanil or the combination for post-thoracotomy pain. Aao Anoesthesiol Scond
Correspondence
I Sabanathan S, Eng J. Mearns A]. Alterations in respiratory mechanics following thoracotomy. J R Coll Surg Edinb 1990; 35: 144-50
2 Richardson J. Sabanathan S. Shah R. Postthoracotomy spirometric lung function: the effect o f analgesia. A review. J Cardiovosc Surg 1999; 40: 445-56 3 George KA. Wright PMC, Chisakuta A. Continuous thoracic epidural fentanyl for post-thoracotomy pain relief: with or without bupivacaine! Anaesthesio I 99 I; 46: 732-6 4 Sabanathan S, Richardson J. Mearns AJ. Management of pain in thoracic surgery. Br J Hosp Med 1993; 50: I 14-20 5 Dickenson AH. Spinal cord pharmacology of pain. Br J Anoesth 1995; 75: 193-200
authors’ rationale for this latter recommendation is that the presence of the cuff in the oral cavity might increase the risk of oropharyngeal morbidity. We are unaware of any data supporting this hypothesis and are concerned that the process of multiple insertion could itself increase the risk of oropharyngeal morbidity. The authors may be able to clarify this matter if they could provide postoperative morbidity data from their study population, as the LMA was inserted into each patient on 2-3 occasions. Third. the authors assessed the presencehbsence of gas leaks around the mask at airway pressures of 10 and 18 cm H 2 0 . Several tests have been described to assess leaks: each differs slightly in accuracy and inter-observer reliabi1ity.j It would be useful to know which test was used. Fourth, in the discussion, the authors indicate that the population studied was Oriental. It i s a commonly held belief that smaller masks are easier to use in Oriental patients. Could the authors comment on the reason for failed placement in the three patients noted in Table 1‘! Were there any data on the time to successful placement between different mask sizes‘? Finally, the authors imply that smaller LMA would commonly be required for tonsillectomy as the larger masks protrude into the oral cavity in 2435% of patients. We consider this recommendation to be weak as the frequency with which the cuff protrudes into the mouth may be less with the flexible LMA (which has a smaller. more mobile tube that might be less likely to push the cuff into the oral cavity) and the presence of the cuff in the oral cavity may not interfere with surgical access to the tonsils. One of the authors (J.B.) has experience of 53 consecutive adult tonsillectomies with the flexible LMA (males size 5 ; females size 4) without any problems relating to surgical access.
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I Asai T, Murao K, Yukawa H. Shingu K. Re-evaluation of appropriate size of the laryngeal mask airway. B r J Anaesth 1999; 83: 478-9 2 Keller C. Puehringer F, Brimacombe J. The influence of cuff volume on oropharyngeal leak pressure and fibreoptic position with the laryngeal mask airway. Br J Anoesth 1998; 8 I : 186-7 3 Keller C. Brimacombe J, Keller K, Morris R. A comparison o f four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. Br J Anaesth 1999; 82: 286-7
Appropriate size of laryngeal mask Editor,-We rend with interest the article by Asai and colleagues reevaluating the appropriate sire of laryngeal mask airway (LMA) in males and females.’ The authors found that larger sizes have a more effective seal, but came up into the mouth more often, which could interfere with tonsillectomy and could increase the risk of sore throat or lingual nerve damage. The value of this study would be greatly improved if the authors could provide additional information. First. the data do not necessarily support these findings as no mention is made of the volume of air used to inflate the cuff. This makes inter-sire comparisons difficult as the efficacy of the seal, fibreoptic position’ and (probably) the extent to which the cuff protrudes into the mouth are related to cuff volume. Second, if the cuff is seen in the oral cavity, we agree that a smaller size should he used for tonsillectomy. but we do not agree that a smaller sire should be used if prolonged surgery is expected. The
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Editor.-In our study,’ we inflated the cuff initially with the recommended maximal volume of air (20 ml for size 3, 30 nil for size 3 and 40 ml for size 5 ) and gradually removed air from the cuff until gas leak around the mask was just prevented. With this method, cuff volume was about 25 ml when the size 4 in females and size 5 in males were used.’ Second, we did not claim that the smaller size should be used if prolonged surgery is expected. Instead, we stated that ‘when the cuff of the laryngeal mask is seen [in the oral cavity], the decision to replace the mask with one size smaller depends 017 .severn/,fxtors. For example, a small mask i s prejernble when . . . surgery of a long duration i s expected’ (authors’ italic).’ The rationale for this claim was, as Dr Brimacombe and colleagues correctly state, ‘the presence of the cuff in the oral cavity might increase the risk of oropharyngeal morbidity’. Of course, one
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scientific meetings and 1 have not yet received an adequate reply. 1 would like to be corrected if my information is erroneous. Having made these comments. 1 am mindful that both of our groups needed additional opioid analgesia and I take this as a spur to continue to refine our regional analgesic techniques. I agree that thoracic epidural analgesia can be continued on the general ward without additional nursing resources. This is indeed the practice i n our own hospital where over the past 8 yr many hundreds of epidurals. using bupivacaine and morphine, have been managed without untoward respiratory incident. To restrict this form of analgesia to only those patients with two to one nursing ratios is a distortion of responsib es. However, we felt that deviation from this (our standard) practice was necessary for the sake of our study. We had to circumvent any barrier, albeit unwittingly imposed, between the patient and additional analgesia. Additional epidural top-ups could have been given, but this would have involved delay and therefore introduced bias to the detriment of the epidural group and hence our data quality. Obviously. high quality studies are required. The simple question, ’can epidural opioid/local anaesthetic regimes compared with epidural local anaesthetic provide improved post-thoracotomy pulmonary function or improved outcome‘?’needs to be answered. Further small studies with different combinations examining pain scoi-es and side effects are not helpful. I would be interested in taking the dose regimens from the resulting optimal study and comparing them i n our own institution with our paravertebral nerve block based regimen. For ethical reasons, it is not possible for me to try t o answer this question myself.
Correspondence
should consider the increased risk of morbidity associated with multiple insertions. We did not formally study the incidence of postoperative sore throat and thus we cannot provide data regarding this factor. Third, we assessed the presence or absence of air leak by hearing an audible noise around the mask. Fourth, the reason for failed ventilation through the laryngeal mask was the same in the three patients in Table 1-the mask came out of the mouth during infation of the cuff. We did not measure the time taken for insertion of the mask. Finally. the flexible and standard laryngeal inasks have different tube structures. but they have masks of the same specifications. Therefore, theoretically. there should be no differences between the two types of device in the incidence of the inask being seen i n the oral cavity. Dr Brirnacombe’s inforination of unproblematic use of the flexible laryngeal mask in 53 patients is useful. but it niay have been that all of his patients were reasonably tall (patient height was not given in his report).
Editor,-We thank Dr Wildsmith for his interest in our article. We never attempted to discredit the use of local anaesthetic infiltration for intra- and postoperative pain relief. Of course our data do not allow for this. Our purpose was to examine the natural killer (NK) cell response to acute pain per se and to discover if local anaesthesia could modify the response. Thus we were investigating the pathophysiology of pain and not that of surgery. N K cells probably play a role as a first line of defence against certain tumour cells and virus infected cells,’ and an increase in NK cell cytotoxicity (in the experimental situation against a specific tumour cell line) i s taken to reflect an increase in the ability to damage deleterious cells. We noted that local anaesthesia blocked the NK cell response in addition to pain. Therefore, we raised the question if infiltration with local anaesthesia has a beneficial effect. The question has to be taken as one for generating hypotheses and not as a conclusion. The fact that local anaesthesia has been used for many years is not in itself proof of its safety. To our knowledge, there are no studies in humans on the importance of local anaesthetics on tumour dissemination or susceptibility to viral infections.
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I Asai T, Murao K. Yukawa H, Shingu K. Re-evaluation of appropriate size of the laryngeal mask airway. Br J Anaesth 1999; 83: 186-7 2 Asai T, Howell TK. Koga K. Morris S. Appropriate size and inflation of the laryngeal mask airway. Br Anaesth 1998; 80: 4 7 0 4
Local anaesthetic infiltration and natural killer cell cytotoxicity Editor.-The study by Greisen and colleagues demonstrated that infiltration o f local anaesthetic abolished the natural killer cell response to painful stiinulation of abdominal wall skin.’ This i s an observation that cannot be refuted, but I must express serious concern that. on the basis of their results. they question the beneficial effect of local anaesthetic infiltration of surgical fields. and suggest that it may impair the response against certain microbial infections and dissemination of tuinour cells. The battle to improve the quality of surgical pain relief i s difficult enough without such unqualified statements. I would make two specific points. First. the experimental model used was one of acute pain ‘without tissue injury’. I know of n o surgical wound that i s not ociated with tissue iii,jury and therefore would question the validity of the conclusions. I appreciate that a similar study 1cif/7 tissue injury would be unlikely to attract inany volunteers. but that doe5 not make their model clinically relevant. Second, local anaesthetic infiltration has been used for surgical procedures for inore than 100 yr. but there is no evidence that I a i n aware of that it predisposes to bacterial infection or dissemination of turnour cells. Can Greisen and colleagues provide any, and, if so, does that mean that they would have every minor surgical procedure performed tinder general anaesthesia instead’? Perhaps they would revert to using no anaesthesia or analgesia a1 all! Observation is easy. Considering the relevance of the observation i s altogether more difficult. J. A. W. Wildsmith U r i i i . c ~ , s i t f~k , / x r i ~ r r w / iof~ rlritrc.c.fhr,sin Ilrrrlflee. U K
I Greisen J, Hokland M. Grofte T. Hansen PO, Jensen TS. Vilstrup H,
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I Whiteside TL, Herberman RB. Role of human natural killer cells in health and disease. Clin Diagn Lab lmmunol 1994; I : 125-33
2 Biron CA. Natural killer cell regulation during viral infection. Biochem Soc Trans 1997; 25: 687-90
Double-lumen tube placement: protecting the good lung Editor.--I congratulate Cheong and Koh’ for their study that not only questioned accepted practice for double-lumen tube placement but also succeeded in showing that there is, after all, a better way. They used the fibreoptic bronchoscope in the tracheal lumen of a left-sided double-lumen tube to observe, as it was happening, passage of the tube into the left main bronchus and inflation of its bronchial cuff. The twin advantages of speed and certainty of double-lumen tube placement make this a rational approach, especially in the presence of pneumothorax or where there i s a need to protect a good lung from contamination from a diseased lung.’ In the latter situation, however, the advantages may be lost if fibreoptic vision is impaired by the presence in the trachea of purulent secretions or blood. In such cases, I have taught a tube placement procedure that has involved ‘blind’ initial insertion of a left-sided Robertshaw tube as the preferred double-lumen tube. I still believe that the relatively rigid anatomical shape of the Robertshaw reduces the likelihood of its entering the incorrect main bronchus during placement and, more importantly. of its becoming displaced in the course of surgery. I was therefore keen to assess the merit of continuing with my old procedure but with the addition of the fibreoptic bronchoscope placed in the tracheal lumen of the left-sided Robertshaw tube during otherwise ‘blind’ placement. Unfortunately, I find that although the technique works very well for plastic double-lumen
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Tonnesen E. Acute pain induces an instant increase in natural killer cell cytotoxicity in humans and this response is abolished by local anaesthesia. B r J Anaesth 1999; 83: 2 3 5 4 0
Correspondence tubes such as the Mallinckrodt and Sheridan, the twin advantages are much less impressive with the Robertshaw tube. The distance between the bronchial and tracheal orifices of the Robertshaw tube is large in comparison with the plastic tubes. and its anatomical shape as it lies within the trachea serves as an obstruction to both the view and easy and safe advancement of the bronchoscope. Thus the carina and right main bronchial orifice may only be seen after the bronchial component has entered the left main bronchus. The fibreoptic bronchoscope is then useful for confirming that the transverse ‘gutter’ that identities the proximal rim of the inflated bronchial cuff of the Robertshaw lies in the left main bronchus at or just beyond the carina. I also teach that where i t is anticipated that secretions or blood may impede fibreoptic vision. a right-sided Robertshaw should be available i n case the left-sided tube persists in entering the right main bronchus. Thus where protecting a good lung i s paramount. my preferred technique continues to involve the Robertshaw double-lumen tube inserted ‘blind’. but I do intend to modify my regular practice to include seeing the inflated bronchial cuff before rather than after the routine of individual lung ventilation. Ilqxtrrtiiettt of Atrtrc~stlir.c.iti
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Koh KF. Placement o f left-sided double-lumen endobronchial tubes: comparison of clinical and fibreoptic-guided placement. Br J Anaesth 1999; 82: 920-1
Editor.-We are grateful to Dr Pfitzner for his interest in our study. We agree that the use of our technique is hampered in cases where copious secretions or blood are present in the trachobronchial tree. In thesc cases. we merely withdraw the bronchoscope and proceed with blind placement as practised conventionally. Our experience with the Robertshaw double-lumen tube is limited and this typc of endobronchial tube has not been available for some time in our institution. As such we would like to thank Dr Pfitzner for his helpful hints. The bronchoscope can only be an aid to placement of double-lumen tubes; it cannot replace conventional tcchniqties in all cases.
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H. Hack Royal Munchester Cliildtwis Hospitul Manchrstet; U K I Zideman DA. Resuscitation. B r J Anoesth 1999; 83: 157-68 2 Dieckman RA, Vardis R. High-dose epinephrine in paediatric out-ofhospital cardiopulmonary arrest. Pediatrics 1995; 95: 90 I-I 3 3 Schindler MB, Bohn D, Cox P, et 01. Outcome o f out-of-hospital cardiac or respiratory arrest in children. N Engl J Med 1996; 335:
Paediatric Resuscitation Guidelines Editor,-Dr Zideinan’s article concerning paediatric resuscitation and the ILCOR guidelines,’ including the current experimental and clinical evidence on which such recotnmendations are based. provided an excellent and concise review of the subject. However, a recent case has led me to question two statements made in support of the current guidelines. A 3.8-kg male baby, aged 5 days, underwent an exploratory laparotomy and removal of a left suprarenal ttimoiir. Histology subsequently showed it to be a mesoblastic nephrorna. Approximately 20 min after removal of the tumour, the baby suddenly became profoundly bradycardic and hypotensive (arterial saturation remaining normal) and then rapidly suffered an asystolic cardiac arrest. Multiple doses of epinephrine, volume replacement (colloid and blood), sodium bicarbonate and calcium chloride were given (according to currently accepted ILCOR and Resuscitation Council (UK)
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Editor,-I am delighted that Dr Hack has reported this unusual event where a 3.8-kg baby survived multiple doses of epinephrine and ventricular fibrillation without severe neurological damage. At the beginning of my article’ and in the ILCOR statement’ it is explained that both are based on specific evidence where available, or supported on the basis of common sense or ease of teaching and skill retention. The paediatric ILCOR statement includes recommendations reached by consensus of an expert multinational panel. The specific published evidence was declared in the reference list. Dr Hack, by presenting this letter for
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J. Ptitzner
guidelines). After four doses of epinephrine, ventricular fibrillation developed which proved very resistant to treatment. Eventually, after the sixth attempt at defibrillation and following a fifth dose of epinephrine, a slow, broad complex rhythm associated with a spontaneous cardiac output returned. Atropine 20 k g kg-’ produced rapid and sustained improvement in both heart rate and cardiac output. The baby made an excellent recovery and was subsequently discharged home with no signs of neurological impairment. In his review, Dr Zideman stated that ‘no children have survived to discharge who have received more than two doses of epinephrine’. The references used to support this statement studied the results after ‘out of hospital’ arrests where long ‘down times‘ and relatively inadequate resuscitation could be confidently expected.2 Dr Zideman also stated that in the ILCOR guidelines, atropine i s ‘not indicated during resuscitation as the adrenergic effects of epinephrine are considered to over-ride the parasympathetic (vagal) effects of atropine’. The exact cause of this infant’s cardiac arrest i s not known but was probably secondary to relative hypovolaemia with pre-existing impaired ventricular function. Before operation, this baby had been hypertensive requiring treatment with CI and p blockers. Residual adrenergic block may have played a role in the aetiology of the cardiac arrest, in addition to the requirements for high doses of epinephrine. The effective response to atropine with such high circulating concentrations of catecholamines is also surprising. Perhaps residual p block was a contributory factor? The prompt recognition and treatment of this asystolic arrest was undoubtedly responsible for the eventual successful outcome. Clearly, such a short period between onset and effective treatment is highly unusual, especially in an ‘out of hospital’ situation and only adds strength to the emphasis placed on the early recognition and treatment of the critically ill child, as taught in resuscitation courses (e.g. Paediatric Advanced Life Support and Advanced Paediatric Life Support). The guidelines recommended by the ILCOR and Resuscitation Council (UK) should be used but not rigidly adhered to without consideration of each individual case. Indeed, within the current guidelines, flexibility in therapy is ‘allowed’ when you ‘consider and correct reversible causes’. Of course, this also requires flexibility of thought on the part of those leading the resuscitation. The potentially huge disparity in outcome between individual resuscitation cases depending on their aetiology and location. as illustrated by the case report here, must surely encourage a more cautionary approach to the use of such sweeping statements when associated with such widely read and important guidelines.
Correrpondence
I Zideman. D A . Resuscitation. B r j Anoesth 1999; 83: 157-68 2 Nadkarni V. Hazinski MF, Zideman DA, et 01. Paediatric life support: an advisory statement by the Paediatric Life Support Working Group of the International Liaison Committee on Resuscitation. Resuscitation 1997; 34: I 15-27 3 Zaritsky A. Nadkarni V. Hazinski MF. et 01. and the Paediatric Utstein Consensus Panel. Recommended guidelines for uniform reporting o f paediatric advanced life support: the paediatric Utstein style. Resuscitotion 1995; 30: 95-1 I 6
that this is a typing error and that the author means to suggest that edrophonium has a higher ED50 in children than in adults.‘ For this reason, the author suggests the use of higher doses of edrophonium for antagonism in infants and children. These studies, however, were carried out under steady-state infusion of tubocurarine and not during the recovery phase from the newer non-depolarizing agents. Moreover, there was no significant difference in the dose of edrophonium required to antagonize tubocurarine-induced neuromuscular block in children and adults.6 In contrast, several studies have shown that neostigrnine antagonizes residual non-depolarizing neuromuscular block more effectively in children than in adults.’-’ Debaene, Meistelman and d’Hollander’ showed that, when twitch height recovered to 10% of control after vecuronium, neostigmine 30 ~g kg-’ had a more rapid onset in children than in adults, and that a TOF of 0.7 was obtained in less than 10 min in all patients, including infants. The dose of neostigmine to effectively antagonize 90% block produced by rocuronium is indeed smaller in children (mean 7 pg kg-’) than in adults (56 pg kg-1).8 The effects of 2 X EDg5of rocuronium could effectively be antagonized in infants with neostigmine 20 pg kg-1.9 With inivacurium there may be an argument for the use of edrophonium as it slows the hydrolysis of mivacurium by plasma cholinesterase less than neostigmine. However, until this issue is resolved, we agree with the author’s recommendation of not antagonizing profound mivacuriun-induced block. In summary, we feel that there are little convincing scientific data to prefer edrophoniuin to neostigmine in paediatric patients. Indeed, with the new shorter acting neuromuscular blocking agents, there may be some advantage to the use of neostigmine over edrophonium. J. J. Driessen E. N. Robertson L. H. D. J. Booij Depcirtrnent (fAnnesthesiology Acadernic Hospifal Nijrizrgeri Nijinegerr. The Nrthrrlnritls
Which is better in children: edrophonium or neostigmine? Editor,-We read with interest the review article by Fisher’ on neurornuscular blocking agents in poediatric anaesthesia. It was a concisc summary of the use of these agents in pediatric practice today. The author’s preference for edrophonium over neostigmine, however. did not seem to be a true reflection of what is known about antagonism of neuromuscular block in children. There have been few comparative studies in children of the speed of action of edrophonium and neostigmine. In comparable mg per kg doses, recovery from an intense atracurium-induced neuroinuscular block in children is faster after neostigmine than edrophonium.’ In adults. it has been shown that in the reversal of profound block produced by vecuronium or atracurium, neostigmine is more effective than edrophonium and its maximal effect is reached more quickly. even though edrophonium is faster in its initial onset.? Monitoring of the depth of neuromuscular bloch in infants and children is technically more difficult and not perhaps ax widespread as in Dr Fisher’s department. This suggests that the chance of profound neuromuscular block at the end of surgery is greater in pediatric anaesthetic practice. Neostigmine would therefore be a better choice than edrophonium. In his article. Fisher stated that less neostigmine is needed in children than in adults, and quoted Fisher and colleagues.’ Quoting the same article.’ he then stated that the EDSO of neostigmine for antagonism was greater for children than for adults. It is possible
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Fisher D M . Neuromuscular blocking agents in paediatric anaesthesia. B r J Anoesth 1999; 83: 58-64 Gwinnutt CL, Walker RWM. Meakin G. Antagonism of intense atracurium-induced neuromuscular block in children. Br J Anoesth 1991; 67: 13-6 Caldwell JE, Robertson EN, Baird WLM. Antagonism of profound neuromuscular blockade induced by vecuronium o r atracurium. Comparison o f neostigmine with edrophonium. B r j Anoesth 1986; 58: 1285-9 Caldwell JE. Robertson EN, Baird WLM. Antagonism o f vecuronium and atracurium: comparison of neostigmine and edrophonium administered at 5% twitch height recovery. Br j Anoesth 1987; 59: 478-8 I Fisher DM, Cronelly R. Miller RD, Sharma M. The neuromuscular pharmacology o f neostigmine in infants and children. Anesthesiology 1983;59: 220-5 Fisher DM. Cronelly R, Sharma M, Miller RD. Clinical pharmacology of edrophonium in infants and children. Anesthesiology I 9 8 4 6 I : 428-33 Debaene 6,Meistelman C, d’Hollander A. Recovery from vecuronium neuromuscular blockade following neostigmine administration in infants, children and adults during halothane anaesthesia. Anesthesiology 1989; 71: 840-4 Abdulatif M, Mowafi H, Al-Ghamdi A, El-Sanabary M. Dose-response relationships for neostigmine antagonism of rocuronium-induced neuromuscular block in children and adults. Br J Anoesth 1996; 77: 710-15 Leuwer M, Motsch J, Schledt U. et ol. Dose-response, time course o f
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publication. has therefore added to the data source and the results that he has reported would be considered, together with those reported via published pediatric Utstein template3 reports, at the next review. The paediatric resuscitation guidelines should not be considered as rigid protocols. I note that in his report, Dr Hack adhered to the recommended guidelines initially. In some events. especially whcn the cau5e is treatable and there is little or no monitored hypoxia. it is appropriate to continue resuscitation and to use any reasonable resource or treatment available. I n this case, multiple administrations of epinephrine (dose not reported) were successful in restoring a spontaneous circulation. The use of atropine in the treatment of the resulting peri-arrest bradycardia was appropriate, despite the anomaly of the previous multiple doses of epinephrine. Finally, may 1 suggest that the success of this event was a result of sustained maintenance of tissue oxygenation. It cannot be emphasized sufficiently that sustained delivery of oxygen to this infant‘s tissues was critical to the successful outcome. I would hope that the publication of this letter will encourage others to report their pediatric resuscitation events, either as individual case reports or using the Utstein template,’ so that we can continue to improve the practice of paediatric life support.
Correspondence
neuromuscular block in children and adults. Br J Anoesth 1996; 77: 710-15 Leuwer M, Motsch J, Schledt U, et 01. Dose-response, time course o f action and recovery o f Ong 9426 (rocuronium) in infants during halothane anaesthesia. Br J Anoesth 1994; 73: 7 16P Fisher DM, Cronnelly R. Miller RD, Sharma M. Neuromuscular pharmacology of neostigmine in infants and children. Anesthesiology 1983;59: 220-5 Cronnelly R. Morris RB. Miller RD. Edrophonium: Duration of action and atropine requirement in humans during halothane anesthesia. Anesthesiology 1982; 57: 26 1-6 Miller RD, VanNyhuis LS, Eger El 11, et 01. Comparative times t o peak effect and durations o f action o f neostigmine and pyridostigmine. Anesthesiology I 9 7 4 4 I: 27-33
action and recovery o f O R G 9426 (rocuronium) in infants during halothane anaesthesia. Br J Anoesth 1994; 73: 7 l6P
Bacterial contamination of needles used for spinal and epidural anaesthesia Editor.-We read with interest the article by Raedler and colleagues regarding contamination of needles used during central neural block.' It is cause for concern that almost 18% of the needles showed evidence of bacterial contamination, even though no patient developed infective complications. There are points we would like to make with regard to the aseptic technique which may explain the high incidence of bacterial colonization. First. it is not clear if the 10% polyvidone-iodine (PI) used for skin preparation came from single or multiple-use containers. There is evidence to show that multiple-use PI bottles in normal use may become contaminated by bacteria and also that the solution is less effective than PI from previously unopened bottles.2 Also. alcohol chlorhexidine is a commonly used alternative to PI for skin disinfection and has been shown to reduce the rate of central venous catheter colonization and catheter-related sepsis compared with PI.3 There are no studies comparing the two solutions for skin disinfection before central neural block, but we would suggest that it should be used in preference to PI. Second, the authors refer to the use of sterile gloves and drapes, but no mention is made as to whether face masks were worn. While we accept that the use of face masks has not been shown to decrease the incidence of postoperative surgical wound i~ifection.~ there is evidence to suggest that they decrease bacterial dispersion' and that their use can reduce the incidence of catheterrelated infections during insertion.' We suggest that the use of alcohol chlorhexidine instead of 10% PI and wearing of face masks for central neural block may reduce the incidence of bacterial contamination of spinal and epidural needles.
'
J. Whiteside J . A. W. Wildsmith Uriiwr-s;ry Drpnrrriirrit c?f'Aiitrestlirsirr Dirritlec., U K
Gwinnutt CL, Walker RW. Meakin G. Antagonism of intense atracurium-induced neuromuscular block in children. Br J Anoesth 1991; 67: 13-16 Fisher DM. Cronnelly R. Sharma M. Miller RD. Clinical pharmacology of edrophonium in infants and children. Anesthesiology 1984; 6 I:428-33 Debaene B, Meistelman C, d'tiollander A. Recovery from vecuronium neuromuscular blockade following neostigmine administration in infants, children, and adults during halothane anesthesia. Anesthesiology 1989; 71: 8 4 0 4 Abdulatif M. Mowafi ti, al-Ghamdi A, el-Sanabary M. Dose-response relationships for neostigmine antagonism of rocuronium-induced
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Raedler C. Lass Florl C, Puhringer F, et 01. Bacterial contamination of needles used for spinal and epidural anaesthesia. Br J Anoesth 1999; 83: 657-8 Birnbach D, Stein D. Murray 0. Thys D. Sordillo E. Povidone iodine and skin disinfection before initiation of epidural anesthesia. Anesthesiology 1998; 88: 668-72 Mimoz 0, Pieroni L, Lawrence, C. et 01. Prospective, randomized trial o f two antiseptic solutions for prevention of central venous or arterial catheter colonization and infection in intensive care unit patients. Crit Core Med 1996; 24: I 8 18-23 Legras A, Cattier B, Dequin P, Boulain T, Perrotin D. Prospective randomised trial for prevention of vascular catheter infection: Alcohol
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Editor.-Driessen. Robertson and Booij challenge my preference for edrophoniurn over neostigmine. The first issue that they explore is profound block. My review acknowledges that neostigmine i s prel'erred in that setting. Even if they are correct that 'monitoring o f infants i\ tcchnically more difficult', I hope that neuromuscular block is monitored routinely in infants. I also expect that clinicians are able to dihnguish between profound twitch depression at the time of antagonism' (no response to train-of-four stimulation) from the more typical level of recovery (presence of more than one twitch i n response t o train-of-four stimulation). Under these usual conditions. is there evidence to refute my claim that cdrophonitnii works faster'? Driessen. Robertson and Booij detected a typographical error that I mish to correct. The EDSO for edrophonium (not for neostiginine) is larger i n children (233 pg kg-') than in adults ( 1 1 8 pg kg-'). Although the difference was not significant. the larger value and larger variability in children than in adults led to our recommendation 'that paediatric patients receive larger doses of edrophonium (e.g.. I .0 mg kg-I)' than adults. Drieswi. Robertson and Booij then claimed that three studies dcinonstrated that 'neostigmine antagonizes residual nondepolariing neuromumilar block more effectively in children than in adults'. Unfortunately, they mis-state the conclusions of those studics. Debaene. Meistelman and d'Holland3 found no difference between infants. children and adults for recovery of twitch at any time or in the train-of-four response before 10 min. They attribute the improved late train-of-four recovery in children to 'the faster rate o f spontaneous recovery from vecuronium', rathcr than a n effect of the antagonist. The results of Abdulatif and colleagues4 also can be explained by the more rapid spontaneous recobery in children than in adults (as evidenced by their control groups). Lcuuer and colleagues' abstract5 reported that recovery, improved the neostigmine 10 pg kg-', given at 3% time to train-of-four >0.7 in infants (no adults were studied) compared \\ i t h ;I group given no antagonist; however, variability i n recovery rate was quite large (SD exceeded the mean) and no other neostigmine doses were evaluated. Driessen. Robertson and Booij concluded that 'there is little convincing scientific data to prefer edrophonium to neostigmine i n pediatric patients' and suggest that 'with the new shorter acting neuromuscular blocking agents there may be some advantage to the use of neostigmine over edrophonium'. In contrast. studies in children' (' and adults' demonstrate that edrophonium antagonizes 90% block faster t h m neostigmine. Hence, whenever block is not intense and recovery time is important (as is increasingly true in clinical anaesthesia). 1 prefer edrophoniurn i n children.
Correspondence chlorhexidine versus povidone-iodine. Reanimation Urgences 1997; 6: 5-1 I 5 Tunevall T. Postoperative wound infections and surgical face masks: a controlled study. World] Surg I 9 9 I : 15: 383-7 6 Philips J. Fergusson S. Armstrong P. Anderson F. Wildsmith J. Surgical face masks are effective in reducing bacterial contamination caused by dispersal from the upper airway. Br] Anoesth 1992; 69: 407-8 7 Raad I, Hohn D, Gilbreath B. et 01. Prevention of central venous catheter-related infections by using maximal sterile barrier precautions during insertion. Infect Control Hosp Epidemiol 1994; 15: 23 1-8
2
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4
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Editor.-Our aim was to study our practice of administering spinal or epidural anaesthesig; our technique was guided by generally recognized rules. We used aqueous povidone-iodine (PI). Face masks were not used in all cases, but there was no correlation between the use of face masks and needle contamination in our study. We are aware of the study published by Birnbach and colleagues' who found 40% of multiple-use PI bottles to be microbiologically contaminated compared with 5% contamination rate in bottles used for the first time. Hence they suggest singleuse bottles for skin disinfection. Small bottles of PI for single use are not available in our country. Moreover, Birnbach and colleagues stated that none of the organisms isolated from the sponge sticks used for skin disinfection was present in the PI solution, except in one case. Thus contamination is more a problem of normal skin colonization than of contaminated disinfection solutions. We found our multiple-use PI solutions to be free of bacterial growth. However, Birnbach and colleagues speculated that reduced antimicrobial activity of PI solutions from multiple-use bottles might have been the reason for their findings. Another point raised was that alcoholic PI might be superior to aqueous solutions. We found our antimicrobial solutions eradicated bacteria after weeks of use. But our results demonstrated that standards and guidelines must be subject to continuous evaluation. Despite using an aseptic technique, lumbar puncture may contaminate spinal or epidural needles. In line with Birnbach and co-workers. we conclude that indigenous bacterial skin flora is most likely the source of this contamination. Alcoholic solutions may be more effective in this respect.
E. ChojnowAn F l - < ~ l i < ~Ho.\/l;ld /i~l~
Bii\tO/. I'K
I Raedler C. Lass-Florl C. Puhringer F. Kolbitsch Ch, Lingnau W. Benzer
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I Birnbach DJ, Stein DJ, Murray 0, Thys DM, Sordillo EM. Povidone iodine and skin disinfection before initiation of epidural anesthesia. Anesthesiology 1998; 88: 668-72
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Editor.-Raedler and colleagues' described an incidence of 17.9% bacterial contamination of spinal and epidural needles after lumbar puncture of the subarachnoid or epidural space. The authors make (tic important point that despite using an aseptic technique. lumbar puncture may contaminate spinal and epidural needles. Their aseptic technique included skin disinfection with 10% polyvidoneiodine (Braunol 2000). Povidone-iodine is a complex of iodine. the bactericidal component, with polyvinylpyrrolidone (povidone) a synthetic polymer. The common commercial form in the UK is a 10% solution in water (Betadine). h i v i t w studies showed that aqueous povidone-iodine (PI) preparations were superior to alcohol or chlorhexidine preparations when tested for activity against bacteria with increasing dilution.' However. addition of 80% ethanol to 0 5 % chlorhexidine significantly increased its potency and onset of action compared with 10%PI.' The advantages of using alcohol rather than aqueous based solutions are further demonstrated by itz 1,ii.ostudies. Sato. Sakuragi and Dan' excised skin specimens from 60 patients undergoing elective back operations after preparation with either aqueous 10% PI or 0.5% chlorhexidine in 80% ethanol. and cultured staphylococcal species in 32.470 I'S 5.7%. respectively. A further problem. raised by Birnbach and colleagues.' concerns the frequency of bacterial contamination of previously opened multiple-use bottles of aqueous 10% PI. Bacteria were found only in previously opened bottles of which 40% were contaminated. Hence the study recommends single-use containers. PI in an alcoholic solution overcomes the disadvantages of aqueous solution. A comparison of the efficacy of 10% PI ethanol solution and 0.5% chlorhexidine ethanol solution' showed no significant difference in decreasing skin bacterial counts (bacterial reduction rate 95% 1's 93.5%). Complete eradication of indigenous bacteria is impossible using thc currently available skin disinfecting methods. However, to reduce the risk of infectious complications of epidural anaesthesia, attention should focus on any means of prevention, including optimal skin disinfection. Raedler and colleagues do not state if their PI solution was aqueous based or came from previously opened multi-use bottles. They recommend further improvement of hygienic measures but do not include optimization of skin disinfection with an alcoholic solution of 10% PI or 0.5% chlorhexidine.
A. Bacterial contamination of needles used for spinal and epidural anaesthesia. Br J Anoesth 1999; 83: 657-8 Michel D. Zach GA. Antiseptic efficacy of disinfecting solutions in suspension test in vitro against methicillin-resistant Staphylococcus aureus. Pseudomonas aeruginosa and Escherichia coli in pressure sore wounds after spinal cord injury. Dermatology 1997; 195 (Suppl. 2): 36-4 I McLure AR, Gordon J. In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus. J Hosp Infect 1992; 21: 291-9 Sakuragi T, Yanagisawa K. Dan K. Bactericidal activity o f skin disinfectants on methicillin-resistant Staphylococcus aureus. Anesth Analg 1995; 8 I: 555-8 Sat0 S, Sakuragi T. Dan K. Human skin flora as a potential source o f epidural abscess. Anesthesiology 1996; 85: 1276-82 Birnbach DJ, Stein DJ, Murray 0, Thys DM. Sordillo EM. Povidone iodine and skin disinfection before initiation o f epidural anesthesia. Anesthesiology 1998; 88: 668-72 Arata T. Kamitani M, Miyai T, I t 0 M. Antiseptic effects at injection sites. Dermatology 1997; I 9 5 (Suppl. 2): 107-10
Correspondence Post-thoracotomy analgesia
epidural
vs
paravertebral
Richardson J, Sabanathan S. Jones J, Shah RD, Cheema S, Mearns AJ. A prospective, randomized comparison of preoperative and continuous balanced epidural o r paravertebral bupivacaine on post-thoracotomy pain, pulmonary function and stress responses. B r j Anoesth 1999; 83:
387-92 Tejwani GA, Rattan AK, McDonald IS. Role of spinal opioid receptors
1992; 36: 7 0 4
Romer HC, Russell GN. A survey o f the practice of thoracic epidural analgesia in the United Kingdom. Anaesthesia I998 53: I0 12-27 Ready LB, Loper KA, Nessly M, W i l d L. Postoperative epidural morphine is safe o n surgical wards. Anesthesiology I99 I ; 75: 453-6
Editor,-I am grateful to Dr Wang for the interest in our study. I appreciate the points he has made, but I must try to justify our choice of epidural regimen. To some extent, better pain relief may have been provided by addition of an opioid to epidural bupivacaine. Pain relief at rest may have been enhanced, but I am doubtful that pain on movement or coughing would have been affected sufficiently to improve pulmonary function (our primary outcome variable). Pain is the most important factor responsible for the post-thoracotomy impairment of pulmonary function' and bedside spirometry is a good indicator of the dynamic capabilities of a chosen analgesic regimen.' I would argue that to undertake research into thoracic or upper abdominal pain without studying pulmonary function is to render the data of lower quality. Pain scores and opioid requirements, which are often the main study outcome variables, are 'soft' data and have little comparative meaning. Pain scores on coughing are better but what exactly is a 'cough'? Is it clearing of the throat or clearing of lung base secretions'? The difference in chest wall movement and hence post-thoracotomy pain exacerbation between these two manoeuvres could be great. I have found only one prospective, randomized study which used a combination of local anaesthetic (bupivacaine) and a opioid (fentanyl) for post-thoracotomy pain and studied spirometric function.' Values were reduced to 50-60% of baseline throughout the study. which are inferior to our values using plain epidural bupivacaine. Opioids are primarily c-fibre inhibitors. In the presence of a large chest wound with severe soft tissue, bony, ligamentous and intercostal nerve damage, pain generation with movement (i.e., with respiration) is probably mediated via intercostal A-delta fibres, although the sympathetic, vagal and phrenic afferents may also be involved.' As opioid receptors are absent from these fibres.5 opioids cannot be expected to provide pain relief with respiration. Administering these drugs by different routes (e.g., neuraxially) does not alter their pharmacology. In my view. it disadvantages the postoperative patient (as opposed to the obstetric patient) if use is made of synergy between epidural local anaesthetic and opioid to allow a reduction in the amount of local anaesthetic. From neurophysiological and neuroendocrine perspectives, I subscribe to the view that the greatest block density possible is the essential starting point if outcomes are to be improved. We need to define clearly our postoperative analgesic goals. Is pain relief per se adequate or should we aim to facilitate chest physiotherapy and postoperative pulmonary function? I am sure that only through the latter can we improve outcome. I do wonder if the analgesia which follows systemic or neuraxial lipophillic opioid administration comes entirely from suppression of sighing and deep breathing. inhibition of the cough reflex and through sedation which attenuates the desire for movement. Provocatively, I have put this question to many speakers at
0 The Board of Management and Trustees of the British Journal of Anaesthesia 2000
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Editor.-I read with interest the article by Richardson and colleagues on post-thoracotomy pain.' The authors compared thoracic paravertebral bupivacaine (bolus of 0 . 5 6 followed by infusion of 0.5%) with thoracic epidural bupivacaine (bolus of 0.25% followed by infusion of 0.25%). Both groups received PCA morphine. The paravertebral group had significantly lower pain scores. better preservation of respiratory function, lower incidence of chest infections, and less nausea, vomiting and hypotension. Thus the authors concluded that with these regimens, paravertebral block was superior to epidural bupivacaine. As many believe that thoracic epidural can provide superior analgesia. these are impressive findings. 1 feel it is important to emphasize that Richardson and colleagues uscd 0 . 2 5 9 bupivacaine without opioids in the epidural group, which is an uncommon practice. A combination of local anaesthetic and opioid administered epidurally has been shown to be synergistic.' Even though the optimal drug combination has yet to be determined, 91% of anaesthetists in the UK use a combination of bupivacaine with either fentanyl or diamorphine.' Choosing to administer only local anaesthetic epidurally effectively handicapped the epidural group in comparison with the paravertebral group. It is conceivable that a combination of an opioid and dilute 0. I % bupivacaine would have resulted in a significantly better outcome in the epidural group. The authors reasoned against using a local anaesthetic-opioid combination regimen for the epidural group on the basis that all patients returned to the general ward and they were unsure how to provide additional rescue opioid analgesia, as a combination of neuraxial and systemic opioids (for example) is known to be a major risk factor of respiratory depression. It is worth noting that 39% of respondents to a survey of thoracic epidural analgesia practice allowed patients to return to a general ward without specific additional nursing resources.' Inadequate analgesia with a correctly placed epidural catheter can generally be managed with an epidural top-up; systemic opioids are usually not needed. The use of epidural morphine, including top-ups, has been shown to be safe on surgical wards.' Paravertebral analgesia is an attractive alternative to epidural analgesia: it is a relatively easy technique and is free of the risk of major neurological injury. We need a study comparing the two methods of analgesia where each technique is individually optimized. Otherwise I am left wondering whether paravertebral analgesia is really as good or maybe even better than thoracic epidural.
in the antinociceptive interactions between intrathecal morphine and bupivacaine. Anesth Anolg I992 84: 726-34 Mouisse J. Hasenbros M, Gielen M, et of. Epidural bupivacaine, sufentanil or the combination for post-thoracotomy pain. Aao Anoesthesiol Scond
Correspondence
I Sabanathan S, Eng J. Mearns A]. Alterations in respiratory mechanics following thoracotomy. J R Coll Surg Edinb 1990; 35: 144-50
2 Richardson J. Sabanathan S. Shah R. Postthoracotomy spirometric lung function: the effect o f analgesia. A review. J Cardiovosc Surg 1999; 40: 445-56 3 George KA. Wright PMC, Chisakuta A. Continuous thoracic epidural fentanyl for post-thoracotomy pain relief: with or without bupivacaine! Anaesthesio I 99 I; 46: 732-6 4 Sabanathan S, Richardson J. Mearns AJ. Management of pain in thoracic surgery. Br J Hosp Med 1993; 50: I 14-20 5 Dickenson AH. Spinal cord pharmacology of pain. Br J Anoesth 1995; 75: 193-200
authors’ rationale for this latter recommendation is that the presence of the cuff in the oral cavity might increase the risk of oropharyngeal morbidity. We are unaware of any data supporting this hypothesis and are concerned that the process of multiple insertion could itself increase the risk of oropharyngeal morbidity. The authors may be able to clarify this matter if they could provide postoperative morbidity data from their study population, as the LMA was inserted into each patient on 2-3 occasions. Third. the authors assessed the presencehbsence of gas leaks around the mask at airway pressures of 10 and 18 cm H 2 0 . Several tests have been described to assess leaks: each differs slightly in accuracy and inter-observer reliabi1ity.j It would be useful to know which test was used. Fourth, in the discussion, the authors indicate that the population studied was Oriental. It i s a commonly held belief that smaller masks are easier to use in Oriental patients. Could the authors comment on the reason for failed placement in the three patients noted in Table 1‘! Were there any data on the time to successful placement between different mask sizes‘? Finally, the authors imply that smaller LMA would commonly be required for tonsillectomy as the larger masks protrude into the oral cavity in 2435% of patients. We consider this recommendation to be weak as the frequency with which the cuff protrudes into the mouth may be less with the flexible LMA (which has a smaller. more mobile tube that might be less likely to push the cuff into the oral cavity) and the presence of the cuff in the oral cavity may not interfere with surgical access to the tonsils. One of the authors (J.B.) has experience of 53 consecutive adult tonsillectomies with the flexible LMA (males size 5 ; females size 4) without any problems relating to surgical access.
Cciirrzs Btrre H o s p i f d , A i r ~ f ~ l i u
C. Ke,,er Depnrtrizerzt
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I Asai T, Murao K, Yukawa H. Shingu K. Re-evaluation of appropriate size of the laryngeal mask airway. B r J Anaesth 1999; 83: 478-9 2 Keller C. Puehringer F, Brimacombe J. The influence of cuff volume on oropharyngeal leak pressure and fibreoptic position with the laryngeal mask airway. Br J Anoesth 1998; 8 I : 186-7 3 Keller C. Brimacombe J, Keller K, Morris R. A comparison o f four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. Br J Anaesth 1999; 82: 286-7
Appropriate size of laryngeal mask Editor,-We rend with interest the article by Asai and colleagues reevaluating the appropriate sire of laryngeal mask airway (LMA) in males and females.’ The authors found that larger sizes have a more effective seal, but came up into the mouth more often, which could interfere with tonsillectomy and could increase the risk of sore throat or lingual nerve damage. The value of this study would be greatly improved if the authors could provide additional information. First. the data do not necessarily support these findings as no mention is made of the volume of air used to inflate the cuff. This makes inter-sire comparisons difficult as the efficacy of the seal, fibreoptic position’ and (probably) the extent to which the cuff protrudes into the mouth are related to cuff volume. Second, if the cuff is seen in the oral cavity, we agree that a smaller size should he used for tonsillectomy. but we do not agree that a smaller sire should be used if prolonged surgery is expected. The
Sarrain
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Editor.-In our study,’ we inflated the cuff initially with the recommended maximal volume of air (20 ml for size 3, 30 nil for size 3 and 40 ml for size 5 ) and gradually removed air from the cuff until gas leak around the mask was just prevented. With this method, cuff volume was about 25 ml when the size 4 in females and size 5 in males were used.’ Second, we did not claim that the smaller size should be used if prolonged surgery is expected. Instead, we stated that ‘when the cuff of the laryngeal mask is seen [in the oral cavity], the decision to replace the mask with one size smaller depends 017 .severn/,fxtors. For example, a small mask i s prejernble when . . . surgery of a long duration i s expected’ (authors’ italic).’ The rationale for this claim was, as Dr Brimacombe and colleagues correctly state, ‘the presence of the cuff in the oral cavity might increase the risk of oropharyngeal morbidity’. Of course, one
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scientific meetings and 1 have not yet received an adequate reply. 1 would like to be corrected if my information is erroneous. Having made these comments. 1 am mindful that both of our groups needed additional opioid analgesia and I take this as a spur to continue to refine our regional analgesic techniques. I agree that thoracic epidural analgesia can be continued on the general ward without additional nursing resources. This is indeed the practice i n our own hospital where over the past 8 yr many hundreds of epidurals. using bupivacaine and morphine, have been managed without untoward respiratory incident. To restrict this form of analgesia to only those patients with two to one nursing ratios is a distortion of responsib es. However, we felt that deviation from this (our standard) practice was necessary for the sake of our study. We had to circumvent any barrier, albeit unwittingly imposed, between the patient and additional analgesia. Additional epidural top-ups could have been given, but this would have involved delay and therefore introduced bias to the detriment of the epidural group and hence our data quality. Obviously. high quality studies are required. The simple question, ’can epidural opioid/local anaesthetic regimes compared with epidural local anaesthetic provide improved post-thoracotomy pulmonary function or improved outcome‘?’needs to be answered. Further small studies with different combinations examining pain scoi-es and side effects are not helpful. I would be interested in taking the dose regimens from the resulting optimal study and comparing them i n our own institution with our paravertebral nerve block based regimen. For ethical reasons, it is not possible for me to try t o answer this question myself.
Correspondence
should consider the increased risk of morbidity associated with multiple insertions. We did not formally study the incidence of postoperative sore throat and thus we cannot provide data regarding this factor. Third, we assessed the presence or absence of air leak by hearing an audible noise around the mask. Fourth, the reason for failed ventilation through the laryngeal mask was the same in the three patients in Table 1-the mask came out of the mouth during infation of the cuff. We did not measure the time taken for insertion of the mask. Finally. the flexible and standard laryngeal inasks have different tube structures. but they have masks of the same specifications. Therefore, theoretically. there should be no differences between the two types of device in the incidence of the inask being seen i n the oral cavity. Dr Brirnacombe’s inforination of unproblematic use of the flexible laryngeal mask in 53 patients is useful. but it niay have been that all of his patients were reasonably tall (patient height was not given in his report).
Editor,-We thank Dr Wildsmith for his interest in our article. We never attempted to discredit the use of local anaesthetic infiltration for intra- and postoperative pain relief. Of course our data do not allow for this. Our purpose was to examine the natural killer (NK) cell response to acute pain per se and to discover if local anaesthesia could modify the response. Thus we were investigating the pathophysiology of pain and not that of surgery. N K cells probably play a role as a first line of defence against certain tumour cells and virus infected cells,’ and an increase in NK cell cytotoxicity (in the experimental situation against a specific tumour cell line) i s taken to reflect an increase in the ability to damage deleterious cells. We noted that local anaesthesia blocked the NK cell response in addition to pain. Therefore, we raised the question if infiltration with local anaesthesia has a beneficial effect. The question has to be taken as one for generating hypotheses and not as a conclusion. The fact that local anaesthesia has been used for many years is not in itself proof of its safety. To our knowledge, there are no studies in humans on the importance of local anaesthetics on tumour dissemination or susceptibility to viral infections.
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I Asai T, Murao K. Yukawa H, Shingu K. Re-evaluation of appropriate size of the laryngeal mask airway. Br J Anaesth 1999; 83: 186-7 2 Asai T, Howell TK. Koga K. Morris S. Appropriate size and inflation of the laryngeal mask airway. Br Anaesth 1998; 80: 4 7 0 4
Local anaesthetic infiltration and natural killer cell cytotoxicity Editor.-The study by Greisen and colleagues demonstrated that infiltration o f local anaesthetic abolished the natural killer cell response to painful stiinulation of abdominal wall skin.’ This i s an observation that cannot be refuted, but I must express serious concern that. on the basis of their results. they question the beneficial effect of local anaesthetic infiltration of surgical fields. and suggest that it may impair the response against certain microbial infections and dissemination of tuinour cells. The battle to improve the quality of surgical pain relief i s difficult enough without such unqualified statements. I would make two specific points. First. the experimental model used was one of acute pain ‘without tissue injury’. I know of n o surgical wound that i s not ociated with tissue iii,jury and therefore would question the validity of the conclusions. I appreciate that a similar study 1cif/7 tissue injury would be unlikely to attract inany volunteers. but that doe5 not make their model clinically relevant. Second, local anaesthetic infiltration has been used for surgical procedures for inore than 100 yr. but there is no evidence that I a i n aware of that it predisposes to bacterial infection or dissemination of turnour cells. Can Greisen and colleagues provide any, and, if so, does that mean that they would have every minor surgical procedure performed tinder general anaesthesia instead’? Perhaps they would revert to using no anaesthesia or analgesia a1 all! Observation is easy. Considering the relevance of the observation i s altogether more difficult. J. A. W. Wildsmith U r i i i . c ~ , s i t f~k , / x r i ~ r r w / iof~ rlritrc.c.fhr,sin Ilrrrlflee. U K
I Greisen J, Hokland M. Grofte T. Hansen PO, Jensen TS. Vilstrup H,
29 I
I Whiteside TL, Herberman RB. Role of human natural killer cells in health and disease. Clin Diagn Lab lmmunol 1994; I : 125-33
2 Biron CA. Natural killer cell regulation during viral infection. Biochem Soc Trans 1997; 25: 687-90
Double-lumen tube placement: protecting the good lung Editor.--I congratulate Cheong and Koh’ for their study that not only questioned accepted practice for double-lumen tube placement but also succeeded in showing that there is, after all, a better way. They used the fibreoptic bronchoscope in the tracheal lumen of a left-sided double-lumen tube to observe, as it was happening, passage of the tube into the left main bronchus and inflation of its bronchial cuff. The twin advantages of speed and certainty of double-lumen tube placement make this a rational approach, especially in the presence of pneumothorax or where there i s a need to protect a good lung from contamination from a diseased lung.’ In the latter situation, however, the advantages may be lost if fibreoptic vision is impaired by the presence in the trachea of purulent secretions or blood. In such cases, I have taught a tube placement procedure that has involved ‘blind’ initial insertion of a left-sided Robertshaw tube as the preferred double-lumen tube. I still believe that the relatively rigid anatomical shape of the Robertshaw reduces the likelihood of its entering the incorrect main bronchus during placement and, more importantly. of its becoming displaced in the course of surgery. I was therefore keen to assess the merit of continuing with my old procedure but with the addition of the fibreoptic bronchoscope placed in the tracheal lumen of the left-sided Robertshaw tube during otherwise ‘blind’ placement. Unfortunately, I find that although the technique works very well for plastic double-lumen
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T. A u i K. Shingu KtrH ctri M d i c . o / L’fliIY~r3ifV Mor~igrrdri c‘it\: Osnktr. Jtqxrrr
Tonnesen E. Acute pain induces an instant increase in natural killer cell cytotoxicity in humans and this response is abolished by local anaesthesia. B r J Anaesth 1999; 83: 2 3 5 4 0
Correspondence tubes such as the Mallinckrodt and Sheridan, the twin advantages are much less impressive with the Robertshaw tube. The distance between the bronchial and tracheal orifices of the Robertshaw tube is large in comparison with the plastic tubes. and its anatomical shape as it lies within the trachea serves as an obstruction to both the view and easy and safe advancement of the bronchoscope. Thus the carina and right main bronchial orifice may only be seen after the bronchial component has entered the left main bronchus. The fibreoptic bronchoscope is then useful for confirming that the transverse ‘gutter’ that identities the proximal rim of the inflated bronchial cuff of the Robertshaw lies in the left main bronchus at or just beyond the carina. I also teach that where i t is anticipated that secretions or blood may impede fibreoptic vision. a right-sided Robertshaw should be available i n case the left-sided tube persists in entering the right main bronchus. Thus where protecting a good lung i s paramount. my preferred technique continues to involve the Robertshaw double-lumen tube inserted ‘blind’. but I do intend to modify my regular practice to include seeing the inflated bronchial cuff before rather than after the routine of individual lung ventilation. Ilqxtrrtiiettt of Atrtrc~stlir.c.iti
~ V ~ t - rIlVt ~ , . s r ~ r A t 1d d n i d e H d r h S r r . i ~ i ~ c Atlel~idr.Sottth A m r d i i t
I Cheong KF,
Koh KF. Placement o f left-sided double-lumen endobronchial tubes: comparison of clinical and fibreoptic-guided placement. Br J Anaesth 1999; 82: 920-1
Editor.-We are grateful to Dr Pfitzner for his interest in our study. We agree that the use of our technique is hampered in cases where copious secretions or blood are present in the trachobronchial tree. In thesc cases. we merely withdraw the bronchoscope and proceed with blind placement as practised conventionally. Our experience with the Robertshaw double-lumen tube is limited and this typc of endobronchial tube has not been available for some time in our institution. As such we would like to thank Dr Pfitzner for his helpful hints. The bronchoscope can only be an aid to placement of double-lumen tubes; it cannot replace conventional tcchniqties in all cases.
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H. Hack Royal Munchester Cliildtwis Hospitul Manchrstet; U K I Zideman DA. Resuscitation. B r J Anoesth 1999; 83: 157-68 2 Dieckman RA, Vardis R. High-dose epinephrine in paediatric out-ofhospital cardiopulmonary arrest. Pediatrics 1995; 95: 90 I-I 3 3 Schindler MB, Bohn D, Cox P, et 01. Outcome o f out-of-hospital cardiac or respiratory arrest in children. N Engl J Med 1996; 335:
Paediatric Resuscitation Guidelines Editor,-Dr Zideinan’s article concerning paediatric resuscitation and the ILCOR guidelines,’ including the current experimental and clinical evidence on which such recotnmendations are based. provided an excellent and concise review of the subject. However, a recent case has led me to question two statements made in support of the current guidelines. A 3.8-kg male baby, aged 5 days, underwent an exploratory laparotomy and removal of a left suprarenal ttimoiir. Histology subsequently showed it to be a mesoblastic nephrorna. Approximately 20 min after removal of the tumour, the baby suddenly became profoundly bradycardic and hypotensive (arterial saturation remaining normal) and then rapidly suffered an asystolic cardiac arrest. Multiple doses of epinephrine, volume replacement (colloid and blood), sodium bicarbonate and calcium chloride were given (according to currently accepted ILCOR and Resuscitation Council (UK)
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Editor,-I am delighted that Dr Hack has reported this unusual event where a 3.8-kg baby survived multiple doses of epinephrine and ventricular fibrillation without severe neurological damage. At the beginning of my article’ and in the ILCOR statement’ it is explained that both are based on specific evidence where available, or supported on the basis of common sense or ease of teaching and skill retention. The paediatric ILCOR statement includes recommendations reached by consensus of an expert multinational panel. The specific published evidence was declared in the reference list. Dr Hack, by presenting this letter for
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J. Ptitzner
guidelines). After four doses of epinephrine, ventricular fibrillation developed which proved very resistant to treatment. Eventually, after the sixth attempt at defibrillation and following a fifth dose of epinephrine, a slow, broad complex rhythm associated with a spontaneous cardiac output returned. Atropine 20 k g kg-’ produced rapid and sustained improvement in both heart rate and cardiac output. The baby made an excellent recovery and was subsequently discharged home with no signs of neurological impairment. In his review, Dr Zideman stated that ‘no children have survived to discharge who have received more than two doses of epinephrine’. The references used to support this statement studied the results after ‘out of hospital’ arrests where long ‘down times‘ and relatively inadequate resuscitation could be confidently expected.2 Dr Zideman also stated that in the ILCOR guidelines, atropine i s ‘not indicated during resuscitation as the adrenergic effects of epinephrine are considered to over-ride the parasympathetic (vagal) effects of atropine’. The exact cause of this infant’s cardiac arrest i s not known but was probably secondary to relative hypovolaemia with pre-existing impaired ventricular function. Before operation, this baby had been hypertensive requiring treatment with CI and p blockers. Residual adrenergic block may have played a role in the aetiology of the cardiac arrest, in addition to the requirements for high doses of epinephrine. The effective response to atropine with such high circulating concentrations of catecholamines is also surprising. Perhaps residual p block was a contributory factor? The prompt recognition and treatment of this asystolic arrest was undoubtedly responsible for the eventual successful outcome. Clearly, such a short period between onset and effective treatment is highly unusual, especially in an ‘out of hospital’ situation and only adds strength to the emphasis placed on the early recognition and treatment of the critically ill child, as taught in resuscitation courses (e.g. Paediatric Advanced Life Support and Advanced Paediatric Life Support). The guidelines recommended by the ILCOR and Resuscitation Council (UK) should be used but not rigidly adhered to without consideration of each individual case. Indeed, within the current guidelines, flexibility in therapy is ‘allowed’ when you ‘consider and correct reversible causes’. Of course, this also requires flexibility of thought on the part of those leading the resuscitation. The potentially huge disparity in outcome between individual resuscitation cases depending on their aetiology and location. as illustrated by the case report here, must surely encourage a more cautionary approach to the use of such sweeping statements when associated with such widely read and important guidelines.
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I Zideman. D A . Resuscitation. B r j Anoesth 1999; 83: 157-68 2 Nadkarni V. Hazinski MF, Zideman DA, et 01. Paediatric life support: an advisory statement by the Paediatric Life Support Working Group of the International Liaison Committee on Resuscitation. Resuscitation 1997; 34: I 15-27 3 Zaritsky A. Nadkarni V. Hazinski MF. et 01. and the Paediatric Utstein Consensus Panel. Recommended guidelines for uniform reporting o f paediatric advanced life support: the paediatric Utstein style. Resuscitotion 1995; 30: 95-1 I 6
that this is a typing error and that the author means to suggest that edrophonium has a higher ED50 in children than in adults.‘ For this reason, the author suggests the use of higher doses of edrophonium for antagonism in infants and children. These studies, however, were carried out under steady-state infusion of tubocurarine and not during the recovery phase from the newer non-depolarizing agents. Moreover, there was no significant difference in the dose of edrophonium required to antagonize tubocurarine-induced neuromuscular block in children and adults.6 In contrast, several studies have shown that neostigrnine antagonizes residual non-depolarizing neuromuscular block more effectively in children than in adults.’-’ Debaene, Meistelman and d’Hollander’ showed that, when twitch height recovered to 10% of control after vecuronium, neostigmine 30 ~g kg-’ had a more rapid onset in children than in adults, and that a TOF of 0.7 was obtained in less than 10 min in all patients, including infants. The dose of neostigmine to effectively antagonize 90% block produced by rocuronium is indeed smaller in children (mean 7 pg kg-’) than in adults (56 pg kg-1).8 The effects of 2 X EDg5of rocuronium could effectively be antagonized in infants with neostigmine 20 pg kg-1.9 With inivacurium there may be an argument for the use of edrophonium as it slows the hydrolysis of mivacurium by plasma cholinesterase less than neostigmine. However, until this issue is resolved, we agree with the author’s recommendation of not antagonizing profound mivacuriun-induced block. In summary, we feel that there are little convincing scientific data to prefer edrophoniuin to neostigmine in paediatric patients. Indeed, with the new shorter acting neuromuscular blocking agents, there may be some advantage to the use of neostigmine over edrophonium. J. J. Driessen E. N. Robertson L. H. D. J. Booij Depcirtrnent (fAnnesthesiology Acadernic Hospifal Nijrizrgeri Nijinegerr. The Nrthrrlnritls
Which is better in children: edrophonium or neostigmine? Editor,-We read with interest the review article by Fisher’ on neurornuscular blocking agents in poediatric anaesthesia. It was a concisc summary of the use of these agents in pediatric practice today. The author’s preference for edrophonium over neostigmine, however. did not seem to be a true reflection of what is known about antagonism of neuromuscular block in children. There have been few comparative studies in children of the speed of action of edrophonium and neostigmine. In comparable mg per kg doses, recovery from an intense atracurium-induced neuroinuscular block in children is faster after neostigmine than edrophonium.’ In adults. it has been shown that in the reversal of profound block produced by vecuronium or atracurium, neostigmine is more effective than edrophonium and its maximal effect is reached more quickly. even though edrophonium is faster in its initial onset.? Monitoring of the depth of neuromuscular bloch in infants and children is technically more difficult and not perhaps ax widespread as in Dr Fisher’s department. This suggests that the chance of profound neuromuscular block at the end of surgery is greater in pediatric anaesthetic practice. Neostigmine would therefore be a better choice than edrophonium. In his article. Fisher stated that less neostigmine is needed in children than in adults, and quoted Fisher and colleagues.’ Quoting the same article.’ he then stated that the EDSO of neostigmine for antagonism was greater for children than for adults. It is possible
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Fisher D M . Neuromuscular blocking agents in paediatric anaesthesia. B r J Anoesth 1999; 83: 58-64 Gwinnutt CL, Walker RWM. Meakin G. Antagonism of intense atracurium-induced neuromuscular block in children. Br J Anoesth 1991; 67: 13-6 Caldwell JE, Robertson EN, Baird WLM. Antagonism of profound neuromuscular blockade induced by vecuronium o r atracurium. Comparison o f neostigmine with edrophonium. B r j Anoesth 1986; 58: 1285-9 Caldwell JE. Robertson EN, Baird WLM. Antagonism o f vecuronium and atracurium: comparison of neostigmine and edrophonium administered at 5% twitch height recovery. Br j Anoesth 1987; 59: 478-8 I Fisher DM, Cronelly R. Miller RD, Sharma M. The neuromuscular pharmacology o f neostigmine in infants and children. Anesthesiology 1983;59: 220-5 Fisher DM. Cronelly R, Sharma M, Miller RD. Clinical pharmacology of edrophonium in infants and children. Anesthesiology I 9 8 4 6 I : 428-33 Debaene 6,Meistelman C, d’Hollander A. Recovery from vecuronium neuromuscular blockade following neostigmine administration in infants, children and adults during halothane anaesthesia. Anesthesiology 1989; 71: 840-4 Abdulatif M, Mowafi H, Al-Ghamdi A, El-Sanabary M. Dose-response relationships for neostigmine antagonism of rocuronium-induced neuromuscular block in children and adults. Br J Anoesth 1996; 77: 710-15 Leuwer M, Motsch J, Schledt U. et ol. Dose-response, time course o f
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publication. has therefore added to the data source and the results that he has reported would be considered, together with those reported via published pediatric Utstein template3 reports, at the next review. The paediatric resuscitation guidelines should not be considered as rigid protocols. I note that in his report, Dr Hack adhered to the recommended guidelines initially. In some events. especially whcn the cau5e is treatable and there is little or no monitored hypoxia. it is appropriate to continue resuscitation and to use any reasonable resource or treatment available. I n this case, multiple administrations of epinephrine (dose not reported) were successful in restoring a spontaneous circulation. The use of atropine in the treatment of the resulting peri-arrest bradycardia was appropriate, despite the anomaly of the previous multiple doses of epinephrine. Finally, may 1 suggest that the success of this event was a result of sustained maintenance of tissue oxygenation. It cannot be emphasized sufficiently that sustained delivery of oxygen to this infant‘s tissues was critical to the successful outcome. I would hope that the publication of this letter will encourage others to report their pediatric resuscitation events, either as individual case reports or using the Utstein template,’ so that we can continue to improve the practice of paediatric life support.
Correspondence
neuromuscular block in children and adults. Br J Anoesth 1996; 77: 710-15 Leuwer M, Motsch J, Schledt U, et 01. Dose-response, time course o f action and recovery o f Ong 9426 (rocuronium) in infants during halothane anaesthesia. Br J Anoesth 1994; 73: 7 16P Fisher DM, Cronnelly R. Miller RD, Sharma M. Neuromuscular pharmacology of neostigmine in infants and children. Anesthesiology 1983;59: 220-5 Cronnelly R. Morris RB. Miller RD. Edrophonium: Duration of action and atropine requirement in humans during halothane anesthesia. Anesthesiology 1982; 57: 26 1-6 Miller RD, VanNyhuis LS, Eger El 11, et 01. Comparative times t o peak effect and durations o f action o f neostigmine and pyridostigmine. Anesthesiology I 9 7 4 4 I: 27-33
action and recovery o f O R G 9426 (rocuronium) in infants during halothane anaesthesia. Br J Anoesth 1994; 73: 7 l6P
Bacterial contamination of needles used for spinal and epidural anaesthesia Editor.-We read with interest the article by Raedler and colleagues regarding contamination of needles used during central neural block.' It is cause for concern that almost 18% of the needles showed evidence of bacterial contamination, even though no patient developed infective complications. There are points we would like to make with regard to the aseptic technique which may explain the high incidence of bacterial colonization. First. it is not clear if the 10% polyvidone-iodine (PI) used for skin preparation came from single or multiple-use containers. There is evidence to show that multiple-use PI bottles in normal use may become contaminated by bacteria and also that the solution is less effective than PI from previously unopened bottles.2 Also. alcohol chlorhexidine is a commonly used alternative to PI for skin disinfection and has been shown to reduce the rate of central venous catheter colonization and catheter-related sepsis compared with PI.3 There are no studies comparing the two solutions for skin disinfection before central neural block, but we would suggest that it should be used in preference to PI. Second, the authors refer to the use of sterile gloves and drapes, but no mention is made as to whether face masks were worn. While we accept that the use of face masks has not been shown to decrease the incidence of postoperative surgical wound i~ifection.~ there is evidence to suggest that they decrease bacterial dispersion' and that their use can reduce the incidence of catheterrelated infections during insertion.' We suggest that the use of alcohol chlorhexidine instead of 10% PI and wearing of face masks for central neural block may reduce the incidence of bacterial contamination of spinal and epidural needles.
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J. Whiteside J . A. W. Wildsmith Uriiwr-s;ry Drpnrrriirrit c?f'Aiitrestlirsirr Dirritlec., U K
Gwinnutt CL, Walker RW. Meakin G. Antagonism of intense atracurium-induced neuromuscular block in children. Br J Anoesth 1991; 67: 13-16 Fisher DM. Cronnelly R. Sharma M. Miller RD. Clinical pharmacology of edrophonium in infants and children. Anesthesiology 1984; 6 I:428-33 Debaene B, Meistelman C, d'tiollander A. Recovery from vecuronium neuromuscular blockade following neostigmine administration in infants, children, and adults during halothane anesthesia. Anesthesiology 1989; 71: 8 4 0 4 Abdulatif M. Mowafi ti, al-Ghamdi A, el-Sanabary M. Dose-response relationships for neostigmine antagonism of rocuronium-induced
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Raedler C. Lass Florl C, Puhringer F, et 01. Bacterial contamination of needles used for spinal and epidural anaesthesia. Br J Anoesth 1999; 83: 657-8 Birnbach D, Stein D. Murray 0. Thys D. Sordillo E. Povidone iodine and skin disinfection before initiation of epidural anesthesia. Anesthesiology 1998; 88: 668-72 Mimoz 0, Pieroni L, Lawrence, C. et 01. Prospective, randomized trial o f two antiseptic solutions for prevention of central venous or arterial catheter colonization and infection in intensive care unit patients. Crit Core Med 1996; 24: I 8 18-23 Legras A, Cattier B, Dequin P, Boulain T, Perrotin D. Prospective randomised trial for prevention of vascular catheter infection: Alcohol
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Editor.-Driessen. Robertson and Booij challenge my preference for edrophoniurn over neostigmine. The first issue that they explore is profound block. My review acknowledges that neostigmine i s prel'erred in that setting. Even if they are correct that 'monitoring o f infants i\ tcchnically more difficult', I hope that neuromuscular block is monitored routinely in infants. I also expect that clinicians are able to dihnguish between profound twitch depression at the time of antagonism' (no response to train-of-four stimulation) from the more typical level of recovery (presence of more than one twitch i n response t o train-of-four stimulation). Under these usual conditions. is there evidence to refute my claim that cdrophonitnii works faster'? Driessen. Robertson and Booij detected a typographical error that I mish to correct. The EDSO for edrophonium (not for neostiginine) is larger i n children (233 pg kg-') than in adults ( 1 1 8 pg kg-'). Although the difference was not significant. the larger value and larger variability in children than in adults led to our recommendation 'that paediatric patients receive larger doses of edrophonium (e.g.. I .0 mg kg-I)' than adults. Drieswi. Robertson and Booij then claimed that three studies dcinonstrated that 'neostigmine antagonizes residual nondepolariing neuromumilar block more effectively in children than in adults'. Unfortunately, they mis-state the conclusions of those studics. Debaene. Meistelman and d'Holland3 found no difference between infants. children and adults for recovery of twitch at any time or in the train-of-four response before 10 min. They attribute the improved late train-of-four recovery in children to 'the faster rate o f spontaneous recovery from vecuronium', rathcr than a n effect of the antagonist. The results of Abdulatif and colleagues4 also can be explained by the more rapid spontaneous recobery in children than in adults (as evidenced by their control groups). Lcuuer and colleagues' abstract5 reported that recovery, improved the neostigmine 10 pg kg-', given at 3% time to train-of-four >0.7 in infants (no adults were studied) compared \\ i t h ;I group given no antagonist; however, variability i n recovery rate was quite large (SD exceeded the mean) and no other neostigmine doses were evaluated. Driessen. Robertson and Booij concluded that 'there is little convincing scientific data to prefer edrophonium to neostigmine i n pediatric patients' and suggest that 'with the new shorter acting neuromuscular blocking agents there may be some advantage to the use of neostigmine over edrophonium'. In contrast. studies in children' (' and adults' demonstrate that edrophonium antagonizes 90% block faster t h m neostigmine. Hence, whenever block is not intense and recovery time is important (as is increasingly true in clinical anaesthesia). 1 prefer edrophoniurn i n children.
Correspondence chlorhexidine versus povidone-iodine. Reanimation Urgences 1997; 6: 5-1 I 5 Tunevall T. Postoperative wound infections and surgical face masks: a controlled study. World] Surg I 9 9 I : 15: 383-7 6 Philips J. Fergusson S. Armstrong P. Anderson F. Wildsmith J. Surgical face masks are effective in reducing bacterial contamination caused by dispersal from the upper airway. Br] Anoesth 1992; 69: 407-8 7 Raad I, Hohn D, Gilbreath B. et 01. Prevention of central venous catheter-related infections by using maximal sterile barrier precautions during insertion. Infect Control Hosp Epidemiol 1994; 15: 23 1-8
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Editor.-Our aim was to study our practice of administering spinal or epidural anaesthesig; our technique was guided by generally recognized rules. We used aqueous povidone-iodine (PI). Face masks were not used in all cases, but there was no correlation between the use of face masks and needle contamination in our study. We are aware of the study published by Birnbach and colleagues' who found 40% of multiple-use PI bottles to be microbiologically contaminated compared with 5% contamination rate in bottles used for the first time. Hence they suggest singleuse bottles for skin disinfection. Small bottles of PI for single use are not available in our country. Moreover, Birnbach and colleagues stated that none of the organisms isolated from the sponge sticks used for skin disinfection was present in the PI solution, except in one case. Thus contamination is more a problem of normal skin colonization than of contaminated disinfection solutions. We found our multiple-use PI solutions to be free of bacterial growth. However, Birnbach and colleagues speculated that reduced antimicrobial activity of PI solutions from multiple-use bottles might have been the reason for their findings. Another point raised was that alcoholic PI might be superior to aqueous solutions. We found our antimicrobial solutions eradicated bacteria after weeks of use. But our results demonstrated that standards and guidelines must be subject to continuous evaluation. Despite using an aseptic technique, lumbar puncture may contaminate spinal or epidural needles. In line with Birnbach and co-workers. we conclude that indigenous bacterial skin flora is most likely the source of this contamination. Alcoholic solutions may be more effective in this respect.
E. ChojnowAn F l - < ~ l i < ~Ho.\/l;ld /i~l~
Bii\tO/. I'K
I Raedler C. Lass-Florl C. Puhringer F. Kolbitsch Ch, Lingnau W. Benzer
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I Birnbach DJ, Stein DJ, Murray 0, Thys DM, Sordillo EM. Povidone iodine and skin disinfection before initiation of epidural anesthesia. Anesthesiology 1998; 88: 668-72
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Editor.-Raedler and colleagues' described an incidence of 17.9% bacterial contamination of spinal and epidural needles after lumbar puncture of the subarachnoid or epidural space. The authors make (tic important point that despite using an aseptic technique. lumbar puncture may contaminate spinal and epidural needles. Their aseptic technique included skin disinfection with 10% polyvidoneiodine (Braunol 2000). Povidone-iodine is a complex of iodine. the bactericidal component, with polyvinylpyrrolidone (povidone) a synthetic polymer. The common commercial form in the UK is a 10% solution in water (Betadine). h i v i t w studies showed that aqueous povidone-iodine (PI) preparations were superior to alcohol or chlorhexidine preparations when tested for activity against bacteria with increasing dilution.' However. addition of 80% ethanol to 0 5 % chlorhexidine significantly increased its potency and onset of action compared with 10%PI.' The advantages of using alcohol rather than aqueous based solutions are further demonstrated by itz 1,ii.ostudies. Sato. Sakuragi and Dan' excised skin specimens from 60 patients undergoing elective back operations after preparation with either aqueous 10% PI or 0.5% chlorhexidine in 80% ethanol. and cultured staphylococcal species in 32.470 I'S 5.7%. respectively. A further problem. raised by Birnbach and colleagues.' concerns the frequency of bacterial contamination of previously opened multiple-use bottles of aqueous 10% PI. Bacteria were found only in previously opened bottles of which 40% were contaminated. Hence the study recommends single-use containers. PI in an alcoholic solution overcomes the disadvantages of aqueous solution. A comparison of the efficacy of 10% PI ethanol solution and 0.5% chlorhexidine ethanol solution' showed no significant difference in decreasing skin bacterial counts (bacterial reduction rate 95% 1's 93.5%). Complete eradication of indigenous bacteria is impossible using thc currently available skin disinfecting methods. However, to reduce the risk of infectious complications of epidural anaesthesia, attention should focus on any means of prevention, including optimal skin disinfection. Raedler and colleagues do not state if their PI solution was aqueous based or came from previously opened multi-use bottles. They recommend further improvement of hygienic measures but do not include optimization of skin disinfection with an alcoholic solution of 10% PI or 0.5% chlorhexidine.
A. Bacterial contamination of needles used for spinal and epidural anaesthesia. Br J Anoesth 1999; 83: 657-8 Michel D. Zach GA. Antiseptic efficacy of disinfecting solutions in suspension test in vitro against methicillin-resistant Staphylococcus aureus. Pseudomonas aeruginosa and Escherichia coli in pressure sore wounds after spinal cord injury. Dermatology 1997; 195 (Suppl. 2): 36-4 I McLure AR, Gordon J. In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus. J Hosp Infect 1992; 21: 291-9 Sakuragi T, Yanagisawa K. Dan K. Bactericidal activity o f skin disinfectants on methicillin-resistant Staphylococcus aureus. Anesth Analg 1995; 8 I: 555-8 Sat0 S, Sakuragi T. Dan K. Human skin flora as a potential source o f epidural abscess. Anesthesiology 1996; 85: 1276-82 Birnbach DJ, Stein DJ, Murray 0, Thys DM. Sordillo EM. Povidone iodine and skin disinfection before initiation o f epidural anesthesia. Anesthesiology 1998; 88: 668-72 Arata T. Kamitani M, Miyai T, I t 0 M. Antiseptic effects at injection sites. Dermatology 1997; I 9 5 (Suppl. 2): 107-10