- Email: [email protected]
Cruel to be kind? Regional block before or after induction of general anaesthesia
Current Anaesthesia & Critical Care (2003) 13, 287^292
c 2003 Elsevier Science Ltd. All rights reserved. doi:10.1054/cacc.2002.0423
CONTROVERSIES
Cruel to be kind? Regional block before or after induction of general anaesthesia P. D.W. Fettes and J. A.W. Wildsmith University Department of Anaesthesia, Ninewells Hospital and Medical School, Dundee DD19SY, UK
KEYWORDS anaesthesia, general; anaesthesia, local; safety; paresthesia; complications, neurologic; anaesthesia, epidural
Summary The question of whether to insert regional blocks before or after induction of general anaesthesia is controversial, but the debate based more on opinion than fact. The arguments for insertion after induction are: K K K K
There is no evidence that it is any more dangerous. It leads to greater patient acceptance and comfort. It provides better conditions for training. The practice is medicolegally acceptable.
The arguments for insertion before induction are: K
K K
Anaesthetized patients cannot report pain or paraesthesia when the block is performed, or adverse symptoms to test doses of local anaesthetic. Why not perform the block ¢rst since this is standard practice in many centres? Who will monitor the patient when the block is performed?
There is no large randomized controlled trial comparing the safety of blocks before and after induction of general anaesthesia, and it is unlikely thatthere ever will be. However, a signi¢cant link between pain or paraesthesia experienced on needle insertion, and subsequent nerve damage has been observed. Also studies using nerve stimulators during peripheralnerve block have shownthat paraesthesiae may be experienced without motor response. Both of these ¢ndings suggest that nerve block may be safer in awake patients. Although there is no direct evidence that performing blocks on anaesthetized patients is less safe, there is some indirect evidence to suggest it might be. If a block is to be performed on an anaesthetized patientthere must be a good positive reason for this.
c 2003 Elsevier Science Ltd. All rights reserved.
INTRODUCTION The popularity of regional anaesthesia is probably at an all time high, there having been a substantial and international increase in the use of regional blocks over the past 30 years. But popularity in medicine, as in politics, tends to wax and wane, and concerns about safety could reverse this trend. Large surveys have shown that regional anaesthesia is safe, and that serious complications are rare. However, the complications are permanent and distressing. Predictably, the increased utilisztion of regional Correspondence to: PDWF.Tel.: +44 01382 632427; Fax: 01382 644914; E-mail: [email protected] 0953-7112/03/$-see front matter
anaesthetic techniques has been accompanied by an increase in the absolute number of cases in which complications have been identi¢ed. There has also been an increase in the number of claims against anaesthetists by patients who have received regional anaesthesia,1,2 although there is no evidence that the actual incidence of complications or claims has risen. It is ironic that, in the age of evidence-based medicine, it is a small number of high pro¢le cases, rather than the combined weight of large studies, that is more likely to cause regional anaesthesia to fall from grace. Therefore every factor, which could compromise patient safety, must be considered and reconsidered.
288
In1996, a new factor was identi¢ed by a World authority on regional anaesthesia, Philip Bromage, who presented his views in an editorial entitled ‘Masked mischief’.3 In the article, Bromage described situations where complications could be masked by anaesthesia, or nerve block. One example was the insertion of thoracic epidural catheters under general anaesthesia that was, he said, ‘‘the most £orid form of masked mischief’’. He stated that patients are ‘‘rendered incapable of vocal or re£ex muscular responses to spinal cord impalement and insu¥ation with air.’’ Bromage’s article has triggered much debate over the past few years, mainly based on opinion rather than evidence, but the issue still requires attention.
THE ARGUMENTS .... .... for insertion after induction Most discussion has hinged on whether performing blocks on anaesthetized patients increases the likelihood of neurological sequelae. Protagonists of this approach argue that there is no evidence that it is any more dangerous to do so,4,5 that it leads to greater patient acceptance and comfort, and that it provides better conditions for training.5 Paradoxically it has also been stressed that only skilled anaesthetists should perform central blocks,5,6 and few would argue with Fischer’s assertion that ‘‘the major factors in preventing neurological sequelae are the experience and dexterity of the anaesthetist, proper training and supervision of trainees, detailed assessment of pre-existing vascular and neurological disease, avoidance of repeated attempts due to technical di⁄culties, and prompt recognition and treatment of complications to prevent permanent damage’’.5 Fischer has also pointed out that two major medical defence organizations in the United Kingdom do not view the administration of a general anaesthetic before a regional anaesthetic as inherently bad practice.5 Although medicolegal opinion is important, there is a di¡erence between optimum management, and what might be considered legally defensible, although the gap may be narrowing. .... for insertion before induction Bromage has highlighted that anaesthetized patients cannot give a verbal warning of symptoms of, or produce re£ex muscular responses to, pain or paraesthesia. The latter assertion is at odds with that of Fischer who believes that re£ex muscle movement will still occur. A further concern is that patients will also be unable to report any adverse symptoms to test doses of local anaesthetic for epidural, or indeed any other type of local or regional block. Adverse e¡ects may be systemic (e.g. as a result of intravascular injection) or local (e.g. unintentional subarachnoid injection during epidural block), although the consequences may still be systemic.
CURRENT ANAESTHESIA & CRITICAL CARE Bromage and others7,8 have questioned the need to perform blocks on anaesthetized patients given that it is standard practice in most centres noted for regional anaesthesia to do them ¢rst.This seems perfectly acceptable to patients if a careful technique is used, and as Bromage asks: ‘‘why risk the added risk?’’9 A key point is the question of who monitors the general anaesthetic while the block is performed, the clear inference being that patient safety may be compromised by the ‘distraction’ of the block.7 While Fischer has argued that there is no good evidence that performing blocks under general anaesthesia increases the risk, he acknowledges that the onus for proving the safety of this approach is on its proponents.
THE EVIDENCE BASE So, experts in regional anaesthesia are divided in their opinions on the subject of when to perform the block. But what evidence base is there to help the practitioner decide what to do?
Studies and surveys There is no large randomized controlled trial comparing the safety of blocks before and after induction of general anaesthesia, and it is unlikely that there ever will be. In fact, there are few large surveys examining complications of regional anaesthesia, and none which looks speci¢cally at di¡erences in incidence when the blocks are performed awake or asleep. What the available studies do show is that regional anaesthesia is safe, and that serious complications are very rare. Auroy and colleagues10 looked prospectively at over 100 000 regional anaesthetics and found the incidence of permanent neurological de¢cit to be 0.5 in10 000 and the incidence of death to be 0.9 in 10,000 (other studies have found similar incidences11,12). This suggests that any potential di¡erence in complication rates between blocks performed awake or asleep is likely to be small, and di⁄cult to demonstrate. Therefore, it seems unlikely that large surveys will ever provide a straight answer on whether there is a di¡erence in safety between the two approaches. Thus, other less direct evidence must be sought to guide practice. What Auroy and colleagues did ¢nd is that there is a signi¢cant link between pain or paraesthesia experienced on needle insertion, and subsequent nerve damage. Out of a total of 34 neurological complications recorded in their study, 21 were associated with paraesthesia on needle insertion, or pain on injection. Most of the rest involved the intrathecal injection of 5% lidocaine suggesting a direct neurotoxic e¡ect, and a di¡erent mechanism of action. Pain or paraesthesia on needle insertion have also been found to be risk factors in other large studies, albeit retrospective in nature,1,11,13 and the
CRUELTO BEKIND?
implication of this needs to be considered. Would performing the block awake be safer if the needle is withdrawn immediately on sensation of pain or paraesthesia, or will the damage have been done already? It does make sense that any damage will at least be limited if the patient is awake, the needle advanced gently, and any discomfort taken immediately as a sign of problems.
289
although the patients were awake. So was patient feedback useless in preventing damage? This series has been used to negate the argument that performing blocks in awake patients is safer,17 but did the clinicians simply ignore the warnings?
Inferential evidence Case reviews and reports What value does the presentation of reports on individual patients have to modern day medicine? The answer is ‘considerable’ in situations like this where complications are rare and may not be picked up even in largescale studies. The ‘yellow card’ system for reporting adverse drug reactions is a good example of this, and the chair and deputy chair of the Cochrane Collaborative Steering Group have recognized the limitation of even large-scale trials which unless ‘placed in the context of other relevant research, exist as islands of information’. They have also recognized that ‘one challenge facing reviewers today is how to identify and incorporate data on rare adverse events not usually available from randomised trials’.14 Unfortunately, because they tend to be carried out by enthusiasts, voluntary surveys rarely identify problems, but occasional case reviews and reports, anecdotal though they are, may provide important information. When they are publicized widely, individual cases carry enormous power, as can be seen from the history of spinal anaesthesia. A case series reported by a British trained, New York based neurologist, coincided with two high pro¢le cases in the UK, and led to the virtual demise of spinal anaesthesia in the middle of the 20th century.15 More recently, in1994, a report of two patients su¡ering major neurological injury after thoracic epidural block was published in Germany, and led to the setting up there of what amount to national guidelines.8 These state that general anaesthesia is an absolute contra-indication to thoracic epidural placement, and a relative contra-indication to all other central blocks. The guidelines also go so far as to suggest that ‘for instance a cholecystectomy or a hemicolectomy in an otherwise healthy patient is not considered to be a reasonable indication for a thoracic epidural.’ In 2001, Reynolds16 published a series of seven patients su¡ering from spinal cord damage after spinal or combined spinal/epidural (CSE) anaesthesia. In all seven patients, there was pain on insertion of the spinal needle and the neurological de¢cit emerged as the block regressed, and six of the seven had magnetic resonance imaging (MRI) evidence of a lesion in the spinal cord at a level consistent with the clinical features.Only one of the patients had pain on injection of local anaesthetic, but all had permanent de¢cit.The damage had already occurred
Two recent publications add weight to the argument that peripheral nerve block is safer if performed awake. First Choyce and colleagues,18 and then Urmey and Stanton19 have demonstrated that a motor response cannot always be elicited with a nerve stimulator after the patient has reported paraesthesiae. In both studies paraesthesiae were elicited during brachial plexus block and then the nerve stimulator was turned on. A twitch response did not occur at o0.5 mA in all patients in either study, although there were important di¡erences between the two. Urmey and Stanton enlisted 30 patients undergoing interscalene block for shoulder surgery. After paraesthesiae were obtained, a twitch was observed in only 30% of patients when the current was increased to1mA, there being no relationship between the distribution of paraesthesiae and the subsequent motor response although 20 out of the 30 needles used were un-insulated. No patient required conversion to general anaesthesia, and the surgeon’s assessment of the block was at least ‘satisfactory’ or better. Choyce and colleagues enrolled 72 patients having axillary brachial plexus block with un-insulated needles for upper limb surgery, but 19 of these were excluded, mostly because of arterial puncture. In 77% of the remainder a motor response was obtained (at o0.5 mA) after paraesthesiae. Median current was 0.17 mA, but the range was 0.03^3.3 mA, and a relationship between distribution of paraesthesiae and motor response was found in 81% of patients. Interestingly,13% of blocks required supplementary local anaesthetic, and 9% of patients required conversion to general anaesthesia. The two studies show big di¡erences in both block reliability, and the relationship between paraesthesiae and motor response. These di¡erences are important and may be explained only partly by di¡erences in block site and the needles used. However, the important message is that paraesthesiae may be experienced without motor response, and both papers concluded that nerve block would be safer in lightly sedated or awake patients.
SPECIAL PROBLEMS AND GREY AREAS There are a number of special situations where the balance of risk and bene¢t becomes altered to some degree, and these deserve special consideration.
290
Paediatric anaesthesia No discussion about the timing of regional block would be complete without consideration of paediatric practice, where blocks are now performed almost universally after induction of general anaesthesia. This is because of the particular problems of communication and compliance in children that virtually dictate that general anaesthesia must be used.This view was challenged in1998 by a report detailing the case of a 62-year-old woman, with a history of previous back surgery, who su¡ered permanent paraplegia after multiple attempts to site an epidural catheter under general anaesthesia.20 Several criticisms were made of the patient’s management, which was complicated by poor treatment of periods of intra and postoperative hypotension, and magnetic resonance imaging (MRI) showed both spinal cord infarction at T5, and gas bubbles in the spinal cord at T10 and T12. However, the authors condemned particularly the administration of a thoracic epidural in an anaesthetized patient, stating that this should only be attempted as a life-saving measure in exceptional circumstances. Subsequently, this conclusion was refuted vehemently by a large number of paediatric anaesthetists who stated that performing regional anaesthesia on anaesthetized children is a safe technique.21,22 Of the several articles cited to support their stance, one is particularly worthy of mention. A prospective French survey23 was carried out over the course of 1 year. Data from over 85 000 anaesthetics (a 51% response rate) included 24 409 with a regional component (89% under GA). Over 60% of these were central (mainly caudal) and 38% were peripheral.The results were interesting. No peripheral complications were recorded at all.The central complication rate was1.5 per 1000, although most complications were relatively minor, and none were permanent in nature. The conclusion of this impressive study was that regional anaesthesia is safe, but that peripheral blocks are safer than central ones.
Other di⁄culties with patient compliance In paediatric anaesthesia the balance of risk and bene¢t in regional block is altered because children are generally unable fully to comprehend and comply with treatment. It is possible to imagine situations in the adult population where similar conditions might prevail, and one such case has been described by Absalom and colleagues.24 Insertion of a thoracic epidural catheter was attempted prior to induction of anaesthesia for emergency abdominal surgery in an anxious Asian woman with poor English. The patient was lightly sedated, and unrestrained. During local anaesthetic in¢ltration with a 4 cm needle, the patient rolled suddenly onto her back, causing the needle to advance to its hub, and leaving the patient
CURRENT ANAESTHESIA & CRITICAL CARE
with a spinal cord injury. Although the problem might have been avoided if a needle of more appropriate length had been used for in¢ltration, the authors suggest that performing the block asleep would have probably been safer in this instance. They maintain the view, however, that regional blocks are generally safer if performed awake.
The patient in pain Patients may present for surgery, particularly emergency surgery, in severe pain and this will often make the prospect of performing regional anaesthesia prior to induction less than appealing. Positioning the patient for all but the simplest blocks may be impossible, and the twitching with a nerve stimulator may add to their distress. In addition, caution must be exercised because the patient may be hypovolaemic, or have some other relative contra-indication to central block. Nevertheless, certain patients undergoing emergency abdominal surgery may bene¢t from a thoracic epidural once the procedure is over. Does the additional bene¢t of establishing analgesia ¢rst justify inserting the epidural before the patient regains consciousness? Certainly, the consequence of spinal cord damage is so severe that any additional risk needs justi¢cation, but if the risk is very small, and the bene¢t (high-quality pain relief) so tangible, is that not justi¢cation in itself? In Germany, the answer would be a resounding ‘no’. Should it be di¡erent elsewhere?
Uncertain surgery In some situations it may be di⁄cult to predict the operation that will be performed on a patient. In some centres, including our own, diagnostic laparoscopy may precede, and often obviate the need for, laparotomy. Those that do undergo laparotomy may bene¢t from thoracic epidural block, particularly in the presence of respiratory illness. What should be done in this instance? Should the patient have an epidural sited prior to induction when it may prove to be unnecessary? Should the epidural be sited under general anaesthesia if laparotomy is performed, or should it be sited once the patient is awake and in pain? Perhaps the easiest option would be to forget the epidural altogether and prescribe PCA morphine, but that would not be optimum care for every patient. Another dilemma, cited by a group of anaesthetists in Cardi¡,6 is in anaesthesia for thoracic surgery where bronchoscopy may or may not be followed by thoracotomy. They use this to justify thoracic epidural insertion under general anaesthesia, although one alternative solution is to have separate lists for bronchoscopy and
CRUELTO BEKIND?
thoracotomy, and another to use a more peripheral block technique (e.g. Paravertebral).
SO, AWAKE OR ASLEEP? The protagonists in this debate are agreed on one thing. Regional anaesthesia must be performed carefully and cautiously by practitioners who have full knowledge of the relevant anatomy, the technique being used, its complications and the ways of avoiding them.Those (the present authors included) who favour the ‘awake’ approach note that the protagonists of the‘asleep’ approach accept that they have to prove that it is a safe one. They also have to be able to answer several questions: 1. Why do the block with the patient asleep? 2. Why not do the block with the patient awake? 3. Is there an alternative to an invasive procedure on an unconscious patient? 4. Who will monitor the patient while the block is being performed? The answer to the‘awake or asleep’question relates to the balance of risk and bene¢t, so proscriptive national guidelines such as those in place in Germany, although well intentioned, are probably unnecessary because they remove the clinician’s ability to tailor the anaesthetic to the patient. Anaesthetists would be well advised to perform all blocks in awake or lightly sedated patients if at all possible, but there must be a place for the alternative.This principle is of particular importance for central blocks where the potential for damage is greatest, but it also applies to peripheral nerve block. In instances where more than one block is used the more peripheral block should be inserted ¢rst where possible. Finally, an interesting observation with which to close. A recent survey of anaesthetists in the Oxford region has shown a di¡erence between beliefs and working practices.25 While most anaesthetists believed that blocks were safer performed awake, the majority still performed most of their blocks on anaesthetized patients. Instead of being cruel to be kind, is this a case of being kind to be cruel? It is time to question this anomaly, and practise what we believe to ensure the safety of our patients.
REFERENCES 1. Cheney F W, Domino K B, Caplan R A, Posner K L. Nerve injury associated with anesthesia: a closed claims analysis. Anesthesiology 1999; 90(4): 1062–1069. 2. Aitkenhead A R. The pattern of litigation against anaesthetists. Br J Anaesth 1994; 73(1): 10–21. 3. Bromage P R. Masked mischief. Reg Anesth 1996; 21(6 Suppl): 62–63.
291
4. Gough J D, Williams A B, Vaughan R S, Khalil J F, Butchart E G. The control of post-thoracotomy pain. A comparative evaluation of thoracic epidural fentanyl infusions and cryo-analgesia. Anaesthesia 1988; 43(9): 780–783. 5. Fischer H B. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1998; 53(8): 727–729. 6. Vaughan R S, Gough J D. The control of post-thoracotomy pain: a reply. Anaesthesia 1989; 44: 445–446. 7. Wildsmith J A. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1999; 54: 86. 8. Gruning T. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1999; 54: 86–87. 9. Bromage P R. The control of post-thoracotomy pain. Anaesthesia 1989; 44(5): 445–446. 10. Auroy Y, Narchi P, Messiah A, Litt L, Rouvier B, Samii K. Serious complications related to regional anaesthesia: results of a prospective survey in France. Anesthesiology 1997; 87(3): 479–486. 11. Aromaa U, Lahdensuu M, Cozanitis D A. Severe complications associated with epidural and spinal anaesthesias in Finland 1987–1993. A study based on patient insurance claims. Acta Anaesthesiol Scand 1997; 41(4): 445–452. 12. Horlocker T T, Wedel D J. Neurologic complications of spinal and epidural anaesthesia. Reg Anesth Pain Med 2000; 25(1): 83–98. 13. Horlocker T T, McGregor D G, Matsushige D K, Schroeder D R, Besse J A. A retrospective review of 4767 consecutive spinal anesthetics: central nervous system complications. Perioperative Outcomes Group. Anesth Analg 1997; 84(3): 578–584. 14. Clarke M, Langhorne P. Revisiting the Cochrane Collaboration. Meeting the challenge of Archie CochraneFand facing up to some new ones. BMJ 2001; 323(7317): 821. 15. Wildsmith J A, Lee J A. Neurological sequelae of spinal anaesthesia. Br J Anaesth 1989; 63(5): 505–507. 16. Reynolds F. Damage to the conus medullaris following spinal anaesthesia. Anaesthesia 2001; 56(3): 238–247. 17. Vaughan R S. Pain relief after thoracotomy. Br J Anaesth 2001; 87(5): 681–683. 18. Choyce A, Chan V W, Middleton W J, Knight P R, Peng P, McCartney C J. What is the relationship between paresthesia and nerve stimulation for axillary brachial plexus block? Reg Anesth Pain Med 2001; 26(2): 100–104. 19. Urmey W F, Stanton J. Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration. Anesthesiology 2002; 96(3): 552–554. 20. Bromage P R, Benumof J L. Paraplegia following intracord injection during attempted epidural anesthesia under general anesthesia. Reg Anesth Pain Med 1998; 23(1): 104–107. 21. Krane E J, Dalens B J, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23(5): 433–438. 22. Bosenberg A T, Ivani G. Regional anaesthesiaFchildren are different. Paediatr Anaesth 1998; 8(6): 447-450. 23. Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg 1996; 83(5): 904–912. 24. Absalom A R, Martinelli G, Scott N B. Spinal cord injury caused by direct damage by local anaesthetic infiltration needle. Br J Anaesth 2001; 87(3): 512–515. 25. Kadry M A, Rutter S V, Popat M T. Regional anaesthesia for limb surgery–before or after general anaesthesia. A survey of anaesthetists in the Oxford region. Anaesthesia 2001; 56(5): 450–453.
292
FURTHER READING Urmey W F. Regional anaesthesia is potentially dangerous in anaesthetised adult patientsFpro. http://www.esraeurope.org/abstracts/abstracts99/urmey2.htm Fischer B. Regional anaesthesia is potentially dangerous in anaesthetised patients F con. http://www.esraeurope.org/abstracts/abstracts99/fischer3.htm Urmey W F, Stanton J. Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration. Anesthesiology 2002; 96(3): 552–554.
CURRENT ANAESTHESIA & CRITICAL CARE
Choyce A, Chan V W, Middleton W J, Knight P R, Peng P, McCartney C J. What is the relationship between paresthesia and nerve stimulation for axillary brachial plexus block? Reg Anesth Pain Med 2001; 26(2): 100–104. Krane E J, Dalens B J, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23(5): 433–438.
c 2003 Elsevier Science Ltd. All rights reserved. doi:10.1054/cacc.2002.0423
CONTROVERSIES
Cruel to be kind? Regional block before or after induction of general anaesthesia P. D.W. Fettes and J. A.W. Wildsmith University Department of Anaesthesia, Ninewells Hospital and Medical School, Dundee DD19SY, UK
KEYWORDS anaesthesia, general; anaesthesia, local; safety; paresthesia; complications, neurologic; anaesthesia, epidural
Summary The question of whether to insert regional blocks before or after induction of general anaesthesia is controversial, but the debate based more on opinion than fact. The arguments for insertion after induction are: K K K K
There is no evidence that it is any more dangerous. It leads to greater patient acceptance and comfort. It provides better conditions for training. The practice is medicolegally acceptable.
The arguments for insertion before induction are: K
K K
Anaesthetized patients cannot report pain or paraesthesia when the block is performed, or adverse symptoms to test doses of local anaesthetic. Why not perform the block ¢rst since this is standard practice in many centres? Who will monitor the patient when the block is performed?
There is no large randomized controlled trial comparing the safety of blocks before and after induction of general anaesthesia, and it is unlikely thatthere ever will be. However, a signi¢cant link between pain or paraesthesia experienced on needle insertion, and subsequent nerve damage has been observed. Also studies using nerve stimulators during peripheralnerve block have shownthat paraesthesiae may be experienced without motor response. Both of these ¢ndings suggest that nerve block may be safer in awake patients. Although there is no direct evidence that performing blocks on anaesthetized patients is less safe, there is some indirect evidence to suggest it might be. If a block is to be performed on an anaesthetized patientthere must be a good positive reason for this.
c 2003 Elsevier Science Ltd. All rights reserved.
INTRODUCTION The popularity of regional anaesthesia is probably at an all time high, there having been a substantial and international increase in the use of regional blocks over the past 30 years. But popularity in medicine, as in politics, tends to wax and wane, and concerns about safety could reverse this trend. Large surveys have shown that regional anaesthesia is safe, and that serious complications are rare. However, the complications are permanent and distressing. Predictably, the increased utilisztion of regional Correspondence to: PDWF.Tel.: +44 01382 632427; Fax: 01382 644914; E-mail: [email protected] 0953-7112/03/$-see front matter
anaesthetic techniques has been accompanied by an increase in the absolute number of cases in which complications have been identi¢ed. There has also been an increase in the number of claims against anaesthetists by patients who have received regional anaesthesia,1,2 although there is no evidence that the actual incidence of complications or claims has risen. It is ironic that, in the age of evidence-based medicine, it is a small number of high pro¢le cases, rather than the combined weight of large studies, that is more likely to cause regional anaesthesia to fall from grace. Therefore every factor, which could compromise patient safety, must be considered and reconsidered.
288
In1996, a new factor was identi¢ed by a World authority on regional anaesthesia, Philip Bromage, who presented his views in an editorial entitled ‘Masked mischief’.3 In the article, Bromage described situations where complications could be masked by anaesthesia, or nerve block. One example was the insertion of thoracic epidural catheters under general anaesthesia that was, he said, ‘‘the most £orid form of masked mischief’’. He stated that patients are ‘‘rendered incapable of vocal or re£ex muscular responses to spinal cord impalement and insu¥ation with air.’’ Bromage’s article has triggered much debate over the past few years, mainly based on opinion rather than evidence, but the issue still requires attention.
THE ARGUMENTS .... .... for insertion after induction Most discussion has hinged on whether performing blocks on anaesthetized patients increases the likelihood of neurological sequelae. Protagonists of this approach argue that there is no evidence that it is any more dangerous to do so,4,5 that it leads to greater patient acceptance and comfort, and that it provides better conditions for training.5 Paradoxically it has also been stressed that only skilled anaesthetists should perform central blocks,5,6 and few would argue with Fischer’s assertion that ‘‘the major factors in preventing neurological sequelae are the experience and dexterity of the anaesthetist, proper training and supervision of trainees, detailed assessment of pre-existing vascular and neurological disease, avoidance of repeated attempts due to technical di⁄culties, and prompt recognition and treatment of complications to prevent permanent damage’’.5 Fischer has also pointed out that two major medical defence organizations in the United Kingdom do not view the administration of a general anaesthetic before a regional anaesthetic as inherently bad practice.5 Although medicolegal opinion is important, there is a di¡erence between optimum management, and what might be considered legally defensible, although the gap may be narrowing. .... for insertion before induction Bromage has highlighted that anaesthetized patients cannot give a verbal warning of symptoms of, or produce re£ex muscular responses to, pain or paraesthesia. The latter assertion is at odds with that of Fischer who believes that re£ex muscle movement will still occur. A further concern is that patients will also be unable to report any adverse symptoms to test doses of local anaesthetic for epidural, or indeed any other type of local or regional block. Adverse e¡ects may be systemic (e.g. as a result of intravascular injection) or local (e.g. unintentional subarachnoid injection during epidural block), although the consequences may still be systemic.
CURRENT ANAESTHESIA & CRITICAL CARE Bromage and others7,8 have questioned the need to perform blocks on anaesthetized patients given that it is standard practice in most centres noted for regional anaesthesia to do them ¢rst.This seems perfectly acceptable to patients if a careful technique is used, and as Bromage asks: ‘‘why risk the added risk?’’9 A key point is the question of who monitors the general anaesthetic while the block is performed, the clear inference being that patient safety may be compromised by the ‘distraction’ of the block.7 While Fischer has argued that there is no good evidence that performing blocks under general anaesthesia increases the risk, he acknowledges that the onus for proving the safety of this approach is on its proponents.
THE EVIDENCE BASE So, experts in regional anaesthesia are divided in their opinions on the subject of when to perform the block. But what evidence base is there to help the practitioner decide what to do?
Studies and surveys There is no large randomized controlled trial comparing the safety of blocks before and after induction of general anaesthesia, and it is unlikely that there ever will be. In fact, there are few large surveys examining complications of regional anaesthesia, and none which looks speci¢cally at di¡erences in incidence when the blocks are performed awake or asleep. What the available studies do show is that regional anaesthesia is safe, and that serious complications are very rare. Auroy and colleagues10 looked prospectively at over 100 000 regional anaesthetics and found the incidence of permanent neurological de¢cit to be 0.5 in10 000 and the incidence of death to be 0.9 in 10,000 (other studies have found similar incidences11,12). This suggests that any potential di¡erence in complication rates between blocks performed awake or asleep is likely to be small, and di⁄cult to demonstrate. Therefore, it seems unlikely that large surveys will ever provide a straight answer on whether there is a di¡erence in safety between the two approaches. Thus, other less direct evidence must be sought to guide practice. What Auroy and colleagues did ¢nd is that there is a signi¢cant link between pain or paraesthesia experienced on needle insertion, and subsequent nerve damage. Out of a total of 34 neurological complications recorded in their study, 21 were associated with paraesthesia on needle insertion, or pain on injection. Most of the rest involved the intrathecal injection of 5% lidocaine suggesting a direct neurotoxic e¡ect, and a di¡erent mechanism of action. Pain or paraesthesia on needle insertion have also been found to be risk factors in other large studies, albeit retrospective in nature,1,11,13 and the
CRUELTO BEKIND?
implication of this needs to be considered. Would performing the block awake be safer if the needle is withdrawn immediately on sensation of pain or paraesthesia, or will the damage have been done already? It does make sense that any damage will at least be limited if the patient is awake, the needle advanced gently, and any discomfort taken immediately as a sign of problems.
289
although the patients were awake. So was patient feedback useless in preventing damage? This series has been used to negate the argument that performing blocks in awake patients is safer,17 but did the clinicians simply ignore the warnings?
Inferential evidence Case reviews and reports What value does the presentation of reports on individual patients have to modern day medicine? The answer is ‘considerable’ in situations like this where complications are rare and may not be picked up even in largescale studies. The ‘yellow card’ system for reporting adverse drug reactions is a good example of this, and the chair and deputy chair of the Cochrane Collaborative Steering Group have recognized the limitation of even large-scale trials which unless ‘placed in the context of other relevant research, exist as islands of information’. They have also recognized that ‘one challenge facing reviewers today is how to identify and incorporate data on rare adverse events not usually available from randomised trials’.14 Unfortunately, because they tend to be carried out by enthusiasts, voluntary surveys rarely identify problems, but occasional case reviews and reports, anecdotal though they are, may provide important information. When they are publicized widely, individual cases carry enormous power, as can be seen from the history of spinal anaesthesia. A case series reported by a British trained, New York based neurologist, coincided with two high pro¢le cases in the UK, and led to the virtual demise of spinal anaesthesia in the middle of the 20th century.15 More recently, in1994, a report of two patients su¡ering major neurological injury after thoracic epidural block was published in Germany, and led to the setting up there of what amount to national guidelines.8 These state that general anaesthesia is an absolute contra-indication to thoracic epidural placement, and a relative contra-indication to all other central blocks. The guidelines also go so far as to suggest that ‘for instance a cholecystectomy or a hemicolectomy in an otherwise healthy patient is not considered to be a reasonable indication for a thoracic epidural.’ In 2001, Reynolds16 published a series of seven patients su¡ering from spinal cord damage after spinal or combined spinal/epidural (CSE) anaesthesia. In all seven patients, there was pain on insertion of the spinal needle and the neurological de¢cit emerged as the block regressed, and six of the seven had magnetic resonance imaging (MRI) evidence of a lesion in the spinal cord at a level consistent with the clinical features.Only one of the patients had pain on injection of local anaesthetic, but all had permanent de¢cit.The damage had already occurred
Two recent publications add weight to the argument that peripheral nerve block is safer if performed awake. First Choyce and colleagues,18 and then Urmey and Stanton19 have demonstrated that a motor response cannot always be elicited with a nerve stimulator after the patient has reported paraesthesiae. In both studies paraesthesiae were elicited during brachial plexus block and then the nerve stimulator was turned on. A twitch response did not occur at o0.5 mA in all patients in either study, although there were important di¡erences between the two. Urmey and Stanton enlisted 30 patients undergoing interscalene block for shoulder surgery. After paraesthesiae were obtained, a twitch was observed in only 30% of patients when the current was increased to1mA, there being no relationship between the distribution of paraesthesiae and the subsequent motor response although 20 out of the 30 needles used were un-insulated. No patient required conversion to general anaesthesia, and the surgeon’s assessment of the block was at least ‘satisfactory’ or better. Choyce and colleagues enrolled 72 patients having axillary brachial plexus block with un-insulated needles for upper limb surgery, but 19 of these were excluded, mostly because of arterial puncture. In 77% of the remainder a motor response was obtained (at o0.5 mA) after paraesthesiae. Median current was 0.17 mA, but the range was 0.03^3.3 mA, and a relationship between distribution of paraesthesiae and motor response was found in 81% of patients. Interestingly,13% of blocks required supplementary local anaesthetic, and 9% of patients required conversion to general anaesthesia. The two studies show big di¡erences in both block reliability, and the relationship between paraesthesiae and motor response. These di¡erences are important and may be explained only partly by di¡erences in block site and the needles used. However, the important message is that paraesthesiae may be experienced without motor response, and both papers concluded that nerve block would be safer in lightly sedated or awake patients.
SPECIAL PROBLEMS AND GREY AREAS There are a number of special situations where the balance of risk and bene¢t becomes altered to some degree, and these deserve special consideration.
290
Paediatric anaesthesia No discussion about the timing of regional block would be complete without consideration of paediatric practice, where blocks are now performed almost universally after induction of general anaesthesia. This is because of the particular problems of communication and compliance in children that virtually dictate that general anaesthesia must be used.This view was challenged in1998 by a report detailing the case of a 62-year-old woman, with a history of previous back surgery, who su¡ered permanent paraplegia after multiple attempts to site an epidural catheter under general anaesthesia.20 Several criticisms were made of the patient’s management, which was complicated by poor treatment of periods of intra and postoperative hypotension, and magnetic resonance imaging (MRI) showed both spinal cord infarction at T5, and gas bubbles in the spinal cord at T10 and T12. However, the authors condemned particularly the administration of a thoracic epidural in an anaesthetized patient, stating that this should only be attempted as a life-saving measure in exceptional circumstances. Subsequently, this conclusion was refuted vehemently by a large number of paediatric anaesthetists who stated that performing regional anaesthesia on anaesthetized children is a safe technique.21,22 Of the several articles cited to support their stance, one is particularly worthy of mention. A prospective French survey23 was carried out over the course of 1 year. Data from over 85 000 anaesthetics (a 51% response rate) included 24 409 with a regional component (89% under GA). Over 60% of these were central (mainly caudal) and 38% were peripheral.The results were interesting. No peripheral complications were recorded at all.The central complication rate was1.5 per 1000, although most complications were relatively minor, and none were permanent in nature. The conclusion of this impressive study was that regional anaesthesia is safe, but that peripheral blocks are safer than central ones.
Other di⁄culties with patient compliance In paediatric anaesthesia the balance of risk and bene¢t in regional block is altered because children are generally unable fully to comprehend and comply with treatment. It is possible to imagine situations in the adult population where similar conditions might prevail, and one such case has been described by Absalom and colleagues.24 Insertion of a thoracic epidural catheter was attempted prior to induction of anaesthesia for emergency abdominal surgery in an anxious Asian woman with poor English. The patient was lightly sedated, and unrestrained. During local anaesthetic in¢ltration with a 4 cm needle, the patient rolled suddenly onto her back, causing the needle to advance to its hub, and leaving the patient
CURRENT ANAESTHESIA & CRITICAL CARE
with a spinal cord injury. Although the problem might have been avoided if a needle of more appropriate length had been used for in¢ltration, the authors suggest that performing the block asleep would have probably been safer in this instance. They maintain the view, however, that regional blocks are generally safer if performed awake.
The patient in pain Patients may present for surgery, particularly emergency surgery, in severe pain and this will often make the prospect of performing regional anaesthesia prior to induction less than appealing. Positioning the patient for all but the simplest blocks may be impossible, and the twitching with a nerve stimulator may add to their distress. In addition, caution must be exercised because the patient may be hypovolaemic, or have some other relative contra-indication to central block. Nevertheless, certain patients undergoing emergency abdominal surgery may bene¢t from a thoracic epidural once the procedure is over. Does the additional bene¢t of establishing analgesia ¢rst justify inserting the epidural before the patient regains consciousness? Certainly, the consequence of spinal cord damage is so severe that any additional risk needs justi¢cation, but if the risk is very small, and the bene¢t (high-quality pain relief) so tangible, is that not justi¢cation in itself? In Germany, the answer would be a resounding ‘no’. Should it be di¡erent elsewhere?
Uncertain surgery In some situations it may be di⁄cult to predict the operation that will be performed on a patient. In some centres, including our own, diagnostic laparoscopy may precede, and often obviate the need for, laparotomy. Those that do undergo laparotomy may bene¢t from thoracic epidural block, particularly in the presence of respiratory illness. What should be done in this instance? Should the patient have an epidural sited prior to induction when it may prove to be unnecessary? Should the epidural be sited under general anaesthesia if laparotomy is performed, or should it be sited once the patient is awake and in pain? Perhaps the easiest option would be to forget the epidural altogether and prescribe PCA morphine, but that would not be optimum care for every patient. Another dilemma, cited by a group of anaesthetists in Cardi¡,6 is in anaesthesia for thoracic surgery where bronchoscopy may or may not be followed by thoracotomy. They use this to justify thoracic epidural insertion under general anaesthesia, although one alternative solution is to have separate lists for bronchoscopy and
CRUELTO BEKIND?
thoracotomy, and another to use a more peripheral block technique (e.g. Paravertebral).
SO, AWAKE OR ASLEEP? The protagonists in this debate are agreed on one thing. Regional anaesthesia must be performed carefully and cautiously by practitioners who have full knowledge of the relevant anatomy, the technique being used, its complications and the ways of avoiding them.Those (the present authors included) who favour the ‘awake’ approach note that the protagonists of the‘asleep’ approach accept that they have to prove that it is a safe one. They also have to be able to answer several questions: 1. Why do the block with the patient asleep? 2. Why not do the block with the patient awake? 3. Is there an alternative to an invasive procedure on an unconscious patient? 4. Who will monitor the patient while the block is being performed? The answer to the‘awake or asleep’question relates to the balance of risk and bene¢t, so proscriptive national guidelines such as those in place in Germany, although well intentioned, are probably unnecessary because they remove the clinician’s ability to tailor the anaesthetic to the patient. Anaesthetists would be well advised to perform all blocks in awake or lightly sedated patients if at all possible, but there must be a place for the alternative.This principle is of particular importance for central blocks where the potential for damage is greatest, but it also applies to peripheral nerve block. In instances where more than one block is used the more peripheral block should be inserted ¢rst where possible. Finally, an interesting observation with which to close. A recent survey of anaesthetists in the Oxford region has shown a di¡erence between beliefs and working practices.25 While most anaesthetists believed that blocks were safer performed awake, the majority still performed most of their blocks on anaesthetized patients. Instead of being cruel to be kind, is this a case of being kind to be cruel? It is time to question this anomaly, and practise what we believe to ensure the safety of our patients.
REFERENCES 1. Cheney F W, Domino K B, Caplan R A, Posner K L. Nerve injury associated with anesthesia: a closed claims analysis. Anesthesiology 1999; 90(4): 1062–1069. 2. Aitkenhead A R. The pattern of litigation against anaesthetists. Br J Anaesth 1994; 73(1): 10–21. 3. Bromage P R. Masked mischief. Reg Anesth 1996; 21(6 Suppl): 62–63.
291
4. Gough J D, Williams A B, Vaughan R S, Khalil J F, Butchart E G. The control of post-thoracotomy pain. A comparative evaluation of thoracic epidural fentanyl infusions and cryo-analgesia. Anaesthesia 1988; 43(9): 780–783. 5. Fischer H B. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1998; 53(8): 727–729. 6. Vaughan R S, Gough J D. The control of post-thoracotomy pain: a reply. Anaesthesia 1989; 44: 445–446. 7. Wildsmith J A. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1999; 54: 86. 8. Gruning T. Regional anaesthesiaFbefore or after general anaesthesia? Anaesthesia 1999; 54: 86–87. 9. Bromage P R. The control of post-thoracotomy pain. Anaesthesia 1989; 44(5): 445–446. 10. Auroy Y, Narchi P, Messiah A, Litt L, Rouvier B, Samii K. Serious complications related to regional anaesthesia: results of a prospective survey in France. Anesthesiology 1997; 87(3): 479–486. 11. Aromaa U, Lahdensuu M, Cozanitis D A. Severe complications associated with epidural and spinal anaesthesias in Finland 1987–1993. A study based on patient insurance claims. Acta Anaesthesiol Scand 1997; 41(4): 445–452. 12. Horlocker T T, Wedel D J. Neurologic complications of spinal and epidural anaesthesia. Reg Anesth Pain Med 2000; 25(1): 83–98. 13. Horlocker T T, McGregor D G, Matsushige D K, Schroeder D R, Besse J A. A retrospective review of 4767 consecutive spinal anesthetics: central nervous system complications. Perioperative Outcomes Group. Anesth Analg 1997; 84(3): 578–584. 14. Clarke M, Langhorne P. Revisiting the Cochrane Collaboration. Meeting the challenge of Archie CochraneFand facing up to some new ones. BMJ 2001; 323(7317): 821. 15. Wildsmith J A, Lee J A. Neurological sequelae of spinal anaesthesia. Br J Anaesth 1989; 63(5): 505–507. 16. Reynolds F. Damage to the conus medullaris following spinal anaesthesia. Anaesthesia 2001; 56(3): 238–247. 17. Vaughan R S. Pain relief after thoracotomy. Br J Anaesth 2001; 87(5): 681–683. 18. Choyce A, Chan V W, Middleton W J, Knight P R, Peng P, McCartney C J. What is the relationship between paresthesia and nerve stimulation for axillary brachial plexus block? Reg Anesth Pain Med 2001; 26(2): 100–104. 19. Urmey W F, Stanton J. Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration. Anesthesiology 2002; 96(3): 552–554. 20. Bromage P R, Benumof J L. Paraplegia following intracord injection during attempted epidural anesthesia under general anesthesia. Reg Anesth Pain Med 1998; 23(1): 104–107. 21. Krane E J, Dalens B J, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23(5): 433–438. 22. Bosenberg A T, Ivani G. Regional anaesthesiaFchildren are different. Paediatr Anaesth 1998; 8(6): 447-450. 23. Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg 1996; 83(5): 904–912. 24. Absalom A R, Martinelli G, Scott N B. Spinal cord injury caused by direct damage by local anaesthetic infiltration needle. Br J Anaesth 2001; 87(3): 512–515. 25. Kadry M A, Rutter S V, Popat M T. Regional anaesthesia for limb surgery–before or after general anaesthesia. A survey of anaesthetists in the Oxford region. Anaesthesia 2001; 56(5): 450–453.
292
FURTHER READING Urmey W F. Regional anaesthesia is potentially dangerous in anaesthetised adult patientsFpro. http://www.esraeurope.org/abstracts/abstracts99/urmey2.htm Fischer B. Regional anaesthesia is potentially dangerous in anaesthetised patients F con. http://www.esraeurope.org/abstracts/abstracts99/fischer3.htm Urmey W F, Stanton J. Inability to consistently elicit a motor response following sensory paresthesia during interscalene block administration. Anesthesiology 2002; 96(3): 552–554.
CURRENT ANAESTHESIA & CRITICAL CARE
Choyce A, Chan V W, Middleton W J, Knight P R, Peng P, McCartney C J. What is the relationship between paresthesia and nerve stimulation for axillary brachial plexus block? Reg Anesth Pain Med 2001; 26(2): 100–104. Krane E J, Dalens B J, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23(5): 433–438.