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RESPIRATORY DEPRESSION AFTER EXTRADURAL FENTANYL
BRITISH JOURNAL OF ANAESTHESIA
166 18. Montiel C, Artalejo AR, Bermejo PM, Sanchez-Garcia P. A dopaminergic receptor in adrenal medulla as a possible site of action for the droperidol-evoked hypertensive response. Anesthesiology 1986; 65: 474-^79.
TABLE I. Results for fibreoptic scoring. Score 4 = only cords; 3 = cords plus posterior epiglottis; 2 — cords plus anterior epiglottis; 1 = cords not seen, but function adequate; 0 = failure to insert within 60 s or to function
C. Y. WANG
Score
Kuala Lumpur 1. Marty M, Pouillart P, Scholl S, Droz JP, Azab M, Brion N, Pujade-Lauraine E, Paule B, Paes D, Bons J. Comparison of the 5-hydroxytryptamine3 (serotonin) antagonist ondansetron (GR 38032F) with high-dose metoclopramide in the control of cisplatin-induced emesis. New England Journal of Medicine 1990; 322: 816-821. 2. Gourlay GK, Murphy TM, Plummer JL, Kowalski SR, Cherry DA, Cousins MJ. Pharmacokinetics of fentanyl in lumbar and cervical CSF following lumbar epidural and intravenous administration. Pain 1989; 38: 253-259. 3. Cousins MJ, Mather LE. Intrathecal and epidural administration of opioids. Anesthesiology 1984; 61: 276-310.
NEUROMUSCULAR BLOCK AND INSERTION OF THE LARYNGEAL MASK AIRWAY Sir,—We have been following the recent correspondence about hypoxaemia and laryngeal mask airway (LMA) insertion and were interested in the comments on insertion under neuromuscular block [1, 2]. Hayes, Allsop and Gillies found that insertion of the LMA was difficult in 16 of 87 patients after induction of anaesthesia with propofol 2 mg kg"1 and fentanyl 1 |ig kg""1 [3]. In contrast, Yaddanapudi and colleagues found that thiopentone 3-6 mg kg"1 and suxamethonium 1.5 mg kg"1 resulted in only one difficult insertion in 20 subjects [1]. Based on these results, Yaddanapudi's group suggested that insertion of the LMA under neuromuscular block was a viable alternative to insertion with
Group A Group B Total
4
3
2
1
0
score
23 26 49
10 6 16
6 10 16
1 7 8
0 1 1
3.4 3.0 32
These data suggest that there is no difference between ease of insertion of the LMA using propofol 2.5 mg kg"1 and fentanyl 1 ug kg"1 compared with thiopentone 4-6 mg kg"1 and suxamethonium 1 mg kg"1. It is possible that smaller doses of propofol, as used by Haynes, Allsop and Gillies [3] may make conditions less favourable for LMA insertion, although Blake and colleagues found no difference in ease of insertion of the LMA when comparing a dose of 2 mg with 2.5 mg at 90 s [6]. It would seem that neuromuscular block provides good conditions for LMA insertion, but no better than those provided by an adequate dose of induction agent. Given the lack of improvement in insertion conditions, there would appear to be no advantage in routinely using neuromuscular blocking drugs to aid insertion. We also suggest that, if an adequate dose of induction agent has been administered and there is subsequent difficulty in LMA insertion, suxamethonium would not improve conditions for insertion. If tracheal intubation has failed, however, it is useful to know that LMA insertion can be achieved easily if the patient is still paralysed. J. BRIMACOMBE A. BERRY
Royal Perth Hospital Perth, Australia
Downloaded from http://bja.oxfordjournals.org/ at Harvard University on July 25, 2015
Sir,—The suggestion of a ventilatory depressant interaction between systemic antiemetic (in this case metoclopramide) and CSF opioid is interesting. Metoclopramide has been used extensively for the treatment and prevention of nausea and vomiting, in the past 30 years and there is an extensive literature on its efficacy. Recognized side effects of metoclopramide include extrapyramidal reactions, sedation, restlessness and cardiovascular effects. However, respiratory depression has not been reported and high-dose metoclopramide has been used in the prevention of nausea and vomiting in patients receiving chemotherapeutic agents [1]. Chrubasik, Chrubasik and Black have concentrated their comments on the dosage and the time course of respiratory depression. The respiratory depression observed after extradural fentanyl may be caused by three mechanisms alone or in combination: a systemic effect; rostral spread in the CSF [2]; rostral spread via a direct perimedullary channel [3]. A systemic effect seems unlikely. It is generally accepted that fentanyl, a highly lipid-soluble opioid, easily crosses the dura and quickly penetrates the spinal cord, inducing segmental analgesia without the side effects associated with migration of the opioid in a rostral direction [3]. However, the study by Gourlay and colleagues [2] demonstrated rapid (30 min) appearance of large concentrations of fentanyl in cervical CSF after lumbar extradural, but not in i.v., fentanyl injection. The mechanism for this rapid redistribution is uncertain, but it may explain cases of rapid-onset, severe respiratory depression from lipid-soluble opioids. In my case report, respiratory depression occurred 80 min after the initial injection of bupivacaine and fentanyl. It seems probable, therefore, that the respiratory depression in this patient was caused by the larger doses of fentanyl being administered, enhancing rostral spread via a direct perimedullary vascular channel [3]. I agree strongly with Drs Chrubasik, Chrubasik and Black that the utmost vigilance should be maintained with every use of extradural opioids.
propofol and might be considered when the requirements of surgery necessitated controlled ventilation. As Gillies commented [2], it is difficult to make direct comparisons between separate studies with different designs. We present data from the control groups of the two LMA insertion studies we have conducted and which followed similar designs and incorporated standardized criteria for successful insertion. From these data, we feel that a more conclusive statement can be made regarding ease of insertion of the LMA with propofol and fentanyl compared with thiopentone and suxamethonium. Ethics Committee approval and informed consent were obtained for both studies. Control group A comprised 40 patients in whom anaesthesia was induced with fentanyl 1 ug kg"1 followed, 2 min later, by propofol 2.5mgkg~1. In control group B, 50 patients underwent induction of anaesthesia with thiopentone 4-6 mg kg"1 and, after loss of consciousness and lash reflex, were given suxamethonium 1 mgkg"1. All the patients were fasted, ASA I—II and were monitored with an ECG, pulse oximeter and Dinamap. All patients were preoxygenated for 3 min, with no subsequent manual ventilation. A standard insertion technique was used in both groups [4]. In control group A, LMA insertion was attempted 1 min after completion of propofol injection. In control group 2, LMA insertion was attempted when fasciculations had ceased. When the LMA was in position, afibreopticscope was passed to the level of the mask aperture bars and the view scored [5]. Function was assessed by gentle hand ventilation and synchronous observation of chest wall movement. The mean age, weight and male: female ratio were similar in the two groups. The results for fibreoptic scoring are shown in table I. In all patients, oxygen saturation remained greater than 94%. In control group A, all LMA were inserted within 10 s of placing the bowl of the LMA in the mouth to inflation of the cuff. In control group B, there was one failure and in all other patients the insertion time was between 5 s and 18 s from the time the LMA was picked up to inflation of the cuff. The distribution by fibreoptic scoring between control group A and group B was analysed using the chi-square test and revealed no significant difference.
166 18. Montiel C, Artalejo AR, Bermejo PM, Sanchez-Garcia P. A dopaminergic receptor in adrenal medulla as a possible site of action for the droperidol-evoked hypertensive response. Anesthesiology 1986; 65: 474-^79.
TABLE I. Results for fibreoptic scoring. Score 4 = only cords; 3 = cords plus posterior epiglottis; 2 — cords plus anterior epiglottis; 1 = cords not seen, but function adequate; 0 = failure to insert within 60 s or to function
C. Y. WANG
Score
Kuala Lumpur 1. Marty M, Pouillart P, Scholl S, Droz JP, Azab M, Brion N, Pujade-Lauraine E, Paule B, Paes D, Bons J. Comparison of the 5-hydroxytryptamine3 (serotonin) antagonist ondansetron (GR 38032F) with high-dose metoclopramide in the control of cisplatin-induced emesis. New England Journal of Medicine 1990; 322: 816-821. 2. Gourlay GK, Murphy TM, Plummer JL, Kowalski SR, Cherry DA, Cousins MJ. Pharmacokinetics of fentanyl in lumbar and cervical CSF following lumbar epidural and intravenous administration. Pain 1989; 38: 253-259. 3. Cousins MJ, Mather LE. Intrathecal and epidural administration of opioids. Anesthesiology 1984; 61: 276-310.
NEUROMUSCULAR BLOCK AND INSERTION OF THE LARYNGEAL MASK AIRWAY Sir,—We have been following the recent correspondence about hypoxaemia and laryngeal mask airway (LMA) insertion and were interested in the comments on insertion under neuromuscular block [1, 2]. Hayes, Allsop and Gillies found that insertion of the LMA was difficult in 16 of 87 patients after induction of anaesthesia with propofol 2 mg kg"1 and fentanyl 1 |ig kg""1 [3]. In contrast, Yaddanapudi and colleagues found that thiopentone 3-6 mg kg"1 and suxamethonium 1.5 mg kg"1 resulted in only one difficult insertion in 20 subjects [1]. Based on these results, Yaddanapudi's group suggested that insertion of the LMA under neuromuscular block was a viable alternative to insertion with
Group A Group B Total
4
3
2
1
0
score
23 26 49
10 6 16
6 10 16
1 7 8
0 1 1
3.4 3.0 32
These data suggest that there is no difference between ease of insertion of the LMA using propofol 2.5 mg kg"1 and fentanyl 1 ug kg"1 compared with thiopentone 4-6 mg kg"1 and suxamethonium 1 mg kg"1. It is possible that smaller doses of propofol, as used by Haynes, Allsop and Gillies [3] may make conditions less favourable for LMA insertion, although Blake and colleagues found no difference in ease of insertion of the LMA when comparing a dose of 2 mg with 2.5 mg at 90 s [6]. It would seem that neuromuscular block provides good conditions for LMA insertion, but no better than those provided by an adequate dose of induction agent. Given the lack of improvement in insertion conditions, there would appear to be no advantage in routinely using neuromuscular blocking drugs to aid insertion. We also suggest that, if an adequate dose of induction agent has been administered and there is subsequent difficulty in LMA insertion, suxamethonium would not improve conditions for insertion. If tracheal intubation has failed, however, it is useful to know that LMA insertion can be achieved easily if the patient is still paralysed. J. BRIMACOMBE A. BERRY
Royal Perth Hospital Perth, Australia
Downloaded from http://bja.oxfordjournals.org/ at Harvard University on July 25, 2015
Sir,—The suggestion of a ventilatory depressant interaction between systemic antiemetic (in this case metoclopramide) and CSF opioid is interesting. Metoclopramide has been used extensively for the treatment and prevention of nausea and vomiting, in the past 30 years and there is an extensive literature on its efficacy. Recognized side effects of metoclopramide include extrapyramidal reactions, sedation, restlessness and cardiovascular effects. However, respiratory depression has not been reported and high-dose metoclopramide has been used in the prevention of nausea and vomiting in patients receiving chemotherapeutic agents [1]. Chrubasik, Chrubasik and Black have concentrated their comments on the dosage and the time course of respiratory depression. The respiratory depression observed after extradural fentanyl may be caused by three mechanisms alone or in combination: a systemic effect; rostral spread in the CSF [2]; rostral spread via a direct perimedullary channel [3]. A systemic effect seems unlikely. It is generally accepted that fentanyl, a highly lipid-soluble opioid, easily crosses the dura and quickly penetrates the spinal cord, inducing segmental analgesia without the side effects associated with migration of the opioid in a rostral direction [3]. However, the study by Gourlay and colleagues [2] demonstrated rapid (30 min) appearance of large concentrations of fentanyl in cervical CSF after lumbar extradural, but not in i.v., fentanyl injection. The mechanism for this rapid redistribution is uncertain, but it may explain cases of rapid-onset, severe respiratory depression from lipid-soluble opioids. In my case report, respiratory depression occurred 80 min after the initial injection of bupivacaine and fentanyl. It seems probable, therefore, that the respiratory depression in this patient was caused by the larger doses of fentanyl being administered, enhancing rostral spread via a direct perimedullary vascular channel [3]. I agree strongly with Drs Chrubasik, Chrubasik and Black that the utmost vigilance should be maintained with every use of extradural opioids.
propofol and might be considered when the requirements of surgery necessitated controlled ventilation. As Gillies commented [2], it is difficult to make direct comparisons between separate studies with different designs. We present data from the control groups of the two LMA insertion studies we have conducted and which followed similar designs and incorporated standardized criteria for successful insertion. From these data, we feel that a more conclusive statement can be made regarding ease of insertion of the LMA with propofol and fentanyl compared with thiopentone and suxamethonium. Ethics Committee approval and informed consent were obtained for both studies. Control group A comprised 40 patients in whom anaesthesia was induced with fentanyl 1 ug kg"1 followed, 2 min later, by propofol 2.5mgkg~1. In control group B, 50 patients underwent induction of anaesthesia with thiopentone 4-6 mg kg"1 and, after loss of consciousness and lash reflex, were given suxamethonium 1 mgkg"1. All the patients were fasted, ASA I—II and were monitored with an ECG, pulse oximeter and Dinamap. All patients were preoxygenated for 3 min, with no subsequent manual ventilation. A standard insertion technique was used in both groups [4]. In control group A, LMA insertion was attempted 1 min after completion of propofol injection. In control group 2, LMA insertion was attempted when fasciculations had ceased. When the LMA was in position, afibreopticscope was passed to the level of the mask aperture bars and the view scored [5]. Function was assessed by gentle hand ventilation and synchronous observation of chest wall movement. The mean age, weight and male: female ratio were similar in the two groups. The results for fibreoptic scoring are shown in table I. In all patients, oxygen saturation remained greater than 94%. In control group A, all LMA were inserted within 10 s of placing the bowl of the LMA in the mouth to inflation of the cuff. In control group B, there was one failure and in all other patients the insertion time was between 5 s and 18 s from the time the LMA was picked up to inflation of the cuff. The distribution by fibreoptic scoring between control group A and group B was analysed using the chi-square test and revealed no significant difference.