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Correspondence Epidural Morphine for Analgesia After Caesarean Section To the Editor: In a recent study of epidural morphine after Caesarcan section Carmichael et al. conclude that 'This technique of pain management is reliable and safe using a 4 mg dose .... Our experience suggests that patients would be adequately monitored postpartum on the ward if vital signs were taken hourly for the first 8 to 12 hours after each epidural dose of morphine.' Only 29 patients were studied, ten receiving morphine 4 mg epidurally. Respiratory rate was the only way of monitoring the ventilation and blood gases were not checked in the group receiving morphine 4 nag. Rare, but serious late respiratory depression has been a major problem in epidural morphine analgesia, 2-~ a fact which was stressed in your epidural 'D~j/~Vu' less than a year ago. 6 In the same volume Knill et al. 7 showed that epidural morphine changed the respiratory pattern in healthy individuals, and that ventilator), depression primarily was due to reductions in tidal volume. Accordingly I question the appropriateness of a general statement such as the one cited above, based upon the study reported. Carmichael's recommendation to keep these patients in ordinary obstetric wards may sooner or later bring about sedt~us or even catastrophic consequences. Patients receiving epidural morphine would be safer in intensive care units. Per Egil Haavik, MD Department of Anesthesiology, Ullev/il Hospital University of Oslo Oslo, Norway REI~RENCES

I Carmichaet FJ, Rolbin SIC, Hew EM. Epidural

CAN' A N A E S T H S O C J 1 9 8 3 / 30: I / pp 108-10

Morphine for analgesia after Caesarean section. Can Anaesth Soc J 1982; 29: 359-63. 2 Glynn CJ, Mother LE, Cousins M J, Wilson PR, Graham JR. Spinal rmreotics and respiratory

depression. Lancet 1979; 2: 356-7. 3 Davies GK, Tolharst-Gleaver CL, James TL. CNS

4 5 6 7

depression from intratheca! morhine. Anesthesiology 1980; 52: 280. Christensen V. Respiratory depression after extradural morphine. Br 2 Artaesth 1980; 52: 841. Reiz S, Westberg M. Side effects of epidural morphine. Lancet 1980; 2: 203-4. Wyant GM. I~j~t Vu. Editorial. Can Anaesth Soc J 1981; 28: 551-2. KnillRL, ClementJL, Thompson WR. Epidural Morphine Causes delayed and prolonged ventilatory depression. Can Anaesth Soc J I981; 28: 537-43.

REPLY Thank you for the invitation to reply to Dr. Haavik's letter concerning our article 'Epidural Morphine for Analgesia after Caesarean Section' published in the July 1982 issue of the Journal. Our study was a randomized double blind placebo controlled study of efficacy, duration and safety of epidural morphine for the management of postcaesarean section pain. Dr. Haavik is concerned, as indeed we are, about the safety of this technique. To date, epidural morphine administration to more than 8,000 patients has been reported. One recent survey of practice in Sweden t reported respiratory depression in 23 patients out of 6,000 who received epidural morphine. Delayed respiratory depression after epidural narcottcs ~s more frequent if the patient is elderly, debilitated, has bnpaired respiratory functions or has received both epidural and systemic opiates. All of the case reports referred to by Dr, Haavik are in this category except possibly the case reported by Reiz and Westburg3 who unfortunately did not state the age of their patient. We are not aware of any case reports of delayed respiratory depression in young healthy patients following epidural morphine in acceptable doses (e.g. lesa than 5 m~). The investigations by Knitl et al~ were done in normal healthy individuals who had not undergone surgery. Postoperative patients receiving epidural morphine need to be compared to those receiving parenteral morphine. The clinical applicabili~ of such studies is more obvious. Lastly, we are not recommending the use of epidural

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CORF~ESPONDENCE

morphine on 'ordinary' obstetric wards. We stated our belief that vital signs need to be taken hourlyfor thefirst 8 to 12 hours. This would be possible because the improved

patient comfort would require less nursing care. Since this technique is relatively new, its safety is not 100 per cent proven. However, the large numbers of patients reported in the literature to date suggests that 'serious or catastrophic consequences' are not inevitable if patients are selected using the guidelines referred to above.

S. Rolbin, MOCMVRC1'(C) Department of Anaesthesia Mount Sinai Hospital, Toronto

whose importance cannot be ignored with impunity. No doubt others before me have suggested the introduction of uniform colour coding for the labels of anaesthetic (if not all) drugs, but present circumstances prompt me to add my voice to theirs. 1 would propose that distinguishing colours be reserved for the labels of at least the following classes of commonly used drugs: narcotics - barbiturates and other hypnotics muscle relaxants autonomic agonists and antagonists anticholinesterases -

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REFERENCES

1 GJ'~stafsonnLL, Schlldt B, Jacobsen K. Adverse Ef-

fe~:tsof Extradural and lntrathecal Opiates: Report of a Nationwide Survey in Sweden. Br J Anaesth 1983; 54: 479-85. 2 Reiz S, Westberg M. Side Effects of Epidural Morphine. Lancet 1980; 2: 537-43. 3 1Chill RL, Clement JL, Thompson WR. Epidural MorphineCauses Delayed and Prolonged Vemilatory Depression. Can Anacsth Soc J 1981; 28: 537-43.

Colour Coding of Drug Labels To the Editor: The Burroughs Wellcome company has introduced a potentially hazardous change in the labelling of 5 ml ampoules of Anectine| (suecinylcholine). These ampoules have been labelled in yellow for many years and their characteristic appearance has come virtually to identify their contents to anaesthetists accustomed to using this brand of the drug. Without warning, the colour of the label has been changed to red, giving an ampoule of Anectine a striking resemblance to a 5 ml ampoule of Sublimazes', a brand of fentanyl in common use. The possible confusion between a syringe containing 100 mg of suceinylcholine instead of 250 v.g of fentanyt, or vice versa, and the hazard thereby engendered surely needs no further elaboration. Wh:ile it is a fundamental tenet of safe anaesthetic practice that the contents of an ampoule be verified by careful inspection of the label, nonetheless, in the identificationof drugs, medical gases and equipment sizes, visual cues such as colour play a part

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Christopher P. Bates, MD, FRCP (C) Department of Anaesthesia The University of British Columbia Health Sciences Centre Hospital REPLY We are indebted to Dr. Bates for his letter highlighting the ease with which label changes can create potentially dangerous situations in the operating room. As all the readers of this journal are no doubt aware, as soon as Burroughs WeUcome discovered this potential hazard, we immediately re-designed the label and froze all stocks of the drug in our warehouses, at the same time notifying all chiefs of anaesthesia and hospital pharmacists. Drug labels are designed to be maximally informative and distinctive and are closely regulated by the Health Protection Branch in Ottawa. I do not know however of any nationally accepted mechanism that could prevent the incident which has occurred, because this process is conducted outside the context of routine ctinical practice. It would, I suggest, be appropriate for the Canadian Anaesthetists' Society to appoint a committee to monitor all drug labels and maintain a dialogue with the drug industry. In the meantime I would urge us atl to remember the aphorism ingrained in us at medical school 'always, always read the ruddy label."

MalcolmF/etcher, tRcr(Lond), ~al~CS(Eng)OA(RCS)(Eng) Medical Director Burroughs Wellcome Inc. Montreal, Quebec