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NITROPRUSSIDE INFUSIONS
Br. J. Anaesth. (1983), 55,919
CORRESPONDENCE MONITORING OF NEUROMUSCULAR FUNCTION AND ATRACURIUM
P. J. A. HARDY Edinburgh REFERENCE
Hunter, J. M., Jones, R. S., and Uttingj J. E. (1982). Use of atracurium during general surgery monitored by the train of four stimuli. Br. J. Anaesth., 54,1243.
G.G.GRAHAM D. RIGG
Dariinghunt, N.S.W. REFERENCES
NITROPRUSSIDE INFUSIONS
Sir,—Bisset and colleagues (1981) stated that light must be vigorously excluded from nitroprusside infusions, to prevent breakdown ^o aquapentacyanoferrate. This complex iori readily breaks down to yield cyanide. Although it is cominon practice to protect the infusion solution of sodium nitroprusside from light, light is usually not excluded completely. Nitroprussidc infusions are conJmonly controlled by drip counters incorporating a light beam through the drip chamber and neither the drip chamber not the infusion tubing is protected from ambient light. The rate of infusion is often slow and, consequently, there may be considerable exposure to light even though the reservoir is protected. Vesey and Batistoni (1977) have reported a 10% decrease in potency 6f nitroprusside solutions after 3 h exposure to strong sunlight, but in view of the comment of Bisset and colleagues (1981) that light must be completely excluded, we have examined the cyanide concentrations in infusion solutions of nitrbprusslde under the conditions in which they are administered. Two infusions were set up, each containing sodium nitroprusside (Nipride, Roche) in 5% Dextrose (Travenol) to yield solutions containing 200 mg litre"1. The solutions were administered via infusion sets incorporating burette and drip chambers which allowed microdrip delivery (60 drops per ml) (Metriset, McGaw). The reservoir solutions and burettes were totally covered by aluminium foil, while the drip chambers and infusion tubing were left exposed to room lighting. Both infusions were regulated at a rate of 0.83 ml min"1 (50 microdrops per min). One was controlled by an infusion pump incorporating a drop counter with an incandescent light beam and
Bisset, W. I. K., Butler, A. R., Glidewell, C , and Reglinski, J. (1981). Sodium nitroprusside and cyanide release: reasons for re-appraisal. Br. J. Anaesth., 53,1015. Lundquist, P., Martensson, J., Sorbo, B., and Ohman, S. (1979). Method for determining thiocyanate in serum and urine. Clin. Chem., 25, 678. Vesey, C. J. and Batistoni, G. A. (1977). The determination and stability of sodium nitroprusside in aqueous solutions. / . Clin. Pharmac.,2,105. DEMAND ANALGESIA
Sir,—I am writing in support of Dr Gibbs and associates' article on demand analgesia (DA) (Gibbs, Johnson and Davis, 1982). They correctly emphasize the great person-to-person variance in narcotic requirements following comparable surgical interventions and indicate that drug requirements in the same person are a function of time as well. This would have been brought into sharper focus had they been able to follow their subjects' drug intake for more than 24 h. Our experience supports their finding that a patient's drug requirements are greatest at the time when conventional wisdom limits them to fractional doses of their eventual narcotic prescriptions. A patient population that self-administers 25% more narcotic when the drug is made available in larger increments is not to be trusted as analgesic sensors or, alternately, the parameters of drug administration were less than optimal in this respect. To our mind the latter is true. The average dosing interval following the administration of buprenorphine 0.1 mg turns out to be 2.14h;
Downloaded from http://bja.oxfordjournals.org/ at The University of British Colombia Library on July 10, 2015
Sir,—In their paper on the use of atracurium in general surgical patients Hunter, Jones and Utting (1982) observed that "recovery from each and every incremental dose . i. was rapid" when monitored by a train-of-four stimulus. Recent use of atracurium 0.6mgkg~' in paediatric patients during halothanesupplemented anaesthesia showed spontaneous recovery with triggering of the ventilator (Servo 900B) after 35-40 min in most patients. In two unpremedicated.patients undergoing emergency appendicectomy, spontaneous triggering was followed rapidly by movement, particularly of the abdominal wall, which interrupted surgery. It would appear, therefore, that objective monitoring of neuromuscular function is essential when using atracurium—particularly in paediatric patients.
sensor (Tekmar T51), while the control infusion was regulated manually by means of the roller clamp of the infusion set. The volume of the tubing exposed to light was 14 ml, indicating a mean, exposure time to light of 17 min. Both infusions were administered for 2,h continuously at the predetermined rate. Samples for cyanide assay were collected from the end of the infusion sets. The experiment was duplicated and all assays were run in duplicate. Aliquots of infusion solution (1 ml) were mixed with 10% sulphuric acid 0.2 ml in the outer well of a Conway diffusion cell with sodium hydroxide 0.1 mol litre" 1 ,0.6 ml in the centre well. After diffusion in the dark for 3.5h, the alkaline solution in the centre well was assayed for cyanide by the colorimetric method of Lundquist and colleagues (1979). No cyanide was detected in either nitroprusside infusion solution. Standard curves were linear in the range 2-10;imollitre~ 1 and recovery of cyanide added to the infusion solution was quantitative within this range. We conclude that no significant amounts of cyanide are delivered to the patient under the present conditions of administration of nitroprusside, even though there is some exposure to light.
CORRESPONDENCE MONITORING OF NEUROMUSCULAR FUNCTION AND ATRACURIUM
P. J. A. HARDY Edinburgh REFERENCE
Hunter, J. M., Jones, R. S., and Uttingj J. E. (1982). Use of atracurium during general surgery monitored by the train of four stimuli. Br. J. Anaesth., 54,1243.
G.G.GRAHAM D. RIGG
Dariinghunt, N.S.W. REFERENCES
NITROPRUSSIDE INFUSIONS
Sir,—Bisset and colleagues (1981) stated that light must be vigorously excluded from nitroprusside infusions, to prevent breakdown ^o aquapentacyanoferrate. This complex iori readily breaks down to yield cyanide. Although it is cominon practice to protect the infusion solution of sodium nitroprusside from light, light is usually not excluded completely. Nitroprussidc infusions are conJmonly controlled by drip counters incorporating a light beam through the drip chamber and neither the drip chamber not the infusion tubing is protected from ambient light. The rate of infusion is often slow and, consequently, there may be considerable exposure to light even though the reservoir is protected. Vesey and Batistoni (1977) have reported a 10% decrease in potency 6f nitroprusside solutions after 3 h exposure to strong sunlight, but in view of the comment of Bisset and colleagues (1981) that light must be completely excluded, we have examined the cyanide concentrations in infusion solutions of nitrbprusslde under the conditions in which they are administered. Two infusions were set up, each containing sodium nitroprusside (Nipride, Roche) in 5% Dextrose (Travenol) to yield solutions containing 200 mg litre"1. The solutions were administered via infusion sets incorporating burette and drip chambers which allowed microdrip delivery (60 drops per ml) (Metriset, McGaw). The reservoir solutions and burettes were totally covered by aluminium foil, while the drip chambers and infusion tubing were left exposed to room lighting. Both infusions were regulated at a rate of 0.83 ml min"1 (50 microdrops per min). One was controlled by an infusion pump incorporating a drop counter with an incandescent light beam and
Bisset, W. I. K., Butler, A. R., Glidewell, C , and Reglinski, J. (1981). Sodium nitroprusside and cyanide release: reasons for re-appraisal. Br. J. Anaesth., 53,1015. Lundquist, P., Martensson, J., Sorbo, B., and Ohman, S. (1979). Method for determining thiocyanate in serum and urine. Clin. Chem., 25, 678. Vesey, C. J. and Batistoni, G. A. (1977). The determination and stability of sodium nitroprusside in aqueous solutions. / . Clin. Pharmac.,2,105. DEMAND ANALGESIA
Sir,—I am writing in support of Dr Gibbs and associates' article on demand analgesia (DA) (Gibbs, Johnson and Davis, 1982). They correctly emphasize the great person-to-person variance in narcotic requirements following comparable surgical interventions and indicate that drug requirements in the same person are a function of time as well. This would have been brought into sharper focus had they been able to follow their subjects' drug intake for more than 24 h. Our experience supports their finding that a patient's drug requirements are greatest at the time when conventional wisdom limits them to fractional doses of their eventual narcotic prescriptions. A patient population that self-administers 25% more narcotic when the drug is made available in larger increments is not to be trusted as analgesic sensors or, alternately, the parameters of drug administration were less than optimal in this respect. To our mind the latter is true. The average dosing interval following the administration of buprenorphine 0.1 mg turns out to be 2.14h;
Downloaded from http://bja.oxfordjournals.org/ at The University of British Colombia Library on July 10, 2015
Sir,—In their paper on the use of atracurium in general surgical patients Hunter, Jones and Utting (1982) observed that "recovery from each and every incremental dose . i. was rapid" when monitored by a train-of-four stimulus. Recent use of atracurium 0.6mgkg~' in paediatric patients during halothanesupplemented anaesthesia showed spontaneous recovery with triggering of the ventilator (Servo 900B) after 35-40 min in most patients. In two unpremedicated.patients undergoing emergency appendicectomy, spontaneous triggering was followed rapidly by movement, particularly of the abdominal wall, which interrupted surgery. It would appear, therefore, that objective monitoring of neuromuscular function is essential when using atracurium—particularly in paediatric patients.
sensor (Tekmar T51), while the control infusion was regulated manually by means of the roller clamp of the infusion set. The volume of the tubing exposed to light was 14 ml, indicating a mean, exposure time to light of 17 min. Both infusions were administered for 2,h continuously at the predetermined rate. Samples for cyanide assay were collected from the end of the infusion sets. The experiment was duplicated and all assays were run in duplicate. Aliquots of infusion solution (1 ml) were mixed with 10% sulphuric acid 0.2 ml in the outer well of a Conway diffusion cell with sodium hydroxide 0.1 mol litre" 1 ,0.6 ml in the centre well. After diffusion in the dark for 3.5h, the alkaline solution in the centre well was assayed for cyanide by the colorimetric method of Lundquist and colleagues (1979). No cyanide was detected in either nitroprusside infusion solution. Standard curves were linear in the range 2-10;imollitre~ 1 and recovery of cyanide added to the infusion solution was quantitative within this range. We conclude that no significant amounts of cyanide are delivered to the patient under the present conditions of administration of nitroprusside, even though there is some exposure to light.