Canadian Anaesthetists' Society journal
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This study involves ventilation of the lungs with warmed humidifed anaesthetic gases during prolonged elective abdominal operations. Tympanic, oesophageal and toe temperatures were compared bewteen twenty warmed and twenty un-warmed patients at various times during operation and recovery. Fifty per cent (10/20) unwarmed patients shivered in the recovery room, while none of the warmed patients shivered. Our data indicate that pulmonary ventilation with warm humidified anaesthetic gases provides heat transfer by the lungs, preventing hypothermia during operation and post -anaesthesia shivering is prevented by maintaining the patient normothermic in both the operating room and the recovery room.
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Several recently reported deaths following the use of sodium nitroprusside have been attributed to the accumulation of the nitroprusside metabolite, cyanide. In this study, brief nitroprusside infusions (mean = 36 minutes) were administered in currently recommended doses during intracranial surgery. The peak blood cyanide following the infusions was 65.2 +/- 17.5 microgram per cent (mean +/- SE) (n = 13). ⋯ These findings are indicative of disturbed aerobic metabolism. We conclude that there is evidence of cyanide toxicity when nitroprusside is infused into patients using currently recommended doses. We recommend that for short infusions the dose of sodium nitroprusside should not exceed 0.5 mg/kg.
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Comparative Study
Maternal and neonatal effects of methoxyflurane, nitrous oxide and lumbar epidural anaesthesia for Caesarean section.
General anaesthetic techniques continue to be used for Caesarean section despite the possible increased incidence of foetal acidosis and neonatal depression. Two techniques of general anaesthesia (methoxyflurane-oxygen and nitrous oxide-oxygen) and lumbar epidural anaesthesia were compared in 37 patients under-going elective Caesarean section. ⋯ Cord blood gas analysis showed the babies in the methoxyflurane group to have a higher PaO2 with less metabolic acidosis than the babies from the other two groups. The maternal effects of the three anaesthetic techniques were similar, with only a small rise in serum fluroide levels noted in the methoxyflurane group.
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We have studied the effects of an inspiratory pause (PI) during artificial ventilation in 13 patients in acute respiratory insufficiency. The effects on gas exchange, haemodynamics and distribution of ventilation were observed. During the period of study the total volume, the inspiration/expiration ratio and the inspired oxygen concentration were all maintained constant. ⋯ The physiological dead space (VD/VT) was reduced in proportion to the duration of the inspiratory pause. These results suggest that the inspiratory pause triggers regional modification of the ventilation/perfusion ratio, favouring a reduction of the VD/VT ratio. However, this improvement of the VD/VT ratio does not seem to influence the oxygenation or the total distribution of ventilation in this type of patient.
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Randomized Controlled Trial Comparative Study Clinical Trial
Double-blind evaluation of buprenorphine hydrochloride for post-operative pain.
In a double-blind, random assignment study of four groups of 40 patients, relief of severe pain with buprenorphine hydrochloride 0.2 mg or 0.4 mg was evaluated and compared with morphine sulphate 5 or 10 mg. Evaluations included pain intensity, pain relief, sedation and other effects for up to 12 hours after drug administration, following recovery of wakefulness from anaesthesia for major abdominal surgery. Analyses of five parameters showed that the four groups were statistically comparable and that buprenorphine hydrochloride is at least 50 times more potent than morphine sulphate and has a substantially longer duration of analgesic action. Further clinical evaluation is, therefore, recommended.