THE ANAESTHETIC ADMINISTRATION Of 14C labelled halothane has been shown to cause non-volatile halothane metabolites to accumulate in the liver of mice) These labelled halothane metabolites are bound to liver microsomes in proportion to liver blood flow, hepatic arterial oxygen tension and enzyme induction? Cohen 3 showed that repeated weekly injections of labelled halothane caused non-volatile metabofires to accumulate and increase in the liver suggesting stimulation of enzyme induction. In contrast, Topham and Longshaw 4 showed that repeated daily inhalations of labelled halothane produced no accumulation of non-volatile metabolites using whole body auto-radiography techniques. Stevens and co-workers 5 reported that constant subanaesthetic inhalations of halothane for 35 days caused reproducible dose dependent liver toxicity. This could be related to Sawyer's 6 work which showed optimum halothane metabolism at 1/100 MAC. It was hypothesized that increasing halothane concentrations depressed the necessary enzyme systems for halothane metabolism and that optimum metabolism may only be present in the post-anaesthetic period.In an attempt to clarify the divergent results of other workers, our study measured metabolism of halothane with chronic repeated exposures, determined the specific site of metabolism and assessed possible hepatotoxicity by light and electron microscopy. METHODS

Hypertension following coronary surgery is generally reported at an alarmingly high incidence (35-40 per cent). A vigilant program carried out in 1977 at Montreal Heart Institute disclosed a low incidence of 3.5 per cent in 200 consecutive unselected cases. A similar programme in 1980 based on 100 patients showed an incidence of 23 per cent. This highly significant difference is felt to be related to the different anaesthetic management that has occurred since 1977. Anaesthesia for all the 200 patients was primarily morphine 1.0-1.5 mg. kg-t. The 1980 group when divided according to the main anaesthetic agent used, with 40 patients in each group, yields the following incidence of postoperative hypertension: Morphine 4 per cent Fentanyl 20 per cent Halogenated Agents 37.5 per cent We conclude that early return of sympathetic activity is likely to increase the incidence of post-operative hypertension following coronary artery surgery; hence, early awakening following this type of surgery is not in the best interest of the patient.

The question of whether colloids are better than crystalloid solutions for resuscitation of hypovolemic patients remains to be answered.The purpose of this study was to investigate how the closing lung volume is affected by a reduction of colloid oncotic pressure.We measured closing lung volumes of anesthetized dogs in the presence of undisturbed serum proteins (COP= 18.9–22.1 mmHg). Following these determinations, we reduced the colloid oncotic pressure to 10.9–12.9 mmHg by administration of 50 ml/kg of 5% dextrose solution. Closing lung volumes were evaluated repeatedly from 10 to 90 minutes following the completion of infusion.

Diazepam is a commonly used drug for suicidal attempts. The antagonistic effect of physostigmine in these patients is poorly understood.We studied the interaction of large doses of diazepam and either physostigmine or galanthamine hydrobromide using dose-response curves in 21 cats. After establishing dose-response curves for diazepam, half of the animals received 0.02 mg/kg of physostigmine intravenously. Two minutes later 8, 10, 12, or 14 mg/kg of diazepam was administered intravenously. After 2, 5, and 10 min, animals were evaluated for their response to noise and pain stimuli. The other half of animals were given 0.2 mg/kg of galanthamine intravenously and evaluated for diazepam effect using the same criteria. Sufficient number of days were allowed for the animals to recover from diazepam.