Metallized plastic sheeting (m.p.s.) was found to be ineffective in the prevention of hypothermia in adult patients studied during neurosurgical operations. Twenty patients were wrapped in m.p.s. and 22 patients acted as controls. Mean oesophageal temperature in the m.p.s. group decreased from 36.2 degrees C to 35.4 degrees C after 3 h (control 36.5 degrees C to 35.4 degrees C). It was concluded that active warming systems are needed to maintain normothermia in patients undergoing neurosurgical operations.

A number of recent papers have established that nitrous oxide, oxygen and halothane anaesthesia is accompanied by a high incidence of cardiac dysrhythmias when it is administered to outpatients for dental extractions. Rollason 8z Dundas 1 reported an incidence of 18 % in 202 patients, Thurlow2 24 % in 250 patients and Ryder3 34 % in 177 patients. The author's previous series which was monitored at the Royal DentalHospital2 showed that 34 % of children under 14 years anaesthetised solely with nitrous oxide, oxygen and halothane developed dysrhythmias but that adults who received an intravenous induction prior to maintenance with nitrous oxide, oxygen and halothane showed only a 10% incidence. This difference was attributed partly to the intravenous induction, with a consequent reduction in the amount of halothane needed and, partly to the fact that children had bilateral procedures more frequently and therefore there was a greater amount of intra-oral manipulation and temporary airway obstruction.The likely final common pathway of these dysrhythmias is beta stimulation of a myocardium already 'sensitised' by halothane4. The main evidence for this is twofold. First that the dysrhythmias can be prevented by beta blockerssl6 and secondly that the incidence of dysrhythmias using a purely intravenous technique without added halothane is very low 1 s 7. Shaft07 reported a series of 500 children successfully anaesthetised by continuous intravenous methohexitone but this method is sometimes technically difficult in young children and may carry some additional hazards899. It was therefore felt that many children would continue to be anaesthetised solely by nitrous oxide, oxygen and halothane and further investigation of this particular group would therefore be desirable. In order to determine the precise aetiology of the dysrhythmias, the investigation must be concentrated on those factors which might trigger the release of catecholamines. These include increased endogenous catecholamine secretion, which is especially likely in the highly nervous patient, surgical

SummaryWe report a case, of acute upper airway obstruction after tracheal extubation 24 hours after surgery. The respiratory complications of surgery for posterior fossa lesions are discussed.

SummaryFour cases of air embolism which occurred during neurosurgical procedures in the sitting position are described, in whom the signs could be due to air in the coronary or cerebral arteries. It is suggested that, during venous air embolism in the sitting position, a significant number of patients are haemodynarnically at risk from paradoxical air embolism, and that the serious consequences of venous air embolism in neurosurgery may be due to this.

A number of recent papers have established that nitrous oxide, oxygen and halothane anaesthesia is accompanied by a high incidence of cardiac dysrhythmias when it is administered to outpatients for dental extractions. Rollason 8z Dundas 1 reported an incidence of 18 % in 202 patients, Thurlow2 24 % in 250 patients and Ryder3 34 % in 177 patients.The author's previous series which was monitored at the Royal Dental Hospital2 showed that 34 % of children under 14 years anaesthetised solely with nitrous oxide, oxygen and halothane developed dysrhythmias but that adults who received an intravenous induction prior to maintenance with nitrous oxide, oxygen and halothane showed only a 10% incidence. This difference was attributed partly to the intravenous induction, with a consequent reduction in the amount of halothane needed and, partly to the fact that children had bilateral procedures more frequently and therefore there was a greater amount of intra-oral manipulation and temporary airway obstruction.The likely final common pathway of these dysrhythmias is beta stimulation of a myocardium already 'sensitised' by halothane4. The main evidence for this is twofold. First that the dysrhythmias can be prevented by beta blockerssl6 and secondly that the incidence of dysrhythmias using a purely intravenous technique without added halothane is very low 1 s 7. Shaft07 reported a series of 500 children successfully anaesthetised by continuous intravenous methohexitone but this method is sometimes technically difficult in young children and may carry some additional hazards899. It was therefore felt that many children would continue to be anaesthetised solely by nitrous oxide, oxygen and halothane and further investigation of this particular group would therefore be desirable. In order to determine the precise aetiology of the dysrhythmias, the investigation must be concentrated on those factors which might trigger the release of catecholamines. These include increased endogenous catecholamine secretion, which is especially likely in the highly nervous patient, surgical