Intrawmus arlhtinbtration ofctnetidine may occasionally cause profound hypotension. Cimetidine 200 mg was Ollhrinbtcred a bolus injection to patients whilst on cardiopulmonary bypass and subsequent changes in systemic arterial pressure were recorded. A statistically significant fall in arterial pressure was observed @ < 0.001). which was attributable to afall in systemic vascular resbrance. Key war&Surgery; cardiovascular. Hirtmlre; cknetidine.The histamine H,-receptor antagonist cimetidine has been observed to cause profound hypotension when given as an intravenous bolus to seriously ill patients.'-' Possible explanations for this include a negative inotropic effect,z an effect on vasomotor t one, ' -' and a negative chronotropic effects Routine observation in this hospital indicated patients receiving cimetidine whilst on cardiopulmonary bypass exhibited an apparently consistent fall in arterial pressure. Hsu et aL6 have pointed out that the patient on cardiopulmonary bypass behaves as a model of the isolated peripbmd circulation. They examined the effects of morphine on arteriolar and venocapacitana tone by m g perfusion pressure and the volume of blood in the pump reservoir respectively. This prompted the present study, in which the effbcts of cimetidine on arteriolar tone wen examined. Patients rod metbodsT h e investigation was limited to patients undergoing coronary artery bypass surgery. Patients were excluded if they were considered to be especially at risk from hypotension, i.e. those over 55 years old, those with preexisting hypertension (systemic diastolic pressure greater than 100 mmHg), and those with carotid bruits or other evidence of cerebrovascular insufficiency.The 14 patients included were those for whom cimetidine administration would normally be considered; that is, those with a history or symptoms of peptic ulcer or hiatus hernia, and those for whom intra-operative administration of steroids was indicated. A standard anaesthetic technique was employed, comprising diazepam, phenoperidine, pancuronium, nitrous oxide and oxygen. In addition, seven of the fourteen patients received

Intrawmus arlhtinbtration ofctnetidine may occasionally cause profound hypotension. Cimetidine 200 mg was Ollhrinbtcred a bolus injection to patients whilst on cardiopulmonary bypass and subsequent changes in systemic arterial pressure were recorded. A statistically significant fall in arterial pressure was observed @ < 0.001). which was attributable to afall in systemic vascular resbrance. Key war&Surgery; cardiovascular. Hirtmlre; cknetidine. A standard anaesthetic technique was employed, comprising diazepam, phenoperidine, pancuronium, nitrous oxide and oxygen. In addition, seven of the fourteen patients received

In 75 young female patients undergoing extraction of 3rd molar teeth during halothane or enflurane anaesthesia, the electrocardiogram was recorded on magnetic tape and analysed subsequently for arrhythmias, using a high-speed analyser. Enflurane induced a much lower frequency of arrhythmia during surgery than halothane, but there was otherwise little difference between the two drugs in the quality of anaesthesia or recovery. Many arrhythmias occurred before exposure of the patient to enflurane or halothane; the significance of this is discussed.