Droperidol elimination after cardiopulmonary bypass surgery.

A high-dose (0.75 to 2.8 mg/kg) pharmacokinetic study of droperidol was undertaken in patients during the recovery phase after cardiac surgery involving hypothermic cardiopulmonary bypass (CPB). The elimination half-life of droperidol in these patients, determined from concentration-time data obtained after CPB, was significantly prolonged relative to previously reported mean values in younger surgical patients not undergoing CPB and receiving lower doses of the drug (0.05-0.20 mg/kg). On stratification of the patients by droperidol dose, there was an inverse correlation between the size of the dose and the elimination half-life of droperidol: mean half-life decreased as mean dose increased. This difference in elimination half-life was not related to the duration of the CPB procedure, or the total anesthetic time, both of which were not significantly different between the patient groups receiving the three different doses of droperidol. The magnitude or duration of hypothermia after CPB did not differ between the three patient groups. The differences in half-lives are more likely due to the clinical condition of the patients, such that the patients who received the higher doses of droperidol were also judged clinically to be less ill and thus eliminated droperidol more efficiently. This hypothesis, however, could not be supported due to the small number of patients studied. The results obtained in this study indicate that droperidol elimination is significantly prolonged after high-dose administration to elderly patients undergoing hypothermic CPB procedures during cardiac surgery.

Responses of the dural circulation to electrical stimulation of the trigeminal ganglion in the cat.

1. In cats anaesthetized with alpha-chloralose, electrical stimulation (ES) of the trigeminal ganglion produced a fall in blood pressure, a predominantly ipsilateral dilatation in the common carotid vascular bed and bilateral dilatation of the middle meningeal vascular bed. Section of the trigeminal root abolished these responses. 2. Dilatation in the middle meningeal artery was not affected by section of the cervical sympathetic trunk nor by the section of the seventh cranial nerve trunk. The dilator response was abolished by section of the spinal cord at the C3 level and by intravenous administration of bretylium (10 mg/kg) or phentolamine (5 mg/kg). The response was significantly reduced by the prior administration of papaverine (10 mg/kg). 3. Functional adrenalectomy by means of a snare placed around the nerves and blood vessels supplying the adrenal glands significantly reduced the response. Electrical stimulation of the trigeminal ganglion was accompanied by a fall in circulating levels of noradrenaline and serotonin. 4. We conclude that ES of the trigeminal ganglion produces dilatation in the middle meningeal artery partly by autoregulation during the trigeminal depressor response and partly by a reduction in the circulating levels of noradrenaline. It differs from the dilatation seen in the general carotid circulation and the cortical microcirculation, which is mediated by parasympathetic nerves. There is no evidence that antidromic release of neuropeptides from sensory nerve endings in the dura plays a part in the dilatation.