[Baroreflex activity in carotid endarterectomy during general anesthesia].

The baroreceptor reflex was studied in eleven patients, aged 69 +/- 6 years, scheduled for carotid endarterectomy under general anaesthesia. Nine were hypertensive. The anaesthetic protocol was the same for all the patients: premedication with morphine and scopolamine, induction with 5 mg.kg-1 thiopentone, 6 micrograms.kg-1 fentanyl and 0.01 mg.kg-1 pancuronium bromide. All the patients were intubated and ventilated with a mixture of nitrous oxide and oxygen. Fentanyl, 100 micrograms, was routinely given at the time of incision. Baroreflex sensitivity was tested using Smyth's method, with a bolus of 75 micrograms trinitrin and plotting changes in heart rate against those in systolic blood pressure. Electrocardiogram, invasive arterial blood pressure and airway pressure were simultaneously recorded. PaCO2 and PaO2 were measured during arterial clamping. The tests were carried out before clamping, 2 min later and 10 to 20 min after the last injection of fentanyl. In the seven patients for whom clamping lasted more than 15 min, a further test was carried out after administration of 0.4 +/- 0.05 vol% halothane (Datex analyser) for 5 min. During anaesthesia, baroreflex sensitivity was low (1.8 +/- 0.3 ms.mmHg-1). After clamping, there was only a significant change in Pasys, with no changes in heart rate or blood gas values (129 +/- 8 mmHg before clamping; 167 +/- 12 mmHg after clamping; n = 8; p less than 0.01). After halothane administration, the sensitivity slope decreased, but not significantly. Moreover, halothane decreased the R-R intervals (1140 +/- 84 after clamping; 963 +/- 76 under halothane; n = 6; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)