The effects of propofol, methohexitone and isoflurane on the baroreceptor reflex in the cat.

The effects of propofol (P), methohexitone (M) and isoflurane (I) on the baroreceptor reflex were studied in a cat model in which the blood pressure in a bilateral isolated carotid sinus preparation was artificially varied between 50-200 mmHg. The influence from aortic and cardiopulmonary baroreceptors was excluded by vagotomy. With basal chloralose anaesthesia as control, the investigated anaesthetics were used in doses corresponding to MAC 0.5 and 1.0. The maximum change in systemic mean arterial pressure (MAP) and heart rate (HR) following a defined increase in carotid sinus pressure was used as an index of baroreceptor reflex sensitivity. Compared to control, M and I anaesthesia were associated with significant depression of baroreceptor reflex sensitivity at the high dose (corresponding to MAC 1.0), and during I anaesthesia also at the low dose (MAC 0.5). The baroreceptor reflex sensitivity was maintained during propofol anaesthesia. The carotid sinus pressure interval at which the maximum changes in MAP could be elicited, was significantly higher during M than during P. This indicates resetting of the baroreflex.