Effects of graded suppression of the EEG with propofol on the neurologicaloutcome following incomplete cerebral ischaemia in rats

We evaluated the relation between dose and response for the neuroprotective effect of propofol in a rat model with incomplete cerebral ischaemia. For clarification of the mechanism of neuroprotection, plasma catecholamines an d tumour necrosis factor-alpha levels were measured. Three doses (low, mode rate and high-dose) of propofol were tested. These produced, respectively, a low amplitude, slowing and a burst-suppression pattern of electroencephal ographic activity. Incomplete cerebral ischaemia was produced by right caro tid artery occlusion combined with haemorrhagic hypotension (35 mmHg) for 3 0 min. Neurological outcome at 72 h post-ischaemia in the high-dose group w as significantly better than that in both low-dose and moderate-dose groups . Propofol exhibited a trend in the dose-related attenuation of the increas es in plasma adrenaline and noradrenaline during ischaemia. Tumour necrosis factor-alpha increased during and after ischaemia in all groups with no in tergroup differences. The results indicate that a burst-suppression dose of propofol provides neuroprotection. The protective effect can not be comple tely explained by the attenuating effect on circulating catecholamines.