Increased haemodilution in hypotension induced by epidural anaesthesia

This study examined whether the increased haemodilution from fluid loading in patients who develop hypotension at the onset of epidural anaesthesia (EDA) can be explained by high-level blockade or by stress-induced elevation of the blood glucose concentration. In 20 men aged between 53 and 87, crystalloid volume loading was carried out with 10 ml.kg-1 b.w. and EDA was induced with mepivacaine 2% and adrenaline 1:200,000. Irrespective of the blood pressure reaction to the blockade, there was no change in blood glucose level. A strong linear correlation between haemodilution and arterial pressure was found, in spite of unchanged blood glucose levels, in 10 patients in whom EDA was induced with bupivacaine 0.5%, and in 10 patients who received spinal anaesthesia with tetracaine 1%. There was no correlation between the haemodilution and the extent of sensory analgesia. These results support the view that low arterial pressure alone triggers the increased haemodilution observed during EDA-induced hypotension.