[The level of analgesia and changes in heart rate during spinal anesthesia]

It is well known that high spinal anesthesia produces bradycardia. Studies are lacking, however, on the relation of changes in heart rate and the level of sympathetic blockade. Investigation was designed to elucidate the relationship between sympathetic blockade and heart rate during high spinal anesthesia. Subjects of the study were 70 rheumatoid arthritis patients who received spinal anesthesia with isobaric 0.5% bupivacaine. Cephalad spread of sympathetic blockade (loss of cold sensation to alcohol sponge) was determined at 30 minutes after injection of local anesthetics into the subarachnoid space. Heart rate was also measured before anesthesia and 30 minutes following spinal anesthesia. Heart rate was expressed by percent change. The results show that sympathetic blockade above T6 decreases heart rate more than 30%. In conclusion, sympathetic blockade above T6 by cold test produces 30% decrease in heart rate and this means that cardiac sympathetic denervation is almost complete at this level.