CHANGES IN BLOOD-VOLUME DISTRIBUTION BETWEEN LEGS AND TRUNK DURING HALOTHANE ANESTHESIA

To assess the influence of halothane anaesthesia on the distribution o f blood volume in supine humans, we used albumin labelled with Tc-99m to measure blood volume distribution along the craniocaudal axis. We s tudied 6 volunteers in the supine position before, during and after an aesthesia with 1% halothane and 66% nitrous oxide. Using collimated de tectors above and below the subject, counts were obtained from the leg s, pelvis, abdomen, rib cage and head, with the arms excluded. During anaesthesia, the proportion of counts detected in the legs increased, but failed to achieve significance (P = 0.059). On recovery from anaes thesia, leg counts decreased significantly. Counts in the abdomen and rib cage decreased significantly during anaesthesia and the abdomen co unts increased again on recovery (P = 0.036 for all changes). These re sults confirm other studies of the vascular effects of halothane, and do not support the hypothesis that blood volume redistributes from the legs to within the chest wall during anaesthesia.