Blood volume at the onset of hypotension during TURP performed under epidural anaesthesia

An analysis was made of the development of hypotension in the course of 60 transurethral resections of the prostate (TURP) performed under epidural anaesthesia. Hypotension was defined as a decrease in the systolic pressure down to 85 mmHg or less, or a total drop of 60 mmHg or more within 15 min. Indirect estimations of the blood volume according to the haemoglobin dilution method indicated that patients who developed hypotension from the epidural anaesthesia had a larger decrease in blood volume than other patients. During the operation, hypotension was associated with a blood volume of 300 ml or more below baseline, while 400 ml above baseline was required to ensure a stable circulation when the legs were lowered and removed from the stirrups after the TURP. Low central venous pressures, which were measured in 30 of the patients, were also associated with hypotension during and after TURP. There was a significant linear relationship between the total changes in blood volume and CVP measured at the end of each 10-min period of TURP (P < 0.001). However, no correlation between heart rate and hypotension was found.