Slowing of the heart during hypotension in major abdominal surgery

Abstract

Heart rate (HR) and mean arterial blood pressure (MBP) were studied during abdomino-perineal resections of the rectum under neurolept anesthesia in order to observe HR deviations due to hypovolemic hypotension. Of the 65 patients followed, 18 developed a systolic BP under 100 mm Hg. Their blood loss (37 .+-. 9 ml/kg, mean .+-. s.e. mean) was higher than that of the normotensive control group (20 .+-. 2 ml/kg, P < 0.01), the urine production lower (8 .+-. 1 versus 10 .+-. 3 ml/kg, P < 0.01) and blood transfusions amounted to 40 .+-. 8 versus 24 .+-. 2 ml/kg (P < 0.01). In the hypotensive patients a decrease in MBP from 108 .+-. 3 to 94 .+-. 3 mm Hg was accompanied by a simultaneous increase in HR from 81 .+-. 3 to 91 .+-. 3 beats/ min (P < 0.05). However, during the hypotensive incident where the MBP averaged 69 .+-. 4 mm Hg, HR decreased temporarily to 75 .+-. 3 beats/min (P < 0.001). After MBP was restored to 94 .+-. 3 mm Hg using volume repletion, HR increased to 95 .+-. 3 beats/min (P < 0.001). The results demonstrated a temporary slowing of HR in anesthetized, bleeding and hypotensive patients.