Human cerebral circulation during deliberate hypotension and head-up tilt

¹ Department of Anesthesia, Schools of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, and Department of Anaesthetics, The Queen Victoria Hospital, East Grinstead, Sussex, England

Forty-two patients for elective surgical procedures were anesthetized with thiopental, nitrous oxide, and halothane and made hypotensive by ganglionic blockade with pentolinium, hexamethonium, trimethaphan, and/or guanethidine, combined with head-up body tilt, with or without positive airway pressure. In 23 patients, the systolic arterial pressure was at or below 70 mm Hg for an average of 42 min. In six patients, the systolic pressure was 50 mm Hg or below for an average of 39 min with an average head-up tilt of 24°. The lowest jugular bulb Po₂ recorded during hypotension was 27 mm Hg except in six instances when lower figures were recorded in the presence of increased airway pressure. Jugular bulb Po₂ was better correlated with Pa_COCO2 (r = 0.79) than with arterial pressure (r = 0.56). In the head-up position, jugular bulb pressures were usually above atmospheric pressure and were related to arterial carbon dioxide tension (r = 0.58). Cerebrovascular compensation appeared adequate under the conditions of deliberate hypotension as produced with this technique.

Submitted on March 4, 1963