Pupil Changes during Hypothermic Cardiopulmonary Bypass Under Fentanyl Anesthesia / 대한마취과학회지

ABSTRACT

BACKGROUND: Central nervous system dysfunction continues to be a major cause of morbidity after aorta and cardiac surgery under cardiopulmonary bypass (CPB). Pupillary reflexes are important component of the neurologic examination. The purpose of this study was to evaluate how the pupil reacts during hypothermic CPB under fentanyl anesthesia and its relation with postoperative neurologic deficits. METHODS: Fourteen patients undergoing ascending aortic dissection or aneurysm repair surgery under profound hypothermic CPB and circulatory arrest were enrolled. Pupil size and light reflex were evaluated at varying stages of CPB and temperatures. Temperatures were measured at different sites of perfusate, nasopharynx and rectum. Postoperatively neurologic assessments were performed to compare with the pupillary signs. RESULTS: Anesthetic induction with fentanyl decreased pupil size to pinpoint. Pupil dilated progressively under hypothermic CPB reaching fully dilated size at profound hypothermia. Rewarming returned the pupil to original size. Nasopharyngeal temperature correlated well with pupil size during cooling and rewarming. Light reflex was absent at any stage or temperature after anesthetic induction. Seven patients showed insignificant anisocoria and two died of other causes than neurologic deficit. One patient who was not in the anisocoria group exhibited delirium. CONCLUSIONS: Profound hypothermic CPB under fentanyl anesthesia dilates the pupil to a maximum size without light reflex overwhelming narcotic effect. Fully dilated pupil does not denote neurologic damage.