TIME-DEPENDENT CHANGES IN HEART-RATE AND PUPIL SIZE DURING DESFLURANEOR SEVOFLURANE ANESTHESIA

To better characterize alterations in autonomic function associated wi th prolonged anesthesia, we tested the hypothesis that the time-depend ent effects of sevoflurane and desflurane differ. We studied seven mal e volunteers, each anesthetized for 8 h with 1.25 minimum alveolar ane sthetic concentration desflurane on one study day and with 8 h sevoflu rane on another. These volunteers did not undergo surgery and were min imally stimulated during the study. Measurements included blood pressu re, heart rate, pupillary size and light reactivity, concentrations of serum catecholamines, and carbon dioxide production. Over time, heart rate and pupil size increased significantly. During 6 of the 14 anest hetics (45%), heart rate at some point exceeded 95 bpm; similarly, pup il size at some time exceeded 5 mm during 8 anesthetics (57%). In cont rast, plasma catecholamine concentrations and carbon dioxide productio n remained unchanged, and blood pressure remained nearly constant. The re are thus substantial time-dependent changes in autonomic functions during prolonged anesthesia, even in unstimulated, nonsurgical volunte ers, but we could not detect a difference in these changes during desf lurane compared with sevoflurane anesthesia. Implications: Pupil size and heart rate changes are used to guide the delivery of anesthesia. I n volunteers, pupil size and heart rate increased with increasing dura tion of constant desflurane or sevoflurane anesthesia. Thus, anestheti c duration alters heart rate and pupil size independent of surgery and changes in anesthetic delivery.