Effects of Different Types of General Anesthesia on Postoperative Pupillary Reactivity

Introduction: With the increased focus on early discharge after surgery and anesthesia, it is important to identify objective criteria that can be used to assess home-readiness after ambulatory surgery. Premature discharge may lead to a higher rate of patients suffering complications and to an increased readmission rate. Time-consuming objective evaluations of postoperative vigilance status like EEG registrations are not practicable in routine postoperative clinical practice.

In this study an approach to a more quantitative judgment of postoperative vigilance and consciousness is made by recording pupillometric measurements using a portable infrared pupillometer. The findings of this study may provide new important insights to the meaning of pupillary responses for postoperative vigilance measurement.

Aim: With regard to the lack of knowledge about mechanisms that enable the central nervous system to restore consciousness after the deep functional disorder of the anesthetized state, this study aims to compare general anesthesia techniques (volatile, intravenous) on postoperative changes in pupillary reactivity by using infrared pupillometry.

The primary aim of this study is to investigate changes in pupillary reactivity (pupillary light reflex (PLR, %) in the early postoperative phase (2 hours) after common used types of general anesthesia techniques (inhaled - sevoflurane versus intravenous - propofol).

Secondary aim is to examine whether decreased postoperative PLR predicts a decline in neuropsychological testing (alertness).

Hypotheses: The investigators hypothesis that changes in PLR within the first 2 postoperative hours differs depending on the anesthesia technique used, with a lower decline in PLR after propofol compared to sevoflurane anesthesia.

Furthermore, the investigators hypothesis that postoperative PLR correlates with changes in alertness measured by a neuropsychological test.

Design: This study will be a prospective, randomized double blinded study.

Methods: The study is approved by the local ethics committee and written informed consent will be obtained from each patient. A total of 108 patients aged ≥18 and ≤99 years, with American Society of Anesthesiologist (ASA) physical status scores I-II, scheduled for elective ENT surgery will be enrolled. Baseline assessment of pupillometry and neuropsychological test will be carried out before surgery (baseline) and at predefined time intervals during the first 2 postoperative hours after the end of anesthesia. Results (AUC, PLR%) will be compared between both anesthesia groups.

Primary outcome parameter will be the AUC of PLR (percentage change, %) measured every 15 minutes during the first 2 postoperative hours. Secondary outcome parameter will include the neuropsychological test score (Digit Symbol Substitution Test (DSST), the Visual Intrinsic Alertness Test (VIA) and the Trail making Test (TMT)) will be performed every 30 minutes after general anesthesia (sevoflurane, propofol maintained).), assessed every 30 min up to 2 hours after discontinuation of anesthesia.

• Alertness assessed with the Visual Intrinsic Alertness Test Score [Time frame: baseline and within the first 2 postoperative hours]
• Alertness assessed with the Trail making Test Score [Time frame: baseline and within the first 2 postoperative hours]
• Alertness assessed with the Digit Symbol Substitution Test [Time frame: baseline and within the first 2 postoperative hours]