# Estimated End-Tidal Sevoflurane Concentration to Maintain Optimal Anesthetic Depth During Cardiopulmonary Bypass: A Meta-Analysis

## TL;DR

This study estimates the sevoflurane concentration needed to maintain proper anesthesia during heart surgery, finding that older patients require less of the drug.

## Contribution

The study provides a meta-analysis of sevoflurane requirements during cardiopulmonary bypass, identifying age as a key factor.

## Key findings

- The pooled end-tidal sevoflurane concentration during CPB was 0.88 vol%.
- Patients over 62 years old required 0.45 vol% less sevoflurane.
- Body temperature had no significant effect on sevoflurane requirements.

## Abstract

Background/Objectives: Volatile anesthetic dosing during cardiopulmonary bypass (CPB) is poorly standardized. We estimated the end-tidal sevoflurane (ETsevo) concentration required to maintain adequate anesthesia during CPB and investigated the effects of age and body temperature. Methods: This study is a PRISMA-compliant, PROSPERO-registered meta-analysis. PubMed, Embase, and the Cochrane Library were searched. Prospective studies of adults who underwent cardiac surgery with CPB and receiving sevoflurane were included. Primary outcome was mean ETsevo concentration when bispectral index (BIS) was 40–60. Three-level random-effects meta-analytic models with robust variance estimation were used to pool repeated measurements within studies. Age and body temperature were then examined as study-level moderators. Risk of bias was determined using ROBINS-I. Results: Five studies (n = 129) fulfilled the criteria. Pooled ETsevo during CPB was 0.88 vol% (95% confidence interval [CI] 0.29 to 1.46; p = 0.02) with substantial heterogeneity (I2 = 87.6%). Body temperature was not a significant moderator (difference 0.26 vol%; 95% CI −1.12 to 1.64; p = 0.27). Higher mean age was associated with lower ETsevo, evidenced by the finding that patients with a mean age of >62.0 years required 0.45 vol% less ETsevo (95% CI −0.78 to −0.13; p = 0.01), and sensitivity analysis revealed a 0.05 vol% decrease per additional year. Conclusions: To maintain BIS at 40–60 during CPB, the estimated ETsevo requirement is 0.88 vol% (minimum alveolar concentration 0.53–0.58 in patients in their 60s). Requirements decreased with age, and body temperature exerted no detectable effect.