# Randomized, Single-Blind Comparison of Two Different Flow Rates of Sevoflurane Anesthesia on Acute Kidney Injury

## TL;DR

This study compares two flow rates of sevoflurane anesthesia and finds both are safe with no acute kidney injury.

## Contribution

The study provides new clinical evidence on the safety of low-flow sevoflurane anesthesia for kidney function.

## Key findings

- No cases of acute kidney injury were observed in either flow rate group.
- Urinary microalbumin levels increased temporarily but returned to near baseline within 48 hours.
- Only one patient had a slightly elevated albumin-to-creatinine ratio, which was not clinically significant.

## Abstract

Background: Prolonged sevoflurane-based low-flow anaesthesia (LFA) is often not advised for clinical use due to acute kidney injury (AKI) risk. However, LFA has multitudes of advantages, and surveys on anesthesia practice indicate that the use of LFA, even with sevoflurane, is on the rise. Literature on human studies is growing, but the recommendations for LFA have not changed, indicating the need for further evaluation. We aimed to evaluate the incidence of AKI with sevoflurane-based LFA with two different FGFs.

Methods: The current prospective, randomized, single-blind, parallel-arm study was conducted using sevoflurane-based LFA with two FGFs: group A (1000mL/min) and group B (600mL/min) with a targeted age-adjusted minimum alveolar concentration (MACage) of 1-1.2 enrolling adult participants undergoing elective surgeries of at least 120-minute anesthesia duration. Anesthesia management was standardized, and AKI classification was performed based on Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. Further, spot urinary microalbumin, sodium (Na), potassium (K), protein, and spot albumin creatinine ratio (sACR) were evaluated and compared. A two-tailed p-value <0.05 was considered statistically significant.

Results: Data from 65 (33 in the 1000mL and 32 in the 600mL group) were evaluated. No AKI was noted in either group. The anesthesia duration ranged from 120 to 780 minutes (median 200, interquartile range 260-180, with mean 230.9, and 95% confidence 202.5-259.3 minutes). Spot urine microalbumin was significantly higher at two to four hours postoperatively than at the preoperative level, but the rise was similar in both groups. By 24 hours, the level declined significantly and remained at a slightly higher level than the preoperative value, which further reduced to a somewhat lower level than the preoperative value by 48 hours. Only one patient in the 1000mL/min group had sACR >66.7 μg/mg.

Conclusion: Sevoflurane-based LFA with an FGF of 600mL/min is safe and comparable to the FGF of 1000mL/min for surgeries. Transient urinary microalbumin and sACR changes occur, which settle within 24 to 48 hours; no impact on urine output and AKI was noted.