Consumption of isoflurane and recovery time in low-flow anaesthesia versus high-flow anaesthesia

To compare the effects of low-flow versus high-flow Isoflurane anesthesia on volatile anesthetic consumption, recovery characteristics, postoperative inflammatory response, and patient clinical outcomes in elective laparoscopic cholecystectomy.

This quasi-experimental study was conducted at Department of Anesthesia, Combined Military Hospital, Malir Cantt, Karachi, Pakistan from October 2022-March 2023. A total of 280 consecutive eligible patients fulfilling the inclusion criteria were recruited using non-probability convenience sampling and assigned into Group-A (Low-flow anesthesia) (n=140) and Group-B (High-flow anesthesia) (n=140). Primary variables were the mean intraoperative isoflurane consumption, and the neutrophil-to-lymphocyte ratio (NLR) at 24 hours postoperatively. Secondary variables were patient outcomes and anesthesia adverse effect profile.

Mean isoflurane consumption was significantly lower in Group-A at 12.04 ± 3.00 mL, compared with 16.18 ± 3.79 mL in Group-B (p<0.001). Median baseline NLR values were nearly the same: 2.27 (0.87) in Group-A and 2.30 (0.89) in Group-B (p=0.972). However, postoperative NLR at 24 hours showed a clear rise in Group-B, recorded as 4.46 (2.01), compared with 3.45 (1.54) in Group-A (p<0.001). Low-flow anesthesia was associated with shorter time to extubation while time to Aldrete score ≥ 9, postoperative pain score, rescue analgesia requirements, postoperative nausea and vomiting, shivering, hypothermia, delayed emergence, dizziness and HDU admissions were comparable between groups.

The study supports low flow anaesthesia as an effective technique that reduces anesthetic use, shortens the extubation time and attenuated the postoperative inflammatory response without increasing perioperative adverse events related to anesthesia or delaying recovery.