Evaluation of a method for isocapnic hyperventilation: a clinical pilot trial. Issue 2 (16th October 2017)

• Record Type: Journal Article
• Authors: Hallén, K.; Jildenstål, P.; Stenqvist, O.; Ricksten, S.‐E.; Lindgren, S.
• Is Part Of: Acta anaesthesiologica scandinavica. Volume 62:Issue 2(2018:Feb.)
• Page Start: 186
• Page End: 195
• Publication Date: 2017-10-16
• Subjects: Anesthesiology -- Periodicals; Critical care medicine -- Periodicals; 617.9605
• DOI: 10.1111/aas.13008
• Languages: English
• ISSNs: 0001-5172

Abstract

Abstract : Background: Isocapnic hyperventilation (IHV) is a method that shortens time to extubation after inhalation anaesthesia using hyperventilation (HV) without lowering airway CO2 . In a clinical trial on patients undergoing long‐duration sevoflurane anaesthesia for major ear–nose–throat (ENT) surgery, we evaluated the utility of a technique for CO2 delivery (DCO2 ) to the inspiratory limb of a closed breathing circuit, during HV, to achieve isocapnia. Methods: Fifteen adult ASA 1–3 patients were included. After end of surgery, mechanical HV was started by doubling baseline minute ventilation. Simultaneously, CO2 was delivered and dosed using a nomogram developed in a previous experimental study. Time to extubation and eye opening was recorded. Inspired (FICO2 ) and expired (FETCO2 ) CO2 and arterial CO2 levels were monitored during IHV. Cognition was tested pre‐operatively and at 20, 40 and 60 min after surgery. Results: A DCO2 of 285 ± 45 ml/min provided stable isocapnia during HV (13.5 ± 4.1 l/min). The corresponding FICO2 level was 3.0 ± 0.3%. Time from turning off the vaporizer (1.3 ± 0.1 MACage) to extubation (0.2 ± 0.1 MACage) was 11.3 ± 1.8 min after 342 ± 131 min of anaesthesia. PaCO2 and FETCO2 remained at normal levels during and after IHV. In 85% of the patients, post‐operative cognition returned to pre‐operative values within 60 min. Conclusions: In this cohort of patients, a DCO2 nomogram for IHV was validated. The patients were safely extubated shortly after discontinuing long‐term sevoflurane anaesthesia. Perioperatively, there were no adverse effects on arterial blood gases or post‐operative cognition. This technique for IHV can potentially be used to decrease emergence time from inhalation anaesthesia.