Isocapnic hyperventilation provides early extubation after head and neck surgery: A prospective randomized trial.

Abstract

Isocapnic hyperventilation (IHV) shortens recovery time after inhalation anaesthesia by increasing ventilation while maintaining a normal airway carbon dioxide (CO2)-level. One way of performing IHV is to infuse CO2 to the inspiratory limb of a breathing circuit during mechanical hyperventilation (HV). In a prospective randomized study, we compared this IHV technique to a standard emergence procedure (control). Thirty-one adult ASA I-III patients undergoing long-duration (>3hours) sevoflurane anaesthesia for major head and neck surgery were included and randomized to IHV-treatment (n=16) or control (n=15). IHV was performed at minute ventilation 13.6±4.3L/min and CO2 delivery, dosed according to a nomogram tested in a pilot study. Time to extubation and eye-opening was recorded. Inspired (FICO2) and expired (FETCO2) CO2 and arterial CO2 levels (PaCO2) were monitored. Cognition was tested preoperatively and at 20, 40 and 60minutes after surgery. Time from turning off the vapourizer to extubation was 13.7±2.5minutes in the IHV group and 27.4±6.5minutes in controls (P<.001). Two minutes after extubation, PaCO2 was 6.2±0.5 and 6.2±0.6 kPa in the IHV and control group respectively. In 69% (IHV) vs 53% (controls), post-operative cognition returned to pre-operative values within 40 minutes after surgery (NS). Incidences of pain and nausea/vomiting did not differ between groups. In this randomized trial comparing an IHV method with a standard weaning procedure, time to extubation was reduced with 50% in the IHV group. The described IHV method can be used to decrease emergence time from inhalation anaesthesia.