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

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 (>3 hours) 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 ± 4.3 L/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 60 minutes after surgery.

Time from turning off the vapourizer to extubation was 13.7 ± 2.5 minutes in the IHV group and 27.4 ± 6.5 minutes 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.