Mild Hypercapnic Hyperventilation with the QED-100TM Attenuates Age-Related
K. Nakai1, H. Yoshida2, H. Hashimoto2, T. Kushikata2, K. Hirota2
Background: Mild hypercapnic hyperventilation significantly decreases emergence and recovery time from inhaled anesthesia in relatively younger patients (1-4). The effect of that in elderly patients has not yet been clarified. Therefore, we examined the age-related effect of mild hypercapnic hyperventilation on emergence from inhaled anesthesia.
Methods: We enrolled 28 patients aged 45-64 yrs and 28 patients aged over 65 yrs with ASA physical status I - II scheduled for elective ophthalmic surgery. Induction and maintenance of anesthesia were standardized with a protocol consisting of remifentanil, propofol, vecuronium, and 1.5% sevoflurane in air/O2. To develop mild hypercapnic hyperventilation, we used the QED-100TM (Anecare Laboratories, Inc.) according to previous reports (1, 3). Patients were randomly assigned to a control or QED-100 group for each age group. The minute ventilation in the QED-100 group was doubled during emergence. The QED-100 includes a re-breathing circuit to maintain hypercapnia, and a charcoal filter to absorb anesthetic vapor. In the control group, we left the minute ventilation unchanged. We recorded the following time from discontinuing sevoflurane to recovery, respiratory and hemodynamic parameters, BIS number, and complications after emergence.
Results: The times to adequate response, extubation and leaving the operating room were shorter in the QED-100 group (P<0.05). The decrease of time to adequate response in elderly patients, 41.5%, was larger than that in middle-aged patients, 27.5%. In the control group, the elderly patients required more time to each event than the middle-aged patients (P<0.05). Figure1 shows the linear regression analysis of time to adequate response and age. The QED-100 significantly deleted age-related changes in emergence time. During emergence the time-response, BIS curves were sigmoidal. The QED-100 shifted the sigmoid curve to the left in both the middle-aged and elderly groups. There were no statistically significant differences in hemodynamics or complications.
Discussion: Since all patients inhaled the same concentration of sevoflurane, emergence in the elderly patients was slower due to age-related decreases in MAC-awake. However, the QED-100 attenuated these age-related changes in recovery time and BIS. Mild hypercapnic hyperventilation may show increased benefit for elderly patients.