The Effect of Pressure-controlled Ventilation-volume Guaranteed Mode

Overview

The anesthetized patient is turned to the prone position during lumbar spine surgery. The dynamic compliance of lung usually decreases and peak airway pressure increases during the surgery. A new ventilation mode, pressure-controlled ventilation with volume guaranteed mode (PCV-VG) has been recently introduced. The ventilator compares the tidal volume of the previous breath and automatically regulates the pressure up or down to achieve the set tidal volume. This prospective, randomized study is designed to compare the effect of PCV-VG and volume-controlled ventilation (VCV) on peak airway pressure, lung compliance and hemodynamic variables.

1. Total 34 patients with American Society of Anesthesiologists physical status I-III who underwent lumbar spine surgery in prone position were enrolled. 2. All patients fasted for 8 hours before the surgery and were premedicated with intramuscular glycopyrrolate 0.2 mg. Anesthesia was induced with remifentanil (0.1-0.2 ug/kg/min), propofol (1.5-2 mg/kg) and rocuronium (0.6 mg.kg) and maintained with sevoflurane (2.0-2.5 vol%) in inspired oxygen fraction with 0.5, remifentanil (0.05-0.3 ug/kg/min) and vecuronium (0.03-0.05 mg/kg/hr). 3. A 20 G catheter was inserted into the radial artery to monitor continuous arterial pressure and hemodynamic variables (cardiac output, cardiac index, stroke volume, stroke volume index, and stroke volume variation) monitoring. 4. All patients were ventilated with a Datex-Ohmeda Ventilator (S/5 AVANCE). Patients were randomized to receive either PCV-VG (n=17) or VCV (n=17) mode. The tidal volume in both group were set to deliver 8 mL/kg of ideal body weight. The respiratory rate (RR) was adjust to maintain end tidal CO2 (ETCO2) 33-38 mmHg. 5. Hemodynamic variables (mean blood pressure, heart rate, cardiac output, cardiac index, stroke volume, stroke volume index, and stroke volume variation) , respiratory variables (saturation, RR, ETCO2, peak airway pressure, mean airway pressure and lung dynamic compliance) and arterial gas analyses were recorded at 4 stages: (1) 15 minutes after induction in supine position, (2) 30 minutes after turning the patient to the prone position, (3) 60 minutes after turning the patient to the prone position, (4) 15 minutes after turning the patient to supine position at the end of surgery.