[Time course of epidural pressure change under intraperitoneal insufflation during laparoscopic surgery]

The effect of intraperitoneal insufflation on epidural pressure (EPP) was studied in 10 patients undergoing laparoscopic cholecystectomy under general anesthesia. Epidural puncture was performed at T8/9 interspace. After placing an epidural catheter, EPP was recorded continuously using a pressure transducer. Ventilation was controlled to maintain PETCO2 at 30-35 mmHg. Intraperitoneal pressure was maintained at 8-12 mmHg by using CO2 gas insufflator. During EPP measurements, the patients were supine on a horizontal operating table and zero point was referred to the level of the external auditory meatus. ECG and direct BP were also monitored. Before anesthetic induction, the mean EPP was 15.5 +/- 2.0 mmHg. During the mechanical ventilation, EPP recordings showed two types of periodic waves: large and small. The large waves were observed in phase of positive pressure ventilation, and the small waves were synchronous with arterial pulsations. Intraperitoneal insufflation produced an immediate increase in EPP (19.8 +/- 4.2 mmHg after 1 min, 22.8 +/- 5.8 mmHg after 5 min). An immediate decrease in EPP to the baseline level was observed just after the release of intraperitoneal pressure. The results suggest that 1) EPP is positive and fluctuates with ventilation and arterial pulsations, 2) intraperitoneum insufflation produces an increase in EPP that lasts until the procedure is discontinued, and 3) increased intrathoracic and intraperitoneal pressures play a predominant role in producing the elevation of EPP.