CHANGES IN INTRACRANIAL-PRESSURE ASSOCIATED WITH APNEUMIC RETRACTORS

Objective: To investigate the effect of apneumic retraction on intracranial pressure (ICP) using a live porcine model. Design: Five 25- to 30-kg pigs had a fiber-optic ICP bolt inserted under general endotracheal anesthesia and were monitored for ICP, mean arterial pressure, arterial blood gas measurements, and intra-abdominal pressure before, during, and after pneumoperitoneum, with each period 30 minutes long. These series of measurements were repeated after artificially raising ICP with an epidural balloon to create a head-injured model. The mean (+/-SE) ICP in the noninjured model at baseline was 13.46+/-1.01 mm Hg; during pneumoperitoneum, 18.72+/-1.50 mm Hg (P=.0001). Similarly, in the head-injured model, ICP was raised artificially to a new baseline of 22+/-1.75 mm Hg with an epidural balloon, and pneumoperitoneum increased ICP to 27.40+/-0.93 mm Hg (P=.0001). Pneumoperitoneum was then released, and an apneumic retractor was inserted while maintaining the inflated epidural balloon. Main Outcome Measure: Changes in ICP. Results: Applying anterior wall retraction equivalent to 20 mm Hg was not associated with changes in ICP. These observations were independent of any changes in arterial PCO2 or arterial pH. Following the release of pneumoperitoneum, abdominal wall retraction, and epidural balloon, all measurements reverted to baseline. Conclusion: Pneumoperitoneum adversely affects ICP, while apneumic retraction may not affect animals with raised ICP. These findings suggest that pneumoperitoneum should be used with caution in patients with raised ICP, and apneumic retraction may be a safer alternative for laparoscopic evaluation in this population.