EVALUATION OF MECHANISM OF INCREASED INTRACRANIAL-PRESSURE WITH INSUFFLATION

Background: Previous studies have documented an increase in intracrani al pressure with abdominal insufflation, but the mechanism has not bee n explained. Methods: Nine 30-35-kg domestic pigs underwent carbon dio xide insufflation at 1.5 l/min. Intracranial pressure (ICP), lumbar sp inal pressure (LF), central venous pressure (CVP), inferior vena cava pressure (IVCP), heart rate, systemic arterial blood pressure, pulmona ry arterial pressure, cardiac output, heart rate, respiratory rate, te mperature, and end-tidal CO2 were continuously measured, mechanical ve ntilation was used to maintain a constant pCO(2). Measurements were re corded at 0, 5, 10, and 15 mmHg of abdominal pressure with animals in supine, Trendelenburg (T), and reverse Trendelenburg (RT) positions, P rior to recording measurements, the animals were allowed to stabilize for 40 min after each increase in abdominal pressure and for 20 min af ter each position change. Results: The animals showed a significant in crease in ICP (mmHg) with each 5-mmHg increase in abdominal pressure ( 0 mmHg: 14 +/- 1.7; 5 mmHg: 19.8 +/- 2.3, p < 0.001; 10 mmHg: 24.8 +/- 2.5, p < 0.001; 15 mmHg: 29.8 +/- 4.7, p < 0.01). The ICP at 15 mmHg abdominal pressure increased further in the T position (39 +/- 4, p < 0.01). Insufflating in the RT position did not significantly reduce th e increase in ICP. The IVCP (mmHg) increased with increased abdominal pressure 10 mmHg: 11.5 +/- 6.2, 15 mmHg: 22.1 +/- 3.5, p < 0.01). This increase correlated with the increase in ICP and LP (r of mean pressu res greater than or equal to 0.95). There was no significant change in CVP. Conclusions: This study suggests that care may be needed with la paroscopy in patients at risk for increased ICP due to head injury or a space occupying lesion. The mechanism of increased ICP associated wi th insufflation is most likely impaired venous drainage of the lumbar venous plexus at increased intraabdominal pressure. Further studies of cerebral spinal fluid movement during insufflation are currently unde rway to confirm this hypothesis.