Evaluation of mechanism of increased intracranial pressure with insufflation.

BACKGROUND: Previous studies have documented an increase in intracranial pressure with abdominal insufflation, but the mechanism has not been explained.

METHODS: Nine 30-35-kg domestic pigs underwent carbon dioxide insufflation at 1.5 l/min. Intracranial pressure (ICP), lumbar spinal pressure (LP), central venous pressure (CVP), inferior vena cava pressure (IVCP), heart rate, systemic arterial blood pressure, pulmonary arterial pressure, cardiac output, heart rate, respiratory rate, temperature, and end-tidal CO2 were continuously measured. Mechanical ventilation was used to maintain a constant pCO2. Measurements were recorded at 0, 5, 10, and 15 mmHg of abdominal pressure with animals in supine, Trendelenburg (T), and reverse Trendelenburg (RT) positions. Prior to recording measurements, the animals were allowed to stabilize for 40 min after each increase in abdominal pressure and for 20 min after each position change.

RESULTS: The animals showed a significant increase 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 the increase in ICP. The IVCP (mmHg) increased with increased abdominal pressure (0 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 pressures >/=0.95). There was no significant change in CVP.

CONCLUSIONS: This study suggests that care may be needed with laparoscopy in patients at risk for increased ICP due to head injury or a space occupying lesion. The mechanism of increased ICP associated with 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 underway to confirm this hypothesis.