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Changes in mesenteric blood flow during intracranial hypertension due to acute elevations in intra-abdominal pressure

Shmuel Avital, Samuel Szomstein, Oscar E Brasesco, Danny Rosin, Pablo Paolucci, Turab Pishori, Klaus Thaler, Ravindra Mailapur, Laurence Sands, Steven Wexner and Raul J Rosenthal

Elevated intra-abdominal pressure (IAP) has been associated with increased intracranial pressure (ICP) and diminished splanchnic blood flow. We investigated superior mesenteric artery flow and ICP following an increase in IAP. A flowmeter was placed on the superior mesenteric artery in five pigs and ICP was measured with an intraparenchymal bolt. IAP was elevated to 10 and 20 mmHg with nitrogen pneumoperitoneum. Changes in ICP, central venous pressure, mean arterial blood pressure and superior mesenteric artery blood flow were recorded at each level of IAP. Analysis of variants and paired t-test analyses were performed. ICP was increased and superior mesenteric artery flow decreased following IAP elevation. These changes were statistically significant when IAP was raised to 20 mmHg (ICP: p = 0.02; superior mesenteric artery flow: p = 0.006); central venous pressure was also increased. There was no significant change in mean arterial blood pressure and cerebral perfusion pressure. We have demonstrated a simultaneous effect of IAP on ICP (increase) and superior mesenteric artery blood flow (decrease). Further studies are warranted to evaluate the complete mechanism of these findings. In addition to direct transmission of pressures from the abdominal cavity, indirect effects of intra-abdominal hypertension may play a role in these documented changes.