EFFECTS OF INCREASED INTRAABDOMINAL PRESSURE UPON INTRACRANIAL AND CEREBRAL PERFUSION-PRESSURE BEFORE AND AFTER VOLUME EXPANSION

Objective: To study the effects of elevated intra-abdominal pressure ( IAP) upon intracranial (ICP) and cerebral perfusion pressure (CPP) bef ore and after intravascular volume resuscitation. Materials and Method s: Intra-abdominal pressure was increased in five anesthetized swine b y inflating an intraperitoneal balloon until the IAP was 25 mm Hg abov e baseline, Intravascular volume was then expanded and finally abdomin al decompression was performed. Changes in ICP and systemic and pulmon ary hemodynamic parameters secondary to increasing IAP were measured, The effect upon CPP was derived from these measurements. PaO2 and PaCO 2 were maintained relatively constant by increasing ventilatory rate. Measurements and Main Results: Elevated IAP significantly increased IC P (7.6 +/- 1.2 vs, 21.4 +/- 1.0), pleural pressure and central venous pressure; whereas cardiac index and CPP (82.2 +/- 6.3 vs, 62.0 +/- 10. 0) decreased significantly, Intravascular volume expansion further sig nificantly increased ICP (27.8 +/- 1.0), and significantly increased b oth mean arterial pressure (83.4 +/- 14.0 versus 103.4 +/- 8.9) and CP P (75.6 +/- 9.0). Abdominal decompression returned ICP (11.2 +/- 1.8) toward baseline and further increased CPP (79.8 +/- 9.7). Conclusions: Elevated IAP increases ICP and decreases CPP and cardiac index, Volum e expansion further increases ICP yet improves CPP via its greater pos itive effect upon mean arterial pressure (p < analysis of variance, A ll measurements are mean +/- SEM in mm Hg).