The role of Cushing's reflex and the vasopressin-mediated oligoanuric response to intracranial hypertension in patients with abdominal compartment syndrome.

Background: We examined the link between increased intra-abdominal pressure, intracranial pressure, and vasopressin release as a potential mechanism. Intra-abdominal pressure, produced by abdominal-cavity insufflation with carbon dioxide (CO) during laparoscopic abdominal procedures to facilitate visualization, is associated with various complications, including arterial hypertension and oliguria.

Methods: Mean arterial pressure, optic nerve sheath diameter, measured as a proxy for intracranial pressure, plasma vasopressin, serum and urine osmolarity, and urine output were measured 4 times during laparoscopic sleeve gastrectomy in 42 patients: before insufflation with CO (T); after insufflation to 15 cm water (HO) pressure, with 5 cm HO positive end-expiratory pressure (T); after positive end-expiratory pressure was raised to 10 cm HO (T); and after a return to the baseline state (T). Mean values at T to T and the directional consistency of changes (increase/decrease/ unchanged) were compared among the 4 data-collection points.

Results: Statistically significant elevations (all P ≤ .001) were noted from T to T and from T to T in mean arterial pressure, optic nerve sheath diameter, and vasopressin, followed by decreases at T. For optic nerve sheath diameter and vasopressin, the increases at T and T occurred in 98% and 100% of patients, ultimately exceeding normal levels in 88 and 97%, respectively. Conversely, urine output fell from T to T and T by 60.9 and 73.4%, decreasing in 88.1% of patients (all P < .001). Patients with class II obesity exhibited statistically greater increases in optic nerve sheath diameter and vasopressin, but statistically less impact on urine output, than patients with class III obesity.

Conclusion: Increased mean arterial pressure, intracranial pressure, and vasopressin release appear to be intermediary steps between increased intra-abdominal pressure and oliguria. Further research is necessary to determine any causative links between these physiological changes.