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

Abstract

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 (CO₂) during laparoscopic abdominal procedures to facilitate visualization, is associated with various complications, including arterial hypertension and oliguria. 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 CO₂ (T₀); after insufflation to 15 cm water (H₂O) pressure, with 5 cm H₂O positive end-expiratory pressure (T₁); after positive end-expiratory pressure was raised to 10 cm H₂O (T₂); and after a return to the baseline state (T₃). Mean values at T₀ to T₃ and the directional consistency of changes (increase/decrease/ unchanged) were compared among the 4 data-collection points. Statistically significant elevations (all P ≤ .001) were noted from T₀ to T₁ and from T₀ to T₂ in mean arterial pressure, optic nerve sheath diameter, and vasopressin, followed by decreases at T₃. For optic nerve sheath diameter and vasopressin, the increases at T₁ and T₂ occurred in 98% and 100% of patients, ultimately exceeding normal levels in 88 and 97%, respectively. Conversely, urine output fell from T₀ to T₁ and T₂ 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. 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.