Differential effects of isotonic and hypotonic 4% albumin solution on intracranial pressure and renal perfusion and function

Objectives: Albumin is used to resuscitate trauma patients but may increase intracranial pressure (ICP). Its effects on renal blood flow and function are unknown. Our aim was to examine the effects of hypertonic albumin on ICP and renal function, and if any effects are due to the hypotonicity of the solution containing albumin or to albumin itself. Design, setting and subjects: Cross-over, randomised controlled experimental study of six adult Merino ewes in the animal facility of a research institute. Method: Sheep were implanted with flow probes around the pulmonary and renal arteries and an ICP monitoring catheter in a lateral cerebral ventricle. Conscious sheep received normal saline, commercially available hypotonic 4% albumin solution (4% Albumex [278 mOsm/kg]) or a novel isotonic 4% albumin solution (288 mOsm/kg), with at least 48 hours between each intervention. Results: Commercial hypotonic albumin solution increased ICP (by 8.5 mmHg [SEM, 2.1 mmHg]; P < 0.01), but neither isotonic albumin solution nor saline significantly changed ICP. The increase in ICP with hypotonic albumin solution was associated with an increase in central venous pressure (CVP) (by 5.4 mmHg [SEM, 0.6 mmHg]; P < 0.001), but no significant changes in cardiac output or stroke volume. None of the infusions changed renal blood flow, plasma creatinine level, creatinine clearance or plasma or urinary electrolyte levels. Conclusion: Compared with saline or isotonic albumin solution, hypotonic albumin solution increased ICP and CVP, but did not alter arterial pressure, cardiac output renal blood flow or renal function. Our findings support the view that the tonicity of the albumin solution, rather than the albumin itself, is responsible for increasing ICP.