Peripheral Perfusion Index Predicts Hypotension during Fluid Withdrawal by Continuous Veno-Venous Hemofiltration in Critically Ill Patients

Aim: Peripheral perfusion may predict harmful hypovolemic hypotension during fluid withdrawal by continuous veno-venous hemofiltration (CVVH) in critically ill patients with acute kidney injury. Methods: Twenty-three critically ill AKI patients were subjected to progressive fluid withdrawal. Systemic hemodynamics and peripheral perfusion index (PPI) by pulse oximetry, forearm-to-fingertip skin temperature gradient (Tskin-diff) and tissue oxygen saturation (StO2, near infra-red spectroscopy) were measured. Results: Most hemodynamic values decreased with fluid withdrawal, particularly in the hypotensive group, except for stroke volume (SV) and cardiac output, which decreased to a great extent in the non-hypotensive patients. Increases in systemic vascular resistance (SVR) were less in hypotension. Baseline pulse pressure and PPI were lower in hypotensive (n = 10) than non-hypotensive patients and subsequent PPI values paralleled SV decreases. A baseline PPI ≤0.82 AU predicted hypotension with a sensitivity of 70%, and a specificity of 92% (AUC 0.80 ± 0.11, p = 0.004). Conclusion: Progressive fluid withdrawal during CVVH is poorly tolerated in patients with less increases in SVR. The occurrence of hypotension can be predicted by low baseline PPI.