Peripheral Perfusion Index as an Early Predictor for Central Hypovolemia in Awake Healthy Volunteers

BACKGROUND: In healthy volunteers, we investigated the ability of the pulse oximeter derived peripheral perfusion index (PPI) to detect progressive reductions in central blood volume. METHODS: Twenty-five awake, spontaneously breathing, healthy male volunteers were subjected to progressive reductions in central blood volume by inducing stepwise lower body negative pressure (LBNP) with 20 mm Hg for 5 minutes per step, from 0 to -20, -40, -60, and back to 0 mm Hg. Throughout the procedure, stroke volume (SV), heart rate (HR), and mean arterial blood pressure were recorded using volume-clamp finger plethysmography. Assessment of the PPI was done by pulse oximetry. Additionally, RESULTS: Of the 25 subjects, one did not complete the study because of cardiovascular collapse. After the first LBNP step (-20 mm Hg), PPI decreased from 2.2 (1.6-3.3) to 1.2 (0.8-1.6) (P = 0.007) and SV decreased from 116 +/- 3.0 mL to 104 +/- 2.6 mL (P = 0.02). The magnitude of the PPI decrease (41% +/- 6.0%) was statistically different from that observed for SV (9% +/- 1.3%) and HR (3% +/- 1.9%). During progression of LBNP SV decreased and HR increased progressively with the increased applied CONCLUSIONS: These results indicate that the pulse oximeter-derived PPI may be a valuable adjunct diagnostic tool to detect early clinically significant central hypovolemia, before the onset of cardiovascular decompensation in healthy volunteers. (Anesth Analg 2013;116:351-6)