Is thenar tissue hemoglobin oxygen saturation in septic shock related to macrohemodynamic variables and outcome?

Abstract

Introduction: The study objectives were to evaluate septic shock-induced alterations in skeletal muscle hemoglobin oxygenation saturation (StO2) using near-infrared spectroscopy (NIRS) and forearm skin blood flow velocity using laser Doppler (LD) to determine the relationship of macroperfusion and microperfusion parameters, and to test the relationship of the worst NIRS parameters during the first 24 hours of shock with 28-day prognosis.

Methods: A prospective, observational study was performed in a 21-bed university hospital surgical intensive care unit. Forty-three septic shock patients with at least another organ failure underwent a 3-minute, upper arm (brachial artery) vascular occlusion test (VOT). Microperfusion parameters (thenar eminence StO2 and forearm LD skin blood flow) were collected on days 1, 2 and 3, before (baseline StO2 and LD values) and during the 3-minute VOT with calculation of occlusion and reperfusion slopes for StO2 and LD. Daily Sequential Organ Failure Assessment (SOFA) score, macrohemodynamic parameters (systolic arterial blood pressure, cardiac output (pulmonary artery catheter or transesophageal Doppler), mixed venous oxygen saturation (pulmonary artery or superior vena cava catheter)) and metabolic parameters (pH, base excess, lactate) were determined.

Results: Baseline StO2 (82% (75 to 88) vs. 89% (85 to 92), P = 0.04) and reperfusion slope (2.79%/second (1.75 to 4.32) vs. 9.35%/second (8.32 to 11.57), P < 0.0001) were lower in septic shock patients than in healthy volunteers. StO2 reperfusion slope correlated with occlusion slope (P < 0.0001), cardiac output (P = 0.01) and LD reperfusion slope (P = 0.08), and negatively with lactate level (P = 0.04). The worst StO2 reperfusion slope during the first day of shock was lower in nonsurvivors than in survivors (P = 0.003) and improved significantly the predictive value of Simplified Acute Physiology Score II and SOFA scores.

Conclusions: The alteration of StO2 reperfusion slope in septic shock patients compared with healthy volunteers was related with macrohemodynamic, microhemodynamic and metabolic parameters. The addition of the worst value of the day 1 StO2 reperfusion slope improved the outcome prediction of Simplified Acute Physiology Score II and SOFA scores.

Figure 1

Tissue hemoglobin oxygen saturation and laser Doppler measurement. Example of a real tracing for tissue hemoglobin oxygen saturation (StO₂) and laser Doppler measurements obtained before and during the occlusion test. TPU, tissue perfusion units.

Figure 2

Baseline tissue hemoglobin oxygen saturation and the reperfusion slope. (a) Box plot for baseline tissue hemoglobin oxygen saturation (StO₂) in healthy volunteers compared with that for septic shock patients on day 1. (b) Box plot for reperfusion slope in healthy subjects compared with that for septic shock patients on day 1.

Figure 3

Correlation between central venous oxygen saturation and tissue hemoglobin oxygen saturation. Correlation between central venous oxygen saturation (SvO₂) and tissue hemoglobin oxygen saturation (StO₂) obtained during the first day of septic shock.

Figure 4

Correlation between hemodynamic and metabolic parameters and occlusion and reperfusion slopes. (a) Correlation between tissue hemoglobin oxygen saturation (StO₂) occlusion and reperfusion slopes for 98 measurements performed on 43 patients (day 1, 43 measurements; day 2, 34 measurements; day 3, 21 measurements) during the first 3 days of septic shock. (b) Correlation between reperfusion slope and cardiac output (CO) obtained for 77 measurements, corresponding to 33 patients on day 1, 28 patients on day 2, and 16 patients on day 3. (c) Correlation between lactate plasma concentration and reperfusion slope (48 measurements), corresponding to 23 patients measured on day 1, 18 patients on day 2, and seven patients on day 3. (d) Correlation between the reperfusion slope obtained with laser Doppler and the one obtained with StO₂ during the simultaneous occlusion tests: 37 measurements were obtained, on 15 patients on day 1, 13 patients on day 2, and nine patients on day 3. TPU, tissue perfusion units.

Figure 5

Predictive value on outcome. Area under the curve (AUC) for the multivariate model using each determinant alone or in combination (solid curve). Se, sensitivity; SOFA, Sequential Organ Failure Assessment; Sp, specificity.