Background

Traditionally, blood transfusions in the perioperative setting are used to maintain adequate delivery of nutrients and oxygen to organs. However, the effect of blood administration on tissue oxygenation in the perioperative setting remains poorly understood.

Questions/Purposes

The aim of this study was to determine changes in muscle tissue oxygenation saturation (SmO₂) in response to perioperative blood transfusions.

Patients and Methods

Patients undergoing total knee arthroplasty were enrolled. SmO₂, continuous hemoglobin (SpHb), stroke volume (SV), cardiac index, and standard hemodynamic parameters including heart rate (HR), mean arterial blood pressure (MAP), and arterial oxygen saturation (SO₂) were recorded. To assess fluid responsiveness, a passive leg raise (PLR) test was performed before the transfusions were started.

Results

Twenty-eight patients were included in the analysis. Mean (±SD) SmO₂ before transfusion was 63.18 ± 10.04%, SpHb was 9.27 ± 1.16 g/dl, and cardiac index was 2.62 ± 0.75 L/min/m². A significant increase during the course of blood transfusion was found for SmO₂ (+3.44 ± 5.81% [95% confidence interval (CI) 1.04 to 5.84], p = 0.007), SpHb (0.74 ± 0.92 g/dl [95% CI 0.35 to 1.12], p < 0.001), and cardiac index (0.38 ± 0.51 L/min/m2 [95% CI 0.15 to 0.60], p = 0.002), respectively. However, the correlation between SmO₂ and SpHb over the course of the transfusion was negligible (ρ = 0.25 [95% CI −0.03 to 0.48]). A similar lack of correlation was found when analyzing data of those patients who showed a positive leg raise test before the start of the transfusion (ρ = 0.37 [95% CI −0.11 to 0.84]).

Conclusion

We detected a statistically significant increase in SmO₂ during the course of a single unit blood transfusion compared to baseline. However, there was no evidence of a correlation between longitudinal SmO₂ and SpHb measurements.