The Impact of Red Blood Cell Transfusion on Cerebral Tissue Oxygen Saturation in Severe Traumatic Brain Injury

There are a range of opinions on the benefits and thresholds for the transfusion of red blood cells in critically ill patients with traumatic brain injury (TBI) and an urgent need to understand the neurophysiologic effects. The aim of this study was to examine the influence of red blood cell transfusions on cerebral tissue oxygenation (SctO₂) in critically ill TBI patients.

This prospective observational study enrolled consecutive TBI patients with anemia requiring transfusion. Cerebral tissue oxygen saturation (SctO₂) was measured noninvasively with bilateral frontal scalp probes using near-infrared spectroscopy (NIRS) technology. Data were collected at baseline and for 24 h after transfusion. The primary outcome was the applicability of a four-wavelength near-infrared spectrometer to monitor SctO₂ changes during a transfusion. Secondary outcomes included the correlation of SctO₂ with other relevant physiological variables, the dependence of SctO₂ on baseline hemoglobin and transfusion, and the effect of red blood cell transfusion on fractional tissue oxygen extraction.

We enrolled 24 patients with severe TBI, of which five patients (21 %) were excluded due to poor SctO₂ signal quality from large subdural hematomas and bifrontal decompressive craniectomies. Twenty transfusions were monitored in 19 patients. The mean pre- and post-transfusion hemoglobin concentrations were significantly different [74 g/L (SD 8 g/L) and 84 g/L (SD 9 g/L), respectively; p value <0.0001]. Post-transfusion SctO₂ was not significantly greater than pre-transfusion SctO₂ [left-side pre-transfusion 69 % (SD 7) vs. post-transfusion 70 % (SD 10); p = 0.68, and right-side pre-transfusion 69 % (SD 5) vs. post-transfusion 71 % (SD 7); p = 0.11]. In a multivariable mixed linear analysis, mean arterial pressure was the only variable significantly associated with a change in SctO₂.

The bifrontal method of recording changes in NIRS signal was not able to detect a measurable impact on SctO₂ in this sample of patients receiving red blood cell transfusion therapy in a narrow but conventionally relevant, range of anemia.