Packed red blood cell transfusion increases local cerebral oxygenation*

Abstract

Objective: 

To determine a) whether packed red blood cell transfusion (RBCT) increases local brain tissue oxygen partial pressure (Pbto₂) in a neurocritical care population; and b) what (if any) demographic, clinical, or physiologic variables mediate the assumed change.

Design: 

Prospective observational study.

Setting: 

A neurosurgical intensive care unit at a university-based level I trauma center and tertiary care hospital.

Patients: 

Thirty-five consecutive volume-resuscitated patients with subarachnoid hemorrhage or traumatic brain injury, without cardiac disease, requiring Pbto₂ monitoring and receiving RBCT were studied between October 2001 and December 2003.

Interventions: 

None.

Measurements and Main Results: 

The following physiologic variables were measured and compared 1 hr before and after RBCT: Pbto₂, intracranial pressure, cerebral perfusion pressure, hemoglobin oxygen saturation (Sao₂), Fio₂, hemoglobin, and hematocrit. An increase in Pbto₂ was observed in 26 of the 35 patients (74%). In nine patients, Pbto₂ decreased after RBCT. The mean (±sd) increase in Pbto₂ for all patients was 3.2 ± 8.8 mm Hg (p = .02), a 15% change from baseline (1 hr before RCBT). This Pbto₂ increase was associated with a significant mean increase in hemoglobin and hematocrit after RBCT (1.4 ± 1.1 g/dL and 4.2% ± 3.3%, respectively; both p < .001). Cerebral perfusion pressure, Sao₂, and Fio₂ were similar before and after RBCT. Among the 26 patients whose Pbto₂ increased, the mean increase in Pbto₂ was 5.1 ± 9.4 mm Hg or a 49% mean increase (p < .01).

Conclusions: 

RBCT is associated with an increase in Pbto₂ in most patients with subarachnoid hemorrhage or traumatic brain injury. This mean increase appears to be independent of cerebral perfusion pressure, Sao₂, and Fio₂. Further study is required to determine why Pbto₂ decreases in some patients after RBCT.