Table 3.
Clinical studies assessing the impact of anemia or RBC transfusions on PbtO2 and other physiologic parameters in brain-injured patients
| Study | Patients | Design | Baseline | Intervention | Main findings |
| Smith and colleagues [139] | 23 TBI 12 SAH |
Retrospective (prospective database) | Hb = 8.7 g/dl PbtO2 = 24.4 mmHg |
Any RBC transfusion (number of units not specified a priori; 80% received ≥1 unit; mean Hb increased to 10.2 g/dl) General transfusion threshold Hb <10 g/dl or hct <30% (no protocol) |
- Mean increment in PbtO2 3.2 mmHg (15%) - Increment not related to baseline PbtO2 - PbtO2 decreased in 9/35 patients (26%) |
| Leal-Noval and colleagues [140] | 51 TBI | Prospective observational | Hb = 9.0 g/dl PbtO2 = 24.4 mmHg |
1 or 2 units RBCs (number of units not specified a priori; 52% received 2 units; mean Hb increased to 10.6 g/dl) General transfusion threshold Hb <10 g/dl (no protocol) |
- Mean increment in PbtO2 3.8 mmHg (16%) - Increment larger at lower baseline PbtO2 - PbtO2 decreased in 13/51 patients (25%) |
| Leal-Noval and colleagues [141] | 66 TBI (males) | Prospective observational | Hb = 8.9 g/dl PbtO2 = 21.3 to 26.2 mmHg |
1 or 2 units RBCs number of units not specified a priori; 59% received 2 units; mean Hb increased to 10.2 g/dl) General transfusion threshold Hb <9.5 g/dl (no protocol) |
- Newer units of blood (≤14 days) resulted in greater mean increment in PbtO2 (3.3 mmHg (16%) vs. 2.1 mmHg (8%)) - PbtO2 decreased only in patients receiving older blood (>19 days) |
| Zygun and colleagues [142] | 30 TBI | Prospective RCT | Hb = 8.2 g/dl PbtO2 = 18.8 mmHg |
Randomized to transfusion thresholds of 8, 9, or 10 g/dl; 2 units RBCs administered over 2 hours (mean Hb increased to 10.1 g/dl) | - Mean increment in PbtO2 2.2 mmHg (12%) - Increment in PbtO2 most prominent when LPR >25 - PbtO2 decreased in 13/30 patients (43%) - No effect on SjvO2 or microdialysis parameters |
| Ekelund and colleagues [162] | 8 SAH (TCD-vaso-spasm) | Prospective interventional | Hb = 11.9 g/dl | Isovolemic hemodilution (venesection with infusion of dextran 70 and 4% albumin) to mean Hb of 9.2 g/dl | - Outcomes (using 133Xenon and SPECT): - Increased global CBF (52.3 to 58.6 ml/100 g/min) - Reduced cerebral vascular resistance - Reduced oxygen delivery - Increased ischemic brain volume |
| Muench and colleagues [163] | 10 SAH | Prospective interventional | Hb = 10.6 g/dl PbtO2 = 24.8 mmHg |
Volume expansion with HES ± crystalloid to achieve ITBVI >1000 ml/m2; this produced a decline in Hb of 1.3 to 2.0 g/dl (on various days) | - Although hypervolemia/hemodilution produced a slight increment in CBF, PbtO2 decreased by an average of 0 to 5 mmHg - Only induced hypertension was consistently effective at raising PbtO2 |
| * Dhar and colleagues [164] | 8 SAH | Prospective interventional | Hb = 8.7 g/dl | One unit RBCs (mean Hb increased to 9.9 g/dl) | - Outcomes assessed using PET: - No significant change in CBF - Reduced O2 extraction ratio (49 to 41%; P = 0.06) - No significant change in CMRO2 - Reduction in oxygen extraction ratio observed also in territories with vasospasm and low oxygen delivery |
| Oddo and colleagues [165] | 20 SAH | Retrospective (prospective database) | Not applicable | None | - Hb <9 g/dl associated with higher risk of PbtO2 <20 mmHg (OR 7.2, P < 0.01) and LPR >40 (OR 4.2, P = 0.02) |
| Chang and colleagues [237] | 27 TBI | Retrospective | Not applicable | None | - 13.7% of PbtO2 readings <20 mmHg - No significant association between PbtO2 and Hb |
| Naidech and colleagues [238] | 6 SAH | Prospective observational | Not reported | 14 RBC transfusions (no protocol) | - Hb correlated with cerebral oximetry (rO2) - rO2 increased following 11/14 transfusions, but not statistically significant |
| Sahuquillo and colleagues [239] | 28 TBI | Prospective | Not applicable | None | - Critical LOI (suggestive of ischemia/infarction) associated with lower Hb (11.7 g/dl vs. 13.1 g/dl) |
| Cruz and colleagues [240] | 62 TBI | Retrospective (prospective data) | Not applicable | None | - Cerebral extraction of oxygen was highest when Hb <10 g/dl |
* published only as abstract.
CBF = cerebral blood flow; CMRO2 = cerebral metabolic rate; Hb = hemoglobin; HES = hydroxyethyl starch; ITBVI = intrathoracic blood volume index; LOI = jugular venous lactate:oxygen index; LPR = lactate:pyruvate ratio; PbtO2 = brain tissue oxygen tension; PET = positron emission tomography; RBC = red blood cell; RCT = randomized controlled trial; rO2 = cerebral oximetry; SAH = subarachnoid hemorrhage; SjvO2 = jugular venous oxygen saturation; SPECT = single photon emission computed tomography; TBI = traumatic brain injury; TCD = transcranial Doppler.