This proposal aims to provide some objective, non-invasively achieved, physiologically relevant data in order to provide some rational basis for decision-making for transfusion in sTBI. Specifically this proposal is an observational study of transfusion and brain tissue saturation in sTBI patients. The results will illustrate to what degree brain tissue oxygenation is critically dependent on the degree of anemia in sTBI and help in the decision of whether transfusion might be helpful.

While there are studies that have invasively monitored cerebral saturation and brain tissue oxygen in severe traumatic brain injury (sTBI) patients, there are none using non-invasive cerebral saturation monitoring in TBI patients undergoing packed red blood cell (pRBC) transfusion. To date, all published studies have involved invasive monitoring with their concomitant potential side effects. Insertion of invasive probes and monitors has several risks and side effects including bleeding, local trauma and brain damage, and infection. Furthermore, they have limited utility as information is restricted to the region of the brain surrounding the probe, as opposed to a more global picture. We therefore propose an observational study using non-invasive near infrared spectroscopy to monitor brain tissue oxygen during the transfusion of packed red blood cells.

Primary Hypothesis:

• Improved oxygen delivery causes improved brain tissue oxygen saturation.

Testable Hypothesis:

• The transfusion of packed red blood cells resulting in a change in the hemoglobin in the 70- 100g/L range, will be associated with an increase in cerebral tissue oxygen saturation measured by near infrared spectroscopy in severe traumatic brain injured patients.

Primary Aims:

• Evaluate the applicability of a 4 wavelength near-infrared spectroscopy (NIRS) to monitor the cerebral oximetry in traumatic brain injury patients. Observe the trend of cerebral tissue oxygenation saturations (StO2) before, during and after a blood transfusion in TBI patients.

Secondary Hypothesis:

• We hypothesize that as pRBCs are transfused there will be a plateau (i.e. hemoglobin threshold) beyond which no increase in cerebral tissue oxygenation will occur.
• There will be lag time between the increase in systemic hemoglobin and the improvement of cerebral tissue oxygenation.

Secondary Aims:

• To correlate the systemic hemoglobin level with cerebral tissue oxygenation saturation as pRBCs are transfused.
• Correlation of non-invasive cerebral tissue oxygenation saturation measurements with invasive brain tissue oxygen tension (if available).

Inclusion Criteria:

1. Age > 18 years old
2. Patient with clinical diagnosis of severe TBI and GCS <9
3. Patient requiring PRBC transfusion with a qualifying Hb< 10/dL

Exclusion Criteria:

1. Inability to place the NIRS probes on the patients (facial fractures, facial laceration, etc.).

2. Deficient signal of SctO2 impeding its proper valuation

3. Active coronary ischemia as judged by dynamic ischemic ECG changes and/ or positive troponin levels not due to myocardial contusion.

4. Active hemorrhage: Example

   1. Bleeding into the chest, abdomen or retro-peritoneum likely to require surgery +/- embolization
   2. Pelvic fracture likely to require surgery +/- embolization
   3. More than two long bone fractures requiring operative fixation

5. Clinical diagnosis of drug or alcohol intoxication as predominant cause of coma

6. Systolic BP <90mmHg

7. Heart rate > 120bpm

8. GCS=3 + un-reactive pupils

30 Patient with clinical diagnosis of severe TBI and GCS <9 and Age > 18 years old