The grades of evidence (I-III) and levels of recommendations (I-III) are defined at the end of the "Major Recommendations" field.
Level I
There are insufficient data to support a Level I recommendation for this topic.
Level II
Blood pressure should be monitored and hypotension (systolic blood pressure <90 mm Hg) avoided.
Level III
Oxygenation should be monitored and hypoxia (PaO2 <60 mm Hg or O2 saturation <90%) avoided.
Summary
A significant proportion of traumatic brain injury (TBI) patients have hypoxemia or hypotension in the prehospital setting as well as inhospital. Hypotension or hypoxia increase morbidity and mortality from severe TBI. At present, the defining level of hypotension is unclear. Hypotension, defined as a single observation of a systolic blood pressure of less than 90 mm Hg, must be avoided if possible, or rapidly corrected in severe TBI patients. A similar situation applies to the definition of hypoxia as apnea cyanosis in the field, or a PaO2 <60 mm Hg. Clinical intuition suggests that correcting hypotension and hypoxia improves outcomes; however, clinical studies have failed to provide the supporting data.
Definitions:
Grades of Evidence
Class I - Good quality randomized controlled trial (RCT)
Class II - Moderate quality RCT, good quality cohort, or good quality case-control
Class III - Poor quality RCT; moderate or poor quality cohort; moderate or poor case-control; or case series, databases, or registries
Levels of Recommendation
Levels of recommendation are Level I, II, and III, derived from Class I, II, and III evidence, respectively.
Level I - Recommendations are based on the strongest evidence for effectiveness, and represent principles of patient management that reflect a high degree of clinical certainty.
Level II - Recommendations reflect a moderate degree of clinical certainty.
Level III - Recommendations for which the degree of clinical certainty is not established.