Secondary injury being immediately following the primary insult and can continue for a prolonged period of time. Often, secondary injury is more difficult to treat and carries a higher rate of morbidity and mortality than the primary injury itself. Hypoxia and hypoperfusion are two leading contributing factors to secondary brain injury. One study found that patients with severe TBI who developed two or more episodes of hypotension had an increased odds ratios of two to eight times higher risk for death. Hypotension within the first 48 hours of ICU admission also has been found predictive of mortality.