Traumatic brain injury (TBI) is considered an independent risk factor of venous thromboembolism (VTE). However, the role of TBI severity in VTE risk has not been determined. We hypothesized that increased severity of brain injury in patients with isolated TBI (iTBI) is associated with an increased incidence of VTE.
The records of patients admitted from June 2006 to December 2011 were reviewed for injury data, VTE risk factors, results of lower extremity surveillance ultrasound, and severity of TBI. Patients were identified by DRG International Classification of Diseases—9th Rev. codes for TBI, and only those with a nonhead Abbreviated Injury Scale (AIS) score of 1 or lower, indicating minimal associated injury, were included. The association of iTBI and VTE was determined using a case-control design. Among iTBI patients, those diagnosed with VTE (cases) were matched for age, sex, and admission year to those without VTE (controls). Data were analyzed using conditional logistic regression.
There were 345 iTBI patients: 41 cases (12%) and 304 controls (88%). A total of 151 controls could not be matched to an appropriate case and were excluded. Of the remaining 153 controls, 1 to 16 controls were matched to each of the 41 VTE cases. Compared with the controls, the cases had a higher mean head-AIS score (4.4 vs. 3.9, p = 0.001) and overall Injury Severity Score (20.4 vs. 16.8, p = 0.001). Following adjustment for all factors found to be associated with VTE (ventilator days, central line placement, operative time > 2 hours, chemoprophylaxis, history of VTE, and history of cancer), the cases were significantly more likely to have a greater head injury severity (head-AIS score ≥ 5; odds ratio, 5.25; 95% confidence interval, 1.59–17.30; p = 0.006).
The incidence of VTE in iTBI patients was significantly associated with the severity of TBI. VTE surveillance protocols may be warranted in these high-risk patients, as early detection of VTE could guide subsequent therapy.
LEVEL OF EVIDENCE
Epidemiologic/prognostic study, level III.