Discussion
In our study of 327 patients taking antiplatelet medications who sustained blunt head trauma, 40.7% were found to have an acute ICH. Nine required neurosurgical intervention and none died during the hospitalization. Only three patients (0.9%) with an initial negative head CT scan were found to have a delayed ICH on repeat head CT. These delayed ICH were all found on routine repeat head CT imaging, and not due to any clinical change. None of these patients required neurosurgical intervention and none died during the hospitalization.
As mounting evidence from the 1960s to the 1980s show low-dose aspirin to be an effective means of reducing cardiovascular risk, its use in adults has become widespread. An epidemiological analysis showed that nearly 30% of all adults aged 40 years or older in the USA self-report taking low-dose aspirin for primary or secondary cardiovascular disease (CVD) prevention, and the prevalence of aspirin use only increases with age.21 The US Preventive Services Task Force currently recommends low-dose aspirin use for primary CVD prevention and colorectal cancer.22 Despite the known association between antiplatelet agents and increased bleeding risk in general, few studies have looked directly at the odds of acute or delayed traumatic ICH in patients taking these medications. Among these studies, rates of ICH in patients on antiplatelet medications presenting with blunt head trauma ranged from 3.6% to 67.3%.5
Although our study included all adult patients, our patient population had an average age of 76 years. Our high rate of ICH may be related to this factor. Prior research has shown that the geriatric population suffers from a higher rate of acute ICH. As the brain ages, there is volume loss, making bridging vein more vulnerable to bleeding along with decreased elasticity.23 The aging US population has led to increased utilization of antiplatelet medications, likely contributing to the increased incidence of bleeds.24
The reported incidence of delayed ICH in the antiplatelet patient population is 0%–4%.10–16 These studies differed in their methodology and quality, several were retrospective, others were from trauma registries and some included patients on vitamin K antagonists. Our study found that the rate of delayed ICH is 0.9%, on the lower end of the previously reported range. This suggests that admitting all patients taking antiplatelet medications with blunt head trauma and a negative initial head CT may not be warranted. However, it may be prudent to admit nonagenarians, with higher injury severity scores, and lower platelet counts.
While the association between anticoagulation and increased risk of traumatic ICH is well established in the literature, there are fewer studies quantifying the incidence of traumatic ICH in patients taking antiplatelet medications. Several studies have reported no increased risk for bleeding, mortality or neurosurgical interventions with antiplatelet medications.25–28 However, a meta-analysis with over 20 000 patients showed a pooled OR of 1.87 (95% CI 1.27 to 2.74) with increased odds of ICH for patients on all antiplatelet therapy, although not for patients on aspirin alone.5 This conflicting evidence highlights the need for more prospective trials on the effects of antiplatelet medications on ICH and the risk to patients. This information would be valuable as clinicians weigh the risks and benefits of antiplatelet medications, especially in patients who are older with risk factors for falls.
Our results should be interpreted in the context of several limitations. First, as patients were enrolled retrospectively into this study from trauma registries, there likely were patients with head injuries who presented to the ED and were not seen by the trauma services. Second, antiplatelet use by patients was based on documentation in the medical records. Analysis with platelet function testing was not routinely performed, so it is unclear if patients were compliant with their antiplatelet medications. Third, the protocol for repeat head CT imaging was not universally applied. Many patients did not receive a repeat head CT, limiting the ability to quantify the rate of minor subclinical delayed ICH. Fourth, no follow-up was performed after the hospitalization. Some patients may have had an acute ICH and were discharged to hospice, and others may have had a delayed ICH that occurred after hospital discharge. Although most delayed cases of ICH occur within the first 24 hours, some do occur up to 10 days after the initial head injury which would lead to under reporting of these cases. Finally, this study was not designed to have a control group with patients not on antiplatelets. Therefore, we could only perform comparisons between antiplatelet groups, rather than examine the effects of the individual agents on rates of ICH. Additionally, patients on antiplatelet agents may be more likely to receive a head CT compared with those who are not, which may lead to an increase in the ICH rate of limited clinical significance.
The findings of our study suggest that antiplatelet use increases the odds for the development of acute ICH after head trauma, with low risk for delayed ICH. Therefore, we recommend that all patients on antiplatelets with head injury have immediate head CT imaging. These results are generalizable to patients on the trauma service with head injury, who are potentially sicker than the overall emergency department population. However, even in these patients, we do not recommend routine admission for observation or repeat head CT imaging on asymptomatic patients with negative initial head CT imaging. These patients can safely be discharged home with outpatient follow-up and strict return precautions.
Our research adds to the previously conflicting evidence, demonstrating the need for additional investigation in this area. If future prospective studies confirm the increased rate of ICH in patients on antiplatelet medications with head injury, trauma activation guidelines may need to be amended to include these patients. In addition, identifying risk factors for ICH in patients taking antiplatelet agents may better inform physicians regarding the risk-benefit analysis in deciding on antiplatelet therapy.