Discussion
The aims of the study were to characterize the utilization of ICPM in a cohort of older adults presenting with isolated TBI and identify factors associated with ICPM in those meeting the BTF guidelines. ICPM occurred in less than 3% of patients. Intraparenchymal hemorrhage on initial imaging, skull fractures, and receipt of neurosurgical intervention were identified as the factors associated with ICPM in those who met the BTF guidelines. To our knowledge, this study is one of the first to identify the characteristics in those ≥60 years of age presenting with isolated TBI who meet the BTF guidelines and undergo ICPM.
It has been well established that elevated ICP associated with severe TBI leads to increased morbidity and mortality.2 4 5 23 Consequently, ICPM and treatment of intracranial hypertension remain the mainstay of care in patients with severe TBI. As a result, all previous BTF guidelines recommend ICPM, with the most recent version presenting monitoring as level IIB evidence to reduce in-hospital and 2-week mortality after injury.6 However, reports of compliance with BTF guidelines for ICPM vary widely (from 10% to 75%),8 11 22 likely due to a lack of evidence to definitively associate its use with improved outcomes.5 7 8 11–24 Chesnut et al21 randomized patients to either an invasive ICP monitor or a clinical/radiological examination and failed to find differences in outcomes between the strategies. Furthermore, current BTF guidelines do not specifically recognize older adults with TBI as a distinct population, despite the association with different risk factors, mechanisms of injury, disease progression, and comorbid conditions in these patients, as well as normal anatomic changes that occur with aging and affect the development of intracranial hypertension.25 Nevertheless, it is well established that older patients are at increased risk of adverse outcomes after TBI compared with their younger counterparts.20 23 24 Accordingly, it is reasonable to speculate that older patients with TBI may need to be managed differently from younger patients.
The use of ICPM was low overall (<3% of study sample) and among those meeting the BTF criteria (18%). Although the reason for such a low compliance rate is unclear, it may reflect the fact that current BTF guidelines are not widely considered a recommended practice due to an inherent skepticism of the benefit of ICPM in older adults with severe TBI, given the lack of dedicated research focused on outcomes within this age group and the overall mixed evidence in the currently available literature. It is certainly possible that with increasing age, patients were not offered more aggressive care based on individual patient or family wishes. Additionally, physician clinical decision-making based on 24-hour survivability given injury severity (fixed and dilated pupils, uncal herniation, basal cistern effacement, midline shift), non-recoverable injuries, pre-existing neurological disabilities, overall life expectancy, and inherent bias due to limited available data undoubtedly influence the rate of ICP monitor utilization, although this information is not readily elucidated from our data. Certainly, such a low percentage of patients undergoing ICPM in a large multi-institutional trial suggests that, although the BTF guidelines may be a useful resource or starting point to guide management in older adults, additional factors (individual, provider, and institutional) also heavily influence the decision-making processes and highlights the need for further evidence-based guidelines that specifically focus on the care of older adults with TBI.
One finding of our study that may account for such a small percentage of patients undergoing ICPM, despite meeting the BTF criteria, is earlier establishment of code status and implementation of palliative interventions (discontinuation of life-sustaining measures and hospice care) in those who did not undergo ICP monitor placement. It is unclear if these patients were never offered ICPM or if they opted to forego monitor placement. Given the similar head AIS and GCS scores between both groups, this difference does not likely reflect a discrepancy in injury severity as it is commonly measured. Instead, those patients who received ICPM were significantly more likely to have an underlying skull fracture and/or intraparenchymal or intraventricular hemorrhage. Skull fractures have been shown in two prior studies to be a marker of more severe underlying parenchymal injury in patients with both mild and severe TBI.26 27 As such, this difference suggests that patients who received ICPM may have had more severe injuries, but does not account for relatively later pursuit of palliative interventions. The delay may reflect variations in the availability and utilization of palliative interventions across the different trauma centers that are not captured by our data.
There are multiple limitations to this study, the most notable of which is that the extremely small sample size limited our ability to reliably correlate clinical outcomes with ICP monitor placement. Additionally, sample size limited the ability to make comparisons in the setting of ICPM between those who did and did not undergo neurosurgical interventions. The lack of available data regarding patient characteristics, specifically frailty measures, clinical scenarios, and provider factors, may have influenced the decision whether or not to place an ICP monitor. There is also certain variability in practice management at the participating institutions, which likely introduced some selection bias related to who received an ICP monitor. Finally, our findings are affected by all the inherent limitations of an observational, retrospective study.