Factors associated with receipt of intracranial pressure monitoring in older adults with traumatic brain injury

Introduction

Traumatic brain injury (TBI) is a major health problem among older adults. Although individuals 65 years or older represent only 10% of all patients with TBI, they account for 50% of TBI-related deaths.1 In 2013, TBI was responsible for 485 000 emergency department visits, 123 000 hospitalizations, and 21 000 deaths among adults aged 65 and older in the USA.2 Furthermore, patients who were older than 75 years of age experienced the highest TBI-related hospitalization rate—twice that of any other age group.2

An important but controversial aspect of managing severe TBI is intracranial pressure monitoring (ICPM) to detect and manage intracranial hypertension and reduce secondary insults.3–5 In the 2016 Fourth Edition of the Guidelines for the Management of Severe Traumatic Brain Injury, the Brain Trauma Foundation (BTF) recommended ICPM in patients with a Glasgow Coma Scale (GCS) score <9 and evidence of CT abnormality as level IIB evidence to reduce in-hospital and 2-week mortality after injury.6 However, these guidelines do not specifically address older adults with TBI. In fact, many prior studies either excluded older patients or grouped them with younger adults in outcomes assessment.7–10 Additionally, there is conflicting evidence on whether ICPM improves outcomes in severe TBI in both young5 7 8 11–21 and older patient populations.19 22–24 Given the lack of clear guidance regarding ICPM and the limited available data on outcomes, the decision of whether or not to place a monitor in an older adult presenting with TBI is typically left to an individual physician’s judgment.

The normal cerebral atrophy that occurs with aging may reduce the risk of intracranial hypertension. Thus, conceptually, ICPM may not benefit many elderly patients. Yet this is not reflected in current management guidelines.25 Given the lack of guidelines specific for ICPM in older adults due to the limited number of studies that have investigated the indications and role of ICPM25 in this population and specifically in the setting of isolated TBI, we conducted an indepth analysis to better understand which older patients receive ICPM and whether the current BTF recommendations are followed. The objectives of this study were to (1) characterize the utilization of ICPM in a cohort of older adults presenting with isolated TBI and (2) identify factors associated with ICPM among those patients who met the BTF guidelines. We hypothesized, given the lack of evidence-based guidelines specific for older adults, that indications for ICPM in this population are similar to their younger counterparts and in accordance with the most recent and widely available BTF guidelines.

Methods

Results

Patients were evaluated at one of 45 participating trauma centers. Most centers were level 1 (86.7%) and >600 beds (53.3%). The mean number of annual admissions was 2571±1550 among the participating centers (table 1).

Of the 3081 patients included in the Geri-TBI cohort, 2303 (74.7%) were ≥60 years of age, of whom 66 (2.9%) received ICPM. An intraparenchymal fiberoptic monitor (“bolt”) was used in 33 (50.0%) patients, and 33 (50.0%) underwent placement of an external ventricular drain (EVD). Individuals who received ICPM differed significantly across demographic, clinical, and injury-related characteristics relative to those who did not receive ICPM (table 2).

On bivariate analysis, patients who received ICPM were younger (72.2±8.4 years vs. 77.1±9.1 years, p<0.001), more likely to experience CT worsening (68.2% vs. 23.3%, p<0.001), and more likely to have been injured in a motor vehicle collision (21.2% vs. 7.9%, p<0.001), even though falls were the most common cause of injury in both cohorts. Head AIS score and GCS score were significantly worse in patients who underwent ICPM (p<0.001). Those with ICPM were more likely to undergo neurosurgical intervention as well as experience both longer hospital and intensive care unit (ICU) lengths of stay. Finally, patients with ICPM were more likely to receive palliative interventions (47.7% vs. 13.9%, p<0.001) and were more likely to discharge to a more dependent level of care as compared with their preinjury residence (89.4% vs. 44.4%, p<0.001) (table 2). Patients with ICPM in place also experienced higher mortality (46.9% vs. 9.3%, p<0.001) (table 2).

Our logistic regression model included factors independently associated with ICPM (table 3). Relative to GCS score of 13 to 15, GCS score of 9 to 12 (OR 10.2; 95% CI 4.3 to 24.4) and GCS score of <9 (OR 15.0; 95% CI 7.2 to 31.1) were significantly associated with ICPM. As well, intraventricular hemorrhage (OR 2.4; 95% CI 1.2 to 4.83), skull fractures (OR 3.6; 95% CI 2.0 to 6.6), any subsequent CT worsening (OR 3.3; 95% CI 1.8 to 5.9), and receipt of neurosurgical intervention (OR 3.8; 95% CI 2.1 to 7.0) were significantly associated with ICPM.

We identified 240 patients meeting the BTF criteria (ie, CT-verified TBI and GCS score <9) for ICPM, but only 43 (18%) underwent ICPM (table 4). An intraparenchymal fiberoptic monitor was used in 21 (48.8%) patients, and 22 (51.2%) underwent placement of an EVD. Individuals >81 years of age were less likely to undergo ICPM (11.6% vs. 30.5%, p=0.01). Those who met the BTF criteria and underwent ICPM were more likely to undergo neurosurgical intervention (47% vs. 8%, p<0.001) and go on to experience longer hospital and ICU lengths of stay. Mortality, receipt of palliative interventions, and change in residence did not differ between the two groups. However, changes in code status and discontinuation of life-sustaining measures occurred significantly later into hospitalization in those who underwent ICPM.

Our final logistic regression model of factors associated with ICPM in patients meeting the BTF criteria demonstrated independent associations with intraparenchymal hemorrhage (OR 2.2; 95% CI 1.0 to 4.7), skull fracture (OR 3.9; 95% CI 1.9 to 8.2), and receipt of neurosurgical interventions (OR 3.5; 95% CI 1.7 to 7.2) (table 5).

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.

Conclusion

Although intraparenchymal hemorrhage, skull fractures, and receipt of neurosurgical intervention were associated with ICPM among older adults with TBI, the overall utilization of ICPM in those who meet the BTF criteria remains markedly low across high-volume trauma centers. Therefore, the utility and potential benefits of ICPM in this unique patient population remain unclear. Our analysis highlights the need for further, more detailed studies of ICPM in older adults with severe TBI, as well as investigation of the clinical, patient-specific, and provider-specific factors that may influence utilization and account for current low compliance with the BTF guidelines.