Abstract
BACKGOUND
Nontraumatic subdural hematomas are a common indication for inpatient hospitalization in the United States, yet there is little high-quality evidence regarding which patients should receive surgical or medical treatment. We sought to assess variation in surgical management and medical treatment with steroids for nontraumatic subdural hematomas across the United States.
METHODS
Utilizing the Premier database, patients with a primary discharge diagnosis of nontraumatic subdural hematoma in 2014 were analyzed. ICD procedure codes were used to identify patients who underwent surgical management, and pharmacy data were used to identify patients treated with dexamethasone. Univariable and multivariable analyses were used to examine the association of age, race, sex, academic versus non-academic center, and regions of the United States with conservative or surgical management.
RESULTS
There were 3915 inpatient hospitalizations for nontraumatic SDH in 2014 in the Premier database, of which 1860 (47.5%) underwent surgery, and 360 (9.2%) underwent treatment with dexamethasone, either as a primary treatment or as an adjuvant to surgery. Older age, female sex, and being managed outside of the Western US region were associated with a lower likelihood of undergoing surgical management on multivariable analysis; only younger age was associated with a higher likelihood of being treated with dexamethasone.
CONCLUSIONS
There is considerable variability in surgical management of nontraumatic subdural hematomas across the United States based on age, gender, and region. Future studies should explore the reasons for the variability and attempt to better clarify indications for surgical management of subdural hematomas.
Keywords: Subdural hematomas, Surgical decision-making, Epidemiology
Background
Subdural hematomas (SDH) are an increasingly common indication for hospitalization in the United States,1 and are projected to become the most common cranial neurosurgical condition by 2030.2 While most SDHs are precipitated by trauma,3 a significant number of SDH patients have no clear trauma history, and these patients can present with acute, subacute, or chronic SDH’s.4 Nontraumatic SDH’s frequently occur in elderly patients1 and may result from an unrecognized trivial trauma in most instances;5 aneurysms, cerebral amyloid angiopathy, malignancy, and coagulopathy have also been implicated in some nontraumatic SDHs.6–8
Surgery is more commonly performed in patients with nontraumatic SDH when compared to patients with traumatic SDH, with previous estimates ranging up to 39%−51% of nontraumatic SDH patients being managed surgically depending on the populations studied.1,4,9 Conservative management of SDHs typically consists of clinical observation along with avoidance of antiplatelet and anticoagulant medications. Some nontraumatic SDHs, particularly chronic SDHs, are managed medically, most commonly with steroids (typically dexamethasone) or atorvastatin. These medications can be used either as a primary treatment or as an adjuvant to surgical management to reduce recurrence.10,11
The decision whether to manage a patient surgically or conservatively is typically made based upon on the patient’s neurological exam, the thickness and acuity of blood within the SDH, and the patient’s cardiac risk profile.12,13 There is no class I evidence to help guide these decisions, and survey data suggests considerable variability in decision-making among neurosurgeons for traumatic SDHs;14 however, it is unknown how much variability in surgical management there is for patients with nontraumatic SDH’s, who often are older and have more medical comorbidities than patients with traumatic SDHs.1
We sought to explore practice patterns for surgical and medical management of nontraumatic SDH across the United States at the population level using the Premier Hospital database. We also examined the patterns for use of dexamethasone as either a primary treatment of adjuvant to surgical management in patients with nontraumatic SDH.
Methods
Methods
The Premier Perspective Hospital database is a privately-owned data set that has partnered with the Food and Drug Administration to study procedures and drug use in hospitalized patients at 506 hospitals across the United States, representing ≈15% of hospital discharges annually. All billing and administrative coding information can be cross-linked to hospital pharmacy billing records. Previous studies suggest that hospital and patient characteristics in Premier are representative of the US population.15 For this study, we included adult, 18 years and older, hospitalized patients with the principal discharge diagnosis of nontraumatic subdural hematoma (ICD-9 code 432.1). This code has been validated in the United States previously, with a reported sensitivity of 70%, and a specificity of 100%.16 From this population, we identified a subset of patients who also underwent at least one surgical drainage of their SDH, either craniotomy/craniectomy(ICD-9 procedure codes 1.2, 1.24, 1.25, 1.26, and 1.28) or burr hole (ICD-9 procedure codes 1.09, 1.31, 1.51).1 We then identified patients who underwent additional procedures during their index hospitalization; to reduce the impact of duplicate procedure codes, we required the additional procedures to be dated at least one day from the initial surgery.
Patients that were placed on dexamethasone were identified from pharmacy billing data. We only included patients on a dose of at least 4mg of dexamethasone daily to prevent patients chronically on steroids for other indications being included in the analysis, and further required patients to receive at least 3 doses of the medication to be included. This was meant to exclude patients who received one-time doses of dexamethasone for other reasons (e.g. postoperative nausea). We did not include other corticosteroids besides dexamethasone in the analysis as these drugs are more commonly used for non-neurological indications. If the patient underwent surgical management, steroids were considered adjuvant; if no surgical procedure was performed, dexamethasone was considered primary therapy.
We then examined both initial surgical management and need for additional surgeries with age, race, and sex; we also explored variation of surgical management and need for additional surgical management in the 4 regions of the United States (Midwest, Northeast, South, and West), and compared management between academic and nonacademic medical centers (where academic is defined as a center affiliated with a medical school and promoting at least 4 residency programs, not that the neurosurgery department itself is academic).
Statistical Analysis
Data were managed and analyzed using SAS, version 9.4 (SAS Institute, Cary, North Carolina, USA). The distribution of age is summarized with a median and 25th and 75th percentile (interquartile range; IQR). All other variables were categorical and thus are reported as number and proportion. The Wilcoxon rank sum test was used to compare age between groups of patients, and the χ2 test was used to compare frequencies of categorical variables. Univariate and multivariable logistic regression models were used to estimate unadjusted and adjusted odds ratios (OR) and associated 95% confidence intervals. A p-value of <0.05 was considered statistically significant.
Results
Characteristics of the cohort
3915 patients were admitted with the primary diagnosis of nontraumatic SDH over the study period (Table 1). Most patients admitted during the study period were men (63.4%). 1860 patients (47.5%) underwent at least one drainage. Most initial drainage procedures were burr hole surgeries (86.8%) rather than craniotomies/craniectomies (13.2%). Among the patients who underwent an initial surgical procedure, 99 (2.5% of overall cohort) required an additional surgical procedure during the index hospitalization; there was a trend towards an increased risk of additional procedures if the initial procedure was a burr hole but this did not reach statistical significance (P 0.067). 360 patients (9.2%) were treated with dexamethasone during their hospitalization, either as a primary treatment or in conjunction with surgery.
Table 1:
General characteristics of cohort (n=3915)
| Female gender, N (%) | 1433 (36.6) |
| Race, N (%) | |
| White | 2624 (67.1) |
| Black | 540 (13.8) |
| Other | 746 (19.1) |
| Unknown | 5 |
| Underwent surgery, N (%) | 1860 (47.5) |
| Burr Hole | 1614(41.2) |
| Craniotomy | 246 (6.3) |
| Repeat surgery, N (%) | 99 (2.5) |
| Treated with dexamethasone, N (%) | 360 (9.2) |
Patterns in surgical management
Univariable analysis showed that female sex, increasing age, white race, and being managed outside of the West were all associated with a lower likelihood of surgical management (Table 2). Multivariable analysis of risk factors for surgical management revealed that female sex (OR 0.57 [0.5–0.66], P<0.0001), older age (per 10 years OR 0.88[0.84–0.92], P<0.0001), and being located in any region outside of the West were significant risk factors for nonsurgical management (Table 3). While race overall was not a significant risk factor for surgical management in multivariable analysis, there was a non-significant trend towards an increased odds of surgical management for patients of “other race” when compared to “white race” (OR 1.22, [1.02–1.45]). None of the factors studied were associated with an increased likelihood of requiring additional surgeries during the index hospitalization.
Table 2:
Univariable analysis of factors associated with single and multiple surgical procedures in subdural hematoma patients
| No surgery (N=2055) | Any surgery (N=1860) | p-value | Single surgery (N=1761) | Multiple surgeries (N=99) | p-value | |
|---|---|---|---|---|---|---|
| Age in years, median (IQR) | 76 (64, 84) | 71 (62, 80) | <0.0001 | 71 (63, 80) | 73 (61, 81) | 0.96 |
| Race, N (%) | ||||||
| White | 1410 (68.7) | 1214 (65.4) | 1139 (64.8) | 75 (75.8) | ||
| Black | 287 (14.0) | 253 (13.6) | 0.01 | 245 (13.9) | 8 (8.1) | 0.07 |
| Other | 356 (17.3) | 390 (21) | 374 (21.3) | 16 (16.2) | ||
| Unknown | 2 (0.1) | 3 (0.2) | 3 (0.2) | 0 | ||
| Sex, N (%) | ||||||
| Female | 882 (42.9) | 551 (29.6) | <0.0001 | 519 (29.5) | 32 (32.3) | 0.54 |
| Male | 1173 (57.1) | 1309 (70.4) | 1242 (70.3) | 67 (67.7) | ||
| Care setting, N (%) | ||||||
| Nonacademic | 905 (44) | 780 (41.9) | 0.18 | 739 (42) | 41 (41.4) | 0.92 |
| Academic | 1150 (56) | 1080 (58.1) | 1022 (58) | 58 (58.6) | ||
| Region of United States, N (%) | ||||||
| Midwest | 405 (19.7) | 324 (17.4) | 308 (17.5) | 16 (16.2) | ||
| Northeast | 362 (17.6) | 297 (16) | 0.0007 | 284 (16.1) | 13 (13.1) | 0.81 |
| South | 1073 (52.2) | 970 (52.2) | 916 (52) | 54 (54.6) | ||
| West | 215 (10.5) | 269 (14.5) | 253 (14.4) | 16 (16.2) | ||
| Initial Surgery, N (%) | ||||||
| Burr Hole | N/A | 1614 (86.8) | N/A | 1522 (81.8) | 92 (5) | 0.067 |
| Craniotomy/craniectomy | N/A | 246 (13.2) | 239 (12.8) | 7 (0.4) |
Table 3:
Multivariable analysis of risk factors for surgical management
| aOR | 95%CI | p-value | |
|---|---|---|---|
| Race | |||
| Black vs White | 1.00 | 0.83, 1.21 | 0.08 |
| Other vs White | 1.22 | 1.02, 1.45 | |
| Sex (Female vs Male) | 0.57 | 0.50, 0.66 | <0.0001 |
| Teaching Hospital | 1.12 | 0.98, 1.29 | 0.09 |
| Area | |||
| Midwest vs West | 0.65 | 0.51, 0.83 | |
| Northeast vs West | 0.65 | 0.50, 0.83 | <0.0001 |
| South vs West | 0.77 | 0.62, 0.95 | |
| Age (per 10 years) | 0.88 | 0.84, 0.92 | <0.0001 |
Dexamethasone treatment
Of the 360 patients that met our criteria for treatment with dexamethasone, 148 (41%) received the drug as a primary treatment (i.e. no surgery was performed), while 212 patients (59%) received dexamethasone as an adjuvant treatment with surgery. On univariable analysis, younger age was strongly associated with likelihood of receiving dexamethasone (Table 4), both when used as a primary treatment and when used as an adjuvant treatment. None of the other factors studied were significantly associated with dexamethasone treatment.
Table 4:
Dexamethasone treatment for patients admitted with SDH
| Conservative management without dexamethasone (N=1907) | Conservative management with dexamethasone (N=148) | p-value | Surgery without adjuvant dexamethasone (N=1648) | Adjuvant Dexamethasone (N=212) | p-value | |
|---|---|---|---|---|---|---|
| Age in years, median (IQR) | 77 (65, 85) | 72 (60, 80) | 0.0002 | 72 (63, 81) | 69 (60, 78) | 0.004 |
| Race, N (%) | ||||||
| White | 1300 (68.2) | 110 (74.3) | 1076 (65.4) | 138 (65.1) | ||
| Black | 271 (14.2) | 16 (10.8) | 0.29 | 227 (13.8) | 26 (12.3) | 0.74 |
| Other | 334 (17.5) | 22 (14.9) | 342 (20.8) | 48 (22.6) | ||
| Unknown | 2 (0.1) | 0 | 3 (0.2) | 0 | ||
| Sex, N (%) | ||||||
| Female | 829 (43.5) | 53 (35.8) | 0.07 | 482 (29.2) | 69 (32.6) | 0.32 |
| Male | 1078 (56.5) | 95 (64.2) | 1166 (70.8) | 143 (67.4) | ||
| Care setting, N (%) | ||||||
| Nonacademic | 849 (44.5) | 56 (37.8) | 0.11 | 683 (41.4) | 97 (45.8) | 0.23 |
| Academic | 1058 (55.5) | 92 (62.2) | 965 (58.6) | 115 (54.2) | ||
| Region of United States, N (%) | ||||||
| Midwest | 375 (19.7) | 30 (20.3) | 294 (17.8) | 30 (14.2) | ||
| Northeast | 340 (17.8) | 22 (14.9) | 0.18 | 265 (16.1) | 32 (15.1) | 0.13 |
| South | 986 (51.7) | 87 (58.8) | 844 (51.2) | 126 (59.4) | ||
| West | 201 (10.8) | 9 (6.1) | 245 (14.9) | 24 (11.3) | ||
Discussion
In this large observational study of patients admitted for nontraumatic SDHs in the United States, we found that almost 48% of hospitalized patients underwent surgical management, which is higher than that reported in a prior study of nontraumatic SDH patients in the United States (39%).1 The reason for the higher rate in our study is unknown. Unlike in past population-level studies in the United States, we restricted our analysis to patients with nontraumatic SDH as a primary diagnosis, as a recent study in Europe found that the SDH codes were less reliable as secondary diagnoses.17 This may lead to a lower rate of case misclassification in our study, which could increase the surgical rate. Indeed, a study in Denmark found a surgery rate of 54% when restricting analysis to patients with SDH as a primary diagnosis.9 Restricting our analysis to patients with primary diagnoses of SDH may also exclude a subset of patients with smaller, less clinically significant SDHs.
On multivariable analysis, female sex, older age, and location outside of the west were all associated with a higher rate of surgical management. The different rates of surgical management may arise both from surgical decision-making and the underlying epidemiology of SDH. The effect of age on surgical management may in part result from surgeon preferences, as older age is well known to be a poor prognostic sign in SDH,18 leading some to argue for a higher threshold to operate in this patient group;19 older patients themselves may also prefer to avoid surgical management if conservative management is possible. It is also possible that older patients with smaller, nonsurgical SDHs are admitted to the hospital more commonly, whereas younger patients are more likely to be managed as an outpatient.
Female sex was a significant risk factor for nonsurgical management in our study, which has also been found in a prior single center study of SDH.20 It is well known that SDHs are much more common in men than women,1,9,17,21 although why women would be less likely to be managed surgically is unclear. Few studies have attempted to explore differences in the presentations and management of SDHs between men and women; a study from Japan suggested that women with chronic SDHs tended to be more functionally impaired at baseline and have worse neurological exams on presentation when compared with men,22 both of which might push a surgeon to prefer conservative management. Additionally, as many admissions for surgical management of nontraumatic SDH are elective,1 it is also possible that women prefer to avoid surgery if a conservative approach is possible, as has been seen with other elective surgeries.23 We do not believe this is solely the result of older age among women who present with nontraumatic SDHs, as female sex remained a significant predictor of nonsurgical management in a multivariable model that included age. Future studies should examine the effect of sex more closely on management and outcomes from SDHs.
Regional variation in surgical management of SDH in the United States has not previously been reported, although studies in other countries have shown considerable variation in management of acute traumatic SDHs across different centers.24 A study of the Nationwide Inpatient Sample found considerable variation in the intensity of neurosurgical care across the United States, even when controlling for the severity of patient illness on presentation;25 in general most regional variation in surgical practices is thought to be related to differing opinions about surgical indications and the extent to which patient preferences are incorporated into treatment decisions.26 Fundamental differences in the subtypes and severity of SDHs found in the West could also potentially explain these data, although no prior studies have demonstrated such a trend.
Our results suggest that dexamethasone is used frequently both as a primary treatment and as an adjuvant treatment in the management of patients with nontraumatic SDH. The lower likelihood of use among older patients may result from concerns about the side effects of high dose glucocorticoids in older patients;27 whether a different underlying epidemiology of SDH also contributes to this variability is unknown. By restricting our analysis to patients who receive multiple high doses of dexamethasone, we believe we are selecting primarily for neurological indications for steroid use; however, our study design does not allow for definitive confirmation of medication indications, and some patients in our study may have received dexamethasone for reasons apart from an SDH. Our study design also prevents us from assessing how frequently other medications are used to treat SDHs (e.g. other glucocorticoids, atorvastatin, and angiotensin converting enzyme inhibitors), as they are commonly used for non-neurological indications.
Many of the prior studies that have attempted to define surgical indications for SDHs have utilized single center data,28,29 and more recent studies have expanded the number of patients who can be managed conservatively.30 The extent to which surgical management varied across the demographic groups in our study emphasizes the need for prospective, multicenter studies to better understand the origin of this variation and to better clarify surgical indications. Efforts toward more population-level study have already been carried out with chronic SDHs in the United Kingdom, and have yielded new insights into ideal surgical practices.31 Of course, the developing evidence about the efficacy of medical therapies for chronic SDHs10,32 will also need to be considered as indications for surgical and conservative management are better clarified.
About 6% of surgically managed patients in our study required multiple SDH-related procedures. Many of these patients may have SDH recurrence, as symptomatic recurrence can occur early after drainage.33 Rates of symptomatic recurrence requiring reoperation have varied considerably across the literature, ranging from 2% to 30% depending on the surgical treatment and patient population studied. Our rate should be interpreted with caution, as our study design will miss patients that have symptomatic recurrence after discharge from the hospital. Additionally, some of the additional procedures performed may be for contralateral SDH or for inadequate drainage with the initial surgical approach.
Our study has significant limitations. First, there is a possibility of significant misclassification bias with using ICD codes to identify SDH cases, even with the fairly good evidence of their reliability.1,17 This misclassification bias is likely to be nondifferential across the factors studied, which could mean that we are underestimating the degree to which practice varies. A more significant limitation is that we cannot assess the severity or chronicity of SDHs in our study,17 both of which have significant impact on the decision for surgical management. As a result, we cannot rule out that the variation we observe in our data results from underlying differences in the epidemiology of nontraumatic SDHs across the demographics we studied. Finally, by limiting our study to patients who are managed as inpatients, we may be missing a significant number of SDH cases that are managed primarily as an outpatient.
Conclusion
In this study of nontraumatic SDH patients admitted to hospitals across the United States in 2014, we found considerable variation in the likelihood of being managed surgically based on age, sex, and region. Dexamethasone was used frequently both as a primary treatment modality and as an adjuvant to surgical management. Future studies should further explore the reasons for the variation in surgical management, and ultimately prospective randomized studies are needed to address indications for surgical and conservative management of SDHs.
Glossary
- SDH
Subdural hematoma
- ICD
International classification of diseases
- OR/aOR
Odds ratio, adjusted odds ratio
- CI
Confidence interval
Footnotes
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