The National Inpatient Sample: A Primer for Neurosurgical Big Data Research and Systematic Review

Evidence Against a Traumatic Brain Injury "July Effect": An Analysis of 3 160 452 Patients From the National Inpatient Sample

BACKGROUND AND OBJECTIVES

The "July Effect" hypothesizes increased morbidity and mortality after the addition of inexperienced physicians at the beginning of an academic year. However, the impact of newer members on neurosurgical teams managing patients with traumatic brain injury (TBI) has yet to be examined. This study conducted a nationwide analysis to evaluate the existence of the "July Effect" in the setting of patients with TBI.

METHODS

The Healthcare Cost and Utilization Project Central Distributor's National Inpatient Sample data set was queried for patients with TBI using International Classification of Diseases (ICD)-9 and ICD-10 codes. Discharges were included for diagnoses of traumatic epidural, subdural, or subarachnoid hemorrhages. Only patients treated at teaching hospitals were included to ensure resident involvement in care. Patients were grouped into July admission and non-July admission cohorts. A subgroup of patients with neurotrauma undergoing any form of cranial surgery was created. Perioperative variables were recorded. Rates of different complications were assayed. Groups were compared using χ2 tests (qualitative variables) and t-tests or Mann-Whitney U-tests (quantitative variables). Logistic regression was used for binary variables. Gamma log-linked regression was used for continuous variables.

RESULTS

The National Inpatient Sample database yielded a weighted average of 3 160 452 patients, of which 312 863 (9.9%) underwent surgical management. Patients admitted to the hospital in July had a 5% decreased likelihood of death (P = .027), and a 5.83% decreased likelihood of developing a complication (P < .001) compared with other months of the year. July admittance to a hospital showed no significant impact on mean length of stay (P = .392) or routine discharge (P = .147). Among patients with TBI who received surgical intervention, July admittance did not significantly affect the likelihood of death (P = .053), developing a complication (P = .477), routine discharge (P = .986), or mean length of stay (P = .385).

CONCLUSION

The findings suggested that there is no "July Effect" on patients with TBI treated at teaching hospitals in the United States.

Risk Analysis Index Predicts Nonhome Discharge Following Resection of Cavernous Malformations

OBJECTIVE

Intracranial cavernous malformations (CMs) are benign vascular lesions associated with hemorrhage, seizures, and corresponding neurological deficits. Recent evidence shows that frailty predicts neurosurgical adverse outcomes with superior discrimination compared to greater patient age. Therefore, we utilized the Risk Analysis Index (RAI) to predict adverse outcomes following cavernous malformation resection (CMR).

METHODS

This retrospective study utilized the Nationwide Inpatient Sample to identify patients who underwent craniotomy for CMR (2019-2020). Multivariate analysis used RAI to assess the ability of frailty to predict nonhome discharge (NHD), extended length of stay (eLOS), and postoperative adverse outcomes. Receiver operating characteristic curve analysis evaluated the discriminatory accuracy of RAI for prediction of NHD.

RESULTS

One thousand two hundred CMR patients were identified. Mean patient age was 38±1.2 years, 53.3% (N=640) were female, and 58.3% (N=700) had private insurance. Patients were stratified into 4 frailty tiers based on RAI scores: "robust" (0-20, R), N=905 (80.8%); "normal" (21-30, N), N=110 (9.8%); "frail" (31-40, F), N=25 (2.2%); and "very frail" (41+, VF), N = 80 (7.1%). Increasing frailty was associated with eLOS and higher rates of NHD (P<0.05). The RAI demonstrated strong discriminatory accuracy (C-statistic=0.722) for prediction of NHD following CMR in area under the receiver operating characteristics.

CONCLUSIONS

Preoperative frailty independently predicts adverse outcomes, including eLOS and NHD in patients undergoing resection of cranial CMs. Integrating RAI into preoperative frailty risk assessment may optimize risk stratification and improve patient selection and reallocate perioperative management resources for better patient outcomes.

Identifying inpatient hospitalizations with continuous electroencephalogram monitoring from administrative data

BACKGROUND

Continuous electroencephalography (cEEG) is increasingly utilized in hospitalized patients to detect and treat seizures. Epidemiologic and observational studies using administrative datasets can provide insights into the comparative and cost effectiveness of cEEG utilization. Defining patient cohorts that underwent acute inpatient cEEG from administrative datasets is limited by the lack of validated codes differentiating elective epilepsy monitoring unit (EMU) admissions from acute inpatient hospitalization with cEEG utilization. Our aim was to develop hospital administrative data-based models to identify acute inpatient admissions with cEEG monitoring and distinguish them from EMU admissions.

METHODS

This was a single center retrospective cohort study of adult (≥ 18 years old) inpatient admissions with a cEEG procedure (EMU or acute inpatient) between January 2016-April 2022. The gold standard for acute inpatient cEEG vs. EMU was obtained from the local EEG recording platform. An extreme gradient boosting model was trained to classify admissions as acute inpatient cEEG vs. EMU using administrative data including demographics, diagnostic and procedure codes, and medications.

RESULTS

There were 9,523 patients in our cohort with 10,783 hospital admissions (8.5% EMU, 91.5% acute inpatient cEEG); with average age of 59 (SD 18.2) years; 46.2% were female. The model achieved an area under the receiver operating curve of 0.92 (95% CI [0.91-0.94]) and area under the precision-recall curve of 0.99 [0.98-0.99] for classification of acute inpatient cEEG.

CONCLUSIONS

Our model has the potential to identify cEEG monitoring admissions in larger cohorts and can serve as a tool to enable large-scale, administrative data-based studies of EEG utilization.

Predictors of Prolonged Length of Stay After Pituitary Adenoma Resection: A Large Cohort Analysis Using the National Inpatient Sample (2016-2019)

OBJECTIVE

In this nationwide retrospective study, the authors aimed to identify demographic, clinical, and baseline health risk factors predictive of a prolonged length of stay (PLOS) for patients with pituitary adenomas (PAs).

METHODS

The National Inpatient Sample dataset from 2016 to 2019 was utilized to identify all included hospitalizations for PA resection as identified by the appropriate diagnosis-related group code. Comorbidities were classified based on the Charlson Comorbidity Index mapping of ICD-10 codes, and PLOS was identified as any stay longer than 3 days. Univariable and multivariable logistic regression models, accounting for the sample design, were built to determine factors associated with PLOS and emergent surgery.

RESULTS

Overall, 30 945 patients were included in this study with 10 535 patients having PLOS. Female patients experienced an increased odds of PLOS (odds ratio [OR]: 1.29; P < .001). Black patients (OR: 1.49; P < .001) and Hispanic patients (OR: 1.30; P = .003) had 1.49 times and 1.30 times the odds of PLOS compared to White patients, respectively. Compared to patients insured by Medicare, patients insured by Medicaid had an increased odds of PLOS (OR: 1.36; P = .007) as well as emergent surgery (OR: 5.40; P < .001). When stratified by emergent surgeries, Black patients (OR: 1.89; P < .001), Hispanic patients, (OR: 2.14; P < .001), and patients on Medicaid insurance (OR: 1.71; P < .001) were at an increased risk of emergent procedures. However, female sex (OR: 0.65; P < .001), upper third quartile (OR: 0.73; P = .017), and fourth quartile (OR: 0.69; P = .014) of patients categorized by zip code income were at decreased odds of an emergent procedure.

CONCLUSIONS

Black and Hispanic patients, patients with Medicaid insurance, and patients of low socioeconomic status patients are at significantly higher risk of emergent PA resection and PLOS. Efforts to prevent emergent surgeries and shorten hospitalization after pituitary surgery may need to primarily focus on patient groups with select sociodemographic characteristics.

Changes in deep brain stimulation surgeries between 2019 and 2020: A national inpatient sample analysis

Background

Deep brain stimulation (DBS) surgery is a neurosurgical procedure that implants electrodes into the brain to treat a variety of neurological and psychiatric conditions. The COVID-19 pandemic resulted in significant disruptions in elective surgeries, but the impact on DBS surgeries remains largely unknown.

Methods

The National Inpatient Sample (NIS), an all-payors database of inpatient hospitalizations in the US, was queried for DBS implantation procedural codes in 2019 and 2020.

Results

There were a total of 7,625 hospitalizations (95% CI: 6,664 to 8,586) for the implantation of a DBS lead in the 2019 NIS, which reduced by 11.9% to 6,715 hospitalizations (95% CI: 5,872 to 7,558) in the 2020 NIS. Procedural numbers declined in March 2020, with a peak 92.7% decline in volume in April of 2020 relative to 2019. Case numbers for July through December 2020 were 96.1% of the 2019 volume. Overall patient demographics and primary discharge diagnoses for hospitalizations involving DBS implantation were similar in the two study years.

Conclusions

Surgical volume for DBS implantation reduced by 92.7% in April of 2020 relative to 2019, which is among the highest declines reported for any surgical procedure. While procedural volume increased in the second half of 2020, this did not make up for the reduction in procedures earlier in the year, highlighting the disruption in DBS surgeries in 2020.

RAI-measured frailty predicts non-home discharge following metastatic brain tumor resection: national inpatient sample analysis of 20,185 patients

PURPOSE

Preoperative risk stratification for patients undergoing metastatic brain tumor resection (MBTR) is based on established tumor-, patient-, and disease-specific risk factors for outcome prognostication. Frailty, or decreased baseline physiologic reserve, is a demonstrated independent risk factor for adverse outcomes following MBTR. The present study sought to assess the impact of frailty, measured by the Risk Analysis Index (RAI), on MBTR outcomes.

METHODS

All MBTR were queried from the National Inpatient Sample (NIS) from 2019 to 2020 using diagnosis and procedural codes. The relationship between preoperative RAI frailty score and our primary outcome - non-home discharge (NHD) - and secondary outcomes - complication rates, extended length of stay (eLOS), and mortality - were analyzed via univariate and multivariable analyses. Discriminatory accuracy was tested by computation of concordance statistics in area under the receiver operating characteristic (AUROC) curve analysis.

RESULTS

There were 20,185 MBTR patients from the NIS database from 2019 to 2020. Each patient's frailty status was stratified by RAI score: 0-20 (robust): 34%, 21-30 (normal): 35.1%, 31-40 (very frail): 13.9%, 41+ (severely frail): 16.8%. Compared to robust patients, severely frail patients demonstrated increased complication rates (12.2% vs. 6.8%, p < 0.001), eLOS (37.6% vs. 13.2%, p < 0.001), NHD (52.0% vs. 20.6%, p < 0.001), and mortality (9.9% vs. 4.1%, p < 0.001). AUROC curve analysis demonstrated good discriminatory accuracy of RAI-measured frailty in predicting NHD after MBTR (C-statistic = 0.67).

CONCLUSION

Increasing RAI-measured frailty status is significantly associated with increased complication rates, eLOS, NHD, and mortality following MBTR. Preoperative frailty assessment using the RAI may aid in preoperative surgical planning and risk stratification for patient selection.

Age- and Sex-Specific Trends in Medical Complications After Acute Ischemic Stroke in the United States

BACKGROUND AND OBJECTIVES

To test the hypothesis that the age and sex-specific prevalence of infectious (pneumonia, sepsis, and urinary tract infection [UTI]) and noninfectious (deep venous thrombosis [DVT], pulmonary embolism [PE], acute renal failure [ARF], acute myocardial infarction [AMI], and gastrointestinal bleeding [GIB]) complications increased after acute ischemic stroke (AIS) hospitalization in the United States from 2007 to 2019.

METHODS

We conducted a serial cross-sectional study using the 2007-2019 National Inpatient Sample. Primary AIS admissions in adults (aged 18 years or older) with and without complications were identified using International Classification of Diseases codes. We quantified the age/sex-specific prevalence of complications and used negative binomial regression models to evaluate trends over time.

RESULTS

Of 5,751,601 weighted admissions, 51.4% were women. 25.1% had at least 1 complication. UTI (11.8%), ARF (10.1%), pneumonia (3.2%), and AMI (2.5%) were the most common complications, while sepsis (1.7%), GIB (1.1%), DVT (1.2%), and PE (0.5%) were the least prevalent. Marked disparity in complication risk existed by age/sex (UTI: men 18-39 years 2.1%; women 80 years or older 22.5%). Prevalence of UTI (12.9%-9.7%) and pneumonia (3.8%-2.7%) declined, but that of ARF increased by ≈3-fold (4.8%-14%) over the period 2007-2019 (all p < 0.001). AMI (1.9%-3.1%), DVT (1.0%-1.4%), and PE (0.3%-0.8%) prevalence also increased (p < 0.001), but that of sepsis and GIB remained unchanged over time. After multivariable adjustment, risk of all complications increased with increasing NIH Stroke Scale (pneumonia: prevalence rate ratio [PRR] 1.03, 95% CI 1.03-1.04, for each unit increase), but IV thrombolysis was associated with a reduced risk of all complications (pneumonia: PRR 0.80, 85% CI 0.73-0.88; AMI: PRR 0.85, 95% CI 0.78-0.92; and DVT PRR 0.87, 95% CI 0.78-0.98). Mechanical thrombectomy was associated with a reduced risk of UTI, sepsis, and ARF, but DVT and PE were more prevalent in MT hospitalizations compared with those without. All complications except UTI were associated with an increased risk of in-hospital mortality (sepsis: PRR 1.97, 95% CI 1.78-2.19).

DISCUSSION

Infectious complications declined, but noninfectious complications increased after AIS admissions in the United States in the last decade. Utilization of IV thrombolysis is associated with a reduced risk of all complications.

Maximal safe resection of diffuse lower grade gliomas primarily within central lobe using cortical/subcortical direct electrical stimulation under awake craniotomy

Background

Diffuse lower-grade glioma (DLGG) in the central lobe is a challenge for safe resection procedures. To improve the extent of resection and reduce the risk of postoperative neurological deficits, we performed an awake craniotomy with cortical-subcortical direct electrical stimulation (DES) mapping for patients with DLGG located primarily within the central lobe. We investigated the outcomes of cortical-subcortical brain mapping using DES in an awake craniotomy for central lobe DLGG resection.

Methods

We performed a retrospective analysis of clinical data of a cohort of consecutively treated patients from February 2017 to August 2021 with diffuse lower-grade gliomas located primarily within the central lobe. All patients underwent awake craniotomy with DES for cortical and subcortical mapping of eloquent brain areas, neuronavigation, and/or ultrasound to identify tumor location. Tumors were removed according to functional boundaries. Maximum safe tumor resection was the surgical objective for all patients.

Results

Thirteen patients underwent 15 awake craniotomies with intraoperative mapping of eloquent cortices and subcortical fibers using DES. Maximum safe tumor resection was achieved according to functional boundaries in all patients. The pre-operative tumor volumes ranged from 4.3 cm³ to 137.3 cm³ (median 19.2 cm³). The mean extent of tumor resection was 94.6%, with eight cases (53.3%) achieving total resection, four (26.7%) subtotal and three (20.0%) partial. The mean tumor residue was 1.2 cm³. All patients experienced early postoperative neurological deficits or worsening conditions. Three patients (20.0%) experienced late postoperative neurological deficits at the 3-month follow-up, including one moderate and two mild neurological deficits. None of the patients experienced late onset severe neurological impairments post-operatively. Ten patients with 12 tumor resections (80.0%) had resumed activities of daily living at the 3-month follow-up. Among 14 patients with pre-operative epilepsy, 12 (85.7%) were seizure-free after treatment with antiepileptic drugs 7 days after surgery up to the last follow-up.

Conclusions

DLGG located primarily in the central lobe deemed inoperable can be safely resected using awake craniotomy with intraoperative DES without severe permanent neurological sequelae. Patients experienced an improved quality of life in terms of seizure control.