Clinical and Imaging Characteristics, Care Pathways, and Outcomes of Traumatic Epidural Hematomas: A Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury Study.

BACKGROUND AND OBJECTIVES: Guideline recommendations for surgical management of traumatic epidural hematomas (EDHs) do not directly address EDHs that co-occur with other intracranial hematomas; the relative rates of isolated vs nonisolated EDHs and guideline adherence are unknown. We describe characteristics of a contemporary cohort of patients with EDHs and identify factors influencing acute surgery. METHODS: This research was conducted within the longitudinal, observational Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury cohort study which prospectively enrolled patients with traumatic brain injury from 65 hospitals in 18 European countries from 2014 to 2017. All patients with EDH on the first scan were included. We describe clinical, imaging, management, and outcome characteristics and assess associations between site and baseline characteristics and acute EDH surgery, using regression modeling. RESULTS: In 461 patients with EDH, median age was 41 years (IQR 24-56), 76% were male, and median EDH volume was 5 cm3 (IQR 2-20). Concomitant acute subdural hematomas (ASDHs) and/or intraparenchymal hemorrhages were present in 328/461 patients (71%). Acute surgery was performed in 99/461 patients (21%), including 70/86 with EDH volume ≥30 cm3 (81%). Larger EDH volumes (odds ratio [OR] 1.19 [95% CI 1.14-1.24] per cm3 below 30 cm3), smaller ASDH volumes (OR 0.93 [95% CI 0.88-0.97] per cm3), and midline shift (OR 6.63 [95% CI 1.99-22.15]) were associated with acute surgery; between-site variation was observed (median OR 2.08 [95% CI 1.01-3.48]). Six-month Glasgow Outcome Scale-Extended scores ≥5 occurred in 289/389 patients (74%); 41/389 (11%) died. CONCLUSION: Isolated EDHs are relatively infrequent, and two-thirds of patients harbor concomitant ASDHs and/or intraparenchymal hemorrhages. EDHs ≥30 cm3 are generally evacuated early, adhering to Brain Trauma Foundation guidelines. For heterogeneous intracranial pathology, surgical decision-making is related to clinical status and overall lesion burden. Further research should examine the optimal surgical management of EDH with concomitant lesions in traumatic brain injury, to inform updated guidelines.

Intravenous lidocaine attenuates distention of the optical nerve sheath, a correlate of intracranial pressure, during endotracheal intubation.

BACKGROUND: By preventing hypoxia and hypercapnia, advanced airway management can save lives among patients with traumatic brain injury. During endotracheal intubation (ETI), tracheal stimulation causes an increase in intracranial pressure (ICP), which may impair brain perfusion. It has been suggested that intravenous lidocaine might attenuate this ICP response. We hypothesized that adding lidocaine to the standard induction medication for general anesthesia might reduce the ICP response to ETI. Here, we measured the optical nerve sheath diameter (ONSD) as a correlate of ICP and evaluated the effect of intravenous lidocaine on ONSD during and after ETI in patients undergoing anesthesia. METHODS: This double-blinded, randomized placebo-controlled trial included 60 patients with American Society of Anesthesiologists I or II physical status that were scheduled for elective surgery under general anesthesia. In addition to the standard anesthesia medication, 30 subjects received 1.5 mg/kg 1% lidocaine (0.15 mL/kg, ONSD lidocaine) and 30 received 0.15 mL/kg 0.9% NaCl (ONSD placebo). ONSDs were measured with ultrasound on the left eye, before (T0), during (T1), and 4 times after ETI (T2-5 at 5-min intervals). RESULTS: Compared to placebo, lidocaine did not significantly affect the baseline ONSD after anesthesia induction measured at T0. During ETI, the ONSD lidocaine was significantly smaller (ß=-0.24 mm P=0.022) than the ONSD placebo. At T4 and T5, the ONSD placebo increased steadily, up to 20 min after ETI, but the ONSD lidocaine tended to return to baseline levels. CONCLUSIONS: We found that the ONSD was distended during and after ETI in anesthetized patients, and intravenous lidocaine attenuated this effect.

Impact of dedicated neuro-anesthesia management on clinical outcomes in glioblastoma patients: A single-institution cohort study.

BACKGROUND: Glioblastomas are mostly resected under general anesthesia under the supervision of a general anesthesiologist. Currently, it is largely unkown if clinical outcomes of GBM patients can be improved by appointing a neuro-anesthesiologist for their cases. We aimed to evaluate whether the assignment of dedicated neuro-anesthesiologists improves the outcomes of these patients. We also investigated the value of dedicated neuro-oncological surgical teams as an independent variable in both groups. METHODS: A cohort consisting of 401 GBM patients who had undergone resection was retrospectively investigated. Primary outcomes were postoperative neurological complications, fluid balance, length-of-stay and overall survival. Secondary outcomes were blood loss, anesthesia modality, extent of resection, total admission costs, and duration of surgery. RESULTS: 320 versus 81 patients were operated under the anesthesiological supervision of a general anesthesiologist and a dedicated neuro-anesthesiologist, respectively. Dedicated neuro-anesthesiologists yielded significant superior outcomes in 1) postoperative neurological complications (early: p = 0.002, OR = 2.54; late: p = 0.003, OR = 2.24); 2) fluid balance (p<0.0001); 3) length-of-stay (p = 0.0006) and 4) total admission costs (p = 0.0006). In a subanalysis of the GBM resections performed by an oncological neurosurgeon (n = 231), the assignment of a dedicated neuro-anesthesiologist independently improved postoperative neurological complications (early minor: p = 0.0162; early major: p = 0.00780; late minor: p = 0.00250; late major: p = 0.0364). The assignment of a dedicated neuro-oncological team improved extent of resection additionally (p = 0.0416). CONCLUSION: GBM resections with anesthesiological supervision of a dedicated neuro-anesthesiologists are associated with improved patient outcomes. Prospective evidence is needed to further investigate the usefulness of the dedicated neuro-anesthesiologist in different settings.

Comparative effectiveness of intracranial hypertension management guided by ventricular versus intraparenchymal pressure monitoring: a CENTER-TBI study.

OBJECTIVE: To compare outcomes between patients with primary external ventricular device (EVD)-driven treatment of intracranial hypertension and those with primary intraparenchymal monitor (IP)-driven treatment. METHODS: The CENTER-TBI study is a prospective, multicenter, longitudinal observational cohort study that enrolled patients of all TBI severities from 62 participating centers (mainly level I trauma centers) across Europe between 2015 and 2017. Functional outcome was assessed at 6 months and a year. We used multivariable adjusted instrumental variable (IV) analysis with "center" as instrument and logistic regression with covariate adjustment to determine the effect estimate of EVD on 6-month functional outcome. RESULTS: A total of 878 patients of all TBI severities with an indication for intracranial pressure (ICP) monitoring were included in the present study, of whom 739 (84%) patients had an IP monitor and 139 (16%) an EVD. Patients included were predominantly male (74% in the IP monitor and 76% in the EVD group), with a median age of 46 years in the IP group and 48 in the EVD group. Six-month GOS-E was similar between IP and EVD patients (adjusted odds ratio (aOR) and 95% confidence interval [CI] OR 0.74 and 95% CI [0.36-1.52], adjusted IV analysis). The length of intensive care unit stay was greater in the EVD group than in the IP group (adjusted rate ratio [95% CI] 1.70 [1.34-2.12], IV analysis). One hundred eighty-seven of the 739 patients in the IP group (25%) required an EVD due to refractory ICPs. CONCLUSION: We found no major differences in outcomes of patients with TBI when comparing EVD-guided and IP monitor-guided ICP management. In our cohort, a quarter of patients that initially received an IP monitor required an EVD later for ICP control. The prevalence of complications was higher in the EVD group. PROTOCOL: The core study is registered with ClinicalTrials.gov , number NCT02210221, and the Resource Identification Portal (RRID: SCR_015582).

Safety and efficacy of C1-inhibitor in traumatic brain injury (CIAO@TBI): study protocol for a randomized, placebo-controlled, multi-center trial.

BACKGROUND: Traumatic brain injury (TBI) is a major cause of death and disability across all ages. After the primary impact, the pathophysiologic process of secondary brain injury consists of a neuroinflammation response that critically leads to irreversible brain damage in the first days after the trauma. A key catalyst in this inflammatory process is the complement system. Inhibiting the complement system could therefore be a therapeutic target in TBI. OBJECTIVE: To study the safety and efficacy of C1-inhibitor (C1-INH) compared to placebo in patients with TBI. By temporarily blocking the complement system, we hypothesize a decrease in the posttraumatic neuroinflammatory response resulting in a less unfavorable clinical outcome for TBI patients. METHODS: CIAO@TBI is a multicenter, randomized, blinded, phase II placebo-controlled trial. Adult TBI patients with GCS < 13 requiring intracranial pressure (ICP) monitoring will be randomized, using block randomization, within 12 h after trauma to one dose 6000 IU C1-INH or placebo. A total of 106 patients will be included, and follow-up will occur up to 12 months. The primary endpoints are (1) Therapy Intensity Level (TIL) Scale, (2) Glasgow Outcome Scale-Extended (GOSE) at 6 months, and (3) complication rate during hospitalization. Outcomes will be determined by a trial nurse blinded for the treatment allocation. Analyses will be conducted in an intention-to-treat analysis. DISCUSSION: We expect that C1-INH administration will be safe and potentially effective to improve clinical outcomes by reducing neuroinflammation in TBI patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT04489160. Registered on 27 July 2020. EudraCT 2020-000140-58.

Intraoperative B-Mode Ultrasound Guided Surgery and the Extent of Glioblastoma Resection: A Randomized Controlled Trial.

BACKGROUND: Intraoperative MRI and 5-aminolaevulinic acid guided surgery are useful to maximize the extent of glioblastoma resection. Intraoperative ultrasound is used as a time-and cost-effective alternative, but its value has never been assessed in a trial. The goal of this randomized controlled trial was to assess the value of intraoperative B-mode ultrasound guided surgery on the extent of glioblastoma resection. MATERIALS AND METHODS: In this randomized controlled trial, patients of 18 years or older with a newly diagnosed presumed glioblastoma, deemed totally resectable, presenting at the Erasmus MC (Rotterdam, The Netherlands) were enrolled and randomized (1:1) into intraoperative B-mode ultrasound guided surgery or resection under standard neuronavigation. The primary outcome of this study was complete contrast-enhancing tumor resection, assessed quantitatively by a blinded neuroradiologist on pre- and post-operative MRI scans. This trial was registered with ClinicalTrials.gov (NCT03531333). RESULTS: We enrolled 50 patients between November 1, 2016 and October 30, 2019. Analysis was done in 23 of 25 (92%) patients in the intraoperative B-mode ultrasound group and 24 of 25 (96%) patients in the standard surgery group. Eight (35%) of 23 patients in the intraoperative B-mode ultrasound group and two (8%) of 24 patients in the standard surgery group underwent complete resection (p=0.036). Baseline characteristics, neurological outcome, functional performance, quality of life, complication rates, overall survival and progression-free survival did not differ between treatment groups (p>0.05). CONCLUSIONS: Intraoperative B-mode ultrasound enables complete resection more often than standard surgery without harming patients and can be considered to maximize the extent of glioblastoma resection during surgery.

Traumatic axonal injury (TAI): definitions, pathophysiology and imaging-a narrative review.

INTRODUCTION: Traumatic axonal injury (TAI) is a condition defined as multiple, scattered, small hemorrhagic, and/or non-hemorrhagic lesions, alongside brain swelling, in a more confined white matter distribution on imaging studies, together with impaired axoplasmic transport, axonal swelling, and disconnection after traumatic brain injury (TBI). Ever since its description in the 1980s and the grading system by Adams et al., our understanding of the processes behind this entity has increased. METHODS: We performed a scoping systematic, narrative review by interrogating Ovid MEDLINE, Embase, and Google Scholar on the pathophysiology, biomarkers, and diagnostic tools of TAI patients until July 2020. RESULTS: We underline the misuse of the Adams classification on MRI without proper validation studies, and highlight the hiatus in the scientific literature and areas needing more research. In the past, the theory behind the pathophysiology relied on the inertial force exerted on the brain matter after severe TBI inducing a primary axotomy. This theory has now been partially abandoned in favor of a more refined theory involving biochemical processes such as protein cleavage and DNA breakdown, ultimately leading to an inflammation cascade and cell apoptosis, a process now described as secondary axotomy. CONCLUSION: The difference in TAI definitions makes the comparison of studies that report outcomes, treatments, and prognostic factors a daunting task. An even more difficult task is isolating the outcomes of isolated TAI from the outcomes of severe TBI in general. Targeted bench-to-bedside studies are required in order to uncover further pathways involved in the pathophysiology of TAI and, ideally, new treatments.

Hyperoxia in pediatric severe traumatic brain injury (TBI): a comparison of patient classification by cutoff versus cumulative (area-under-the-curve) analysis.

OBJECTIVE: Hyperoxia is associated with adverse outcome in severe traumatic brain injury (TBI). This study explored differences in patient classification of oxygen exposure by PaO2 cutoff and cumulative area-under-the-curve (AUC) analysis. METHODS: Retrospective, explorative study including children (<18 years) with accidental severe TBI (2002-2015). Oxygen exposure analysis used three PaO2 cutoff values and four PaO2 AUC categories during the first 24 hours of Pediatric Intensive Care Unit (PICU) admission. RESULTS: Seventy-one patients were included (median age 8.9 years [IQR 4.6-12.9]), mortality 18.3% (n = 13). Patient hyperoxia classification differed depending on PaO2 cutoff vs AUC analysis: 52% vs. 26%, respectively, were classified in the highest hyperoxia category. Eleven patients (17%) classified as 'intermediate oxygen exposure' based on cumulative PaO2 analysis whereby they did not exceed the 200 mmHg PaO2 cutoff threshold. Patient classification variability was reflected by Pearson correlation coefficient of 0.40 (p-value 0.001). CONCLUSIONS: Hyperoxia classification in pediatric severe TBI during the first 24 hours of PICU admission differed depending on PaO2 cutoff or cumulative AUC analysis. We consider PaO2 cumulative (AUC) better approximates (patho-)physiological circumstances due to its time- and dose-dependent approach. Prospective studies exploring the association between cumulative PaO2, physiological parameters (e.g. ICP, PbtO2) and outcome are warranted as different patient classifications of oxygen exposure influences how its relationship to outcome is interpreted.

Evolution of Evidence and Guideline Recommendations for the Medical Management of Severe Traumatic Brain Injury.

Brain Trauma Foundation (BTF) Guidelines for medical management of severe traumatic brain injury (TBI) have become a global standard for the treatment of TBI patients. We aim to explore the evolution of the guidelines for the management of severe TBI. We reviewed the four editions of the BTF guidelines published over the past 20 years. The 1996 and 2000 editions were merged because of minimal differences, and are referred to as the 1996 edition. We described changes in topics and recommendations over time, and analyzed predictors of survival of recommendations with logistical regression. The guidelines contained 27 recommendations on 18 topics in 2016, 35 recommendations on 15 topics in 2007, and 22 recommendations on 10 topics in 1996. Substantial delays were found between the search for evidence and the guideline publication, ranging from 18 to 34 months. The overall body of evidence comprised 189 studies on 18 topics in 2016, compared with 156 studies on 15 topics in 2007 and 180 studies on 10 topics in 1996. Over time, a total of 175 studies were discarded from the evidence base following more rigorous grading of evidence. A total of 15/23 (65%) of the 1996/2000 recommendations were discarded over time. Out of 12 new recommendations introduced in the 2007 edition, 8 (66%) were discarded in 2016. Survival of recommendations varied between 33% and 100% for level I recommendations and between 11% and 31% for level II and III recommendations. No predictors of survival of recommendations were found. Substantial delays exist between literature search and publication, and survival rate of TBI guideline recommendations is poor. These factors may adversely affect currency and adherence to guidelines. The TBI community should take responsibility for improving the quality of the evidence base and ensuring that the translation of the evidence into guidelines supports clinicians in daily clinical practice.

Variation in Guideline Implementation and Adherence Regarding Severe Traumatic Brain Injury Treatment: A CENTER-TBI Survey Study in Europe.

OBJECTIVE: Guidelines may reduce practice variation and optimize patient care. We aimed to study differences in guideline use in the management of traumatic brain injury (TBI) patients and analyze reasons for guideline non-adherence. METHODS: As part of a prospective, observational, multicenter European cohort study, participants from 68 centers in 20 countries were asked to complete 72-item questionnaires regarding their management of severe TBI. Six questions with multiple sub-questions focused on guideline use and implementation. RESULTS: Questionnaires were completed by 65 centers. Of these, 49 (75%) reported use of the Brain Trauma Foundation guidelines for the medical management of TBI or related institutional protocols, 11 (17%) used no guidelines, and 5 used other guidelines (8%). Of 54 centers reporting use of any guidelines, 41 (75%) relied on written guidelines. Four centers of the 54 (7%) reported no formal implementation efforts. Structural attention to the guidelines during daily clinical rounds was reported by 21 centers (38%). The most often reported reasons for non-adherence were "every patient is unique" and the presence of extracranial injuries, both for centers that did and did not report the use of guidelines. CONCLUSIONS: There is substantial variability in the use and implementation of guidelines in neurotrauma centers in Europe. Further research is needed to strengthen the evidence underlying guidelines and to overcome implementation barriers.

Correction to: Variation in neurosurgical management of traumatic brain injury: a survey in 68 centers participating in the CENTER-TBI study.

The collaborator names are inverted.

Ventricular Drainage Catheters versus Intracranial Parenchymal Catheters for Intracranial Pressure Monitoring-Based Management of Traumatic Brain Injury: A Systematic Review and Meta-Analysis.

Intracranial pressure (ICP) monitoring is one of the mainstays in the treatment of severe traumatic brain injury (TBI), but different approaches to monitoring exist. The aim of this systematic review and meta-analysis is to compare the effectiveness and complication rate of ventricular drainage (VD) versus intracranial parenchymal (IP) catheters to monitor and treat raised ICP in patients with TBI. Pubmed, Embase, Web of Science, Google Scholar, and the Cochrane Database were searched for articles comparing ICP monitoring-based management with VDs and monitoring with IP monitors through March 2018. Study selection, data extraction, and quality assessment were performed independently by two authors. Outcomes assessed were mortality, functional outcome, need for decompressive craniectomy, length of stay, overall complications, such as infections, and hemorrhage. Pooled effect estimates were calculated with random effects models and expressed as relative risk (RR) for dichotomous outcomes and mean difference (MD) for ordinal outcomes, with corresponding 95% confidence intervals (CI). Six studies were included: one randomized controlled trial and five observational cohort studies. Three studies reported mortality, functional outcome, and the need for a surgical decompression, and three only reported complications. The quality of the studies was rated as poor, with critical or serious risk of bias. The pooled analysis did not show a statistically significant difference in mortality (RR = 0.90, 95% CI = 0.60-1.36, p = 0.41) or functional outcome (MD = 0.23, 95% CI = 0.67-1.13, p = 0.61). The complication rate of VDs was higher (RR = 2.56, 95% CI = 1.17-5.61, p = 0.02), and consisted mainly of infectious complications; that is, meningitis. VDs caused more complications, particularly more infections, but there was no difference in mortality or functional outcome between the two monitoring modalities. However, the studies had a high risk of bias. A need exists for high quality comparisons of VDs versus IP monitor-based management strategies on patient outcomes.

Intensive care admission criteria for traumatic brain injury patients across Europe.

Within a prospective, observational, multi-center cohort study 68 hospitals (of which 66 responded), mostly academic (n = 60, 91%) level I trauma centers (n = 44, 67%) in 20 countries were asked to complete questionnaires regarding the "standard of care" for severe neurotrauma patients in their hospitals. From the questionnaire pertaining to ICU management, 12 questions related to admission criteria were selected for this analysis. The questionnaires were completed by 66 centers. The median number of TBI patients admitted to the ICU was 92 [interquartile range (IQR): 52-160] annually. Admission policy varied; in 45 (68%) centers, patients with a Glasgow Come Score (GCS) between 13 and 15 without CT abnormalities but with other risk factors would be admitted to the ICU while the rest indicated that they would not admit these patients routinely to the ICU. We found no association between ICU admission policy and the presence of a dedicated neuro ICU, the discipline in charge of rounds, the presence of step down beds or geographic location (North- Western Europe vs. South - Eastern Europe and Israel). Variation in admission policy, primarily of mild TBI patients to ICU exists, even among high-volume academic centers and seems to be largely independent of other center characteristics. The observed variation suggests a role for comparative effectiveness research to investigate the potential benefit and cost-effectiveness of a liberal versus more restrictive admission policies.

Variation in neurosurgical management of traumatic brain injury: a survey in 68 centers participating in the CENTER-TBI study.

BACKGROUND: Neurosurgical management of traumatic brain injury (TBI) is challenging, with only low-quality evidence. We aimed to explore differences in neurosurgical strategies for TBI across Europe. METHODS: A survey was sent to 68 centers participating in the Collaborative European Neurotrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study. The questionnaire contained 21 questions, including the decision when to operate (or not) on traumatic acute subdural hematoma (ASDH) and intracerebral hematoma (ICH), and when to perform a decompressive craniectomy (DC) in raised intracranial pressure (ICP). RESULTS: The survey was completed by 68 centers (100%). On average, 10 neurosurgeons work in each trauma center. In all centers, a neurosurgeon was available within 30 min. Forty percent of responders reported a thickness or volume threshold for evacuation of an ASDH. Most responders (78%) decide on a primary DC in evacuating an ASDH during the operation, when swelling is present. For ICH, 3% would perform an evacuation directly to prevent secondary deterioration and 66% only in case of clinical deterioration. Most respondents (91%) reported to consider a DC for refractory high ICP. The reported cut-off ICP for DC in refractory high ICP, however, differed: 60% uses 25 mmHg, 18% 30 mmHg, and 17% 20 mmHg. Treatment strategies varied substantially between regions, specifically for the threshold for ASDH surgery and DC for refractory raised ICP. Also within center variation was present: 31% reported variation within the hospital for inserting an ICP monitor and 43% for evacuating mass lesions. CONCLUSION: Despite a homogeneous organization, considerable practice variation exists of neurosurgical strategies for TBI in Europe. These results provide an incentive for comparative effectiveness research to determine elements of effective neurosurgical care.

Efficacy and Safety of switching to Pasireotide in Acromegaly Patients controlled with Pegvisomant and Somatostatin Analogues: PAPE extension study.

OBJECTIVE: to assess the efficacy and safety after 48 weeks of treatment with pasireotide long-acting-release (PAS-LAR) alone or in combination with pegvisomant in patients with acromegaly. In addition, we assessed the relation between insulin secretion and pasireotide-induced hyperglycemia. DESIGN: The PAPE extension study is a prospective follow-up study until 48 weeks after the core study of 24 weeks. METHODS: 59 out of 61 patients entered the extension study. Efficacy was defined as the percentage of patients achieving IGF-I normalization (≤ 1.2 x the Upper Limit of Normal (ULN)) at 48-weeks through protocol-based adjustment of pegvisomant and PAS-LAR doses. At baseline, insulin secretion was assessed by an oral glucose tolerance test (OGTT). RESULTS: At the end of the study median IGF-I was 0.98 x ULN, and 77% of patients achieved normal IGF-I levels with a mean pegvisomant dose of 64 mg/week, and an overall cumulative pegvisomant dose reduction of 52%. Frequency of diabetes mellitus increased from 68% at 24 weeks to 77% at 48 weeks, and 9 patients discontinued PAS-LAR treatment, mainly because of severe hyperglycemia. Pasireotide-induced hyperglycemia was inversely correlated with baseline insulin secretion (r = -0.37, P < 0.005). CONCLUSIONS: PAS-LAR normalizes IGF-I levels in most acromegaly patients, with a fifty percent pegvisomant-sparing effect. However, PAS-LAR treatment coincided with a high incidence of diabetes mellitus. The risk for developing diabetes during PAS-LAR treatment seems inversely related to insulin secretion at baseline.

Adjusting for confounding by indication in observational studies: a case study in traumatic brain injury.

INTRODUCTION: Observational studies of interventions are at risk for confounding by indication. The objective of the current study was to define the circumstances for the validity of methods to adjust for confounding by indication in observational studies. PATIENTS AND METHODS: We performed post hoc analyses of data prospectively collected from three European and North American traumatic brain injury studies including 1,725 patients. The effects of three interventions (intracranial pressure [ICP] monitoring, intracranial operation and primary referral) were estimated in a proportional odds regression model with the Glasgow Outcome Scale as ordinal outcome variable. Three analytical methods were compared: classical covariate adjustment, propensity score matching and instrumental variable (IV) analysis in which the percentage exposed to an intervention in each hospital was added as an independent variable, together with a random intercept for each hospital. In addition, a simulation study was performed in which the effect of a hypothetical beneficial intervention (OR 1.65) was simulated for scenarios with and without unmeasured confounders. RESULTS: For all three interventions, covariate adjustment and propensity score matching resulted in negative estimates of the treatment effect (OR ranging from 0.80 to 0.92), whereas the IV approach indicated that both ICP monitoring and intracranial operation might be beneficial (OR per 10% change 1.17, 95% CI 1.01-1.42 and 1.42, 95% CI 0.95-1.97). In our simulation study, we found that covariate adjustment and propensity score matching resulted in an invalid estimate of the treatment effect in case of unmeasured confounders (OR ranging from 0.90 to 1.03). The IV approach provided an estimate in the similar direction as the simulated effect (OR per 10% change 1.04-1.05) but was statistically inefficient. CONCLUSION: The effect estimation of interventions in observational studies strongly depends on the analytical method used. When unobserved confounding and practice variation are expected in observational multicenter studies, IV analysis should be considered.