Postoperative elevated bed header position versus supine in the management of chronic subdural hematoma: a systematic review and meta-analysis

Background Chronic subdural hematoma (CSDH) is a prevalent type of intracranial hemorrhage. Surgical interventions, such as Twist Drill Craniostomy and Burr Hole Craniostomy, are employed for its treatment. However, limited information exists regarding the impact of postoperative head position (supine vs. elevated) on clinical outcomes. We aim to assess whether patients’ head position after surgery influences their prognosis. Method We conducted a PRISMA-compliant systematic review and meta-analysis. Our search encompassed PubMed, Cochrane CENTRAL, Scopus, Web of Science, and Embase databases to identify relevant published studies. Data were meticulously extracted, pooled using a fixed model, and reported as risk ratios (RR) with 95% confidence intervals (CI). Statistical analysis was performed using R and Stata MP v.17. Results Five studies involving 284 patients were included in our meta-analysis. We focused on three primary clinical outcomes, comparing the supine and elevated header positions. Notably, there was no statistically significant difference between the supine and elevated positions in terms of recurrence rate (RR 0.77, 95% CI [0.44, 1.37]), second intervention for recurrence (RR 1.07, 95% CI [0.42, 2.78]) and postoperative complications (RR 1.16, 95% CI [0.70, 1.92]). Conclusion Current studies have proved no difference between supine and elevated bed header positions regarding recurrence rate, second intervention for recurrence, and postoperative complications. Future RCTs with long-term follow-ups are recommended.


Introduction
Chronic subdural hematoma (CSDH) is a common intracranial hemorrhage seen predominantly in older adults.As the population ages and anticoagulant medication usage becomes more widespread, the incidence of CSDH is on the rise [1,2].The annual occurrence of CSDH in the adult population varies from 1.7 to 16.3 cases per 100,000 individuals [3,4].Clinically, CSDH is characterized by a collection of blood or its breakdown products between the brain and the dura mater, persisting for at least 21 days [5].Recurrence rates range from 9.2 to 26.5% [6][7][8][9][10][11].
Management strategies for CSDH include various surgical approaches, such as twist drill craniostomy with closed system drainage (TDC-CSD) and Burr Hole Craniostomy [4].While these interventions have demonstrated longstanding success, there remains limited knowledge regarding the impact of head position (flat/supine vs. elevated/ reverse Trendelenburg) on procedural efficacy and overall patient outcomes.
Craniostomy, a common surgical procedure for CSDH, is typically performed with the patient in a semi-lateral or supine position [12].The head can be kept neutral or rotated, depending on the location of the lesion [12].During this procedure, it is crucial to position the burr hole near the vertex of the head.Improper head posture during burr hole creation may lead to the accumulation of significant subdural air [12,13].
CSDH often occurs alongside cerebral atrophy, increasing potential space within the subdural area.To facilitate drainage and reduce this potential space, some neurosurgeons advocate flattening the patient's head and adjusting the head end of the bed.However, an alternative approach involves elevating the head end of the bed.This technique, borrowed from the management of acute subdural hematomas, aims to decrease intracranial pressure and is also applied to CSDH patients [14].
The growth of CSDH involves complex mechanisms that continue to be debated.Two main hypotheses shed light on its pathogenesis: (i) Oncotic Pressure and Clot Liquefaction: Some researchers propose that increasing oncotic pressure within the enclosed region due to partial clot liquefaction contributes to CSDH progression.While this concept remains controversial, adjusting the patient's head end of the bed may help modulate the pressure gradient [15].(ii) Recurrent Bleeding and Aberrant Veins: Another hypothesis attributes CSDH spread to repeated bleeding.Dilated, aberrant veins within the hematoma's outer layer are implicated in this process [16].Exudation from macro capillaries in the CSDH outer membrane likely plays a crucial role in disease progression.Elevating the head end of the bed during treatment may mitigate this source of hemorrhage [17].
During surgery, particularly in awake patients, the sitting position offers relaxation and convenience for both the patient and the surgeon.The burr hole, created near the patient's vertex (and the vertex of the CSDH), acts as a natural barrier, preventing gas entry into the subdural cavity.Although the sitting position has historically been associated with complications (such as venous air embolism), recent studies show reduced complication rates in patients undergoing surgeries in this position [18,19].
Furthermore, some authors advocate early post-procedure head elevation and prompt mobilization to prevent complications related to prolonged recumbency, including atelectasis, pneumonia, and venous thromboembolic diseases [20,21].However, anesthesiologists and surgeons approach this position cautiously [22].
While our previous work showed that various factors have been associated with the recurrence of CSDH and other outcomes [23][24][25][26], optimal patient positioning remains uncertain.This study aims to provide updated evidence and compare different bedside positions regarding their impact on recurrences and complications.By examining these factors, we hope to enhance our understanding of effective management strategies for CSDH.

Literature search
We conducted a thorough literature review across various databases, including PubMed, Cochrane CENTRAL, Scopus, Web of Science, and Ovid, with the latest search performed in August 2023.Our search strategy utilized Medical Subject Headings terms, including ("subdural hematoma" or "chronic subdural hematoma") in combination with ("supine" or "elevated" or "bed header").To ensure inclusivity, we performed the search without any filters.Additionally, we adhered to a meticulous approach by manually scrutinizing the reference lists of studies meeting our initial criteria, ensuring that no potentially relevant studies were inadvertently omitted during our search process.

Eligibility criteria
We followed a defined set of criteria based on the PICO framework: (1) Patients with CSDH; (2) Elevated head position; (3) Supin head position; (4) Assessment of morbidity, mortality, and recurrence rates.Our selection criteria excluded studies that did not meet the PICO criteria, as well as case reports, review papers, and secondary reviews.Additionally, conference abstracts were excluded due to their tendency to present incomplete or insufficiently detailed results.

Study selection and data extraction
Two reviewers (IS and AW) initially screened studies based on titles and abstracts using Rayyan [27].Subsequently, the complete texts of potentially eligible studies underwent comprehensive evaluation for final inclusion.Disagreements between reviewers prompted constructive discussions to reach consensus, with a third reviewer (AA) making the final decision if consensus was unattainable.For included studies, two authors (IS and AS) independently extracted data using standardized templates on Google Sheets for outcomes and study population characteristics, including study ID, country, study design, sample size, follow-up period in months, gender distribution, mean age at baseline, inclusion criteria and exclusion criteria for each study.

Quality assessment
Two reviewers independently evaluated the quality of the included studies (IS and AW), and a third author resolved any disagreements (MAzid).For observational studies, we employed a modified New Castle Ottawa scale consisting of eight questions distributed across the domains of selection (four questions), comparability (one question), and outcome (three questions).Each question carried a maximum score of 1 point, except for comparability, which could be assigned 2 points [28].Ratings were categorized as "high quality" (7-9 points), "some concern" (5-6 points), and "low quality" (0-4 points).
Randomized Controlled Trials (RCTs) underwent assessment using the Cochrane risk of bias tool 2, with each RCT categorized as high quality, some concern, or low quality [29].

Data synthesis and statistical analysis
If sufficient studies addressing a specific outcome were available, we conducted a meta-analysis using R and StataMP version 17.The Mantel-Haenszel method used the fixed-effect model to calculate the summary estimate.Dichotomous data were computed using risk ratios (RR) and 95% confidence interval (CI), and continuous data were calculated using mean and standard deviation.The chi-square statistic was used to calculate I-squared.A Chi-square with a p-value less than 0.1 was considered significant heterogeneity.Also, the I-square value of more than or equal to 50% indicated high heterogeneity [30].Also, we performed meta-regression with each outcome, using the average age of the patients in each study, and the results were reported as standard error (SE) and 95% CI.We conducted a sensitivity analysis to evaluate the impact of these studies on the overall assessment of results.

Study selection
Our investigation yielded a comprehensive collection of 855 articles, sourced as follows: 105 from Pubmed, 20 from WOS, 671 from Embase, 24 from Cochrane, and 35 from Scopus.After eliminating 223 duplicates, we conducted title and abstract screenings on eight articles, excluding an additional three.Subsequent full-text screening retained five articles for quantitative analysis [3,4,14,31,32] (refer to PRISMA Fig. 1).

Quality, summary, and baseline characteristics of included studies
The quality assessment of the included studies, as determined by the Cochrane risk of bias assessment, indicated a moderate to high quality.Figure 2 provides a comprehensive overview of the quality assessment domains for three studies, showing that all three RCTs had some concerns in the randomization process; some concerns were also found in some studies regarding selection and deviations from the intended intervention.Non-RCT trials showed that the study of Adeolu et al. [26] was of high quality, and some concerns in selection were found in Miele et al. [4].
For the summary of the studies, there were 146 patients in the study group and 138 patients in the control group, of which we included 284 patients.Table 1 briefly summarizes baseline characteristics and main findings of the included studies.

Sensitivity analysis.
The sensitivity analysis consistently maintained the same results for all outcomes.The I 2 statistic ranged from 0 to 29%, indicating low heterogeneity in the data, thus suggesting a high level of homogeneity (Fig. 4a-c).

Discussion
The systematic review and meta-analysis on the impact of postoperative bed header position (elevated vs. supine) in managing CSDH revealed no statistically significant differences in clinical outcomes between the two positioning strategies.The study pooled data from five studies, encompassing 284 patients, and discussed three primary clinical outcomes: recurrence rate, the second intervention due to recurrence, and postoperative complications.The findings, expressed as risk ratios and confidence intervals, indicated that the elevation of the bed header post-operatively did not significantly influence the recurrence, the need for second interventions, or the incidence of postoperative complications compared to the supine position.These findings suggest that the position of the bed header, whether elevated or supine, post-CSDH surgery does not have a differential impact on the recurrence rates, requirement for additional surgical interventions, or the development of complications.This outcome underscores the need for further research, particularly randomized controlled trials with long-term follow-ups, to explore other factors influencing postoperative outcomes in CSDH management.
In comparing our findings with those of a previous metaanalysis conducted in 2014 [33], both studies corroborate the conclusion that there is no statistically significant difference in recurrence rates, necessity for reoperation, or postoperative complications between elevated and supine bed header positions following surgery for CSDH.The earlier metaanalysis reported a slightly suggestive but non-significant trend towards reduced recurrences with an elevated bed header, with relative risks closely aligning with those found in our study (Recurrence: 0.51 vs. our RR = 0.77; Reoperation: 1.07 vs. our RR = 1.07; Complications: 1.15 vs. our RR = 1.16).Both analyses underscore the critical need for Fig. 2 Risk of bias assessment is represented in traffic light plot and summary plot according to the Cochrane risk-of-bias tool, created using robvis [35] and The Newcastle-Ottawa Scale assessment for nonrandomized studies    further randomized controlled trials to increase the quality of evidence of the impact of postoperative positioning on CSDH management outcomes.The significance of the postoperative bed header position in managing CSDH has been debated considerably, with varying practices and outcomes reported in the literature.Our findings align with those of Adeolu et al. [31] and Ishfaq et al. [14], indicating that the elevation of the bed header post-operatively does not significantly affect the rate of hematoma recurrence or the incidence of postoperative complications [14,31].This suggests that early mobilization, regardless of bed header position, may be a viable option for patients, potentially facilitating quicker recovery without increasing risks.Contrarily, Abouzari et al. [3] reported an increased recurrence rate associated with an upright posture soon after surgery, highlighting the potential risk factors that must be considered when deciding postoperative care [3].Despite these differing outcomes, our manuscript, along with the study by Ishfaq et al. [14], suggests that the positioning of the patient's head, either flat or elevated, does not grant access to the operculum or significantly influence the surgical efficacy in terms of hematoma evacuation.Furthermore, the study by Adeolu et al. [31] underscores the absence of significant differences in outcomes between early and late mobilization, advocating for the benefits of early patient mobilization to reduce hospital stays without exacerbating side effects or recurrence rates.

Limitations
First, including non-RCTs alongside RCTs while expanding the scope of the analysis introduces a potential bias that could skew the results.Non-RCTs are more susceptible to confounding factors and selection bias, which might affect the validity of the comparisons made between different pharmacological interventions.Second, although the sample size provided robust results based on the sensitivity analysis, it was not sufficiently large enough to conduct subgroup analyses with higher statistical power.Third, our study did not account for all potential variables, such as variations in surgical technique, the exact volume of hematoma drainage, or patients' comorbid conditions, which could affect outcomes independently of bed header position.Finally, the follow-up period may not have been long enough to capture late recurrences or long-term complications.

Conclusion
No substantial disparity exists between the elevated and supine bed header positions concerning recurrence rates, second interventions for recurrence, or postoperative complications.However, we recommend conducting future randomized controlled trials with larger patients and longterm follow-ups to further elucidate optimal management strategies for CSDH patients.

Fig. 1
Fig.1PRISMA chart of the reported studies showing the search selection strategy and exclusion criteria[34]

Fig. 3
Fig. 3 Forest plot of (a) recurrence rate, (b) second intervention for recurrence, and (c) postoperative complications

Table 1
Baseline characteristics and main findings of the included studies