Prophylaxis for cerebral desaturation events (CDEs) during anesthesia in the beach chair position (BCP) for shoulder surgeries has not been evaluated. We systematically analyzed the effectiveness of various prophylactic measures used in this clinical setting.
We performed a meta-analysis (PROSPERO; no. CRD42020167285) of trials reporting CDEs and regional cerebral oxygen saturation (rSO2) and jugular venous oxygen saturation (SjvO2) values in anesthetized patients undergoing shoulder surgery in BCP. Considering the type of prophylactic measures used (pharmacological or non-pharmacological), a subgroup analysis was planned. Outcomes included (1) rSO2 and SjvO2 data with and without prophylactic measures for CDEs, recorded for different time intervals, and (2) the number of patients experiencing CDEs and hypotension.
Twelve studies (786 patients) were included in the analysis. We observed lower absolute rSO2 values for early and all-time periods for vasoactive agent prophylaxis. The lowest achieved rSO2 values were also lower for vasoactive agent prophylaxis. Risk of CDEs was higher with vasoactive agent prophylaxis. Subgroup analysis identified targeted mild hypercarbia as effective in preserving cerebral oxygenation. Similarly, targeted mild hypercarbia prevented the fall in rSO2 with position change. Meta-regressions revealed statistically significant highest estimates for vasoactive agent prophylaxis in contrast to targeted mild hypercarbia. Likelihood of not developing CDEs was higher for targeted mild hypercarbia. In contrast to rSO2, most prophylactic methods reduced hypotensive episodes.
Targeted mild hypercarbia can reduce BCP-related CDEs. Evidence does not favor prophylactic use of vasoactive agents for the prevention of cerebral desaturations irrespective of whether their use interferes with cerebral oximetry readings.
Beach chair position (BCP) surgeries are associated with significant cerebral desaturation events (CDEs) in as many as 80% of patients [
Our study attempted to determine whether any particular pharmacological or non-pharmacological technique is useful for reducing CDEs during BCP surgeries. Confirming an association between the two would improve predictability, provide insight into the possible underlying pathophysiological mechanisms, and guide the anesthesiologist on the most efficacious method of preventing these undesirable events. Therefore, we performed a systematic review and meta-analysis to summarize the existing evidence on the ability of prophylactic measures to prevent CDEs in this clinical setting.
This meta-analysis was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses [
We included prospective randomized clinical studies or randomized controlled trials (RCTs) with adult patients (> 18 years) who underwent elective shoulder surgeries in BCP. Reporting of monitored cerebral oxygen saturation-related data and at least one prophylactic method used to prevent CDEs were mandatory for inclusion. Publications in all languages were considered. The patients received one of the following anesthetic modalities: (1) planned general anesthesia (GA) or (2) regional anesthesia (RA),
An electronic literature search, specifically restricted to randomized studies or RCTs of BCP, was conducted in MEDLINE, CINAHL (EBSCO host), Google Scholar, and the Cochrane Central Register of Controlled Trials. The bibliography of the retrieved manuscripts was searched for additional studies pertaining to data encompassing our primary outcome of interest. These included studies reporting incidence of CDEs, maximum and minimum average cerebral oxygen saturations, serial average cerebral saturation values overtime periods, critical CDEs, and the percentage change of cerebral saturations, with a caveat that both supine, pre-BCP and BCP data are available. Similar to cerebral saturation, SjvO2 was documented whenever data were available. Twenty-first-century literature, that is, literature published only after January 1, 2000, was scanned because anesthesia protocols have remained uniform during this period. Cohorts with matched controls, retrospective studies, reviews with inadequate information on primary outcomes of interest, abstracts, and letters to the editor were not included. The detailed search strategy is shown in
A collection of studies was conducted by TPT and HK. The manuscripts meeting the inclusion criteria were assessed, and data were extracted following a standardized format by the same authors. The extracted items comprised study characteristics, risk of bias domains [
Data relevant to the outcomes of interest were extracted from each study in this meta-analysis. The rSO2 or SjvO2 data included continuous data documented as pooled averages or sequential data at various intervals for a study. Data were collected as a single or combined value in the form of mean and standard deviation (SD) or median and interquartile range (IQR), respectively. If multiple datasets were available, they were converted into pooled statistical averages. The other dichotomous data included the number of patients experiencing CDEs.
The data were tabulated before induction (baseline) and post-induction (relating to pre-BCP and BCP categories after stabilization of vital signs). The BCP rSO2 or SjvO2 data were pooled for the time periods mentioned in the respective publications. If the recorded data timings were non-specific, they were approximated to a specific time by a mutual discussion with the authors. Publications with unreported or inconclusive data that could not be obtained after attempts to contact the authors were excluded from this review.
To analyze cerebral saturation data, four categories of rSO2 or SjvO2 values were considered from the study (i.e., prophylactic measures used) and control (i.e., no prophylactic measures used) groups. The absolute values, which are mentioned as percentages, for both groups with respect to time (i.e., early or entire period of BCP) or for the type of outcome studied (i.e., rSO2/SjvO2) were recorded. These data were synthesized as pooled data that included (1) the early BCP period (rSO2/SjvO2 values, for immediate, the first 15 min of BCP), (2) the entire BCP period (all-time overall rSO2/SjvO2 values, until the reported time period or the end of surgery) referring to the pooled average values of those at all time points during BCP, (3) the lowest observed at BCP rSO2/SjvO2 values. When the right and left cerebral hemispheres were monitored separately (with either single or two different methods), the lowest value was included (4) the baseline values, which refer to the supine, pre-BCP rSO2 values after induction of anesthesia.
The data presented in tables, text, and images were used as the primary sources for extraction. Graph digitizing software (Engauge Digitizer version 10.10, @Mark Mitchell) was used to efficiently extract and estimate raw numerical data whenever textual numerical data were unavailable. When range and IQR were available, SD was estimated using the formulas SD = range / 4 and SD = IQR / 1.35, as described by the Cochrane Handbook for Systematic Reviews of Interventions [
Individual definitions for CDEs and hypotension were accepted as described by each study. Dichotomous data such as the occurrence of CDEs and hypotension were converted into incidence (
With regard to MAP, data evaluation and synthesis were similar to those applied for CDEs or rSO2/SjvO2 values. The incidence of hypotension was counted whenever the events were reported at least once either individually or sequentially for each patient.
To explore the potential causes of heterogeneity that could influence the primary outcomes, we pre-identified certain aspects of individual study groups. These included (1) anesthetic technique (GA vs. combined GA and RA); (2) induction agent (propofol vs. thiopentone); (3) maintenance anesthetic agent (propofol vs. inhalational agents); (4) prophylactic measures (vasoactive agents vs. preloading vs. SCD vs. targeted mild hypercarbia techniques vs. compression stockings vs. others), and (5) maintenance vasopressors (phenylephrine vs. ephedrine vs. others).
Meta-analysis was conducted using Review Manager (RevMan 5.4.1, Cochrane Collaboration, Denmark, 2014). A random-effects model was used for all analyses. Heterogeneity was measured and expressed as
Because of overlapping of use (i.e., more than one) of different prophylactic measures, a meta-regression analysis was planned to estimate the effectiveness of the individual prophylactic measures. Pre-BCP (supine, after anesthesia induction) and BCP (all-time overall, absolute [%], and pooled) cerebral saturation values were considered for meta-regression. Meta-regression data inputs were different from the data of conventional meta-analysis, where the former included the MDs from baseline to all-time overall fall of rSO2 values. Meta-regression was performed using JASP software (Version 0.9.2, BibTeX, University of Amsterdam, the Netherlands). The effect size (estimate) and standard error (SE) were used for meta-regression.
The certainty of the evidence was summarized using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) [
From 2,297 studies that were initially screened, 56 potentially relevant manuscripts were selected based on abstracts (
Cerebral oxygenation monitoring was performed using INVOS™ 5100 B/C (Medtronic, Ireland) cerebral oximetry monitoring devices [
CDE was uniformly defined as > 20% decrease from baseline values and critical desaturation as < 55% (absolute value,
Pooled absolute rSO2 (comparisons with controls,
Pooled absolute rSO2 (comparisons with controls,
The lowest achieved rSO2 (comparisons with controls,
The SjvO2 values (comparisons with controls,
Meta-regression analysis included 11 studies [
Ten studies reporting patients with CDEs [
Ten studies [
Phenylephrine was used in five studies [
A few studies compared cerebral desaturations with respect to time-person observations, such as time from induction or time from upright positioning to the onset of CDE, and average cumulative CDE durations. However, the data were inadequate for additional analyses. Serious adverse neurological outcomes (as reported by all studies) and postoperative cognitive dysfunction (as reported by three studies [
Meta-regression analysis of the number of patients experiencing CDEs (
Two studies [
The risk of bias summary and graph are presented in
The relevant summary results are presented in
In our meta-analysis, we evaluated the efficacy of different prophylactic measures employed to prevent cerebral desaturation during shoulder surgeries performed in BCP. We observed that not all prophylactic measures were successful, and the methods did differ in efficacy. Our current study provides concrete evidence that PPMs cannot effectively prevent cerebral desaturation. The benefits of a few NPPM techniques, such as targeted mild hypercarbia, for maintaining cerebral oxygenation during BCP are also evident. However, a few trials have confirmed the protective effects of HES preloading, and studies of SCDs or RIPC are scarce. Our meta-analysis unequivocally confirmed the negative effect of vasoactive agents on rSO2 values (but not on SjvO2), highlighting their failure in protecting patients from CDEs despite their ability to prevent hypotension.
A pervasive issue in the pharmacologic prophylaxis portion of this meta-analysis is the extracranial contribution (contamination) [
In this review, the effectiveness of individual prophylactic measures (especially NPPMs) was analyzed through a separate analysis. Drawing conclusions on NPPMs was not possible, as we have lumped together with a disparate and diverse group. Importantly, since no study authors used a single measure to prevent cerebral desaturation, analyzing a single method (such as NPPMs) could be misleading. Therefore, the more appropriate method of meta-regression analysis was performed. Our analysis confirmed the beneficial effects of a few NPPMs, such as targeted mild hypercarbia, HES, and RIPC. Targeted mild hypercarbia during these procedures must be performed with caution and must not be performed to the exclusion of blood pressure support. Hypercarbia impairs cerebral autoregulation and puts the patient at a higher risk for cerebral hypoperfusion, should hypotension occur at the same time. Additional subgroup analysis established stronger evidence for targeted mild hypercarbia use. Few prospective studies [
One of the interpretations of this meta-analysis is that NPPMs in combination can be effectively deployed during BCP surgery to enhance rSO2; this conclusion could be relevant to clinicians in maintaining cerebral oxygenation. For example, targeted mild hypercarbia of 40-42 mmHg during controlled ventilation, appropriate preloading (HES), and concomitant use of SCDs can significantly reduce CDEs. The routine use of RIPC as a prophylactic measure has not yet been recommended. While a previous prospective cohort study [
While PPMs were inferior to a few NPPMs in the prevention of CDEs (coefficient evaluation), both exhibited similar effects with respect to lowering the incidence of hypotension (vs. controls). Thus, PPMs were unable to achieve the ultimate therapeutic benefit, despite maintaining MAP. The association of episodic decrease in MAP with the incidence of cerebral desaturation and its direct correlation with cerebral oximetry values remain unconfirmed [
Over 80% of the patients in this meta-analysis were treated with ephedrine for BCP-related hypotension. Phenylephrine and ephedrine are commonly used for this indication. While treating hypotension in a non-BCP setting, the former was shown to decrease cerebral oxygen saturation even with correction of arterial blood pressure [
Our study had some limitations. Higher heterogeneity values represent different NPPM methods applied over cohorts. The type of anesthesia, maintenance anesthetics, Fraction of inspired oxygen concentration, and other co-variables could have partially influenced the outcomes. The definition of ‘event’ could vary according to the authors’ perception, and this could have a bearing on the incidence reporting. The range of rSO2 values may be significantly larger when measured with INVOS™ devices compared to FORE-SIGHT™, but the exact underlying reasons for these differences remain unknown [
In conclusion, the evidence favors the prophylactic use of targeted mild hypercarbia techniques to effectively reduce BCP-CDEs and best preserve cerebral oxygenation. Evidence does not favor the use of prophylactic vasoactive agents for the prevention of cerebral desaturations, irrespective of whether their use interferes with cerebral oximetry readings. One may use a combination of a few NPPMs as prophylactic measures; however, an RCT investigating the effect of combined use of all NPPMs could conclusively demonstrate the benefits. At the same time, comparisons of prophylactic as well as therapeutic effects of different vasoactive agents (such as phenylephrine vs. ephedrine) for BCP-CDEs could set the direction for future research in this field.
We sincerely acknowledge Dr. Rajani Kadri, M.S., Associate Professor, Department of Ophthalmology, A J Institute of Medical Sciences & Research Centre, Kuntikana, Mangalore, India. Mangalore, for her contribution during the preparation of the manuscript. We also thank Pranavi and Poorvi for their kind help during the manuscript preparation.
No potential conflict of interest relevant to this article was reported.
Thrivikrama Padur Tantry (Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Resources; Software; Validation; Writing – original draft; Writing – review & editing)
Baikunje Golitadka Muralishankar (Formal analysis; Investigation; Methodology; Project administration; Resources; Validation)
Harish Karanth (Data curation; Methodology; Project administration; Resources; Validation)
Pramal Karkala Shetty (Data curation; Formal analysis; Resources; Software)
Sunil Purushotham Shenoy (Data curation; Methodology; Project administration; Writing – review & editing; Validation)
Dinesh Kadam (Project administration; Validation; Writing – review & editing)
Gururaj Tanthry (Data curation; Formal analysis; Resources)
Rithesh Shetty (Data curation; Formal analysis; Resources)
The search strategy. The search terms were used to search MEDLINE, CCRCT (Cochrane Central Register of Controlled Trials), CINHAL (Cumulative Index to Nursing and Allied Health Literature, EBSCO host), and Google Scholar (modified to suit each specific database with abstract, keywords, and text with the removal of duplicates).
The flow chart for literature identification and study selection. BCP: beach chair position, CDE: cerebral desaturation event, CCRCT: Cochrane Central Register of Controlled Trials, CINHAL: Cumulative Index to Nursing and Allied Health Literature, n: number of studies, rSO2: regional cerebral oxygen saturation.
The study characteristics. ASA PS: American Society of Anesthesiologists physical status, AVP: arginine vasopressin, BCP: beach chair position, BL: baseline, BP: blood pressure, CBF: cerebral blood flow, CDE: cerebral desaturation event, CS: compression stockings, DM: diabetes mellitus, Eph: ephedrine, GA: general anesthesia, HES: hydroxyethyl starch, HR: heart rate, HTN: hypertension, ICB: infraclavicular block, ISB: interscalene block, MAP: mean arterial pressure, MBP: mean blood pressure, N2O: nitrous oxide, NA: not applicable, NE: norepinephrine, NP: not provided, O2: oxygen, Phe: phenylephrine, rSO2: regional saturation of oxygen in the brain, SCD: sequential compression device, TIVA: total intravenous anesthesia.
Publication bias. The funnel plots for (A) pre-BCP (supine, after anesthesia induction) and BCP (all-time overall, absolute, and pooled) cerebral saturation values, (B) the number of patients experiencing the CDEs during meta-regressions of prophylactic factors to prevent cerebral desaturation. The regression test for funnel plot asymmetry (Egger's test) P values were > 0.05; however, poor model fit – fit measures were recorded for funnel plot B.
Studies depicting associations between MAP and rSO2. Correlation analysis was used in most of the studies to establish the associations. BCP: beach chair position, BL: baseline, CDE: cerebral desaturation event, CO: cardiac output, DBP: diastolic blood pressure, ETCO2: end-tidal carbon dioxide, eTMAP: estimated temporal mean arterial pressure, L: left-sided measurement, MAP: mean arterial pressure, MBP: mean blood pressure, NIBP: noninvasive blood pressure, NIRS: near-infrared reflectance spectrometry, R: right-sided measurement, r: correlation coefficient, rSO2: regional cerebral oxygen saturation, SBP: systolic blood pressure, *INVOSTM (Somanetics, Troy, MI, USA) and **FORE-SIGHTTM (Cas Medical Systems Inc., Branfort, CT, USA), the names of cerebral oximeter equipments that measured the regional cerebral oxygen saturation.
Forest plots depicting (A) absolute values of rSO2 for early period (first 15 min of BCP) for vasoactive agents and targeted mild hypercarbia techniques, (B) absolute values of rSO2 for early period (first 15 min of BCP) based on whether prophylactic measures are pharmacological or non-pharmacological, and (C) absolute values of SjvO2 for an early time period for PPMs. The mean differences between individual trials and 95% CIs are shown for prophylactic measures. Absolute values are expressed in %. The overall effects for each prophylactic measure and the differences between the subgroups are shown. The 95% CIs are shown as lines for individual studies and as diamonds for pooled estimates. IV: inverse variance, NPPM: non-pharmacological prophylactic methods, PPM: pharmacological prophylactic methods, rSO2: regional cerebral oxygen saturation, SjvO2: jugular venous oxygen saturation.
Forest plots depicting (A) absolute values of rSO2 for an all-time period for vasoactive agents and targeted mild hypercarbia techniques, (B) absolute values of rSO2 for an all-time period based on whether prophylactic measures are pharmacological or non-pharmacological, and (C) absolute values of SjvO2 for all-time period for PPMs. The mean differences between individual trials and 95% CIs are shown for prophylactic measures. Absolute values are expressed in %. The overall effects for each prophylactic measure and the differences between the subgroups are shown. The 95% CIs are shown as lines for individual studies and as diamonds for pooled estimates. IV: inverse variance, NPPM: non-pharmacological prophylactic methods, PPM: pharmacological prophylactic methods, rSO2: regional cerebral oxygen saturation, SjvO2: jugular venous oxygen saturation.
Forest plots depicting (A) absolute values for lowest achieved rSO2 for vasoactive agent, compression stockings, and targeted mild hypercarbia techniques, (B) subgroup analysis for lowest achieved rSO2, based on whether prophylactic measures are pharmacological or non-pharmacological, and (C) SjvO2 changes for lowest achieved values for PPMs. The mean differences between individual trials and 95% CIs are shown for prophylactic measures. Absolute values are expressed in %. The overall effects for each prophylactic measure and the differences between the subgroups are shown. The 95% CIs are shown as lines for individual studies and as diamonds for pooled estimates. IV: inverse variance, NPPM: non-pharmacological prophylactic methods, PPM: pharmacological prophylactic methods, rSO2: regional cerebral oxygen saturation, SjvO2: jugular venous oxygen saturation.
Forest plots depicting numbers of patients who developed (A) CDEs and (B) hypotension. The individual trials’ RRs or ORs, SEs, and the pooled estimates are shown. The 95% CIs are shown as lines for individual studies and as diamonds for pooled estimates. Natural log transformation was adopted, as the outcomes for incidences were expected to be non-normally distributed for CDE incidences. CDE: cerebral desaturation event, M-H: Mantel-Haenszel, NPPMs: non-pharmacological prophylactic methods, OR: odds ratio, PPMs: pharmacological prophylactic methods, RR: risk ratio, rSO2: regional cerebral oxygen saturation, SE: standard error, SjvO2: jugular venous oxygen saturation.
Risk of bias summary (A) and graph (B).
Meta-regression Analysis
Prophylactic measure | Estimate (SE, 95% CI) | P value | Model fit |
---|---|---|---|
A. All-time overall rSO2 | |||
Intercept | 7.8 (0.892, 6.1 to 9.6) | < 0.001 | Omnibus P < 0.001 |
Compression stocking (Y) | 0.2 (1.491, -2.8 to 3.1) | 0.921 | Heterogeneity P = 0.646 |
Sequential compression device (Y) | -1.6 (1.184, -3.95 to 0.7) | 0.167 | Egger's P = 0.514 |
Low BCP angle (Y) | 1.2 (1.525, -1.8 to 4.2) | 0.438 | Log-likelihood, -37.9 |
Regional ischemic preconditioning (Y) | -2.5 (1.018, -4.5 to -0.5) | 0.014 | Deviance, 75.8 |
Crystalloid loading (Y) | -0.9 (0.99, -2.8 to 1.1) | 0.387 | AIC, 104.1 |
Hydroxyethyl starch (Y) | -3.5 (1.043, -5.5 to -1.5) | < 0.001 | |
Targeted mild hypercarbia (Y) | -5.5 (1.408, -8.2 to -2.7) | < 0.001 | |
Vasoactive agents (Y) | 7.8 (1.534, 4.8 to 10.8) | < 0.001 | |
B. Number of patients developing CDEs | |||
Intercept | 20.3 (6.487, 7.6 to 32.99) | 0.002 | Omnibus P = 0.459 |
Compression stocking (Y) | 0.5 (6.335, -11.9 to 12.9) | 0.937 | Heterogeneity P < 0.01 |
Sequential compression device (Y) | -10.2 (8.375, -26.6 to 6.3) | 0.225 | Egger's P = 0.299 |
Low BCP angle (Y) | 3.025 (8.235, -13.1 to 19.2) | 0.713 | Log-likelihood, -50.2 |
Regional ischemic preconditioning (Y) | -2.527 (12.641, -27.3 to 22.3) | 0.842 | Deviance, 100.3 |
Crystalloid loading (Y) | -10.752 (6.848, -24.2 to 2.7) | 0.116 | AIC, 120.3 |
Hydroxyethyl starch (Y) | -8.924 (8.193, -24.98 to 7.1) | 0.276 | |
Targeted mild hypercarbia (Y) | -12.31 (10.14, -32.2 to 7.6) | 0.225 | |
Vasoactive agents (Y) | 5.734 (7.632, -9.2 to 20.7) | 0.452 |
Meta-regression analysis of prophylactic measures used across the study groups. (A) Pre-BCP (supine, after anesthesia induction) and BCP (all-time overall, absolute, and pooled) cerebral saturation values were considered for meta-regression depending on the use of prophylactic measures (yes vs. no). (B) Meta-regressions of ‘number of patients experiencing CDEs’, where baseline supine, pre-BCP CDEs were assumed as ‘zero’ for the analysis. All meta-regressions were performed using the restricted maximum likelihood method and random effects. AIC: Akaike information criterion, BCP: beach chair position, CDE: cerebral desaturation event, rSO2: regional cerebral oxygen saturation, SE: standard error, Y: yes.
Summary of Results with GRADE of Evidence
No. | Outcomes | Studies | Number of participants | Relative effect; MDs (%) or RR/OR (95% CI) | Certainty of the evidence (GRADE) |
---|---|---|---|---|---|
1 | Absolute values for rSO2 for early period - PPMs | 3 | 150 | -13.58 (-16.03, -11.4) | ⨁⨁⨁◯, moderate |
2 | Absolute values for SjvO2 for early period - PPMs | 3 | 150 | -0.88 (-5.47, 3.7) | ⨁⨁⨁◯, moderate |
3 | Absolute values for rSO2 for all-time period - PPMs | 4 | 184 | -12.23 (-14.6, -9.87) | ⨁⨁⨁◯, moderate |
4 | Absolute values for SjvO2 for all-time period - PPMs | 3 | 150 | -0.23 (-4.67, 4.21) | ⨁⨁⨁◯, moderate |
5 | Absolute values for lowest rSO2 achieved - PPMs | 3 | 150 | -12.72 (-15.28, -10.15) | ⨁⨁⨁◯, moderate |
6 | Absolute values for lowest SjvO2 achieved - PPMs | 3 | 150 | 1.45 (-2.85, 5.76) | ⨁⨁⨁◯, moderate |
7 | Number of patients developing CDEs - PPMs (event) | 3 | 124 | RR 4.01 (1.82, 8.81) | ⨁⨁◯◯, low |
8 | Number of patients developing hypotension episodes - PPMs | 4 | 184 | OR 0.13 (0.06, 0.28) | ⨁⨁◯◯, low |
9 | Number of patients developing hypotension episodes - NPPMs | 6 | 316 | OR 0.27 (0.10, 0.74) | ⨁⨁◯◯, low |
10 | Effect of targeted mild hypercarbia techniques (all-time overall for absolute rSO2 values) | 2 | 110 | 4.93 (2.45, 7.41) | ⨁⨁⨁◯, moderate |
11 | Effect of targeted mild hypercarbia techniques (lowest achieved absolute rSO2 values) | 2 | 110 | 6.0 (3.35, 8.65) | ⨁⨁⨁◯, moderate |
12 | Effect of targeted mild hypercarbia techniques (Pre-BCP to BCP fall in absolute rSO2 values) | 2 | 108 | 1.56 (-0.71, 3.83) | ⨁⨁⨁◯, moderate |
13 | Effect of targeted mild hypercarbia techniques (number of patients developing fall in rSO2, event) | 2 | 110 | RR 0.15 (0.05, 0.42) | ⨁⨁⨁◯, moderate |
14 | Effect of compression stockings (lowest achieved absolute rSO2 values) | 2 | 56 | -0.38 (-5.85, 5.09) | ⨁⨁◯◯, low |
15 | Effect of compression stockings (number of patients developing CDEs, event) | 2 | 104 | RR 1.20 (0.75, 1.93) | ⨁⨁◯◯, low |
CDE: cerebral desaturation event, GRADE: Grading of Recommendations Assessment, Development and Evaluation, MD: mean difference, NPPMs: non-pharmacological prophylactic methods, OR: odds ratio, PPMs: pharmacological prophylactic methods, RR: risk ratio, rSO2: regional oxygen saturation, SjvO2: jugular venous oxygen saturation.