Out-Of-Hospital Cardiac Arrest Patients Have Better Outcomes with Endotracheal Intubation Compared to Supraglottic Airway Placement: a Meta-Analysis

Home , Airtraq, Emergency physician

Out-of-Hospital Cardiac Arrest Patients Have Better Outcomes with Endotracheal Intubation Compared to Supraglottic Airway Placement: A Meta-Analysis

A thesis submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of

Master of Science in Clinical & Translational Research

In the Department of Environmental Health Division of Epidemiology & Biostatistics of the College of Medicine March 2015 By

Justin L. Benoit

MD, Case Western Reserve University, May 2010 BS, University of Maryland, College Park, May 2002

Committee Chair: Erin N. Haynes, DrPH

Abstract

Objective: Overall survival from out-of-hospital cardiac arrest (OHCA) is less than 10%. After initial bag-valve mask ventilation, 80% of patients receive an advanced airway, either by endotracheal intubation (ETI) or placement of a supraglottic airway (SGA). The objective of this study was to compare patient outcomes for these two advanced airway methods in OHCA patients treated by Emergency Medical Services (EMS).

Methods: A dual-reviewer search was conducted in PubMed, Scopus, and the Cochrane Database to identify all relevant peer-reviewed articles. Exclusion criteria were traumatic arrests, pediatric patients, physician/nurse intubators, rapid sequence intubation, video devices, and older airway devices. Outcomes were (1) return of spontaneous circulation, (2) survival to hospital admission, (3) survival to hospital discharge, and (4) neurologically intact survival to hospital discharge. Results were adjusted for covariates when available, and combined using meta-analysis techniques and the random effects model.

Results: From 3,454 titles, 10 observational studies fulfilled all criteria, with 34,533 ETI patients and 41,116 SGA patients. Important covariates were similar between groups. Patients who received ETI had statistically significant higher odds of return of spontaneous circulation (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.05-1.55), survival to hospital admission (OR 1.34, CI 1.02-1.75), and neurologically intact survival (OR 1.33, CI 1.09-1.61) compared to SGA. Survival to hospital discharge was not statistically different (OR 1.15, CI 0.97-1.37).

Conclusions: Patients with OHCA who receive ETI by EMS are more likely to obtain return of spontaneous circulation, survive to hospital admission, and survive neurologically intact when compared to SGA.

iii

Acknowledgements

The author would like to acknowledge his collaborators Ryan B. Gerecht, MD, Michael T. Steuerwald, MD, and Jason T. McMullan, MD. The author would also like to acknowledge Jeffrey Welge, PhD, for his assistance on meta-analysis techniques and statistical modeling. This work was unfunded. There are no conflicts of interest to disclose.

Table of Contents

List of Tables and Figures ...... vi Introduction ...... 1 Methods ...... 2 Results ...... 4 Discussion ...... 5 Conclusions ...... 8 Tables and Figures ...... 9-16 Bibliography ...... 17-19 Appendix ...... 20-28

List of Tables and Figures

Figure 1: Search Strategy ...... 9 Table 1: Baseline Demographics ...... 10 Table 2: Raw Outcomes ...... 11 Table 3: Quality of Evidence ...... 12 Figure 2: Forest Plot for Return of Spontaneous Circulation ...... 13 Figure 3: Forest Plot for Survival to Hospital Admission ...... 14 Figure 4: Forest Plot for Survival to Hospital Discharge ...... 15 Figure 5: Forest Plot for Neurologically Intact Survival to Hospital Discharge ...... 16

Introduction

For patients suffering out-of-hospital cardiac arrest (OHCA), the overarching goal of emergency medical care is to resuscitate the patient and achieve neurologically intact survival. Interventions performed by Emergency Medical Services (EMS) prior to Emergency Department arrival have a significant impact on obtaining this goal.1 Approximately 360,000 OHCA occur annually in the United States, and survival to discharge is around 9.5% despite decades of research.2 Additionally, significant regional variation exists, with some areas only obtaining a survival to discharge rate of 1.1%.3 As such, the need for improvement in the care of OHCA patients has long been recognized.

A fundamental component of resuscitation efforts is airway management, which attempts to reverse the hypoxia and hypercarbia of cardiac arrest.4 Traditionally, this occurred using a bag- valve mask. However, advanced airway management by endotracheal intubation (ETI) was introduced in the 1970s.5 It has been assumed that ETI will improve the likelihood of survival in cardiac arrest patients by facilitating oxygenation and ventilation. However, its ability to actually improve survival is still unclear.6 ETI is a difficult skill to perform in the prehospital environment. Multiple attempts, high failure rates, unrecognized tube misplacement, and interruptions in cardiopulmonary resuscitation (CPR) are common.7-10 In addition, significant effort must be put into education to both learn and maintain intubation skills.11 In response, some EMS agencies have moved towards supraglottic airways (SGA) as an alternative to ETI, as they are technically easier to insert. However, these too have been only minimally validated and may not have equivalent efficacy in maintaining proper oxygenation and ventilation.12 Currently, 80% of patients in the United States receive advanced airway management either by ETI or SGA during resuscitation from OHCA.13

The objective of this study was to determine the comparative effectiveness of ETI versus SGA after OHCA using meta-analysis techniques. Specifically, we addressed the following question: In adult, non-traumatic OHCA patients who receive advanced airway management by paramedics in the prehospital setting, is ETI associated with worse patient outcomes when compared to SGA? We hypothesized that ETI would have decreased rates of all major cardiac arrest outcomes, including neurologically intact survival to hospital discharge.

Methods

Eligibility Criteria: The inclusion criteria for this meta-analysis were (1) cardiac arrest patients with any presenting rhythm, (2) treated by EMS in the prehospital environment, (3) compared ETI to any SGA [e.g. King Laryngeal Tube, Combitube, Laryngeal Mask Airway, I-Gel], and (4) reported at least one patient outcome as defined below. Exclusion criteria were (1) traumatic aetiology of arrest, (2) pediatric studies, (3) airway primarily managed by physician or nurse, (4) rapid sequence intubation techniques, (5) video/fiber-optic airway techniques [e.g. King Vision], and (6) predominance of older airway devices [e.g. esophageal obturator airway]. Unlike Europe, the United States predominately uses emergency medical technicians (paramedics) to perform the vast majority of airway management in the prehospital setting. As such, this meta- analysis was specifically designed to evaluate these providers using standard airway techniques. To ensure that a single OHCA event was not double counted, we verified that studies did not use overlapping cardiac arrest databases.

Outcomes: There are four major outcomes after OHCA per the Utstein Guidelines.14 (1) Return of spontaneous circulation (ROSC), (2) survival to hospital admission, (3) survival to hospital discharge, and (4) neurologically intact survival to hospital discharge as defined by the Cerebral Performance Category, modified Rankin Scale, or Glasgow Outcome Scale. There were minor differences in how outcomes were defined by different studies. For this meta-analysis, the following outcomes were considered equivalent: (1) Overall ROSC or ROSC before hospital arrival, (2) admitted to the hospital or survival for 24 hours, (3) survival until discharge or 30 days after discharge, and (4) neurologically intact survival at discharge or 30 days after discharge.

Search Strategy: A dual-reviewer search was conducted in PubMed, Scopus (which contains Embase), and the Cochrane Database with assistance from a research librarian using a standard review protocol to identify all relevant peer-reviewed articles. The following Medical Subject Headings (MeSH) terms were used: “Emergency Medical Services” plus “airway management” and then “out-of-hospital cardiac arrest” plus “airway management.” The parent term “airway management” includes the MeSH terms “intubation”, “laryngeal mask” and “positive pressure respiration.” “Emergency Medical Services” includes “prehospital emergency care” and “ambulance.” All titles from this search were reviewed for relevance based on the inclusion and exclusion criteria. The abstract of articles selected based on title search were

then reviewed and the inclusion/exclusion criteria applied again. If still appropriate, the entire manuscript was reviewed. A consensus of the authors was used to determine the final list of articles that met all criteria. The reference section of included articles were forward and backward searched for other relevant articles. Similarly, the reference section from any review article found by the search process was also reviewed for relevant articles. Experts in the field were personally contacted and asked to provide any other relevant published studies. There were no language limitations or date restrictions put on this search method. The literature search was current as of April 2014.

Data Extraction: Demographic data were extracted for each airway intervention when available, including the number of patients in each arm, age, gender, presenting cardiac rhythm, witnessed versus unwitnessed arrest status, presence of bystander CPR, and bystander automated external defibrillator (AED) use. Measured treatment effects for ETI versus SGA were extracted as odds ratios with associated 95% confidence intervals for each of the four outcomes. Outcomes adjusted for covariates using propensity scoring or regression analysis and raw outcomes were extracted when available. Double data extraction was performed to ensure reliability, and any discrepancies were addressed by the authors.

Quality of Evidence: Quality was assessed by a consensus of authors using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.15 Evidence is rated as one of four levels of quality (high, moderate, low, and very low) based on the study design, risk of bias, indirectness of evidence, imprecision of results, possibility of publication bias, magnitude of effect, and plausible influence of confounding. Based on our search methods, it was required that articles be published in a peer-reviewed journal to ensure minimum quality standards.

Statistical Methods: Treatment effects were transformed to log odds ratios with 95% confidence intervals and combined for each of the four outcomes using the random effects model. The random effects model was chosen a priori based on expected heterogeneity in the final list of applicable studies. Heterogeneity was still assessed using Cochrane’s Q test with corresponding I2. Based on the quality assessment, there was no indication for funnel plot analysis. In the full model, preference was given to results adjusted for covariates over unadjusted data when both were available. Quality of evidence was used as the basis for the a priori sensitivity analysis model only, as the Meta-analysis of Observational Studies in

Epidemiology (MOOSE) criteria do not support using quality data to exclude or weight studies.16 Sensitivity analyses were also conducted to address overlapping databases. All statistical analyses were conducted using SAS 9.2 (SAS Institute, Cary NC).

Results

The primary search strategy produced 3,454 titles for review (Figure 1). Of these, 10 observational studies satisfied all inclusion/exclusion criteria.12,13,17-24 Additional forward/backward searching of references and expert consultation only provided one additional small study, suggesting adequacy of the search methodology. The 112 studies excluded after full manuscript review are listed in the Appendix.

These 10 studies included 34,533 ETI patients and 41,116 SGA patients. Baseline demographics such as age, initial cardiac rhythm, witness status, and bystander CPR or AED use were similar between groups (Table 1). Raw outcomes for included studies are shown (Table 2). The baseline demographics and raw outcomes data varied significantly between the different studies.

Based on the full random effects models, patients who received ETI had statistically significant higher odds of return of spontaneous circulation (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.05-1.55), survival to hospital admission (OR 1.34, CI 1.02-1.75), and neurologically intact survival to hospital discharge (OR 1.33, CI 1.09-1.61) compared to SGA. Survival to hospital discharge was not statistically different but followed a similar pattern (OR 1.15, CI 0.97-1.37). Forest plots of the full models with odds ratios and 95% confidence intervals for individual studies are shown (Figures 2-5).

Significant study-level heterogeneity was present for return of spontaneous circulation (I2=82.6%, p<0.001) and survival to hospital admission (I2=85.4%, p<0.001), but not for survival to hospital discharge (I2=48.8%, p=0.068) or neurologically intact survival (I2=20.2%, p=0.28).

Given that all 10 articles were observational cohort studies, overall quality of evidence was considered “low” or “very low” for all studies based on GRADE methodology (Table 3). The main cause of bias and subsequent threat to validity was a lack of statistical adjustment for known confounders of OHCA outcomes, such as those shown in Table 1, which occurred in five

studies. In addition, two studies had very small sample sizes that yielded highly imprecise measurements of effect.

Sensitivity analysis models were constructed by excluding studies that were “very low” quality of evidence based on GRADE methodology. This reduced the number of studies available to only three or four studies per outcome. Results are shown in Figures 2-5. Neurologically intact survival was still statistically significant in favor of ETI (OR 1.33, CI 1.04-1.69).

A study by Hasegawa used a Japanese OHCA database that captured the same data reported by studies already included in our models (Kohei Hasegawa, MD, MPH, e-mail communication, July 2014).6 Adding this study would have resulted in some OHCA events being counted twice. As such, we conducted a sensitivity analysis including the Hasegawa study, while excluding all overlapping Japanese studies. Return of spontaneous circulation was unchanged (OR 1.43, CI 1.03-1.99). Survival to hospital discharge was now statistically significant (OR 1.11, CI 1.03- 1.20), while neurologically intact survival was not (OR 1.22, CI 0.62-2.40), although this was based on only three studies.

A final sensitivity analysis was conducted by excluding the study by Yanagawa, which reported 15% traumatic aetiology of cardiac arrest. No significant changes were seen for return of spontaneous circulation (OR 1.26, CI 1.03-1.56) or neurologically intact survival (OR 1.33, CI 1.08-1.64).

Discussion

Despite the concern that ETI is more difficult to perform than SGA insertion in the prehospital environment, our results demonstrate that ETI is associated with improved outcomes after OHCA. Although the effect sizes are small, they are consistent across outcomes after OHCA. This includes proximal outcomes occurring minutes after cardiac arrest (e.g. return of spontaneous circulation) and distal outcomes that are not apparent until days to weeks after the cardiac arrest event (e.g. neurologically intact survival to hospital discharge.)

The mechanisms behind these associations are poorly understood. Although not common, multiple complications can occur during and after SGA insertion including pulmonary aspiration, pneumothorax, upper airway bleeding, esophageal laceration, subcutaneous emphysema,

tongue edema, tracheal injury, and pneumomediastinum.25,26 These complications may result in worse outcomes for SGA patients. Additionally, the airway is not secure after SGA insertion, so head and neck position can lead to significant oropharyngeal air leaks.27 This could be a common occurrence during transport from the scene of cardiac arrest and may result in decreased oxygenation and ventilation of the patient. Similarly, because the airway is not secure, patients with an SGA will still undergo ETI after arrival in the Emergency Department, potentially exposing these patients to hypoxia. Finally, decreased carotid blood flow has been seen in a porcine model of SGA use in cardiac arrest, which could decrease neurologically intact survival if brain oxygenation is impaired.28 However, this has yet to be demonstrated in humans.

A meta-analysis by Fouche also evaluated airway management in OHCA, but did not assess the comparative effectiveness of ETI versus SGA, focusing instead on ETI or SGA versus bag- valve mask.29 However, patients who receive only bag-valve mask ventilation may have lower expected mortality at baseline. For example, if a patient regained consciousness quickly after defibrillation, this would preclude the opportunity for ETI or SGA insertion. This would falsely elevate the observed survival for a bag-valve mask only strategy.13 Our study assessed only patients sick enough to receive an advanced airway, reducing the potential for confounding by indication.

In an effort to ensure validity, the more conservative random effects model was chosen a priori instead of a fixed effect model. It was hypothesized that differences in EMS systems worldwide would results in significant heterogeneity of outcomes. However, our results indicate that heterogeneity is low for the more distal survival outcomes, further supporting our results. To control for confounding of this observed association, we gave preference to data from logistic regression models and propensity scoring whenever provided by the included studies. Variables controlled for include initial rhythm, bystander witnessed arrest, EMS witnessed arrest, bystander CPR, AED shock before EMS arrival, location type, and ambulance response time. Although the full model included both adjusted and unadjusted data, this was felt to be reasonable since studies that provided both showed minimal to no change in odds ratios even after controlling for known confounders.13,17 The oldest study that met all inclusion/exclusion criteria for this analysis was from 2007, indicating that these results are likely relevant to current clinical practice in the prehospital environment. Although Advanced Cardiac Life Support

guidelines deemphasized airway management in 2010, it is unlikely this would have change the comparative effectiveness for these two airway techniques.

To provide an even more robust, conservative estimate of effect, we constructed an a priori sensitivity analysis model for each outcome. This demonstrated that even when data are limited to the highest quality evidence currently available, which controls for known confounders, neurologically intact survival is still improved after ETI when compared to SGA. Although other outcomes were not statistically significant under these models, this was likely because only three to four studies could be included in these highly conservative models. Under these circumstances, the random effects model produces large confidence intervals. However, it is important to note that the point estimate of the odds ratio remained unchanged for all outcomes.

One study was excluded from the full model due to overlapping databases. Including redundant data would result in double counting multiple cardiac arrest events, which would inappropriately increase the influence these data have on the final results. We chose to exclude the study by Hasegawa because unlike other studies from Japan, it contained no adjusted data and no baseline demographics of ETI versus SGA, focusing instead on bag-valve mask versus all advanced airway techniques combined.6 In addition 16.5% of patients in this study had an external aetiology for their cardiac arrest, which included trauma, hanging, drowning, intoxication or asphyxia. Although a sensitivity analysis demonstrated slightly different results when this paper was included at the expense of other studies, the overall trend was unchanged.

The main limitation of this study is that the exact course of airway events during resuscitation is often unknown. It is possible that some patients may have received SGA after failed ETI, which could result in decreased survival if CPR was interrupted or hypoxia occurred. However, the study by Wang specifically looked at this concern, and demonstrated no significant difference in the comparative effectiveness of ETI versus SGA even after adjusting for failed airway attempts.12 In addition, some studies in this meta-analysis specifically excluded patients that received multiple airway attempts or had failed airways.17 A few studies included small numbers of trauma patients, adolescent patients, or physician intubators. However, the largest violation was a 15% traumatic aetiology of arrest in the study by Yanagawa, and excluding this study had no effect on observed outcomes.24 No randomized controlled trials exist comparing these two airway interventions, resulting in an overall low quality of evidence for this meta-analysis. More research is clearly needed in this area of cardiac arrest. We attempted to reduce reviewer-level

bias with thorough, redundant search methodologies and double data extraction, but the potential for missed data is always present when performing a meta-analysis. Finally, we cannot extrapolate our findings to advanced prehospital providers such as physicians, nor to novel airway techniques such as video laryngoscopy, as they were specifically excluded from our analysis. Similarly, we cannot differentiate between the various types of SGA, as this level of data was not available.

Conclusions

In this meta-analysis of all currently available published data, non-traumatic out-of-hospital cardiac arrest patients who receive endotracheal intubation by EMS providers in the prehospital setting have improved outcomes when compared to those who have a supraglottic airway placed. Odds of return of spontaneous circulation, survival to hospital admission, and neurologically intact survival to hospital discharge are improved with intubation. Because the overall quality of evidence is universally low and limited to observation studies, a randomized controlled trial is warranted.

Tables and Figures

Figure 1: Search Strategy

Table 1: Baseline Demographics

Study Airway n Age (SD) Male (%) VT/VF (%) Witness (%) CPR (%) AED (%) Cady 200917 ETI 4335 67 (16.8) 2639 (60.9) 1075 (25.1) 2222 (51.3) 397 (9.2) 12 (0.3) SGA 1487 64 (9.8) 900 (60.6) 393 (26.4) 654 (44) 147 (9.9) 0 (0) Hanif 201018 ETI 1027 71 (16.3) 610 (59) 300 (29) 581 (57) 457 (45) SGA 131 Kajino 201119 ETI 1679 73.8 (14.6) 1021 (60.8) 278 (16.6) 1679 (100) 686 (40.9) SGA 3698 71.9 (15.2) 2291 (62) 622 (16.9) 3698 (100) 1472 (39.8) McMullan 201413 ETI 5591 66.1 (16.4) 3383 (60.5) 1252 (22.4) 2689 (48.1) 2113 (37.8) 324 (5.8) SGA 3110 63.9 (16) 1934 (62.2) 703 (22.6) 1489 (47.9) 1101 (35.4) 286 (9.2) Nagao 201220 ETI 10 SGA 189 Noda 200721 ETI 4 SGA 24 Shin 201222 ETI 250 61.7 (17) 160 (64) 32 (12.8) 83 (33.2) 10 (4) SGA 391 61 (16.9) 270 (69.1) 62 (15.9) 136 (34.8) 16 (4.1) Tanabe 201323 ETI 16054 73.8 (15.3) 9397 (58.5) 1201 (7.5) 7126 (44.4) 6722 (41.9) 51 (0.3) SGA 34125 72.1 (15.9) 20657 (60.5) 2943 (9.8) 13413 (39.3) 12930 (37.9) 77 (0.2) Wang 201212 ETI 8487 67.6 (16.6) 5423 (63.9) 2023 (24) 4473 (52.7) 2997 (35.3) SGA 1968 64.2 (16.2) 1360 (69.1) 486 (24.7) 1021 (52) 726 (36.9) Yanagawa 201024 ETI 158 SGA 478

ETI = Endotracheal intubation; SGA = Supraglottic Airway; SD = Standard deviation; VT = Ventricular fibrillation; VF = Ventricular tachycardia; Witness = Cardiac arrest witnessed by bystander or Emergency Medical Services; CPR = Bystander cardiopulmonary resuscitation performed; AED = Bystander use of automated external defibrillator.

Table 2: Raw Outcomes

Study Airway n ROSC (%) Admit (%) Survive (%) Neuro (%) Cady 2009 ETI 4335 1558 (35.9) 1112 (25.7) 279 (6.4) SGA 1487 508 (34.2) 377 (25.4) 97 (6.5) Hanif 2010 ETI 1027 244 (24) 152 (15) 38 (4) SGA 131 5 (4) 0 (0) Kajino 2011 ETI 1679 802 (47.8) 688 (41) 180 (10.7) 61 (3.6) SGA 3698 1643 (44.4) 1412 (38.2) 361 (9.8) 133 (3.6) McMullan 2014 ETI 5591 1890 (33.8) 1487 (26.6) 464 (8.3) 302 (5.4) SGA 3110 793 (25.5) 666 (21.4) 208 (6.7) 162 (5.2) Nagao 2012 ETI 10 1 (10) SGA 189 36 (19) Noda 2007 ETI 4 2 (40) 2 (40) 1 (20) 0 (0) SGA 24 5 (20.8) 4 (16.7) 3 (12.5) 0 (0) Shin 2012 ETI 250 55 (22) 20 (8) SGA 391 80 (20.5) 22 (5.6) Tanabe 2013 ETI 12992 853 (6.6) 474 (3.7) 162 (1.3) SGA 29640 1386 (4.7) 1060 (3.6) 310 (1.1) Wang 2012 ETI 8487 399 (4.7) SGA 1968 77 (3.9) Yanagawa 2010 ETI 158 18 (11.4) 2 (1.3) SGA 478 37 (7.7) 6 (1.3)

ETI = Endotracheal intubation; SGA = Supraglottic Airway; ROSC = Return of spontaneous circulation; Admit = Survival to hospital admission; Survive = Survival to hospital discharge; Neuro = Neurologically intact survival to hospital discharge

Table 3: Quality of Evidence

Study Study Risk of Indirectness Imprecision Publication Magnitude Residual Quality of Design Bias Bias of Effect Confounding Evidence Cady 2009 Cohort No No No No Not Large No Low Hanif 2010 Cohort Serious No Serious No Not Large N/A Very Low Kajino 2011 Cohort No No No No Not Large No Low McMullan 2014 Cohort No No No No Not Large No Low Nagao 2012 Cohort Serious No No No Not Large N/A Very Low Noda 2007 Cohort Serious No Serious No Not Large N/A Very Low Shin 2012 Cohort Serious No No No Not Large N/A Very Low Tanabe 2013 Cohort No No No No Not Large No Low Wang 2012 Cohort No No No No Not Large No Low Yanagawa 2010 Cohort Serious No No No Not Large N/A Very Low

Figure 2: Forest Plot for Return of Spontaneous Circulation

ETI = Endotracheal intubation; SGA = Supraglottic Airway; OR = Odds ratio; CI = Confidence interval

Figure 3: Forest Plot for Survival to Hospital Admission

ETI = Endotracheal intubation; SGA = Supraglottic Airway; OR = Odds ratio; CI = Confidence interval

Figure 4: Forest Plot for Survival to Hospital Discharge

ETI = Endotracheal intubation; SGA = Supraglottic Airway; OR = Odds ratio; CI = Confidence interval

Figure 5: Forest Plot for Neurologically Intact Survival to Hospital Discharge

ETI = Endotracheal intubation; SGA = Supraglottic Airway; OR = Odds ratio; CI = Confidence interval

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