Traumatology

CAB versus ABC approach for resuscitation of patients following traumatic injury: Toward improving patient safety and survival

a b s t r a c t

Introduction: Though a circulation-airway-breathing (CAB) resuscitation sequence is now widely accepted in ad- ministering CPR over the airway-breathing-circulation (ABC) sequence following cardiac arrest, current evidence and guidelines vary considerably for complex polytraumas, with some prioritizing management of the airway and others advocating for initial treatment of hemorrhage. This review aims to evaluate existing literature com- paring ABC and CAB resuscitation sequences in adult trauma patients in-hospital to direct future research and guide evidence-based recommendations for management.

Methods: A literature search was conducted on PubMed, Embase, and Google Scholar until September 29, 2022. Articles were assessed for comparison between CAB and ABC resuscitation sequences, adult trauma patients, in- hospital treatment, patient volume status, and clinical outcomes.

Results: Four studies met the inclusion criteria. Two studies compared the CAB and ABC sequences specifically in hypotensive trauma patients, one study evaluated the sequences in trauma patients with hypovolemic shock, and one study in patients with all types of shock. Hypotensive trauma patients who underwent rapid sequence intubation before blood transfusion had a significantly higher mortality rate than those who had blood transfu- sion initiated first (50 vs 78% P < 0.05) and a significant drop in blood pressure. Patients who subsequently ex- perienced post-intubation hypotension (PIH) had increased mortality over those without PIH. overall mortality was higher in patients that developed PIH (mortality, n (%): PIH = 250/753 (33.2%) vs 253/1291 (19.6%), p < 0.001).

Conclusion: This study found that hypotensive trauma patients, especially those with Active hemorrhage, may benefit more from a CAB approach to resuscitation, as early intubation may increase mortality secondary to PIH. However, patients with critical hypoxia or airway injury may still benefit more from the ABC sequence and prioritization of the airway. Future prospective studies are needed to understand the benefits of CAB with trauma patients and identify which patient subgroups are most affected by prioritizing circulation before airway management.

(C) 2023

  1. Background

Airway-breathing-circulation (the ABC approach) is a resuscitation sequence that was developed for assessing and treating critically in- jured trauma patients in the 1970s. Since then, it has been widely

* Corresponding author at: Department of Surgery, Division of Trauma and Surgical Critical Care, Orlando Regional Medical Center, 82 W Underwood St., Orlando, FL 32806, USA.

E-mail address: [email protected] (A. Elkbuli).

accepted and used by experts in emergency medicine and trauma to guide resuscitation and improve outcomes in trauma patients [1]. How- ever, the evidence supporting the ABC approach for more complex polytraumas is largely based on expert consensus, rather than evidence-based medicine [1,2]. In the setting of polytrauma, patients often present with more complicated, life-threatening injuries, includ- ing massive hemorrhage and critical airway compromise; as such, a de- cision must be made as to which injury Resuscitative efforts should prioritize [3]. While the circulation-airway-breathing (CAB) sequence, sometimes referred to as cABC (c = major hemorrhage A = airway ob- struction B = chest injuries C = circulatory shock) to emphasize the

https://doi.org/10.1016/j.ajem.2023.02.034

0735-6757/(C) 2023

importance of hemorrhage management, is now a widely accepted se- quence for administering CPR compared to the ABC sequence in cardiac arrest, it remains to be seen how the two techniques compare in com- plex trauma situations. Additionally, this introduces questions as to what clinical scenarios are appropriate for each resuscitative sequence, how clinical judgment may play a role in guiding these practices in trauma patients, and how guidelines regarding CAB or ABC techniques could be improved for resuscitation in trauma accordingly [4].

Currently, there is a paucity of evidence that directly compares re- suscitative algorithms in the polytrauma patient [3]. Existing guidelines vary considerably in their recommendations, with some prioritizing management of the airway through strategies such as rescue breathing, intubation, and Tension pneumothorax decompression while others ad- vocate for initial control of circulation through management of intrave- nous access, Hemorrhage control, and leg elevation [1]. Current literature primarily examines the effect of CAB on the employment time of cardiopulmonary resuscitation in patients suffering from cardiac arrest in prehospital trauma patients. Additionally, recent studies have found increased morbidity and mortality associated with prehospital in- tubation in trauma patients, particularly those with hemorrhagic shock [5-7]. However, there are few studies that compare clinical outcomes between the two algorithms for trauma patients within the hospital set- ting, further illustrating a gap in the literature needed to appropriately determine which algorithm is most suitable for patients arriving with complex polytraumas.

While the CAB sequence has been widely studied for pre-hospital re- suscitation, current guidelines for the most appropriate resuscitation se- quence in complex polytrauma patients in-hospital are mixed in their recommendations and lack substantial evidence. The primary objective of this review is to evaluate the existing literature comparing ABC and CAB resuscitation sequences implemented for traumatically injured adult patients in-hospital to best direct further research and guide evidence-based recommendations for managing these patients.

  1. Methods

We conducted a literature search on databases including PubMed, Embase, and Google Scholar for studies published from database con- ception to September 29, 2022. The search utilized keywords including “CAB and ABC,” “circulation first,” “CAB” AND “trauma,” “CAB” AND “re- suscitation,” “CAB” AND “guidelines.” Articles were initially searched, and their titles and abstracts were screened for relevance by all authors. References from included studies were then screened for relevance.

The full text of selected articles was then reviewed and analyzed by all authors.

Studies were included in this review if they were peer-reviewed, in English, and compared outcomes of adult trauma patients undergoing either ABC or CAB resuscitation sequencing in in-hospital settings. Arti- cles excluded were case reports, case series, studies that did not include trauma patients, studies that provided information on resuscitation without any mention of CAB, or studies that were written in a language other than English. Articles in this review were assessed for an in- hospital setting, trauma, volume status of the patient population, resus- citation sequencing, and clinical outcomes. After applying exclusion criteria, this literature search ultimately yielded 4 studies (Table 1).

  1. Results

Four studies were included in this narrative review that compared CAB vs ABC Resuscitation algorithms. Two studies compared algorithms specifically in hypotensive trauma patients [8,9], one study evaluated the algorithms in trauma patients with hypovolemic shock [2], and one study in patients with all types of shock [2,10]. Results were separated into two categories, hypotensive trauma patients and trauma patients with shock, as some studies addressed hypotension indepen- dently without explicitly meeting criteria for shock. A summary of the literature and recommended practices in guidelines by Advanced Trauma Life Support (ATLS) can be found in the practice algorithm in Fig. 1. This algorithm prioritizes circulation in hypotensive trauma pa- tients without critical hypoxia or dynamic airway injury and recom- mends targeted management of ventilation impairment if hypoxia or airway injury is present.

    1. Hypotensive trauma patients

Before 2010, the Resuscitation protocol in hypotensive trauma pa- tients would first include airway management and intubation before addressing the patients’ underlying hemodynamic instability [4]. How- ever, it has been noted that early intubation and ventilation can result in deleterious effects, such as compromising venous return, decreasing ce- rebral perfusion, and subsequent worsening of hypotension [7,11].

More recent studies investigated outcomes associated with intuba- tion in hemodynamically unstable trauma patients. In 2018, Ferrada compared the use of Rapid Sequence Intubation and blood transfu- sions in hypotensive trauma patients in the hospital and found that pa- tients who underwent RSI before blood transfusion had a significantly

Table 1

Studies Comparing CAB versus ABC Approach for Resuscitation in Trauma Patients.

Authors Year Design Study Description Reported Outcomes Additional Comments

Ferrada 2018 Retrospective Analysis of 229 hypotensive trauma patients who

underwent RSI before blood transfusion (ABC) or blood transfusion before RSI (CAB).

Patients who underwent RSI before blood transfusion (ABC) had a significantly higher mortality rate than those who had blood transfusion initiated first (CAB) (50% vs 78% p < 0.05).

RSI resulted in Hemodynamic deterioration in 75% of the already hypotensive patients.

Ferrada et al.

Petrosoniak and Hicks

Ferrada et al.

2018 Retrospective Analysis of 440 hypotensive trauma patients, 245

(55.7%) received intravenous blood product resuscitation first (CAB), and 195 (44.3%) were intubated before any resuscitation was started (ABC).

2018 Review Literature review challenges the conventional ABC

sequence that can at times inappropriately prioritize less urgent interventions over treatment for more critical injuries.

2019 Meta-analysis Meta-analysis including 2044 trauma and acute

patients across four studies that underwent intubation and developed PIH.

Those intubated prior to receiving transfusion had a lower GCS than those with transfusion initiation prior to intubation (ABC: 4, CAB:9, p = 0.005).

There was no statistically significant difference in mortality between cohorts (CAB 47% and ABC 50%). Authors propose the use of evidence-based methods for shock identification to apply effective trauma resuscitation, placing emphasis on prioritizing circulation in patients without critical hypoxia or dynamic airway injury.

Overall mortality rates were higher in trauma patients who developed PIH (mortality, n (%): PIH = 250/753 (33.2%) vs 253/1291 (19.6%), p < 0.001).

N/A

No single indicator can predict both presence and degree of shock in trauma patients reliably

N/A

Abbreviations: ABC = Airway-Breathing-Circulation, CAB = Circulation-Breathing-Airway, RSI = Rapid Sequence Intubation, GCS = Glasgow Coma Scale, PIH = Post-Intubation Hypotension, NA = Not Applicable.

Fig. 1. Proposed Resuscitation Algorithm for In-Hospital Trauma Patients.

higher mortality rate than those who had blood transfusion initiated first (50 vs 78%; P < 0.05) [8]. Furthermore, RSI resulted in significant decreases in the systolic and diastolic blood pressures in 75% of the already hypotensive patients (SBP mean drop: -18 mmHg and SBP median drop: -15 mmHg) [8].

Following that, Ferrada et al. conducted a meta-analysis in 2019 that evaluated the effect of post-intubation hypotension (PIH) on mortality in hypovolemic trauma and acute patients in the hospital [9]. The pop- ulation was heterogeneous and included critically ill medical (n = 1391, 68%) and trauma patients (n = 653, 32%) [9]. They found that overall mortality was higher in patients that developed PIH (mortality, n (%): PIH = 250/753 (33.2%) vs 253/1291 (19.6%), p < 0.001) [9].

Accordingly, the authors argue in favor of a CAB sequence in the resus- citation of the hypotensive hypovolemic patient by expediting Bleeding control while obtaining airway access [9].

    1. Trauma patients with shock

In 2018, Ferrada et al. investigated mortality rates by comparing in- hospital CAB to ABC algorithms in bleeding adult trauma patients with hypovolemic shock [2]. Of these patients, 33.6% suffered from a pene- trating mechanism of injury [2]. A majority of patients (245, 55.7%) un- derwent the CAB sequence (i.e. received intravenous blood product resuscitation first) [2]. Patients in the CAB group had a higher average

initial Glasgow Coma Scale (GCS) of 9 compared to 4 in the ABC group (p = 0.0005) [2]. The CAB group additionally presented with a lower initial emergency department diastolic blood pressure of 48 mmHg ver- sus 51 mmHg in the ABC group (p = 0.03). Overall, no statistically sig- nificant difference in mortality between the two groups was found (CAB 47% and ABC 50%, p = 0.63) [2].

A review article by Petrosoniak and Hicks in 2018 outlined an Evidence-based approach to resuscitation of trauma patients presenting to the emergency department with shock [10]. They call into question the traditional A-B-C-D-E sequence (airway, breathing, circulation, dis- ability, environment and exposure), arguing against this scripted protocol and instead favoring an approach that is based on physiologic priorities [10]. The authors contend that airway management is favored in trauma patients in hospital when there is critical hypoxia or dynamic airway in- jury; otherwise, a focus on circulation is preferred [10]. Furthermore, in these two circumstances, a highly trained team can still address shock states concurrent with management of the airway [10].

  1. Discussion

Addressing the resuscitation sequence in trauma patients with hy- potension and hypovolemic shock is critical to improving patient care, especially given that hemorrhage is responsible for up to 40% of trauma-related mortalities [12]. In adult trauma patients presenting with hypotension, this review identified that initial airway manage- ment with intubation can induce further postintubation hypotension, exacerbating their condition and leading to increased mortality [2,8,9]. The Incidence of PIH can be as high as 36.3%; however, its impact in the trauma population remains poorly understood [9,13]. Instead, it is recommended that addressing problems with circulation, namely active hemorrhage, should occur before intubation in hypovolemic trauma patients unless there is evidence of critical hypoxia or dynamic airway injury [10]. Several guidelines support this recommendation, including Battlefield Advanced Life Trauma Support (BATLS), Prehospital Trauma Life Support (PHTLS), and the European Trauma Course [14-16]. However, Advanced Trauma Life Support (ATLS) currently supports the assessment and treatment of life-threatening problems with airway and breathing problems before addressing circulation [17]. Together, these findings challenge the traditional notion that establishing an airway should always be the primary focus after trauma, instead identi- fying the potential harm in intubating a hypovolemic patient and em- phasizing the need for provider discretion in delivering resuscitative care based on the patient’s most life-threatening injuries.

Studies in our review investigated use of the CAB sequence in unstable patients with hypotension secondary to trauma. One study demonstrated a significantly higher mortality rate in patients who un- derwent RSI before blood transfusion compared to those who had blood transfusion initiated first [8]. Prioritizing RSI was found to signif- icantly exacerbate unstable blood pressure in these patients, resulting in post-intubation hypotension. A meta-analysis assessing PIH found that overall mortality was higher in hypotensive trauma patients who subse- quently developed further post-intubation hypotension [9]. Guidelines by Petrosoniak and Hicks also recognize the risks of post-intubation hypotension, and recommend invasive airway management only after other life threatening injuries have been managed [10].

This review additionally evaluated ABC versus CAB in the setting of shock, specifically addressing hypovolemic shock following massive hemorrhage. In the 2018 study by Ferrada et al., results did not identify a mortality difference when comparing ABC to CAB in the hypovolemic trauma patient [2]. However, prior studies have demonstrated that prompt initiation of massive transfusion protocols (MTP) is a major de- terminant of outcome in trauma patients with active hemorrhage. These studies found that rapid initiation of MTP through blood products available in the trauma bay led to significantly decreased mortality, supporting many of the current guidelines’ recommendations for initi- ating circulatory resuscitation first in patients with active bleeding

[18,19]. We recognize, however, that blood products, especially those required for initiation of rapid MTP may not always be readily available and should not delay prompt resuscitation of the airway in the event of their absence. The conflicting results on mortality between the 2018 Ferrada et al. study and studies supporting the use of rapid MTP suggest that providers may already be using clinical judgment to determine re- suscitation sequence based on patient presentation. Those with more critical airways were intubated first, while those with significant hypo- tension but no critical airways were resuscitated first. While our results support provider discretion in determining the best resuscitation mo- dality to begin with based on presenting injuries, more research is needed to provide stronger evidence for the use of CAB vs ABC in vary- ing scenarios.

Guidelines addressing the use of the CAB vs ABC sequence in poly- trauma patients remain divided on their recommendations. The 2018 ATLS continues to recommend an “ABCDE” approach, standing for: air- way with restriction of Cervical spine motion, breathing, circulation in- cluding hemorrhage control, disability or neurologic status, exposure of the patient, and environment (Temperature control) [17]. Moreover, they suggest prioritizing the airway first over circulation, stating that the loss of an airway results in mortality more quickly than a loss of cir- culation [17]. Contrary to this, other guidelines including the Battlefield Advanced Life Trauma Support (BATLS), the Prehospital Trauma Life Support (PHTLS), and various European societies representing the European Trauma Course prioritize control of hemorrhage as the initial step in resuscitation [14-16]. BATLS defines four stages of trauma care, the most advanced being Field Resuscitation and Advanced Resuscita- tion where they emphasize prioritizing the correction of catastrophic hemorrhage [16]. PHTLS currently recommends prioritizing the man- agement of hemorrhage before establishing an airway, breathing, and circulation [14]. The European Trauma Course advises a holistic assess- ment of trauma patients, but recommends starting with injuries in the order of cABC (prioritizing hemorrhage control) before determining if there is any need to deviate from this protocol [15].

While there are currently guidelines on resuscitation using the ABC sequence from different trauma and emergency services associations, only those from BATLS, PHTLS, and the European Trauma Course pro- vide specific guidelines for CAB in trauma patients [14-16]. This may be owing to the paucity of evidence describing CAB outcomes in trauma patients. Based on the findings in this review, we recommend future prospective studies to better understand the clinical advantages of CAB and to identify the patient subgroups most likely to benefit or suffer by prioritizing control of circulation before airway management. Ran- domized studies are also needed to identify the most appropriate circu- lation management strategies in order to update guidelines that more accurately reflect the complexities of trauma situations. Finally, the findings of this review included specific practices for the management of hypotensive trauma patients. Thus, we recommend investigating the role of Postintubation hypotension in management of poly- trauma patients. Lastly, we recommend updating courses such as the ATLS to provide education on evidence-based practices for CAB in the trauma population in centers where resources and experienced trauma surgeons are available.

  1. Limitations

This review presents several limitations. The value of a literature re- view is dependent on the Level of evidence of the studies included only 2 retrospective cohort studies were identified, and we were unable to identify any randomized controlled trials that evaluated ABC vs CAB in trauma patients or simulated in-hospital trauma scenarios. Three of our identified articles were published by the same first author, which increases the likelihood of bias as this author may be biased toward val- idating prior work. In Ferrada et al. 2018, patients who underwent ABC presented in more severe condition (determined by Glasgow Coma Score and diastolic blood pressure) than the CAB patients, though due

to the retrospective nature of the study it is unclear if the trauma centers were implementing an evidence-based approach to assigning a resusci- tation sequence or if patients received either of the sequences due to physician clinical gestalt [2]. This study also did not stratify the cause of hypovolemia; as such, atraumatic etiologies may have been inadver- tently included in the cohort. Additionally, in the meta-analysis per- formed by Ferrada et al. 2019, the included studies represented a heterogenous population of both critically ill Medical patients (n = 1391, 68%) and trauma patients (n = 653, 32%) [9]. Given that critically ill patients comprised the majority, outcomes may be skewed by the lower percentage of the trauma population. Finally, we recognize that studies comparing these two algorithms in-hospital are difficult in prac- tice, as many acute trauma patients often receive both ventilatory and circulatory resuscitative measures concurrently in the trauma bay. However, we believe that in situations where provider access is limited, such as rural areas, education on the best resuscitation sequence to ini- tiate for different scenarios can potentially be a life saving intervention.

  1. Conclusion

Findings from this review indicate that current evidence supports the benefits of CAB approach to resuscitation in some trauma patients, particularly for those with hypotension and who do not require imme- diate intubation. Initial airway management with intubation can signif- icantly lower blood pressure in already hypotensive patients and lead to increased mortality. Although several trauma societies currently support addressing circulation first during the resuscitation of trauma patients, others still support the assessment and treatment of life- threatening problems with the airway and breathing before circulation. Future prospective studies are needed to understand the benefits of CAB in trauma patients and to identify which patient subgroups would most benefit from prioritizing circulation before airway management.

Author contribution

Study design and conception: AE.

Data collection, analysis, and interpretations: TB, BM, JK, JK, AE. Manuscript preparation: TB, BM, JK, JK, AE.

Critical revision of the manuscript: TB, BM, JK, JK, HH, WH, AE. All authors read and approved the final manuscript.

Conflict of interest/disclosures

Authors disclose no competing interest.

Funding/financial disclosure

None.

Conflicts of interests

Authors declare no competing interest.

CRediT authorship contribution statement

Tessa Breeding: Writing – review & editing, Writing – original draft, Methodology, Investigation, Data curation. Brian Martinez:

Writing – review & editing, Writing – original draft, Methodology, Investigation, Data curation. Joshua Katz: Writing – review & editing, Writing – original draft, Investigation, Data curation. Jason Kim: Writ- ing – review & editing, Writing – original draft, Investigation, Data curation. Will Havron: Writing – review & editing, Investigation. Heather Hoops: Writing – review & editing, Investigation. Adel Elkbuli: Writing – review & editing, Writing – original draft, Supervision, Resources, Project administration, Methodology, Investigation, Data curation, Conceptualization.

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