Clinical paperSodium bicarbonate administration is associated with improved survival in asystolic and PEA Out-of-Hospital cardiac arrest
Introduction
Though out-of-hospital cardiac arrest (OHCA) recommendations have included the use of sodium bicarbonate (NaHCO3, hereafter “bicarb”) for nearly-four decades, the effectiveness of this medication has limited evidence. Bicarb is thought to combat acidosis arising during cardiac arrest by buffering acid-base imbalances.1 Severe acidosis (pH < 7.2) suppresses myocardial contractility, possibly through hyporesponsiveness to inotropes and vasopressors.2, 3, 4, 5, 6 Thus, bicarb administration potentially offers a promising therapy to minimize acidosis and therefore reduce injury and death.
Some studies support the use of bicarb in OHCA.7, 8, 9, 10 However, several studies from recent years have failed to support its use in OHCA, citing either no difference in outcomes or an association with poorer outcomes.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Proposed explanations for adverse effects are hypernatremia, inhibited oxygen release from hemoglobin, reduction of systemic vascular resistance, and inactivation of simultaneously-administered catecholamines. Nevertheless, in many of these observational studies, bicarb was often given late in the resuscitation after earlier resuscitative attempts are not successful. Thus, the association of bicarb with poor outcomes is confounded by long resuscitation attempts which have inherently poor prognoses. More recent updates to the American Heart Association guidelines have removed support for bicarb administration and recommend use only in cases of cyclic antidepressant overdose, ventricular arrhythmias, and hyperkalemic cardiac arrests.20, 21, 22, 23 While frequency of bicarb administration in OHCA has decreased in recent years, prehospital use remains variable.7, 24
There is a need to investigate the impact of bicarb on cardiac arrest outcomes when controlling for known predictors of OHCA outcomes, including the length of the resuscitation attempt. In this work, we sought to investigate the use of bicarb in OHCA and associated outcomes through analysis of a nationwide database of EMS-treated patients with cardiac arrest.
Section snippets
Study design and setting
We conducted a nationwide retrospective cross-sectional study of EMS-treated OHCA using fully anonymized prehospital electronic health records maintained by the ESO Data Collaborative (Austin, TX). As of 2019, the ESO database contains de-identified EMS records from 1,322 participating agencies across all fifty states and provides comprehensive clinical information including demographics, treatments, and pertinent timestamps for each medical event. Data collected within the ESO database are
Results
Of the 148,110 cardiac arrests in the database between January 2019 and December 2020, 23,567 (15.9 %) met the inclusion criteria (Fig. 1). Median age was 68 years (IQR 57–78 years) and 38.2 % were female. Most patients had a presenting rhythm of asystole (67.4 %), followed by PEA (16.6 %), and VF/VT (15.1 %). Overall, bicarb was administered in 28.3 % of cases. Bicarb was administered most often to patients with a presenting rhythm of asystole (29.5 %), followed by PEA (27.3 %), and then VF/VT
Discussion
Using a large national sample of more than 23,000 EMS records with linked hospital outcome data for patients with non-traumatic cardiac arrest, we observed significant improvements in ROSC and survival for patients receiving prehospital bicarb when presenting with non-shockable rhythms, after adjustment for confounding variables. There were no associations between bicarb use status and outcomes for patients presenting with shockable rhythms (VF/VT). Collectively, these findings suggest that
Conclusions
In this large propensity score-matched analysis, prehospital bicarb was associated with increased survival to hospital discharge in patients experiencing OHCA. Specifically, patients presenting with asystole and PEA in out-of-hospital cardiac arrest had more favorable survival outcomes when administered prehospital bicarb than those not receiving bicarb, after accounting for important arrest characteristics. Additional prospective work is needed to confirm these findings and establish causality.
CRediT authorship contribution statement
Sara M. Niederberger: Investigation, Methodology, Software, Formal analysis, Resources, Data curation, Writing – original draft, Visualization, Funding acquisition. Remle P. Crowe: Software, Validation, Formal analysis, Data curation, Writing – review & editing. David D. Salcido: Software, Validation, Formal analysis, Writing – review & editing. James J. Menegazzi: Conceptualization, Methodology, Validation, Formal analysis, Resources, Supervision, Writing – review & editing, Visualization,
Acknowledgements
The authors thank Chase Zikmund for the technical support.
Sources of funding
Research reported in this publication was supported in part by University of Pittsburgh School of Medicine T35 Grant Award (5T35DK065521-17) from the National Institutes of Health.
Disclosures
Dr. Crowe is employed by ESO. The authors have nothing else to disclose in relation to this work.
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