Etiologies of In-hospital cardiac arrest: A systematic review and meta-analysis

Background: Etiologies of in-hospital cardiac arrest (IHCA) in general wards may differ from etiologies of out-of-hospital cardiac arrest (OHCA) given the different clinical characteristics of these patient populations. An appreciation for the causes of IHCA may allow the clinician to appropriately target root causes of arrest. Methods: MEDLINE/PubMed, EMBASE, and Google Scholar were queried from inception until May 31, 2021. Studies reporting etiologies of IHCA were included. A random effects meta-analysis of extracted data was performed using Review Manager 5.4. Results: Of 12,451 citations retrieved from the initial literature search, 9 were included in the meta-analysis. The most frequent etiologies of cardiac arrest were hypoxia (26.46%, 95% confidence interval [CI] 14.19–38.74%), acute coronary syndrome (ACS) (18.23%, 95% CI 13.91–22.55%), arrhythmias (14.95%, 95% CI 0–34.93%), hypovolemia (14.81%, 95% CI 6.98–22.65%), infection (14.36%, 95% CI 9.46–19.25%), and heart failure (12.64%, 95% CI 6.47–18.80%). Cardiac tamponade, electrolyte disturbances, pulmonary embolism, neurological causes, toxins, and pneumothorax were less frequent causes of IHCA. Initial rhythm was unshockable (pulseless electrical activity or asystole) in 69.83% of cases and shockable (ventricular tachycardia or ventricular fibrillation) in 21.75%. Conclusion: The most prevalent causes of IHCA among the general wards population are hypoxia, ACS, hypovolemia, arrythmias, infection, heart failure, three of which (arrhythmia, infection, heart failure) are not part of the traditional “H's and T's” of cardiac arrest. Other causes noted in the “H's and T's” of advanced cardiac life support do not appear to be important causes of IHCA.