Author contributions:-Zheng Jie LIM: This author has conceived the project idea, conducted the systematic review, statistical analysis, assisted with data analysis, wrote the initial drafts of the manuscript, created tables and figures and finalized the manuscript.-Ashwin SUBRAMANIAM: This author has conceived the project idea, conducted the systematic review, assisted with data analysis, wrote the initial drafts of the manuscript and finalized the manuscript.-Mallikarjuna REDDY: This author has conducted the systematic review, assisted with data analysis, wrote the initial drafts of the manuscript and finalized the manuscript.-Gabriel BLECHER: This author has analyzed the data and wrote the initial drafts of the manuscript and finalized the manuscript.-Umesh KADAM: This author has conducted the systematic review, assisted with data analysis, wrote the initial drafts of the manuscript and finalized the manuscript.

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Background The impact of COVID-19 on pre-hospital and hospital services and hence on the prevalence and outcomes of out-of-hospital cardiac arrests (OHCA) remain unclear. The review aimed to evaluate the influence of the COVID-19 pandemic on the incidence, process, and outcomes of OHCA. Methods A systematic review of PubMed, EMBASE, and pre-print websites was performed. Studies reporting comparative data on OHCA within the same jurisdiction, before and during the COVID-19 pandemic were included. Study quality was assessed based on the Newcastle-Ottawa Scale. Results Ten studies reporting data from 35,379 OHCA events were included. There was a 120% increase in OHCA events since the pandemic. Time from OHCA to ambulance arrival was longer during the pandemic (p = 0.036). While mortality (OR = 0.67, 95%-CI 0.49-0.91) and supraglottic airway use (OR = 0.36, 95%-CI 0.27-0.46) was higher during the pandemic, automated external defibrillator use (OR = 1.78 95%-CI 1.06-2.98), return of spontaneous circulation (OR = 1.63, 95%-CI 1.18-2.26) and intubation (OR = 1.87, 95%-CI 1.12-3.13) was more common before the pandemic. More patients survived to hospital admission (OR = 1.75, 95%-CI 1.42-2.17) and discharge (OR = 1.65, 95%-CI 1.28-2.12) before the pandemic. Bystander CPR (OR = 1.08, 95%-CI 0.86-1.35), unwitnessed OHCA (OR = 0.84, 95%-CI 0.66-1.07), paramedic-resuscitation attempts (OR = 1.19 95%-CI 1.00-1.42) and mechanical CPR device use (OR = 1.57 95%-CI 0.55-4.55) did not defer significantly. Conclusions The incidence and mortality following OHCA was higher during the COVID-19 pandemic. There were significant variations in resuscitation practices during the pandemic. Research to define optimal processes of pre-hospital care during a pandemic is urgently required. Review registration PROSPERO (CRD42020203371).

Objective: To explore associations between frailty (Clinical Frailty Scale score of 5 or more) in very old patients in intensive care units (ICUs) and their clinical outcomes (mortality, discharge destination).