Excess Out-of-Hospital Mortality and Declining Oxygen Saturation: The Sentinel Role of Emergency Medical Services Data in the COVID-19 Crisis in Tijuana, Mexico

Abstract

Objective Emergency medical services (EMS) may serve as a key source of real-time data about the evolving health of COVID-19 affected populations, especially in low-and-middle-income countries (LMICs) with less rapid and reliable vital statistic registration systems. Although official COVID-19 statistics in Mexico report almost exclusively in-hospital mortality events, excess out-of-hospital mortality has been identified in other countries, including one EMS study in Italy that showed a 58% increase. Additionally, EMS and hospital reports from several countries have suggested that silent hypoxemia—low oxygen saturation (SpO2) in the absence of dyspnea—is associated with COVID-19. It is unclear, however, how these phenomena can be generalized to LMICs. We assess how EMS data can be used in a sentinel capacity in Tijuana, a city on the Mexico-United States border with earlier exposure to COVID-19 than many LMIC settings. Methods In this observational study, we calculated numbers of weekly out-of-hospital deaths and respiratory cases seen by EMS in Tijuana, and estimate the difference between peak-epidemic rates and expected trends based on data from 2014-2019. Results were compared with official COVID-19 statistics, stratified by neighborhood socioeconomic status (SES), and examined for changing demographic or clinical features, including mean SpO2. Results An estimated 194.7 (95%CI: 135.5-253.9) excess out-of-hospital deaths events occurred during the peak window (April 14 th -May 11 th ), representing an increase of 145% (70%-338%) compared to expected levels. During the same window, only 5 COVID-19-positive, out-of-hospital deaths were reported in official statistics. This corresponded with a rise in respiratory cases of 236.5% (100.7%-940.0%), and a drop in mean SpO2 to 77.7%, from 90.2% at baseline. The highest out-of-hospital death rates were observed in low-SES areas, although respiratory cases were more concentrated in high-SES areas. Conclusions EMS systems may play an important sentinel role in monitoring excess out-of-hospital mortality and other trends during the COVID-19 crisis in LMICs. Using EMS data, we observed increases in out-of-hospital deaths in Tijuana that were nearly threefold greater magnitude than increases reported in EMS data in Italy. Increased testing in out-of-hospital settings may be required to determine if excess mortality is being driven by COVID-19 infection, health system saturation, or patient avoidance of healthcare. We also found evidence of worsening rates of hypoxemia among respiratory patients seen by EMS, suggesting a possible rise in silent hypoxemia, which should be met with increased detection and clinical management efforts. Finally, we observed that social disparities in out-of-hospital death that warrant monitoring and amelioration.

Effect of COVID19 on prehospital pronouncements and ED visits for stroke and myocardial infarction

“…Baldi et al compared the number of pronouncements in Lombardi, Italy in a two-month period from the end of February to the end of April during COVID19 in 2020 with the same period in 2019 and found a 62% increase, which is considerably less than our 183% increase [ 13 ]. Friedman et al found a 145% increase in out-of-hospital deaths in Tijuana following arrival of COVID19 there [ 14 ]. In the six-week period of the pandemic in Paris, compared to the same six-week periods in 2012–2020 prehospital deaths following OHCA increased 54% [ 12 ].…”

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“…According to data from the Office of National Statistics (ONS) and Public Health England, occupation and socio-economic deprivation play key roles in the risk of COVID-19 infection and poor outcomes in BAME communities [ 25 , 26 ]. In Latin America mortality during the COVID-19 pandemic is reported to be higher in low socio-economic status neighbourhoods and rural communities [ 27 , 28 ]. Limited access to health care, greater social mixing, unemployment, and lower ability to work from home in the vulnerable populations are likely relevant in conferring this increased risk [ 29 ].…”

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“…Despite the biological plausibility on which we built the grounds for our hypothesis, we acknowledge its speculative nature as a potential field for future research. However, it is safe to conclude from our data that clinicians should be aware of nondyspnogenic acute hypoxemic respiratory failure in COVID-19 and possibly increase surveillance mechanisms (e.g., pulse oximetry monitoring), particularly in highrisk populations (46). Assuming that further studies would confirm the hypothesis that SARS-CoV-2 infection is associated with marked respiratory autonomic dysfunction, we could also expect cardiovascular autonomic dysfunction to participate in the pathophysiology of cardiovascular manifestations, including heart failure and cardiac arrhythmias, and related clinical outcomes.…”