1. In this retrospective cohort study, increased surge index during the Delta wave was associated with worse survival across various hospitals in the United States.

2. The relationship between COVID-19 caseload stress and mortality was consistent across hospitals with varying size, location, and infrastructure.

Evidence Rating Level: 2 (Good)

Study Rundown: While over a year has passed since the World Health Organization declared COVID-19 to no longer constitute a public health emergency of international concern, the pandemic has led to lasting effects in U.S. hospitals, including burnout and worsening of pre-existing staffing shortages. Variations in resources and infrastructure have been shown to produce inequities in care, particularly under increased caseload strain. The Delta variant-predominant phase of the COVID-19 pandemic, spanning from June to December 2021, provided an important opportunity to investigate whether certain hospital types were more resilient to caseload stress. This period was optimal for analysis for several reasons: significant improvements in COVID-19 management and survivability by this point thus minimizing variations in care; relatively uniform presentations of patients acutely ill with the Delta variant; and the influx of cases on the background of significant staffing shortages. Hence, this retrospective cohort study aimed to determine whether the care infrastructure provided by hospitals in the United States would impact patient outcomes during the Delta wave surge. Overall, higher surge indices during the study period were associated with increased mortality rates across various U.S. hospitals. A similar relationship between COVID-19 caseload stress and mortality was seen across all hospital types despite their varying care infrastructure. Further, the surge-mortality relationship appeared to be incremental, with no clear surge index decile above which mortality increased drastically. The study was limited by residual confounding variables including patients’ vaccination status and the availability of specific hospital provisions like continuous renal replacement therapy. Nonetheless, this study demonstrated that caseload strain during the Delta wave had detrimental effects on survival independent of hospital care infrastructure.

Click to read the study in AIM

Relevant Reading: Trends in patient transfers from overall and caseload-strained US hospitals during the COVID-19 pandemic

In-Depth [retrospective cohort]: This retrospective cohort study aimed to determine whether hospital type affected patient outcomes during increased caseload stress associated with the Delta wave surge. Adults aged 18 years or older admitted to one of 620 U.S. hospitals between 1 July and 30 November 2021 were included. Hospitals were classified into 4 separate categories: ECMO-capable hospitals, non-ECMO multi-ICU hospitals, large single-ICU hospitals (200 beds or more), and small single-ICU hospitals (less than 200 beds). A previously validated surge index for each hospital-month was calculated by dividing the severity-weighted COVID-19 inpatient caseload by the hospital bed capacity. Of the 620 hospitals with at least one ICU, 208 were ECMO-capable, 216 were multi-ICU, 36 were large single-ICU, and 160 were small single-ICU. Of 2,687,526 patients admitted to these hospitals during the Delta wave, 223,380 with COVID-19 were included. A total of 50,752 of these patients (23%) were admitted to the ICU, 27,474 (12%) required mechanical ventilation, 463 received ECMO, and 34,273 (15.3%) died or were discharged to hospice. The marginally adjusted probability of mortality among inpatients with COVID-19 per unit increase in the log surge index was 5.51% (95% confidence interval [CI], 4.53% to 6.50%). Approximately 21.5% (number of deaths, 7375; 95% CI, 5936 to 8813) of COVID-19 deaths were potentially attributable to caseload surges. The adjusted marginal probability of mortality did not differ across the 4 hospital categories (P = 0.32). In summary, COVID-19 caseload stress was associated with increased mortality across all U.S. hospital types during the Delta wave surge.

Image: PD

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