Data released on May 8 by the UK’s Intensive Care National Audit & Research Centre (ICNARC) shows the mortality rate for 4287 COVID 19 patients who received advanced respiratory support was 58.8%. This figure is much lower than percentages of 86% to 97% as reported in earlier studies included in my March 30 post on this topic.
Advanced respiratory support was needed in 71% of 6143 critically ill patients with reported outcomes and was defined as invasive ventilation, bilevel positive airway pressure (BiPAP) via endotracheal tube or tracheostomy, continuous positive airway pressure (CPAP) via endotracheal tube, or extracorporeal respiratory support (known as ECMO in the US).
For the 1584 patients receiving basic respiratory support (>50% oxygen by facemask, chest physiotherapy and/or or suctioning of respiratory secretions at least every two hours, CPAP or BiPAP via mask or hood, and those intubated for airway protection only), 282 (17.8%) died.
Advanced cardiovascular support—such as IV rhythm controlling or vasoactive drugs, intra-aortic balloon pumps, or temporary cardiac pacemakers—was required in 1644 (38.4%) advanced respiratory support patients. Renal support with acute renal replacement therapy (RRT) or RRT for chronic renal failure combined with other organ support was provided in 1374 (32.1%) patients.
Of the 817 patients needing advanced respiratory support who were under the age of 50, 265 (32%) died compared to a mortality rate of 65% for patients ≥ 50 years old.
Critically ill patients with COVID-19 pneumonia died about twice as frequently as those with non-COVID-19 viral pneumonia. The figure below shows that a higher percentage of patients with a body mass index of 25-30 died than those with a BMI ≥ 40 suggesting that obesity may not be as big a risk factor as found in previous studies.
The mortality rate for patients with very severe comorbidities was 73.4% vs. 57.9% for those without. Very severe comorbidities were defined as cardiovascular symptoms at rest, shortness of breath with light activity, end-stage renal disease with RRT, biopsy-proven cirrhosis with portal hypertension or hepatic encephalopathy, metastatic cancer, leukemia, multiple myeloma, or lymphoma, and immunosuppressed patients on chemotherapy, radiation, or high dose steroids in the last six months, and HIV/AIDS or congenital immune deficiency. Diabetes was apparently not part of the data collection.
A recent study from the University of Oxford and the London School of Hygiene & Tropical Medicine listed the following as risk factors for COVID-19 mortality: uncontrolled diabetes, male sex, advanced age, black or Asian ethnicity, social deprivation, and asthma. Obesity was not mentioned.
The ICNARC data is one of the largest and most comprehensive COVID-19 studies published to date and helps to clarify the impact of advanced respiratory support on mortality. As the pandemic evolves and intensivists learn more about the disease, I expect to see a continuing decline in the mortality rate of critically ill patients on ventilators.
Acknowledgment: This data is derived from the ICNARC Case Mix Programme Database. The Case Mix Programme is the national clinical audit of patient outcomes from adult critical care coordinated by ICNARC. For more information on the representativeness and quality of these data, please contact ICNARC.