The study of endothelin-1 in venous and arterial blood in mechanically ventilated COVID-19 critically ill patients

The aim of the present study was to measure endothelin-1 (ET-1) in the venous and arterial circulation of mechanically ventilated COVID-19-induced ARDS patients and to investigate whether abnormal metabolism of ET-1 prognosticates poor outcomes. ET-1 was measured in 18 mechanically ventilated COVID-19-induced ARDS patients, with simultaneous blood draw from the central vein and from a peripheral arterial line catheter, on days 1 and 3 following ICU admission. Two age- and sex-matched non-COVID-19 control groups were also used [mechanically ventilated non-COVID-19 critically ill (N=20) and ARDS (N=14) patients]. Venous and arterial ET-1 levels were measured in all patients. COVID-19-induced ARDS patients had statistically higher arterial and venous ET-1 levels compared to non-COVID-19 ARDS and critically ill patients (p<0.05). On ICU admission, the arterial:venous (A:V) ET-1 ratio was abnormal (1.1±0.07) only in the non-COVID-19 ARDS patients. The A:V ratio was 0.78±0.1 in the COVID-19-induced ARDS patients and 0.82±0.09 in the non-COVID-19 critically ill patients (p<0.05). On the 3rd day, the A:V ratio in all three groups was <1. The COVID-19 patient group was then subdivided based on 28-day mortality. Although arterial and venous levels did not differ, the A:V ratio tended to be higher (p= 0.07) on ICU admission in the non-survivors. Measurement of ET-1 clearance on ICU admission might be useful in stratifying COVID-19 critically ill patients according to outcomes.