COVID19 - Haemodynamic Monitoring
Presently there are no specific therapeutic agents for Covid19; While the immune system is fighting the virus it is vital to optimise organ perfusion. To achieve this appropriate haemodynamic monitoring is essential.
Fluid overload will seriously compromise lungs with pre-existing high levels of extravascular lung water and impaired capillary integrity. Remember, that excessive doses of fluid dilutes the haemoglobin concentration (Hb) and presupposes that the cardiac output can increase to compensate for this. As myocardial depression can be severe in Covid-19 infection, there may be no increase in CO following intravenous fluid and a consequent net reduction in DO2.
As many ICU patients with Covid-19 are on mechanical ventilators, it is essential to ensure that the PEEP setting is “balanced”, optimising ventilation without adversely affecting perfusion. Excessive PEEP will reduce preload and compromise CO, with a reduction in oxygen delivery (DO2). DO2 = Hb x 1.34 x SV x HR x SPo2. Monitoring DO2 enables PEEP to be optimised - "best PEEP"
Around 50% of ventilated Covid-19 patients recover but the other half do not. It has been shown that many of these sustain myocardial injury or severe myocardial depression. Regular measurement of the inotropy level of the heart provides an early warning and indication of the severity of myocardial depression, permitting earlier and appropriate intervention, e.g. suitable inotropic support at an appropriate dose to correct or normalise the inotropic index (SMII).