16, 15, 13
The only controlled evidence that raising ECMO flow protects the brain in differential hypoxaemia, and the only evidence that the syndrome injures the brain within hours. It is a model, not a patient population, and it measured only one of the two organs at stake. Read alongside Chapter 15: the same manoeuvre that protects the brain here is the manoeuvre that distends the ventricle there.
Low ECMO flow 2.5 L/min, ensuring the brain was entirely perfused by the native heart and lungs (n=3)
DOI 10.1038/s41598-023-30226-6
Randomised to high ECMO flow 4.5 L/min, ensuring the brain was at least partly perfused by the circuit (n=3), for 5 hours
Three animals per group. Five-hour follow-up. Healthy young female sheep. Cannula position not varied. Neurobiomarkers unavailable in sheep; cerebral autoregulation not measurable. DECISIVE LIMITATION, stated by the authors: mortality and long-term outcome were not assessed, so the cerebral benefit of higher flow may not outweigh left ventricular damage from increased afterload.
PRIMARY OUTCOME - global histological brain injury score significantly worse in the low-flow group (p=0.0003); neuronal shrinkage, congestion and perivascular oedema all p<0.0001. Brain tissue oxygen tension change from baseline +215% (high flow) versus -58% (low flow), p=0.043. Cerebral NIRS 67 plus or minus 5% versus 49 plus or minus 4%, p=0.003. Cerebral blood flow 970 plus or minus 400 versus 205 plus or minus 76 arbitrary perfusion units, p=0.042. PaO2 p=0.006 and SaO2 p=0.041 both higher at high flow. Microdialysis showed no significant between-group difference but every low-flow value reached the predefined pathological threshold. Authors conclude differential hypoxaemia can cause cerebral damage after only a few hours and that increasing ECMO flow was an effective strategy to reduce it.
Six female Merino crossbred sheep, 45-60 kg, with ethanol-induced cardiogenic shock (EF under 30%, systolic pressure under 90 mmHg, lactate over 4 mmol/L, urine output under 0.5 mL/kg/h) plus induced respiratory failure (VT 4 mL/kg, PEEP 0, RR 5, FiO2 0.21), on femoral veno-arterial ECMO. Scientific Reports 2023;13:4002. Retrieved in full.