Low versus standard-blood-flow reperfusion strategy in a pig model of refractory cardiac arrest resuscitated with Extra Corporeal Membrane Oxygenation.

OBJECTIVE: This study was designed to assess the effect of two veno-arterial ExtraCorporeal Membrane Oxygenation (ECMO) blood-flow strategies in an experimental model of Extracorporeal Cardio-Pulmonary Resuscitation (ECPR) on macrocirculatory, metabolic and microcirculatory parameters in the first six hours of ECMO initiation.

METHODS: Cardiac arrest was induced in 18 pigs by surgical ligature of the left descending coronary artery followed by a low-flow time of 40 min using internal cardiac massage. ECPR was initiated in normothermia with an ECMO blood flow of 30-35 ml.kg-1 . min-1 (low-blood-flow group, LBF) or 65-70 ml.kg-1 . min-1 (standard-blood-flow group, SBF), with the same mean arterial pressure target of 65 mmHg adjusted with norepinephrine. Macrocirculatory and metabolic parameters were assessed by lactate clearance and carotid blood flow. Microcirculatory parameters were assessed by sublingual microcirculation with Sidestream Dark Field (SDF) imaging and peripheral Near-InfraRed Spectrometry (NIRS). Inflammatory cytokine levels were measured with a multicomplexed ELISA-based array platform.

RESULTS: There were no between-group differences at baseline and at ECMO initiation (H0). Lactate clearance at H6 was lower in LBF compared to SBF (6.67[-10.43-18.78] vs. 47.41[19.54-70.69] %, p = 0.04). Carotid blood flow was significantly lower (p<0.005) during the last four hours despite similar mean arterial pressure levels. For microvascular parameters, SDF and NIRS parameters were transitorily impaired at H3 in LBF. IL-6 cytokine level was significantly higher in LBF at the end of the experiment.

CONCLUSION: In an experimental porcine model of refractory cardiac arrest treated by ECMO, a low-blood-flow strategy during the first six hours of resuscitation was associated with lower lactate clearance and lower cerebral blood flow with no benefits on ischemia-reperfusion parameters.