Ischemic preconditioning does not prevent placental dysfunction induced by fetal cardiac bypass

Remote ischemic preconditioning (rIPC) has been applied to attenuate tissue injury. We tested the hypothesis that rIPC applied to fetal lambs undergoing cardiac bypass (CB) reduces fetal systemic inflammation and placental dysfunction.

Eighteen fetal lambs were divided into three groups: sham, CB control, and CB rIPC. CB rIPC fetuses had a hindlimb tourniquet applied to occlude blood flow for four cycles of a 5-min period, followed by a 2-min reperfusion period. Both study groups underwent 30 min of normothermic CB. Fetal inflammatory markers, gas exchange, and placental and fetal lung morphological changes were assessed.

The CB rIPC group achieved higher bypass flow rates (p < .001). After CB start, both study groups developed significant decreases in PaO₂ , mixed acidosis, and increased lactate levels (p < .0004). No significant differences in tissular edema were observed on fetal lungs and placenta (p > .391). Expression of Toll-like receptor 4 and intercellular adhesion molecule-1 in the placenta and fetal lungs did not differ among the three groups, as well as with vascular cell adhesion molecule-1 (VCAM-1) of fetal lungs (p > .225). Placental VCAM-1 expression was lower in the rIPC group (p < .05). Fetal interleukin-1 (IL-1) and thromboxane A2 (TXA2) levels were lower at 60 min post-CB in the CB rIPC group (p < .05). There were no significant differences in tumor necrosis factor-α, prostaglandin E2, IL-6, and IL-10 plasma levels of the three groups at 60-min post-bypass (p > .133).

Although rIPC allowed increased blood flow during fetal CB and decreased IL-1 and TXA2 levels and placental VCAM-1, it did not prevent placental dysfunction in fetal lambs undergoing CB.