Ischemic preconditioning does not prevent placental dysfunction induced
by fetal cardiac bypass
Abstract
Background: 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. Methods:
Eighteen fetal lambs were divided into 3 groups: sham, CB control, and
CB rIPC. CB rIPC fetuses had a hindlimb tourniquet applied to occlude
blood flow for 4 cycles of a 5-minute period, followed by a 2-minute
reperfusion period. Both study groups underwent 30 minutes of
normothermic CB. Fetal inflammatory markers, gas exchange, and placental
and fetal lung morphological changes were assessed. Results:
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 on tissular edema were observed on fetal
lungs and placenta (p>.391). Expression of toll-like
receptor-4 and ICAM-1 in the placenta and fetal lungs did not differ
among the 3 groups, as well as with 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 minutes post-CB in the CB rIPC group
(p<.05). There was no significant differences in TNF-α, PGE2,
IL-6 and IL-10 plasma levels of the three groups at 60-minute
post-bypass (p>.133). Conclusion: Although rIPC
allowed for increased blood flow during fetal CB and decreased in IL-1
and TXA2 levels and placental VCAM-1, it did not prevent placental
dysfunction in fetal lambs undergoing CB.