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Ann Thorac Surg 2007;84:917-925
© 2007 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Role of Nitric Oxide Pathway in Placental Dysfunction Following Fetal Bypass

^a Division of Cardiothoracic Surgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio
^b Department of Obstetrics and Gynecology, University of Cincinnati, Cincinnati, Ohio

Accepted for publication April 16, 2007.

^_* Address correspondence to Dr Eghtesady, Division of Cardiothoracic Surgery, Cincinnati Children’s Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3039 (Email: pirooz.eghtesady{at}cchmc.org).

Presented at the Forty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 29–31, 2007.

Background: The etiology of placental dysfunction after fetal cardiopulmonary bypass remains unknown. The placental nitric oxide (NO) pathway has been implicated in this pathophysiology. We set out to examine possible perturbations in this pathway in an ovine model of fetal bypass.

Methods: Ovine fetuses (n = 14) between 100 and 114 days of gestation, instrumented to measure hemodynamics and umbilical blood flow, were placed on bypass for 30 minutes and followed after bypass for 2 hours. Sham controls (n = 6) were instrumented but did not undergo bypass. Real-time, in-vivo NO concentrations were measured in the placental circulation. To examine other components of the NO pathway, fetal plasma samples were analyzed by immunoassays for total NO metabolite and cyclic guanosine 3',5'–cyclic monophosphate (cGMP) levels. In addition, the expression of phosphodiesterase-5 was examined in placenta by immunohistochemistry. Statistical analysis was performed using analysis of variance with least significant difference post hoc tests (p 0.05).

Results: With the onset of bypass, an immediate increase occurs in umbilical NO concentrations. These return to baseline with cessation of bypass, and decline thereafter. In contrast, there was a linear increase in fetal plasma cGMP levels and a decline in NO metabolite concentrations through the post-bypass period. There was a dramatic increase in placental phosphodiesterase-5 expression with 30 minutes of bypass. The changes occur simultaneously with decreasing umbilical flows, increased placental vascular resistance, and worsening placental gas exchange.

Conclusions: Fetal bypass leads to significant reductions in placental NO concentrations despite increases in fetal plasma cGMP and placental phosphodiesterase-5 levels, indicative of perturbations in the fetal-placental NO pathway.

This article has been cited by other articles:

				C. T. Lam, S. Sharma, R. S. Baker, J. Hilshorst, J. Lombardi, K. E. Clark, and P. Eghtesady Fetal stress response to fetal cardiac surgery. Ann. Thorac. Surg., May 1, 2008; 85(5): 1719 - 1727. [Abstract] [Full Text] [PDF]