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ARTIGO ORIGINAL

Tolerância da placenta à parada circulatória umbilical normotérmica

Renato S AssadI; Fan-Yen LeeII; Joseph SabikI; Saralyn MackenzieII; Frank L HanleyII

DOI: 10.1590/S0102-76381992000300001

RESUMO

O aumento da resistência vascular placentáriae distúrbios de trocas gasosas freqüentemente ocorrem após a circulação extracorpórea (CEC) fetal. A utilização de um circuito convencional de CEC que exclua a placenta da circulação através do clampeamento temporário do cordão umbilical pode proteger a vasculatura placentária dos estímulos que levam ao aumento da resistência vascular. Para avaliar a tolerância placentária à parada normotérmica do fluxo sangüíneo umbílico-placentário, 9 placentas de ovelhas isoladas in-situ, foram colocadas em CEC através da canulação dos vasos umbilicais, com fluxo médio de artéria umbilical de 214 ml/min/kg. Após 30 minutos de estabelecimento da CEC, a circulação placentária foi interrompida por 30 minutos, simulando o clapeamento do cordão umbilical durante a CEC fetal total. Posteriormente, a circulação placentária foi restabelecida aos valores basais. A troca de gases placentária, o fluxo sangüíneo e a resistência vascular materno-placentários foram avaliados antes e depois da parada circulatória. Não houve diferença estatisticamente significante entre os gradientes transplacentários de pO2 e pCO2, indicando que a interrupção do fluxo sangüíneo placentário por 30 minutos, em condições normotérmicas, não afeta a função placentária. Este modelo sugere um método alternativo para a aplicação clínica da CEC fetal, através da exclusão da circulação umbílico-placentária durante a CEC fetal, eliminandose, assim, os efeitos deletérios da CEC nas trocas gasosas placentárias.

ABSTRACT

Elevation of placental vascular resistance (PVR) and depression of fetal gas exchange occurs after fetal cardiopulmonary bypass (CPB). Excluding the placenta from the CPB circuit may protect the placental vasculature from the unwanted stimuli which lead to elevated PVR. To evaluate this approach, 9 isolated in-situ sheep placentas were placed on CPB by cannulating the umbilical vessels, with a mean umbilical artery flow of 214 ml/min/kg. After 30 minutes of stable flow, placental circulation was arrested for 30 minutes, simulating the umbilical vessel clamp time during whole body fetal CPB. Placental circulation was then restored to baseline values. Placental gas exchange and maternal placental blood flow were evaluated before and after arrest. Interruption of blood flow to the placenta for 30 minutes under normothermic conditions does not affect placental function or maternal placental blood flow. It may be possible to exclude the placenta from the circulation during fetal CPB as a mean of eliminating the detrimental effects of CPB on placental gas exchange. This model suggests an alternative way of designing a scheme for clinical fetal CPB which may avoid the negatives effects of CPB on the placenta.
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REFERÊNCIAS

1. ADDONIZIO, V. P.; SMITH, J. B.; STRAUSS, J. F.; COLMAN, R. W.; EDMUNDS, L. H. - Thromboxane synthesis and platelet secretion during cardiopulmonary bypass with bubble oxygenator. J. Thorac. Cardiovasc. Surg., 79: 91-96, 1980. [MedLine]

2. ASSALI, N. S.; BRINKMAN, C. R.; NUWAYHID, B. - Comparison of maternal and fetal cardiovascular functions in acute and chronic experiments in the sheep. Am. J. Obstet. Gynecol., 120: 411-425, 1974.

3. BERMAN, W.; GOODLIN, R. C.; HEYMANN, M. A.; RUDOLPH, A. M. - Effects of pharmacologic agents on umbilical blood flow in fetal lambs in utero. Biol. Neonate, 33: 225-235, 1978. [MedLine]

4. BRADLEY, S. M.; HANLEY, F. L.; JENNINGS, R. W.; DUNCAN, B. W.; JESTER, J. A.; VERRIER, E. D. - Regional blood flows during cardiopulmonary bypass in fetal lambs: the effect of nitroprusside. Circulation, 82: III-413, 1990 (Resumo).

5. BRADLEY, S. M.; VERRIER, E. D.; DUNCAN, B. W.; LONGAKER, M. T.; TURLEY, K.; HARRISON, M. R.; HANLEY, F. L. - Cardiopulmonary bypass in the fetal lamb: effect of sodium nitroprusside. Circulation, 80 (Supl. 2): II-220, 1989 (Resumo).

6. CHALLSI, J. R. G.; DILLEY, S. R.; ROBINSON, J. S.; THORBURN, G. D. - Prostaglandins in the circulation of the fetal lamb. Prostaglandins, 11: 1041-1052, 1975.

7. CONTRACTOR, S. F.; EATON, B. M.; FIRTH, J. A.; BAUMAN, K. F. - A comparison of the effects of different perfusion regimes on the structure of the isolated human placental lobule. Cell. Tissue Res., 237: 609-617, 1984. [MedLine]

8. FAYMONVILLE, M. E.; DEBY-DUPONT, G.; LARBUISSON, R.; DEBY, C.; BODSON, L; LIMET, R.; LAMY, M. - Prostaglandin E2, prostacyclin, and thromboxane changes during nonpulsatile cardiopulmonary bypass in humans. J. Thorac. Cardiovasc. Surg., 91: 858-866, 1986. [MedLine]

9. FISHMAN, N. H.; HOF, R. B.; RUDOLPH, A. M.; HEYMANN, M. A. - Models of congenital heart disease in fetal lambs. Circulation, 58: 354-364, 1978. [MedLine]

10. GOETZMAN, B. W.; ITSKOVITZ, J.; RUDOLPH, A. M. - Fetal adaptations to spontaneous hypoxemia and responses to maternal oxygen breathing. Biol. Neonate, 46: 276-284, 1984. [MedLine]

11. GREISS, F. C. - Pressure-flow relationships in the gravid uterine vascular bed. Am. J. Obstet. Gynecol., 96: 41-47, 1966. [MedLine]

12. HARRISON, M. R. & ADZICK, N. S. - The fetus as a patient. Ann. Surg., 213: 279-291, 1991. [MedLine]

13. HEARSE, D. J. - Detection and prevention of tissue injury during hypoxia and ischemia. Contr. Gynecol. Obstet., 13: 48-58, 1985.

14. HEYMANN, M. A.; CREASY, R. K.; RUDOLPH, A. M. - Quantitation of blood flow patterns in the foetal lamb in utero. In: COMLINE, K. S.; CROSS, K. W.; DAWES, G. S.; NATHANIELSZ, P. W. Foetal and neonatal physiology. Cambridge, Cambridge University Press, 1973. p. 129-135.

15. HEYMANN, M. A.; PAYNE, B. D.; HOFFMAN, J. I.; RUDOLPH, A. M. - Blood flow measurements with radionuclide-labeled particles. Prog. Cardiovasc. Dis., 20: 55-79, 1977. [MedLine]

16. IWAMOTO, H. S. & RUDOLPH, A. M. - Effects of angiotensin II on the blood flow and its distribution in fetal lambs. Circ. Res., 48: 183-189, 1981. [MedLine]

17. KAUFMANN, P. - Influence of ischemia and artificial perfusion on placental ultrastructure and morphometry. Contr. Gynecol. Obstet., 13: 18-26, 1985.

18. LONGAKER, M. T.; COLBUS, M. S.; FILLY, R. A.; ROSEN, M. A.; CHANG, S. W.; HARRISON, M. R. - Maternal outcome after open fetal surgery: a review of the first 17 human cases. JAMA, 265: 737-741, 1991. [MedLine]

19. NOVY, M. J.; PIASECKI, G.; JACKSON, B. T. - Effect of prostaglandins E2 and F2 on umbilical blood flow and fetal hemodynamics. Prostaglandins, 5: 543-555, 1974. [MedLine]

20. PARISI, V. M.; SALINAS, J.; STOCKMAR, E. J. - Placental vascular responses to nicardipine in the hypertensive ewe. Am. J. Obstet. Gynecol., 161: 1039-1043, 1989. [MedLine]

21. PARISI, V. M. & WALSH, S. W. - Arachidonic acid metabolites and the regulation of placental and other vascular tone during pregnancy. Semin. Perinatol ., 10: 288-298, 1986. [MedLine]

22. PARISI, V. M. & WALSH, S. W. - Fetal placental vascular responses to prostacyclin after angiotensin ll-induced vasoconstriction. Am. J. Physiol., 257: 102-107, 1989.

23. PARISI, V. M. & WALSH, S. W. - Fetal vascular response to prostacyclin. Am. J. Obstet. Gynecol., 160: 871-878, 1989.

24. PARISI, V. M. & WALSH, S. W. - Fetoplacental vascular responses to prostacyclin after thromboxane-induced vasoconstriction. Am. J. Obstet. Gynecol., 160: 502-507, 1989. [MedLine]

25. RANKIN, J. H. G. - Role of prostaglandins in the maintenance of the placental circulation. In: COCEANI, F. & OLLEY, P. M. Advances in prostaglandin and thromboxane research. New York, Raven Press, 1978. p. 221-229.

26. RUDOLPH, A. M. & HEYMANN, M. A. - Hemodynamic changes induced by blockers of prostaglandin synthesis in the fetal lamb in utero. In: COCEANI, F. & OLLEY, P. M. Advances in prostaglandin and thromboxane research. New York, Raven Press, 1978. p. 231-237.

27. SCHWARTZ, D. B.; PHERNETTON, T. M.; STOCK, M. K.; RANKIN, J. H. G. - Placental vascular responses to 6-keto-prostaglandin E1 in the near-term sheep. Am. J. Obstet. Gynecol., 145: 406-410, 1983. [MedLine]

28. TURLEY, K.; VLAHAKES, G. J.; HARRISON, M. R.; MESSINA, L.; HANLEY, F.; UHLIG, P. N.; EBERT, P. A. - Intrauterine cardiothoracic surgery: the fetal lamb model. Ann. Thorac. Surg., 34: 422-426, 1982. [MedLine]

29. WATKINS, W. D.; PETERSON, M. B.; KONG, D. L; KONO, K.; BUCKLEY, M. J.; LEVINE, F. H.; PHILBIN, D. M. - Thromboxane and prostacyclin changes during cardiopulmonary bypass with and without pulsatile flow. J. Thorac. Cardiovasc. Surg., 84: 250-256, 1982. [MedLine]

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