Prolonged pulmonary vascular hyperreactivity in conscious dogs after cardiopulmonary bypass

D. P. Nyhan, J. M. Redmond, A. M. Gillinov, K. Nishiwaki, P. A. Murray

Research output: Contribution to journalArticle


Although cardiopulmonary bypass (CPB) is required in all surgical procedures involving open-heart surgery, the extent to which CPB alters pulmonary vascular regulation has not been systematically investigated. Our objectives were to investigate the acute, subacute, and chronic effects of CPB on the left pulmonary vascular pressure-flow (LP-Q̇) relationship in conscious dogs. Continuous LP-Q̇ plots were generated in chronically instrumented conscious dogs 2-4 days pre-CPB and again 4 h and 1, 2, 7, and 14 days after 2.5 h of closed-chest hypothermic CPB. In addition, pulmonary vascular reactivity was assessed by examining the dose-response relationship to the thromboxane analogue U-46619 pre- and post-CPB. CPB resulted in an acute (4 h post-CPB) shift in the baseline LP-Q̇ relationship, indicating an increase in pulmonary vascular resistance (P < 0.01). The baseline LP-Q̇ relationship returned to pre-CPB values by 1 day post-CPB. Despite this return of the baseline LP-Q̇ relationship to pre-CPB values, the pulmonary vasoconstrictor response to U-46619 was markedly potentiated 2 days post-CPB compared with the pre-CPB response (P < 0.01). This enhanced pulmonary vasoconstrictor response to U-46619 was still apparent 7 days post-CPB (P < 0.01) but was not evident 14 days post-CPB. These results indicate that CPB results in a pronounced, but transient, increase in pulmonary vascular resistance. Moreover, CPB causes a protracted increase in pulmonary vascular reactivity even when the baseline LP-Q̇ relationship has returned to pre- CPB values. This experimental model can be used to assess the specific effects of CPB on acute and chronic mechanisms of pulmonary vascular regulation.

Original languageEnglish (US)
Pages (from-to)1584-1590
Number of pages7
JournalJournal of applied physiology
Issue number4
StatePublished - 1994


  • U-46619
  • chronic instrumentation
  • pressure-flow plots
  • pulmonary circulation
  • pulmonary vasoconstriction

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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