Abstract
Combination vasodilator and cardiotonic therapy may help infants with pulmonary vasospasm and low cardiac output. To test the relative effectiveness of α-blockers with different receptor actions, we instrumented newborn lambs with catheters to measure pressure in the pulmonary artery (PAP), aorta (SAP) and left atrium (LAP). The ductus arteriosus was tied and a flow transducer placed around the main PA. After recovery, all lambs were studied in room air on two successive days. Dopamine dose response to 2.7, 27 and 270 ug/kg/min was measured then repeated with Phe (1 mg/kg, n=5), Pz (1 mg/kg, n=6), or T (5 mg/kg/hr, n=13). Dopamine raised SAP, PAP, LAP, systemic vascular resistance (SVR), and heart rate (HR)(p<.05) at medium and high doses. Pulmonary vascular resistance (PVR) rose at the top dose (p<.01) while QP didn't change and PVR/SVR fell (p<.01). Only Phe changed basal values, lowering SAP (75±2 to 67±3, p<.05), and raising HR (208±20, to 256±28, p<.01). All drugs blocked dopamine-induced SAP and SVR rise and allowed increased QP, HR and PVR/SVR relative to dopamine alone (p<.05). Pz and T blunted the dopamine-induced PAP increase, which Phe did not; PVR was lower when T was coupled with dopamine (p<.025). With Pz and Phe, PVR, was the same as doparaine alone. Thus, all three drugs prevented dopamine interaction with systemic α-receptors, all increased HR and cardiac output when coupled with dopamine. None completely blocked dopamine's pulmonary circulatory effect although T blunted it. Thus, all α-blockers can facilitate the cardiotonic effect of high dose dopamine, but none completely ablates its pulmonary vasoconstrictor effect. T may be more advantageous in this regard, perhaps because of its non-adrenergic effects
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Drummond, W., Williams, B., Shrager, H. et al. 96 INFLUENCE OF α-BLOCKING DRUGS PRAZOSIN (Pz), PHENTOLAMINE (Phe), AND TOLAZOLINE (T) ON CARDIOPULMONARY RESPONSE TO DOPAMINE IN AWAKE LAMBS. Pediatr Res 19, 126 (1985). https://doi.org/10.1203/00006450-198504000-00126
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DOI: https://doi.org/10.1203/00006450-198504000-00126