Key result
Acute and long-term labetalol reduced blood pressure, peripheral resistance, and heart rate, while long-term oral treatment elevated resting stroke volume to normalize cardiac output.
Why the study?
Does acute and long-term labetalol administration alter cardiovascular dynamics at rest, supine, standing, and during exercise?
Does acute and long-term labetalol administration alter cardiovascular dynamics at rest, supine, standing, and during exercise?
Long-term labetalol therapy effectively reduces blood pressure and peripheral resistance while maintaining cardiac output through a compensatory increase in stroke volume.
May inform labetalol selection for active hypertensives; leaves open randomized confirmation of stroke volume adaptation.
1 After acute intravenous administration labetalol reduced mean values for BP, total peripheral resistance, heart rate and cardiac output. All changes were more pronounced during bicycle exercise. 2 After a mean duration of 20 months' treatment with oral labetalol the haemodynamic findings were broadly similar except for a more marked reduction in the total peripheral resistance and cardiac output had returned to pretreatment level due to an increased stroke volume which had counter balanced the reduction in heart rate. These changes occurred at rest, in the erect position and during exercise but the reductions in BP and peripheral resistance were most marked during exercise. 3 Left ventricular filling pressures and stroke volume/filling pressure ratios were not significantly altered after intravenous labetalol compared with pretreatment values. 4 Systolic BP x heart rate product was lowered particularly during exercise after both intravenous and oral labetalol. 5 After long-term oral labetalol, the most striking haemodynamic change was in the elevated resting stroke volume supine and standing.
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G. Koch (1979) studied this question. Labetalol vs. Pretreatment values was evaluated on Haemodynamic parameters (blood pressure, peripheral resistance, heart rate, cardiac output). Acute and long-term labetalol reduced blood pressure, peripheral resistance, and heart rate, while long-term oral treatment elevated resting stroke volume to normalize cardiac output.
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