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Systemic arterial pressure wave reflections during acute hemorrhage.
Paul Dark1, Rod Little, Mahesh Nirmalan
1Faculty of Medical and Human Sciences, University of Manchester, UK.
Critical Care Medicine
|March 17, 2006
Summary
Hemorrhage alters aortic pressure wave reflections, increasing systolic pressure augmentation. This may worsen cardiac afterload and reduce coronary perfusion, with changes in reflection sites potentially indicating these effects.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Vascular Mechanics
Background:
- Systolic pressure augmentation in the aorta is influenced by wave reflections.
- Hemorrhage significantly impacts cardiovascular dynamics and systemic vascular resistance.
Purpose of the Study:
- To investigate the effect of hemorrhage on wave-reflection-induced systolic pressure augmentation in the aorta.
- To identify changes in pressure wave reflection sites following hemorrhage.
Main Methods:
- A randomized, controlled laboratory experiment was conducted using anesthetized pigs.
- Hemorrhage was induced, followed by observation or reinfusion, with high-fidelity pressure waveforms recorded from the aorta to the femoral artery.
Main Results:
- Hemorrhage decreased augmentation index values, particularly in the distal aorta, and shifted reflection sites from one to two locations.
- Reinfusion restored augmentation index values and reflection sites to baseline levels.
- Systemic vascular resistance did not significantly change despite hemorrhage.
Conclusions:
- Hemorrhage causes early pressure wave reflection from abdominal vasculature, increasing aortic systolic pressure augmentation.
- This augmentation can worsen left ventricular afterload and decrease cardiac performance.
- Systolic pressure augmentation may be a better indicator of left ventricular afterload than systemic vascular resistance.