Interpreting the Arterial Pressure Waveform in the Intra-aortic Balloon-Pumped Patient

Susan J. Quaal, PhD, APRN, CVS, CCRN, University of Utah Health Sciences Center and Department of Cardiology, VA Salt LakeHealthcare System

Prog Cardiovasc Nurs. 2001;16(3) 

In This Article

What Pressure Reference Point Should Be Used for Titration of Vasopressor and Vasodilator Drips?

Balloon pumping every other heartbeat expands the arterial waveform to five reference points. The effect of vasopressor and vasodilator drugs can no longer be assessed via a simple two-point systolic and diastolic blood pressure. Rather, each reference point must be assessed with regard to the potential effect of various pharmacologic agents. For example, dobutamine primarily exerts a b-adrenergic effect. Therefore, the intended pharmacologic action is inotropic, with an increase in contraction. As the heart empties more efficiently and completely, a greater stroke volume also should be ejected. An increase in stroke volume also should result in an increase in blood volume displaced with IAB inflation and, hence, an increase in peak diastolic augmented pressure.

Dopamine exhibits a-adrenergic effects at infusion rates greater than 10 µg/kg/min, which produces peripheral vasoconstriction. As systemic vascular resistance rises, systolic pressure also may increase. The resultant effect could be that of an increase in both assisted systole and unassisted systole. Assisted systole should, however, remain comparatively lower than patient systole, reflecting the reduction in ventricular work secondary to balloon deflation during isovolumetric contraction.

Mild vasoconstriction improves stroke volume and may increase diastolic augmented pressure. Higher pressor doses will provoke greater vasoconstriction and an increase in systemic vascular resistance. The ventricle now has to work harder, stroke volume is decreased, and diastolic augmentation will also be decreased.

A vasodilator drug such as nitroprusside or nitroglycerin could affect several aspects of arterial pressure. It is possible that both BAEDP and UAEDP may be lowered. Stroke volume decreases with vasodilitation. Lower stroke volume again results in lower diastolic augmented pressure. It is therefore critically important to assess the entire hemodynamic profile when administering vasoactive, vasodilitating, or inotropic drugs to the IAB-pumped patient. Expanding the assessment to include flow parameters such as oxygen delivery and utilization, rather than an isolated pressure point, is perhaps a more accurate outcome measurement. If the nurse receives an order to "titrate dopamine to maintain a pressure of 90," it is crucial to clarify with the provider what that means for the IAB-pumped patient. Deleterious outcomes can arise if one nurse assumes the titration order refers to MAP and another assumes this refers to systole or perhaps peak diastolic augmented pressure.

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