Monitoring the systemic circulation

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Optimizing systemic circulation involves the maintenance of optimal cardiac output and tissue perfusion without unfavorable effects on coronary blood flow or the critical balance between myocardial oxygen supply and demand.1

Direct measurement of arterial pressure2

A well-reproduced signal can yield valuable information relevant to the status of systemic circulation. Systolic, diastolic, and mean arterial pressures are important determinants of flow and tissue perfusion. Rate of rise of pressure in the arterial pressure wave form is an indirect indicator of myocardial contractility. The position of dicrotic wave takeoff could provide information relevant to the volemic status of the patient. Hypovolemia is often associated with low takeoff of dicrotic wave.

Fidelity of reproduction of arterial pressure signal is important for appropriate interpretation of the significance of the measurement. The most important factors affecting the quality of the signal are catheters used for cannulation, conducting systems of extension tubing and stopcocks, and the disposable diaphragm domes. With a reasonable conducting system, a frequency response of 6 to 20 Hz is adequate for reasonable reproduction of a signal. Resonance and overshoot are due to underdamping of the signal and can result in inaccuracies. Several measures are used to diminish underdamping although none are totally dependable.

Myocardial oxygen consumption

Heart rate and systolic pressure significantly correlate with myocardial oxygen consumption. Rate-systolic pressure product shows more significant correlation with myocardial oxygen consumption in awake and anesthetized patients.3 ST-segment changes especially in lead V-5 could be useful indicators of myocardial oxygen consumption.4

Tissue perfusion

Clinical indicators of . . .



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