PubMed · 2005470
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M L Nusynowitz. 1991. Geometric methods for determining left ventricular volume.. https://pubmed.ncbi.nlm.nih.gov/2005470/
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Severe sepsis is characterized by increased oxygen demand, alteration of oxygen extraction, and a diminution of myocardial contractility. The importance of each of these three factors is directly related to the severity of the sepsis. The combination of these factors may lead to tissue hypoxia, which is the shortest route to development of multiple organ failure (MOF). The presence of tissue hypoxia should be suspected in the presence of lactic acidosis. The phenomenon of dependence on oxygen consumption (VO2) in relation to oxygen transport (DO2) is detectable where there is a rise in DO2 induced by perfusion of liquids or administration of vasoactive agents. Study of the relationship between cardiac flow and oxygen extraction is a simple means of studying the relations between VO2 and DO2 at the patient's bedside.
The influence of ventricular interdependence on cardiovascular function has been convincingly demonstrated. In the intact cardiovascular system ventricular interdependence is always present, and thus measures of cardiac function include the contribution of ventricular interdependence (VI). A cardiovascular system model is presented and used to discuss how VI affects selected indices of left ventricular (LV) systolic function. Indices of LV function studied were the ejection fraction, stroke work, peak time derivative of ventricular pressure (dP/dT) and the LV end-systolic pressure-volume relationship. The effects of right ventricular (RV) volume through systolic VI on these indices are conveniently studied by comparing the model responses to pulmonary artery (PA) and vena caval (VC) occlusions; both PA and VC occlusion reduce LV volume, but the RV volume is increased by PA but reduced by VC occlusions. Through systolic VI the increase in RV volume with PA occlusion shifted the LV end-systolic pressure-volume relationship to the left and thus affected measures of LV maximum elastance. The LV ejection fraction, peak dP/dT and stroke work were all augmented by the increase in RV volume associated with the PA occlusion. Experimental studies comparing the responses to PA and VC occlusions are in broad agreement with the results described here. Systolic VI also shifted the cardiac function curve, a global measure of cardiac function, to the left. The results thus suggest that commonly used indices of LV systolic function are dependent on RV function and do not solely reflect LV function.
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