Key result
Systolic pressure variation outperforms CVP and PAOP in predicting cardiac output drop after blood loss.
Why the study?
The utility of systolic pressure variation during a controlled mechanical respiratory cycle as a predictor of the cardiac output response to an acute decrease in ventricular preload needed evaluation.
Does systolic pressure variation predict the cardiac output response to acute blood loss in adults undergoing coronary artery bypass grafting?
Does systolic pressure variation predict the cardiac output response to acute blood loss in adults undergoing coronary artery bypass grafting?
Systolic pressure variation is a superior dynamic measurement compared to central filling pressures for predicting cardiac output response to acute preload reduction.
Answers are grounded in this paper and cite their sources.
May favor SPV over central pressures for preload assessment in CABG; hypothesis-generating, prospective validation required.
STUDY OBJECTIVE To evaluate systolic pressure variation (SPV), defined as the difference between the maximum and minimum systolic blood pressure measured during a controlled mechanical respiratory cycle, as a predictor of the cardiac output (CO) response to an acute decrease in ventricular preload. DESIGN Prospective study with each subject serving as his or her own control. SETTING Cardiac surgery operating rooms of a university medical center. PATIENTS 15 adults with good ventricular function undergoing coronary artery bypass grafting. INTERVENTION During stable anesthetic conditions and before surgical stimulation, 500 ml of blood was removed from each patient over 10 minutes. MEASUREMENTS AND MAIN RESULTS CO, central venous pressure (CVP), pulmonary artery diastolic pressure, and pulmonary artery occlusion pressure (PAOP), and SPV before and after phlebotomy were recorded. Phlebotomy was associated with significant decreases in CVP, PAOP, and CO, and an increase in SPV. Of these variables, SPV was the best predictor of the percent decrease in CO resulting from blood loss. CONCLUSION SPV is a dynamic measurement, which, by revealing the response to small cyclical changes in left ventricular preload that occur during the controlled mechanical respiratory cycle, is a better predictor than central filling pressures of the response of CO to acute decreases in preload that occur as a result of acute blood loss.
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Ornstein et al. (1998) studied Coronary artery bypass grafting (n=15). Systolic pressure variation (SPV) during 500 ml acute phlebotomy vs. Central filling pressures (CVP and PAOP) and pre-phlebotomy baseline was evaluated on Percent decrease in cardiac output resulting from acute blood loss. Systolic pressure variation best predicted the percent decrease in cardiac output after 500 ml blood loss in 15 CABG patients, outperforming CVP and PAOP.
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