| Summary: | Kenneth Warring-Davies1, Martin Bland21The Intensive Care Unit, Bradford Royal Infirmary, Bradford, West Yorkshire, UK; 2Department of Health Sciences, University of York, York, North Yorkshire, UKAbstract: The empirical physiological formulae of the new continuous cardiac dynamic ­monitoring HeartSmart® technology, which involves the use of a new inverse square rule of the heart, were investigated with pulmonary artery catheter (PAC) thermodilution in the ­estimation of CI in diverse patients. Clinical trial data collected from 268 adult surgery or intensive care patients requiring PAC placement were obtained from 7 NHS Trust hospitals, providing 2720 paired sets of CI estimations for comparison between HeartSmart® and PAC thermodilution. For 95% of pairs of measurements, HeartSmart® values were between 57% and 164% of PAC measurements; additionally, the larger limit of agreement between HeartSmart® and PAC thermodilution (1.26 L min-1•m-2) suggests that HeartSmart® agrees with PAC thermodilution as closely as PAC thermodilution agrees with itself. HeartSmart® can also estimate CI in the extreme circumstances of shock/sepsis, as indicated by PAC thermodilution CI values that were hypo- or hyperdynamic based on systemic inflammatory response syndrome criteria. In CI measurements for hypo- or hyperdynamic values that were matched between HeartSmart® and PAC thermodilution, the difference in total volumes and average CI measurements between the two methods was less than 5%. For unmatched hypo- or hyperdynamic values, the difference between total volumes and average CI measurements was less than 33% – an acceptable percentage of difference or error even for normal values of CI. HeartSmart® tracked PAC thermodilution CI hypodynamic values 98.2% of the time and hyperdynamic values 97.6% of the time. These findings show that CI estimations provided by the HeartSmart® empirical physiological formulae are comparable to those obtained using PAC thermodilution. HeartSmart® removes many of the technical barriers that prevent the routine adoption and practice of early goal-directed therapy, and represents a simple, reliable method of estimating CI and other hemodynamic variables at the bedside or in departments other than the Intensive Care Unit.Keywords: cardiac index, early goal-directed therapy, HeartSmart®, cardiodynamics, blood flow
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