Cardiac Output by Thermodilution and Arterial Pulse Contour Techniques

A Simple Physiologic Algorithm for Managing Hemodynamics Using Stroke Volume and Stroke Volume Variation: Physiologic Optimization Program

Intravascular volume status and volume responsiveness continue to be important questions for the management of critically ill or injured patients. Goal-directed hemodynamic therapy has been shown to be of benefit to patients with severe sepsis and septic shock, acute lung injury and adult respiratory distress syndrome, and for surgical patients in the operating room. Static measures of fluid status, central venous pressure (CVP), and pulmonary artery occlusion pressure (PAOP) are not useful in predicting volume responsiveness. Stroke volume variation and pulse pressure variation related to changes in stroke volume during positive pressure ventilation predict fluid responsiveness and represent an evolving practice for volume management in the intensive care unit (ICU) or operating room. Adoption of dynamic parameters for volume management has been inconsistent. This manuscript reviews some of the basic physiology regarding the use of stroke volume variation to predict fluid responsiveness in the ICU and operating room. A management algorithm using this physiology is proposed for the critically ill or injured in various settings.

An evaluation of cardiac output by five arterial pulse contour techniques during cardiac surgery

The bias, precision and tracking ability of five different pulse contour methods were evaluated by simultaneous comparison of cardiac output values from the conventional thermodilution technique (COtd). The five different pulse contour methods included in this study were: Wesseling's method (cZ); the Modelflow method; the LiDCO system; the PiCCO system and a recently developed Hemac method. We studied 24 cardiac surgery patients undergoing uncomplicated coronary artery bypass grafting. In each patient, the first series of COtd was used to calibrate the five pulse contour methods. In all, 199 series of measurements were accepted by all methods and included in the study. COtd ranged from 2.14 to 7.55 l.min(-1), with a mean of 4.81 l.min(-1). Bland-Altman analysis showed the following bias and limits of agreement: cZ, 0.23 and - 0.80 to 1.26 l.min(-1); Modelflow, 0.00 and - 0.74 to 0.74 l.min(-1); LiDCO, - 0.17 and - 1.55 to 1.20 l.min(-1); PiCCO, 0.14 and - 1.60 to 1.89 l.min(-1); and Hemac, 0.06 and - 0.81 to 0.93 l.min(-1). Changes in cardiac output larger than 0.5 l.min(-1) (10%) were correctly followed by the Modelflow and the Hemac method in 96% of cases. In this group of subjects, without congestive heart failure, with normal heart rhythm and reasonable peripheral circulation, the best results in absolute values as well as in tracking changes in cardiac output were measured using the Modelflow and Hemac pulse contour methods, based on non-linear three-element Windkessel models.

Monitoring cardiac output using the femoral and radial arterial pressure waveform

This study was performed to determine the interchangeability of femoral artery pressure and radial artery pressure measurements as the input for the PiCCO system (Pulsion Medical Systems, Munich, Germany). We studied 15 intensive care patients following cardiac surgery. Five-second averages of the cardiac output derived from the femoral artery pressure (COfem) were compared to 5-s averages derived from the radial artery pressure (COrad). One patient was excluded due to problems in the pattern recognition of the arterial pressure signal. In the remaining 14 patients, 14 734 comparative cardiac output values were analysed. The mean sample time was 88 min, range [30-119 min]. Mean (SD) COfem was 6.24 (1.1) l.min(-1) and mean COrad 6.23 (1.1) l.min(-1). Bland-Altman analysis showed an excellent agreement with a bias of - 0.01 l.min(-1), and limits of agreement from 0.60 to - 0.62 l.min(-1). If changes in CO were > 0.5 l.min(-1), the direction of changes in COfem and COrad were equal in 97% of instances. We conclude that femoral artery pressure and radial artery pressure are interchangeable as inputs for the PiCCO device.

Arterial pressure-based technologies: a new trend in cardiac output monitoring

New trends in cardiovascular monitoring use the arterial pulse as a less invasive means of assessing cardiac output. When adopting a new technology into practice, three questions need to be answered: (1) is the method technologically sound?, (2) is it based on physiologic principles?, and (3) are the applications clinically important? This article provides a clinical review on the technology, physiology, and applications of a new arterial pressure-based method of determining cardiac output and stroke volume variation as an additional parameter for fluid status assessment.