Cardiac Output Assessed by Invasive and Minimally Invasive Techniques

Abstract

Cardiac output (CO) measurement has long been considered essential to the assessment and guidance of therapeutic decisions in critically ill patients and for patients undergoing certain high-risk surgeries. Despite controversies, complications and inherent errors in measurement, pulmonary artery catheter (PAC) continuous and intermittent bolus techniques of CO measurement continue to be the gold standard. Newer techniques provide less invasive alternatives; however, currently available monitors are unable to provide central circulation pressures or true mixed venous saturations. Esophageal Doppler and pulse contour monitors can predict fluid responsiveness and have been shown to decrease postoperative morbidity. Many minimally invasive techniques continue to suffer from decreased accuracy and reliability under periods of hemodynamic instability, and so few have reached the level of interchangeability with the PAC.

Focused rapid echocardiographic evaluation versus vascular cather-based assessment of cardiac output and function in critically ill trauma patients

“…These catheters intermittently sample the CO and display the average value over 5 minutes to 15 minutes. They may miss episodes of change but provide a reasonable "global" CO. 6 By echo, the SV estimate can be falsely high if the LVOT area is overestimated or falsely low if the blood flow is not in-line with the transducer.…”

“…Proprietary software estimates vessel compliance using patient demographic data and then integrates complex arterial wave form analysis using 11 different data points to determine the SV and from that the CI. 6 The accuracy of the V/FT system relative to PACs in vasodilated states including sepsis and liver failure has been questioned in several studies. 15,16 The manufacturer has released its thirdgeneration software to address this issue, which appears to correlate better with PACs in sepsis.…”

“…Patients for whom CI was simultaneously recorded from both FREE and from either a PAC or an a-line with the FloTrac Vigileo (FT/V) (Edwards Lifesciences, LLC, Irvine CA) system were identified. The FT/V system uses the pulse contour analysis of the a-line to estimate the CI 6,7 and is the most common mode of assessing CO within our institution's SICUs. In addition, to assess normal CI as a measure of cardiac function, the percentage of patients with moderate (EF 30 -40%) or severe systolic dysfunction (EF Ͻ30%) and a below normal CI (Յ2.5) was determined.…”

“…The CCO PAC uses an electrical filament in the right ventricular portion of the catheter and a heat sensor at its tip to thermo-dilute the blood and intermittently calculate a CO which is then divided by the patient's BSA to determine the CI. 6 Alternatively, a peripheral a-line is attached to the FloTrac sensor and Vigileo monitor (software version 3.2, Edwards Lifesciences). The sensor collects and analyzes the arterial wave form for several characteristics and determines a SV from which CO and CI are calculated, as is described in detail elsewhere.…”

Oesophageal Doppler guided optimization of cardiac output does not increase visceral microvascular blood flow in healthy volunteers

“…Thermodilution, however, remains the gold standard for the assessment of SV 57 against which new monitors are compared [6].…”