Pulmonary Artery Catheter (PAC) Accuracy and Efficacy Compared with Flow Probe and Transcutaneous Doppler (USCOM): An Ovine Cardiac Output Validation

School of Medicine, The University of Queensland, Brisbane QLD 3010, Australia.
Critical care research and practice 05/2012; 2012(9):621496. DOI: 10.1155/2012/621496
Source: PubMed


Background. The pulmonary artery catheter (PAC) is an accepted clinical method of measuring cardiac output (CO) despite no prior validation. The ultrasonic cardiac output monitor (USCOM) is a noninvasive alternative to PAC using Doppler ultrasound (CW). We compared PAC and USCOM CO measurements against a gold standard, the aortic flow probe (FP), in sheep at varying outputs. Methods. Ten conscious sheep, with implanted FPs, had measurements of CO by FP, USCOM, and PAC, at rest and during intervention with inotropes and vasopressors. Results. CO measurements by FP, PAC, and USCOM were 4.0 ± 1.2 L/min, 4.8 ± 1.5 L/min, and 4.0 ± 1.4 L/min, respectively, (n = 280, range 1.9 L/min to 11.7 L/min). Percentage bias and precision between FP and PAC, and FP and USCOM was -17 and 47%, and 1 and 36%, respectively. PAC under-measured Dobutamine-induced CO changes by 20% (relative 66%) compared with FP, while USCOM measures varied from FP by 3% (relative 10%). PAC reliably detected -30% but not +40% CO changes, as measured by receiver operating characteristic area under the curve (AUC), while USCOM reliably detected ±5% changes in CO (AUC > 0.70). Conclusions. PAC demonstrated poor accuracy and sensitivity as a measure of CO. USCOM provided equivalent measurements to FP across a sixfold range of outputs, reliably detecting ±5% changes.

Download full-text


Available from: Rob A Phillips
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: In managing patients with unstable hemodynamics, monitoring cardiac output (CO) can provide critical diagnostic data. However, conventional CO measurements are invasive, intermittent, and/or inaccurate. The purpose of this study was to validate our newly developed CO monitoring system. Methods: This system automatically determines peak velocity of the ascending aortic flow using continuous-wave Doppler transthoracic echocardiography and estimates cardiac ejection time and aortic cross-sectional area using the pulse contour of the radial arterial pressure. These parameters are continuously processed to estimate CO (CO(est)). In 10 anesthetized closed-chest dogs instrumented with an aortic flowprobe to measure reference CO (CO(ref)), hemodynamic conditions were varied over wide ranges by infusing cardiovascular drugs or by random atrial pacing. Under each condition, CO(ref) and CO(est) were determined. Absolute changes of CO(ref) (ΔCOref) and CO(est) (ΔCO(est)), and relative changes of CO(ref) (%ΔCO(ref)) and CO(est) (%ΔCO(est)) from the corresponding baseline values were determined in each animal. We calibrated CO(est) against CO(ref) to obtain proportionally scaled CO(est) (CO(est)(N)). Results: A total of 1335 datasets of CO(ref) and CO(est) were obtained, in which CO(ref) ranged from 0.17 to 5.34 L/min. Bland-Altman analysis between CO(ref) and CO(est) indicated that the limits of agreement (the bias ± 1.96 × SD of the difference) and the percentage error (1.96 × [SD of the difference]/[mean CO] × 100) were from -1.01 to 1.13 L/min (95% confidence interval, -1.76 to 1.88 L/min) and 43%, respectively. The agreement between CO(ref) and CO(est)(N) was improved, with limits of agreement from -0.53 to 0.49 L/min (95% confidence interval, -0.62 to 0.59 L/min) and the percentage error of 20%. Polar plot analysis between ΔCO(ref) and ΔCO(est) indicated that mean ± 1.96 × SD of polar angle was -2° ± 22°. Four quadrant plot analysis indicated that %ΔCO(est) correlated tightly with %ΔCO(ref) (R(2) = 0.93). The %ΔCO(est) and %ΔCO(ref) changed in the same direction in 95% of the datasets. Reliability of this system was well preserved under conditions of random atrial pacing and also in a continuous manner. Conclusion: Over a wide range of hemodynamic conditions, irrespective of cardiac beat irregularity, this system may allow minimally invasive monitoring of CO with a good trending ability. The present results warrant further research and development of this system for future clinical application.
    Full-text · Article · Mar 2013 · Anesthesia and analgesia
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Maintaining threshold values of cardiac output (CO) and systemic vascular resistance (SVR) when used as part of the American College of Critical Care Medicine (ACCM) haemodynamic protocol improves the outcomes in paediatric septic shock. We observed the evolution of CO and SVR during the intensive care admission of children with fluid-refractory septic shock and report this together with the eventual outcomes. Prospective observational study. Tertiary care Paediatric Intensive Care Unit (PICU) in London. Children admitted in fluid refractory septic shock to the Intensive Care Unit over a period of 36 months were studied. Post liver re-transplant children and delayed septic shock admissions were excluded. A non-invasive ultrasound cardiac output monitor device (USCOM) was used to measure serial haemodynamics. Children were allocated at presentation into one of two categories: (1) hospital-acquired infection and (2) community-acquired infection. Vasopressor, inotrope or inodilator therapies were titrated to maintain threshold cardiovascular parameters as per the ACCM guidelines. Thirty-six children [19 male, mean age (SD) 6.78 (5.86) years] were admitted with fluid-refractory septic shock and studied. At presentation, all 18 children with hospital-acquired (HA) sepsis and 3 from among the community-acquired (CA) sepsis group were in 'warm shock' (SVRI < 800 dyne s/cm(5)/m(2)) whereas 15 of the 18 children with community-acquired sepsis and none in the hospital-acquired group were in 'cold shock' [cardiac index (CI) < 3.3 l/min/m(2)]. All 21 children in 'warm shock' were initially commenced on a vasopressor (noradrenaline). Despite an initial good response, four patients developed low CI and needed adrenaline. Similarly, all 15 children in cold shock were initially commenced on adrenaline. However, two of them subsequently required noradrenaline. Five others needed milrinone as an inodilator. In general, both groups of children had normalised SVRI and CI within 42 h of therapy but required variable doses of vasopressors, inotropes or inodilators in a heterogeneous manner. The overall 28-day survival rate was 88.9 % in both groups. Central venous oxygen saturation (ScvO2) was significantly (p = 0.003) lower in the community-acquired group (mean 51.72 % ± 4.26) when compared to the hospital-acquired group (mean 58.72 % ± 1.36) at presentation but showed steady improvement during therapy. Gram-positive organisms were predominant in blood cultures, 61 % in HA and 56 % in CA groups. In general, we found children with community-acquired septic shock presented in cold shock whereas hospital-acquired septic shock children manifested warm shock. Both types evolved in a heterogeneous manner needing frequent revision of cardiovascular support therapy. However the 28-day survival in both groups was the same at 89 %. Frequent measurements of haemodynamics using non-invasive ultrasound helped in fine tuning cardiovascular therapies.
    Full-text · Article · Jun 2013 · Intensive Care Medicine
  • [Show abstract] [Hide abstract]
    ABSTRACT: Supra-sternal Doppler (USCOM Ltd., Sydney, Australia) can be used during anaesthesia to measure cardiac output (CO) and related flow parameters. However, before the USCOM can be used routinely, its utility and limitations need to be fully understood and critical information about its use disseminated. In "Window to the Circulation" we use the example of an elderly man undergoing major urological robotic surgery to highlight the utility and limitations of intra-operative USCOM use. USCOM readings were verified against oesophageal Doppler. Despite the lack of major blood loss (<500 ml in 8-h), significant changes in haemodynamics were recorded. CO ranged from 3.2 to 8.3 l/min. The quality of USCOM scans and reliability of data was initially poor, but improved as CO increased as surgery progressed. When USCOM scans became acceptable the correlation with oesophageal Doppler was R(2) = 8.0 (p < 0.001). Several characteristic features of the supra-sternal Doppler scans were identified: Aortic and pulmonary flow waves, valve closure, E and A waves, false A-wave and aberrant arterial flow patterns. Their identification helped with identifying the main flow signal across the aortic valve. The USCOM has the potential to monitor changes in CO and related flow parameters intra-operatively and thus help the anaesthetist to more fully understand the patient's haemodynamics. However, achieving a good quality scan is important as it improves the reliability of USCOM data. The supra-sternal route is rich in flow signals and identifying the aortic valve signal is paramount. Recognizing the other characteristic waveforms in the signal helps greatly.
    No preview · Article · Aug 2013 · International Journal of Clinical Monitoring and Computing
Show more