Paired Cardiac Output Measurements Research Articles

The Edwards Acumen IQ system using peripheral arterial catheter-based waveforms to estimate cardiac output is not accurate as compared to thermodilution in dogs.

To assess the agreement between cardiac output (CO) estimated via evaluation of the arterial pressure waveform by a novel monitoring system (Edwards Acumen IQ sensor and HemoSphere Advanced Monitor Platform [HS-IQ]; Edwards LifeSciences) and measured by thermodilution (TD) in anesthetized, normovolemic, and hypovolemic dogs. To assess the agreement between the HS-IQ CO measurements in the radial artery and dorsal metatarsal artery. 8 purpose-bred Beagles. Dogs were placed under general anesthesia. CO was measured via TD and via the HS-IQ at radial and dorsal metatarsal arterial catheters. CO measurements were obtained at 4 time points including normovolemic and multiple hypovolemic states. Paired measurements of CO were evaluated via the method of Bland and Altman with acceptable limits of agreement (LOA) defined as < 30%. A total of 24 (dorsal metatarsal) and 21 (radial) paired measurements were collected in 8 dogs. The overall bias (CI) for comparison of TD to radial arterial HS-IQ CO measurements was -0.09 L/min. LOA and proportional LOA were -2.66 to 2.49 L/min and -140.72% to 104.94%. The overall bias (CI) for comparison of TD to dorsal metatarsal arterial HS-IQ CO measurements was -0.26 L/min. LOA and proportional LOA were -2.76 to 2.24 L/min and -135.96% to 93.25%. The overall proportional error for radial arterial was -17.9% and for dorsal metatarsal was -21.4%. CO measurements with the HS-IQ were easy to obtain but did not produce results within a clinically acceptable range for either measurement site, with a very wide LOA. The CO estimations from the HS-IQ are not appropriate for clinical use at this time.

Changes in transcranial near-infrared spectroscopy values reflect changes in cardiac index during cardiac surgery.

To determine whether changes in transcranial near-infrared spectroscopy (NIRS) values reflect changes in cardiac index (CI) in adult cardiac surgical patients. Single-center prospective post hoc analysis. University hospital. One hundred and twenty-four adult patients undergoing cardiac surgery. In each patient, several CI measurements were taken, and NIRS values were collected simultaneously. We used a hierarchical linear regression model to assess the association between NIRS values and CI. We calculated a crude model with NIRS as the only factor included, and an adjusted model, where mean arterial pressure, end-tidal CO2 , and oxygen saturation were used as confounding factors. A total of 1301 pairs of NIRS and CI values were collected. The analysis of separate NIRS and CI pairs revealed a poor association, which was not statistically significant when adjusted with the chosen confounders. However, when the changes in NIRS from baseline or from the previous measurement were compared to those of CI, a clinically and statistically significant association between NIRS and CI was observed also in the adjusted model. Compared to the baseline and to the previous measurement, respectively, the regression coefficients with 95% confidence intervals were 0.048 (0.041-0.056) and 0.064 (0.055-0.073) in off-pump coronary artery bypass patients and 0.022 (0.016-0.029) and 0.026 (0.020-0.033) in patients who underwent cardiopulmonary bypass. In an unselected cardiac surgical population, the changes in NIRS values reflect those in CI, especially in off-pump coronary artery bypass patients. In this single-center post hoc analysis of data from a prospectively collected database of cardiac surgery patients, paired measurements of cardiac output and NIRS revealed that while there was a no correlation between individual paired measurements, a small correlation was found in changes in the two measurements from baseline values. This highlights a potential to utilize changes in NIRS from baseline to suggest changes in cardiac output in cardiac surgical populations.

Validation of cardiac output estimation using the fourth-generation FloTrac/EV1000™ system in patients undergoing robotic-assisted off-pump coronary artery bypass surgery.

The pulmonary artery catheter (PAC)-despite its invasiveness-remains the gold standard for cardiac output (CO) monitoring. The FloTrac system, a less invasive hemodynamic monitor has been developed, which estimates CO using arterial pressure waveform analysis without external calibration. Recently, an upgraded version of FloTrac system with improved algorithm to follow changes in vascular resistance was introduced into the market. The aim of this study was to assess the reliability of the CO estimated from the fourth-generation FloTrac/EV1000 system (COFT) compared to that measured with PAC using the thermodilution method (COPAC) during robotic-assisted off-pump coronary artery bypass (OPCAB) surgery. COFT and COPAC were obtained simultaneously at 4 predefined time points during robotic-assisted OPCAB: 5min after the induction of general anesthesia (T1), after starting one-lung ventilation (T2), after capnothorax (T3), and after mini-thoracotomy was performed (T4). The agreement of data was investigated by Bland-Altman analysis. Thirty-four patients were initially enrolled. After exclusion, 32 patients and a total of 128 paired CO measurements were obtained. The overall bias was 1.46L/min, the 95% limits of agreements were - 3.40 to 6.33L/min, and the percentage error was 72.98%. Regression analysis of the systemic vascular resistance index (SVRI) and the bias between COPAC and COFT showed that the bias was moderately correlated with the SVRI (r2 = 0.43; p < 0.0001). Despite a software upgrade, the reliability of the fourth-generation FloTrac/EV1000™ system during robotic-assisted OPCAB to estimate CO was not acceptable, especially in patients with low SVRI.

Hemodynamic Monitoring by Smartphone-Preliminary Report from a Comparative Prospective Observational Study.

Background: Advanced hemodynamic monitoring supports making therapeutic decisions in critically ill patients. New technologies, including mobile health, have been introduced into the hemodynamic monitoring armamentarium. However, each monitoring method has potential limitations—content, technical and organizational. The aim of this study was to assess the comparability between measurements obtained with two arterial pressure cardiac output methods: Capstesia™ smartphone hemodynamic software (CS) and LiDCO Rapid™ uncalibrated hemodynamic monitor (LR). Methods: The initial analysis included 16 patients in the period 06–09 2020 without limitations that could make the results obtained unreliable. Eighty pairs of cardiac output measurements were obtained. The comparability of cardiac output results obtained with both methods was assessed using the Spearman’s rank correlation coefficient (R), the intra-class correlation (CCC) and the Bland–Altman curves analysis (B-A). Results: The median (IQR) cardiac output measured with CS and LR were 4.6 (3.9–5.7) and 5.5 (4.6–7.4) L min−1, respectively. In the B-A analysis, CS cardiac output values were on average 1.2 (95% CI −2.1–4.4) L min-1 lower than LR values. The correlation between cardiac output with CS and LR was moderate (r = 0.5; p = 0.04). After adjusting for the presence of the dicrotic notch on the pulse waveform, in the group of eight patients with a visible dicrotic notch, the CS and LR results differed by only 0.1 (95% CI −0.8–1.1) L min−1, the correlation between CS and LR was close to complete (r = 0.96; p < 0.001), and the percentage error was 40%, with a CCC-CS of 0.98 (95% CI 0.95–0.99). Conclusions: The CapstesiaTM smartphone software can provide an alternative method of cardiac output assessment in patients meeting arterial pressure cardiac output evaluation criteria with a clearly discernible dicrotic notch on the arterial pulse pressure waveform. It is necessary to confirm the obtained observations on a larger group of patients; however, it may potentially make objective hemodynamic measurements ubiquitous in patients with invasive arterial pressure monitoring with a clearly discernible dicrotic notch.

Lithium dilution cardiac output measurements in isoflurane-anaesthetised goats: Jugular versus cephalic lithium chloride administration

The administration of lithium chloride (LiCl) for cardiac output (CO) measurement via a peripheral instead of a central vein has been described previously as a valid alternative route in pigs and dogs. The aim of the study was to compare CO measurements after administration of LiCl using two peripheral veins, cephalic or jugular, in goats. Ten adult, female, experimental goats undergoing bilateral stifle arthrotomy were recruited for the study. Paired CO measurements were taken two minutes apart during stable conditions in isoflurane-anaesthetised goats. Forty-two paired CO measurements were taken in total, and the median (range) of paired CO measurement per goat were 4.5 (3–6). The mean (SD) CO using the cephalic and jugular vein for injection of LiCl was 5.28 (1.29) L min−1 and 5.20 (1.24) L min−1 respectively. The Bland-Altman analysis showed an acceptable agreement with a mean bias of 1.33% with limits of agreement (LoA) of −18.43 to 21.09%. The percentage of error was 25%. The four-quadrant plot analysis showed a poor agreement (71%) between the two routes. The polar plot showed a poor trending ability. An 86% inclusion rate (18/21 points) was reached with a ± 35° radial sector size. The findings revealed that the agreement between the two routes is not as precise as the authors expected, however the results are comparable with studies published previously.

Comparing Doppler Echocardiography and Thermodilution for Cardiac Output Measurements in a Contemporary Cohort of Comatose Cardiac Arrest Patients Undergoing Targeted Temperature Management.

Measuring cardiac output is used to guide treatment during postresuscitation care. The aim of this study was to compare Doppler echocardiography (Doppler-CO) with thermodilution using pulmonary artery catheters (PAC-CO) for cardiac output estimation in a large cohort of comatose out-of-hospital cardiac arrest (OHCA) patients undergoing targeted temperature management (TTM). Single-center substudy of 141 patients included in the TTM trial randomly assigned to 33 or 36°C for 24 hours after OHCA. Per protocol, PAC-CO and Doppler-CO were measured simultaneously shortly after admission and again at 24 and 48 hours. Linear correlation was assessed between methods and positive predictive value (PPV) and negative predictive value (NPV) of Doppler to estimate low cardiac output (<3.5 L/min) was calculated. A total of 301 paired cardiac output measurements were available. Average cardiac output was 5.28 ± 1.94 L/min measured by thermodilution and 4.06 ± 1.49 L/min measured by Doppler with a mean bias of 1.22 L/min (limits of agreements -1.92 to 4.36 L/min). Correlation between methods was moderate (R2 = 0.36). Using PAC-CO as the gold standard, PPV of a low cardiac output measurement (<3.5 L/min) by Doppler was 33%. However, the NPV was 92%. Hypothermia at 33°C did not negatively affect the correlations of CO methods. In the lowest quartile of Doppler, 13% had elevated lactate (>2 mmol/L). In the lowest quartile of thermodilution, 36% had elevated lactate (>2 mmol/L). In ventilated OHCA patients, the two methods for estimating cardiac output correlated moderately and there was a consistent underestimation of Doppler-CO. Absolute cardiac output values from Doppler-CO should be interpreted with caution. However, Doppler can be used to exclude low cardiac output with high accuracy. TTM at 33°C did not negatively affect the correlation or bias of cardiac output measurements. ClinicalTrials.gov ID: NCT01020916.

A performance comparison of the most commonly used minimally invasive monitors of cardiac output.

Shock is common in critically ill and injured patients. Survival during shock is highly dependent on rapid restoration of tissue oxygenation with therapeutic goals based on cardiac output (CO) optimization. Despite the clinical availability of numerous minimally invasive monitors of CO, limited supporting performance data are available. Following approval of the University of Saskatchewan Animal Research Ethics Board, we assessed the performance and trending ability of PiCCOplus™, FloTrac™, and CardioQ-ODM™ across a range of CO states in pigs. In addition, we assessed the ability of invasive mean arterial blood pressure (iMAP) to follow changes in CO using a periaortic transit-time flow probe as the reference method. Statistical analysis was performed with function-fail, bias and precision, percent error, and linear regression at all flow, low-flow (> 1 standard deviation [SD] below the mean), and high-flow (> 1 SD above the mean) CO conditions. We made a total of 116,957 paired CO measurements. The non-invasive CO monitors often failed to provide a CO value (CardioQ-ODM: 40.6% failed measurements; 99% confidence interval [CI], 38.5 to 42.6; FloTrac: 9.6% failed measurements; 99% CI, 8.7 to 10.5; PiCCOplus: 4.7% failed measurements; 99% CI, 4.5 to 4.9; all comparisons, P < 0.001). The invasive mean arterial pressure provided zero failures, failingless often than any of the tested CO monitors (all comparisons, P < 0.001). The PiCCOplus was most interchangeable with the flow probe at all flow states: PiCCOplus (20% error; 99% CI, 19 to 22), CardioQ-ODM (25% error; 99% CI, 23 to 27), FloTrac (34% error; 99% CI, 32 to 38) (all comparisons, P < 0.001). At low-flow states, CardioQ-ODM (43% error; 99% CI, 32 to 63) and Flotrac (45% error; 99% CI, 33 to 70) had similar interchangeability (P = 0.07), both superior to PiCCOplus (48% error; 99% CI, 42 to 60) (P < 0.001). Regarding CO trending, the CardioQ-ODM (correlation coefficient, 0.82; 99% CI, 0.81 to 0.83) was statistically superior to other monitors including iMAP, but at low flows iMAP (correlation coefficient, 0.58; 99% CI, 0.58 to 0.60) was superior to all minimally invasive CO monitors (all comparisons P < 0.001). None of the minimally invasive monitors of CO performed well at all tested flows. Invasive mean arterial blood pressure most closely tracked CO change at critical flow states.

Cardiac output estimation using multi-beat analysis of the radial arterial blood pressure waveform: a method comparison study in patients having off-pump coronary artery bypass surgery using intermittent pulmonary artery thermodilution as the reference method

Pulse wave analysis enables stroke volume to be estimated from an arterial blood pressure waveform. Multi-beat analysis is a novel pulse wave analysis method. We aimed to investigate cardiac output (CO) estimations using multi-beat analysis of the radial arterial blood pressure waveform in patients undergoing off-pump coronary artery bypass surgery (OPCAB) using intermittent pulmonary artery thermodilution (PATD) as the reference method. This was a prospective clinical method comparison study. In 58 patients, we measured CO using PATD (PATD-CO; reference method) and simultaneously recorded the radial arterial blood pressure waveform that we used for off-line estimation of CO based on multi-beat analysis (MBA-CO; test method) using the Argos CO monitor (Retia Medical; Valhalla, NY, USA). The final analysis was performed using 572 paired CO measurements. We performed Bland–Altman analysis accounting for multiple observations per patient. To describe the ability of the test method to track changes in CO over time we computed four-quadrant plots using a central exclusion zone of 15% and calculated the concordance rate. Mean PATD-CO was 4.13 ± 1.26 L/min and mean MBA-CO was 4.31 ± 1.25 L/min. The mean of the differences between PATD-CO and MBA-CO was − 0.20 L/min with a standard deviation of ± 1.14 L/min and 95% limits of agreement of − 2.48 to + 2.08 L/min. The concordance rate for CO changes between PATD-CO and MBA-CO was 89%. CO estimations using multi-beat analysis (Argos monitor) show reasonable agreement and trending ability compared with PATD-CO as the reference method in adult patients during OPCAB.

Disagreement in cardiac output measurements between fourth-generation FloTrac and critical care ultrasonography in patients with circulatory shock: a prospective observational study

BackgroundCardiac output measurements may inform diagnosis and provide guidance of therapeutic interventions in patients with hemodynamic instability. The FloTrac™ algorithm uses uncalibrated arterial pressure waveform analysis to estimate cardiac output. Recently, a new version of the algorithm has been developed. The aim was to assess the agreement between FloTrac™ and routinely performed cardiac output measurements obtained by critical care ultrasonography in patients with circulatory shock.MethodsA prospective observational study was performed in a tertiary hospital from June 2016 to January 2017. Adult critically ill patients with circulatory shock were eligible for inclusion. Cardiac output was measured simultaneously using FloTrac™ with a fourth-generation algorithm (COAP) and critical care ultrasonography (COCCUS). The strength of linear correlation of both methods was determined by the Pearson coefficient. Bland-Altman plot and four-quadrant plot were used to track agreement and trending ability.ResultEighty-nine paired cardiac output measurements were performed in 17 patients during their first 24 h of admittance. COAP and COCCUS had strong positive linear correlation (r2 = 0.60, p < 0.001). Bias of COAP and COCCUS was 0.2 L min−1 (95% CI − 0.2 to 0.6) with limits of agreement of − 3.6 L min−1 (95% CI − 4.3 to − 2.9) to 4.0 L min−1 (95% CI 3.3 to 4.7). The percentage error was 65.6% (95% CI 53.2 to 77.3). Concordance rate was 64.4%.ConclusionsIn critically ill patients with circulatory shock, there was disagreement and clinically unacceptable trending ability between values of cardiac output obtained by uncalibrated arterial pressure waveform analysis and critical care ultrasonography.Trial registrationClinicaltrials.gov, NCT02912624, registered on September 23, 2016

Reliability of three-dimensional color flow Doppler and two-dimensional pulse wave Doppler transthoracic echocardiography for estimating cardiac output after cardiac surgery

BackgroundThree-dimensional color flow Doppler (3DCF) is a new convenient technique for cardiac output (CO) measurement. However, to date, no one has evaluated the accuracy of 3DCF echocardiography for CO measurement after cardiac surgery. Therefore, this single-center, prospective study was designed to evaluate the reliability of three-dimensional color flow and two-dimensional pulse wave Doppler (2D-PWD) transthoracic echocardiography for estimating cardiac output after cardiac surgery.MethodsPost-cardiac surgical patients with a good acoustic window and a low dose or no dose of vasoactive drugs (norepinephrine < 0.05 μg/kg/min) were enrolled for CO estimation. Three different methods (third generation FloTrac/Vigileo™ [FT/V] system as the reference method, 3DCF, and 2D-PWD) were used to estimate CO before and after interventions (baseline, after volume expansion, and after a dobutamine test).ResultsA total of 20 patients were enrolled in this study, and 59 pairs of CO measurements were collected (one pair was not included because of increasing drainage after the dobutamine test). Pearson’s coefficients were 0.260 between the CO-FT/V and CO-PWD measurements and 0.729 between the CO-FT/V and CO-3DCF measurements. Bland-Altman analysis showed the bias between the absolute values of CO-FT/V and CO-PWD measurements was − 0.6 L/min with limits of agreement between − 3.3 L/min and 2.2 L/min, with a percentage error (PE) of 61.3%. The bias between CO-FT/V and CO-3DCF was − 0.14 L/min with limits of agreement between − 1.42 L /min and 1.14 L/min, with a PE of 29.9%. Four-quadrant plot analysis showed the concordance rate between ΔCO-PWD and ΔCO-3FT/V was 93.3%.ConclusionsIn a comparison with the FT/V system, 3DCF transthoracic echocardiography could accurately estimate CO in post-cardiac surgical patients, and the two methods could be considered interchangeable. Although 2D-PWD echocardiography was not as accurate as the 3D technique, its ability to track directional changes was reliable.

A preliminary study evaluating cardiac output measurement using Pressure Recording Analytical Method (PRAM) in anaesthetized dogs

BackgroundHaemodynamic variations normally occur in anaesthetized animals, in relation to the animal status, administered drugs, sympathetic and parasympathetic tone, fluid therapy and surgical stimulus. The possibility to measure some cardiovascular parameters, such as cardiac output (CO), during anaesthesia would be beneficial for both the anaesthesia management and its outcome. New techniques for the monitoring of CO are aimed at finding methods which are non invasive, accurate and with good trending ability, which can be used in a clinical setting. The aim of this study was to compare the Pressure Recording Analytical Method (PRAM) with the pulmonary artery thermodilution (TD) for the measurement of cardiac output in 6 anaesthetized critically ill dogs.ResultsFifty-four pairs of CO measurements were obtained with a median (range) of 3.33 L/min (0.81–7.21) for PRAM-CO and 3.48 L/min (1.41–6.56) for TD-CO. The Bland-Altman analysis showed a mean bias of 0.17 L/min with limits of agreement (LoA) of − 0.46 to 0.81 L/min. The percentage error resulted 18.2%. The 4-quadrant plot analysis showed an acceptable concordance (93%) between the 2 methods. The polar plot showed a good trending ability with the mean angular bias of 3.9° and radial LoA ± 12.1°.ConclusionsThe PRAM resulted in good precision, acceptable concordance and good trending ability for the measure of CO in the anaesthetized dog, representing a promising alternative to thermodilution for the measurement of CO. Among all the pulse contour methods available on the market it is the only one that does not require any calibration or adjustment of the measurement. Further studies are required to verify the ability of this method to accurately measure cardiac output even during unstable hemodynamic conditions.

Accuracy of impedance cardiography for evaluating trends in cardiac output: a comparison with oesophageal Doppler

Impedance cardiography (ICG) enables continuous, beat-by-beat, non-invasive, operator-independent, and inexpensive cardiac output (CO) monitoring. We compared CO values and variations obtained by ICG (Niccomo™, Medis) and oesophageal Doppler monitoring (ODM) (CardioQ™, Deltex Medical) in surgical patients. This prospective, observational, single-centre study included 32 subjects undergoing surgery with general anaesthesia. CO was measured simultaneously with ICG and ODM before and after events likely to modify CO (vasopressor administration and volume expansion). One hundred and twenty pairs of CO measurements and 94 pairs of CO variation measurements were recorded. The CO variations measured by ICG correlated with those measured by ODM [r=0.88 (0.82-0.94), P<0.001]. Trending ability was good for a four-quadrant plot analysis with exclusion of the central zone (<10%) [95% confidence interval (CI) for concordance (0.86; 1.00)]. Moderate to good trending ability was observed with a polar plot analysis (angular bias: -7.2°; 95% CI -12.3°; -2.5°; with radial limits of agreement -38°; 24°). After excluding subjects with chronic obstructive pulmonary disease, a Bland-Altman plot showed a mean bias of 0.47 litre min(-1), limits of agreements between -1.24 and 2.11 litre min(-1), and a percentage error of 35%. ICG appears to be a reliable method for the non-invasive monitoring of CO in patients undergoing general surgery.

Non-invasive cardiac output assessment in critically ill paediatric patients

Objective Recently, non-invasive methods for cardiac output (CO) assessment have been developed including the ultrasonic cardiac output monitor (USCOM). This technique uses the same concept as Doppler echocardiography but differs in two aspects including continuous wave (CW) Doppler and estimated outflow tract diameter (OTD) used in USCOM compared to pulsed wave Doppler and directed measurement of OTD used in echocardiography. We sought to assess the agreement between CO assessment by USCOM and echocardiography in critically ill paediatric patients.Methods Paired measurements of CO in critically ill paediatric patients were simultaneously and independently obtained by USCOM and echocardiography. Agreement between OTD, velocity time integral (VTI), CO, and cardiac index (CI) were assessed by percentage error and Bland-Altman analysis.Results Thirty-four children (aged 7.86 ± 5.78 years, 44.1% male) had a mean OTD (1.47 ± 0.38, 1.41 ± 0.40), VTI (19.13 ± 6.06, 23.53 ± 7.31 cm), CO (3.88 ± 2.19, 4.41 ± 2.83 l/min) and CI (4.23 ± 1.19, 4.77 ± 1.43 l/min/m2) by echocardiography and USCOM, respectively. Bias ± precision and percentage of error of OTD, VTI, CO, and CI were -0.07 ± 0.20 cm, 27.80%; -4.40 ± 3.84 cm, 31.99%; –0.53 ± 1.23 l/min, 54.66%; and 0.54 ± 1.03 l/min/m2, 42.32%, respectively. The bias ± precision and percentage error were more important in patients with septic shock (n = 16).Conclusion USCOM was an unreliable tool for absolute value measurement of CO and CI due to the errors of VTI by CW Doppler.

Thermodilution vs pressure recording analytical method in hemodynamic stabilized patients

PurposeMany mini-invasive devices to monitor cardiac output (CO) have been introduced and, among them, the pressure recording analytical method (PRAM). The aim of this study was to assess the agreement of PRAM with the intermittent transpulmonary thermodilution and continuous pulmonary thermodilution in measuring CO in hemodynamically stabilized patients. Materials and MethodsThis is a prospective clinical study in a mixed medical-surgical intensive care unit (ICU) and in a postcardiac surgical ICU. Forty-eight patients were enrolled: 32 patients to the medical-surgical ICU monitored with PiCCO (Pulsion Medical System AG, Munich, Germany) and 16 were cardiac patients monitored with Vigilance (Edwards Lifesciences, Irvine, CA). ResultsA total of 112 measurements were made. Ninety-six comparisons of paired CO measurements were made in patients hospitalized in medical-surgical ICU; 16, in cardiac surgical patients.The mean Vigilance-CO was 4.49 ± 0.99 L/min (range, 2.80-5.90 L/min), and the mean PRAM-CO was 4.27 ± 0.88 L/min (range, 2.85-6.19 L/min). The correlation coefficient between Vigilance-CO and PRAM-CO was 0.83 (95% confidence interval, 0.57-0.94; P < .001). The bias was 0.22 ± 0.55 L/min with limits of agreement between 0.87 and 1.30 L/min. The percentage error was 25%.Mean TP-CO was 6.78 ± 2.04 L/min (range, 4.12-11.27 L/min), and the mean PRAM-CO was 6.11 ± 2.18 L/min (range, 2.82-10.90 L/min). The correlation coefficient between PiCCO-CO and PRAM-CO was 0.91 (95% confidence interval, 0.83-0.96; P < .0001). The bias was 0.67 ± 0.89 L/min with limits of agreement −1.07 and 2.41 L/min. The coefficient of variation for PiCCO was 4% ± 2%, and the coefficient of variation for PRAM was 10% ± 8%. The percentage error was 28%. ConclusionsThe PRAM system showed good agreement with pulmonary artery catheter and PiCCO in hemodynamically stabilized patients.

Influence of lung injury on cardiac output measurement using transpulmonary ultrasound dilution: a validation study in neonatal lambs

Transpulmonary ultrasound dilution (TPUD) is a promising method for cardiac output (CO) measurement in severely ill neonates. The incidence of lung injury in this population is high, which might influence CO measurement using TPUD because of altered lung perfusion. We evaluated the influence of lung injury on the accuracy and precision of CO measurement using TPUD in an animal model. In nine neonatal lambs, central venous and arterial catheters were inserted and connected to the TPUD monitor. Repeated lavages with warmed isotonic saline were performed to gradually induce lung injury. CO measurements with TPUD (COtpud) were compared with those obtained by an ultrasonic transit-time flow probe around the main pulmonary artery (COufp). An increase in oxygenation index was used as an indicator of induced lung injury during the experiment. Post-mortem lung injury was confirmed by histopathological examination. Fifty-five sessions of three paired CO measurements were analysed. The mean COufp was 1.53 litre min(-1) (range 0.66-2.35 litre min(-1)), and the mean COtpud was 1.65 litre min(-1) (range 0.78-2.91 litre min(-1)). The mean bias (standard deviation) between the two methods was 0.13 (0.15) litre min(-1) with limits of agreement of ±0.29 litre min(-1). The overall percentage error was 19.1%. The accuracy and precision did not change significantly during progressive lung injury. Histopathological severity scores were consistent with heterogeneous lung injury. The capability to track changes in CO using TPUD was moderate to good. The accuracy and precision of CO measurement using TPUD is not influenced in the presence of heterogeneous lung injury in an animal model.

Cardiac output measurement with transpulmonary ultrasound dilution is feasible in the presence of a left-to-right shunt: a validation study in lambs

Cardiac output (CO) monitoring remains complex in newborns as most of the current technologies fail to accurately measure systemic blood flow in the presence of shunts. We validated CO measurements using transpulmonary ultrasound dilution (TPUD) in a neonatal lamb model with a left-to-right shunt. Regular arterial and central venous catheters were inserted into seven lambs (3.5-8.3 kg). A surgically constructed left-to-right aorto-pulmonary Gore-Tex(®) shunt was intermittently opened and closed, while CO was manipulated by creating haemorrhagic hypotension. CO measurements with TPUD (COtpud) were compared with those obtained by an ultrasonic transit-time flow probe positioned around the main pulmonary artery (COufp). We performed 72 sessions of three paired CO measurements. The mean COufp was 1.00 litre min(-1) (range 0.47-1.75 litre min(-1)) and mean COtpud 1.05 litre min(-1) (range 0.54-1.87 litre min(-1)). With an open shunt, the mean Qp/Qs ratio was 1.8 (range 1.3-2.6). A comparison between COufp and COtpud showed a mean bias (sd) of 0.03 (0.09) and 0.07 (0.10) litre min(-1), respectively, for measurements with a closed and an open shunt. The percentage error was 18% and 20% for measurements with a closed and an open shunt. Polar plot analysis showed good trending ability for both closed and open shunt groups. TPUD is a reliable technology to measure CO in the presence of a left-to-right shunt.

The Impact of Phenylephrine, Ephedrine, and Increased Preload on Third-Generation Vigileo-FloTrac and Esophageal Doppler Cardiac Output Measurements

Cardiac output (CO) monitoring based on pulse contour analysis (Vigileo-FloTrac) has the potential to be used for goal-directed fluid therapy in the perioperative setting. However, factors such as vasopressor usage may impact Vigileo-FloTrac's reliability in tracking CO changes. We tested third-generation Vigileo-FloTrac system's ability to accurately measure the changes in CO induced by vasopressor administration and increased preload in comparison with esophageal Doppler measurements. In 33 anesthetized patients, CO was monitored simultaneously by the third-generation Vigileo-FloTrac and esophageal Doppler. Hemodynamic challenges included phenylephrine (to increase vasomotor tone), ephedrine (to increase myocardial contractility and heart rate), and whole-body tilting (to increase preload). Measurements were performed before and after each intervention. Overall, 176 pairs of CO measurements were obtained. The difference between paired pulse contour and Doppler measurements of CO was 0.14 ± 2.13 L/min (mean ± SD), and the percentage error (2 SD of the difference divided by the mean CO of the reference method) was 66%. The trending ability of pulse contour versus Doppler was 23% (concordance, the percentage of the total number of data points that are in 1 of the 2 quadrants of agreement) after phenylephrine treatment, 69% (concordance) after ephedrine treatment, and 96% (concordance) after whole-body tilting. The pulse contour method of measuring CO, as implemented in the third-generation Vigileo-FloTrac device, accurately tracks changes in CO when preload changes. However, the pulse contour method does not accurately track changes in CO induced with phenylephrine and ephedrine.

Lack of agreement between pulmonary arterial thermodilution cardiac output and the pressure recording analytical method in postoperative cardiac surgery patients

Pulse-contour analysis method (PCM) cardiac output (CO) monitors are increasingly used for CO monitoring during anaesthesia and in the critically ill. Very recently, several systems have been introduced that do not need calibration; among them the pressure recording analytical method (PRAM). Sparse data comparing the accuracy of the PRAM-CO with conventional thermodilution CO (ThD-CO) in cardiac surgery patients are available. In this prospective comparison study, paired CO measurements with a pulmonary artery catheter and a PRAM monitoring set were obtained 20-30 min apart (t1, t2) in 23 extubated patients on the first postoperative day after cardiac surgery. Data were analysed by the Bland-Altman method. A total of 46 paired CO measurements (23 for each interval) were collected. The Bland-Altman analysis showed a mean difference (bias) of 0.0 litre min(-1) and limits of agreement (1.96 sd) of 4.53 to -4.54 litre min(-1) [upper 95% confidence interval (CI), 3.26-5.80; lower 95% CI, -5.8 to -3.27]. The percentage error (1.96 sd/mean of the reference method) was 87%. These results question the reliability of the PRAM technology for the determination of CO in postoperative cardiac surgery patients.

Cardiac output derived from arterial pressure waveform analysis without calibration vs. thermodilution in septic shock: evolving accuracy of software versions

We studied the evolution of software in the accuracy of the FloTrac/Vigileo system to measure cardiac output less invasively from arterial pressure waveform analysis without calibration, in comparison with pulmonary artery catheter-derived thermodilution measurements, in patients with septic shock and presumed alterations in vascular tone. Nine patients who received a pulmonary artery catheter and were on mechanical ventilation and in sinus rhythm were monitored by the FloTrac/Vigileo. Paired cardiac output measurements by both techniques were analysed for 86 measurements in four patients using the 1.07 software version and 73 measurements in five subsequent patients using the later 1.10 version. For the 1.07 version, bias was -1.6 L min, precision 1.6 L min, limits of agreement -4.8-1.5 L min and error 48%. Measurements correlated at partial r equal to 0.32 (P = 0.003). For the 1.10 version, bias was -1.2 L min, precision 1.1 L min, limits of agreement -3.5-1.0 L min and error 32%. Measurements correlated at partial r equal to 0.90 (P < 0.001 vs. version 1.07). Differences were inversely related to mean cardiac output (P < 0.001, generalized estimating equations), particularly for software version 1.07 vs. 1.10 (P = 0.017, generalized estimating equation). Changes in thermodilution cardiac output over the course of time were also better tracked by the FloTrac/Vigileo when applying the latest software (P < 0.001, generalized estimating equation). Evolving software versions are thus better able to account for the effect of vascular tone on cardiac output measurements by less invasive waveform analyses without calibration (FloTrac/Vigileo), so that the latter may become useful in the haemodynamic monitoring of septic shock.

Monitoring in resuscitation: Comparison of cardiac output measurement between pulmonary artery catheter and NICO

Aim The cardiac output and coronary perfusion pressure generated from chest compressions during resuscitation manoeuvres can predict effectiveness and successful outcome. Until now, there is no good method for haemodynamic monitoring during resuscitation. Noninvasive partial carbon dioxide rebreathing system (NICO, Novametrix Medical Systems, Inc., Wallingford, CT, USA) is a relatively new non-invasive alternative to thermodilution for measuring cardiac output. The accuracy of the NICO system has not been evaluated during resuscitation. The aim of this study is to compare thermodilution cardiac output method with NICO system and to assess the utility of NICO during resuscitation. Methods and design Experimental study in 24 Yorkshire pigs. Paired measurements of cardiac output were determined during resuscitation (before ventricular fibrillation and after 5, 15, 30 and 45 min of resuscitation) in the supine position. The average of 3 consecutive thermodilution cardiac output measurements (10 ml 20 °C saline) was compared with the corresponding NICO measurement. Results Bland and Altman plot and Lin's concordance coefficient showed a high correlation between NICO and thermodilution cardiac output measurements although NICO has a tendency to underestimate cardiac output when compared to thermodilution at normal values of cardiac output. Conclusions There is a high degree of agreement between cardiac output measurements obtained with NICO and thermodilution cardiac output during resuscitation. The present study suggests that the NICO system may be useful to measure cardiac output generated during cardiopulmonary resuscitation.