Thermodilution Cardiac Output Measurements Research Articles

Agreement between direct Fick and bolus thermodilution measurements of cardiac output during right heart catheterisation and the impact on haemodynamic classifications

Abstract Background/Introduction When measuring cardiac output (CO) during right heart catheterisation (RHC), both direct Fick (DF) and bolus thermodilution (TD) methods are endorsed by pulmonary hypertension (PH) guidelines (1). Agreement between these techniques in contemporary practice is not well understood, nor are the diagnostic consequences of disagreement. Purpose To investigate the real-world agreement between DF and TD techniques for measuring CO during contemporary RHC, and evaluate the impact of disagreement on patients’ haemodynamic classification. Methods This was a single-centre study including 182 patients who had CO measured simultaneously by DF and TD methods during RHC. Oxygen consumption (VO2) was measured with an indirect calorimeter. The primary outcome was the agreement between DF and TD derived CO using Bland-Altman analysis. Secondary outcomes included the impact of specific clinical variables on CO agreement, and the frequency of disagreement in determining patients’ haemodynamic classification. Results Disagreement between DF and TD measures of CO was noted, with the DF technique tending to overestimate CO relative to the TD measurement (median DF-CO 5.42 L/min [interquartile range (IQR) 3.90 – 7.41] vs median TD-CO 4.10 L/min [IQR 3.47 – 5.10], p<0.001). For CO values between 3-7 L/min, the error between DF and TD measurements ranged from -4.75% to +44.5%, and limits of agreement were between -69.9% and +101% (Figure 1). Disagreement was increased by 19.2% in patients with at least moderate-to-severe tricuspid regurgitation, and by 16.0% in those with irregular heart rhythms (Table1). The agreement between DF and TD derived pulmonary vascular resistance (PVR) was equally poor. Nonetheless, in 86.3% of patients, the techniques agreed in classifying the PVR as abnormally elevated (> 2 Wood Units), with disagreement occurring more frequently in patients with less severe PH. Conclusions In this real-world study there was poor agreement between DF and TD derived CO, resulting in more than 10% of patients having discrepant haemodynamic classifications. This data highlight that both methods should be utilised in clinical practice, particularly in borderline cases or when the haemodynamic assessment influences treatment eligibility or operative risk assessment. The two techniques should not be used interchangeably for serial surveillance, and the impact of our findings on invasive assessments of valvular pathologies needs further investigation.

Is There a Correlation Between Left Ventricular Outflow Tract Velocity Time Integral and Stroke Volume Index in Patients Undergoing Cardiac Surgery?

IntroductionLeft ventricular outflow tract velocity time integral (LVOT VTI) is a promising surrogate for stroke volume (SV). However, there is controversy in the literature regarding its correlation with thermodilution or newer cardiac output measurement techniques. This study was conducted to determine the correlation between LVOT VTI determined by transesophageal echocardiography (TEE) with stroke volume index (SVI) calculated by thermodilution.MethodsConsecutive patients older than 17 years undergoing elective cardiac surgery with pulmonary artery catheter (PAC) and TEE monitoring between September 2021 and February 2022 were included in this prospective, descriptive, single-center study. LVOT VTI was measured using TEE after induction of anesthesia but before skin incision and at least four hours after initial LVOT VTI measurement. SVI was simultaneously measured using the continuous thermodilution technique with a PAC. The correlation between LVOT VTI and SVI was determined with Pearson’s correlation index.ResultsTwelve patients were included and 21 paired measurements were compared. Mean SVI was 31.62 ± 10.71 mL/m2 and mean LVOT VTI was 14.74 ± 4.79 cm. The Pearson's correlation index for the two measurements was r = 0.257, p = 0.262.ConclusionThis prospective study demonstrated a weak correlation between LVOT VTI and SVI in patients undergoing cardiac surgery.

A new noninvasive finger sensor (NICCI system) for cardiac output monitoring: A method comparison study in patients after cardiac surgery.

The new noninvasive finger sensor system NICCI (Getinge; Gothenburg, Sweden) allows continuous cardiac output monitoring. We aimed to investigate its cardiac output measurement performance. To investigate the NICCI system's cardiac output measurement performance. Prospective method comparison study. University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Fifty-one patients after cardiac surgery. We performed a method comparison study in 51 patients after cardiac surgery to compare NICCI cardiac output (CO NICCI ) and NICCI cardiac output calibrated to pulmonary artery thermodilution cardiac output measurement (CO NICCI-CAL ) with pulmonary artery thermodilution cardiac output (CO PAT ). As a secondary analysis we also compared CNAP cardiac output (CO CNAP ) and externally calibrated CNAP cardiac output (CO CNAP-CAL ) with CO PAT . We analysed 299 cardiac output measurement pairs. The mean of the differences (95% limits of agreement) between CO NICCI and CO PAT was 0.6 (-1.8 to 3.1) l min -1 with a percentage error of 48%. The mean of the differences between CO NICCI-CAL and CO PAT was -0.4 (-1.9 to 1.1) l min -1 with a percentage error of 29%. The mean of the differences between CO CNAP and CO PAT was 1.0 (-1.8 to 3.8) l min -1 with a percentage error of 53%. The mean of the differences between CO CNAP-CAL and CO PAT was -0.2 (-2.0 to 1.6) l min -1 with a percentage error of 35%. The agreement between CO NICCI and CO PAT is not clinically acceptable. The study was registered in the German Clinical Trial Register (DRKS00023189) after inclusion of the first patient on October 2, 2020.

Gas Phase Diffusion Does Not Limit Lung Volatile Anesthetic Uptake Rate.

Inefficiency of lung gas exchange during general anesthesia is reflected in alveolar (end-tidal) to arterial (end-tidal-arterial) partial pressure gradients for inhaled gases, resulting in an increase in alveolar deadspace. Ventilation-perfusion mismatch is the main contributor to this, but it is unclear what contribution arises from diffusion limitation in the gas phase down the respiratory tree (longitudinal stratification) or at the alveolar-capillary barrier, especially for gases of high molecular weight such as volatile anesthetics. The contribution of longitudinal stratification was examined by comparison of end-tidal-arterial partial pressure gradients for two inhaled gases with similar blood solubility but different molecular weights: desflurane and nitrous oxide, administered together at 2 to 3% and 10 to 15% inspired concentration (FiG), respectively, in 17 anesthetized ventilated patients undergoing cardiac surgery before cardiopulmonary bypass. Simultaneous measurements were done of tidal gas concentrations, of arterial and mixed venous blood partial pressures by headspace equilibration, and of gas uptake rate calculated using the direct Fick method using thermodilution cardiac output measurement. Adjustment for differences between the two gases in FiG and in lung uptake rate (VG) was made on mass balance principles. A 20% larger end-tidal-arterial partial pressure gradient relative to inspired concentration (PetG - PaG)/FiG for desflurane than for N2O was hypothesized as physiologically significant. Mean (SD) measured (PetG - PaG)/FiG for desflurane was significantly smaller than that for N2O (0.86 [0.37] vs. 1.65 [0.58] mmHg; P < 0.0001), as was alveolar deadspace for desflurane. After adjustment for the different VG of the two gases, the adjusted (PetG - PaG)/FiG for desflurane remained less than the 20% threshold above that for N2O (1.62 [0.61] vs. 1.98 [0.69] mmHg; P = 0.028). No evidence was found in measured end-tidal to arterial partial pressure gradients and alveolar deadspace to support a clinically significant additional diffusion limitation to lung uptake of desflurane relative to nitrous oxide.

A Lumped Parameter Model for Cardiac Output Estimation Using Arterial Blood Pressure Waveform.

This paper investigates a subject-specific lumped parameter cardiovascular model for estimating Cardiac Output (CO) using the radial Arterial Blood Pressure (ABP) waveform. The model integrates a simplified model of the left ventricle along with a linear third order model of the arterial tree and generates reasonably accurate ABP waveforms along with the Dicrotic Notch (DN). Non-linear least square optimization technique is used to obtain uncalibrated estimates of cardiovascular parameters. Thermodilution CO measurements have been used to evaluate the CO estimation accuracy. The model achieves less than 15% normalized error across 10 subjects with different shapes of ABP waveform.

Indirect Fick and Thermodilution Cardiac Output Measurements Have Significant Variance Compared to Direct Fick in LVAD Patients

Purpose Direct Fick is the gold standard for measuring cardiac output (CO). Due to direct Fick complexity, indirect Fick (iFICK) and Thermodilution (TD) are most commonly used to assess CO during right heart catheterization (RHC). However, a small previous study found a 45% discordance in CO estimations when comparing TD with iFick in LVAD patients. This study aimed to compare TD and iFick estimations to direct Fick in order to compare which common method was most accurate. Methods We included 16 LVAD patients referred for clinically indicated RHC. Concomitant with obtaining mixed venous oxygen saturation, resting oxygen consumption was obtained via the MGC diagnostics calorimeter system. Three common formulae were used to calculate iFick for comparison - Lafarge, Dehmer, and Bergstra. Thermodilution was measured in triplicate and averaged with removal of outliers. Correlation between each method and direct Fick was assessed with linear regression. Bias between each method and direct Fick was compared using Bland-Altman Plot analysis. Greater than 25% percent error was used a priori as clinically unacceptable. Results Moderate correlation was present between all methods and direct Fick (TD: R=0.45; Lafarge: R=0.61; Dehmer: R=0.51; Bergstra: R=0.4). However, while absolute bias was lowest between TD and direct Fick (+14.5 ± 30%), all methods tended to overestimate CO compared to direct Fick and had poor overall agreement (Figure). By any method, more than 30% of measurements carried significant discrepancy (>25%) compared to direct Fick. Conclusion Though TD CO carried the least bias, both it and all methods of iFick calculation tend to overestimate CO and have poor agreement when compared to the direct Fick method. These imprecise CO measurements could lead to poor clinical decisions in VAD patients and misjudgment of transplant candidacy due to inaccurate calculation of pulmonary vascular resistance. Where possible, direct Fick should be used to measure CO in LVAD patients.

Thermodilution vs indirect fick cardiac output measurement in clinical practice: insights from a tertiary centre

Abstract Introduction Thermodilution (TD) and indirect Fick (IF) methods are widely used to measure cardiac output (CO). They are often used interchangeably to make critical clinical decisions, yet few studies have compared these approaches concerning agreement and comparative prognostic value as applied in medical practice. Purpose To assess agreement between TD and IF methods and to compare how well these methods predict mortality. Methods Retrospective cohort study including all consecutive right heart catheterizations performed in a referral pulmonary hypertension (PH) centre from 2010 to 2018. Cardiac index (CI) was calculated by indexed CO to body surface area. PH was classified according to the new definition of the 6st World Symposium on Pulmonary Hypertension 2018 [mean pulmonary arterial pressure (mPAP) &amp;gt;20 mmHg]. Patients with cardiac or extra-cardiac shunts or significant (moderate to severe or severe) tricuspid regurgitation were excluded. All-cause mortality over 1 year after right heart catheterization was recorded. Logistic regression was used to identify predictors of the adverse event. Results From a total of 569 procedures, 424 fulfilled the inclusion criteria: mean age 56.7±15.4 years, 67.3% female. Haemodynamic parameters were diagnosed of PH in 86.2% of cases: mPAP 35.3±15.3 mmHg, 83.6% pre-capillary subtype, 42.9% belonging to group 4 (chronic thromboembolic pulmonary hypertension) and 26.6% to group 1 (pulmonary arterial hypertension). Mean values of CO and CI were, respectively, 4.5±2.8 L/min and 2.5±0.8 L/min/m2 measured by TD and 4.6±2.4 L/min and 2.6±1.3 L/min/m2 measured by IF method. There was a median difference (IF minus TD) of - 0.03 / min to CO and - 0.05 L/min/m2 to CI but both meausres correlated only modestly (r=0.6 to TD and r=0.5 to IF). One-year all-cause mortality rate was 5.4% (median time to death was 50.5 days). Lower values of CO and CI assessed by TD were significantly associated with all-cause mortality occurrence (CO TD: 4.5±1.3 L/min versus 3.6±1.0 L/min, p&amp;lt;0.01; CI TD: 2.6±0.7 L/min/m2 versus 2.1±0.4 L/min/m2, p&amp;lt;0.01). No association was observed between CO (p=0.31) and CI (p=0.42) measured by IF method and the adverse event. Logistic regression identified 2 independent predictors of all-cause mortality: TD CO (OR 0.55, 95% CI 0.38–0.79, p&amp;lt;0.01) and TD CI (OR 0.34, 95% CI 0.17–0.67, p&amp;lt;0.01). Similar results were obtained when patients diagnosed with PH were independently analyzed. Conclusions There is only modest agreement between TD and IF CO and CI estimates. Despite being more time-consuming, TD measurements were predictors of all-cause mortality and present a highest prognostic value. These findings favored their used over IF in clinical practice. Funding Acknowledgement Type of funding source: None

Reliability of transcardiopulmonary thermodilution cardiac output measurement in experimental aortic valve insufficiency.

BackgroundMonitoring cardiac output (CO) is important to optimize hemodynamic function in critically ill patients. The prevalence of aortic valve insufficiency (AI) is rising in the aging population. However, reliability of CO monitoring techniques in AI is unknown. The aim of this study was to investigate the impact of AI on accuracy, precision, and trending ability of transcardiopulmonary thermodilution-derived COTCPTD in comparison with pulmonary artery catheter thermodilution COPAC.MethodsSixteen anesthetized domestic pigs were subjected to serial simultaneous measurements of COPAC and COTCPTD. In a novel experimental model, AI was induced by retraction of an expanded Dormia basket in the aortic valve annulus. The Dormia basket was delivered via a Judkins catheter guided by substernal epicardial echocardiography. High (HPC), moderate (MPC) and low cardiac preload conditions (LPC) were induced by fluid unloading (20 ml kg-1 blood withdrawal) and loading (subsequent retransfusion of the shed blood and additional infusion of 20 ml kg-1 hydroxyethyl starch). Within each preload condition CO was measured before and after the onset of AI. For statistical analysis, we used a mixed model analysis of variance, Bland-Altman analysis, the percentage error and concordance analysis.ResultsExperimental AI had a mean regurgitant volume of 33.6 ± 12.0 ml and regurgitant fraction of 42.9 ± 12.6%. The percentage error between COTCPTD and COPAC during competent valve function and after induction of substantial AI was: HPC 17.7% vs. 20.0%, MPC 20.5% vs. 26.1%, LPC 26.5% vs. 28.1% (pooled data: 22.5% vs. 24.1%). The ability to trend CO-changes induced by fluid loading and unloading did not differ between baseline and AI (concordance rate 95.8% during both conditions).ConclusionDespite substantial AI, transcardiopulmonary thermodilution reliably measured CO under various cardiac preload conditions with a good ability to trend CO changes in a porcine model. COTCPTD and COPAC were interchangeable in substantial AI.

Cardiac Output Assessment in Patients Supported with Left Ventricular Assist Device: Discordance Between Thermodilution and Indirect Fick Cardiac Output Measurements.

Cardiac output (CO) assessed by thermodilution (TD) and indirect Fick (iFK) methods is commonly employed in left ventricular assist device (LVAD) patients; however, no study has assessed agreement. This study assesses correlation between these methods and association with hemodynamic/echocardiographic data in LVAD patients. Discordance was defined as a 20% difference between TD and iFK CO measurements. Bias and agreement were determined via the Bland-Altman technique in both the overall sample and iFK-stratified tertiles. Correlation with each assessment of CO and right heart catheterization (RHC) hemodynamics was performed. Among 111 RHCs, the mean CO for TD and iFK were 4.65 ± 1.33 (range: 1.44-9.30) and 5.37 ± 1.51 (range: 3.07-11.80) L/min (p < 0.001), respectively, with a calculated discordance of 45.9%. A correlation coefficient of 0.66 with a bias of -0.72 L/min was found. The lower and upper limit of precision were -3.12 and 1.68 L/min, respectively. By tertile analysis, bias (lower and upper limit of precision) for the low, middle, and high tertile groups were -0.24 (-1.88 and 1.40), -0.48 (-2.50 and 1.53), and -1.39 (-4.18 and 1.39) L/min, respectively. No significant correlation was found between either method with right atrial pressure or pulmonary capillary wedge pressure or any valvular condition. Substantial discrepancies exist between TD and iFK CO in LVAD patients. Although fixed bias was small, the limits of agreement extend into the clinically relevant area, with larger bias being present at higher CO. Studies with flow probes are needed to define which method better represents CO in LVAD patients.

Agreement of Bioreactance Cardiac Output Monitoring With Thermodilution During Hemorrhagic Shock and Resuscitation in Adult Swine.

The study tests the hypothesis that noninvasive cardiac output monitoring based upon bioreactance (Cheetah Medical, Portland, OR) has acceptable agreement with intermittent bolus thermodilution over a wide range of cardiac output in an adult porcine model of hemorrhagic shock and resuscitation. Prospective laboratory animal investigation. Preclinical university laboratory. Eight ~ 50 kg Yorkshire swine with a femoral artery catheter for blood pressure measurement and a pulmonary artery catheter for bolus thermodilution. With the pigs anesthetized and mechanically ventilated, 40 mL/kg of blood was removed yielding marked hypotension and a rise in plasma lactate. After 60 minutes, pigs were resuscitated with shed blood and crystalloid. Noninvasive cardiac output monitoring and intermittent thermodilution cardiac output were simultaneously measured at nine time points spanning baseline, hemorrhage, and resuscitation. Simultaneous noninvasive cardiac output monitoring and thermodilution measurements of cardiac output were compared by Bland-Altman analysis. A plot was constructed using the difference of each paired measurement expressed as a percentage of the mean of the pair plotted against the mean of the pair. Percent bias was used to scale the differences in the measurements for the magnitude of the cardiac output. Method concordance was assessed from a four-quadrant plot with a 15% zone of exclusion. Overall, noninvasive cardiac output monitoring percent bias was 1.47% (95% CI, -2.5 to 5.4) with limits of agreement of upper equal to 33.4% (95% CI, 26.5-40.2) and lower equal to -30.4% (95% CI, -37.3 to -23.6). Trending analysis demonstrated a 97% concordance between noninvasive cardiac output monitoring and thermodilution cardiac output. Over the wide range of cardiac output produced by hemorrhage and resuscitation in large pigs, noninvasive cardiac output monitoring has acceptable agreement with thermodilution cardiac output.

The pilot study of role of electrical cardiometry in non-invasive assessment of hemodynamic parameters in patients with pulmonary arterial hypertension (RCD code: II-1A.1)

Background: Electrical cardiometry (EC) technique could estimate cardiac output (CO), cardiac index (CI) and other parameters related to cardiac contractility and fluid status by measuring the thoracic electrical bioimpedance. We hypothesized that EC could assess right ventricle (RV) hemodynamic function in patients diagnosed with pulmonary arterial hypertension (PAH). Results: In our pilot study, enrolling 23 PAH patients, we observed a significant correlation (r = 0.71; p <0.001) between thermodilution CO measurement results (4.59 ±1.05 l/min) and CO results obtained by EC (4.86 ±1.20 l/min) and between systemic vascular resistance calculated by EC monitor and obtained during right heart catheterization (RHC) (r = 0.68; p = 0.002). Furthermore, EC parameter index of contractility (ICON) sig‑ nificantly correlated with tricuspid annular plane systolic excursion assessed by echocardiography (r = 0.57; p = 0.01). Conclusions: RHC cannot be replaced in obtaining accurate results of CO, however EC technique provides feasible insight into RV function at the bedside or outpatient care. JRCD 2017; 3 (2): 44–49

Agreement between ccNexfin CO-trek cardiac output and intermittent cold-bolus pulmonary thermodilution in a prospective multicenter study.

The ccNexfin System uses the CO-trek algorithm to analyze a non-invasively obtained arterial pressure waveform and calculate cardiac output (NEXCO). It remains matter of debate whether NEXCO can replace invasive, pulmonary artery catheter-derived, cold-bolus pulmonary thermodilution cardiac output measurement (PACCO). This study aimed at testing NEXCO-PACCO agreement in a large sample size, multicenter study. We hypothesized that agreement between NEXCO and PACCO would be demonstrated by a mean accuracy (bias) <0.6 L/min with a percentage error <30%. Patients undergoing cardiac surgery in three academic hospitals clinically requiring pulmonary artery catheterization were included. Exclusion criteria were aortic, pulmonary and tricuspid (valve) abnormalities, non-sinus rhythm and insufficient perfusion of the digits such as in Raynaud's disease. After induction of anesthesia, cardiac output was measured with four cold bolus thermodilution measurements and four averaged 30-second ccNexfin measurements randomized through the respiratory cycle to obtain one measurement pair. Mean accuracy and precision of ccNexfin were expressed as bias (mean of all NEXCO-PACCO differences) and limits of agreement (LOA) (1.96·SD of bias). Percentage error was calculated as [LOA / (NEXCO-PACCO average)]. Fifty-five patients were enrolled in the study, 51 completed the protocol. Median PACCO was 3.7 (IQR: 3.2 to 4.6) L/min and median NEXCO was 3.8 (IQR: 3.1 to 4.7) L/min. NEXCO-PACCO bias was 0.1 (LOA: -1.4 to +1.6) L/min with a 37% percentage error. In this study, cardiac output measurement with ccNexfin failed to meet the predefined criteria for agreement with cold-bolus pulmonary artery thermodilution.

110 - Discordance between Thermodilution and Indirect Fick Cardiac Output Measurements in LVAD Patients

110 - Discordance between Thermodilution and Indirect Fick Cardiac Output Measurements in LVAD Patients

Use of a pressure wire to evaluate right heart pressures in a pre-liver transplant recipient through a peripheral IV.

Use of a pressure wire to evaluate right heart pressures in a pre-liver transplant recipient through a peripheral IV.

Comparison of pulmonary artery and transpulmonary thermodilution cardiac output measurements in unsedated newborn calves

ObjectiveTo compare the agreement, repeatability and trending ability of transpulmonary thermodilution (TPTD) and pulmonary artery thermodilution (PATD) cardiac output ( Q˙t) measurements in unsedated newborn calves. Study designProspective experimental trial. AnimalsEight newborn calves weighing a median (range) of 53 (46–59) kg. MethodsPulmonary and femoral artery thermodilution catheters were placed under local anaesthesia. A total of 382 PATD and TPTD Q˙t measurements were performed simultaneously. Cardiac output was influenced by intravenous doxapram and theophylline in a randomized crossover fashion. Bland–Altman analysis for multiple comparisons, concordance and polar plots were used to assess TPTD against PATD. ResultsMedian (range) cardiac index values measured with PATD and TPTD were 197 mL kg−1 minute−1 (74–335 mL kg−1 minute−1) and 196 mL kg−1 minute−1 (59–395 mL kg−1 minute−1), respec-tively. A small mean bias of -3 mL kg−1 minute−1 with limits of agreement (LOA) of -64 to 58 mL kg−1 minute−1 and a percentage error of 31% were found. Eighty-two mean values were calculated. This reduced the LOA to -50 to 41 mL kg−1 minute−1 with a similar small bias and a percentage error of 23%. Mean TPTD tracked changes in Q˙t compared with mean PATD with 90% concordance, a mean polar angle of 6° and radial LOA of 43°, indicating marginal trending ability. Keeping the femoral artery catheter patent and obtaining acceptable measurements were very challenging because the calves were not used to being restrained. Calf movement had less influence on PATD. Conclusions and clinical relevanceWe recommend that PATD remains the reference method to measure Q˙t in unsedated newborn calves. However, the robust results of the evaluation of the less invasive TPTD technique warrants further evaluation taking into account the difficulties reported in this study.

Synchronizing thermodilution cardiac output measurements with spontaneous breathing does not improve precision.

Measuring cardiac output (CO) with the pulmonary artery catheter intermittent bolus thermodilution technique (PAC-IBTD) is less precise with spontaneous breathing compared to controlled ventilation. We aimed to test if precision could be improved in spontaneous breathing by synchronizing the measurement with respiration or using instructed respiration in 18 post-operative cardiac surgery patients. We performed eight CO measurements with PAC-IBTD using cold saline in three different situations; in random order: 1) random compared to respiration, 2) timed to the start of expiration, and 3) synchronized with a slow exhalation through a PEP-flute. We calculated the standard deviation (SD), coefficient of variation (CV), and precision in the total material and in the three situations using a linear mixed effects model. A total of 408 CO measurements were performed in 17 included patients. There were no differences between the three study situations regarding mean or precision. The overall CO was 6.0 ± 1.4 l/min (mean ± SD), CV 6.2% and precision 12.2% for single measurements. Averaging three measurements increased the precision to 7.0%. We could not improve the precision of PAC-IBTD in spontaneously breathing patients by synchronizing the measurements with respiration.

Importance of re-calibration time on pulse contour analysis agreement with thermodilution measurements of cardiac output: a retrospective analysis of intensive care unit patients.

We assessed the effect of re-calibration time on cardiac output estimation and trending performance in a retrospective analysis of an intensive care unit patient population using error grid analyses. Paired thermodilution and arterial blood pressure waveform measurements (N=2141) from 222 patient records were extracted from the Multiparameter Intelligent Monitoring in Intensive Care II database. Pulse contour analysis was performed by implementing a previously reported algorithm at calibration times of 1, 2, 8 and 24h. Cardiac output estimation agreement was assessed using Bland-Altman and error grid analyses. Trending was assessed by concordance and a 4-Quadrant error grid analysis. Error between pulse contour and thermodilution increased with longer calibration times. Limits of agreement were -1.85 to 1.66 L/min for 1h maximum calibration time compared to -2.70 to 2.41L/min for 24h. Error grid analysis resulted in 74.2% of points bounded by 20% error limits of thermodilution measurements for 1h calibration time compared to 65% for 24h. 4-Quadrant error grid analysis showed <75% of changes in pulse contour estimates to be within ±80% of the change in the thermodilution measurement at any calibration time. Shorter calibration times improved the agreement of cardiac output pulse contour estimates with thermodilution. Use of minimally invasive pulse contour methods in intensive care monitoring could benefit from prospective studies evaluating calibration protocols. The applied pulse contour analysis method and thermodilution showed poor agreement to monitor changes in cardiac output.

Systolic left ventricular function is preserved during therapeutic hypothermia, also during increases in heart rate with impaired diastolic filling.

BackgroundSystolic left ventricular function during therapeutic hypothermia is found both to improve and to decline. We hypothesized that this discrepancy would depend on the heart rate and the variables used to assess systolic function.MethodsIn 16 pigs, cardiac performance was assessed by measurements of invasive pressures and thermodilution cardiac output and with 2D strain echocardiography. Left ventricle (LV) volumes, ejection fraction (EF), transmitral flow, and circumferential and longitudinal systolic strain were measured. Miniaturized ultrasonic transducers were attached to the epicardium of the LV to obtain M-mode images, systolic thickening, and diastolic thinning velocities and to determine LV pressure-wall dimension relationships. Preload recruitable stroke work (PRSW) was calculated. Measurements were performed at 38 and 33°C at spontaneous and paced heart rates, successively increased in steps of 20 up to the toleration limit. Effects of temperature and heart rate were compared in a mixed model analysis.ResultsHypothermia reduced heart rate from 87 ± 10 (SD) to 76 ± 11 beats/min without any changes in LV stroke volume, end-diastolic volume, EF, strain values, or PRSW. Systolic wall thickening velocity (S′) and early diastolic wall thinning velocity decreased by approximately 30%, making systolic duration longer through a prolonged and slow contraction and changing the diastolic filling pattern from predominantly early towards late. Pacing reduced diastolic duration much more during hypo- than during normothermia, and combined with slow myocardial relaxation, incomplete relaxation occurred with all pacing rates. Pacing did not affect S′ or PRSW at physiological heart rates, but stroke volume, end-diastolic volume, and strain were reduced as a consequence of reduced diastolic filling and much more accentuated during hypothermia. At the ultimate tolerable heart rate during hypothermia, S′ decreased, probably as a consequence of myocardial hypoperfusion due to sustained ventricular contraction throughout a very short diastole.ConclusionsSystolic function was maintained at physiological heart rates during therapeutic hypothermia. Reduced tolerance to increases in heart rate was caused by lack of ventricular filling due to diastolic dysfunction and shorter diastolic duration.

The Precision of Pulmonary Artery Catheter Bolus Thermodilution Cardiac Output Measurements Varies With the Clinical Situation.

To investigate the effects of ventilatory mode, injectate temperature, and clinical situation on the precision of cardiac output measurements. Randomized, prospective observational study. Single university hospital. Forty patients undergoing planned cardiac surgery, receiving a pulmonary artery catheter according to institutional routine. Cardiac output was measured at 4 predefined time points during the perioperative patient course, twice during controlled and twice during spontaneous ventilation, using 2 blocks of 8 measurement replications with cold and tepid injectate in random order. The data were analyzed using a hierarchical linear mixed model. Clinical precision was determined as half the width of the 95% confidence interval for the underlying true value. The single-measurement precision measured in 2 different clinical situations for each temperature/ventilation combination was 8% to 10%, 11% to 13%, 13% to 15%, and 23% to 24% in controlled ventilation with cold injectate, controlled ventilation with tepid injectate, spontaneous breathing with cold injectate, and spontaneous breathing with tepid injectate, respectively. Tables are provided for the number of replications needed to achieve a certain precision and for how to identify significant changes in cardiac output. Clinical precision of cardiac output measurements is reduced significantly during spontaneous relative to controlled ventilation. The differences in precision between repeated measurement series within the temperature/ventilation combinations indicate influence of other situation-specific factors not related to ventilatory mode. Compared with tepid injectate in patients breathing spontaneously, the precision is 3-fold better with cold injectate and controlled ventilation.

Trending ability and limitations of transpulmonary thermodilution and pulse contour cardiac output measurement in cats as a model for pediatric patients.

The present study evaluated transpulmonary thermodilution (TPTD) and pulse contour cardiac output (PCCO) both measured by the PiCCO Plus™ monitor (Pulsion Medical Systems, Munich, Germany) against pulmonary artery thermodilution (PATD) in cats as a hemodynamic model for small children. A wide range of cardiac outputs (CO) was simultaneously measured. Accuracy and trending abilities were critically evaluated. Three cats were studied under isoflurane anesthesia and 160 CO measurements were performed with 3 mL ice-cold 5 % dextrose with PATD and TPTD. The results were compared with the PCCO measurement before the bolus measurement. Cardiac output was manipulated from 32 to 224 mL/kg/min by dobutamine, dopamine, phenylephrine, medetomidine and increased concentrations of isoflurane. Bland-Altman analysis, concordance and polar plot analysis were performed to assess accuracy and trending ability. TPTD was measuring constantly higher than PATD with a mean bias of 73 mL/kg/min and limits of agreement of 34-112 mL/kg/min, a concordance rate of 94 % and a mean polar angle of -5° with radial limits of agreement (RLOA) of 33°. Concordance rate of the PCCO versus PATD was 82 % with a mean polar angle of -10° and RLOA of 46° and versus TPTD 90 % with a mean polar angle of -6° and RLOA of 46°. Both tested methods constantly overestimated simultaneous PATD measurements. The small size, low flows and the relative short catheter not reaching the abdominal aorta may explain that. However TPTD tracked changes accurately opposed to a poor trending ability of the PCCO measurement.