Modified Thermodilution for Simultaneous Cardiac Output and Recirculation Assessment in Veno-venous Extracorporeal Membrane Oxygenation: A Prospective Diagnostic Accuracy Study.

BACKGROUND: Thermodilution is unreliable in veno-venous extracorporeal membrane oxygenation (VV-ECMO). Systemic oxygenation depends on recirculation fractions and ratios of extracorporeal membrane oxygenation (ECMO) flow to cardiac output. In a prospective in vitro simulation, this study assessed the diagnostic accuracy of a modified thermodilution technique for recirculation and cardiac output. The hypothesis was that this method provided clinically acceptable precision and accuracy for cardiac output and recirculation. METHODS: Two ECMO circuits ran in parallel: one representing a VV-ECMO and the second representing native heart, lung, and circulation. Both circuits shared the right atrium. Extra limbs for recirculation and pulmonary shunt were added. This study simulated ECMO flows from 1 to 2.5 l/min and cardiac outputs from 2.5 to 3.5 l/min with recirculation fractions (0 to 80%) and pulmonary shunts. Thermistors in both ECMO limbs and the pulmonary artery measured the temperature changes induced by cold bolus injections into the arterial ECMO limb. Recirculation fractions were calculated from the ratio of the areas under the temperature curve (AUCs) in the ECMO limbs and from partitioning of the bolus volume (flow based). With known partitioning of bolus volumes between ECMO and pulmonary artery, cardiac output was calculated. High-precision ultrasonic flow probes served as reference for Bland-Altman plots and linear mixed-effect models. RESULTS: Accuracy and precision for both the recirculation fraction based on AUC (bias, -5.4%; limits of agreement, -18.6 to 7.9%) and flow based (bias, -5.9%; limits of agreement, -18.8 to 7.0%) are clinically acceptable. Calculated cardiac output for all recirculation fractions was accurate but imprecise (RecirculationAUC: bias 0.56 l/min; limits of agreement, -2.27 to 3.4 l/min; and RecirculationFLOW: bias 0.48 l/min; limits of agreement, -2.22 to 3.19 l/min). Recirculation fraction increased bias and decreased precision. CONCLUSIONS: Adapted thermodilution for VV-ECMO allows simultaneous measurement of recirculation fraction and cardiac output and may help optimize patient management with severe respiratory failure.

Thermodilution Assessment of Cardiac Index in Patients With Tricuspid Regurgitation.

BACKGROUND: Disparities between thermodilution (TD) and Fick measurements of cardiac index (CI) are common in real-world clinical practice. Published studies about the effect of tricuspid regurgitation (TR) on TD are small and describe conflicting results. We tested the correlation between TD and Fick across a wide range of TR severity, in a larger group of patients undergoing right heart catheterization (RHC). We aimed to determine if TD is an acceptable alternative to Fick in patients with TR in clinical practice. METHODS: We retrospectively evaluated patients undergoing RHC at a single center over a 10-month period, and included those with recent (<90 days) echocardiograms. TD was measured during RHC and Fick was calculated using estimated oxygen consumption. The primary outcome was the correlation between TD and Fick CIs. We performed regression modeling to evaluate predictors of the difference between TD and Fick. RESULTS: A total of 349 patients were included, 40% of whom had at least moderate TR. The correlation between TD and Fick was strong (r=0.765) and did not significantly differ in those with none to mild TR (r=0.73) and those with moderate to severe TR (r=0.80). Atrial fibrillation or atrial flutter was the only variable significantly associated with the difference between CI by Fick and TD (P=.04). CONCLUSION: The correlation between TD and Fick was strong and unaffected by TR severity.

Cardiac output assessment methods in left ventricular assist device patients: A problem of heteroscedasticity.

Equipoise remains about how best to measure cardiac output (CO) in patients with left ventricular assist devices (LVAD). In this study, direct Fick CO was compared with thermodilution (TD) and indirect Fick (iFick) CO in 61 LVAD patients. TD and LaFarge iFick showed moderate correlation with direct Fick (R2 = 0.49 and R2 = 0.38, p < 0.001 for both), while Dehmer and Bergstra iFick showed poor correlation with direct Fick (R2 = 0.29 and R2 = 0.31, p < 0.001 for both). Absolute bias between all CO estimation techniques and direct Fick CO was lowest for TD compared to iFick methods but significant for all methods. All methods tended to overestimate CO compared to direct Fick, with greatest overestimation present in those with the lowest measured direct Fick CO. Bias and frequency of significant discrepancy were least using TD and Lafarge iFick CO estimation methods in this study, with TD CO demonstrating modestly better correlation and less heteroscedasticity compared to Lafarge.

Thermodilution-Based Invasive Assessment of Absolute Coronary Blood Flow and Microvascular Resistance: Quantification of Microvascular (Dys)Function?

During the last two decades, there has been a sharp increase in both interest and knowledge about the coronary microcirculation. Since these small vessels are not visible by the human eye, physiologic measurements should be used to characterize their function. The invasive methods presently used (coronary flow reserve (CFR) and index of microvascular resistance (IMR)) are operator-dependent and mandate the use of adenosine to induce hyperemia. In recent years, a new thermodilution-based method for measurement of absolute coronary blood flow and microvascular resistance has been proposed and initial procedural problems have been overcome. Presently, the technique is easy to perform using the Rayflow infusion catheter and the Coroventis software. The method is accurate, reproducible, and completely operator-independent. This method has been validated noninvasively against the current golden standard for flow assessment: Positron Emission Tomography-Computed Tomography (PET-CT). In addition, absolute flow and resistance measurements have proved to be safe, both periprocedurally and at long-term follow-up. With an increasing number of studies being performed, this method has great potential for better understanding and quantification of microvascular disease.

Noninvasive Assessment of Cardiac Output: Accuracy and Precision of the Closed-Circuit Acetylene Rebreathing Technique for Cardiac Output Measurement.

Background Accurate assessment of cardiac output is critical to the diagnosis and management of various cardiac disease states; however, clinical standards of direct Fick and thermodilution are invasive. Noninvasive alternatives, such as closed-circuit acetylene (C2H2) rebreathing, warrant validation. Methods and Results We analyzed 10 clinical studies and all available cardiopulmonary stress tests performed in our laboratory that included a rebreathing method and direct Fick or thermodilution. Studies included healthy individuals and patients with clinical disease. Simultaneous cardiac output measurements were obtained under normovolemic, hypovolemic, and hypervolemic conditions, along with submaximal and maximal exercise. A total of 3198 measurements in 519 patients were analyzed (mean age, 59 years; 48% women). The C2H2 method was more precise than thermodilution in healthy individuals with half the typical error (TE; 0.34 L/min [r=0.92] and coefficient of variation, 7.2%) versus thermodilution (TE=0.67 [r=0.70] and coefficient of variation, 13.2%). In healthy individuals during supine rest and upright exercise, C2H2 correlated well with thermodilution (supine: r=0.84, TE=1.02; exercise: r=0.82, TE=2.36). In patients with clinical disease during supine rest, C2H2 correlated with thermodilution (r=0.85, TE=1.43). C2H2 was similar to thermodilution and nitrous oxide (N2O) rebreathing technique compared with Fick in healthy adults (C2H2 rest: r=0.85, TE=0.84; C2H2 exercise: r=0.87, TE=2.39; thermodilution rest: r=0.72, TE=1.11; thermodilution exercise: r=0.73, TE=2.87; N2O rest: r=0.82, TE=0.94; N2O exercise: r=0.84, TE=2.18). The accuracy of the C2H2 and N2O methods was excellent (r=0.99, TE=0.58). Conclusions The C2H2 rebreathing method is more precise than, and as accurate as, the thermodilution method in a variety of patients, with accuracy similar to an N2O rebreathing method approved by the US Food and Drug Administration.

Assessment of Right Heart Function during Extracorporeal Therapy by Modified Thermodilution in a Porcine Model.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation therapy is a growing treatment modality for acute cardiorespiratory failure. Cardiac output monitoring during veno-arterial extracorporeal membrane oxygenation therapy remains challenging. This study aims to validate a new thermodilution technique during veno-arterial extracorporeal membrane oxygenation therapy using a pig model. METHODS: Sixteen healthy pigs were centrally cannulated for veno-arterial extracorporeal membrane oxygenation, and precision flow probes for blood flow assessment were placed on the pulmonary artery. After chest closure, cold boluses of 0.9% saline solution were injected into the extracorporeal membrane oxygenation circuit, right atrium, and right ventricle at different extracorporeal membrane oxygenation flows (4, 3, 2, 1 l/min). Rapid response thermistors in the extracorporeal membrane oxygenation circuit and pulmonary artery recorded the temperature change. After calculating catheter constants, the distributions of injection volumes passing each circuit were assessed and enabled calculation of pulmonary blood flow. Analysis of the exponential temperature decay allowed assessment of right ventricular function. RESULTS: Calculated blood flow correlated well with measured blood flow (r2 = 0.74, P < 0.001). Bias was -6 ml/min [95% CI ± 48 ml/min] with clinically acceptable limits of agreement (668 ml/min [95% CI ± 166 ml/min]). Percentage error varied with extracorporeal membrane oxygenation blood flow reductions, yielding an overall percentage error of 32.1% and a percentage error of 24.3% at low extracorporeal membrane oxygenation blood flows. Right ventricular ejection fraction was 17 [14 to 20.0]%. Extracorporeal membrane oxygenation flow reductions increased end-diastolic and end-systolic volumes with reductions in pulmonary vascular resistance. Central venous pressure and right ventricular ejection fractions remained unchanged. End-diastolic and end-systolic volumes correlated highly (r2 = 0.98, P < 0.001). CONCLUSIONS: Adapted thermodilution allows reliable assessment of cardiac output and right ventricular behavior. During veno-arterial extracorporeal membrane oxygenation weaning, the right ventricle dilates even with stable function, possibly because of increased venous return.

Doppler echocardiography for assessment of systemic vascular resistances in cardiogenic shock patients.

OBJECTIVE: Impaired vascular tone plays an important role in cardiogenic shock. Doppler echocardiography provides a non-invasive estimation of systemic vascular resistance. The aim of the present study was to compare Doppler echocardiography with the transpulmonary thermodilution method for the assessment of systemic vascular resistance in patients with cardiogenic shock. METHODS: This prospective monocentric comparison study was conducted in a single cardiology intensive care unit (Hopital Nord, Marseille, France). We assessed the systemic vascular resistance index by both echocardiography and transpulmonary thermodilution in 28 patients admitted for cardiogenic shock, on admission and after the introduction of an inotrope or vasopressor treatment. RESULTS: A total of 35 paired echocardiographic and transpulmonary thermodilution estimations of the systemic vascular resistance index were compared. Echocardiography values ranged from 1309 to 3526 dynes.s.m2/cm5 and transpulmonary thermodilution values ranged from 1320 to 3901 dynes.s.m2/cm5. A statistically significant correlation was found between echocardiography and transpulmonary thermodilution (r=0.86, 95% confidence interval (CI) 0.74, 0.93; P<0.0001). The intraclass correlation coefficient was 0.84 (95% CI 0.72, 0.92). The mean bias was -111.95 dynes.s.m2/cm5 (95% CI -230.06, 6.16). Limits of agreement were -785.86, 561.96. CONCLUSIONS: Doppler echocardiography constitutes an accurate non-invasive alternative to transpulmonary thermodilution to provide an estimation of systemic vascular resistance in patients with cardiogenic shock.

Are Peripherally Inserted Central Catheters Suitable for Cardiac Output Assessment With Transpulmonary Thermodilution?

OBJECTIVES: Peripherally inserted central catheters are increasingly used in ICU as an alternative to centrally inserted central catheters for IV infusion. However, their reliability for hemodynamic measurements with transpulmonary thermodilution is currently unknown. We investigated the agreement between transpulmonary thermodilution measurements obtained with bolus injection through peripherally inserted central catheter and centrally inserted central catheter (reference standard) using a transpulmonary thermodilution-calibrated Pulse Contour hemodynamic monitoring system (VolumeView/EV1000). DESIGN: Prospective method-comparison study. SETTING: Twenty-bed medical-surgical ICU of a teaching hospital. PATIENTS: Twenty adult ICU patients who required hemodynamic monitoring because of hemodynamic instability and had both peripherally inserted central catheter and centrally inserted central catheter in place. INTERVENTION: The hemodynamic measurements obtained by transpulmonary thermodilution after injection of a cold saline bolus via both centrally inserted central catheter and either a single-lumen 4F or a double-lumen 5F peripherally inserted central catheter using were compared. In order to rule out bias related to manual injection, measurements were repeated using an automated rapid injection system. MEASUREMENTS AND MAIN RESULTS: A total of 320 measurements were made. Cardiac index was significantly higher when measured with double-lumen 5F peripherally inserted central catheter than with centrally inserted central catheter (mean, 4.5 vs 3.3 L/min/m; p < 0.0001; bias, 1.24 L/min/m [0.27, 2.22 L/min/m]; bias percentage, 31%). Global end-diastolic index, extravascular lung water index, and stroke volume index were also overestimated (853 ± 240 vs 688 ± 175 mL/m, 12.2 ± 4.2 vs 9.4 ± 2.9 mL/kg, and 49.6 ± 14.9 vs 39.5 ± 9.6 mL/m, respectively; p < 0.0001). Lower, albeit significant differences were found using single-lumen 4F peripherally inserted central catheter (mean cardiac index, 4.2 vs 3.7 L/min/m; p = 0.043; bias, 0.51 L/min/m [-0.53, 1.55 L/min/m]; bias percentage, 12.7%). All differences were confirmed, even after standardization of bolus speed with automated injection. CONCLUSIONS: Bolus injection through peripherally inserted central catheter for transpulmonary thermodilution using EV1000 led to a significant overestimation of cardiac index, global end-diastolic index, extravascular lung water index, and stroke volume index, especially when double-lumen 5F peripherally inserted central catheter was used (ClinicalTrial.gov NCT03834675).

Noninvasive assessment of Cardiac Index using impedance cardiography during liver transplantation surgery: a comparison with pulmonary artery thermodilution.

BACKGROUND: Liver transplantation (LT) is a high-risk surgery associated with significant hemodynamic changes requiring advanced hemodynamic monitoring. Pulmonary Artery Catheter (PAC) is still considered as a gold-standard for Cardiac Index (CI) measurement during LT despite association with an increased risk of complications. Noninvasive impedance cardiography (ICG) could be an interesting alternative tool for CI monitoring. The aim of this study was to compare the precision and trending ability of ICG versus PAC methods during LT. METHODS: Patients undergoing LT were prospectively included. CI was measured with PAC and ICG at 4 time points (T1: before surgical incision, T2: during anhepatic phase, T3: after portal reperfusion, T4: during wound closure). Bias and percentage error (PE) between CI measured with PAC and ICG were analyzed with the Bland-Altman method for repeated measurements. Trending ability was studied with 4-quadrant and polar plots and correlation coefficient. RESULTS: We included 43 patients with 156 measures. Mean bias was -0.95 L.min-1.m-2, SD±1.07, limits of agreement -3.73 to 1.83 L.min-1.m-2 and PE 58%. There was a significant increase in bias during LT (P<0.001). Assessment of trending ability displayed a concordance rate of 72% on the 4-quadrant plot and a mean angular bias of -8.4° (SD±28°) and radial limits of agreement ±55° on the polar plot. CONCLUSIONS: CI measurements using ICG exhibited a low precision and a poor trending ability when compared to thermodilution method during LT. Consequently, ICG is not an adequate hemodynamic tool to monitor CI during LT.

Assessment of lung edema during ex-vivo lung perfusion by single transpulmonary thermodilution: A preliminary study in humans.

BACKGROUND: Single transpulmonary thermodilution (SD) with extravascular lung water index (EVLWI) could become a new tool to better assess lung graft edema during ex-vivo lung perfusion (EVLP). In this study we compare EVLWI with conventional methods to better select lungs during EVLP and to predict post-transplant primary graft dysfunction (PGD). METHODS: We measured EVLWI, arterial oxygen/fraction of inspired oxygen (P/F) ratio, and static lung compliance (SLC) during EVLP in an observational study. At the end of EVLP, grafts were accepted or rejected according to a standardized protocol blinded to EVLWI results. We compared the respective ability of EVLWI, P/F, and SLC to predict PGD. Mann-Whitney U-test, Fisher's exact test, and receiver-operating characteristic (ROC) curve data were used for analysis. p < 0.05 was considered statistically significant. RESULTS: Thirty-five lungs were evaluated by SD during EVLP. Three lungs were rejected for pulmonary edema. Thirty-two patients were transplanted, 8 patients developed Grade 2 or 3 PGD, and 24 patients developed Grade 0 or 1 PGD. In contrast to P/F ratio, SLC, and pulmonary artery pressure, EVLWI differed between these 2 populations (p < 0.001). The area under the ROC for EVLWI assessing Grade 2 or 3 PGD at the end of EVLP was 0.93. Donor lungs with EVLWI >7.5 ml/kg were more likely associated with a higher incidence of Grade 2 or 3 PGD at Day 3. CONCLUSIONS: Increased EVLWI during EVLP was associated with PGD in recipients.

Assessment of interchangeability rate between 2 methods of measurements: An example with a cardiac output comparison study.

The Bland-Altman (BA) and percentage error (PE) methods have been previously described to assess the agreement between 2 methods of medical or laboratory measurements. This type of approach raises several problems: the BA methodology constitutes a subjective approach to interchangeability, whereas the PE approach does not take into account the distribution of values over a range. We describe a new methodology that defines an interchangeability rate between 2 methods of measurement and cutoff values that determine the range of interchangeable values. We used a simulated data and a previously published data set to demonstrate the concept of the method. The interchangeability rate of 5 different cardiac output (CO) pulse contour techniques (Wesseling method, LiDCO, PiCCO, Hemac method, and Modelflow) was calculated, in comparison with the reference pulmonary artery thermodilution CO using our new method. In our example, Modelflow with a good interchangeability rate of 93% and a cutoff value of 4.8 L min, was found to be interchangeable with the thermodilution method for >95% of measurements. Modelflow had a higher interchangeability rate compared to Hemac (93% vs 86%; P = .022) or other monitors (Wesseling cZ = 76%, LiDCO = 73%, and PiCCO = 62%; P < .0001). Simulated data and reanalysis of a data set comparing 5 CO monitors against thermodilution CO showed that, depending on the repeatability of the reference method, the interchangeability rate combined with a cutoff value could be used to define the range of values over which interchangeability remains acceptable.

Hemodynamic Assessment of Patients With Septic Shock Using Transpulmonary Thermodilution and Critical Care Echocardiography: A Comparative Study.

BACKGROUND: To assess the agreement between transpulmonary thermodilution (TPT) and critical care echocardiography (CCE) in ventilated patients with septic shock. METHODS: Ventilated patients in sinus rhythm requiring advanced hemodynamic assessment for septic shock were included in this prospective multicenter descriptive study. Patients were assessed successively using TPT and CCE in random order. Data were interpreted independently at bedside by two investigators who proposed therapeutic changes on the basis of predefined algorithms. TPT and CCE hemodynamic assessments were reviewed offline by two independent experts who identified potential sources of discrepant results by consensus. Lactate clearance and outcome were studied. RESULTS: A total of 137 patients were studied (71 men; age, 61 ± 15 years; Simplified Acute Physiologic Score, 58 ± 18; Sequential Organ Failure Assessment, 10 ± 3). TPT and CCE interpretations at bedside were concordant in 87/132 patients (66%) without acute cor pulmonale (ACP), resulting in a moderate agreement (kappa, 0.48; 95% CI, 0.37-0.60). Experts' adjudications were concordant in 100/129 patients without ACP (77.5%), resulting in a good intertechnique agreement (kappa, 0.66; 95% CI, 0.55-0.77). In addition to ACP (n = 8), CCE depicted a potential source of TPT inaccuracy in 8/29 patients (28%). Lactate clearance at H6 was similar irrespective of the concordance of online interpretations of TPT and CCE (55/84 [65%] vs 32/45 [71%], P = .55). ICU and day 28 mortality rates were similar between patients with concordant and discordant interpretations (29/87 [36%] vs 13/45 [29%], P = .60; and 31/87 [36%] vs 16/45 [36%], P = .99, respectively). CONCLUSIONS: Agreement between TPT and CCE was moderate when interpreted at bedside and good when adjudicated offline by experts, but without impact on lactate clearance and mortality.

Invasive Assessment of the Coronary Microvasculature: The Index of Microcirculatory Resistance.

Traditionally, invasive coronary physiological assessment has focused on the epicardial coronary artery. More recently, appreciation of the importance of the coronary microvasculature in determining patient outcomes has grown. Several invasive modalities for interrogating microvascular function have been proposed. Angiographic techniques have been limited by their qualitative and subjective nature. Doppler wire-derived coronary flow reserve has been applied in research studies, but its clinical role has been limited by its lack of reproducibility, its lack of a clear normal value, and the fact that it is not specific for the microvasculature but interrogates the entire coronary circulation. The index of microcirculatory resistance-a thermodilution-derived measure of the minimum achievable microvascular resistance-is relatively easy to measure, more reproducible, has a clearer normal value, and is independent of epicardial coronary artery stenosis. The index of microcirculatory resistance has been shown to have prognostic value in patients with ST-segment-elevation myocardial infarction and cardiac allograft vasculopathy after heart transplantation. Emerging data demonstrate its role in evaluating patients with chest pain and nonobstructive coronary artery disease. Increasingly, the index of microcirculatory resistance is used as a reference standard for invasively assessing the microvasculature in clinical trials.

Transpulmonary Thermodilution: Its Role in Assessment of Lung Water and Pulmonary Edema.

Tissue edema, in particular pulmonary edema, increasingly is recognized as a perioperative complication affecting outcome. Management strategies directed at avoiding excessive fluid administration, reducing inflammatory response, and decreasing capillary permeability commonly are advocated in perioperative care protocols. In this review, transpulmonary thermodilution (TPTD) as a bedside tool to quantitatively monitor lung water accumulation and optimize fluid therapy is examined. Furthermore, the roles of TPTD as an early detector of fluid accumulation before the development of overt pulmonary edema and in risk stratification are explored. In addition, the ability of TPTD to provide insight into the etiology of pulmonary edema, specifically differentiating hydrostatic versus increased pulmonary capillary permeability, is emerging as an aid in therapeutic decision-making. The combination of hemodynamic and lung water data afforded by TPTD offers unique benefits for the care of high-risk perioperative patients.

Pulse contour cardiac output monitoring in acute heart failure patients : Assessment of hemodynamic measurements.

BACKGROUND: Heart failure is known to be a major public health problem. Fluid redistribution contributes to acute heart failure; therefore, knowledge of hemodynamic parameters could be important for optimizing outcomes. The pulse contour cardiac output monitor PiCCO uses the single thermal indicator technique and pulse contour analysis to calculate hemodynamic parameters of preload, afterload, cardiac output, systemic vascular resistance and extravascular lung water. OBJECTIVES: We primarily aimed to describe values and parameters seen in acute heart failure patients admitted to the intensive care unit (ICU) and secondly to investigate associations between hemodynamic measurements and survival data. MATERIAL AND METHODS: In this study 420 consecutive patients admitted to a tertiary medical university hospital ICU between January 2004 and December 2009 were retrospectively investigated. The study sample was divided into two subgroups: patients monitored by PiCCO (n = 47) and those not monitored by thermodilution measurements (n = 373). No predetermined treatment algorithm based on knowledge obtained by the PiCCO monitor was used and measurements were individually interpreted by the treating physician. The PiCCO monitor measurements were carried out according to manufacturer's directions. RESULTS: Patients with PiCCO monitoring were clinically in poorer health with a mean simplified acute physiology score II (SAPS2) of 45 ± 17 vs. 56 ± 20 (p < 0.01). The ICU mortality (22 % vs. 38 %, p = 0.02) and, at least as a tendency, long-term-mortality were increased in patients monitored by PiCCO (RR 1.49, 95 % CI 0.96-2.31, p = 0.08). We provide hemodynamic measurements in acute heart failure patients: cardiac index (2.7 ± 1.2 l/min/m²) was reduced, preload and extravascular lung water index (EVLWI, 11.5 ± 5.1 ml/kg body weight), representing lung edema, were increased. CONCLUSION: We provide real world values for PiCCO parameters in acutely decompensated heart failure. In our study patients who were clinically in poorer health were monitored with PiCCO, resulting in increased mortality in this group. Further prospective studies to investigate the effects of treatment decisions triggered by information obtained by PiCCO monitoring for patients in acute heart failure are needed.

Constant infusion transpulmonary thermodilution for the assessment of cardiac output in exercising humans.

To determine the accuracy and precision of constant infusion transpulmonary thermodilution cardiac output (CITT-Q) assessment during exercise in humans, using indocyanine green (ICG) dilution and bolus transpulmonary thermodilution (BTD) as reference methods, cardiac output (Q) was determined at rest and during incremental one- and two-legged pedaling on a cycle ergometer, and combined arm cranking with leg pedaling to exhaustion in 15 healthy men. Continuous infusions of iced saline in the femoral vein (n = 41) or simultaneously in the femoral and axillary (n = 66) veins with determination of temperature in the femoral artery were used for CITT-Q assessment. CITT-Q was linearly related to ICG-Q (r = 0.82, CITT-Q = 0.876 × ICG-Q + 3.638, P < 0.001; limits of agreement ranging from -1.43 to 3.07 L/min) and BTD-Q (r = 0.91, CITT-Q = 0.822 × BTD + 4.481 L/min, P < 0.001; limits of agreement ranging from -1.01 to 2.63 L/min). Compared with ICG-Q and BTD-Q, CITT-Q overestimated cardiac output by 1.6 L/min (≈ 10% of the mean ICG and BTD-Q values, P < 0.05). For Q between 20 and 28 L/min, we estimated an overestimation < 5%. The coefficient of variation of 23 repeated CITT-Q measurements was 6.0% (CI: 6.1-11.1%). In conclusion, cardiac output can be precisely and accurately determined with constant infusion transpulmonary thermodilution in exercising humans.

Comprehensive assessment of microcirculation after primary percutaneous intervention in ST-segment elevation myocardial infarction: insight from thermodilution-derived index of microcirculatory resistance and coronary flow reserve.

OBJECTIVES: A pathophysiological mechanism of microvascular dysfunction in ST-segment elevation myocardial infarction (STEMI) is multifactorial; thus, multiple modalities were needed to precisely evaluate a microcirculation. METHODS: We complementarily assessed microcirculation in STEMI by the index of microcirculatory resistance (IMR) and coronary flow reserve (CFR) immediately after a primary percutaneous intervention in 89 STEMI patients. Cardiovascular and cerebrovascular events (MACCE) including cardiovascular death, target vessel failure, heart failure, and stroke were assessed during a mean follow-up period of 3.0 years. RESULTS: The microcirculation of enrolled patients was classified into four groups using cutoff CFR and IMR values (CFR>2 and mean IMR): group-1 (n=23, CFR>2 and IMR ≤ 27); group-2 (n=31, CFR ≤ 2 and IMR ≤ 27); group-3 (n=9, CFR>2 and IMR>27); and group-4 (n=26, CFR<2 and IMR>27). On echocardiography 3 months later, improvement in the wall motion score index was shown in group-1 (P<0.01), group-2 (P<0.01), and group-3 (P=0.04), whereas group-4 did not show improvement in wall motion score index (P=0.06). During clinical follow-up, there were no MACCE in group-1 and the patients in group-2 and group-3 showed significantly lower MACCE compared with group-4 (group-1=0%, group-2, and group-3=10%, group-4=23.1%, P=0.04). CONCLUSION: Complimentary assessment of microcirculation by the IMR and CFR may be useful to evaluate myocardial viability and the long-term prognosis of STEMI patients.

Novel continuous capnodynamic method for cardiac output assessment during mechanical ventilation.

BACKGROUND: It is important to be able to accurately monitor cardiac output (CO) during high-risk surgery and in critically ill patients. The invasiveness of the pulmonary artery catheter (PAC) limits its use, and therefore, new minimally invasive methods for CO monitoring are needed. A potential method is estimation of CO from endogenous carbon dioxide measurements, using a differentiated Fick's principle to determine effective pulmonary blood flow (EPBF). In this study, we aimed to validate a novel capnodynamic method (COEPBF) in a wide range of clinically relevant haemodynamic conditions. METHODS: COEPBF was studied in 10 pigs during changes in preload, afterload, CO increase, and bleeding. An ultrasonic flow probe around the pulmonary artery was used as reference method of CO determination. CO was also measured using a PAC thermodilution technique (COPAC). CO and other haemodynamic data were recorded before and during each intervention. Accuracy and precision and also the ability to track changes in CO were determined using Bland-Altman, four-quadrant plot and polar plot analysis. RESULTS: COEPBF and COPAC showed equally good agreement, with a tendency to overestimate CO (bias 0.2 and 0.3 litre min(-1), respectively). The overall percentage error was 47% for COEPBF and 49% for COPAC. The concordance for tracking CO changes was 97 and 95% for COEPBF and COPAC, respectively, with an exclusion zone of 15% and radial limits of ±30°. CONCLUSIONS: COEPBF showed reliable trending abilities, equivalent to COPAC. COEPBF and COPAC also showed low bias but high percentage errors. Further studies in animal models of lung injury and in high-risk surgery patients are warranted.