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Mathematical coupling may explain in part why cardiac filling volumes obtained by transpulmonary thermodilution may better predict and monitor responses of cardiac output to fluid loading than pressures obtained by pulmonary artery catheters (PACs).Eleven consecutive patients with hypovolaemia after coronary surgery and a PAC, allowing central venous pressure (CVP) and continuous cardiac index (CCIp) measurements, received a femoral artery catheter for transpulmonary thermodilution measurements of global end-diastolic blood volume index (GEDVI) and cardiac index (CItp). One to five colloid fluid-loading steps of 250 ml were done in each patient (n = 48 total).Fluid responses were predicted and monitored similarly by CItp and CCIp, whereas CItp and CCIp correlated at r = 0.70 (P0.001) with a bias of 0.40 l min(-1) m(-2). Changes in volumes (and not in CVP) related to changes in CItp and not in CCIp. Changes in CVP and GEDVI similarly related to changes in CItp, after exclusion of two patients with greatest CItp outliers (as compared to CCIp). Changes in GEDVI correlated better to changes in CItp when derived from the same thermodilution curve than to changes in CItp of unrelated curves and changes in CCIp.After coronary surgery, fluid responses can be similarly assessed by intermittent transpulmonary and continuous pulmonary thermodilution methods, in spite of overestimation of CCIp by CItp. Filling pressures are poor monitors of fluid responses and superiority of GEDVI can be caused, at least in part, by mathematical coupling when cardiac volume and output are derived from the same thermodilution curve.

Objective A new method to estimate mean cardiac output by thermodilution with a single duration-controlled injection was evaluated in patients. Design Prospective criterion standard study. Setting University hospital cardiac surgical intensive care unit and cardiac operation room. Patients Of 33 patients, 24 underwent coronary bypass graft surgery, four had a valve replacement, and five were treated in the intensive care unit. Interventions Interventions consisted of thermodilution cardiac output measurements. One single duration-controlled injection of cold fluid was used to calculate cardiac output. This controlled injection was performed with a duration equal to one whole ventilation cycle of the ventilator. An algorithm adapted to this duration-controlled injection calculated cardiac output. Moreover, this algorithm has properties to reduce errors caused by artificial ventilation and thermal noise. Measurements and Main Results In 33 patients, the averaged values of four measurements equally spread over the ventilatory cycle (phase-controlled) were compared with the values of two single duration-controlled measurements. The measurements were performed during periods of stable respiration and circulation. No significant difference was observed between the mean of four phase-controlled measurements and the mean of the two duration-controlled measurements. The cardiac output values in the intensive care patients were significantly higher compared with the two other patient groups (p .05). The coefficient of variation of the single duration-controlled thermodilution measurements was significantly lower than the single phase-controlled measurements, 3% vs. 6% (p Conclusions One single duration-controlled injection thermodilution measurement is as accurate and repeatable as the mean of four phase-controlled measurements and is clinically feasible.

PURPOSE: The purpose of this study was to determine the dynamic changes in right ventricular (RV) and left ventricular (LV) output during positive airway pressure inspiratory hold maneuvers so as to characterize the interaction of processes in creating steady-state cardiac output during positive pressure ventilation. MATERIALS AND METHODS: We examined the disparity of RV and LV outputs at 5 seconds (early) and 20 seconds (late) into a 24-second inspiratory hold maneuver in 14 subjects in the intensive care unit immediately following coronary artery bypass surgery. RV output was measured by the thermodilution technique, whereas LV output was measured by the arterial pulse contour method. RV and LV volumes were also measured by thermal and radionuclide ejection fraction techniques, respectively. RESULTS: As P(aw) was progressively increased from 0 to 20 cm H2O in sequential inspiratory hold maneuvers, both RV and LV outputs changed differently both at 5 seconds and 20 seconds into the inspiratory hold maneuvers. When expressed as change in cardiac output (L/min) for every cm H2O P(aw) increase relative to end-expiratory values, RV output increased at 5 seconds (0.05 +/- 0.15 L/min) then decreased at 20 seconds (-0.08 +/- 0.21, P < .05). LV output decreased slightly at 5 seconds (-0.14 +/- 0.22) and did not change from this minimal depressed level at 20 seconds (P < .05). Changes in RV and LV output were paralleled by changes in RV and LV end-diastolic volumes, respectively. CONCLUSION: Positive pressure inspiration induces time-dependent changes in central hemodynamics, which are dissimilar between RV and LV function. Initially, inspiration increases RV output but decreases LV output, such that intrathoracic blood volume increases. However, sustained inspiratory pressures induce proportionally similar decreases in both RV and LV outputs. Thus, the hemodynamic effects of positive pressure ventilation will depend on the degree of lung inflation, the inspiratory time, and when measurements are made within the ventilatory cycle. These data also suggest that positive pressure ventilation with up to 20 cm H2) P(aw) does not significantly impair ventricular performance in humans

External leg compression (ELC) may increase cardiac output (CO) in fluid-responsive patients like passive leg raising (PLR). We compared the hemodynamic effects of two methods of ELC and PLR measured by thermodilution (COtd), pressure curve analysis Modelflow (TM) (COmf) and ultra-sound HemoSonic (TM) (COhs), to evaluate the method with the greatest hemodynamic effect and the most accurate less invasive method to measure that effect. We compared hemodynamic effects of two different ELC methods (circular, A (n = 16), vs. wide, B (n = 13), bandages inflated to 30 cm H2O for 15 min) with PLR prior to each ELC method, in 29 post-operative cardiac surgical patients. Hemodynamic responses were measured with COtd, COmf and COhs. PLR A increased COtd from 6.1 +/- A 1.7 to 6.3 +/- A 1.8 L center dot min(-1) (P = 0.016), and increased COhs from 4.9 +/- A 1.5 to 5.3 +/- A 1.6 L center dot min(-1) (P = 0.001), but did not increase COmf. ELC A increased COtd from 6.4 +/- A 1.8 to 6.7 +/- A 1.9 L center dot min(-1) (P = 0.001) and COmf from 6.9 +/- A 1.7 to 7.1 +/- A 1.8 L center dot min(-1) (P = 0.021), but did not increase COhs. ELC A increased COtd and COmf as in PLR A. PLR B increased COtd from 5.4 +/- A 1.3 to 5.8 +/- A 1.4 L center dot min(-1) (P < 0.001), and COhs from 5.0 +/- A 1.0 to 5.4 +/- A 1.0 L center dot min(-1) (P = 0.013), but not COmf. ELC B increased COtd from 5.2 +/- A 1.2 to 5.4 +/- A 1.1 L center dot min(-1) (P = 0.003), but less than during PLR B (P = 0.012), while COmf and COhs did not change. Bland-Altman and polar plots showed lower limits of agreement with changes in COtd for COmf than for COhs. The circular leg compression increases CO more than bandage compression, and is able to increase CO as in PLR. The less invasive Modelflow (TM) can detect these changes reasonably well.

OBJECTIVE:: To measure the relationship between blood flow and central venous pressure (Pcv) and to estimate mean systemic filling pressure (Pmsf), circulatory compliance, and stressed volume in patients in the intensive care unit. DESIGN:: Intervention study. SETTING:: Intensive care unit of a university hospital. PATIENTS:: Twelve mechanically ventilated postoperative cardiac surgery patients. INTERVENTIONS:: Inspiratory holds were performed during normovolemia in supine position (baseline), relative hypovolemia by placing the patients in 30 degree head-up position (hypo), and relative hypervolemia by volume loading with 0.5 L colloid (hyper). MEASUREMENTS AND MAIN RESULTS:: We measured the relationship between blood flow and Pcv using 12-second inspiratory-hold maneuvers transiently increasing Pcv to three different steady-state levels and monitored the resultant blood flow via the pulse contour method during the last 3 seconds. The Pcv to blood flow relation was linear for all measurements with a slope unaltered by relative volume status. Pmsf decreased with hypo and increased with hyper (18.8 ± 4.5 mm Hg, to 14.5 ± 3.0 mm Hg, to 29.1 ± 5.2 mm Hg [baseline, hypo, hyper, respectively, p < 0.05]). Baseline total circulatory compliance was 0.98 mL•mm Hg•kg and stressed volume was 1677 mL. CONCLUSIONS:: Pmsf can be determined in intensive care patients with an intact circulation with use of inspiratory pause procedures, making serial measures of circulatory compliance and circulatory stressed volume feasible. © 2009 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.

Background and aims: Cardiac function may differ after valvular (VS) and coronary artery (CAS) surgery and this may affect assessment of fluid responsiveness. The aim of the study was to compare VS and CAS in the value of cardiac fitting pressures and volumes herein. Methods: There were eight consecutive patients after VS and eight after CAS, with femoral and pulmonary artery catheters in place. In each patient, five sequential fluid loading steps of 250 ml of colloid each were done. We measured central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP) and, by transpulmonary thermodilution, cardiac index (CI) and global end-diastolic (GEDVI) and intrathoracic blood volume (ITBVI) indices. Fluid responsiveness was defined by a Cl increase >5% or >10% per step. Results: Global ejection fraction was tower and PAOP was higher after VS than CAS. In responding steps after VS (n = 9-14) PACP and volumes increased, white CVP and volumes increased in responding steps (n = 12-19) after CAS. Baseline PAOP was tower in responding steps after VS only. Hence, baseline PACP as well as changes in PACP and volumes were of predictive value after VS and changes in CVP and volumes after CAS, in receiver operating characteristic curves. After VS, PAOP and volume changes equally correlated to Cl changes. After CAS, only changes in CVP and volumes correlated to those in Cl. Conclusions: While volumes are equally useful in monitoring fluid responsiveness, the predictive and monitoring value of PAOP is greater after VS than after CAS. In contrast, the CVP is of similar value as volume measurements in monitoring fluid responsiveness after CAS. The different value of pressures rather than of volumes between surgery types is likely caused by systolic left ventricular dysfunction in VS. The study suggests an effect of systolic cardiac function on optimal parameters of fluid responsiveness and superiority of the pulmonary artery catheter over transpulmonary dilution, for haemodynamic monitoring of VS patients. (C) 2008 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

The hemodynamic effects of increases in airway pressure (Paw) are related in part to Paw-induced increases in right atrial pressure (Pra), the downstream pressure for venous return, thus decreasing the pressure gradient for venous return. However, numerous animal and clinical studies have shown that venous return is often sustained during ventilation with positive end-expiratory pressure (PEEP). Potentially, PEEP-induced diaphragmatic descent increases abdominal pressure (Pabd). We hypothesized that an increase in Paw induced by PEEP would minimally alter venous return because the associated increase in Pra would be partially offset by a concomitant increase in Pabd. Thus we studied the acute effects of graded increases of Paw on Pra, Pabd, and cardiac output by application of inspiratory-hold maneuvers in sedated and paralyzed humans. Forty-two patients were studied in the intensive care unit after coronary artery bypass surgery during hemodynamically stable, fluid-resuscitated conditions. Paw was progressively increased in steps of 2 to 4 cmH2O from 0 to 20 cmH2O in sequential 25-s inspiratory-hold maneuvers. Right ventricular (RV) cardiac output (COtd) and RV ejection fraction (EFrv) were measured at 5 s into the inspiratory-hold maneuver by the thermodilution technique. RV end-diastolic volume and stroke volume were calculated from EFrvand heart rate data, and Pra was measured from the pulmonary artery catheter. Pabd was estimated as bladder pressure. We found that, although increasing Paw progressively increased Pra, neither COtdnor RV end-diastolic volume changed. The ratio of change (Δ) in Paw to ΔPra was 0.32 ± 0.20. The ratio of ΔPra to ΔCOtdwas 0.05 ± 00.15 l · min−1· mmHg−1. However, Pabd increased such that the ratio of ΔPra to ΔPabd was 0.73 ± 0.36, meaning that most of the increase in Pra was reflected in increases in Pabd. We conclude that, in hemodynamically stable fluid-resuscitated postoperative surgical patients, inspiratory-hold maneuvers with increases in Paw of up to 20 cmH2O have minimal effects on cardiac output, primarily because of an in-phase-associated pressurization of the abdominal compartment associated with compression of the liver and squeezing of the lungs.