Thermodilution Cardiac Output Research Articles

The ability of a new continuous cardiac output monitor to measure trends in cardiac output following implementation of a patient information calibration and an automated exclusion algorithm

A new non-invasive continuous cardiac output (esCCO) monitoring system solely utilizing a routine cardiovascular monitor was developed, even though a reference cardiac output (CO) is consistently required. Subsequently, a non-invasive patient information CO calibration together with a new automated exclusion algorithm was implemented in the esCCO system. We evaluated the accuracy and trending ability of the new esCCO system. Either operative or postoperative data of a multicenter study in Japan for evaluation of the accuracy of the original version of esCCO system were used to develop the new esCCO system. A total of 207 patients, mostly cardiac surgical patients, were enrolled in the study. Data were manually reviewed to formulate a new automated exclusion algorithm with enhanced accuracy. Then, a new esCCO system based on a patient information calibration together with the automated exclusion algorithm was developed. CO measured with a new esCCO system was compared with the corresponding intermittent bolus thermodilution CO (ICO) utilizing statistical methods including polar plots analysis. A total of 465 sets of CO data obtained using the new esCCO system were evaluated. The difference in the CO value between the new esCCO and ICO was 0.34 ± 1.50 (SD) L/min (95 % confidence limits of −2.60 to 3.28 L/min). The percentage error was 69.6 %. Polar plots analysis showed that the mean polar angle was −1.6° and radial limits of agreement were ±53.3°. This study demonstrates that the patient information calibration is clinically useful as ICO, but trending ability of the new esCCO system is not clinically acceptable as judged by percentage error and polar plots analysis, even though it’s trending ability is comparable with currently available arterial waveform analysis methods.

Multicenter Study Verifying a Method of Noninvasive Continuous Cardiac Output Measurement Using Pulse Wave Transit Time

Many technologies have been developed for minimally invasive monitoring of cardiac output. Estimated continuous cardiac output (esCCO) measurement using pulse wave transit time is one noninvasive method. Because it does not require any additional sensors other than those for conducting 3 basic forms of monitoring (electrocardiogram, pulse oximeter wave, and noninvasive (or invasive) arterial blood pressure measurement), esCCO measurement is potentially useful in routine clinical circulatory monitoring for any patient including low-risk patients. We evaluated the efficacy of noninvasive esCCO using pulse wave transit time in this multicenter study. We compared esCCO and intermittent bolus thermodilution cardiac output (TDCO) in 213 patients, 139 intensive care units (ICUs), and 74 operating rooms (ORs), at 7 participating institutions. We performed electrocardiogram, pulse oximetry, TDCO, and arterial blood pressure measurements in patients in ICUs and ORs; a single calibration was performed to measure esCCO continuously. TDCO measurement was performed once daily for ICU patients and every hour for OR patients, and just before the removal of the pulmonary arterial catheter from patients in both the ICU and OR. We evaluated esCCO against TDCO with correlation analysis and Bland and Altman analysis and also assessed the change of bias over time. Furthermore, we inspected the impact of change in systemic vascular resistance (SVR) on change in bias because abnormal SVR was assumed to be a factor contributing to the change of the bias. From among 588 esCCO and TDCO datasets (excluding calibration points), 587 datasets were analyzed for 213 patients. The analysis results show a correlation coefficient of 0.79 (P < 0.0001, 95% confidence limits of 0.756-0.819), a bias (mean difference between esCCO and TDCO) of 0.13 L/min (95% confidence interval of bias 0.04-0.22 L/min), and a precision (1 SD) of 1.15 L/min (95% prediction interval was -2.13 to 2.39 L/min). There were no significant differences among 3 defined time intervals over 48 hours after calibration (repeated-measures analysis of variance P = 0.781) in the ICU. The influence of SVR on esCCO analysis showed a correlation coefficient between SVR and an error of 0.37 (P < 0.0001, 95% confidence interval 0.298-0.438). The efficacy of noninvasive esCCO technology was compared with TDCO in 213 cases. Five hundred eighty-seven datasets comparing esCCO and TDCO showed close correlation and small bias and precision, which were comparable to current arterial waveform analysis technologies.

Comparison of pulse contour versus pulmonary artery thermodilution cardiac output in patients undergoing elective open abdominal aortic aneurysm repair

Comparison of pulse contour versus pulmonary artery thermodilution cardiac output in patients undergoing elective open abdominal aortic aneurysm repair

Comparison of Invasive and Noninvasive Assessment of Aortic Stenosis Severity in the Elderly

Aortic valve area (AVA) in aortic stenosis (AS) can be assessed noninvasively or invasively, typically with similar results. These techniques have not been validated in elderly patients, where common assumptions make them most prone to error. Accurate assessment of AVA is crucial to determine which patients are appropriate candidates for aortic valve replacement. Fifty elderly patients (mean 86 years, 46% female) referred for cardiac catheterization to evaluate AS also underwent transthoracic echocardiography within 24 hours. To minimize assumptions all patients had 3-dimensional echocardiography (Echo-3D), and at catheterization using directly measured oxygen consumption (Cath-mVo(2)) and thermodilution cardiac output (Cath-TD). Correlation between Cath-mVo(2) and Echo-3D AVA was poor (r=0.41). Cath-TD AVA had a moderate correlation with Echo-3D AVA (r=0.59). Cath-mVo(2) (AVA=0.69 cm(2)) and Cath-TD (AVA=0.66 cm(2)) underestimated AVA compared with Echo-3D (AVA=0.76 cm(2;) P=0.08 for comparison with Cath-mVo(2); P=0.001 for Cath-TD). Compared with Echo-3D, the sensitivity and specificity for determining critical disease (AVA <0.8 cm(2)) were 81% and 42% for Cath-mVo(2), and 97% and 53% for Cath-TD. The only independent predictor of the difference between noninvasive and invasive AVA was stroke volume index (P<0.01). Resistance, a less flow-dependent measure, showed a stronger correlation between Echo-3D and Cath-mVo(2) (r=0.69), and Echo-3D and Cath-TD (r=0.77). Standard techniques of AVA assessment for AS show poor correlation in elderly patients, with frequent misclassification of critical AS. Less flow-dependent measures, such as resistance, should be considered to ensure that only appropriate patients are treated with aortic valve replacement.

002 A randomised study of temporary epicardial cardiac resynchronisation vs conventional right ventricular pacing in cardiac surgical patients

<h3>Introduction</h3> Left ventricular (LV) function is an important indicator of morbidity and mortality after cardiac surgery. Therefore, interventions to optimise peri-operative LV function may improve surgical outcomes. Biventricular (BiV) pacing has been shown to improve haemodynamic function in heart failure patients and temporary BiV pacing is feasible after cardiac surgery. Therefore, temporary BiV pacing may be beneficial to heart failure patients after cardiac surgery. <h3>Aim</h3> The aim of this trial was to investigate the clinical utility of temporary BiV pacing delivered via epicardial wires attached to the right atrium (RA), right ventricle (RV) and left ventricle (LV) after cardiac surgery. <h3>Methods</h3> 55 subjects undergoing elective cardiac surgery (coronary artery bypass grafting and/or valve surgery) were recruited from two cardiac centres, over an 18-month period commencing January 2010. 38 subjects completed the protocol. Nine subjects were removed at the operators request including: “off pump” bypass surgery, patient referred for alternative mode of revascularisation or surgical “turn down”. 19 subjects were randomly assigned to receive temporary (BiV) pacing using a dedicated triple chamber temporary pacing box with the capacity to programme the atrio-ventricular (AV) and inter-ventricular (VV) intervals. 19 received “standard pacing” after cardiac surgery. The duration of level 3 care was measured for each subject. In brief, this is the requirement for either invasive ventilation, multi-organ support or haemodynamic support with more than one inotrope/vasocontrictor or intra-aortic balloon pump. The trial was powered to compare the primary endpoint of transition from level 3 to level 2 care in the two groups. Secondary endpoints included acute haemodynamic performance in different pacing modes: immediately after the operation, 6 h, 18 h and 24 h after admission to cardiac intensive care. The pacing modes assessed included: atrial inhibited (AAI); ventricular inhibited (VVI-RV); dual chamber (DDD-RV); biventricular (DDD-BiV) and left ventricular pacing (DDD-LV). Base rate for pacing was set at 86/min and continued for the duration of level 3 care. The haemodynamic data were measured using a pulmonary arterial catheter using either thermodilution or continuous cardiac output measurements. <h3>Results</h3> The baseline demographics are illustrated in Abstract 002 table 1. The acute haemodynamic measurements at 18 h, Abstract 002 table 2. <h3>Conclusions</h3> BiV pacing significantly improved haemodynamics in the early part of the post-operative period compared to standard AAI pacing at 18 h. There is a suggestion that the improvement in haemodynamic function may translate into clinical benefit. The duration of level 3 care was 57.1 h in the standard pacing group compared to 44.5 h in the BiV group. However, the 22% reduction in level 3 care in the BiV group compared to the standard pacing group did not reach statistical significance.

Volume Status and Fluid Responsiveness

To the Editor, Dr. Lazaridus has presented a great review of advanced hemodynamic monitoring (AHM) [1]. Significant caution though must be used in accepting the accuracy of any noninvasive cardiac output methodology. The FDA 510 K approval process is not very rigorous and the comparison of noninvasive to invasive cardiac output (CO) is not done over a very large range of loading and unloading conditions. Hadian et al. [2] showed that FloTrac as well as other noninvasive CO devices showed widely varying results as compared to thermodilution (TD) CO and more importantly could trend in different directions under different loading conditions. The differences were in a range where therapy choices could be affected; possibly adversely. This type of testing is more clinically relevant and rigorous than the methodology used by Mutoh et al. [3] which assessed effects of volume loading but not that of vasoactive or inotropic drips. We have evaluated another noninvasive CO device in our unit, Cheetah, which measure CO by assessing changes in thoracic impedance and often found results diverging significantly from TD CO (unpublished data). In addition one of the statements ‘‘The ultimate goal of volume expansion is augmentation of stroke volume ...’’ may not be completely accurate. There is evidence that excess volume expansion may worse renal failure and increase mortality in the setting of sepsis [4, 5]. The fact that the patient is fluid responsive as evidenced by passive leg raise (PLR) test does confirm that the patient is not on the flat portion of the Frank-Sterling curve. However since cardiac output is not necessarily the goal endpoint of fluid resuscitation and excess fluid can cause harm, further data is needed before accepting results of PLR as a clinical volume resuscitation endpoint.

Cardiac Output Derived From Arterial Pressure Waveform Analysis: Validation of the Third-Generation Software in Patients Undergoing Orthotopic Liver Transplantation

BackgroundThe upgraded third-generation software (version 3.02) for the FloTrac/Vigileo system has been developed to particularly improve the accuracy of cardiac output (CO) measurements in hyperdynamic conditions. The aim of our study was to compare the CO values obtained using the FloTrac/Vigileo system during orthotopic liver transplantation (OLT) with those obtained in the same circumstances using a Swan-Ganz catheter (bolus thermodilution method). MethodsTwenty consecutive recipients scheduled for OLT were studied. Simultaneous CO values measured by both devices were obtained at 10 predefined time points throughout the surgery. A percentage error of not more than 30% was established as the criterion for device interchangeability. ResultsA total of 200 paired measurements were obtained. The CO values derived from the FloTrac/Viligeo ranged from 2.8 to 10.9 L/min, with a mean of 5.91 ± 1.81 L/min. The values from bolus thermodilution ranged from 2.2 to 13.2 L/min, with a mean of 6.12 ± 2.07 L/min. The bias was 0.22, and the limits of agreement were −3.13 to 3.56 L/min. The percentage error between the FloTrac/Viligeo and bolus thermodilution measurements was 54.93%. The percentage errors of paired measurements in three surgical phases by subgroup analysis were 43.50% (dissecting phase), 62.9% (anhepatic phase), and 56.05% (reperfusion phase), respectively. ConclusionCO measurements obtained using the less invasive arterial waveform FloTrac/Vigileo system upgraded with the third-generation software had poor intraoperative agreement with pulmonary artery thermodilution CO measurements in patients undergoing OLT.

Arterial pressure waveform derived cardiac output FloTrac/Vigileo system (third generation software): comparison of two monitoring sites with the thermodilution cardiac output

The present study was conducted to study the effect of monitoring site, radial or femoral, for arterial pressure waveform derived cardiac output using FloTrac/Vigileo system with third generation software version 3.02 during cardiac surgery. The cardiac output derived from the two sites was also compared to the pulmonary artery catheter (PAC) derived cardiac output to reevaluate the relation between them using the newer software. The effect of cardiopulmonary bypass (CPB) was also studied by doing the sub analysis before and after bypass. Forty patients undergoing coronary artery bypass surgery with cardiopulmonary bypass were enrolled in the study. Cardiac output derived from radial artery (RADCO), femoral artery (FEMCO) using FloTrac/Vigileo system with third generation software version 3.02 and cardiac output using pulmonary artery catheter (PACCO) at predefined nine time points were recorded. Three hundred and forty two cardiac output data triplets were analysed. The Bland-Altman analysis of RADCO and FEMCO revealed a mean bias of -0.28 with percentage error of 20%. The pre CPB precision of both RADCO and FEMCO was 1.25 times as that of PACCO. The post CPB precision of FEMCO was 1.2 times of PACCO while that of RADCO was 1.7 times of PACCO. The third generation of FloTrac/Vigileo system shows good correlation between the radial and femoral derived cardiac outputs in both pre and post bypass periods. The newer software correlates better to PAC derived cardiac output in the post bypass period for femoral artery than radial artery.

Effects of cardiac output levels on the measurement of transpulmonary thermodilution cardiac output in patients with acute lung injury

Transpulmonary thermodilution cardiac output (CO) correlates closely with pulmonary artery (PA) thermodilution CO. Levels of CO may contribute varying amounts of thermal indicator loss and recirculation during thermodilution CO measurement. This study aimed to investigate the effects of CO levels on the agreement between transpulmonary and PA thermodilution CO in acute lung injury (ALI) patients.

Impact of arterial catheter location on the accuracy of cardiac output provided by an endotracheal bioimpedance device

With respect to a radial arterial pressure measurement, a more central achievement of this pressure should improve the reliability of endotracheal bioimpedance cardiac output (CO) monitoring. We therefore compared prospectively the impact on accuracy of this device, in comparison with thermodilution (TD) CO.

Performance of Cardiac Output Measurement Derived From Arterial Pressure Waveform Analysis in Patients Requiring High-Dose Vasopressor Therapy

Background Arterial pressure waveform analysis of cardiac output (APCO) without external calibration (FloTrac/Vigileo™) is critically dependent upon computation of vascular tone that has necessitated several refinements of the underlying software algorithms. We hypothesized that changes in vascular tone induced by high-dose vasopressor therapy affect the accuracy of APCO measurements independently of the FloTrac software version. Methods In this prospective observational study, we assessed the validity of uncalibrated APCO measurements compared with transpulmonary thermodilution cardiac output (TPCO) measurements in 24 patients undergoing vasopressor therapy for the treatment of cerebral vasospasm after subarachnoid haemorrhage. Results Patients received vasoactive support with [mean (sd)] 0.53 (0.46) µg kg−1 min−1 norepinephrine resulting in mean arterial pressure of 104 (14) mm Hg and mean systemic vascular resistance of 943 (248) dyn s−1 cm−5. Cardiac output (CO) data pairs (158) were obtained simultaneously by APCO and TPCO measurements. TPCO ranged from 5.2 to 14.3 litre min−1, and APCO from 4.1 to 13.7 litre min−1. Bias and limits of agreement were 0.9 and 2.5 litre min−1, resulting in an overall percentage error of 29.6% for 68 data pairs analysed with the second-generation FloTrac® software and 27.9% for 90 data pairs analysed with the third-generation software. Precision of the reference technique was 2.6%, while APCO measurements yielded a precision of 29.5% and 27.9% for the second- and the third-generation software, respectively. For both software versions, bias (TPCO–APCO) correlated inversely with systemic vascular resistance. Conclusions In neurosurgical patients requiring high-dose vasopressor support, precision of uncalibrated CO measurements depended on systemic vascular resistance. Introduction of the third software algorithm did not improve the insufficient precision (>20%) for APCO measurements observed with the second software version.

Thermodilution and Fick Cardiac Outputs Differ: Impact on Pulmonary Hypertension Evaluation

The relationship between thermodilution and indirect Fick cardiac output determination methods has not been well described. To describe the relationship between these two cardiac output determination methods in patients evaluated for pulmonary hypertension and to highlight potential clinical implications. A retrospective review of charts of all adult patients who underwent a right heart catheterization (RHC) between January 1, 2007 and November 10, 2010, and participated in the pulmonary hypertension program of the pulmonary division at an academic institution was conducted. For validation, the charts of all patients who underwent RHC during the same period within the cardiology division were reviewed. A total of 198 patients underwent 213 RHCs, 79 (40%) of whom had pulmonary arterial hypertension, were included. Forty-three per cent of patients had >20% difference between thermodilution and Fick. The average difference (thermodilution - Fick ±SD) was -0.39±2.03 L⁄min (n=213; P=0.006). There was no significant difference in bias or variability between thermodilution and Fick among patients with tricuspid regurgitant jet velocity (TRJ) of <3 m⁄s versus those with TRJ >3 m⁄s (-0.41±2.10 L⁄min versus -0.36±1.93 L⁄min, respectively; P=0.87). In a multivariable analysis, the thermodilution-Fick difference increased with age (P=0.001). The presence of such discrepancy in 36% of patients evaluated for heart failure and⁄or heart transplant validated the results. In total, 37% of the 1315 procedures (213 performed by pulmonologists and 1102 performed by cardiologists) had a difference of >20% between thermodilution and Fick. Significant discrepancy exists between thermodilution and indirect Fick methods. This discrepancy potentially impacts pulmonary arterial hypertension prognostication and diagnosis, and is independent of TRJ.

Hemodynamic effects of fluid resuscitation with 6% hydroxyethyl starch and whole blood in experimental hypovolemic shock in Beagle dogs

The short-term effects of 6% hydroxyethyl starch (HES) and whole blood (WB) resuscitations in hypovolemic shock (HS) on invasive and noninvasive hemodynamic variables were studied from the clinical point of view in 20 mature healthy male Beagle dogs. After anesthesia, the animals were randomly divided into 2 groups, HES (n = 10) and WB (n = 10), and were surgically instrumented with an arterial catheter and a thermodilution cardiac output catheter. For induction of HS, the right carotid artery was catheterized and approximately 40% of the blood volume was drawn over a period of 30 min, until a mean arterial blood pressure (MAP) of about 50 mmHg was reached. After that, the HES group received 6% HES and the WB group received autologous whole blood resuscitation (30 mL/kg/h). The measurement of hemodynamic variables was performed in normovolemic (baseline, BL), severe hypovolemic, and resuscitation state (from R1 to R4 at an interval of 30 min). Significant changes in some of the hemodynamic variables systolic arterial pressure (SAP), diastolic arterial pressure (DAP), MAP, central venous pressure (CVP), cardiac output (CO), cardiac index (CI), stroke volume (SV), stroke volume index (SVI), oxygen delivery (DO_2), and oxygen consumption (VO_2) were observed during hypovolemic shock and resuscitation, which could reflect the condition of the patient. Resuscitation with WB seemed to resolve the hemodynamic variables to or above BL, whereas that with HES could resolve most but not all of the hemodynamic variables. The WB was found to be superior to restore the hemodynamic variable to the BL or above in comparison to that of the HES, for the clinical management of HS in dogs. The findings of this study suggest that dogs in HS can be successfully resuscitated with HES and WB.

Theoretical and model analysis of the unreliability of cardiac output measurement by means of the thermodilution method

Theoretical and model analysis of the unreliability of cardiac output measurement by means of the thermodilution methodThermodilution is the clinically most often applied method of cardiac output measurements. This method is based on thermal indicator (iced isotonic salt solution) variation measurements by a Swan-Ganz catheter located inside the pulmonary artery. The unreliability of thermodilution should be estimated theoretically because of the lack of references. In this paper an attempt has been made to estimate theoretically the unreliability of thermodilution cardiac output measurements.

Disagreement between pulse contour analysis and transpulmonary thermodilution for cardiac output monitoring after routine therapeutic interventions in ICU patients with acute circulatory failure

The present prospective study was aimed at assessing the reliability of the pulse contour method for measuring cardiac output (CO) after different routinely used therapeutic interventions that can influence vascular compliance and systemic vascular resistances in ICU patients (fluid challenges, changes in norepinephrine or dobutamine infusion rates and changes in ventilatory settings). In ICU patients requiring CO monitoring, transpulmonary thermodilution CO (COTD) and pulse contour CO (COPC) were measured with a PiCCO device after therapeutic manoeuvre-free periods (≤ and >1 h) and after therapeutic interventions without recalibration. Three hundred fifty-two sets of CO measurement pairs in 63 ICU patients were performed. The biases (and percentage errors) between COPC and COTD for the overall paired measurement, therapeutic manoeuvre-free periods and therapeutic manoeuvres were 0.20 ± 1.09 (33%), -0.01 ± 0.93 (29%) and 0.37 ± 1.18 (34%), respectively. The percentage errors were 36 and 39% for fluid challenges and changes in norepinephrine infusion rate, respectively. In ICU patients requiring therapeutic interventions, COPC is frequently in disagreement with COTD.

Predicting cardiac output responses to passive leg raising by a PEEP-induced increase in central venous pressure, in cardiac surgery patients

Changes in central venous pressure (CVP) rather than absolute values may be used to guide fluid therapy in critically ill patients undergoing mechanical ventilation. We conducted a study comparing the changes in the CVP produced by an increase in PEEP and stroke volume variation (SVV) as indicators of fluid responsiveness. Fluid responsiveness was assessed by the changes in cardiac output (CO) produced by passive leg raising (PLR). In 20 fully mechanically ventilated patients after cardiac surgery, PEEP was increased +10 cm H2O for 5 min followed by PLR. CVP, SVV, and thermodilution CO were measured before, during, and directly after the PEEP challenge and 30° PLR. The CO increase >7% upon PLR was used to define responders. Twenty patients were included; of whom, 10 responded to PLR. The increase in CO by PLR directly related (r=0.77, P<0.001) to the increase in CVP by PEEP. PLR responsiveness was predicted by the PEEP-induced increase in CVP [area under receiver-operating characteristic (AUROC) curve 0.99, P<0.001] and by baseline SVV (AUROC 0.90, P=0.003). The AUROC's for dCVP and SVV did not differ significantly (P=0.299). Our data in mechanically ventilated, cardiac surgery patients suggest that the newly defined parameter, PEEP-induced CVP changes, like SVV, appears to be a good parameter to predict fluid responsiveness.

Pulmonary arterial thermodilution, femoral arterial thermodilution and bioreactance cardiac output monitoring in a pediatric hemorrhagic hypovolemic shock model

AimBioreactance is a new non-invasive method for cardiac output measurement (NICOM). There are no studies that have analysed the utility of this technique in a pediatric animal model of hemorrhagic shock. MethodsA prospective study was performed using 9 immature Maryland pigs weighing 9 to 12kg was performed. A Swan-Ganz catheter, a PiCCO catheter and 4 dual surface electrodes were placed at the four corners of the anterior thoracic body surface. Shock was induced by withdrawing a blood volume of 30mL/kg, and then after, 30mL/kg of Normal saline was administered. Seven simultaneous measurements of cardiac index (CI) were made by pulmonary artery thermodilution (PATD), Femoral artery thermodilution (FATD), and NICOM before, during, and after hypovolaemia and during and after volume expansion. ResultsThe mean difference (bias) of differences (limits of agreement) between PATD and FATD was 0.84 (−1.87–3.51)L/min/1.77m2, between PATD and NICOM was 1.95 (−1.79–5.69)L/min/1.77m2, and between FATD and NICOM was 1.06 (−1.40–3.52)L/min/1.77m2. A moderate correlation was found between PATD and FATD (r=0.43; P=0.01), but no correlation was found between bioreactance and either PATD or FATD. Hypovolemia and volume expansion produced important significant differences in CI as measured by PATD and FATD, while the changes with bioreactance were small and non significant. ConclusionsPATD and FATD measurements showed similar responses to hypovolemic shock and volume expansion. Bioreactance persistently underestimates the CI and is not significantly altered by either inducing hemorrhagic shock, or later, through volume expansion. Bioreactance is not a suitable method for monitoring the CI in pediatric hemorrhagic shock.

Haemodynamic response to abdominal decompression in acute Budd–Chiari syndrome

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome commonly occur in patients with liver disease. We compared haemodynamic variables pre- and post-abdominal decompression in patients with acute Budd-Chiari syndrome (BCS) and patients with chronic liver disease (CLD), ascites and IAH. Patients with IAH admitted to the Liver ICU, King's College Hospital were studied. Transpulmonary thermodilution cardiac output (CO) monitoring was performed with the PiCCO(®) system. Ten patients with decompensated BCS (median age 39 years, 20-52) and eight patients with CLD (59 years, 33-65) and tense ascites requiring paracentesis were studied. Intra-abdominal pressure (IAP) was raised in both groups pre-intervention (BSC 23 mmHg, 17-40; CLD 26, 20-40). Intrathoracic blood volume (ITBVI) was persistently low in the BCS group (632 ml/m(2) , 453-924) despite volume resuscitation. Post-intervention, reduction in IAP was noted in both groups (BCS P<0.001, CLD P<0.0001). The ITBVI increased (P=0.001) in the BCS group only. An increase in cardiac index (CI) and stroke volume index (SVI) was noted in both groups (BCS: CI P=0.003, SVI: P=0.007; CLD: CI P=0.005, SVI P=0.02). The central venous pressure did not change in either group and did not correlate with markers of flow (CI, SVI) or IAP. Both groups demonstrated an inverse relationship between IAP, CI and SVI. Patients with BCS and IAH have evidence of central hypovolaemia. In addition to raised IAP, hepatic venous obstruction and caudate lobe hypertrophy limit venous return in patients with BCS. Reduction in IAP and re-establishment of caval flow restores preload with improvement in CO.

Arterial pressure allows monitoring the changes in cardiac output induced by volume expansion but not by norepinephrine*

To evaluate to which extent the systemic arterial pulse pressure could be used as a surrogate of cardiac output for assessing the effects of a fluid challenge and of norepinephrine. Observational study. Medical intensive care unit. Patients with an acute circulatory failure who received a fluid challenge (228 patients, group 1) or in whom norepinephrine was introduced or increased (145 patients, group 2). We measured the systolic, diastolic, and mean arterial pressure, pulse pressure, and the transpulmonary thermodilution cardiac output before and after the therapeutic interventions. In group 1, the fluid challenge significantly increased cardiac output by 24% ± 25%. It significantly increased cardiac output by ≥15% (+35% ± 27%) in 142 patients ("responders"). The fluid-induced changes in cardiac output were correlated with the changes in pulse pressure (r = .56, p < .0001), systolic arterial pressure (r = .55, p < .0001), diastolic arterial pressure (r = .37, p < .0001), and mean arterial pressure (r = .52, p < .0001). At multivariate analysis, changes in pulse pressure were significantly related to changes in stroke volume (multiple r = .52) and to age (r = .12). A fluid-induced increase in pulse pressure of ≥17% allowed detecting a fluid-induced increase in cardiac output of ≥15% with a sensitivity of 65[56-72]% and a specificity of 85[76-92]%. The area under the receiver operating characteristic curves for the fluid-induced changes in mean arterial pressure and in diastolic arterial pressure was significantly lower than for pulse pressure. In group 2, the introduction/increase of norepinephrine significantly increased cardiac output by 14% ± 18%. The changes in cardiac output induced by the introduction/increase in the dose of norepinephrine were correlated with the changes in pulse pressure and systolic arterial pressure (r = .21 and .29, respectively, p = .001) but to a significantly lesser extent than in group 1. Pulse pressure and systolic arterial pressure could be used for detecting the fluid-induced changes in cardiac output, in spite of a significant proportion of false-negative cases. By contrast, the changes in pulse pressure and systolic arterial pressure were unable to detect the changes in cardiac output induced by norepinephrine.

Performance of cardiac output measurement derived from arterial pressure waveform analysis in patients requiring high-dose vasopressor therapy

Arterial pressure waveform analysis of cardiac output (APCO) without external calibration (FloTrac/Vigileo™) is critically dependent upon computation of vascular tone that has necessitated several refinements of the underlying software algorithms. We hypothesized that changes in vascular tone induced by high-dose vasopressor therapy affect the accuracy of APCO measurements independently of the FloTrac software version. In this prospective observational study, we assessed the validity of uncalibrated APCO measurements compared with transpulmonary thermodilution cardiac output (TPCO) measurements in 24 patients undergoing vasopressor therapy for the treatment of cerebral vasospasm after subarachnoid haemorrhage. Patients received vasoactive support with [mean (sd)] 0.53 (0.46) µg kg(-1) min(-1) norepinephrine resulting in mean arterial pressure of 104 (14) mm Hg and mean systemic vascular resistance of 943 (248) dyn s(-1) cm(-5). Cardiac output (CO) data pairs (158) were obtained simultaneously by APCO and TPCO measurements. TPCO ranged from 5.2 to 14.3 litre min(-1), and APCO from 4.1 to 13.7 litre min(-1). Bias and limits of agreement were 0.9 and 2.5 litre min(-1), resulting in an overall percentage error of 29.6% for 68 data pairs analysed with the second-generation FloTrac(®) software and 27.9% for 90 data pairs analysed with the third-generation software. Precision of the reference technique was 2.6%, while APCO measurements yielded a precision of 29.5% and 27.9% for the second- and the third-generation software, respectively. For both software versions, bias (TPCO-APCO) correlated inversely with systemic vascular resistance. In neurosurgical patients requiring high-dose vasopressor support, precision of uncalibrated CO measurements depended on systemic vascular resistance. Introduction of the third software algorithm did not improve the insufficient precision (>20%) for APCO measurements observed with the second software version.