Lack of agreement between bioimpedance and continuous thermodilution measurement of cardiac output in intensive care unit patients

BACKGROUND: Bolus thermodilution is the standard bedside method of cardiac output measurement in the intensive care unit (ICU). The Baxter Vigilance monitor uses a modified thermodilution pulmonary artery catheter with a thermal filament to give a continuous read-out of cardiac output. This has been shown to correlate very well with both the 'gold standard' dye dilution method and the bolus thermodilution method. Bioimpedance cardiography using the Bomed NCCOM 3 offers a noninvasive means of continuous cardiac output measurement and has been shown to correlate with the bolus thermodilution method. We investigated the agreement between the continuous bioimpedance and continuous thermodilution methods, enabling acquisition of a large number of simultaneous measurements. RESULTS: A total of 2390 paired data points from seven patients were collected. There was no correlation (r2 = 0.01) between the methods. The precision (1.16 l/min/m2) of agreement between the Vigilance and the Bomed, assessed by the Bland-Altam method, was very poor although the bias (-0.16 l/min/m2) appeared fair. CONCLUSIONS: The Bomed NCCOM 3 bioimpedance monitor shows poor agreement with the Baxter Vigilance continuous thermodilution monitor in a group of general ICU patients and cannot be recommended for cardiac output monitoring in this situation.     

脉搏轮廓温度稀释连续心排血量监测的护理

脉搏轮廓温度稀释连续心排量测定技术(PiCCO)是一项全新的脉搏轮廓连续心排血量与经肺温度稀释心排血量联合应用技术,可以监测常规血流动力学参数,也可检测容量变化反映的心脏前负荷以及肺血管通透性的参数变化,可有效地指导临床     

Comparison between ultrasonic and thermodilution cardiac output measurements in intensive care patients

The reliability of ultrasonic cardiac output measurement was assessed using a commercial device that combines A-mode aortic root diameter determination and continuous wave (CW) Doppler flow velocity measurement in the ascending aorta. We compared this method with thermodilution (TD) cardiac output in 41 intensive care patients. Aortic root diameter measurement with A-mode was not possible in four (10%) patients. Using strictly defined criteria based upon our initial experience, we could not obtain acceptable CW Doppler flow signals in nine (22%) patients. Thus, ultrasonic cardiac output measurement was possible in 28 (68%) patients in whom there was an excellent correlation with cardiac output (r = 0.97; p less than .001). This study demonstrates that the transcutaneous CW Doppler method for measuring cardiac output is accurate and reliable in a limited percentage of ICU patients. Combining the CW Doppler with B-mode echocardiogram increases the applicability when an A-mode measurement is not possible.     

Continuous cardiac output by femoral arterial thermodilution calibrated pulse contour analysis: comparison with pulmonary arterial thermodilution

OBJECTIVE: To compare two thermodilution methods for the determination of cardiac output (CO)-thermodilution in the pulmonary artery (COpa) and thermodilution in the femoral artery (COa)-with each other and with CO determined by continuous pulse contour analysis (COpc) in terms of reproducibility, bias, and correlation among the different methods. Good agreement between the methods would indicate the potential of pulse contour analysis to monitor CO continuously and at reduced invasiveness. DESIGN: Prospective criterion standard study. SETTING: Cardiac surgical intensive care unit in a university hospital. PATIENTS: Twenty-four postoperative cardiac surgery patients. INTERVENTIONS: Without interfering with standard hospital cardiac recovery procedures, changes in CO as a result of the postsurgical course, administration of vasoactive substances, and/or fluid administration were recorded. CO was first recorded after a 1-hr stabilization period in the intensive care unit and hourly thereafter for 6 hrs, and by subsequent determinations at 9, 12, and 24 hrs. MEASUREMENTS AND MAIN RESULTS: There were 216 simultaneous determinations of COpa, COa, and COpc. COpc was initially calibrated using COa, and no further recalibration of COpc was performed. COpa ranged from 3.0 to 11.8 L/min, and systemic vascular resistance ranged from 252 to 2434 dyne x sec/cm5. The mean difference (bias) +/-2 SD of differences (limits of agreement) was -0.29+/-1.31 L/min for COpa vs. COa, 0.07+/-1.4 L/min for COpc vs. COpa, and -0.22+/-1.58 L/min for COpc vs. COa. In all but four patients COpc correlated with COa after the initial calibration. Correlation and precision of COpc vs. COa was stable for 24 hrs. CONCLUSIONS: Femoral artery pulse contour CO correlates well with both COpa and COa even during substantial variations in vascular tone and hemodynamics. Additionally, CO determined by arterial thermodilution correlates well with COpa. Thus, COa can be used to calibrate COpc.     

Lack of agreement between thermodilution and electrical velocimetry cardiac output measurements

Objective

The modified algorithm for the non-invasive determination of cardiac output (CO) by electrical bioimpedance—electrical velocimetry (EV^®)—has been reported to give reliable results in comparison with echocardiography and pulmonary arterial thermodilution (PA-TD) in patients either before or after cardiac surgery. The present study was designed to determine whether EV^®-CO measurements reflect intraindividual changes in CO during cardiac surgery.

Design

Prospective, observational study.

Setting

Operating room (OR) and intensive care unit (ICU) of a university hospital.

Patients

Twenty-nine patients undergoing elective cardiac surgery.

Interventions

None.

Measurements

CO was determined simultaneously by PA-TD and EV^® after induction of anesthesia (t1) and 4.9?±?3.5?h after ICU admission (t2).

Results

TD-CO was 3.9?±?1.4 and 5.4?±?1.1 l/min at t1 and t2 (?p?®-CO was 4.3?±?1.1 and 4.9?±?1.5 l/min at t1 and t2 (?p?=?0.013). Bland–Altman analysis showed a bias of ?0.4 l/min and 0.4 l/min and a precision of 3.2 and 3.6 l/min (34.3% and 67.4%) at t1 and t2, respectively. Analysis of the individual pre- to postoperative changes in CO with both methods revealed bidirectional changes in n?=?12 patients and unidirectional changes with a difference greater than 50% and less than 50% in n?=?9 and n?=?8 patients, respectively.

Conclusions

The disagreement between PA-TD and EV^®-CO measurements after anesthesia induction and after ICU admission, as well as the fact that thoracic bioimpedance did not adequately reflect pre- to postoperative changes in CO, questions the reliability of EV^®-CO measurements in cardiac surgery patients and contrasts sharply with previous studies.

     

Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with thermodilution cardiac output measurements

Introduction  

Cardiac output (CO) monitoring is indicated only in selected patients. In cardiac surgical patients, perioperative haemodynamic management is often guided by CO measurement by pulmonary artery catheterisation (CO_PAC). Alternative strategies of CO determination have become increasingly accepted in clinical practice because the benefit of guiding therapy by data derived from the PAC remains to be proven and less invasive alternatives are available. Recently, a device offering uncalibrated CO measurement by arterial waveform analysis (CO_Wave) was introduced. As far as this approach is concerned, however, the validity of the CO measurements obtained is utterly unclear. Therefore, the aim of this study was to compare the bias and the limits of agreement (LOAs) (two standard deviations) of CO_Wave at four specified time points prior, during, and after coronary artery bypass graft (CABG) surgery with a simultaneous measurement of the gold standard CO_PAC and aortic transpulmonary thermodilution CO (CO_Transpulm).     

Continuous cardiac output monitoring with pulse contour analysis: a comparison with lithium indicator dilution cardiac output measurement

OBJECTIVE: Pulse contour analysis can be used to provide beat-to-beat cardiac output (CO) measurement. The current study sought to evaluate this technique by comparing its results with lithium dilution CO (LiCO) measurements. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit. PATIENTS: Twenty-two patients after cardiac or major noncardiac surgery. MEASUREMENTS: After initial calibration of the pulse contour CO (PCO) method, CO was measured by PCO and by LiCO methods at 4, 8, 16, and 24 hrs. Recalibration of PCO was performed every 8 hrs. The systemic vascular resistance and dynamic response characteristics of the arterial catheter-transducer system were measured at each time point to determine whether these influenced the agreement between PCO and LiCO methods. MAIN RESULTS: There was an excellent correlation between methods (r = .94). Bias was small (-0.005 L/min), and clinically acceptable limits of agreement were demonstrated between techniques. Although many catheter-transducer systems had poor dynamic response characteristics, this did not influence the level of agreement between the two techniques. An increase in systemic vascular resistance between two time points did tend to cause overestimation of LiCO by the PCO. CONCLUSIONS: PCO measurement compared well with the lithium dilution method and can be considered an accurate technique for measuring beat-to-beat CO with limited risk to the patient.     

Cardiac output measured by lithium dilution and transpulmonary thermodilution in patients in a paediatric intensive care unit

Objective: To compare the results of cardiac output measurements obtained by lithium dilution and transpulmonary thermodilution in paediatric patients. Design: A prospective study.¶Setting: Paediatric intensive care unit in a university teaching hospital.¶Patients: Twenty patients (age 5 days–9 years; weight 2.6–28.2 kg) were studied.¶Interventions: Between two and four comparisons of lithium dilution cardiac output (LiDCO) and transpulmonary thermodilution (TPCO) were made in each patient.¶Measurements and results: Results from three patients were excluded: in one patient there was an unsuspected right-to-left shunt, in two patients there was a problem with blood sampling through the lithium sensor. There were 48 comparisons of LiDCO and TPCO in the remaining 17 patients over a range of 0.4–6 l/min. The mean of the differences (LiDCO–TPCO) was –0.1 ± 0.3 (SD) l/min. Linear regression analysis gave LiDCO = 0.11 + 0.90 × TPCO l/min (r ² = 0.96). There were no adverse effects in any patient.¶Conclusions: These results suggest that the LiDCO method can be used to provide safe and accurate measurement of cardiac output in paediatric patients. The method is simple and quick to perform, requiring only arterial and venous catheters, which will already have been inserted for other reasons in these patients.     

Two-beam pulsed Doppler cardiac output measurement: reproducibility and agreement with thermodilution

Two observers used two-beam pulsed Doppler ultrasound, equipped with a suprasternal probe, to measure cardiac output (QtDopp) in 38 ICU patients who had pulmonary artery catheters and in 20 adult volunteers. The two-beam pulsed Doppler method enables one device to measure simultaneously both aortic blood velocity and aortic diameter. Each observer was blind to the other's measurement and to the thermodilution cardiac output measurement (Qttd). Linear regression of the mean of both observer's QtDopp on Qttd showed QtDopp = 0.90.Qttd + 0.01 (see = 1.54 L/min, r = .90). Bias (+/- SD), defined as mean (QtDopp - Qttd) difference, was -0.69 +/- 1.55 L/min. Interobserver agreement was more variable in patients than volunteers; mean (observer 1 - observer 2) difference was 0.14 +/- 1.30 L/min in ICU patients and -0.09 +/- 0.92 L/min in volunteers. Two-beam pulsed Doppler ultrasound is a simpler method of measuring QtDopp than previous pulsed Doppler methods which measure separately the aortic diameter by echocardiography. Although its agreement with Qttd is close to other Doppler methods and has acceptable interobserver reproducibility, its accuracy remains operator-dependent.     

Comparison of dynamic measurements of pulse contour with pulsed heat continuous cardiac output in postoperative cardiac surgical patients.

Cardiac output (CO) can be measured using bolus thermodilution via a pulmonary artery catheter (PAC) and as continuous cardiac output (CCO), using pulsed heat thermoditution. Pulse contour cardiac output (PCCO) measures continuous CO by analysis of the arterial waveform after calibration with thermodilution CO. The Pulsion Medical Systems (PiCCO system) achieves this by transpulmonary aortic thermodilution (TDtpa). There is uncertainty regarding the agreement between TDtpa, CCO, and PCCO CO measurements in situations of rapid haemodynamic changes. We studied the agreement of the measures by comparing digital recordings of cardiac index (CI) determined by PCCO and CCO (PCCI and CCI, respectively) made during periods of haemodynamic instability. After ethics committee approval we studied four post-coronary artery bypass graft patients, in the immediate postoperative period. Each patient had a 7.5F CCO catheter (Edwards Lifesciences) and a 5F, 20cm PCCO femoral artery catheter. Digital recordings were obtained for the first 12-18 postoperative hours. Six epochs of instability were identified in the first two to three postoperative hours, and at the commencement of inotropic or vasoactive drugs. Notable features, despite frequent PCCO calibrations, were the marked difference of PCCI compared to CCI. In contradistinction, they tracked very closely during a period of stability. Limitations of both methods were noted. Whilst PCCO responded to rapid change, it developed significant error during haemodynmamic instability and requires frequent recalibration. CCO on the other hand has a considerable time lag in responding to changes in CO. The way a monitor measures CO must be taken into account when using the data in clinical management.     

The clinical application of pulse contour cardiac output and intrathoracic volume measurements in critically ill patients.

Cardiac output (CO) determination by pulmonary artery (PA) catheter has increasingly been criticised within the literature due to its invasive nature and poor correlation between the pressure measurements and intravascular volume status in mechanically ventilated patients. Consequently, alternative less invasive technologies to PA catheterisation are emerging within intensive care. One such novel technology are pulse contour CO (PCCO) systems. They establish comprehensive and continuous haemodynamic monitoring utilising a central venous catheter (CVC) and an arterial line. Furthermore, a key feature of this technology is its ability to produce intrathoracic volume measurements which may provide a better estimation of cardiac preload as well as indicate the presence and severity of pulmonary oedema. This article aims to discuss the theoretical basis and clinical application of PCCO systems, how PCCO systems differ from PA catheters and how the intrathoracic volume measurements are derived. Understanding these advanced concepts will ensure that clinicians are able to employ this innovative monitoring technology more effectively.     

Estimated continuous cardiac output based on pulse wave transit time in off-pump coronary artery bypass grafting: a comparison with transpulmonary thermodilution

To evaluate the accuracy of estimated continuous cardiac output (esCCO) based on pulse wave transit time in comparison with cardiac output (CO) assessed by transpulmonary thermodilution (TPTD) in off-pump coronary artery bypass grafting (OPCAB). We calibrated the esCCO system with non-invasive (Part 1) and invasive (Part 2) blood pressure and compared with TPTD measurements. We performed parallel measurements of CO with both techniques and assessed the accuracy and precision of individual CO values and agreement of trends of changes perioperatively (Part 1) and postoperatively (Part 2). A Bland–Altman analysis revealed a bias between non-invasive esCCO and TPTD of 0.9 L/min and limits of agreement of ±2.8 L/min. Intraoperative bias was 1.2 L/min with limits of agreement of ±2.9 L/min and percentage error (PE) of 64 %. Postoperatively, bias was 0.4 L/min, limits of agreement of ±2.3 L/min and PE of 41 %. A Bland–Altman analysis of invasive esCCO and TPTD after OPCAB found bias of 0.3 L/min with limits of agreement of ±2.1 L/min and PE of 40 %. A 4-quadrant plot analysis of non-invasive esCCO versus TPTD revealed overall, intraoperative and postoperative concordance rate of 76, 65, and 89 %, respectively. The analysis of trending ability of invasive esCCO after OPCAB revealed concordance rate of 73 %. During OPCAB, esCCO demonstrated poor accuracy, precision and trending ability compared to TPTD. Postoperatively, non-invasive esCCO showed better agreement with TPTD. However, invasive calibration of esCCO did not improve the accuracy and precision and the trending ability of method.     

Effects of intermittent positive-pressure ventilation on cardiac output measurements by thermodilution

Sequential thermodilution measurements of cardiac output in mechanically ventilated patients undergoing cardiac surgery demonstrated a cyclic modulation which correlated with changes in airway pressure, and was not affected by opening the pericardium. There was no satisfactory point for single measurements, which suggests that random thermodilution measurements of cardiac output during intermittent positive-pressure ventilation should be avoided, even when triplicate measurements are performed. To estimate the mean cardiac output, at least two measurements should be made at predetermined points of the ventilatory cycle. We recommend paired measurements at midinspiration and end-expiration.     

Reproducibility of transpulmonary thermodilution cardiac output measurements in clinical practice: a systematic review

Measuring cardiac output (CO) is an integral part of the diagnostic and therapeutic strategy in critically ill patients. During the last decade, the single transpulmonary thermodilution (TPTD) technique was implemented in clinical practice. The purpose of this paper was to systematically review and critically assess the existing data concerning the reproducibility of CO measured using TPTD (COTPTD). A total of 16 studies were identified to potentially be included in our study because these studies had the required information that allowed for calculating the reproducibility of COTPTD measurements. 14 adult studies and 2 pediatric studies were analyzed. In total, 3432 averaged CO values in the adult population and 78 averaged CO values in the pediatric population were analyzed. The overall reproducibility of COTPTD measurements was 6.1 ± 2.0 % in the adult studies and 3.9 ± 2.9 % in the pediatric studies. An average of 3 boluses was necessary for obtaining a mean CO value. Achieving more than 3 boluses did not improve reproducibility; however, achieving less than 3 boluses significantly affects the reproducibility of this technique. The present results emphasize that TPTD is a highly reproducible technique for monitoring CO in critically ill patients, especially in the pediatric population. Our findings suggest that obtaining a mean of 3 measurements for determining CO values is recommended.     

Effects of injectate volume on thermodilution measurements of cardiac output in patients with low ventricular ejection fraction.

OBJECTIVE: To determine the effect of 5-mL injectate on cardiac output measurements in critically ill patients with low ventricular ejection fraction (< 35%). METHODS: Thermodilution cardiac output measurements obtained with three 5-mL and three 10-mL (randomly ordered) iced injectates in 50 patients with low ejection fraction were averaged if the measurements were within 10% of the median. If the 3 measurements were not within those limits, additional measurements were obtained. RESULTS: Cardiac output measured with the 5-mL injectate (mean, 4.63 L/min) and cardiac output measured with the 10-mL injectate (mean, 4.52 L/min) were not significantly different (P = .64). Lower and upper limits of agreement were -1.7 L/min to +1.6 L/min. The bias (mean difference between 10- and 5-mL measurements) of all measurements was -0.09, and the precision was 1.43 L/min, with a 95% confidence limit (mean difference +/- 2 SD) of -1.7 to +1.6 L/min. An additional measurement was necessary in 77% of patients in the 5-mL group but in only 48% of the 10-mL group (P = .006). CONCLUSIONS: Cardiac outputs measured with 5- and 10-mL injectates do not differ significantly. The greater variability of measurements obtained with a 5-mL injectate suggests that more measurements, and thus more time, are needed to measure cardiac output accurately. Clinicians must weigh the benefit of minimizing fluid volume used against the potential decreased reliability of cardiac output measurements.     

Outcome of cardiac surgery patients with complicated intensive care unit stay

Risk stratification has become an essential element in the practice of cardiac surgery. Several studies have identified preoperative risk factors for adverse outcome. However, outcome is mostly defined by 30-day mortality and morbidity. These data reflect poorly the benefit for the patient. Long-term survival, quality of life, and functional status should be included in a more global analysis of the outcome, particularly in patients with complicated ICU stay. By reviewing the recent data reported in the literature, we can identify a number of preoperative predictive factors for complicated ICU stay, including advanced age, chronic obstructive pulmonary disease, preoperative low ejection fraction, previous myocardial infarction, reoperation, renal failure, combined surgery (coronary artery bypass grafting plus valve surgery), low hematocrit, and neurologic impairment. Short- and long-term outcomes are dependent on the type of postoperative complication. Unfortunately, data regarding the long-term outcome in these situations are very scarce.     

Comparison of cardiac output measures by transpulmonary thermodilution,pulse contour analysis,and pulmonary artery thermodilution during off-pump coronary artery bypass surgery: a subgroup analysis of the cardiovascular anaesthesia registry at a single tertiary centre

Cardiac output measurement has a long history in haemodynamic management and many devices are now available with varying levels of accuracy. The purpose of the study was to compare the agreement and trending abilities of cardiac output, as measured by transpulmonary thermodilution and calibrated pulse contour analysis, using the VolumeView? system, continuous thermodilution via a pulmonary artery catheter, and uncalibrated pulse contour analysis, using FloTrac? with pulmonary artery bolus thermodilution. Twenty patients undergoing off-pump coronary artery bypass surgery using a pulmonary artery catheter and the VolumeView? and FloTrac? systems were included in this subgroup analysis of the cardiovascular anaesthesia registry at a single tertiary centre. During surgery, cardiac output was assessed after the induction of anaesthesia, after sternotomy, during the harvesting of grafts, during revascularization of the anterior and posterior/lateral wall, after protamine infusion, and after sternal fixation. In total, 145 sets of measurements were evaluated using Bland–Altman with % error calculation, correlation, concordance, and polar plot analyses. The percentage error (bias, limits of agreement) was 12.6 % (?0.12, ?0.64 to 0.41 L/min), 26.7 % (?0.38, ?1.50 to 0.74 L/min), 29.3 % (?0.08, ?1.32 to 1.15 L/min), and 33.8 % (?0.05, ?1.47 to 1.37 L/min) for transpulmonary thermodilution, pulmonary artery continuous thermodilution, calibrated, and uncalibrated pulse contour analysis, respectively, compared with pulmonary artery bolus thermodilution. All pairs of measurements showed significant correlations (p < 0.001), whereas only transpulmonary thermodilution revealed trending ability (concordance rate of 95.1 %, angular bias of 1.33°, and radial limits of agreement of 28.71°) compared with pulmonary artery bolus thermodilution. Transpulmonary thermodilution using the VolumeView? system provides reliable data on cardiac output measurement and tracking the changes thereof when compared with pulmonary artery bolus thermodilution in patients with preserved cardiac function during off-pump coronary artery bypass surgery. Trial registration NCT01713192 (ClinicalTrials.gov).