Bolus Thermodilution Technique Research Articles

Reliability of bioreactance and pulse power analysis in measuring cardiac index during cytoreductive abdominal surgery with hyperthermic intraperitoneal chemotherapy (HIPEC)

PurposeVarious malignancies with peritoneal carcinomatosis are treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC). The hemodynamic instability resulting from fluid balance alterations during the procedure necessitates reliable hemodynamic monitoring. The aim of the study was to compare the accuracy, precision and trending ability of two less invasive hemodynamic monitors, bioreactance-based Starling SV and pulse power device LiDCOrapid with bolus thermodilution technique with pulmonary artery catheter in the setting of cytoreductive surgery with HIPEC.MethodsThirty-one patients scheduled for cytoreductive surgery were recruited. Twenty-three of them proceeded to HIPEC and were included to the study. Altogether 439 and 430 intraoperative bolus thermodilution injections were compared to simultaneous cardiac index readings obtained with Starling SV and LiDCOrapid, respectively. Bland-Altman method, four-quadrant plots and error grids were used to assess the agreement of the devices.ResultsComparing Starling SV with bolus thermodilution, the bias was acceptable (0.13 l min− 1 m− 2, 95% CI 0.05 to 0.20), but the limits of agreement were wide (− 1.55 to 1.71 l min− 1 m− 2) and the percentage error was high (60.0%). Comparing LiDCOrapid with bolus thermodilution, the bias was acceptable (− 0.26 l min− 1 m− 2, 95% CI − 0.34 to − 0.18), but the limits of agreement were wide (− 1.99 to 1.39 l min− 1 m− 2) and the percentage error was high (57.1%). Trending ability was inadequate with both devices.ConclusionStarling SV and LiDCOrapid were not interchangeable with bolus thermodilution technique limiting their usefulness in the setting of cytoreductive surgery with HIPEC.

RELIABILITY OF BIOREACTANCE AND PULSE POWER ANALYSIS IN MEASURING CARDIAC INDEX DURING OPEN ABDOMINAL AORTIC SURGERY

<h3>Objective</h3> Pulmonary artery catheter (PAC) is considered as the gold standard for measuring cardiac output, but less invasive monitors have recently been developed. We compared the accuracy, precision and trending ability of non-invasive bioreactance-based Starling SV and mini-invasive pulse power device LiDCOrapid to bolus thermodilution technique with pulmonary artery catheter (TDCO) when measuring cardiac index (CI) in the setting of open abdominal aortic surgery. <h3>Design and Methods</h3> Forty-one patients undergoing open abdominal aortic surgery were monitored with Starling SV, LiDCOrapid and TDCO during surgery, resulting in 627 simultaneous CI measurements. We used the Bland-Altman method and percentage error to investigate the agreement between the devices and four-quadrant plots with error grids to assess the trending ability. <h3>Results</h3> The agreement between TDCO and Starling SV was associated with a bias of 0.18 L/min/m2 (95% confidence interval, 95% CI 0.13 to 0.23), wide limits of agreement (LOA, -1.12 to 1.47 L/min/m2) and a percentage error (PE) of 63.7 (95% CI 52.4-71.0). (Figure 1a) The agreement between TDCO and LiDCOrapid was associated with a bias of -0.15 L/min/m2 (95% CI -0.21 to -0.09), wide LOA (-1.56 to 1.37) and PE of 68.7 (95% CI 54.9-79.6). (Figure 1b) Trending abilities were not acceptable, since with Starling SV only 33.6% and with LiDCOrapid only 41.2 % of the measurements changed in the same direction to the same extent as with TDCO. <h3>Conclusions</h3> CI measurements with Starling SV and LiDCOrapid were not interchangeable with TDCO, and their ability to track changes in CI was poor. These results do not support their use in monitoring CI reliably during open abdominal aortic surgery.

Reliability of Bioreactance and Pulse-Power Analysis in Measuring Cardiac Index in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

Less-invasive and continuous cardiac output monitors recently have been developed to monitor patient hemodynamics. The aim of this study was to compare the accuracy, precision, and trending ability of noninvasive bioreactance-based Starling SV and miniinvasive pulse-power device LiDCOrapid to bolus thermodilution technique with a pulmonary artery catheter (TDCO) when measuring cardiac index in the setting of cardiac surgery with cardiopulmonary bypass (CPB). A prospective method-comparison study. Oulu University Hospital, Finland. Twenty patients undergoing cardiac surgery with CPB. Cardiac index measurements were obtained simultaneously with TDCO intraoperatively and postoperatively, resulting in 498 measurements with Starling SV and 444 with LiDCOrapid. The authors used the Bland-Altman method to investigate the agreement between the devices and four-quadrant plots with error grids to assess the trending ability. The agreement between TDCO and Starling SV was qualified with a bias of 0.43 L/min/m2 (95% confidence interval [CI], 0.37-0.50), wide limits of agreement (LOA, -1.07 to 1.94 L/min/m2), and a percentage error (PE) of 66.3%. The agreement between TDCO and LiDCOrapid was qualified, with a bias of 0.22 L/min/m2 (95% CI 0.16-0.27), wide LOA (-0.93 to 1.43), and a PE of 53.2%. With both devices, trending ability was insufficient. The reliability of bioreactance-based Starling SV and pulse-power analyzer LiDCOrapid was not interchangeable with TDCO, thus limiting their usefulness in cardiac surgery with CPB.

Bioreactance and fourth-generation pulse contour methods in monitoring cardiac index during off-pump coronary artery bypass surgery

The pulmonary artery catheter (PAC) is considered the gold standard for cardiac index monitoring. Recently new and less invasive methods to assess cardiac performance have been developed. The aim of our study was to assess the reliability of a non-invasive monitor utilizing bioreactance (Starling SV) and a non-calibrated mini-invasive pulse contour device (FloTrac/EV1000, fourth-generation software) compared to bolus thermodilution technique with PAC (TDCO) during off-pump coronary artery bypass surgery (OPCAB). In this prospective study, 579 simultaneous intra- and postoperative cardiac index measurements obtained with Starling SV, FloTrac/EV1000 and TDCO were compared in 20 patients undergoing OPCAB. The agreement of data was investigated by Bland–Altman plots, while trending ability was assessed by four-quadrant plots with error grids. In comparison with TDCO, Starling SV was associated with a bias of 0.13 L min−1 m−2 (95% confidence interval, 95% CI, 0.07 to 0.18), wide limits of agreement (LOA, − 1.23 to 1.51 L min−1 m−2), a percentage error (PE) of 60.7%, and poor trending ability. In comparison with TDCO, FloTrac was associated with a bias of 0.01 L min−1 m−2 (95% CI − 0.05 to 0.06), wide LOA (− 1.27 to 1.29 L min−1 m−2), a PE of 56.8% and poor trending ability. Both Starling SV and fourth-generation FloTrac showed acceptable mean bias but imprecision due to wide LOA and high PE, and poor trending ability. These findings indicate limited reliability in monitoring cardiac index in patients undergoing OPCAB.

Evaluation of cardiac output by 5 arterial pulse contour techniques using trend interchangeability method.

Cardiac output measurement with pulse contour analysis is a continuous, mini-invasive, operator-independent, widely used, and cost-effective technique, which could be helpful to assess changes in cardiac output. The 4-quadrant plot and the polar plot have been described to compare the changes between 2 measurements performed under different conditions, and the direction of change by using different methods of measurements. However, the 4-quadrant plot and the polar plot present a number of limitations, with a risk of misinterpretation in routine clinical practice. We describe a new trend interchangeability method designed to objectively define the interchangeability of each change of a variable. Using the repeatability of the reference method, we classified each change as either uninterpretable or interpretable and then as either noninterchangeable, in the gray zone or interchangeable. An interchangeability rate can then be calculated by the number of interchangeable changes divided by the total number of interpretable changes. In this observational study, we used this objective method to assess cardiac output changes with 5 arterial pulse contour techniques (Wesseling's method, LiDCO, PiCCO, Hemac method, and Modelflow) in comparison with bolus thermodilution technique as reference method in 24 cardiac surgery patients. A total of 172 cardiac output variations were available from the 199 data points: 88 (51%) were uninterpretable, according to the first step of the method. The second step of the method, based on the 84 (49%) interpretable variations, showed that only 18 (21%) to 30 (36%) variations were interchangeable regardless of the technique used. None of pulse contour cardiac output technique could be interchangeable with bolus thermodilution to assess changes in cardiac output using the trend interchangeability method in cardiac surgery patients. Future studies may consider using this method to assess interchangeability of changes between different methods of measurements.

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

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

Uncalibrated arterial pressure waveform analysis for cardiac output monitoring is biased by low peripheral resistance in patients with intracranial haemorrhage

Cardiac output (CO) monitoring by uncalibrated arterial pressure waveform analysis (APCO) using the FloTrac/Vigileo™ is feasible in patients with intracranial haemorrhage, but the results of validation studies are contradictory. The aim of the present study was to analyse the clinical agreement between the intermittent bolus thermodilution technique (TDCO) and APCO in patients with non-traumatic intracranial haemorrhage. This was a prospective observational clinical study in a university level intensive care unit. We studied patients who underwent CO monitoring according to clinical indications using TDCO. Simultaneously, APCO was applied using the radial arterial pressure curve. The difference in CO values measured by APCO with a mid-chest calibration level was compared with a calibration level at the angle of the eye. A total of 407 data pairs from 16 patients were obtained. The mean CO(TDCO) was 7.6 litre min(-1) and CO(APCO) was 6.0 litre min(-1), with a bias corrected for repeated measures of 1.5 litre min(-1) and 95% limits of agreement of -2.4 to 5.4 litre min(-1). The percentage error was 58%. The increasing bias correlated with low peripheral resistance (ρ=-0.53, P=0.036). The calibration level at the patient's eye angle did not affect CO values (median bias 0 litre min(-1) with 25th-75th percentile -0.1 to 0.2 litre min(-1)). The second generation of FloTrac(®)/Vigileo(®) monitoring system underestimates the TDCO in patients with non-traumatic intracranial haemorrhage. The bias correlates with measured systemic vascular resistance. The upper calibration level does not affect the results.

Validity of an Arterial Pressure Waveform Analysis Device: Does the Puncture Site Play a Role in the Agreement With Intermittent Pulmonary Artery Catheter Thermodilution Measurements?

The measurement of cardiac output is a key element in the assessment of cardiac function. Recently, a pulse contour analysis-based device without need for calibration became available (FloTrac/Vigileo, Edwards Lifescience, Irvine, CA). This study was conducted to determine if there is an impact of the arterial catheter site and to investigate the accuracy of this system when compared with the pulmonary artery catheter using the bolus thermodilution technique (PAC). Prospective study. The operating room of 1 university hospital. Twenty patients undergoing cardiac surgery. CO was determined in parallel by the use of the Flotrac/Vigileo systems in the radial and femoral position (CO_rad and CO_fem) and by PAC as the reference method. Data triplets were recorded at defined time points. The primary endpoint was the comparison of CO_rad and CO_fem, and the secondary endpoint was the comparison with the PAC. Seventy-eight simultaneous data recordings were obtained. The Bland-Altman analysis for CO_fem and CO_rad showed a bias of 0.46 L/min, precision was 0.85 L/min, and the percentage error was 34%. The Bland-Altman analysis for CO_rad and PAC showed a bias of -0.35 L/min, the precision was 1.88 L/min, and the percentage error was 76%. The Bland-Altman analysis for CO_fem and PAC showed a bias of 0.11 L/min, the precision was 1.8 L/min, and the percentage error was 69%. The FloTrac/Vigileo system was shown to not produce exactly the same CO data when used in radial and femoral arteries, even though the percentage error was close to the clinically acceptable range. Thus, the impact of the introduction site of the arterial catheter is not negligible. The agreement with thermodilution was low.

Intraoperative validation of a new system for invasive continuous cardiac output measurement

Although bolus thermodilution technique for cardiac output (CO) measurement has widespread acceptance, new systems are currently available. We evaluated a continuous CO system (TruCCOMS, Aortech International Inc.) that operates on the thermal conservation principle and we compared it with the reference standard transit time flow measurement (TTFM). Nine consecutive cardiac surgery patients were evaluated. After general anesthesia and intubation, a TruCCOMS catheter was percutaneously placed in the pulmonary artery (PA). After median sternotomy and pericardiotomy, a TTFM probe was placed around the main PA. Right ventricular (RV) CO measurements were recorded with both TruCCOMS and TTFM at different times: before cardiopulmonary bypass (CPB) (T0), during weaning from CPB (T1), and prior to sternal closure (T2). Data analysis included paired student t test, Pearson correlation test, and Bland-Altman plotting. TruCCOMS CO values were significantly lower at T0 (TruCCOMS 4.0 +/- 1.0 vs. TTFM 4.5 +/- 1.0 L/min; P < 0.0001) and T1 (TruCCOMS 3.6 +/- 0.5 vs. TTFM 4.2 +/- 0.7 L/min; P < 0.0001), and comparable at T2 (TruCCOMS 4.5 +/- 0.7 vs. TTFM 4.6 +/- 0.8 L/min; P = 0.4). Pearson test showed a significant correlation between TruCCOMS and TTFM CO measurements (RT0 = 0.9, RT1 = 0.8, RT2 = 0.6; P < 0.0001). Bland-Altmann plotting showed a bias of -0.53 +/- 0.43 L (-12%) at T0, -0.64 +/- 0.43 L (-14.5%) at T1, and -0.1 +/- 0.66 L (-0.8%) at T2. Although TruCCOMS may significantly underestimate CO, measurement trends correlate with TTFM. For this reason, a negative trend in RV output should trigger more specific diagnostic procedures.

Cardiac Output Monitoring: Comparison of a New Arterial Pressure Waveform Analysis to the Bolus Thermodilution Technique in Patients Undergoing Off-Pump Coronary Artery Bypass Surgery

To analyze the clinical agreement between the conventional intermittent bolus thermodilution (TD) technique and a new arterial pressure waveform analysis (APCO) technique (FloTrac; Edward Lifesciences, Irvine, CA) for cardiac output (CO) estimation. Prospective observational clinical study. Cardiac surgery operating room of a tertiary care cardiac center. Twelve patients undergoing elective off-pump coronary artery bypass (OPCAB) surgery. CO was determined by 2 different methods: TD and APCO at 8 time points (preinduction, postinduction, poststernotomy, left internal mammary artery to left anterior descending artery anastomosis, left [obtuse marginal/diagonal] anastomosis, right [right coronary/posterior descending coronary artery] anastomosis, postprotamine administration, and poststernal closure) in 12 patients undergoing elective OPCAB surgery. The mean bias and limits of agreement (2 standard deviations) expressed in liters per minute at respective points of measurement were -0.54 +/- 1.12, -0.37 +/- 1.0, -0.42 +/- 1.50, -0.25 +/- 1.18, -0.31 + 1.28, +/-0.41 +/- 1.0, 0.06 +/- 1.50, and 0.09 +/- 1.40. Good agreement was found between the CO values obtained by the APCO and TD techniques throughout the intraoperative period including the period of coronary artery graft surgery.

Right Atrial Effects on Right Ventricular Ejection Fraction Derived From Thermodilution Measurements

The thermodilution technique provides a convenient means to monitor cardiac output, right ventricular (RV) ejection fraction (EF), and volumes at the bedside. To calculate RVEF from the pulmonary artery temperature curve, the bolus thermodilution technique assumes that right atrial (RA) temperature returns to baseline value within 1 beat following the cold saline injection. The authors hypothesized that this assumption is the reason why the thermodilution technique consistently underestimates RVEF. A theoretical analysis and animal study. Laboratory, university, multi-institutional. Animals. Cold saline injections. In 2 porcine experiments, after a rapid injection of cold saline into right atrium, RA temperature took several heartbeats to return to baseline. In a theoretical analysis, if after the cold saline injection RA temperature returned to baseline in 1 beat (RAEF = 1), then thermodilution-derived RVEF(T) = actual RVEF(A). In contrast, if RA temperature took several beats to return to baseline (RAEF = RVEF), then RVEF(T) consistently underestimated RVEF(A). A least square fit of RVEF(A) versus RVEF(T) resulted in RVEF(A) = 1.0 x RVEF(T) + 0.11. Applying this correction (adding 0.11 to RVEF(T)) to the data gave relatively small errors in estimating RVEF over a wide EF range. After injecting cold saline into the right atrium, RA temperature takes several heart beats to return to baseline temperature, leading to underestimating RVEF and overestimating RV volumes. The pulsed thermal energy approach by injecting heat into the RV avoids these problems, but the impact of its small temperature signal on RVEF measurements needs to be determined.

Cardiac output estimation after off-pump coronary artery bypass: A comparison of two different techniques

The present study compares the cardiac output (CO) estimated by a new, non-invsive continuous Doppler device (Ultrasonic cardiac output monitor-USCOM) with that by bolus thermodilution technique (TD). Thirty post off-pump coronary artery bypass graft surgery patients were studied in this prospective nonrandomized study. Right heart CO estimation by USCOM and TD was performed and measured in quadruplet. A total of 120 paired observations were made. The mean CO was 4.63 and 4.76 Llmin as estimated by TD and USCOM respectively. For TD and USCOM, the CO had a mean bias (tendency of one technique to differ from other) of -0.13 L/min and limits of agreement (mean bias +/- 2SD) at -0.86 and 0.59 L/min. The study reveals very good agreement between the values of CO estimated by USCOM and TD.

Cardiac Output Estimation With a New Doppler Device After Off-Pump Coronary Artery Bypass Surgery

To compare cardiac output (CO), stroke volume (SV), and cardiac index (CI) as estimated with a new, noninvasive Doppler device (Ultrasonic Cardiac Output Monitor [USCOM]; USCOM Ltd, Sydney, Australia) with those measured with the bolus thermodilution (TD) technique. Prospective nonrandomized study. Postcardiac surgery recovery unit of a tertiary cardiac center. Fifty patients after off-pump coronary artery bypass (OPCAB) surgery. Both right-sided and left-sided CO were estimated with a USCOM continuous-wave (CW) Doppler device, and CO was determined with the bolus TD technique performed in triplicate. On comparing the right-sided CO, SV, and CI with those of TD, the mean bias was 0.03 L/min, 1.6 mL, and 0.02 L/min/m(2), respectively. The comparison of left-sided CO, SV, and CI with those of TD revealed a means bias of 0.14 L/min, 1.0 mL, and 0.08 L/min/m(2), respectively. This study showed excellent agreement between the values for CO, SV, and CI as determined with USCOM and TD. Since there was only 1 time period for CO estimation in each patient with both methods, the stability of this correlation needs to be further investigated over time.

Comparison of Cardiac Output in OPCAB : Bolus Thermodilution Technique versus Pulse Contour Analysis

The study was designed to evaluate the clinical agreement between intermittent bolus thermodilution technique and pulse contour analysis technique. Sixty patients with normal left ventricular function undergoing elective off-pump coronary bypass surgery were included in this prospective study. In addition to routine monitoring, a 7.5F pulmonary artery thermodilution catheter via right internal jugular vein and a 4F arterial thermodilution catheter into femoral artery were also placed. Cardiac output measurements were compared before induction, after induction, after sternotomy, during the various anastomoses, post-protamine and post-sternal closure. Statistical analysis was performed using analysis of agreement to assure bias distribution of differences between the two methods by using Bland and Altman analysis. The cardiac output values obtained at preinduction, post-induction, and post-sternal closure time points showed good agreement, whereas the values obtained during the various anastomoses showed significant differences (p <0.05). Therefore it was concluded that pulse contour analysis cannot be relied upon completely whenever there is a change in the position of heart or alteration in systemic vascular resistance. But the trends in cardiac output were in complete agreement during the entire procedure.

Measurement of cardiac output: Comparison of four different methods

Background In off pump Coronary Artery Bypass Grafting (OPCAB), dislocation of the heart influences cardiac output (CO) rapidly. In this study, we compared bolus thermodilution technique (TDCO) with thermal based Continuous cardiac output (CCO), Pulse contour Cardiac Output (Pulse CO) technique and Non Invasive Cardiac Output (NICO) techniques of continuous cardiac output measurement.

Effects of Body Temperature on Accuracy of Continuous Cardiac Output Measurements

Intermittent measurement of cardiac output is routine in the critically ill surgical patient. A new catheter allows real-time continuous measurement of cardiac output. This study evaluated the impact of body temperature variation on the accuracy of these measurements compared to standard intermittent bolus thermodilution technique. This prospective study in a university hospital surgical intensive care unit included 20 consecutive trauma patients. Data were collected with pulmonary artery catheters, which allowed both continuous (COC) and bolus (COB) thermodilution measurements. The catheter was placed through either the subclavian or internal jugular vein. Measurements for COB were performed using a bolus (10cm3) of ice-cold saline with a closed-injectate delivery system at end-expiration. Computer-generated curves were created on a bedside monitor, and the average of three measurements within 10% of one another was used as COB. COC

Thermal filament continuous thermodilution cardiac output delayed response limits its value during acute hemodynamic instability.

It has been suggested that measurement of continuous cardiac output (CCO) is an advancement in the management of critically ill patients. Our objective was to determine the accuracy of CCO during the rapid hemodynamic changes induced by hemorrhage and resuscitation. In 12 anesthetized dogs (20.2+/-0.9 kg), pulmonary artery blood flow, our "gold standard" cardiac output, was measured with an sonographic flowprobe, whereas CCO, intermittent bolus cardiac output (ICO), and mixed venous oxygen saturation were measured with a thermodilution fiberoptic pulmonary artery catheter with a thermal filament. A graded hemorrhage (20 mL/min) was produced to a mean arterial pressure of 40 mm Hg, which was maintained at this level for 30 minutes. Total shed blood volume (701+/-53 mL) was retransfused at a rate of 40 mL/min, over 30 minutes, after which a massive hemorrhage (100 mL/min) was produced over 10 minutes. Hemorrhage induced significant decreases in mean arterial pressure, mixed venous oxygen saturation, and oxygen delivery, which were all restored during early resuscitation. However, CCO showed a delayed response after hemorrhage and resuscitation, compared with pulmonary blood flow, throughout the study (r = 0.549), matching only at baseline and at the end of both graded hemorrhage and resuscitation periods. There was a good correlation between ICO and pulmonary artery blood flow (r = 0.964) and no significant differences between them throughout the study. CCO has a delayed response during acute hemodynamic changes induced by hemorrhage and resuscitation. When sudden changes in mean arterial pressure or in mixed venous oxygen saturation are detected, cardiac output must be estimated by the standard bolus thermodilution technique, not by CCO.

Continuous cardiac output measurement: pulse contour analysis vs thermodilution technique in cardiac surgical patients

We have analysed the clinical agreement between two methods of continuous cardiac output measurement pulse contour analysis (PCCO) and a continuous thermodilution technique (CCO), were both compared with the intermittent bolus thermodilution technique (BCO). Measurements were performed in 26 cardiac surgical patients (groups 1 and 2, 13 patients each, with an ejection fraction > 45% and < 45%, respectively) at 12 selected times. During operation, mean differences (bias) between PCCO-BCO and CCO-BCO did not differ in either group. However, phenylephrine-induced increases in systemic vascular resistance (SVR) by approximately 60% resulted in significant differences. Significantly higher absolute bias values of PCCO-BCO compared with CCO-BCO were also found early after operation in the ICU. Thus PCCO and CCO provided comparable measurements during coronary bypass surgery. After marked changes in SVR, further calibration of the PCCO device is necessary.

Intra-operative evaluation of a continuous versus intermittent bolus thermodilution technique of cardiac output measurement in cardiac surgical patients

The purpose of this study was to analyse the clinical agreement between cardiac output measurements, obtained using a newly available continuous thermodilution technique, and the conventional intermittent bolus technique. Twenty-four cardiac surgical patients were intra-operatively monitored using both techniques. Additionally, two different averaging modes for the continuous thermodilution technique, either the previous 6 min (group 1) or 3 min (group 2) were compared. The mean difference between the continuous thermodilution technique and the intermittent bolus technique (bias), were calculated at eight selected time points. These ranged from -0.09 to 0.42 litres min-1 in group 1 and from -0.02 to 0.18 litres min-1 in group 2. There were significant differences at any time point between the groups. The relative error between continuous thermodilution and intermittent bolus techniques was < 15% for the majority of measurements and was significantly higher in group 1 compared with group 2 just prior to cardiopulmonary bypass. Thus, the continuous thermodilution technique produced a clinically acceptable level of accuracy compared with the intermittent bolus technique measurements, especially when using an averaging mode for the previous 3 min.

Intra-operative evaluation of a continuous versus intermittent bolus thermodilution technique of cardiac output measurement in cardiac surgical patients

The purpose of this study was to analyse the clinical agreement between cardiac output measurements, obtained using a newly available continuous thermodilution technique, and the conventional intermittent bolus technique. Twenty-four cardiac surgical patients were intra-operatively monitored using both techniques. Additionally, two different averaging modes for the continuous thermodilution technique, either the previous 6 min (group 1) or 3 min (group 2) were compared. The mean difference between the continuous thermodilution technique and the intermittent bolus technique (bias), were calculated at eight selected time points. These ranged from −0.09 to 0.42 litres min−1 in group 1 and from −0.02 to 0.18 litres min−1 in group 2. There were significant differences at any time point between the groups. The relative error between continuous thermodilution and intermittent bolus techniques was <15% for the majority of measurements and was significantly higher in group 1 compared with group 2 just prior to cardiopulmonary bypass. Thus, the continuous thermodilution technique produced a clinically acceptable level of accuracy compared with the intermittent bolus technique measurements, especially when using an averaging mode for the previous 3 min.