Continuous Cardiac Output Measurement Research Articles

Early and Sustained Systemic and Renal Hemodynamic Effects of Intravenous Radiocontrast

Background and Aims: To measure the extended renal hemodynamic changes induced by intravenous radiocontrast. Methods: Cross-ewes were studied in a randomized cross-over study. Intravenous saline or radiocontrast were administered, and continuous measurement of cardiac output and renal blood flow (RBF) was performed with flow probes. Results: Radiocontrast induced early but transient increases in cardiac output with vasodilatation, followed by return to baseline values within 2 h. There was an initial decline in RBF (–5.2 ± 4.5 vs. 2.1 ± 5.3%; p < 0.0001) and decreased renal vascular conductance (–4.0 ± 7.2 vs. 3.3 ± 7.1%, p < 0.0001; vasoconstriction). This renal vasoconstriction resolved within 2 h and was followed by sustained (72 h) renal vasodilatation with higher RBF (270 ± 13 vs. 236 ± 11 ml/min; p < 0.0001). Conclusions: Radiocontrast induces short renal vasoconstriction followed by sustained vasodilatation and increased RBF. Short-term studies are not representative of the overall sustained renal hemodynamic effects of radiocontrast.

Assessment of a Cardiac Output Device using Arterial Pulse Waveform Analysis, VigileoTM, in Cardiac Surgery Compared to Pulmonary Arterial Thermodilution

Many devices are available to assess cardiac output (CO) in critically ill patients and in the operating room. Classical CO monitoring via a pulmonary artery catheter involves continuous cardiac output (CCO) measurement. The second generation of Flotrac/Vigileo monitors propose an analysis of peripheral arterial pulse waves to calculate CO (APCO) without calibration. The aim of our study was to compare the CO between the Swan Ganz catheter and the VigileoT. In this observational study, nine patients undergoing coronary artery bypass grafting were prospectively included. APCO, mean (CCO) and instantaneous CO (ICO) were measured. Perioperative and postoperative assessments were performed up to 24 hours post-surgery. Measurements were recorded every minute, resulting in the collection of 6492 data pairs. Comparison of APCO and ICO showed a limited bias of -0.1 l/min but an important percentage error of 48%. Corresponding values were -0.1 l/min and 46% for the APCO versus CCO comparison, and 0 and 17% for ICO versus CCO comparison. Large inter-individual variability does exist. During cardiac surgery and after leaving the operating room, Vigileo is not clinically equivalent to continuous thermodilution by pulmonary artery catheter Nevertheless, the connection between CCO and ICO relates the difference between APCO and CCO more to the different algorithms used. Further efforts should be concentrated on assessing the ability of this device to track changes in cardiac output.

Continuous cardiac output measurement: effect of time

Calibration turns pulse contour methods of cardiac output measurement from continuous to intermittent. We evaluated the necessity to recalibrate pulse contour cardiac output methods; LiDCO™plus (LCO), FloTrac/Vigileo (FCO), PiCCO (PCO) and continuous CO measurement with pulmonary artery catheter (Vigilance) (CCO).

In vitro, in vivo and numerical assessment of the working principle of the truCCOMS™ continuous cardiac output catheter system

The truCCOMS™ cardiac output monitor system provides a continuous and instantaneous measurement of cardiac output, derived from the amount of energy required for heating a filament to maintain a fixed 2 °C blood temperature difference between two thermistors located distally on a pulmonary artery catheter. Clinical studies, however, reported relatively poor accuracy of the cardiac output estimation, possibly due to linearly assumed power–cardiac output relationship used for calibration of the catheters. We experimentally studied the shape of the truCCOMS™ calibration relationship (i) in a hydraulic bench model of the right heart and (ii) in vivo intact animal model. The results showed a nonlinear relationship between the power input into the heating element and the cardiac output; which could satisfactorily be described with an exponential relationship. Comparison of the performance of the same catheters in vitro and in vivo showed that the in vitro determined calibration relationship should not be used for in vivo measurements. Finally, we also simulated the working principle of the catheter using a simplified numerical model of the blood flow and heat transfer around the catheter. The computed results also suggested a pronounced nonlinear relationship between power and cardiac output in pulsatile conditions. We conclude that the observed over- and underestimation of high- and low flows, respectively, by the current truCCOMS™ system is likely to arise from its linear calibration relationship. An appropriate calibration scheme accounting for the intrinsic nonlinear power–cardiac output relationship and the difference between in vitro and in vivo conditions should improve the clinical performance of the system.

Uncalibrated Radial and Femoral Arterial Pressure Waveform Analysis for Continuous Cardiac Output Measurement: An Evaluation in Cardiac Surgery Patients

Arterial pressure waveform analysis is a less invasive alternative to the pulmonary artery catheter for continuous cardiac output (CO) measurement. Uncalibrated and calibrated systems are actually available (ie, the FloTrac/Vigileo system [Edwards Lifesciences, Irvine, CA] and the PiCCOplus system [Pulsion Medical Systems, Munich, Germany]). According to the FloTrac/Vigileo manufacturer, reliable measurements can be performed using any existing arterial catheter. The aim of this study was to evaluate CO determined by the FloTrac/Vigileo system using a radial (FCO(radial)) and femoral arterial catheter (FCO(femoral)) as well as the PiCCOplus system (PCO). Intermittent pulmonary artery thermodilution (ICO) was used as primary reference technique. A prospective clinical study. A teaching hospital, single center. Twenty-six cardiac surgery patients. Perioperative CO measurements. CO was assessed at predefined measurement points. FCO(radial), FCO(femoral), and PCO were recorded after the induction of anesthesia, after sternotomy, at skin closure, after intensive care unit transfer, and during intensive care unit stay 12 and 24 hours after study initiation. ICO was determined as the mean of 3 bolus injections. Bland-Altman analysis revealed comparable mean bias and limits of agreement for FCO(radial), FCO(femoral), and PCO when compared with ICO. There was a decreased agreement for all devices in the postoperative period. However, a consistently close agreement was observed for the direct comparison between FCO(radial) and FCO(femoral). Performance of the FloTrac/Vigileo system via radial as well as femoral access and the PiCCOplus monitoring for cardiac output measurement were comparable when tested against intermittent thermodilution in cardiac surgery patients.

Cardiac arrhythmias related to continuous thermodilution cardiac output measurement in an anaesthetized sheep

A case of cardiac arrhythmias related to continuous thermodilution cardiac output (CCO) is reported. A sheep anaesthetized for experimental purpose was instrumented with a special Swan-Ganz catheter-type to be used for CCO measurements. One hour after starting the CCO monitoring, isolated ventricular extrasystoles were noticed on the electrocardiogram with an increasing frequency. Subsequently bursts of extrasystoles occurred. Atrioventricular dissociation was also observed. The peaks of temperature of the thermal filament were within the normal range and their presence was noticed when arrhythmias appeared. Mean blood pressure and cardiac output did not change during this episode. When the CCO was switched off, no more arrhythmias were observed. The CCO Swan-Ganz by itself did not generate any arrhythmia. The sheep recovered uneventfully. When arrhythmias occur during anaesthesia where CCO is used, a thermal filament induced origin of the arrhythmia must be considered.

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.

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

Cross-comparison of the trending accuracy of continuous cardiac output measurement devices in postoperation patients

Arterial pulse analysis estimates of cardiac output (CO) are less invasive than pulmonary artery catheter (PAC)-derived ones. Although PAC bolus thermodilution CO (COtd) values are the reference CO values for most clinical studies, there is no defined gold standard. We therefore compared the covariance of three commercially available arterial pulse analysis devices (FloTrac, LiDCO, PiCCO) and PAC with COtd and continuous CO (CCO).

Continuous, non-invasive techniques to determine cardiac output in children after cardiac surgery: evaluation of transesophageal Doppler and electric velocimetry

Continuous and non-invasive measurement of cardiac output (CO) may contribute helpful information to the care and treatment of the critically ill pediatric patient. Different methods are available but their clinical verification is still a major problem. Comparison of reliability and safety of two continuous non-invasive methods with transthoracic echocardiography (TTE) for CO measurement: electric velocimetry technique (EV, Aesculon) and transesophageal Doppler (TED, CardioQP). METHODS/MATERIAL: In 26 infants and children who had undergone corrective cardiac surgery at a median age of 3.5 (1-17) years CO and stroke volume (SV) were obtained by EV, TED and TTE. Each patient had five measurements on the first day after surgery, during mechanical ventilation and sedation. Values for CO and SV from TED and EV correlated well with those of TTE (r = 0.85 and r = 0.88), but mean values were significantly lower than the values of TTE for TED (P = 0.02) and EV (P = 0.001). According to Bland-Altman analysis, bias was 0.36 l/min with a precision of 1.67 l/min for TED vs. TTE and 0.87 l/min (bias) with a precision of 3.26 l/min for EV vs. TTE. No severe adverse events were observed and the handling of both systems was easy in the sedated child. In pediatric patients non-invasive measurement of CO and SV with TED and EV is useful for continuous monitoring after heart surgery. Both new methods seem to underestimate cardiac output in terms of absolute values. However, TED shows tolerable bias and precision and may be helpful for continuous CO monitoring in a deeply sedated and ventilated pediatric patient, e.g. in the operating room or intensive care unit.

Is It More Informative to Focus on Cardiac Output than Blood Pressure during Spinal Anesthesia for Cesarean Delivery in Women with Severe Preeclampsia?

Is It More Informative to Focus on Cardiac Output than Blood Pressure during Spinal Anesthesia for Cesarean Delivery in Women with Severe Preeclampsia?

Monitoring preload during liver transplantation

Liver transplantation is associated with major shifts incentral blood volume; therefore, monitoring preload is es-sential. Filling pressures (central venous pressure or pul-monary artery occlusion pressure) do not reflect preload[right ventricular end-diastolic volume (RVEDV) or leftventricular end-diastolic volume (LVEDV)] well becausethese pressures are affected not just by preload but alsoby changes in compliance of the heart. These compliancechanges can be quite significant because of the changesin chest volume that are the result of surgical retractionand variable pressure on the diaphragm. Then, what arethe alternative methods of preload monitoring in the op-erating room? There are only two: thermodilution deter-mination of RVEDV and transesophageal echocardio-graphic estimation of RVEDV and LVEDV. Each of thesetechniques has advantages and disadvantages.The clinical determination of the right ventricularejection fraction (RVEF) and RVEDV became possible inthe early 1980s when American Edwards Laboratoriesmarketed a pulmonary artery catheter with a fast-re-sponse thermistor and an accompanying computer.That technology was based on intermittent injection ofa cold solution as a dye, and the principle of conserva-tion of energy allowed the calculation of RVEF and rightventricular volumes.

Comparison of Continuous, Stat, and Intermittent Bolus Cardiac Output Measurements during Cardiac Surgery

(46.2%) for CCI and 0.09 ± 0.60 L/min/m 2 (44.0%) for SCI, compared with ICI measurements. Conclusions: We found that the agreement of CCI, SCI, and ICI was poor. This disagreement increased during periods of open thorax and open pericardium when compared to the period of closed thorax. Continuous CO measurements through pulmonary artery catheter should be interpreted with caution during OPCAB. (Korean J Anesthesiol 2008; 54: 603∼8)

Reliability of continuous pulse contour cardiac output measurement

To evaluate the reliability of continuous cardiac output monitoring using pulse-contour analysis in critically ill patients.

Reliability of continuous cardiac output measurement during intra-abdominal hypertension relies on repeated calibrations: an experimental animal study

IntroductionMonitoring cardiac output (CO) may allow early detection of haemodynamic instability, aiming to reduce morbidity and mortality in critically ill patients. Continuous cardiac output (CCO) monitoring is recommended in septic or postoperative patients with high incidences of intra-abdominal hypertension (IAH). The aim of the present study was to compare the agreement between three CCO methods and a bolus thermodilution CO technique during acute IAH and volume loading.MethodsTen pigs were anaesthetised and instrumented for haemodynamic measurements. Cardiac output was obtained using CCO by pulse power analysis (PulseCO; LiDCO monitor), using CCO by pulse contour analysis (PCCO; PiCCO monitor) and using CCO by pulmonary artery catheter thermodilution (CCOPAC), and was compared with bolus transcardiopulmonary thermodilution CO (COTCP) at baseline, after fluid loading, at IAH and after an additional fluid loading at IAH. Whereas PulseCO was only calibrated at baseline, PCCO was calibrated at each experimental step.ResultsPulseCO and PCCO underestimated CO, as the overall bias ± standard deviation was 1.0 ± 1.5 l/min and 1.0 ± 1.1 l/min compared with COTCP. A clinically accepted agreement between all of the CCO methods and COTCP was observed only at baseline. Whereas IAH did not influence the CO, increased CO following fluid loading at IAH was only reflected by CCOPAC and COTCP, not by uncalibrated PulseCO and PCCO. After recalibration, PCCO was comparable with COTCP.ConclusionsThe CO obtained by uncalibrated PulseCO and PCCO failed to agree with COTCP during IAH and fluid loading. In the critically ill patient, recalibration of continuous arterial waveform CO methods should be performed after fluid loading or before a major change in therapy is initiated.

Continuous and intermittent cardiac output measurement in hyperdynamic conditions: pulmonary artery catheter vs. lithium dilution technique

This study aimed to assess the level of agreement of both intermittent cardiac output monitoring by the lithium dilution technique (CO(Li)) and continuous cardiac output monitoring (PulseCO(Li)) using the arterial pressure waveform with intermittent thermodilution using a pulmonary artery catheter (CO(PAC)). Prospective, single-center evaluation. University Hospital Intensive Care Unit. Patients (n=23) receiving liver transplantation. Pulmonary artery catheters were placed in all patients and CO(PAC) was determined using thermodilution. CO(Li) and PulseCO(Li) measurements were made using the LiDCO system. Data were collected after intensive care unit admission and every 8h until the 48th hour. A total of 151 CO(PAC), CO(Li) and PulseCO(Li) measurements were analysed. Bias and 95% limit of agreement were 0.11lmin(-1) and -1.84 to + 2.05 lmin(-1) for CO(PAC) vs. CO(Li) (r=0.88) resulting in an overall percentage error of 15.6%. Bias and 95% limit of agreement for CO(PAC) vs. PulseCO(Li) were 0.29 lmin(-1) and -1.87 to + 2.46 lmin(-1) (r=0.85) with a percentage error of 16.8%. Subgroup analysis revealed a percentage error of 15.7% for CO(PAC) vs. CO(Li) and 15.1% for CO(PAC) vs. PulseCO(Li) for data pairs less than 8 lmin(-1), and percentage errors of 15.5% and 18.5% respectively for data pairs higher than 8 lmin(-1). In patients with hyperdynamic circulation, intermittent and continuous CO values determined using the LiDCO system showed good agreement with those obtained by intermittent pulmonary artery thermodilution.

Continuous cardiac output during off-pump coronary artery bypass surgery: pulse-contour analyses vs pulmonary artery thermodilution

No gold standard method exists for monitoring continuous cardiac output (CO). In this study, the agreement between the two most frequently used methods, PiCCO pulse-contour analysis (PCCO) and STAT pulmonary artery thermodilution (STAT-CO), was assessed during multiple-vessel off-pump coronary artery bypass (OPCAB) surgery. Thirty patients were enrolled in the study. Two time periods were defined during surgery; Period 1 included positioning of the heart and stabilizer device and Period 2 included the coronary occlusion. Measurements were obtained every minute during both periods. The agreement for the continuous CO and the change in CO (DeltaCO) was estimated using the Bland-Altman method. Significant changes in mean arterial pressure (DeltaMAP), central venous saturation, PCCO and STAT-CO were seen only during Period 1. DeltaMAP correlated only with changes in PCCO, (P < 0.001, r = 0.60). The mean difference (2sd) between PCCO and STAT-CO ranged from - 0.29 (1.82) to - 0.71 (2.57) litre min(-1), and the percentage error varied from 32 to 50%. For the CO measurements, the limits of agreements did not differ between Period 1 and Period 2. In contrast, for the DeltaCO measurements, the limits of agreements were wider in Period 1 than in the more haemodynamically stable Period 2. CCO and STAT-CO show large discrepancies in CO during OPCAB surgery. Clinically acceptable agreement was seen only for trends in CO during haemodynamically stable periods.

Continuous cardiac output measurement: arterial pressure analysis versus thermodilution technique during cardiac surgery with cardiopulmonary bypass

This study compared cardiac output measured with an arterial pressure-based cardiac output measurement system and a thermodilution cardiac output measurement system. We studied 36 patients undergoing cardiac surgery with cardiopulmonary bypass. Simultaneous arterial pressure-based and thermodilution cardiac output measurements were compared before and after cardiopulmonary bypass, and after phenylephrine administration. Bland-Altman analysis showed good overall agreement between the two methods. Bias (limits of agreement) before and after cardiopulmonary bypass were - 0.21 (- 2.97-2.55) lxmin(-1) and 0.01 (- 3.79-3.81) lxmin(-1), respectively. Phenylephrine administration decreased thermodilution cardiac output by a mean (SD) of 11 (16)% and increased arterial pressure-based cardiac output by 55 (34)%. We conclude that arterial pressure-based cardiac output and thermodilution cardiac output measurement systems yield comparable results during cardiac surgery with cardiopulmonary bypass. However, after phenylephrine administration, the two measurement systems provided opposing results.

Cardiac output measurements during off-pump coronary surgery

Reply EDITOR: We thank Dr Renner and colleagues for their interest in our article and their comments. We are grateful for all input into the discussion about our article on cardiac output monitoring during off-pump coronary artery bypass (OPCAB) surgery. We agree with Dr Renner and colleagues that aortic transit-time ultrasound (ATTUS) cardiac output measurement is the true clinical gold standard for instantaneous cardiac output measurements. However, to our knowledge, in the case of OPCAB surgery, ATTUS has not yet been compared with other cardiac output measurement techniques. Indeed, continuous cardiac output measurements with either pulmonary artery catheter or partial CO2 rebreathing (PRCO) techniques do not provide continuous beat-to-beat assessment of cardiac output. Ideally, the best monitoring equipment should be non-invasive and beat-to-beat, and neither PRCO nor ATTUS achieve both of these ideals. Concerning ventilation during OPCAB surgery, our anaesthetists only exceptionally have to decrease tidal volume below 10 mL kg−1 in order to adjust to the needs of the surgeons. End-tidal CO2 is maintained by adjusting respiratory rate. As we mentioned in our article, no changes in cardiac output readings were observed, suggesting that acute haemodynamic events recorded by either method were related to changes in ventilatory settings. The differences in attitudes of surgeons and between institutions towards tidal volume during OPCAB surgery might be the reason why we were not concerned about the theoretical link of low tidal volume and inadequate rebreathing under our operating conditions. In addition, as mentioned by Tachibana and colleagues [1], the accuracy of the non-invasive cardiac output (NICO) technique can be maintained even at small tidal volumes if normocapnia is achieved by adjusting the respiratory rate. Conversely, the same authors also stated that the NICO underreports cardiac output at small tidal volumes. On the other hand, it is the variation of cardiac output which gives more information about acute haemodynamic changes than the absolute number itself. A disadvantage of underestimation of cardiac output could rather serve as an incentive to react quicker to haemodynamic changes. The assumption of a stable pulmonary capillary blood flow during NICO measurement cycles is indeed a drawback, and recalibration is needed in case of changes of SPO2 and FiO2. We stated that the NICO showed a faster response than the pulmonary artery catheter during OPCAB surgery. In fact, this statement was based on observation and it is correct to add that it has not been substantiated by any of our data. Bein and colleagues [2] correctly concluded that NICO as compared to ATTUS is not suitable for cardiac output determination during quickly changing haemodynamic conditions applicable to their setting of aortic reconstruction. However, to our knowledge ATTUS has neither been examined nor brought into practice as a monitoring tool for OPCAB surgery. Therefore, in this context, even with a delayed response time of 165 s, NICO still remains an interesting monitoring option for OPCAB surgery [3].

Comparison of two methods for enhanced continuous circulatory monitoring in patients with septic shock

To compare a modified pulmonary artery catheter (PAC) and pulse-contour analysis by the PiCCO (Pulsion Medical Systems, Munich, Germany) system for continuous assessment of cardiac output in patients with septic shock. In addition, to assess the relationships between an index of global end-diastolic volume (GEDV) derived by the PiCCO system with traditional PAC-derived indicators of filling: central venous pressure; pulmonary artery occlusion pressure; and right ventricular end-diastolic volume (RVEDV). Prospective cohort study. Surgical intensive care unit of a university hospital. 14 patients with septic shock. None. A significant correlation was found between continuous cardiac output by PAC (CCO(PAC)) and by pulse-contour analysis (r (2) = 0.714, p < 0.0001), accompanied by a bias of 0.1 l min(-1) and a precision of 2.7 l min(-1). The correlation between CCO(PAC) and cardiac output measured by transcardiopulmonary thermodilution was also significant (r (2) = 0.781, p < 0.0001). There was a bias for the two methods of 0.2 l min(-1), and a precision of 2.2 lmin(-1). The GEDV showed no correlation with central venous pressure, pulmonary artery occlusion pressure, or RVEDV. In patients with septic shock, the averaged bias in continuous measurement of cardiac output by both a modified pulmonary artery catheter and pulse-contour analysis was small, but variability was large. No correlation was found between GEDV and RVEDV. The clinical importance of different cardiac filling parameters needs further investigation.