The impact of systemic vascular resistance on the accuracy of the FloTrac/Vigileo™ system in the perioperative period of cardiac surgery: a prospective observational comparison study

FloTrac/Vigileo? system is based on arterial pressure waveform analysis arterial pressure-based CO (APCO). Therefore, systemic vascular resistance (SVR) can influence the accuracy of APCO. The purpose of this study is to evaluate the relationship between SVR and the accuracy of APCO. We managed 50 consecutive patients in the perioperative period of cardiac surgery with FloTrac/Vigileo? system (v. 3.02) and Swan–Ganz catheter/Vigilance? system pulmonary artery catheter-based CO (PAC-CO) simultaneously. Continuous hemodynamic measurement using both methods was performed every 20 s from the induction of anesthesia to PAC removal 4 h after extubation. A total of 11,092 (intraoperative), 38,455 (postoperative, pre-extubation), and 44,235 (postoperative, post-extubation) data pairs were finally analyzed. Bland–Altman analysis revealed that in the intraoperative [postoperative pre-extubation, post-extubation] period, the bias was 0.5 [0.1, 0.0] L/min and the limits of agreement ranged from ?2.4 to 3.3 [?2.2 to 2.4, ?2.4 to 2.3] L/min. The percentage error was 60.3 [54.5, 48.5] %. Regression analysis of the systemic vascular resistance index (SVRI) and the bias between APCO and PAC-CO showed that the bias was positively correlated to the SVRI. Subanalysis based on SVR with Lin’s concordance correlation coefficient revealed that relatively satisfactory concordance was found in the normal-SVR group (concordance correlation coefficient ρ _c = 0.51–0.56) regardless of vasoactive agent use. The accuracy of the FloTrac/Vigileo? System (v. 3.02) is relatively satisfactory in the condition with normal SVR regardless of vasoactive agent use. Positive correlation between the bias and SVR can be the clue to the more effective use of FloTrac/Vigileo? system.     

Continuous noninvasive cardiac output determination using the CNAP system: evaluation of a cardiac output algorithm for the analysis of volume clamp method-derived pulse contour

The CNAP system (CNSystems Medizintechnik AG, Graz, Austria) provides noninvasive continuous arterial pressure measurements by using the volume clamp method. Recently, an algorithm for the determination of cardiac output by pulse contour analysis of the arterial waveform recorded with the CNAP system became available. We evaluated the agreement of the continuous noninvasive cardiac output (CNCO) measurements by CNAP in comparison with cardiac output measurements invasively obtained using transpulmonary thermodilution (TDCO). In this proof-of-concept analysis we studied 38 intensive care unit patients from a previously set up database containing CNAP-derived arterial pressure data and TDCO values obtained with the PiCCO system (Pulsion Medical Systems SE, Feldkirchen, Germany). We applied the new CNCO algorithm retrospectively to the arterial pressure waveforms recorded with CNAP and compared CNCO with the corresponding TDCO values (criterion standard). Analyses were performed separately for (1) CNCO calibrated to the first TDCO (CNCO-cal) and (2) CNCO autocalibrated to biometric patient data (CNCO-auto). We did not perform an analysis of trending capabilities because the patients were hemodynamically stable. The median age and APACHE II score of the 22 male and 16 female patients was 63 years and 18 points, respectively. 18 % were mechanically ventilated and in 29 % vasopressors were administered. Mean ± standard deviation for CNCO-cal, CNCO-auto, and TDCO was 8.1 ± 2.7, 6.4 ± 1.9, and 7.8 ± 2.4 L/min, respectively. For CNCO-cal versus TDCO, Bland–Altman analysis demonstrated a mean difference of +0.2 L/min (standard deviation 1.0 L/min; 95 % limits of agreement ?1.7 to +2.2 L/min, percentage error 25 %). For CNCO-auto versus TDCO, the mean difference was ?1.4 L/min (standard deviation 1.8 L/min; 95 % limits of agreement ?4.9 to +2.1 L/min, percentage error 45 %). This pilot analysis shows that CNCO determination is feasible in critically ill patients. A percentage error of 25 % indicates acceptable agreement between CNCO-cal and TDCO. The mean difference, the standard deviation, and the percentage error between CNCO-auto and TDCO were higher than between CNCO-cal and TDCO. A hyperdynamic cardiocirculatory state in a substantial number of patients and the hemodynamic stability making trending analysis impossible are main limitations of our study.     

A modified breathing pattern improves the performance of a continuous capnodynamic method for estimation of effective pulmonary blood flow

In a previous study a new capnodynamic method for estimation of effective pulmonary blood flow (CO_EPBF) presented a good trending ability but a poor agreement with a reference cardiac output (CO) measurement at high levels of PEEP. In this study we aimed at evaluating the agreement and trending ability of a modified CO_EPBF algorithm that uses expiratory instead of inspiratory holds during CO and ventilatory manipulations. CO_EPBF was evaluated in a porcine model at different PEEP levels, tidal volumes and CO manipulations (N = 8). An ultrasonic flow probe placed around the pulmonary trunk was used for CO measurement. We tested the CO_EPBF algorithm using a modified breathing pattern that introduces cyclic end-expiratory time pauses. The subsequent changes in mean alveolar fraction of carbon dioxide were integrated into a capnodynamic equation and effective pulmonary blood flow, i.e. non-shunted CO, was calculated continuously breath by breath. The overall agreement between CO_EPBF and the reference method during all interventions was good with bias (limits of agreement) 0.05 (?1.1 to 1.2) L/min and percentage error of 36 %. The overall trending ability as assessed by the four-quadrant and the polar plot methodology was high with a concordance rate of 93 and 94 % respectively. The mean polar angle was 0.4 (95 % CI ?3.7 to 4.5)°. A ventilatory pattern recurrently introducing end-expiratory pauses maintains a good agreement between CO_EPBF and the reference CO method while preserving its trending ability during CO and ventilatory alterations.     

Comparison of the ability of two continuous cardiac output monitors to measure trends in cardiac output: estimated continuous cardiac output measured by modified pulse wave transit time and an arterial pulse contour-based cardiac output device

Estimated continuous cardiac output (esCCO), a noninvasive technique for continuously measuring cardiac output (CO), is based on modified pulse wave transit time, which in turn is determined by pulse oximetry and electrocardiography. However, its trending ability has never been evaluated in patients undergoing non-cardiac surgery. Therefore, this study examined esCCO’s ability to detect the exact changes in CO, compared with currently available arterial waveform analysis methods, in patients undergoing kidney transplantation. CO was measured using an esCCO system and arterial pressure-based CO (APCO), and compared with a corresponding intermittent bolus thermodilution CO (ICO) method. Percentage error and statistical methods, including concordance analysis and polar plot analysis, were used to analyze results from 15 adult patients. The difference in the CO values between esCCO and ICO was ?0.39 ± 1.15 L min^?1 (percentage error, 35.6 %). And corrected precision for repeated measures was 1.16 L min^?1 (percentage error for repeated measures, 36.0 %). A concordance analysis showed that the concordance rate was 93.1 %. The mean angular bias was ?1.8° and the radial limits of agreement were ±37.6°. The difference between the APCO and ICO CO values was 0.04 ± 1.37 L min^?1 (percentage error, 42.4 %). And corrected precision for repeated measures was 1.37 L min^?1 (percentage error for repeated measures, 42.5 %). The concordance rate was 89.7 %, with a mean angular bias of ?3.3° and radial limits of agreement of ±42.2°. This study demonstrated that the trending ability of the esCCO system is not clinically acceptable, as judged by polar plots analysis; however, its trending ability is clinically acceptable based on a concordance analysis, and is comparable with currently available arterial waveform analysis methods.     

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.     

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).     

Evaluation of the use of the fourth version FloTrac system in cardiac output measurement before and after cardiopulmonary bypass

The FloTrac system is a system for cardiac output (CO) measurement that is less invasive than the pulmonary artery catheter (PAC). The purposes of this study were to (1) compare the level of agreement and trending abilities of CO values measured using the fourth version of the FloTrac system (CCO-FloTrac) and PAC-originated continuous thermodilution (CCO-PAC) and (2) analyze the inadequate CO-discriminating ability of the FloTrac system before and after cardiopulmonary bypass (CPB). Fifty patients were included. After exclusion, 32 patients undergoing cardiac surgery with CPB were analyzed. All patients were monitored with a PAC and radial artery catheter connected to the FloTrac system. CO was assessed at 10 timing points during the surgery. In the Bland–Altman analysis, the percentage errors (bias, the limits of agreement) of the CCO-FloTrac were 61.82% (0.16, ??2.15 to 2.47 L min) and 51.80% (0.48, ??1.97 to 2.94 L min) before and after CPB, respectively, compared with CCO-PAC. The concordance rates in the four-quadrant plot were 64.10 and 62.16% and the angular concordance rates (angular mean bias, the radial limits of agreement) in the polar-plot analysis were 30.00% (17.62°, ??70.69° to 105.93°) and 38.63% (??10.04°, ??96.73° to 76.30°) before and after CPB, respectively. The area under the receiver operating characteristic curve for CCO-FloTrac was 0.56, 0.52, 0.52, and 0.72 for all, ≥?±?5, ≥?±?10, and ≥?±?15% CO changes (ΔCO) of CCO-PAC before CPB, respectively, and 0.59, 0.55, 0.49, and 0.46 for all, ≥?±?5, ≥?±?10, and ≥?±?15% ΔCO of CCO-PAC after CPB, respectively. When CO <?4 L/min was considered inadequate, the Cohen κ coefficient was 0.355 and 0.373 before and after CPB, respectively. The accuracy, trending ability, and inadequate CO-discriminating ability of the fourth version of the FloTrac system in CO monitoring are not statistically acceptable in cardiac surgery.     

Capnodynamic assessment of effective lung volume during cardiac output manipulations in a porcine model

A capnodynamic calculation of effective pulmonary blood flow includes a lung volume factor (ELV) that has to be estimated to solve the mathematical equation. In previous studies ELV correlated to reference methods for functional residual capacity (FRC). The aim was to evaluate the stability of ELV during significant manipulations of cardiac output (CO) and assess the agreement for absolute values and trending capacity during PEEP changes at different lung conditions. Ten pigs were included. Alterations of alveolar carbon dioxide were induced by cyclic reoccurring inspiratory holds. The Sulphur hexafluoride technique for FRC measurements was used as reference. Cardiac output was altered by preload reduction and inotropic stimulation at PEEP 5 and 12 cmH₂O both in normal lung conditions and after repeated lung lavages. ELV at baseline PEEP 5 was [mean (SD)], 810 (163) mL and decreased to 400 (42) mL after lavage. ELV was not significantly affected by CO alterations within the same PEEP level. In relation to FRC the overall bias (limits of agreement) was ?35 (?271 to 201) mL, and percentage error 36 %. A small difference between ELV and FRC was seen at PEEP 5 cmH₂O before lavage and at PEEP 12 cmH₂O after lavage. ELV trending capability between PEEP steps, showed a concordance rate of 100 %. ELV was closely related to FRC and remained stable during significant changes in CO. The trending capability was excellent both before and after surfactant depletion.     

Cardiac index assessment using bioreactance in patients undergoing cytoreductive surgery in ovarian carcinoma

This clinical study compared the cardiac index (CI) assessed by the totally non-invasive method of bioreactance (CI_BR) (NICOM?, Cheetah Medical, Vancouver, USA) to transpulmonary thermodilution (CI_TD) during cytoreductive surgery in ovarian carcinoma. The hypothesis was that CI could be assessed by bioreactance in an accurate and precise manner including accurate trending ability when compared to transpulmonary thermodilution. In 15 patients CI_BR and CI_TD were assessed after induction of anesthesia, after opening of the peritoneum, hourly during the operative procedure, and 30 min after extubation. Trending ability was assessed between the described timepoints. In total 84 points of measurement were analyzed. Concordance correlation coefficient for repeated measures correlating the CI_BR and CI_TD was 0.32. Bias was 0.26 l/min/m² (limits of agreement ?1.39 and 1.92 l/min/m²). The percentage error was 50.7 %. Trending ability quantified by the mean of angles θ which are made by the ΔCI vector and the line of identity (y = x) showed a value for CI_BR of θ = 23.4°. CI assessment by bioreactance showed acceptable accuracy and trending ability. However, its precision was poor. Therefore, CI measurement can not be solely based on bioreactance in patients undergoing cytoreductive surgery in ovarian carcinoma.     

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.     

An autocalibrating algorithm for non-invasive cardiac output determination based on the analysis of an arterial pressure waveform recorded with radial artery applanation tonometry: a proof of concept pilot analysis

We aimed to describe and evaluate an autocalibrating algorithm for determination of cardiac output (CO) based on the analysis of an arterial pressure (AP) waveform recorded using radial artery applanation tonometry (AT) in a continuous non-invasive manner. To exemplarily describe and evaluate the CO algorithm, we deliberately selected 22 intensive care unit patients with impeccable AP waveforms from a database including AP data obtained with AT (T-Line system; Tensys Medical Inc.). When recording AP data for this prospectively maintained database, we had simultaneously noted CO measurements obtained from just calibrated pulse contour analysis (PiCCO system; Pulsion Medical Systems) every minute. We applied the autocalibrating CO algorithm to the AT-derived AP waveforms and noted the computed CO values every minute during a total of 15 min of data recording per patient (3 × 5-min intervals). These 330 AT-derived CO (AT-CO) values were then statistically compared to the corresponding pulse contour CO (PC-CO) values. Mean ± standard deviation for PC-CO and AT-CO was 7.0 ± 2.0 and 6.9 ± 2.1 L/min, respectively. The coefficient of variation for PC-CO and AT-CO was 0.280 and 0.299, respectively. Bland–Altman analysis demonstrated a bias of +0.1 L/min (standard deviation 0.8 L/min; 95 % limits of agreement ?1.5 to 1.7 L/min, percentage error 23 %). CO can be computed based on the analysis of the AP waveform recorded with AT. In the selected patients included in this pilot analysis, a percentage error of 23 % indicates clinically acceptable agreement between AT-CO and PC-CO.     

Importance of re-calibration time on pulse contour analysis agreement with thermodilution measurements of cardiac output: a retrospective analysis of intensive care unit patients

We assessed the effect of re-calibration time on cardiac output estimation and trending performance in a retrospective analysis of an intensive care unit patient population using error grid analyses. Paired thermodilution and arterial blood pressure waveform measurements (N = 2141) from 222 patient records were extracted from the Multiparameter Intelligent Monitoring in Intensive Care II database. Pulse contour analysis was performed by implementing a previously reported algorithm at calibration times of 1, 2, 8 and 24 h. Cardiac output estimation agreement was assessed using Bland–Altman and error grid analyses. Trending was assessed by concordance and a 4-Quadrant error grid analysis. Error between pulse contour and thermodilution increased with longer calibration times. Limits of agreement were ?1.85 to 1.66 L/min for 1 h maximum calibration time compared to ?2.70 to 2.41 L/min for 24 h. Error grid analysis resulted in 74.2 % of points bounded by 20 % error limits of thermodilution measurements for 1 h calibration time compared to 65 % for 24 h. 4-Quadrant error grid analysis showed <75 % of changes in pulse contour estimates to be within ±80 % of the change in the thermodilution measurement at any calibration time. Shorter calibration times improved the agreement of cardiac output pulse contour estimates with thermodilution. Use of minimally invasive pulse contour methods in intensive care monitoring could benefit from prospective studies evaluating calibration protocols. The applied pulse contour analysis method and thermodilution showed poor agreement to monitor changes in cardiac output.     

Transesophageal Doppler reliably tracks changes in cardiac output in comparison with intermittent pulmonary artery thermodilution in cardiac surgery patients

In this study a comparison of cardiac output (CO) measurements obtained with CardioQ transesophageal Doppler (TED) and pulmonary artery catheter (PAC) thermodilution (TD) technique was done in a systematic set-up, with induced changes in preload, afterload and heart rate. Twenty-five patients completed the study. Each patient were placed in the following successive positions: (1) supine, (2) head-down tilt, (3) head-up tilt, (4) supine, (5) supine with phenylephrine administration, (6) pace heart rate 80 beats per minute (bpm), (7) pace heart rate 110 bpm. The agreement of compared data was investigated by Bland–Altman plots, and to assess trending ability a four quadrants plot and a polar plot were constructed. Both methods showed an acceptable precision 6.4 % (PAC TD) and 12.8 % (TED). In comparison with PAC TD, the TED was associated with a mean bias in supine position of ?0.30 l min^?1 (95 % CI ?0.88; 0.27), wide limits of agreement, a percentage error of 69.5 %, and a trending ability with a concordance rate of 92 %, angular bias of 1.1° and a radial sector size of 40.0° corresponding to an acceptable trending ability. In comparison with PAC TD, the CardioQ TED showed a low mean bias, wide limits of agreement and a larger percentage error than should be expected from the precision of the two methods. However, an acceptable trending ability was found. Thus, the CardioQ TED should not replace CO measurements done by PAC TD, but could be a valuable tool in guiding therapy.     

Comparison of electrical velocimetry and cardiac magnetic resonance imaging for the non-invasive determination of cardiac output

A novel algorithm of impedance cardiography referred to as electrical velocimetry (EV) has been introduced for non-invasive determination of cardiac output (CO). Previous validation studies yielded diverging results and no comparison with the non-invasive gold standard cardiac magnetic resonance imaging (CMR) has been performed. We therefore aimed to prospectively assess the accuracy and reproducibility of EV compared to CMR. 152 consecutive stable patients undergoing CMR were enrolled. EV measurements were taken twice before or after CMR in supine position and averaged over 20 s (AESCULON^®, Osypka Medical, Berlin, Germany). Bland–Altman analysis showed insufficient agreement of EV and CMR with a mean bias of 1.2 ± 1.4 l/min (bias 23 ± 26 %, percentage error 51 %). Reproducibility was high with 0.0 ± 0.3 l/min (bias 0 ± 8 %, percentage error 15 %). Outlier analysis revealed gender, height, CO and stroke volume (SV) by CMR as independent predictors for larger variation. Stratification of CO_CMR in quintiles demonstrated a good agreement for low values (<4.4 l/min) with bias increasing significantly with quintile as high as 3.1 ± 1.1 l/min (p < 0.001). Reproducibility was not affected (p = 0.71). Subgroup analysis in patients with arrhythmias (p = 0.19), changes in thoracic fluid content (p = 0.51) or left heart failure (p = 0.47) could not detect significant differences in accuracy. EV showed insufficient agreement with CMR and good reproducibility. Gender, height and increasing CO and SV were associated with increased bias while not affecting reproducibility. Therefore, absolute values should not be used interchangeably in clinical routine. EV yet may find its place for clinical application with further investigation on its trending ability pending.     

Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia

The capnodynamic method is a minimally invasive method continuously calculating effective pulmonary blood flow (CO_EPBF), equivalent to cardiac output when intra pulmonary shunt flow is low. The capnodynamic equation joined with a ventilator pattern containing cyclic reoccurring expiratory holds, provides breath to breath hemodynamic monitoring in the anesthetized patient. Its performance however, might be affected by changes in the mixed venous content of carbon dioxide (C_vCO₂). The aim of the current study was to evaluate CO_EPBF during rapid measurable changes in mixed venous carbon dioxide partial pressure (P_vCO₂) following ischemia–reperfusion and during sustained hypercapnia in a porcine model. Sixteen pigs were submitted to either ischemia–reperfusion (n?=?8) after the release of an aortic balloon inflated during 30 min or to prolonged hypercapnia (n?=?8) induced by adding an instrumental dead space. Reference cardiac output (CO) was measured by an ultrasonic flow probe placed around the pulmonary artery trunk (CO_TS). Hemodynamic measurements were obtained at baseline, end of ischemia and during the first 5 min of reperfusion as well as during prolonged hypercapnia at high and low CO states. Ischemia–reperfusion resulted in large changes in P_vCO₂, hemodynamics and lactate. Bias (limits of agreement) was 0.7 (?0.4 to 1.8) L/min with a mean error of 28% at baseline. CO_EPBF was impaired during reperfusion but agreement was restored within 5 min. During prolonged hypercapnia, agreement remained good during changes in CO. The mean polar angle was ?4.19° (?8.8° to 0.42°). Capnodynamic CO_EPBF is affected but recovers rapidly after transient large changes in P_vCO₂ and preserves good agreement and trending ability during states of prolonged hypercapnia at different levels of CO.     

Agreement in hemodynamic monitoring during orthotopic liver transplantation: a comparison of FloTrac/Vigileo at two monitoring sites with pulmonary artery catheter thermodilution

To study agreement in cardiac index (CI), systemic vascular resistance index (Systemic VRI) and stroke volume variation (SV variation) between the FloTrac/Vigileo at radial and femoral arterial cannulation sites, and pulmonary artery catheter (PAC) thermodilution, in patients undergoing orthotopic liver transplantation. A prospective observational study of 25 adult patients with liver failure. Radial and femoral arteries were cannulated with standardised FloTrac/Vigileo arterial transducer kits and a PAC was inserted. CI, SV variation and Systemic VRI were measured four times (30 min after induction of anesthesia, 30 min after portal vein clamping, 30 min after graft reperfusion, 30 min after commencement of bile duct anastomosis). The bias, precision, limits of agreement (LOA) and percentage errors were calculated using Bland–Altman statistics to compare measurements from radial and femoral arterial cannulation sites and PAC thermodilution. Neither radial nor femoral CI achieved acceptable agreement with PAC CI [radial to PAC bias (SD) 1.17 (1.49) L/min/m², percentage error 64.40 %], [femoral to PAC bias (SD) ?0.71 (1.81) L/min/m², percentage error 74.20 %]. Agreement between radial and femoral sites for CI [mean difference (SD) ?0.43 (1.51) L/min/m², percentage error 70.40 %] and Systemic VRI [mean difference (SD) 0.03 (4.17) LOA ±8.17 mmHg min m²/L] were also unacceptable. Agreement in SV variation between radial and femoral measurement sites approached a clinically acceptable threshold [mean difference (SD) 0.68 (2.44) %), LOA ±4.78 %]. FloTrac/Vigileo CI cannot substitute for PAC thermodilution CI, regardless of measurement site. SV variation measurements may be interchangeable between radial and femoral sites for determining fluid responsiveness.     

Evaluation of the estimated continuous cardiac output monitoring system in adults and children undergoing kidney transplant surgery: a pilot study

Evaluation of the estimated continuous cardiac output (esCCO) allows non-invasive and continuous assessment of cardiac output. However, the applicability of this approach in children has not been assessed thus far. We compared the correlation coefficient, bias, standard deviation (SD), and the lower and upper 95 % limits of agreement for esCCO and dye densitography-cardiac output (DDG-CO) measurements by pulse dye densitometry (PDD) in adults and children. On the basis of these assessments, we aimed to examine whether esCCO can be used in pediatric patients. DDG-CO was measured by pulse dye densitometry (PDD) using indocyanine green. Modified-pulse wave transit time, obtained using pulse oximetry and electrocardiography, was used to measure esCCO. Correlations between DDG-CO and esCCO in adults and children were analyzed using regression analysis with the least squares method. Differences between the two correlation coefficients were statistically analyzed using a correlation coefficient test. Bland–Altman plots were used to evaluate bias and SD for DDG-CO and esCCO in both adults and children, and 95 % limits of agreement (bias ± 1.96 SD) and percentage error (1.96 SD/mean DDG-CO) were calculated and compared. The average age of the adult patients (n = 10) was 39.3 ± 12.1 years, while the average age of the pediatric patients (n = 7) was 9.4 ± 3.1 years (p < 0.001). For adults, the correlation coefficient was 0.756; bias, ?0.258 L/min; SD, 1.583 L/min; lower and upper 95 % limits of agreement for DDG-CO and esCCO, ?3.360 and 2.844 L/min, respectively; and percentage error, 42.7 %. For children, the corresponding values were 0.904; ?0.270; 0.908; ?2.051 and 1.510 L/min, respectively; and 35.7 %. Due to the high percentage error values, we could not establish a correlation between esCCO and DDG-CO. However, the 95 % limits of agreement and percentage error were better in children than in adults. Due to the high percentage error, we could not confirm a correlation between esCCO and DDG-CO. However, the agreement between esCCO and DDG-CO seems to be higher in children than in adults. These results suggest that esCCO can also be used in children. Future studies with bigger study populations will be required to further investigate these conclusions.     

Estimation of pulse pressure variation and cardiac output in patients having major abdominal surgery: a comparison between a mobile application for snapshot pulse wave analysis and invasive pulse wave analysis

Pulse pressure variation (PPV) and cardiac output (CO) can guide perioperative fluid management. Capstesia (Galenic App, Vitoria-Gasteiz, Spain) is a mobile application for snapshot pulse wave analysis (PWAsnap) and estimates PPV and CO using pulse wave analysis of a snapshot of the arterial blood pressure waveform displayed on any patient monitor. We evaluated the PPV and CO measurement performance of PWAsnap in adults having major abdominal surgery. In a prospective study, we simultaneously measured PPV and CO using PWAsnap installed on a tablet computer (PPV_PWAsnap, CO_PWAsnap) and using invasive internally calibrated pulse wave analysis (ProAQT; Pulsion Medical Systems, Feldkirchen, Germany; PPV_ProAQT, CO_ProAQT). We determined the diagnostic accuracy of PPV_PWAsnap in comparison to PPV_ProAQT according to three predefined PPV categories and by computing Cohen’s kappa coefficient. We compared CO_ProAQT and CO_PWAsnap using Bland-Altman analysis, the percentage error, and four quadrant plot/concordance rate analysis to determine trending ability. We analyzed 190 paired PPV and CO measurements from 38 patients. The overall diagnostic agreement between PPV_PWAsnap and PPV_ProAQT across the three predefined PPV categories was 64.7% with a Cohen’s kappa coefficient of 0.45. The mean (±?standard deviation) of the differences between CO_PWAsnap and CO_ProAQT was 0.6?±?1.3 L min^??1 (95% limits of agreement 3.1 to ??1.9 L min^??1) with a percentage error of 48.7% and a concordance rate of 45.1%. In adults having major abdominal surgery, PPV_PWAsnap moderately agrees with PPV_ProAQT. The absolute and trending agreement between CO_PWAsnap with CO_ProAQT is poor. Technical improvements are needed before PWAsnap can be recommended for hemodynamic monitoring.

     

Cross-comparisons of trending accuracies of continuous cardiac-output measurements: pulse contour analysis,bioreactance, and pulmonary-artery catheter

We compared the similarity of cardiac-output (CO) estimates between available bolus thermodilution pulmonary-artery catheters (PAC), arterial pulse-contour analysis (LiDCOplus^?, FloTrac^? and PiCCOplus^?), and bioreactance (NICOM^?). Repetitive simultaneous estimates of CO obtained from the above devices were compared in 21 cardiac-surgery patients during the first 2 h post-surgery. Mean and absolute values for CO across the devices were compared by ANOVA, Bland–Altman, Pearson moment, and linear-regression analyses. Twenty-one simultaneous CO measurements were made before and after therapeutic interventions. Mean PAC CO (5.7?±?1.5 L min) was similar to LiDCO^?, FloTrac^?, PiCCO^?, and NICOM^? CO (6.0?±?1.9, 5.9?±?1.0, 5.7?±?1.8, 5.3?±?1.0 L min, respectively). Mean CO bias between each paired method was ?0.10 (PAC–LiDCO), 0.18 (PAC–PiCCO), ?0.40 (PAC–FloTrac), ?0.71 (PAC–NICOM), 0.28 (LiDCO–PiCCO), 0.39 (LiDCO–FloTrac), ?0.97 (NICOM–LiDCO), 0.61 (PiCCO–FloTrac), ?1.0 (NICOM–FloTrac), ?0.73 (NICOM–PiCCO) L/min, with limits of agreement (1.96 SD, ±95% CI) of ±?2.01, ±2.35, ±2.27, ±2.70, ±1.97, ±2.17, ±3.51, ±2.87, ±2.40, and ±?3.14 L min, respectively, and the percentage error for each of the paired devices was 35, 41, 40, 47, 33, 36, 59, 50, 42, and 55%, respectively. From Pearson moment analysis, dynamic changes in CO, estimated by each device, showed good cross-correlations. Although all devices studied recorded similar mean CO values, which dynamically changed in similar directions, they have markedly different bias and precision values relative to each other. Thus, results from prior studies that have used one device to estimate CO cannot be used to validate others devices.     

Reliability of cardiac output measurements using LiDCOrapid™ and FloTrac/Vigileo™ across broad ranges of cardiac output values

Knowing a patient’s cardiac output (CO) could contribute to a safe, optimized hemodynamic control during surgery. Precise CO measurements can serve as a guide for resuscitation therapy, catecholamine use, differential diagnosis, and intervention during a hemodynamic crisis. Despite its invasiveness and intermittent nature, the thermodilution technique via a pulmonary artery catheter (PAC) remains the clinical gold standard for CO measurements. LiDCOrapid? (LiDCO, London, UK) and FloTrac/Vigileo? (Edwards Lifesciences, Irvine, CA) are less invasive continuous CO monitors that use arterial waveform analysis. Their calculations are based on arterial waveform characteristics and do not require calibration. Here, we evaluated LiDCOrapid? and FloTrac/Vigileo? during off-pump coronary artery bypass graft (OPCAB) and living-donor liver transplantation (LDLT) surgery. This observational, single-center study included 21 patients (11 OPCAB and 10 LDLT). We performed simultaneous measurements of CO at fixed sampling points during surgery using both devices (LiDCOrapid? version 1.04-b222 and FloTrac/Vigileo? version 3.02). The thermodilution technique via a PAC was used to obtain the benchmark data. LiDCOrapid? and FloTrac/Vigileo? were used in an uncalibrated fashion. We analyzed the measured cardiac index using a Bland–Altman analysis (the method of variance estimates recovery), a polar plot method (half-moon method), a 4-quadrant plot and compared the widths of the limits of agreement (LOA) using an F test. One OPCAB patient was excluded because of the use of an intra-aortic balloon pumping during surgery, and 20 patients (10 OPCAB and 10 LDLT) were ultimately analyzed. We obtained 149 triplet measurements with a wide range of cardiac index. For the FloTrac/Vigileo?, the bias and percentage error were ?0.44 L/min/m² and 74.4 %. For the LiDCOrapid?, the bias and percentage error were ?0.38 L/min/m² and 53.5 %. The polar plot method showed an angular bias (FloTrac/Vigileo? vs. LiDCOrapid?: 6.6° vs. 5.8°, respectively) and radial limits of agreement (?63.9 to 77.1 vs. ?41.6 to 53.1). A 4-quadrant plot was used to obtain concordance rates (FloTrac/Vigileo? vs. PAC and LiDCOrapid? vs. PAC: 84.0 and 92.4 %, respectively). We could compare CO measurement devices across broad ranges of CO and SVR using LDLT and OPCAB surgical patients. An F test revealed no significant difference in the widths of the LoA for both devices when sample sizes capable of detecting a more than two-fold difference were used. We found that both devices tended to underestimate the calculated CIs when the CIs were relatively high. These proportional bias produced large percentage errors in the present study.