Noninvasive Measurement Of Cardiac Output Research Articles

Further Studies Should Evaluate Cardiac Output Measurement by the Nexfin Device

We read the article “Is Arterial Pulse Contour Analysis (PCA) Using Nexfin a New Option in the Noninvasive Measurement of Cardiac Output? —A Pilot Study” by Trinkmann et al1 with great interest. They aimed to evaluate the accuracy and precision of noninvasive cardiac output (CO) measurements using the new digital photoplethysmographic device (Nexfin, BMEYE, Amsterdam, The Netherlands) compared with cardiac magnetic resonance imaging (CMR). They reported that the noninvasive PCA allows the safe and economic measurement of CO, yet it still has major limitations.

Usefulness of a noninvasive cardiac output measurement using pulse wave transit time in coronary care unit

In coronary care unit, assessment of cardiac output may be of importance, especially in patients presenting with unstable hemodynamic [1,2]. Thermodilution method is the gold standard [1], but is invasive and now less frequently performed. In routine practice, cardiac output is assessed by echocardiography [3], but may be difficult because of the need of several measurements. Previous echocardiographic automated cardiac output or new echocardiographic methods have been validated, but are not widely used [1,4].

Rest and latent obstruction in hypertrophic cardiomyopathy

Most patients with hypertrophic cardiomyopathy (HCM) show a limited exercise capacity. A correlation between exercise tolerance and diastolic dysfunction has already been demonstrated. On the contrary, the role of rest-induced or exercise-induced obstruction as a determinant of exercise capacity is still open to debate. The aim of the present study was to analyse the exertional behaviour of patients with HCM presenting different left ventricle (LV) obstructive profiles. Thirty-five consecutive patients with HCM (mean age 45 ± 14 years, 23 men) underwent echocardiography during cardiopulmonary exercise (CPX) testing. Non-invasive measurement of cardiac output was obtained with an inert gas rebreathing system at the beginning and at peak of exercise. Fifteen patients (43%) had neither resting nor provocable obstruction (group A: non-obstructive profile), 12 patients (34%) showed provocable obstruction during exercise (group B: latent-obstructive profile) and eight patients (23%) presented obstruction at rest (group C: rest-obstructive profile). Group A and B patients showed higher peak oxygen consumption in comparison with group C patients (24 ± 6 and 23 ± 6 vs. 17 ± 3 ml/kg per min; P = 0.016) and a greater increment of cardiac index during exercise (6.6 ± 1.3 and 6.0 ± 1.4 vs. 4.6 ± 0.8 l/min per m; P = 0.004). In comparison with the rest-obstructive profile, latent and non-obstructive HCM patients seem to share a similar exertional behaviour characterized by a greater increment of cardiac index during exercise and a minor impairment of exercise tolerance. Accordingly, in HCM patients not obstructive at rest, latent obstruction cannot be suspected based on exertional behaviour and functional capacity. Echocardiography performed during CPX test providing an important adjunct, may be valuable in guiding treatment in patients with substantial exercise limitation.

Characteristics of heart, arteries, and veins in low and high cardiac output preeclampsia

ObjectiveTo assess the feasibility of non-invasive measurements of maternal cardiac output in relation to birth weight percentile and cardiovascular physiology in preeclampsia. Study designIn a cohort of 62 women with preeclampsia, impedance cardiography was used to measure cardiac output and to evaluate heart and arteries. Venous characteristics were assessed by combined electrocardiogram-Doppler ultrasonography. Statistical differences were evaluated by Mann–Whitney U-tests. ResultsCardiac output correlated with birth weight percentile (P=.002), with more small for gestational age newborns in low cardiac output preeclampsia (<7.5L/min) than in high cardiac output preeclampsia (≥8.9L/min) (12/29 vs. 2/16, P=.044). This was associated with lower aortic flow indices and shorter venous pulse transit times in low than in high cardiac output preeclampsia. ConclusionNon-invasive impedance cardiography measurements of maternal cardiac output correlate with birth weight percentile and are associated with different functionality of heart, arteries, and veins in low and high cardiac output preeclampsia.

Noninvasive Assessment of Acute Dyspnea in the ED

Background:We compared the ability of noninvasive measurements of cardiac output (CO) and thoracic fluid content (TFC) and their change in response to orthostatic challenges to diagnose acute decompensate heart failure (ADHF) from non-ADHF causes of acute dyspnea in patients in the ED.Methods:Forty-five patients > 44 years old presenting in the ED with dyspnea were studied. CO and TFC were monitored with a NICOM bioreactance device. CO and TFC were measured continuously while each patient was sitting, supine, and during a passive leg-raising maneuver (3 min each); the maximal values during each maneuver were reported. Orthostatic challenges were repeated 2 h into treatment. One patient was excluded because of intolerance to the supine position. Diagnoses obtained with the hemodynamic measurements were compared with ED diagnoses and with two expert physicians by chart review (used as gold standard diagnosis); both groups were blinded to CO and TFC values. Patient’s treatment, ED disposition, hospital length of stay, and subjective dyspnea (Borg scale) were also recorded.Results:Sixteen of 44 patients received a diagnosis of ADHF and 28 received a diagnosis of non-ADHF by the experts. Baseline TFC was higher in patients with ADHF (P = .001). Fifteen patients were treated for ADHF, and their Borg scale values decreased at 2 h (P < .05). TFC threshold of 78.8 had a receiver operator characteristic area under the curve of 0.81 (76% sensitivity, 71% specificity) for ADHF. Both ADHF and non-ADHF groups were similar in their increased CO from baseline to PLR and supine. Pre- and posttreatment measurements were similar.Conclusions:Baseline TFC can discriminate patients with ADHF from non-ADHF dyspnea in the ED.

Noninvasive and Simple Assessment of Cardiac Output and Pulmonary Vascular Resistance With Whole-Body Impedance Cardiography Is Useful for Monitoring Patients With Pulmonary Hypertension

Right heart catheterization (RHC) is the gold standard for the diagnosis of pulmonary hypertension (PH) and a useful tool for monitoring PH. However, there are some disadvantages in the regular use of RHC because it is invasive. Noninvasive methods for monitoring hemodynamics are needed to manage patients with PH. In this study, we aimed to evaluate the reliability of noninvasive hemodynamic assessment with whole-body impedance cardiography (Non-Invasive Cardiac System [NICaS]) for PH. We investigated 65 consecutive patients undergoing RHC. Two-thirds of them had pulmonary arterial hypertension and one-third had chronic thromboembolic PH; 25% of the patients were receiving medical therapy. Cardiac output (CO) was estimated by NICaS (NI-CO), thermodilution (TD-CO), and the Fick method (Fick-CO). There was a strong correlation between NI-CO and TD-CO (r=0.715, P<0.0001) and Fick-CO (r=0.653, P<0.0001). Noninvasive pulmonary vascular resistance (PVR) was estimated using a conventional invasive equation with NI-CO, mean pulmonary arterial pressure was calculated by echocardiographic measurement, and pulmonary capillary wedge pressure was estimated at 10mmHg in all cases. NICaS-derived PVR was very strongly correlated with invasive PVR (TD-PVR: r=0.704, P<0.0001; Fick-PVR: r=0.702, P<0.0001). Noninvasive measurement of CO and PVR using NICaS and echocardiography is a useful tool for the assessment of PH.

A dye densitometry analysis method for noninvasive measurement of cardiac output based on NIRS

Currently, there exist technology problems in cardiac output (CO) parameter detection clinically, such as invasive and complex operation, as well as possibility of infection and death for patients. In order to solve these problems, a noninvasive and continuous method based on NIRS for CO detection was presented. In this way, the concentration changing of indocyanine green (ICG) dye in the patient's arterial blood was dynamically measured and analyzed, so that the CO could be noninvasively and continuously measured according to the characteristic parameters of dye densitometry curve. While the ICG dye was injected into the patient's body by the median cubital vein, block of photoelectric pulse dye densitometry measurement system as the lower machine acquired pulse wave data and uploaded the data to upper computer. In the scheme, two specialized light sources of LED at 940 and 805 nm were used to capture the signals of sufferer's fingertip pulse wave synchronously and successively. The CO value could then be successfully calculated through drawing complete ICG concentration variation of dye dilution and excretion process and computing mean transmission time (MTT) by upper computer. Compared with the "gold standard" method of thermodilution, the maximum relative error of this method was below 9. 76%, and the mean relative error was below 4. 39%. The result indicates that the method can be used as a kind of convenient operation, noninvasive and continuous solution for clinical CO measurement.

260: Cognitive performance, cerebral oxygenation, exercise capacity and cardiac output in patients with coronary heart disease

Recent data suggested that coronary heart disease (CHD) is associated with non-amnesic mild cognitive impairment. Our purpose was to assess cognitive performances at rest, VO2max, cardiac output (CO), and cerebral hemodynamic changes during maximal exercise in patients with stable CHD. 22 stable fit CHD patients (70,9±9,3 years), 10 healthy age-matched (68,6±8,6 years), 10 middle aged controls and 10 young controls (< 40y) were included. We assessed cognitive performance with a standard battery of paper and pencil tests, maximal exercise test on ergocycle with gas exchange analysis with non-invasive CO measurement and Near-Infrared Spectroscopy (NIRS) oxygenation indices at the brain level. There was no intergroup difference in VO2max or maximal CO between cardiac and healthy age-matched individuals. Some cognitive tests, especially for executive functioning, were significantly better for the healthy matched group (Trail Making Test-B; Inhibition/Flexibility Stroop Task and Backward Digit Span, p<0.05). For NIRS signals, we observed an increase in deoxyhemoglobin (HHb) for maximal intensities and the classical inverted U-shape curve for oxyhemoglobin (O2Hb) and hemoglobin difference (Hbdiff=O2Hb-HHb) in each group. Considering fitness, intra-CHD group differences were observed with lower amplitudes in HHb signalss for less fit subjects. In control groups, middle aged and young subjects had significant higher performances in VO2max, most of cognitive tests and higher amplitudes changes for NIRS indices while exercising. Despite comparable maximal exercise tolerances and CO, CHD individuals presented reduced cognitive performances compared to healthy age-matched subjects. We evidenced an inter-individual variability among CHD patients for cerebral NIRS signals changes, especially with age and fitness. These results suggest that variations in HHb are much more related to exercise capacity than O2Hb in CHD patients.

Effect of Postural Challenges on Non-invasive Cardiac Output Measurement with Impedance Cardiography in Young Healthy Adults Using New Horizontal Electrode Placement Method.

Background: Cardiac output is an important hemodynamic parameter of cardiovascular system and a significant indicator of autonomic function status of a person. It can be measured invasively as well as non-invasively. Imepdance cardiography (ICG) is a promising, new, noninvasive technique to measure cardiac output. There are no studies noninvasively measuring cardiac output in healthy subject by impedance cardiography using new horizontal method of electrode placement during postural challenges. Objective: We observed effect of postural challenges on noninvasive cardiac output measurement using ICG by new horizontal electrode placement method. Methods: Cardiac output (CO), stroke volume (SV) and cardiac index (CI), were measured noninvasively, before and after postural challenges namely Head Up Tilt (HUT) of 700 and Head Down Tilt (HDT) 200, in 38 healthy male subjects (mean age-28 yrs, range 22-34 yrs). Results: After 700 HUT the values of CO, SV and CI decreased by 1.5±0.9 l/min (31%), 25.8±11.4 ml (37%), & 0.8±0.4 l/min/m2 (27 %), respectively. HDT did not cause significant change in theses hemodynamic parameters. Conclusion: ICG successfully detected physiological changes in cardiac output following postural challenges using new horizontal electrode placement method. The study underscores utility of this simple noninvasive tool for hemodynamic assessment after postural challenge using new horizontal electrode placement method.

Non-invasive measurement of cardiac output in obese children and adolescents: comparison of electrical cardiometry and transthoracic Doppler echocardiography

The objective of this study was to evaluate the reliability and accuracy of electrical cardiometry (EC) for the noninvasive determination of cardiac output (CO) in obese children and adolescents. We compared these results with those obtained by transthoracic echocardiography. Sixty-four participants underwent simultaneous measurement of CO. Cardiac output was measured by EC using the ICON(®) device. Simultaneously CO was determined by using transthoracic Doppler echocardiography from parasternal long-axis and apical view. The median age was 12.52years (range 7.9-17.6years) and 36 (56%) were female. A strongly significant correlation was found between the COEC and COEcho measurements (p<0.0001, r=0.91). Significant correlations were also found between CO and age (r=0.37, p=0.002), weight (r=0.57, p<0.0001), height (0.60, p<0.0001) and BMI (r=0.42, p=0.001). The mean difference between the two methods (COEC-COEcho) was 0.015lmin(-1). According to the Bland and Altman method, the upper and lower limits of agreement, defined as mean difference ±2SD, were +1.21 and -0.91lmin(-1), respectively. Compared to the transthoracic Doppler echocardiography, Electrical Cardiometry provides accurate and reliable CO measurements in obese children and adolescents.

Abstract 94: Is the Impedance Cardiogram a Potential Indicator of Effective External Cardiac Massage in a Human Model? A Study to Establish If There Is a Linear Correlation Between the Impedance Cardiogram and Depth in a Cardiac Arrest Setting

Purpose of the Study: The 2010 AHA guidelines currently recommend a depth of at least 2 inches (5cm) during external cardiac massage. The purpose of this study was to assess the hypothesis that if using an alternative measure to depth could assist in quantifying the effectiveness of CPR in an out-of-hospital setting and to determine how achievable depths of at least 2 inches are in cardiac arrest patients. Materials and Methods: A total of 32 cardiac arrest patients were recruited by EMS operators in Belfast and cardiologists in Craigavon Area Hospital (CAH). Patient baseline characteristics are summarised below in the results section. A subset of the patients enrolled had simultaneous recordings of Impedance Cardiogram (ICG) and depth (mm) during CPR. The Impedance Cardiogram (ICG)/Thoracic Impedance (non-invasive measure of cardiac output) was recorded via 2 standard defibrillation electrodes, as a method of detecting the presence of effective CPR. Ethical approval was granted by Ethical Committee Northern Ireland and the study was conducted in accordance with ISO 14155:2011; GCP standards. Depth and rate of CPR were continuously measured using Q-CPR ® , Philips. CPR was administered manually by trained ALS operators. Recordings from each experiment were acquired using Philips Q-CPR review software and HeartSine download software for statistical analysis using R ® . Results: Patients were aged between 32 and 93 years (mean 77 years), 64% of this cohort was male. Excluding cases CPR traces with excessive motion artefact, a total of 1883 compressions were administered in patients with a mean weight of 73.85kg. The mean compression depth achieved was 1.79 inches. A strong linear correlation was achieved between depth (mm) using Q-CPR ® and the Impedance cardiogram (ICG)/ thoracic impedance (ohms); r=0749. Conclusions: It can be concluded that a depth of 2 inches is difficult to achieve both in-hospital and by EMS operators even with the support of real-time CPR feedback. An algorithm will incorporate the results from this study, providing feedback to the operator on the quality of CPR by measuring the ICG amplitude which has been strongly correlated with standard measures of depth as well as a number of physiological parameters.

Validation of the Innocor Device for Noninvasive Measurement of Oxygen Consumption in Children and Adults

Outpatient measurements of oxygen consumption (VO2) and cardiac output (CO) are valuable in the management of pediatric cardiac disease. Current methods are inaccurate and cumbersome or require invasive procedures. New devices to measure these variables in adults have not been rigorously tested for children. The Innocor system uses a photoacoustic analyzer to measure gas content for noninvasive measurement of VO2 and CO. This study sought to validate Innocor-derived VO2 measurements in children and adults by comparing them against the gold standard Douglas bag method. Subjects were tested in an outpatient setting. Adaptations were made for pediatric patients based on weight. Resting VO2 measurements were obtained simultaneously by the Innocor system and Douglas bag during 3 min. The study enrolled 31 children (mean age, 12.2 years; range, 7-17 years, 17 girls) and 29 adults (mean age, 36.7 years; range, 19-57 years; 17 women). Strong correlation between the two techniques was seen for both the adults (R (2) = 0.88) and the children (R (2) = 0.82). The average discrepancy between the Innocor and Douglas bag measurements was 1.7 % (range, 0.6-19.1 %) for the adults, and 5.4 % (range, 0.1-32.2 %) for the children. The discrepancy was more than 15 % for 17 % of the adults and 22 % of the children, with the Innocor device tending to overestimate VO2 in children compared with the Douglas bag. This trend was not seen in adults. The Innocor system has excellent correlation with the Douglas bag and shows promise for noninvasive measurement of VO2 and CO in the school-age pediatric population.

Noninvasive cardiac output measurements in patients with pulmonary hypertension

Pulmonary hypertension (PH) is characterised by a progressive decline in cardiac output (CO) and right heart failure. NICOM® (noninvasive cardiac output monitor) is a bioreactance-based technology that has been broadly validated, but its specific application in right heart failure and PH is unknown. Cardiac catheterisation was performed in 50 consecutive patients with PH. CO measurements were performed using three different methods (thermodilution, Fick and NICOM) at baseline and after vasodilator challenge. We compared the precision (coefficient of variation) and accuracy of NICOM compared to thermodilution and Fick. The mean CO (L·min(-1)) at baseline as measured by the three methods was 4.73±1.15 (NICOM), 5.69±1.74 (thermodilution) and 4.84±1.39 (Fick). CO measured by NICOM was more precise than by thermodilution (3.5±0.3% versus 9.6±6.1%, p<0.001). Bland-Altman analyses comparing NICOM to thermodilution and Fick revealed bias and 95% limits of agreement that were comparable to those comparing Fick to thermodilution. All three CO methods detected an increase in CO in response to vasodilator challenge. CO measured via NICOM is precise and reliably measures CO at rest and changes in CO with vasodilator challenge in patients with PH. NICOM may allow for the noninvasive haemodynamic assessment of patients with PH and their response to therapy.

Short- and long-term effect of an aerobic training programme on gait parameters in the chronic hemiplegic patient

blood analysis, cognitive performances, maximal exercise tolerance with gas exchange analysis, non-invasive cardiac output measurement and Near-Infrared Spectroscopy (NIRS) cerebral signals were measured before and after training. Results.–We found significant improvements in maximal power and VO2max, a decrease in maximal heart rate without other hemodynamic changes. Weight, BMI, fat mass, and waist circumference significantly decreased (P < 0.01), whereas no effects on biological parameters, nor on muscle mass were observed. Some cognitive tests for executive functions (Digit Symbol Substitution Test, P < 0.01; Digit span, P < 0.05) and memory (Rey Auditory Verbal Learning Test, P = 0.03) significantly improved. Regarding the kinetics of the NIRS signals during exercise, both deoxyhemoglobin (HHb) and hemoglobin difference between oxyand deoxyhemoglobin (HbDiff) had higher amplitudes after training (P < 0.05). Conclusion.– In addition to improvements in exercise tolerance, a program combining HIIT and resistance training could improve executive functions in overweight adults. These results were associated with changes in cerebral oxygenation measured using NIRS.

382 Effects of a 4-Months High-Intensity Interval Training Associated With Resistance Training Program on Cognitive Performance, Cerebral Oxygenation, Exercise Capacity and Cardiac Output in Middle-Aged Overweight Subjects: A Pilot Study

382 Effects of a 4-Months High-Intensity Interval Training Associated With Resistance Training Program on Cognitive Performance, Cerebral Oxygenation, Exercise Capacity and Cardiac Output in Middle-Aged Overweight Subjects: A Pilot Study

749 Cognitive Performance, Cerebral Oxygenation, Exercise Capacity and Cardiac Output in Patients with Coronary Heart Disease

Recent data suggested that coronary heart disease (CHD) was associated with non-amnesic mild cognitive impairment. The purpose of our study was to assess cognitive performances at rest, VO2max, cardiac output, and cerebral hemodynamic changes during maximal exercise in patients with stable CHD. 22 stable fit CHD patients (70,9 ± 9,3 years), 10 healthy age-matched (68,6 ± 8,6 years), 10 middle aged controls and 10 young controls (< 40ans) were included. We assessed cognitive performance with a standard battery of pen and paper tests, maximal exercise test on ergocycle with gas exchange analysis with non-invasive cardiac output measurement and Near-Infrared Spectroscopy (NIRS) oxygenation indices at the brain level. There was no intergroup difference in VO2max or maximal cardiac output between cardiac and healthy age-matched individuals. Some cognitive tests, especially for executive functioning, were significantly better for the healthy matched group (Trail Making Test-B ; Inhibition/Flexibility Stroop Task and Backward Digit Span p < 0.05). For NIRS signals, we observed an increase in deoxyhemoglobin (hHb) for maximal intensities and the classical inverted U-shaped curves for oxyhemoglobin (O2Hb) and hemoglobin difference (Diff Hb=O2Hb-HHb) in each group. About fitness, intra-CHD group differences were observed with higher amplitudes in hHb changes for fit CHD subjects. In control groups, middle aged and young subjects had significant higher performances in VO2max, most of cognitive tests and higher amplitudes changes for NIRS indices while exercising. In spite of comparable maximal exercise tolerances and cardiac outputs, CHD individuals presented some reduced cognitive performances compared to healthy age-matched subjects. We also found an inter-individual variability among CHD patients for cerebral NIRS signals changes especially with age and fitness. These results suggest that variations in deoxyhemoglobin are much more related to exercise capacity than oxyhemoglobin, especially in CHD patients.

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

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

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of cardiac output

Study ObjectivesTo compare the Nexfin cardiac output (CO) with the CO obtained from transthoracic Doppler echocardiography (TTE) during routine cardiac function screening. DesignObservational clinical study. SettingEchocardiography laboratory. Patients40 ASA physical status 1 and 2 patients scheduled for routine TTE examination. InterventionsNone. Measurements and Main ResultsIn 40 patients scheduled for routine TTE examination, we obtained simultaneous CO measurements with Doppler ultrasound and derived from Nexfin blood pressure measurements. Correlation and level of agreement between Nexfin and TTE were analyzed using Pearson correlation coefficient and Bland-Altman plots. The Pearson correlation coefficient for Nexfin versus TTE was 0.68 (CI: 0.46 - 0.82, P < 0.0001). Bland-Altman analysis showed a bias of 0.51 ± 1.1 L/min and limits of agreement of -1.6 to 2.6 L/min, with a percentage error of 39%. ConclusionsConsidering limits of precision of CO measurements with Doppler echocardiography (± 30%), the agreement between noninvasive CO measurement with the Nexfin and TTE is reasonable.

Comparison of noninvasive cardiac output measurements using the Nexfin monitoring device and the esophageal Doppler

Study ObjectiveTo evaluate the validity of cardiac output (CO) measurements obtained using the Nexfin device in comparison to those obtained with the esophageal Doppler in steady-state conditions and after phenylephrine administration. DesignProspective observational study. SettingOperating room of a North American academic medical center. Patients25 ASA physical status 1, 2, and 3 patients referred for abdominal or orthopedic surgeries. InterventionsAfter endotracheal intubation, patients who presented with a 20% or greater decrease in mean arterial pressure (MAP) received an intravenous (IV) bolus of 100 μg of phenylephrine. If MAP was still 20% lower than the patient's baseline level at least 10 minutes after the first vasopressor treatment, a second bolus of 100 μg of phenylephrine was given. MeasurementsCO was measured simultaneously by esophageal Doppler (COED) and Nexfin (CONXF) at baseline and when blood pressure peaked after an IV 100 μg phenylephrine bolus. Comparisons were then made between the two devices to evaluate the ability of the Nexfin device to track changes in CO. Main Results66 pairs of data were obtained. Mean COED and CONXF were 4.7 ± 1.8 L/min and 5.6 ± 2.0 L/min, respectively. There was a significant relationship between COED and CONXF (r2 = 0.82; P < 0.001). The agreement between COED and CONXF was 0.88 ± 0.86 L/min (Bland Altman). The mean percent error (Critchley and Critchley) of CONXF versus COED was 37%. Trending analysis found a 94% concordance between changes in COED and CONXF after phenylephrine administration. ConclusionsIntraoperative CO measurement using the Nexfin device has a strong correlation with CO measured by esophageal Doppler.

Eversion Carotid Endarterectomy is Associated with Decreased Baroreceptor Sensitivity Compared to the Conventional Technique

ObjectiveImpairment of baroreceptor sensitivity (BRS) has been shown to be associated with blood pressure instability after carotid endarterectomy (CEA). The aim of this study was to determine whether there is a difference in postoperative BRS changes following eversion CEA (E-CEA) and conventional CEA (C-CEA). MethodsSixty-four patients undergoing E-CEA (n = 37) and C-CEA (n = 27) were prospectively studied. Non-invasive measurements of mean arterial pressure (MAP), cardiac output (CO) and total peripheral resistance (TPR) were perioperatively obtained over three 10-min periods. Baroreflex gain was calculated as the sequential cross-correlation between heart rate and beat-to-beat systolic blood pressure. ResultsCompared with changes observed after C-CEA, E-CEA was associated with an increase in systolic pressure (SP) (P = 0.01), diastolic pressure (DP) (P = 0.008), MAP (P = 0.002) and heart rate (HR) (P = 0.03) on postoperative day 1 (POD-1). BRS decreased after E-CEA from 6.33 to 4.71 ms mmHg−1 on POD-1 (P = 0.001) and to 5.26 ms mmHg−1 on POD-3 (P = 0.0004). By contrast, BRS increased after C-CEA from 4.59 to 6.13 ms mmHg−1 on POD-1 (P = 0.002) and to 6.27 ms mmHg−1 on POD-3 (P < 0.0001). ConclusionE-CEA and C-CEA have different effects on BRS. This is associated with an altered haemodynamic behaviour after E-CEA and C-CEA, respectively. These findings are likely the result of carotid sinus nerve interruption during E-CEA and preservation with C-CEA.