Method For Measurement Of Cardiac Output Research Articles

Comparison between invasive cardiac output and left ventricular assist device flow parameter.

To evaluate the correlation between left ventricular assist device flow parameter and invasive cardiac output measurements. We retrospectively evaluated right heart catheterization examinations performed in left ventricular assist device patients from 2 tertiary medical centres. We evaluated the correlation between cardiac output measurement methods (indirect Fick and thermodilution) and pump flow parameter using linear regression, and the agreement was graphically displayed using Bland-Altman plot technique. Clinical, echocardiographic, pump and haemodynamic parameters were compared between patients with and without discordance, defined as at least a 20% difference between measurements. The study population consisted of 102 patients [median age 58 (51-64), 86% males, 17 ± 12 months post left ventricular assist device implantation] with a total of 544 measurements compared. Discordance between measurements was present in 102 of 226 (45%) comparisons between indirect Fick and pump flow and in 72 of 161 (48%) between thermodilution and pump flow. A comparison of indirect Fick and left ventricular assist device exhibited a statistical correlation of R = 0.751, and that of thermodilution and left ventricular assist device of R = 0.789. Parameters associated with the presence of discordance between cardiac output measurements included a higher rate of aortic valve opening, lower indirect Fick and higher thermodilution cardiac output. After excluding the lowest tertile of indirect Fick cardiac output values, the correlation between measurements improved (thermodilution: R = 0.879 and indirect Fick: R = 0.843, P < 0.001). The current left ventricular assist device flow parameter provides an estimation of cardiac output that correlates well with indirect Fick and exhibits the strongest correlation with thermodilution. This correlation was stronger after excluding lower cardiac output values.

CARDIAC OUTPUT ESTIMATION: PULSE WAVE ANALYSIS (ANTARES) HIGHLY CORRELATES TO ECHOCARDIOGRAPHY ASSESSMENT

Objective: Evaluation of cardiac output (CO) is crucial for understanding cardiac function and diagnosis of heart failure. While invasive thermodilution procedures serve as the gold standard for CO assessment, routine clinical practice has widely adopted transthoracic Doppler echocardiography (TTE) as the established non-invasive method. Nevertheless, there is a persistent demand for alternative non-invasive approaches, aiming to improve the efficiency of CO estimation, mitigate complications associated with invasive methods, and extend its application to non-intensive care settings, all of which potentially can be offered by oscillometric pulse wave analysis (PWA). This study aims to compare the non-invasive estimation of CO using TTE and the oscillometric PWA algorithm Antares. Design and method: We compared non-invasive cardiac output data obtained through two-dimensional transthoracic echocardiography with data obtained from an oscillometric blood pressure device (custo med GmbH, Ottobrunn, Germany) utilizing the integrated Antares algorithm (Redwave Medical GmbH, Jena, Germany). A total of 59 patients, undergoing elective cardiac catheterization for clinical reasons, were included in the study (mean age 71±10 years, 24% females), but only echocardiography-data with CO were used for analysis. Agreement between the two CO measurement methods (TTE versus Antares) was evaluated through Bland-Altman analysis, Student's t-test, and Pearson correlations. Results: The mean difference in CO was 0.04 ± 1.03 l/min. No statistically significant difference in means was observed between the two CO measurement methods. Significant correlations between transthoracic echocardiography (TTE) and Antares CO were evident in the overall population (r=0.71), as well as in both, female (r=0.80) and male patients (r=0.67; all p&lt;0.001). Conclusions: The oscillometric PWA algorithm Antares and the established TTE exhibit strong correlations for non-invasive CO estimation in both male and female patients, with no statistically significant differences between the two approaches. This study opens the door to a valid and simple detection of heart failure that is seamlessly integrated into a quick and easy-to-perform upper arm blood pressure measurement.

529 PERSPECTIVES ON CARDIAC OUTPUT EVALUATION IN PULMONARY HYPERTENSION PATIENTS UNDERGOING RIGHT HEART CATHETERIZATION

Abstract Background and aim Right heart catheterization (RHC) is the gold standard for the diagnosing and classifying pulmonary hypertension (PH). Cardiac output (CO) and the derived cardiac index (CI) are cornerstones of the hemodynamic evalution allowing pulmonary vascular resistance (PVR) calculation and risk stratification. According to the current European Guidelines, CO should be assessed by the direct Fick method or thermodilution (TD). The indirect Fick (IF) method based on theorically estimated values for VO2, is deemed acceptable bul lacks reliability. Of note, data from the literature on a direct comparison among these three methods used for CO measurement are poor. The objective of our study is to compare CO evaluation by the DF method (DFCO) with CO assessed by IF (IFCO) and TD (TDCO). Secondly, we aimed at assessing the impact of CO estimation by different methods on PVR measurement and therefore on PH hemodynamic classification. This might translate into relevant diagnostic, prognostic and therapeutic implications. Methods 27 patients underwent RHC. Breath-by breath VO2 was measured through a Rudolph mask connected with a two-way respiratory valve to a metabolic cart and averaged over the course of 12 to 15 minutes. DFCO was calculated using the following formula: VO2 (ml/min)/(arteriovenous oxygen content difference×10). For IFCO, the same formula was used with VO2 computed by the Dehmer and the LaFarge-Miettinen formulas. TDCO was obtained through the injection of 10 ml of cold saline solution (0-4°C), in the right atrium and by measuring the temperature variation in the pulmonary artery. Results RHC revealed PH in 23 patients (85%) Average VO2 by Dehmer formula differed significantly from direct measurement (228.9 ± 27.9 ml/min and 204.4 ± 43.6 ml/min respectively; P = 0.017). By using LaFarge formula, mean estimated VO2 differed from direct measurement without reaching statistical significance (185.3 ± 31.9 ml/min and 204.4 ± 43.6 ml/min respectively, P= 0.072). Average CO values did not differ significantly from each other (DFCO 4.2 ± 1.5 L/min; IFCO 4.7 ± 1.3 L/min; TDCO 4.6 ± 1.2 L/min; P=NS for all pairwise comparisons) and showed significant Pearson's correlation. Out of 27 cases, TDCO differed for more (± 0.5 L/min) than 10% as compared to DFCO in 17 (63%). IFCO differed consistently from DFCO in 12 (44%) and IFCO from TDCO in 17 (63%). Despite discrepancies among different CO measurement methods, Cohen's kappa coefficient showed good agreement between the three methods in high PVR (≥3 WU) estimation (IF vs DF 0.79; TD vs DF 0.83 and IF vs TD 0.92 respectively). Conclusions Our results indicate consistent discrepancies among different approaches for VO2 and CO measurement, however this did not impact over PVR assessment and therefore in PH classification. Probably, this is due to the small sample size and the low number of patients (8 of 27) with values around the pathological cut-off for PVR (3 WU). Further studies are needed to better investigate the magnitude of CO measurement discrepancies among different methods on PVR calculation and hemodynamic classification.

Correlation of Hemodynamic and Respiratory Parameters in Invasive Cardiopulmonary Exercise Testing (iCPET).

Background: Invasive cardiopulmonary exercise testing (iCPET) is an integral part in the advanced diagnostic workup of pulmonary hypertension (PH). Our study evaluated the relation between hemodynamic and respiratory parameters at two different resting conditions and two defined low exercise levels with a close synchronization of measurements in a broad variety of dyspnea patients. Subjects and methods: We included 146 patients (median age 69 years, range 22 to 85 years, n = 72 female) with dyspnea of uncertain origin. Invasive hemodynamic and gas exchange parameters were measured at rest, 45° upright position, unloaded cycling, 25 and 50 W exercise. All measurements were performed in a single RHC procedure. Results: Oxygen uptake (VO/body mass) correlated significantly with cardiac index (all p ≤ 0.002) at every resting and exercise level and with every method of cardiac output measurement (thermodilution, method of Fick). Mean pulmonary arterial pressure (PAPmean) correlated with all respiratory parameters (respiratory rate, partial end-tidal pressures of oxygen and carbon dioxide [petCO and petO], ventilation/carbon dioxide resp. oxygen ratio [VE/VCO, VE/VO], and minute ventilation [VE], all p < 0.05). These correlations improved with increasing exercise levels from rest via unloaded cycling to 25 W. There was no correlation with right atrial or pulmonary arterial wedge pressure. Summary: In dyspnea patients of different etiologies, the cardiac index is closely linked to VO at every level of rest and submaximal exercise. PAPmean is the only pressure that correlates with different respiratory parameters, but this correlation is highly significant and stable at rest, unloaded cycling and at 25 W.

Perioperative Continuous Noninvasive Cardiac Output Monitoring in Cardiac Surgery Patients by a Novel Capnodynamic Method

To test the clinical performance of a novel continuous noninvasive cardiac output (CO) monitoring based on expired carbon dioxide kinetics in cardiac surgery patients. A prospective feasibility pragmatic clinical study. A single-center, large community hospital. Thirty-two patients undergoing cardiac surgery were studied during the intraoperative (before cardiopulmonary bypass) and postoperative (in the intensive care unit before extubation) periods. CO was measured simultaneously by the continuous capnodynamic method and by transpulmonary thermodilution during changes in the patient's hemodynamic and/or respiratory conditions. The current recommended comparative statistics for CO measurement methods were analyzed, including bias, precision, and percentage error obtained from Bland-Altman analysis, and concordance between methods obtained from the four-quadrant plot analysis to evaluate the trending ability. Bias ± limits of agreement and percentage error were -0.6 (-1.9 to +0.8; 95% CI of 3.73-5.25) L/min and 31% (n=147 measurements) for the intraoperative period, -0.8 (-2.4 to +0.9; 95% CI of 3.03-5.21) L/min and 41% (n=66) for the postoperative period, and -0.6 (-2.1 to +0.8; 95% CI of 3.74-5.00) L/min and 34% (n=213) for the pooled data. The trending analysis obtained a concordance of 82% (n=65) for the intraoperative and 71% (n=24) for the early postoperative periods. Aggregation of both data sets gave a concordance of 79% (n=89). The continuous capnodynamic method was reliable and in good agreement with the reference method, and had an accuracy and trending ability good enough tomake it a possible future alternative for hemodynamic monitoring in the studied population of elective adult cardiac surgery patients.

Non-invasive methods of cardiac output measurement and their importance in everyday clinical practice: the current state of knowledge

Cardiac output is an important parameter in the evaluation of the patients’ haemodynamic status which can be measured using a number of methods with varying degrees of invasiveness. These include invasive (such as pulmonary artery catheterization, transpulmonary thermodilution, lithium dilution), minimally invasive (catheter-based arterial pressure curve contour analysis, transoesophageal Doppler) and non-invasive (electrical bioimpedance, transthoracic echocardiography, measurement of exhaled CO2, continuous non-invasive blood pressure measurement) techniques. With advances in medicine, the role of non-invasive methods as an alternative to pulmonary artery catheterization continues to grow. The undoubted advantage of non-invasive methods is their safety for the patients and their wide availability. In contrast, invasive methods are characterized by greater measurement precision. It is up to the physician to choose the most appropriate haemodynamic monitoring method depending on the clinical situation. The aim of this article is to discuss non-invasive cardiac output measurement techniques and their application in everyday clinical practice.

Cardiac Output Evaluation on Septic Shock Patients: Comparison between Calibrated and Uncalibrated Devices during Vasopressor Therapy.

There are no reliable, non-invasive methods to accurately measure cardiac output (CO) in septic patients. MostCare (Vytech Health™, Vygon, Padova, Italy), is a beat-to-beat, self calibrated method for CO measurement based on continuous analysis of reflected arterial pressure waveforms. We enrolled 40 patients that were suffering from septic shock and requiring norepinephrine infusion to target blood pressure in order to to evaluate the level of agreement between a calibrated transpulmonary thermodilution device (PiCCO System, Pulsion Medical Systems, Feldkirchen, Germany) and the MostCare system in detecting and tracking changes in CO measurements related to norepinephrine reduction in septic shock patients,. PiCCO was connected to a 5 Fr femoral artery catheter and to a central venous catheter. System calibration was performed with 15 mL of cold saline injection over about 3 s. The MostCare device was connected to the artery catheter to analyze the arterial waveform. Before reducing norepinephrine infusion, the PiCCO system was calibrated, the MostCare waveform was optimized, and the values of the complete hemodynamic profile were recorded (T1). Norepinephrine infusion was then reduced by 0.03 mcg/Kg/min. After 30 min, a new calibration of PiCCO system and a new record on both monitors were performed (T2). Static measurements agreements were assessed using the Bland-Altman test, while trending ability was investigated using polar plot analysis. If volume expansion occurred, then related data were separately analyzed. At T1 mean the CO was 5.38 (SD 0.60) L/min, the mean difference was 0.176 L/min, the limits of agreement (LoA) was +1.39 and −1.04 L/min, and the percentage error (PE) was 22.6%; at T2 the mean CO was 5.44 (SD 0.73) L/min, the mean difference was 0.053 L/min, the LoA was +1.51 and −1.40, and the PE was 27%. After considering the volume expansion between T1 and T2, the mean CO at T1 was 5.39 L/min (SD 0.47), the LoA was +1.09 and −0.78 L/min, and the percentage error (PE) was 17%; at T2 the mean CO was 5.35 L/min (SD 0.81), the LoA was +1.73 and −1.52 L/min, and the PE was 30%. The polar plot diagram seems to confirm the trending ability of MostCare system versus the reference method. In septic patients, when the arterial waveform is accurate, MostCare and PiCCO transpulmonary thermodilution exhibit good agreement even after the reduction of norepinephrine and changes in vascular tone or volume expansion. MostCare could be a rapid to set, reliable, and useful tool to monitor hemodynamic variations in septic patients in emergency contexts where thermodilution methods or other advanced systems are not easily available.

The Effect of Surgical Patient Positions on Plet Variability Index, Perfusion Index and Noninvasive Continuous Cardiac Output Measurement Method in Voluntary Breathing Volunteers

Amaç: Cerrahi prosedür için verilen farklı pozisyonlar doku perfüzyonunda ve kardiyak outputta değişikliklere neden olabilir. Bu çalışmada spontan solunuma sahip katılımcılarda plet değişkenlik indeksinin (PVI), perfüzyon indeks (PI) ve noninvaziv sürekli kardiyak output ölçüm yöntemi (EscCO) nin farklı cerrahi pozisyonlardaki değişimlerini araştırmayı amaçladık.Materyal ve Metod: 20 katılımcıdan oluşan bir sağlıklı birey grubu prospektif gözlemsel çalışmaya dahil edildi. Sırasıyla Supin, 30 derece baş yukarı, 45 derece baş yukarı, 20 derece Trendelenburg, 20 derece ters-Trendelenburg, ve pron pozisyonları uygulandı. Her pozisyon arası 10 ar dk olacak şekilde süre tutuldu. Her pozisyon değişikliğinden önce gönüllüler sırtüstü pozisyona alındı ve beş dakika dinlendikten sonra yeni pozisyon verildi. Pozisyon değişiminden sonraki 5. dakika PI, PVI, EscCO, SpO2 değerleri kayıt altına alındı.Bulgular: Katılımcıların farklı pozisyondayken ölçülen PI, PVI ile EscCO değerlerinde istatistiksel olarak anlamlı bir fark bulunamadı.Sonuç: Bu çalışma, PI, PVI ile EscCO nun tüm cerrahi pozisyonlarda herhangi bir değişikliğe uğramadığını ve her üç parametrenin de spontan solunumuna sahip genç sağlıklı bireylerde pozisyondan etkilenmediği ortaya koymuştur.

Clinically applicable model-based method, for physiologically accurate flow waveform and stroke volume estimation

Background and ObjectivesCardiovascular dysfunction can be more effectively monitored and treated, with accurate, continuous, stroke volume (SV) and/or cardiac output (CO) measurements. Since direct measurements of SV/CO are highly invasive, clinical measures are often discrete, or if continuous, can require recalibration with a discrete SV measurement after hemodynamic instability. This study presents a clinically applicable, non-additionally invasive, physiological model-based, SV and CO measurement method, which does not require recalibration during or after hemodynamic instability. Methods and ResultsThe model’s ability to predict flow profiles and SV is assessed in an animal trial, using endotoxin to induce sepsis in 5 pigs. Mean percentage error between beat-to-beat SV measured from an aortic flow probe and estimated by the model was −2%, while 90% of estimations fell within −24.2% and +27.9% error. Error between estimated and measured changes in mean SV following interventions was less than 30% for 4 out of the 5 pigs. Correlations between model estimated and probe measured flow, for each pig and hemodynamic interventions, was r2 = 0.58 − 0.96, with 21 of the 25 pig intervention stages having r2 > 0.80. ConclusionThe results demonstrate the model accurately estimates and tracks changes in flow profiles and resulting SV, without requiring model recalibration.

P05-8 - Concordance evaluation among three methods for cardiac output measurement in adult patients

P05-8 - Concordance evaluation among three methods for cardiac output measurement in adult patients

P3558Comparison of cardiac output measurement methods for mortality prediction in pulmonary hypertension

P3558Comparison of cardiac output measurement methods for mortality prediction in pulmonary hypertension

MATHEMATICAL MODELING OF STROKE VOLUME FROM THE PERIPHERAL BLOOD FLOW FOR NON INVASIVE PLETHYSMOGRAPHIC MEASUREMENT OF CARDIAC OUTPUT AND ITS VALIDATION

The ability to accurately measure Cardiac Output (CO) is important in clinical medicine as it helps in improving diagnosis of abnormalities and appropriate disease management. In spite of being an important vital parameter, it is still missing from the screens of the bedside monitors employed today. This could be due to the invasiveness of the method or the discomfort in the measurement. Invasive methods are most accurate but can be best suited for the intensive care units (ICUs) and surgeries, but for bedside measurement these methods add an unnecessary risk to the life of the patient. The existing non-invasive method employed for CO measurement is the thoracic bioimpedance method, which is risky for patients with cardiovascular diseases and inaccurate for patients with extra vascular lung water. This paper presents a novel method of CO measurement from the peripheral blood flow, which fairly overcomes the disadvantages of the existing method. The impedance pulse has been acquired across the wrist, instead of the thorax. A new stroke volume equation has been modeled by carrying out the finite element simulation of the blood flow and multiple variable regression to incorporate the patient specific factors. The stroke volume thus obtained has been validated for 57 subjects.

Transpulmonary Thermodilution Versus Transthoracic Echocardiography for Cardiac Output Measurements in Severely Burned Children.

Severe burns trigger a hyperdynamic state, necessitating accurate measurement of cardiac output (CO) for cardiovascular observation and guiding fluid resuscitation. However, it is unknown whether, in burned children, the increasingly popular transthoracic echocardiography (TTE) method of CO measurement is as accurate as the widely used transpulmonary thermodilution (TPTD) method. We retrospectively compared near-simultaneously performed CO measurements in severely burned children using TPTD with the Pulse index Continuous Cardiac Output (PiCCO) system or TTE. Outcomes were compared using t tests, multiple linear regression, and a Bland-Altman plot. Fifty-four children (9 ± 5 years) with 68 ± 18% total body surface area burns were studied. An analysis of 105 data pairs revealed that PiCCO yielded higher CO measurements than TTE (190 ± 39% vs. 150 ± 50% predicted values; P < 0.01). PiCCO- and TTE-derived CO measurements correlated moderately well (R = 0.54, P < 0.01). A Bland-Altman plot showed a mean bias of 1.53 L/min with a 95% prediction interval of 4.31 L/min. TTE-derived estimates of CO may underestimate severity of the hyperdynamic state in severely burned children. We propose using the PiCCO system for objective cardiovascular monitoring and to guide goal-directed fluid resuscitation in this population.

Comparison between pressure-recording analytical method (PRAM) and femoral arterial thermodilution method (FATD) cardiac output monitoring in an infant animal model of cardiac arrest.

BackgroundThe pressure-recording analytical method is a new semi-invasive method for cardiac output measurement (PRAM). There are no studies comparing this technique with femoral artery thermodilution (FATD) in an infant animal model.MethodsA prospective study was performed using 25 immature Maryland pigs weighing 9.5 kg. Fifty-eight simultaneous measurements of cardiac index (CI) were made by FATD and PRAM at baseline and after return of spontaneous circulation. Differences, correlation, and concordance between both methods were analyzed. The ability of PRAM to track changes in CI was explored with a polar plot.ResultsMean CI measurements were 4.5 L/min/m2 (95 % CI, 4.2–4.8 L/min/m2; coefficient of variation, 27 %) by FATD and 4.0 L/min/m2 (95 % CI, 3.6–4.3 L/min/m2; coefficient for variation, 37 %) by PRAM (difference, 0.5 L/min/m2; 95 % CI for the difference, 0.1–1.0 L/min/m2; p = 0.003; n = 58). No correlation between both methods was observed (r = 0.170, p = 0.20). Limits of agreement were −2.9 to 4.0 L/min/m2 (−69.9 to 84.9 %). Percentage error was 80.6 %. Only 26.1 % of data points lied within an absolute deviation of ±30° from the polar axis.ConclusionsNo correlation nor concordance between both methods was observed. Limits of agreement and percentage of error were high and clinically not acceptable. No concurrence between both methods in CI changes was observed. PRAM is not a useful method for measurement of the CI in this pediatric model of cardiac arrest.

Bioreactance is a reliable method for estimating cardiac output at rest and during exercise

Bioreactance is a novel noninvasive method for cardiac output measurement that involves analysis of blood flow-dependent changes in phase shifts of electrical currents applied across the thorax. The present study evaluated the test-retest reliability of bioreactance for assessing haemodynamic variables at rest and during exercise. 22 healthy subjects (26 (4) yrs) performed an incremental cycle ergometer exercise protocol relative to their individual power output at maximal O2 consumption (Wmax) on two separate occasions (trials 1 and 2). Participants cycled for five 3 min stages at 20, 40, 60, 80 and 90% Wmax. Haemodynamic and cardiorespiratory variables were assessed at rest and continuously during the exercise protocol. Cardiac output was not significantly different between trials at rest (P=0.948), or between trials at any stage of the exercise protocol (all P>0.30). There was a strong relationship between cardiac output estimates between the trials (ICC=0.95, P<0.001) and oxygen consumption (ICC=0.99, P<0.001). Stroke volume was also not significantly different between trials at rest (P=0.989) or during exercise (all P>0.15), and strong relationships between trials were found (ICC=0.83, P<0.001). The bioreactance method demonstrates good test-retest reliability for estimating cardiac output at rest and during different stages of graded exercise testing including maximal exertion.

Reliable assessment of perfusion is the Holy Grail of intensive care.

Reliable assessment of perfusion is the Holy Grail of intensive care.

Noninvasive Cardiac Output Measurement by Inert Gas Rebreathing in Suspected Pulmonary Hypertension

The objective of this study was to evaluate inert gas rebreathing (IGR) reliability in cardiac output (CO) measurement compared with Fick method and thermodilution. IGR is a noninvasive method for CO measurement; CO by IGR is calculated as pulmonary blood flow plus intrapulmonary shunt. IGR may be ideal for follow-up of patients with pulmonary hypertension (PH), sparing the need of repeated invasive right-sided cardiac catheterization. Right-sided cardiac catheterization with CO measurement by thermodilution, Fick method, and IGR was performed in 125 patients with possible PH by echocardiography. Patients were grouped according to right-sided cardiac catheterization-measured mean pulmonary and wedge pressures: normal pulmonary arterial pressure (n = 20, mean pulmonary arterial pressure = 18 ± 3 mm Hg, pulmonary capillary wedge pressure = 11 ± 5 mm Hg), PH and normal pulmonary capillary wedge pressure (PH-NW, n = 37 mean pulmonary arterial pressure = 42 ± 13 mm Hg, pulmonary capillary wedge pressure = 11 ± 6 mm Hg), and PH and high pulmonary capillary wedge pressure (PH-HW, n = 68, mean pulmonary arterial pressure = 37 ± 9 mm Hg, pulmonary capillary wedge pressure = 24 ± 6 mm Hg). Thermodilution and Fick measurements were comparable. Fick and IGR agreement was observed in normal pulmonary arterial pressure (CO = 4.10 ± 1.14 and 4.08 ± 0.97 L/min, respectively), whereas IGR overestimated Fick in patients with PH-NW and those with PH-HW because of intrapulmonary shunting overestimation in hypoxemic patients. When patients with arterial oxygen saturation (SO2) ≤90% were excluded, IGR and Fick agreement improved in PH-NW (CO = 4.90 ± 1.70 and 4.76 ± 1.35 L/min, respectively) and PH-HW (CO = 4.05 ± 1.04 and 4.10 ± 1.17 L/min, respectively). In hypoxemic patients, we estimated pulmonary shunt as Fick - pulmonary blood flow and calculated shunt as: -0.2423 × arterial SO2 + 21.373 L/min. In conclusion, IGR is reliable for CO measurement in patients with PH with arterial SO2 >90%. For patients with arterial SO2 ≤90%, a new formula for shunt calculation is proposed.

Influence of drugs on the response characteristics of the LiDCO sensor: an in vitro study

In a previous study, the authors found a large bias (50%) for lithium (LiDCO) compared with thermodilution cardiac output measurement methods in ponies receiving i.v. infusions of xylazine, ketamine, and midazolam. This prompted the authors to examine the effect of drugs on the LiDCO sensor. Drugs and lithium were dissolved in 0.9% saline to produce the following solutions: saline, saline-lithium, saline-drug, and saline-drug-lithium. The drug concentrations were overlapping the range of clinical interest as estimated from the published literature. These 38°C solutions were pumped through the LiDCO sensor in predetermined order. Sensor voltages were measured. Differences between lithium-induced voltage changes in the absence and presence of drugs indicated erroneous lithium detections that, if they occurred in vivo, may cause biases in LiDCO measurements. Clonidine, detomidine, dexmedetomidine, medetomidine, romifidine, xylazine, ketamine, S-ketamine, lidocaine, and rocuronium caused concentration-dependent increases in sensor voltages and negative biases in lithium detection that were mathematically equivalent to greater than +10% biases in LiDCO. The drug-induced voltage changes correlated with calculated biases in LiDCO (r(2)=0.91). Atipamezole, acepromazine, butorphanol, diazepam, midazolam, and guaifenesin caused minimal or no interaction in this study. A number of drugs influenced the accuracy of the LiDCO sensor in vitro but, based on published pharmacokinetic data, only xylazine, ketamine, lidocaine, and rocuronium may cause biases at clinically relevant concentrations. These findings need to be confirmed in vivo. Relevant (>3 mV) changes in sensor voltages due to the presence of drugs may indicate possible interactions with the LiDCO sensor.

Doppler and Volumetric Echocardiographic Methods for Cardiac Output Measurement in Standing Adult Horses

Cardiac output (CO) is not routinely measured in critically ill adult horses because of invasiveness of currently validated methods. Noninvasive CO monitoring would complement clinical assessment of hemodynamic status in adult horses. Volumetric methods for measuring CO will have better agreement with lithium dilution than Doppler-based methods. Eight healthy adult horses. Prospective study. CO was manipulated with continuous rate infusions of dobutamine and romifidine to achieve high and low CO states, respectively. At each level, CO was measured by lithium dilution and various echocardiographic methods. Images stored as video loops were reviewed by an individual blinded to the lithium dilution results. Lithium dilution determinations of CO ranged between 16.6 and 63.0L/min. There was a significant effect of method of CO measurement (P<.001), but no significant effect of CO level (P=.089) or interaction between level and method (P=.607) on the absolute value of the bias. The absolute values of the bias of the right ventricular outflow tract (RVOT) Doppler, Simpson, 4-chamber area-length, and bullet methods [5.5, 6.1, 6.5, 8.8L/min, respectively] were significantly lower than that of the left ventricular outflow tract (LVOT) Doppler or cubic methods [14.8, 24.3L/min, respectively]. The 4-chamber area-length, Simpson, bullet, and RVOT Doppler provided better agreement with lithium dilution than the other methods evaluated. These methods warrant further investigation for use in critically ill adult horses.

Hemodynamics in the Cardiac Catheterization Laboratory of the 21st Century

There has been a striking evolution in the role of the cardiac catheterization laboratory over the past decades.1 In the 1950s and 1960s, hemodynamic assessment in the cardiac catheterization laboratory was essential for understanding the physiology and pathophysiology of patients with cardiovascular diseases. With the development of surgical interventions to treat patients with valvular and congenital heart disease, it became necessary for the cardiac catheterization laboratory to provide an accurate hemodynamic assessment, laying out a therapeutic road map. Nearly all patients who had open heart surgery underwent a complete hemodynamic catheterization before surgery. In the 1980s and 1990s, the evolution of 2-dimensional echocardiography and Doppler echocardiography provided an alternative noninvasive approach for the assessment of both cardiac anatomy and hemodynamics in patients with structural heart disease.2 By measuring blood flow velocities noninvasively, Doppler echocardiography was able to provide information on volumetric flow, intracardiac pressures, pressure gradients, and valve areas, as well as diastolic filling of the heart. Furthermore, noninvasive studies could be repeated easily, allowing the practitioner to follow the progress of his/her patient's condition longitudinally. At the same time, there was growing emphasis on coronary angiography for defining epicardial coronary disease with the subsequent development of interventional approaches for coronary disease with catheter-based therapies. As the major focus in the catheterization laboratory shifted to the diagnosis and treatment of the patient with acute and chronic coronary artery disease, the hemodynamic assessment of patients with structural heart disease was left to the noninvasive echocardiographic laboratory. As a consequence, many cardiac catheterization laboratories provided neither the training nor the expertise to assess hemodynamics properly. However, the advent of procedures such as balloon valvotomy, percutaneous valve implantation, and septal ablation has revived interest in structural heart disease and provided the invasive cardiologist with an armamentarium to treat patients who previously …