Quantification of left ventricular ejection fraction and cardiac output using a novel semi-automated echocardiographic method: a prospective observational study in coronary artery bypass patients.

BACKGROUND: Echocardiographic quantification of ejection fraction (EF) by manual endocardial tracing requires training, is time-consuming and potentially user-dependent, whereas determination of cardiac output by pulmonary artery catheterization (PAC) is invasive and carries a risk of complications. Recently, a novel software for semi-automated EF and CO assessment (AutoEF) using transthoracic echocardiography (TTE) has been introduced. We hypothesized that AutoEF would provide EF values different from those obtained by the modified Simpson's method in transoesophageal echocardiography (TOE) and that AutoEF CO measurements would not agree with those obtained via VTILVOT in TOE and by thermodilution using PAC. METHODS: In 167 patients undergoing coronary artery bypass graft surgery (CABG), TTE cine loops of apical 4- and 2-chamber views were recorded after anaesthesia induction under steady-state conditions. Subsequently, TOE was performed following a standardized protocol, and CO was determined by thermodilution. EF and CO were assessed by TTE AutoEF as well as TOE, using the modified Simpson's method, and Doppler measurements via velocity time integral in the LV outflow tract (VTILVOT). We determined Pearson's correlation coefficients r and carried out Bland-Altman analyses. The primary endpoints were differences in EF and CO. The secondary endpoints were differences in left ventricular volumes at end diastole (LVEDV) and end systole (LVESV). RESULTS: AutoEF and the modified Simpson's method in TOE showed moderate EF correlation (r = 0.38, p < 0.01) with a bias of -12.6% (95% limits of agreement (95%LOA): -36.6 - 11.3%). AutoEF CO correlated poorly both with VTILVOT in TOE (r = 0.19, p < 0.01) and thermodilution (r = 0.28, p < 0.01). The CO bias between AutoEF and VTILVOT was 1.33 l min-1 (95%LOA: -1.72 - 4.38 l min-1) and 1.39 l min-1 (95%LOA -1.34 - 4.12 l min-1) between AutoEF and thermodilution, respectively. AutoEF yielded both significantly lower EF (EFAutoEF: 42.0% (IQR 29.0 - 55.0%) vs. EFTOE Simpson: 55.2% (IQR 40.1 - 70.3%), p < 0.01) and CO values than the reference methods (COAutoEF biplane: 2.30 l min-1 (IQR 1.30 - 3.30 l min-1) vs. COVTI LVOT: 3.64 l min-1 (IQR 2.05 - 5.23 l min-1) and COPAC: 3.90 l min-1 (IQR 2.30 - 5.50 l min-1), p < 0.01)). CONCLUSIONS: AutoEF correlated moderately with TOE EF determined by the modified Simpson's method but poorly both with VTILVOT and thermodilution CO. A systematic bias was detected overestimating LV volumes and underestimating both EF and CO compared to the reference methods. TRIAL REGISTRATION: German Register for Clinical Trials (DRKS-ID DRKS00010666, date of registration: 08/07/2016).

Beyond Conventional Hemodynamic Monitoring-Monitoring to Improve Our Understanding of Disease Process and Interventions.

Monitoring the hemodynamic state of patients is a hallmark of any intensive care environment. However, no single monitoring strategy can provide all the necessary data to paint the entire picture of the state of a patient; each monitor has strengths and weaknesses, advantages, and limitations. We review the currently available hemodynamic monitors used in pediatric critical care units using a clinical scenario. This provides the reader with a construct to understand the progression from basic to more advanced monitoring modalities and how they serve to inform the practitioner at the bedside.

Improving echographic monitoring of hemodynamics in critically ill patients: Validation of right cardiac output measurements through the modified subcostal window / Mejorando la monitorización hemodinámica ecográfica en el paciente crítico: validación de la medición del gasto cardíaco derecho a través de la ventana subcostal modificada

Objective We aimed to assess the usefulness of using the right ventricle outflow tract (RVOT) velocity-time integral (VTI) for echocardiographic monitoring of cardiac output compared to the gold standard, the VTI along the left ventricle outflow tract (LVOT). Design Prospective observational study. Setting A tertiary intensive care unit. Patients 100 consecutive patients. Interventions: echocardiographic monitoring in critically ill patients. Main variables of interest We used intraclass correlation coefficients (ICC) to compare echocardiographic measurements of LVOT VTI through apical window with RVOT VTI through the parasternal and modified subcostal windows and to assess interobserver reproducibility. Preplanned post hoc analyses compared the ICC between ventilated and nonventilated patients. Results At the time of echocardiography, 44 (44%) patients were mechanically ventilated and 28 (28%) were receiving vasoactive drugs. Good-quality measurements were obtained through the parasternal short-axis and/or apical views in 81 (81%) patients and in 100 (100%) patients through the subcostal window. Consistency with LVOT VTI was moderate for RVOT VTI measured from the modified subcostal view (ICC 0.727; 95%CI: 0.62–0.808) and for RVOT VTI measured from the transthoracic view (0.715; 95%CI: 0.59–0.807). Conclusions Measurements of RVOT VTI are moderately consistent with measurements of LVOT VTI. Adding the modified subcostal window allows monitoring RVOT VTI in all the patients of this selected cohort, even those under mechanical ventilation (AU)

Objetivo Valorar la utilidad de la integral velocidad-tiempo (IVT) del tracto de salida del ventrículo derecho (TSVD) para la monitorización del gasto cardíaco comparado con el gold standard, el IVT del tracto de salida del ventrículo izquierdo (TSVI). Diseño Estudio prospectivo observacional. Ámbito UCI de un hospital terciario. Paciente Cien pacientes consecutivos. Intervenciones Ecocardiografías realizadas para monitorización hemodinámica. Variables de interés principales Usamos el coeficiente de correlación intraclase (CCI) para comparar las mediciones de IVT TSVI a través de la ventana apical con el IVT TSVD a través de la ventana paraesternal y subcostal modificada y la reproducibilidad interobservador. Se planeó un análisis post hoc para comparar los resultados en pacientes ventilados con no ventilados. Resultados En el momento de la ecografía, 44 (44%) pacientes estaban en ventilación mecánica y 28 (28%) recibían fármacos vasoactivos. Mediciones de buena calidad se obtuvieron a través de la ventana paraesternal o apical en 81 (81%) pacientes, y en 100 (100%) con la ventana subcostal modificada. La consistencia del IVT TSVI fue moderada con el IVT TSVD medido con la ventana subcostal modificada (CCI 0,727; IC 95%: 0,62-0,808) y la transtorácica (0,715; IC 95%: 0,59-0,807). Conclusiones El IVT TSVD presenta una consistencia moderada cuando se compara con el IVT TSVI. Añadir la ventana subcostal modificada permite monitorizar el IVT TSVD en todos los pacientes de esta cohorte, incluso aquellos con ventilación mecánica (AU)

Continuous Venous-Arterial Doppler Ultrasound During a Preload Challenge.

A preload challenge (PC) is a clinical maneuver that, first, increases the cardiac filling (i.e., preload) and, second, calculates the change in cardiac output. Fundamentally, a PC is a bedside approach for testing the Frank-Starling-Sarnoff (i.e., "cardiac function") curve. Normally, this curve has a steep slope such that a small change in the cardiac preload generates a large change in the stroke volume (SV) or cardiac output. However, in various disease states, the slope of this relationship flattens such that increasing the volume into the heart leads to little rise in the SV. In this pathological scenario, additional cardiac preload (e.g., intravenous fluid) is unlikely to be physiologically effective and could lead to harm if organ congestion evolves. Therefore, inferring both the cardiac preload and output is clinically useful as it may guide intravenous (IV) fluid resuscitation. Accordingly, the goal of this protocol is to describe a method for contemporaneously tracking the surrogates of cardiac preload and output using a novel, wireless, wearable ultrasound during a well-validated preload challenge.

Management of two circulations in a COVID-19 patient with secondary superinfection.

Optimal oxygenation in the intensive care unit requires adequate pulmonary gas exchange, oxygen-carrying capacity in the form of hemoglobin, sufficient delivery of oxygenated hemoglobin to the tissue, and an appropriate tissue oxygen demand. In this Case Study in Physiology, we describe a patient with COVID-19 whose pulmonary gas exchange and oxygen delivery were severely compromised by COVID-19 pneumonia requiring extracorporeal membrane oxygenation (ECMO) support. His clinical course was complicated by a secondary superinfection with staphylococcus aureus and sepsis. This case study is provided with two goals in mind (1) We outline how basic physiology was used to address life-threatening consequences of a novel infection-COVID-19. (2) We describe a strategy of whole-body cooling to lower the cardiac output and oxygen consumption, use of the shunt equation to optimize flow to the ECMO circuit, and transfusion to improve oxygen-carrying capacity when ECMO alone failed to provide sufficient oxygenation.

New Hemodynamic Parameters in Peri-Operative and Critical Care-Challenges in Translation.

Hemodynamic monitoring technologies are evolving continuously-a large number of bedside monitoring options are becoming available in the clinic. Methods such as echocardiography, electrical bioimpedance, and calibrated/uncalibrated analysis of pulse contours are becoming increasingly common. This is leading to a decline in the use of highly invasive monitoring and allowing for safer, more accurate, and continuous measurements. The new devices mainly aim to monitor the well-known hemodynamic variables (e.g., novel pulse contour, bioreactance methods are aimed at measuring widely-used variables such as blood pressure, cardiac output). Even though hemodynamic monitoring is now safer and more accurate, a number of issues remain due to the limited amount of information available for diagnosis and treatment. Extensive work is being carried out in order to allow for more hemodynamic parameters to be measured in the clinic. In this review, we identify and discuss the main sensing strategies aimed at obtaining a more complete picture of the hemodynamic status of a patient, namely: (i) measurement of the circulatory system response to a defined stimulus; (ii) measurement of the microcirculation; (iii) technologies for assessing dynamic vascular mechanisms; and (iv) machine learning methods. By analyzing these four main research strategies, we aim to convey the key aspects, challenges, and clinical value of measuring novel hemodynamic parameters in critical care.

New insights on the cardiovascular effects of IGF-1.

Introduction: Cardiovascular (CV) disorders are steadily increasing, making them the world's most prevalent health issue. New research highlights the importance of insulin-like growth factor 1 (IGF-1) for maintaining CV health. Methods: We searched PubMed and MEDLINE for English and non-English articles with English abstracts published between 1957 (when the first report on IGF-1 identification was published) and 2022. The top search terms were: IGF-1, cardiovascular disease, IGF-1 receptors, IGF-1 and microRNAs, therapeutic interventions with IGF-1, IGF-1 and diabetes, IGF-1 and cardiovascular disease. The search retrieved original peer-reviewed articles, which were further analyzed, focusing on the role of IGF-1 in pathophysiological conditions. We specifically focused on including the most recent findings published in the past five years. Results: IGF-1, an anabolic growth factor, regulates cell division, proliferation, and survival. In addition to its well-known growth-promoting and metabolic effects, there is mounting evidence that IGF-1 plays a specialized role in the complex activities that underpin CV function. IGF-1 promotes cardiac development and improves cardiac output, stroke volume, contractility, and ejection fraction. Furthermore, IGF-1 mediates many growth hormones (GH) actions. IGF-1 stimulates contractility and tissue remodeling in humans to improve heart function after myocardial infarction. IGF-1 also improves the lipid profile, lowers insulin levels, increases insulin sensitivity, and promotes glucose metabolism. These findings point to the intriguing medicinal potential of IGF-1. Human studies associate low serum levels of free or total IGF-1 with an increased risk of CV and cerebrovascular illness. Extensive human trials are being conducted to investigate the therapeutic efficacy and outcomes of IGF-1-related therapy. Discussion: We anticipate the development of novel IGF-1-related therapy with minimal side effects. This review discusses recent findings on the role of IGF-1 in the cardiovascular (CVD) system, including both normal and pathological conditions. We also discuss progress in therapeutic interventions aimed at targeting the IGF axis and provide insights into the epigenetic regulation of IGF-1 mediated by microRNAs.

Sex differences in left ventricular stroke work and cardiac power output per unit myocardium relate to blood pressure in apparently healthy adults.

BACKGROUND: Left ventricular stroke work per unit myocardium (LVSWM) and cardiac power output per unit myocardium (CPOM) are important measures of myocardial workload. The sex differences in the myocardial workload and its correlation with blood pressure remain largely unclear. OBJECTIVES: The purpose of this study is to investigate the sex differences in LVSWM and CPOM, and to relate them to blood pressure in a cohort of apparently healthy adults. METHODS: The LVSWM and CPOM were estimated in 596 age- and heart rate-matched apparently healthy adults (298 men) using transthoracic echocardiography combined with cuff-measured brachial blood pressure. The data were compared between sexes, and the sex differences in LVSWM and CPOM were related to blood pressure. RESULTS: After adjustment for the blood pressure, the LVSWM and CPOM were higher in women than in men [75.0 (73.7-76.4) vs 64.9 (63.5-66.2) cJ/100g for LVSWM, and 912.4 (894.1-930.6) vs 780.2 (762.0-798.5) milliwatt/100g for CPOM, respectively; all P<0.001]. After adjustment for the LVSWM and CPOM, the mean systolic and diastolic blood pressure were 7.4 mm Hg and 5.2 mm Hg higher in men than in women, respectively (all P<0.001). CONCLUSIONS: For any given blood pressure, the workload per unit myocardium is higher in apparently healthy women than in their male counterparts. A sex-specific definition of normal blood pressure with a relatively lower threshold for women can minimize the sex differences in the myocardial workload, which might reduce the potentially comparatively higher risk of heart failure in women.

Changes of cardiac output and velocity time integral in blood return at the end of renal replacement therapy predict fluid responsiveness in critically Ill patients with acute circulatory failure.

OBJECTIVES: To observe if blood return, also defined as the blood infusion test (BIT) could predict fluid responsiveness in critically ill patients with acute circulatory failure and renal replacement therapy (RRT). METHODS: This was a single-center, prospective, diagnostic accuracy study. Before BIT, the passive leg raise test (PLRT) was performed to record the change of cardiac output (ΔCO) by pulse contour analysis, and ΔCO > = 10% was defined as the fluid responder. Meanwhile, the change in velocity time integral (ΔVTI) was recorded by ultrasound. Later, the ΔCO and ΔVTI during BIT were recorded 5-10 min after PLRT. The receiver-operating characteristic curves of ΔCO and ΔVTI of BIT were performed in predicting the fluid responder defined by PLRT. RESULTS: A total of 43 patients with acute circulatory failure undergoing RRT were enrolled in the present study, and 25 patients (58.1%) were recognized as responders during PLRT. According to the receiver-operating characteristic curves, the cutoff value of ΔCO was 10% and ΔVTI was 9% during BIT with the area under curve of 0.96 and 0.94, respectively. CONCLUSIONS: BIT in RRT could identify fluid responsiveness in critically ill patients with shock. TRIAL REGISTRATION: ChiCTR-DDD-17010534. Registered on 30/01/2017 (retrospective registration).

Evaluation of transpulmonary ultrasound dilution cardiac output in piglets: accuracy, precision and trending ability with room temperature injectate.

OBJECTIVE: Transpulmonary ultrasound dilution (TPUD) is a minimally invasive technique to measure cardiac output (CO) using a 1 mL kg-1 isotonic 37 °C saline injectate indicator. The objective was to evaluate the performance of TPUD using a room temperature saline injectate. STUDY DESIGN: Prospective experimental trial. ANIMALS: A total of seven anesthetized male Yorkshire piglets. METHODS: Piglets aged 1 month and weighing 7.7-9.0 kg were anesthetized with detomidine-ketamine-hydromorphone-isoflurane and a pulmonary artery flow probe (PAFP) placed via a median sternotomy. The thoracic cavity remained open during measurement of CO by PAFP and TPUD. The TPUD indicators of 1 mL kg-1 0.9% saline at 37 °C and 20 °C were compared during infusions of phenylephrine and dobutamine, blood withdrawal and replacement. Bias, limits of agreement (LoAs) and percentage error (PE) between each iteration of PAFP and TPUD were measured with Bland-Altman plots. Trending ability via concordance, angular bias and radial LoA were compared. RESULTS: Bland-Altman plots showed negligible bias with varying LoAs. PEs of 22% and 38% were found for 37 °C and 20 °C saline injectates, respectively. In the four-quadrant plots, the concordance rate was 94% and 100% for measurements obtained with 37 °C and 20 °C saline injectates, respectively. Angular bias for both were < ±5 °, with radial LoA < ±7 °. CONCLUSIONS: TPUD was accurate when using 1 mL kg-1 of isotonic saline at 37 °C in a range of CO within 0.2-0.8 L minute-1, and it reliably tracked positive and negative changes in CO. Room temperature (20 °C) indicator was less accurate but equally able to track direction of changes in CO. CLINICAL RELEVANCE: The use of room temperature injectates allows an easy, readily available clinical application of TPUD CO monitoring while preserving the trending ability of the monitor.

A New Method of Identifying Characteristic Points in the Impedance Cardiography Signal Based on Empirical Mode Decomposition.

The accurate detection of fiducial points in the impedance cardiography signal (ICG) has a decisive impact on the proper estimation of diagnostic parameters such as stroke volume or cardiac output. It is, therefore, necessary to find an algorithm that is able to assess their positions with great precision. The solution to this problem is, however, quite challenging with regard to the high sensitivity of the ICG technique to the noise and varying morphology of the acquired signals. The aim of this study is to propose a novel method that allows us to overcome these limitations. The developed algorithm is based on Empirical Mode Decomposition (EMD)-an effective technique for processing and analyzing various types of non-stationary signals. We find high correlations between the results obtained from the algorithm and annotated by an expert. This, in turn, implies that the difference in estimation of the diagnostic-relevant parameters is small, which suggests that the method can automatically provide precise clinical information.

Central Venous Waveform Analysis and Cardiac Output in a Porcine Model of Endotoxemic Hypotension and Resuscitation.

BACKGROUND: Cardiac output (CO) is a valuable proxy for perfusion, and governs volume responsiveness during resuscitation from distributive shock. The underappreciated venous system has nuanced physiology that confers valuable hemodynamic information. In this investigation, deconvolution of the central venous waveform by the fast Fourier transformation (FFT) algorithm is performed to assess its ability to constitute a CO surrogate in a porcine model of endotoxemia-induced distributive hypotension and resuscitation. STUDY DESIGN: Ten pigs were anesthetized, catheterized, and intubated. A lipopolysaccharides infusion protocol was used to precipitate low systemic vascular resistance hypotension. Four crystalloid boluses (10 cc/kg) were then given in succession, after which heart rate, mean arterial pressure, thermodilution-derived CO, central venous pressure (CVP), and the central venous waveform were collected, the last undergoing fast Fourier transformation analysis. The amplitude of the fundamental frequency of the central venous waveform's cardiac wave (f0-CVP) was obtained. Heart rate, mean arterial pressure, CVP, f0-CVP, and CO were plotted over the course of the boluses to determine whether f0-CVP tracked with CO better than the vital signs, or than CVP itself. RESULTS: Distributive hypotension to a 25% mean arterial pressure decrement was achieved, with decreased systemic vascular resistance (mean 918 ± 227 [SD] dyne/s/cm-5 vs 685 ± 180 dyne/s/cm-5; p = 0.038). Full hemodynamic parameters characterizing this model were reported. Slopes of linear regression lines of heart rate, mean arterial pressure, CVP, f0-CVP, and CO were -2.8, 1.7, 1.8, 0.40, and 0.35, respectively, demonstrating that f0-CVP values closely track with CO over the 4-bolus range. CONCLUSIONS: Fast Fourier transformation analysis of the central venous waveform may allow real-time assessment of CO during resuscitation from distributive hypotension, possibly offering a venous-based approach to clinical estimation of volume responsiveness.

Translational implications of bradyarrhythmia in hibernating brown bears.

The brown bear Ursus arctos undergoes exceptional physiological adaptions during annual hibernation that minimize energy consumption, including profound decrease in heart rate, cardiac output, and respiratory rate. These changes are completely reversible after the bears reenter into the active state in spring. In this case report, we show episodes of sinus arrest in a hibernating Scandinavian brown bear and in humans, recorded by implantable loop recorders and discuss the possible underlying mechanisms. Lessons learned from cardiac adaptations in hibernating bears might prove useful in the treatment of patients with sinus node dysfunction.

Thermodilution Assessment of Cardiac Index in Patients With Tricuspid Regurgitation.

BACKGROUND: Disparities between thermodilution (TD) and Fick measurements of cardiac index (CI) are common in real-world clinical practice. Published studies about the effect of tricuspid regurgitation (TR) on TD are small and describe conflicting results. We tested the correlation between TD and Fick across a wide range of TR severity, in a larger group of patients undergoing right heart catheterization (RHC). We aimed to determine if TD is an acceptable alternative to Fick in patients with TR in clinical practice. METHODS: We retrospectively evaluated patients undergoing RHC at a single center over a 10-month period, and included those with recent (<90 days) echocardiograms. TD was measured during RHC and Fick was calculated using estimated oxygen consumption. The primary outcome was the correlation between TD and Fick CIs. We performed regression modeling to evaluate predictors of the difference between TD and Fick. RESULTS: A total of 349 patients were included, 40% of whom had at least moderate TR. The correlation between TD and Fick was strong (r=0.765) and did not significantly differ in those with none to mild TR (r=0.73) and those with moderate to severe TR (r=0.80). Atrial fibrillation or atrial flutter was the only variable significantly associated with the difference between CI by Fick and TD (P=.04). CONCLUSION: The correlation between TD and Fick was strong and unaffected by TR severity.

Effect of aortic curvature on bioprosthetic aortic valve performance.

Transvalvular pressure gradient (ΔP) after aortic valve replacement is an important surrogate of aortic bioprostheses performance. Invasive ΔP is often measured after transcatheter aortic valve replacement to exclude patient-prosthetic mismatch. However, invasive aortic pressures are usually recorded in the pressure recovery (PR) zone downstream of the valve, potentially resulting in ΔP underestimation compared to noninvasive measurements. PR was extensively studied in straight ascending aortas. However, the impact of various aortic arch configurations on ΔP has not been explored. PR was assessed in a pulse duplicating simulator at various cardiac conditions of cardiac output, heart rates and pressures. Three different aortic geometries with identical root dimensions but with different aortic arches were used: (1) curvature 1, (2) curvature 2, and (3) straight aortic models. Instantaneous pressure and peak ΔP measurements were recorded incrementally along the models for each cardiac condition. The models with aortic arches produced two distinct PR zones (after the valve and after the aortic arch), whereas the model without an aortic arch produced only one PR zone (after the valve). The trend of the pressure and ΔP curves for each model was independent of the cardiac condition used, but the individually measured pressure magnitudes did change with different conditions. In this study, we illustrated the differences in PR between distinct aortic curvatures and straight aorta. PR affects pressure and ΔP measurements. These effects are clear when recording aortic pressures by catheterization and echocardiography.

A wearable cardiac ultrasound imager.

Continuous imaging of cardiac functions is highly desirable for the assessment of long-term cardiovascular health, detection of acute cardiac dysfunction and clinical management of critically ill or surgical patients1-4. However, conventional non-invasive approaches to image the cardiac function cannot provide continuous measurements owing to device bulkiness5-11, and existing wearable cardiac devices can only capture signals on the skin12-16. Here we report a wearable ultrasonic device for continuous, real-time and direct cardiac function assessment. We introduce innovations in device design and material fabrication that improve the mechanical coupling between the device and human skin, allowing the left ventricle to be examined from different views during motion. We also develop a deep learning model that automatically extracts the left ventricular volume from the continuous image recording, yielding waveforms of key cardiac performance indices such as stroke volume, cardiac output and ejection fraction. This technology enables dynamic wearable monitoring of cardiac performance with substantially improved accuracy in various environments.

Increased reliance on coronary perfusion for cardiorespiratory performance in seawater-acclimated rainbow trout.

Salmonid ventricles are composed of spongy and compact myocardium, the latter being perfused via a coronary circulation. Rainbow trout (Oncorhynchus mykiss) acclimated to sea water have higher proportions of compact myocardium and display stroke volume-mediated elevations in resting cardiac output relative to freshwater-acclimated trout, probably to meet the higher metabolic needs of osmoregulatory functions. Here, we tested the hypothesis that cardiorespiratory performance of rainbow trout in sea water is more dependent on coronary perfusion by assessing the effects of coronary ligation on cardiorespiratory function in resting and exhaustively exercised trout acclimated to fresh water or sea water. While ligation only had minor effects on resting cardiorespiratory function across salinities, cardiac function after chasing to exhaustion was impaired, presumably as a consequence of atrioventricular block. Ligation reduced maximum O2 consumption rate by 33% and 17% in fish acclimated to sea water and fresh water, respectively, which caused corresponding 41% and 17% reductions in aerobic scope. This was partly explained by different effects on cardiac performance, as maximum stroke volume was only significantly impaired by ligation in sea water, resulting in 38% lower maximum cardiac output in seawater compared with 28% in fresh water. The more pronounced effect on respiratory performance in sea water was presumably also explained by lower blood O2 carrying capacity, with ligated seawater-acclimated trout having 16% and 17% lower haemoglobin concentration and haematocrit, respectively, relative to ligated freshwater trout. In conclusion, we show that the coronary circulation allows seawater-acclimated trout to maintain aerobic scope at a level comparable to that in fresh water.

Study of the accuracy of a radial arterial pressure waveform cardiac output measurement device after cardiac surgery.

BACKGROUND: Less invasive monitoring, such as radial arterial pulse contour analysis (ProAQT® sensor), represents an alternative when hemodynamic monitoring is necessary to guide postoperative management and invasive monitoring is not technically feasible. The aim of the study is to evaluate the accuracy of the ProAQT® sensor cardiac output measurements in comparison with Pulmonary Artery Catheter (PAC) during the postoperative course of patients who underwent cardiac surgery with cardiopulmonary bypass. CASE PRESENTATION: Prospective observational study in a Surgical Intensive Care Unit of a tertiary university hospital. Ten patients with a mean age of 73.5 years were included. The main comorbidities were hypertension, diabetes, dyslipidemia and the preoperative left ejection fraction was 43.8 ± 14.5%. Regarding the type of surgery, six patients underwent valve surgery, two underwent coronary artery bypass grafting and two underwent aortic surgery. The cardiac index measured simultaneously by the ProAQT® sensor was compared with the PAC. The parameters were evaluated at predefined time points during the early postoperative courses (6 h, 12 h, 24 h, 48 h and 72 h). The degree of agreement with the cardiac index between the PAC and the ProAQT® sensor along the time points was measured using the concordance correlation coefficient, Bland-Altman analysis, and four-quadrant plot. Sixty-three pairs of measurements were analyzed. We showed that measurements of cardiac index were slightly higher with PAC (ß Ì‚ = - 0.146, p-value = 0.094). The concordance correlation coefficient for the additive model of cardiac index was 0.64 (95% Confidence Interval: 0.36, 0.82), indicating a high concordance between both sensors. Bland-Altmann analysis showed a mean bias of 0.45 L·min-1·m-2, limits of agreement from - 1.65 to 2.3 L·min-1·m-2, and percentage of error was 82.5%. Four-quadrant plot of changes in cardiac index showed a good concordance rate (75%), which increases after applying the exclusion zone (87%). CONCLUSIONS: In patients undergoing cardiac surgery, the ProAQT® sensor may be useful to monitor cardiac index during the postoperative period, especially when more invasive monitoring is not possible.

Pulmonary hypertension due to high cardiac output.

Pulmonary hypertension (PH) is usually associated with a normal or decreased cardiac output (CO). Less commonly, PH can occur in the context of a hyperdynamic circulation, characterized by high CO (>8 L/min) and/or cardiac index ≥4 L/min/m2 in the setting of a decreased systemic vascular resistance. PH due to high CO can occur due to multiple conditions and in general remains understudied. In this review article we describe the pathophysiology, etiology, diagnosis, hemodynamic characteristics, and management of PH in the setting of high CO. It is important to recognize this distinct entity as PH tends to improve with treatment of the underlying etiology and PH specific therapies may worsen the hemodynamic state.