Critical Care Ultrasound in Shock: A Comprehensive Review of Ultrasound Protocol for Hemodynamic Assessment in the Intensive Care Unit.

Shock is a life-threatening condition that requires prompt recognition and treatment to prevent organ failure. In the intensive care unit, shock is a common presentation, and its management is challenging. Critical care ultrasound has emerged as a reliable and reproducible tool in diagnosing and classifying shock. This comprehensive review proposes an ultrasound-based protocol for the hemodynamic assessment of shock to guide its management in the ICU. The protocol classifies shock as either low or high cardiac index and differentiates obstructive, hypovolemic, cardiogenic, and distributive etiologies. In distributive shock, the protocol proposes a hemodynamic-based approach that considers the presence of dynamic obstruction, fluid responsiveness, fluid tolerance, and ventriculo-arterial coupling. The protocol gives value to quantitative measures based on critical care ultrasound to guide hemodynamic management. Using critical care ultrasound for a comprehensive hemodynamic assessment can help clinicians diagnose the etiology of shock and define the appropriate treatment while monitoring the response. The protocol's use in the ICU can facilitate prompt recognition, diagnosis, and management of shock, ultimately improving patient outcomes.

The effect of caffeine chewing gum on muscle performance and fatigue after severe-intensity exercise: isometric vs. dynamic assessments in trained cyclists.

This study investigated the effect of caffeinated chewing gum (GUMCAF) on muscle fatigue (isometric vs. dynamic) after severe-intensity cycling bouts. Fifteen trained male cyclists participated in four visits. Each visit involved two severe-intensity cycling bouts (Δ1 and Δ2) lasting 6 min, separated by a 5-min recovery period. Muscle fatigue was assessed by isometric maximal voluntary knee extension contraction (IMVC) with twitch interpolation technique and dynamically by 7 s all-out cycling sprints. Assessments were performed before GUMCAF (Pre-GUM) and after the cycling bouts (Post-Exercise). GUMCAF and placebo gum (GUMPLA) were administered in a randomized double-blind procedure with participants receiving each gum type (GUMCAF and GUMPLA) during two separate visits. The results showed no significant interaction between gum types and time for the isometric and dynamic measurements (p > 0.05). The percentage change in performance from Pre-GUM to Post-Exercise showed no significant difference between GUMCAF and GUMPLA for either the dynamic-derived TMAX (~ -17.8% and -15.1%, respectively; p = 0.551) or isometric IMVC (~ -12.3% and -17.7%, respectively; p = 0.091) measurements. Moderate to large correlations (r = 0.31-0.51) were found between changes in sprint maximal torque and maximal power output measurements and isometric force, for both gum conditions. GUMCAF was not effective in attenuating muscle force decline triggered by severe-intensity cycling exercises, as measured by both isometric and dynamic methods. The correlations between IMVC and cycling maximal torque and power output suggest caution when interpreting isometric force as a direct measure of fatigue during dynamic cycling exercises.

Correlation between corrected carotid flow time and left ventricular outflow tract velocity-time integral using a novel technique.

BACKGROUND: Transthoracic echocardiography (TTE) is widely used for assessing patients in the intensive care unit, with cardiac output measurement being crucial for hemodynamic monitoring. This is achieved by measuring the velocity-time integral (VTI) of the left ventricular outflow tract (LVOT), which serves as a surrogate of stroke volume. However, conducting TTE in the critical care setting presents several challenges. Our primary objective was to investigate the relationship between carotid corrected flow time (cCFT) and LVOT VTI. Additionally, we aimed to determine the threshold cCFT value that reliably predicts a normal LVOT VTI. MATERIALS AND METHODS: This proof-of-concept study involves a post-hoc analysis from a diagnostic accuracy investigation conducted in a medical-surgical intensive care unit. We included patients admitted to the ICU from December 2021 to January 2022. We used a phased array transducer to measure the cCFT at the left supraclavicular fossa and the LVOT VTI in an apical 5-chamber view. RESULTS: We included 22 patients. The Spearman coefficient between LVOT VTI and cCFT was 0.82 (p < 0.0001). The area under the ROC curve for cCFT to predict LVOT VTI equal to or greater than 17 cm was 0.871 (95% CI 0.660-0.974). A cCFT exceeding 283 ms predicted LVOT VTI equal to or greater than 17 cm with a sensitivity of 93.3% (95% CI 68.1% to 99.8%) and specificity of 85.7% (95% CI 42.1% to 99.6%). CONCLUSION: The cCFT, measured using a novel technique with a phased array transducer, shows a strong correlation with LVOT VTI. Additionally, cCFT predicts a normal LVOT VTI with good sensitivity and specificity in critically ill patients. Larger studies are warranted to validate these findings.

How does participation in Global Value Chains affect embodied carbon emissions in international trade? New insights from cross-country panel data analysis.

Global Value Chains (GVCs) significantly influence international trade and environmental outcomes. Despite the economic benefits of GVCs, their impact on the environment remains under-examined. This study  analyzes the effects of GVC participation (considering forward and backward positions) on total carbon emissions embodied in exports (TEEE) and imports (TEEI). Utilizing panel data from 65 economies spanning 1995 to 2018, we apply input-output matrices and the system generalized method of moments (GMM-SYS) approach. Our results indicate that GVC participation generally is associated with reductions in TEEI and increases in TEEE, with backward participation exerting a more substantial impact. Furthermore, we observed asymmetrical impacts of GVC participation between developed and developing countries. Developed nations tend to reap greater benefits from GVC in terms of diminished CO2 emissions associated with imports, as well as notable CO2 reductions in both exports and imports, particularly when forward participation is the focal point. Conversely, developing countries grapple with heightened environmental burdens stemming from their engagement in backward linkages.

Use of the cardiac power index to predict fluid responsiveness in the prone position: a proof-of-concept study.

BACKGROUND: The primary aim of this proof-of-concept study was to investigate whether the Cardiac Power Index (CPI) could be a novel alternative method to assess fluid responsiveness in the prone position. METHODS: Patients undergoing scheduled elective lumbar spine surgery in the prone position under general anesthesia were enrolled in the criteria of patients aged 19-75 years with American Society of Anesthesiologists (ASA) physical status I-II. The hemodynamic variables were evaluated before and after changes in posture after administering a colloid bolus (5 mL.kg-1) in the prone position. Fluid responsiveness was defined as an increase in the Stroke Volume Index (SVI) ≥ 10%. RESULTS: A total of 28 patients were enrolled. In responders, the CPI (median [1/4Q-3/4Q]) decreased to 0.34 [0.28-0.39] W.m-2 (p = 0.035) after the prone position. After following fluid loading, CPI increased to 0.48 [0.37-0.52] W.m-2 (p < 0.008), and decreased SVI (median [1/4Q-3/4Q]) after prone increased from 26.0 [24.5-28.0] mL.m-2 to 33.0 [31.0-37.5] mL.m-2 (p = 0.014). Among non-responders, CPI decreased to 0.43 [0.28-0.53] W.m-2 (p = 0.011), and SVI decreased to 29.0 [23.5-34.8] mL.m-2 (p < 0.009). CPI exhibited predictive capabilities for fluid responsiveness as a receiver operating characteristic curve of 0.78 [95% Confidence Interval, 0.60-0.95; p = 0.025]. CONCLUSION: This study suggests the potential of CPI as an alternative method to existing preload indices in assessing fluid responsiveness in clinical scenarios, offering potential benefits for responders and non-responders.

Estimation of urinary volume through ultrasonography in dog cadavers and experimental models.

The urinary volume and residual urine volume are pieces of information that can provide relevant clinical data for dogs and cats, especially those hospitalized. Thus, the present study aimed to evaluate mathematical formulas described in human and veterinary literature to estimate urinary volume in dogs and experimental models. For this purpose, nine male dog cadavers and twelve experimental models were used to evaluate residual volume, small, medium, and large, using three different formulas. Data were obtained by three different examiners: two ultrasonographers and one nonultrasonographer. Each examiner recorded three longitudinal and transverse images, obtaining measurements of width, length, and height at each proposed volume. The measurements were then averaged, and the result was added to the formulas, thus estimating urinary volume. All three formulas achieved higher accuracy in estimating smaller volumes, with a gradual decrease as urinary volume increased. The error of all formulas was less than 10%, even when compared with evaluations in experimental models and dogs. There was variation in estimation between ultrasonographers and nonultrasonographer examiners; however, this variation was low, allowing for the assertion that both can apply the technique. Thus, it is concluded that estimating urinary bladder volume using mathematical formulas and 2D ultrasound is accurate and, therefore, an alternative and viable option for evaluating the urinary tract.

Correlation and concordance of carotid Doppler ultrasound and echocardiography with invasive cardiac output measurement in critically ill patients.

BACKGROUND: Critical care management heavily relies on accurate cardiac output (CO) measurement. Echocardiography has been a mainstay in non-invasive cardiac monitoring; however, its comparability to invasive methods warrants further exploration. Recent studies have suggested the potential of carotid Doppler measurements as a promising approach to estimate CO. Despite this potential, the literature presents mixed outcomes regarding its reliability and accuracy. This study aims to evaluate the correlation and concordance between carotid Doppler ultrasonography and invasive hemodynamic monitoring in estimating CO in critically ill patients. Furthermore, it assesses the concordance and correlation between echocardiography CO and the standard invasive CO measurements. METHODS: This concordance study involved critically ill adults requiring invasive CO measurement. Patients with arrhythmias, severe valvulopathy, pregnancy, and poor acoustic window were excluded. Statistical analyses comprised univariate analysis, Wilcoxon signed-rank test, Spearman correlation, and intraclass correlation coefficient. Ethical approval was granted by the institution's ethics committee. RESULTS: A total of 49 critically ill patients were included, predominantly male (63.27%), with a median age of 57 years. Diagnoses included subarachnoid hemorrhage (53.06%) and heart failure (8.16%). Mean cardiac index was 3.36 ± 0.81 L/min/m2 and mean cardiac output was 5.98 ± 1.47 L/min. Spearman correlation coefficient between echocardiography and invasive CO measurements was 0.58 (p-value = p < 0.001), with an ICC of 0.59 for CO and 0.52 for cardiac index. Carotid measurements displayed no significant correlation with invasive CO. CONCLUSION: There is a moderate correlation and concordance between echocardiography and invasive CO measurements. There is no significant correlation between carotid variables and invasive CO, underscoring the necessity for cautious interpretation and application, particularly in patients with distinctive cerebral blood flow dynamics.

Assessment of fluid responsiveness using pulse pressure variation, stroke volume variation, plethysmographic variability index, central venous pressure, and inferior vena cava variation in patients undergoing mechanical ventilation: a systematic review and meta-analysis.

IMPORTANCE: Maneuvers assessing fluid responsiveness before an intravascular volume expansion may limit useless fluid administration, which in turn may improve outcomes. OBJECTIVE: To describe maneuvers for assessing fluid responsiveness in mechanically ventilated patients. REGISTRATION: The protocol was registered at PROSPERO: CRD42019146781. INFORMATION SOURCES AND SEARCH: PubMed, EMBASE, CINAHL, SCOPUS, and Web of Science were search from inception to 08/08/2023. STUDY SELECTION AND DATA COLLECTION: Prospective and intervention studies were selected. STATISTICAL ANALYSIS: Data for each maneuver were reported individually and data from the five most employed maneuvers were aggregated. A traditional and a Bayesian meta-analysis approach were performed. RESULTS: A total of 69 studies, encompassing 3185 fluid challenges and 2711 patients were analyzed. The prevalence of fluid responsiveness was 49.9%. Pulse pressure variation (PPV) was studied in 40 studies, mean threshold with 95% confidence intervals (95% CI) = 11.5 (10.5-12.4)%, and area under the receiver operating characteristics curve (AUC) with 95% CI was 0.87 (0.84-0.90). Stroke volume variation (SVV) was studied in 24 studies, mean threshold with 95% CI = 12.1 (10.9-13.3)%, and AUC with 95% CI was 0.87 (0.84-0.91). The plethysmographic variability index (PVI) was studied in 17 studies, mean threshold = 13.8 (12.3-15.3)%, and AUC was 0.88 (0.82-0.94). Central venous pressure (CVP) was studied in 12 studies, mean threshold with 95% CI = 9.0 (7.7-10.1) mmHg, and AUC with 95% CI was 0.77 (0.69-0.87). Inferior vena cava variation (∆IVC) was studied in 8 studies, mean threshold = 15.4 (13.3-17.6)%, and AUC with 95% CI was 0.83 (0.78-0.89). CONCLUSIONS: Fluid responsiveness can be reliably assessed in adult patients under mechanical ventilation. Among the five maneuvers compared in predicting fluid responsiveness, PPV, SVV, and PVI were superior to CVP and ∆IVC. However, there is no data supporting any of the above mentioned as being the best maneuver. Additionally, other well-established tests, such as the passive leg raising test, end-expiratory occlusion test, and tidal volume challenge, are also reliable.

A randomized controlled trial of ivabradine in patients with acute myocardial infarction related cardiogenic shock.

Objective: . Acute myocardial infarction-related cardiogenic shock (AMI-CS) is often accompanied by tachycardia, which, in turn, increases myocardial oxygen consumption and hinders the use of ventricular assist devices, such as intra-aortic balloon pump. Evidence suggests that ivabradine may reduce heart rate (HR) without affecting other hemodynamic parameters. The aim of the present study was to determine the effect of ivabradine on reducing HR and changes in other hemodynamic parameters such as cardiac index (CI), in patients with AMI-CS and tachycardia. Materials and methods: . A single-center, open label, randomized clinical trial included patients diagnosed with AMI-CS and tachycardia with >100 beats per minute (BPM). Heart rate, cardiac index, and other hemodynamic parameters measured by pulmonary flotation catheter were compared at 0, 6, 12, 24, and 48 hours after randomization. Results: . A total of 12 patients were randomized; 6 received standard therapy, and 6 received ivabradine in addition to standard therapy. Baseline clinical characteristics were similar at randomization. A statistically significant lower heart rate was found at 12 hours (p=0.003) and 48 hours (p=0.029) after randomization, with differences of -23.3 (-8.2 to -38.4) BPM and -12.6 (-0.5 to -25.9) BPM, respectively. No differences in cardiac index, or any other evaluated hemodynamic parameters, length of hospital stay, nor mortality rate were noted between both groups. Conclusions: . The use of ivabradine in patients with AMI-CS was associated with a significant reduction in heart rate at 12 and 48 h, without affecting other hemodynamic parameters.

Objetivo: . El choque cardiogénico relacionado con el infarto agudo de miocardio (AMI-CS, por sus siglas en inglés) suele ir acompañado de taquicardia, lo que, a su vez, aumenta el consumo de oxígeno miocárdico y dificulta el uso de dispositivos de asistencia ventricular, como la bomba de balón intraaórtico. La evidencia sugiere que la ivabradina puede reducir la frecuencia cardíaca (FC) sin afectar otros parámetros hemodinámicos. El objetivo del presente estudio fue determinar el efecto de la ivabradina en la reducción de la FC y los cambios en otros parámetros hemodinámicos como el índice cardíaco (CI) en pacientes con AMI-CS y taquicardia. Materiales y métodos: Se incluyeron pacientes diagnosticados con AMI-CS y taquicardia con >100 latidos por minuto (LPM) en un ensayo clínico aleatorizado de un solo centro. La frecuencia cardíaca, el índice cardíaco y otros parámetros hemodinámicos medidos mediante catéter de flotación pulmonar se compararon a las 0, 6, 12, 24 y 48 h después de la aleatorización. Resultados: Se aleatorizaron un total de 12 pacientes; 6 recibieron terapia estándar y 6 recibieron ivabradina además de la terapia estándar. Las características clínicas basales fueron similares en la aleatorización. Se encontró una frecuencia cardíaca significativamente más baja a las 12 h (p=0,003) y a las 48 h (p=0,029) después de la aleatorización, con diferencias de -23,3 (-8,2 a -38,4) LPM y -12,6 (-0,5 a -25,9) LPM, respectivamente. No se observaron diferencias en el índice cardíaco, en ningún otro parámetro hemodinámico evaluado; tampoco en la duración de la estancia hospitalaria, ni en la tasa de mortalidad entre ambos grupos. Conclusiones: El uso de ivabradina en pacientes con AMI-CS se asoció con una reducción significativa en la frecuencia cardíaca a las 12 y 48 h, sin afectar otros parámetros hemodinámicos.

Continuous-Time Model Identification of the Subglottal System.

Mathematical models that accurately simulate the physiological systems of the human body serve as cornerstone instruments for advancing medical science and facilitating innovative clinical interventions. One application is the modeling of the subglottal tract and neck skin properties for its use in the ambulatory assessment of vocal function, by enabling non-invasive monitoring of glottal airflow via a neck surface accelerometer. For the technique to be effective, the development of an accurate building block model for the subglottal tract is required. Such a model is expected to utilize glottal volume velocity as the input parameter and yield neck skin acceleration as the corresponding output. In contrast to preceding efforts that employed frequency-domain methods, the present paper leverages system identification techniques to derive a parsimonious continuous-time model of the subglottal tract using time-domain data samples. Additionally, an examination of the model order is conducted through the application of various information criteria. Once a low-order model is successfully fitted, an inverse filter based on a Kalman smoother is utilized for the estimation of glottal volume velocity and related aerodynamic metrics, thereby constituting the most efficient execution of these estimates thus far. Anticipated reductions in computational time and complexity due to the lower order of the subglottal model hold particular relevance for real-time monitoring. Simultaneously, the methodology proves efficient in generating a spectrum of aerodynamic features essential for ambulatory vocal function assessment.

The Effects of Dobutamine in Septic Shock: An Updated Narrative Review of Clinical and Experimental Studies.

The key objective in the hemodynamic treatment of septic shock is the optimization of tissue perfusion and oxygenation. This is usually achieved by the utilization of fluids, vasopressors, and inotropes. Dobutamine is the inotrope most commonly recommended and used for this purpose. Despite the fact that dobutamine was introduced almost half a century ago in the treatment of septic shock, and there is widespread use of the drug, several aspects of its pharmacodynamics remain poorly understood. In normal subjects, dobutamine increases contractility and lacks a direct effect on vascular tone. This results in augmented cardiac output and blood pressure, with reflex reduction in systemic vascular resistance. In septic shock, some experimental and clinical research suggest beneficial effects on systemic and regional perfusion. Nevertheless, other studies found heterogeneous and unpredictable effects with frequent side effects. In this narrative review, we discuss the pharmacodynamic characteristics of dobutamine and its physiologic actions in different settings, with special reference to septic shock. We discuss studies showing that dobutamine frequently induces tachycardia and vasodilation, without positive actions on contractility. Since untoward effects are often found and therapeutic benefits are occasional, its profile of efficacy and safety seems low. Therefore, we recommend that the use of dobutamine in septic shock should be cautious. Before a final decision about its prescription, efficacy, and tolerance should be evaluated throughout a short period with narrow monitoring of its wanted and side effects.

Consensus of the Brazilian association of hematology, hemotherapy and cellular therapy on patient blood management: Anemia tolerance mechanisms.

Understanding the physiological concepts of oxygen delivery is essential to discern the mechanisms that influence its increase, reduction or maintenance in the body. This text explores the different mechanisms that help maintain oxygen delivery even in the face of reduced hemoglobin levels. Adequate oxygen delivery ensures tissue and metabolic balance, which is crucial to avoid harmful consequences such as metabolic acidosis and cellular dysoxia. The complex interaction between variables such as cardiac output, hemoglobin and heart rate (HR) plays a fundamental role in maintaining oxygen delivery, allowing the body to temporarily adjust to situations of anemia or high metabolic demand. It is important to emphasize that blood transfusions should not be based on fixed values, but rather on individual metabolic needs. Strategies to reduce myocardial consumption and monitor macro and micro hemodynamics help in making rational decisions. Individualizing treatment and considering factors such as blood viscosity in relation to the benefits of transfusion are increasingly relevant to optimize therapy and minimize risks, especially in complex clinical scenarios, such as neurocritical patients and trauma victims.

Ischemic preconditioning increases spinal excitability and voluntary activation during maximal plantar flexion contractions in men.

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Cardiac Output and Stroke Volume Assessments by Transthoracic Echocardiography and Pulse index Continuous Cardiac Output Monitor in Critically ill Adult Patients: A Comparative Study.

PURPOSE: Bedside transthoracic echocardiography (TTEcho) is a noninvasive cardiac output (CO) monitoring method that has grown recently. However, there are questions regarding its accuracy compared to invasive methods. We aimed to evaluate the agreement and correlation of TTEcho and pulse index continuous CO (PiCCO) monitor measurements for CO and systolic volume (SV) in critically ill patients. METHODS: This prospective experimental study included consecutive adult patients who required invasive hemodynamic monitoring admitted at an intensive care unit in the Federal District, Brazil, from January/2019 to January/2021. Correlation and agreement between SV and CO measurements by PiCCO and TTEcho were performed using the Spearman correlation and the Bland-Altman analysis. RESULTS: The study enrolled 29 patients, with adequate TTEcho evaluations in all patients. There were very strong correlations between CO-TTEcho and CO-PiCCO (r = 0.845, P < .001) and SV-TTEcho and SV-PiCCO (r = 0.800, P < .001). TTEcho estimations for CO and SV were feasible within the limits of agreement in 96.6% (28/29) compared to PiCCO. The mean difference between CO-PiCCO and CO-TTEcho was 0.250 L/min (limits of agreement: -1.083 to 1.583 L/min, percentage error: 21.0%), and between SV-PiCCO and SV-TTEcho was 2.000 mL (limits of agreement: -16.960 to 20.960, percentage error: 24.3%). The reduced cardiac index (CI) measurements by TTEcho showed an accuracy of 89.7% (95% IC: 72.6%-97.8%) and an F1 score of 92.7% (95% IC: 75.0%-98.0%), considering the CI-PiCCO as the gold standard. CONCLUSION: Echocardiographic measurements of CO and SV are comparable to measurements by PiCCO. These results reinforce echocardiography as a reliable tool to evaluate hemodynamics in critically ill patients.

Insuficiencia cardíaca de alto gasto asociada a fístula arteriovenosa: caso clínico / High output heart failure associated with arteriovenous fistula: clinical case / Insuficiência cardíaca de alto débito associada a fístula arteriovenosa: caso clínico

La creación de una fístula arteriovenosa (FAV) determina un incremento del gasto cardíaco, cuya magnitud está relacionada con el tamaño del cortocircuito. En el escenario adecuado esta puede conducir al desarrollo de insuficiencia cardíaca (IC) con alto gasto cardiaco. Se presenta el caso de un paciente que desarrolla IC luego de la confección de una FAV para hemodiálisis crónica y sus implicancias clínicas posteriores. Se revisan aspectos diagnósticos y terapéuticos referidos a la IC de alto gasto.

The creation of an arteriovenous fistula (AVF) determines an increase in cardiac output, the magnitude of which is related to the size of the shunt. In the right scenario, this can lead to the development of heart failure (HF) with high cardiac output. The case of a patient who develops HF after creating an AVF for chronic hemodialysis and its subsequent clinical implications is presented. Diagnostic and therapeutic aspects related to high-output HF are reviewed.

A criação de uma fístula arteriovenosa (FAV) determina aumento do débito cardíaco, cuja magnitude está relacionada ao tamanho do shunt. No cenário certo, isso pode levar ao desenvolvimento de insuficiência cardíaca (IC) com alto débito cardíaco. É apresentado o caso de um paciente que desenvolve IC após confecção de FAV para hemodiálise crônica e suas subsequentes implicações clínicas. Aspectos diagnósticos e terapêuticos relacionados à IC de alto débito são revisados.

Consensus of the Brazilian association of hematology, hemotherapy and cellular therapy on patient blood management: Anemia tolerance mechanisms

Abstract Understanding the physiological concepts of oxygen delivery is essential to discern the mechanisms that influence its increase, reduction or maintenance in the body. This text explores the different mechanisms that help maintain oxygen delivery even in the face of reduced hemoglobin levels. Adequate oxygen delivery ensures tissue and metabolic balance, which is crucial to avoid harmful consequences such as metabolic acidosis and cellular dysoxia. The complex interaction between variables such as cardiac output, hemoglobin and heart rate (HR) plays a fundamental role in maintaining oxygen delivery, allowing the body to temporarily adjust to situations of anemia or high metabolic demand. It is important to emphasize that blood transfusions should not be based on fixed values, but rather on individual metabolic needs. Strategies to reduce myocardial consumption and monitor macro and micro hemodynamics help in making rational decisions. Individualizing treatment and considering factors such as blood viscosity in relation to the benefits of transfusion are increasingly relevant to optimize therapy and minimize risks, especially in complex clinical scenarios, such as neurocritical patients and trauma victims.

Levosimendan: efficacy and safety in pediatric heart failure treatment

SUMMARY OBJECTIVE: The objective of this study was to assess the effectiveness and safety of levosimendan as an alternative treatment for pediatric patients with decompensated heart failure unresponsive to conventional inotropes and to emphasize its role in enhancing cardiovascular stability. METHODS: A total of 15 pediatric patients with decompensated heart failure, stemming from acute fulminant myocarditis (53.3%) and post-congenital heart disease surgery complications (46.7%), received levosimendan. The evaluation focused on adverse effects, respiratory support requirements, and concurrent inotropic medication use during levosimendan treatment. Key cardiovascular parameters were assessed at 0, 6, 12, and 24 h post-levosimendan infusion. RESULTS: Levosimendan administration significantly improved key cardiovascular metrics. Left ventricular ejection fraction increased notably from 45±14.8% to 58±15.6% at 24 h (p<0.001). Systolic and diastolic blood pressures rose significantly, with systolic increasing from 79 (68-90) to 98 (89-109) mmHg and diastolic from 47 (40-57) to 66 (54-76) mmHg by 24 h (p<0.001). Heart rate decreased from 162 (111-175) to 132 (99-148) bpm (p=0.02), and lactate levels significantly decreased from 4.15 (2.3-6.5) to 1.85 (0.8-2.6) mmol/L within 6 h (p<0.001). CONCLUSION: Levosimendan demonstrates its significance in managing pediatric heart failure, indicating its safety and potential to enhance cardiac outcomes by reducing reliance on traditional inotropes.

Cardiac output and the pharmacology of general anesthetics: a narrative review

The relationship between cardiac output and anesthetic drugs is important to anesthesiologists, since cardiac output determines the speed with which a drug infused into the bloodstream reaches its target and the intensity of the drug's effect. But rather than focus on how anesthetic drugs affect cardiac output, this narrative review focuses on how changes in cardiac output affect the pharmacokinetics and pharmacodynamics of general anesthetics during the three phases of anesthesia. At induction, an increase in cardiac output shortens both the onset time of propofol for hypnosis and the neuromuscular blocking effect of rapid-acting neuromuscular blockers, favoring the conditions for rapid sequence intubation. During maintenance, changes in cardiac output are followed by opposite changes in the drug plasma concentration of anesthetic drugs. Thus, an increase in cardiac output followed by a decrease in the plasma concentration of the anesthetic could expose the patient to a real risk of intraoperative awakening, which can be avoided by increasing the dose of hypnotic drugs. At emergence, an increase in cardiac output secondary to an increase in pC02 allows for a more rapid recovery from anesthesia. The pC02 can be increased by adding CO2 to the respiratory circuit, lowering the ventilatory rate, or placing the patient on partial rebreathing. Finally, the reversal action of sugammadex for rocuronium-induced neuromuscular block can be shortened by increasing the cardiac output.

La relación entre el gasto cardíaco y los fármacos anestésicos es importante para los anestesiólogos puesto que el gasto cardíaco determina la velocidad con la cual un medicamento que se infunde al torrente sanguíneo llega a su diana y la intensidad del efecto del agente. Pero en lugar de concentrarnos en cómo los fármacos anestésicos afectan el gasto cardíaco, esta revisión narrativa se enfoca en cómo los cambios en el gasto cardíaco afectan la farmacocinética y la farmacodinámica de los agentes anestésicos generales durante las tres fases de la anestesia. En el momento de la inducción, un incremento en el gasto cardíaco acorta tanto el tiempo de inicio del efecto del propofol para la hipnosis como el efecto del bloqueo neuromuscular causado por los bloqueadores neuromusculares de acción rápida, favoreciendo las condiciones para la intubación de secuencia rápida. Durante la fase de mantenimiento, los cambios en el gasto cardíaco vienen seguidos de cambios opuestos en la concentración plasmática del medicamento de los agentes anestésicos. Por lo tanto, un aumento del gasto cardíaco, seguido de una reducción en la concentración plasmática del anestésico, podría exponer al paciente a un riesgo real de despertar intraoperatorio, lo cual puede evitarse aumentando la dosis de los fármacos hipnóticos. En la educción, un aumento en el gasto cardíaco secundario al incremento en el pCO2 permite una recuperación más rápida de la anestesia. El pCO2 puede aumentar agregando CO2 al circuito de la respiración, reduciendo la tasa ventilatoria, o colocando al paciente en re-inhalación parcial. Finalmente, la acción de reversión de sugammadex en caso de bloqueo neuromuscular inducido por rocuronio, puede acortarse aumentando el gasto cardíaco.

Supervivencia de pacientes con síndrome de bajo gasto cardiaco en el periodo posoperatorio / Survival of patients with low cardiac output syndrome in the postoperative period i: en

Introducción: La intervención quirúrgica cardiaca es compleja, pero con resultados satisfactorios para el paciente, pues incrementa su supervivencia y calidad de vida. El síndrome de bajo gasto cardiaco en el periodo posoperatorio es una de las entidades que ensombrece el pronóstico y eleva los índices de morbilidad y mortalidad en dichos pacientes. Objetivo: Estimar la supervivencia de los pacientes con síndrome de bajo gasto cardiaco en el periodo posoperatorio según variables clínicas y ecocardiográficas. Métodos: Se realizó una investigación de cohorte de supervivencia en 56 pacientes operados del corazón, diagnosticados con síndrome de bajo gasto cardiaco posoperatorio, quienes fueron atendidos en el Centro de Cardiología y Cirugía Cardiovascular de Santiago de Cuba, desde enero del 2019 hasta noviembre del 2021. Resultados: Predominaron el grupo etario de 65 o más años (60,7 %), la diabetes mellitus (44,6 %) como antecedente patológico personal y los pacientes con fracción de eyección de 45 % o más, quienes presentaron mayor cantidad de decesos (29,8 %). La función del ventrículo derecho afectada se halló en 52,6 % de los fallecidos. El tiempo de circulación extracorpórea de 90 minutos o más primó en 67,9 % de los afectados, de los cuales 42,1 % murieron. Conclusiones: Se observó que la diabetes mellitus, el tiempo de circulación extracorpórea y el sangrado perioperatorio prolongados, así como la función sistólica biventricular se relacionaron con el pronóstico del síndrome de bajo gasto cardiaco en el periodo posoperatorio.

Introduction: Heart surgical intervention is complex, but with satisfactory results for the patient, because it increases his survival and life quality. The low cardiac output syndrome in the postoperative period is one of the entities that darkens the prognosis of this operation and elevates the morbidity and mortality indexes in these patients. Objective: To estimate the survival of patients with low cardiac output syndrome in the postoperative period according to clinical and echocardiographyc variables. Methods: A cohort investigation of survival in 56 operated patients was carried out, who were diagnosed with postoperative low cardiac output syndrome and were assisted in the Cardiology and Cardiovascular Surgery Center of Santiago de Cuba, from January, 2019 to November, 2021. Results: There was prevalence of the 65 years and over age group (60.7%), the diabetes mellitus (44.6%) as personal pathological history and patients with ejection fraction of 45% or more who presented higher quantity of deaths (29.8%). The function of the affected right ventricle was found in 52.6% of deaths. The time of extracorporeal circulation of 90 minutes or more prevailed in 67.9% of those affected, of whom 42.1% died. Conclusions: It was observed that diabetes mellitus, the time of extracorporeal circulation and the long perioperative bleeding, as well as the biventricular systolic function was related to the prognosis of low cardiac output syndrome in the postoperative period.

Estimate of lysine nutritional requirements for Japanese quail breeders.

Background: Japanese quail breeders are the basis for genetic improvement and multiplication for commercial layers, however, there have been no known studies on the optimal lysine level for these birds. Thus, study the egg output response to the lysine (Lys) supply using different e-functions and evaluate the that best fit, have allowed the partition the lysine requirements for maintenance, both weight and egg output maximum. Methods: The objectives of this study were to identify the responses to various Lys levels, identify the functions related to these responses and determine the ideal Lys intake amount for Japanese quail breeders. A completely randomized design of seven treatments with seven replicated was used. Treatments consisted of diet supplementation by Lys in concentrations of 16.8, 11.8, 8.4, 6.7, 5.0, 3.4, and 1.7 g/kg. Six exponential models were adjusted. Results: The level of Lys was found to affect bird responses (P < 0.001). The birds responded to the levels provided, allowing for the creation of a lysine response curve. A monomolecular function with four parameters was balanced against the statistics of adjustment and selection of models. It was possible to estimate the level of lysine required for maintenance as 133 ± 2 mg/kg BW0.67, and based an average of 41% efficiency, 22 mg Lys produced 1 g of egg output (EO). The daily intake calculated by the monomolecular factorial model was 284 mg Lys for a bird with 0.170 kg body weight and production of 10 g EO/day. The four-parameter monomolecular function proposed in this study is adequate for interpreting the animal response and calculating lysine intake for breeders.