The Role of Ultrasonographic Inferior Vena Cava Measurement in the Volume-Based Classification of Patients With Hyponatremia.

OBJECTIVES: To demonstrate the role of inferior vena cava (IVC) collapsibility in the assessment of volume status in hyponatremic critically ill patients in the emergency department (ED) with bedside IVC imaging and to predict volume status with response to fluid therapy. METHODS: A prospective 110 hypotonic hyponatremic patients aged >18 years with a serum sodium level under 125 mEq/L and at least one symptom of hyponatremia, who presented or referred to the ED was conducted. Demographical, clinical, and laboratory characteristics with bedside measurement of IVC diameter of patients were recorded. Volume status was divided into 3 subgroups: hypovolemic-G1, euvolemic-G2, and hypervolemic-G3. An ED trainee with a certification to perform basic and advanced ultrasonography (USG) training carried out the USG examinations. A diagnostic algorithm approach was made according to the results. RESULTS: Symptom severity was significantly greater in the hypervolemic group than the other groups (P = .009 and P = .034, respectively). Systolic blood pressure (SBP) and mean arterial pressure (MAP) were significantly lower in the hypovolemic group compared with the other groups (P < .001 and P = .003, respectively). There was a significant difference between the ultrasonographically measured IVC min, IVC max, and mean IVC values across the three volume-based groups (P < .001). CONCLUSION: Considering the diversity of physical examination (PE) findings, with the highly heterogenous nature of hyponatremia, a new measurable algorithm can be developed on the basis of contemporary hyponatremic patient management guidelines.

A comprehensive echocardiographic analysis during simulated hypovolaemia: An observational study.

BACKGROUND: Peri-operative and critically ill patients often experience mild to moderate hypovolaemic shock with preserved mean arterial pressure (MAP), heart rate (HR) and decreased stroke volume index (SVI). OBJECTIVES: The aim of this study was to evaluate echocardiographic parameters during simulated mild to moderate central hypovolaemia. DESIGN: This was a prospective preclinical study. SETTING: Laboratory trial performed in Charité-Universitätsmedizin Berlin, Germany. PATIENTS AND METHODS: Thirty healthy male volunteers underwent graded central hypovolaemia using a lower body negative pressure (LBNP) chamber with a stepwise decrease to simulate a mild (-15 mmHg), mild-to-moderate (-30 mmHg), and moderate state of hypovolaemic shock (-45 mmHg). During every stage, a transthoracic echocardiography examination (TTE) was performed by a certified examiner. MAIN OUTCOME MEASURES: Systolic and diastolic myocardial performance markers, as well as cardiac volumes were recorded during simulated hypovolaemia and compared to baseline values. RESULTS: During simulated hypovolaemia via LBNP, SVI decreased progressively at all stages, whereas MAP and HR did not consistently change. Left ventricular (LV) ejection fraction decreased at -30 and -45 mmHg. Simultaneously with SVI decline, LV global longitudinal strain (LV GLS), tricuspid annular plain systolic excursion (TAPSE), and right ventricular RV S' and left-atrial end-systolic volume (LA ESV) decreased compared to baseline at all stages. CONCLUSIONS: In this study, simulated central hypovolaemia using LBNP did not induce consistent changes in MAP and HR. SVI decreased and was associated with deteriorated right- and left-ventricular function, observed with echocardiography. The decreased filling status was characterised by decreased LA ESV. CLINICAL TRIAL NUMBER: ClinicalTrials.gov Identifier: NCT03481855.

Hepatorenal syndrome misdiagnosis may be reduced using inferior vena cava ultrasound to assess intravascular volume and guide management.

Hepatorenal syndrome (HRS) is a diagnosis of exclusion defined as acute kidney injury (AKI) with cirrhosis and ascites, with serum creatinine unresponsive to standardized volume administration and diuretic withdrawal. Persistent intravascular hypovolemia or hypervolemia may contribute to AKI and be revealed by inferior vena cava ultrasound (IVC US), which may guide additional volume management. Twenty hospitalized adult patients meeting HRS-AKI criteria had IVC US to assess intravascular volume after receiving standardized albumin administration and diuretic withdrawal. Six had IVC collapsibility index (IVC-CI) ≥50% and IVCmax ≤0.7 cm suggesting intravascular hypovolemia, 9 had IVC-CI <20% and IVCmax >0.7 cm suggesting intravascular hypervolemia, and 5 had IVC-CI ≥20% to <50% and IVCmax >0.7 cm. Additional volume management was prescribed in the 15 patients with either hypovolemia or hypervolemia. After 4-5 days, serum creatinine levels decreased ≥20% without hemodialysis in 6 of 20 patients - 3 with hypovolemia received additional volume, and 2 with hypervolemia plus one with 'euvolemia' and dyspnea were volume restricted and received diuretics. In the other 14 patients, serum creatinine failed to persistently decrease ≥20% or hemodialysis was required indicating that AKI did not improve. In summary, fifteen of 20 patients (75%) were presumed to have intravascular hypovolemia or hypervolemia by IVC ultrasound. Six of the 20 patients (40%) improved AKI by 4-5 days of follow-up with additional IVC US-guided volume management, and thus had been misdiagnosed as HRS-AKI. IVC US may more accurately define HRS-AKI as being neither hypovolemic nor hypervolemic, and guide volume management, decreasing the frequency of HRS-AKI misdiagnosis.

Abdominal ultrasound and VExUS score in critical care.

The use of ultrasound while caring for critically ill patients has been increasing exponentially in the last two decades and now is an essential component of intensive care practice. Abdominal ultrasound is an established technique in other specialties, but its use in intensive care has lagged behind other ultrasound modalities. However, its potential role in the diagnosis and management of patients will make it an invaluable tool for intensivists. The main use of abdominal ultrasound at the bedside is for free fluid detection in trauma patients. But abdominal ultrasound can also help us diagnose patients with abdominal pain, hypovolemia or anuria, and it can guide us during procedures such as paracentesis or bladder catheter and gastric tube placement.

Reliability of Pre-Induction Inferior Vena Cava Assessment with Ultrasound for the Prediction of Post-Induction Hypotension in Neurosurgical Patients Undergoing Intracranial Surgery.

Background: Hypotension is one of the most common complications following induction of general anesthesia. Preemptive diagnosis and correcting the hypovolemic status can reduce the incidence of post-induction hypotension. However, an association between preoperative volume status and severity of post-induction hypotension has not been established in neurosurgical patients. We hypothesized that preoperative ultrasonographic assessment of intravascular volume status can be used to predict post-induction hypotension in neurosurgical patients. Our study objective was to establish the relationship between pre-induction maximum inferior vena cava (IVC) diameter, collapsibility index (CI), and post-induction reduction in mean arterial blood pressure in neurosurgical patients. Materials and Methods: A prospective observational study was conducted including 100 patients undergoing elective intracranial surgeries. IVC assessment was done before induction of general anesthesia. Receiver operating characteristic (ROC) curve analysis was used to determine the cutoff values of maximum and minimum IVC diameter (IVCDmax and IVCDmin, respectively) and CI for prediction of hypotension. Results: Post-induction hypotension was observed in 41% patients. Patients with small IVCDmax and higher CI% developed hypotension. The areas under the ROC curve (AUCs) were 0.64 (0.53-0.75) for IVCDmax and 0.69 (0.59-0.80) for IVCDmin. The optimal cutoff values were1.38 cm for IVCDmax and 0.94 cm for IVCDmin. The AUC for CI was 0.65 (0.54-0.77) and the optimal cutoff value was 37.5%. Conclusion: Pre-induction IVC assessment with ultrasound is a reliable method to predict post-induction hypotension resulting from hypovolemia in neurosurgical patients.

Internal jugular vein ultrasound for the diagnosis of hypovolemia and hypervolemia in acutely ill adults: a systematic review and meta-analysis.

Accurate volume status assessments allow physicians to rapidly implement therapeutic measures in acutely unwell patients. However, existing bedside diagnostic tools are often unreliable for assessing intravascular volume. We searched PUBMED, EMBASE, CENTRAL, and Web of Science for English language articles without date restrictions on January 20, 2022. Studies reporting the diagnostic accuracy of IJV-US for hypovolemia and/or hypervolemia in an acute care setting were screened for inclusion. We included studies using any method of IJV-US assessment as the index test, compared against any reference standard. We fitted hierarchical summary receiver operating characteristic (HSROC) models for meta-analysis of diagnostic test accuracy, separately for hypovolemia and hypervolemia. Two reviewers independently extracted data and assessed risk of bias using QUADAS-2. We assessed certainty of evidence using the GRADE approach. A total of 26 studies were included, of which 19 studies (956 patients) examined IJV-US for hypovolemia and 13 studies (672 patients) examined IJV-US for hypervolemia. For the diagnosis of hypovolemia, IJV-US had a pooled sensitivity of 0.82 (95% CI 0.76 to 0.87; moderate-certainty evidence) and specificity of 0.82 (95% CI 0.73 to 0.88; moderate-certainty evidence). Measurement of IJV collapsibility indices had higher diagnostic accuracy (sensitivity 0.85, 95% CI 0.80 to 0.89; specificity 0.78, 95% CI 0.64 to 0.88) than static IJV indices (sensitivity 0.73, 95% CI 0.60 to 0.82; specificity 0.70, 95% CI 0.48 to 0.86). For the diagnosis of hypervolemia, IJV-US had a pooled sensitivity of 0.84 (95% CI 0.70 to 0.92; moderate-certainty evidence) and specificity of 0.70 (95% CI 0.55 to 0.82; very low-certainty evidence). IJV-US has moderate sensitivity and specificity for the diagnosis of hypervolemia and hypovolemia. Randomized controlled trials are needed to determine the role of IJV-US for guiding therapeutic interventions aimed at optimizing volume status.

A wireless ultrasound patch detects mild-to-moderate central hypovolemia during lower body negative pressure.

BACKGROUND: We have developed a wireless, wearable Doppler ultrasound system that continuously measures the common carotid artery Doppler pulse. A novel measure from this device, the Doppler shock index, accurately detected moderate-to-severe central blood volume loss in a human hemorrhage model generated by lower body negative pressure. In this analysis, we tested whether the wearable Doppler could identify only mild-to-moderate central blood volume loss. METHODS: Eleven healthy volunteers were recruited and studied in a physiology laboratory at the Mayo Clinic. Each participant underwent a lower body negative protocol in duplicate. Carotid Doppler measures including Doppler shock indices were compared with blood pressure and the shock index for their ability to detect both 10% and 20% reductions in stroke volume. RESULTS: All carotid Doppler measures were better able to detect diminishing stroke volume than either systolic or mean arterial pressure. Falling carotid artery corrected flow time and rising heart rate/corrected flow time (DSI FTc ) were the most sensitive measures for detecting 10% and 20% stroke volume reductions, respectively. The area under the receiver operator curves (AUROCs) for all shock indices was at least 0.86; however, the denominators of the two Doppler shock indices (i.e., the corrected flow time and velocity time integral) had AUROCs ranging between 0.81 and 0.9, while the denominator of the traditional shock index (i.e., systolic blood pressure) had AUROCs between 0.54 and 0.7. CONCLUSION: The wearable Doppler ultrasound was able to continuously measure the common carotid artery Doppler pulse. Carotid Doppler measures were highly sensitive at detecting both 10% and 20% stroke volume reduction. All shock indices performed well in their diagnostic ability to measure mild-to-moderate central volume loss, although the denominators of both Doppler shock indices individually outperformed the denominator of the traditional shock index. LEVEL OF EVIDENCE: Diagnostic test or criteria; Level III.

The role of tricuspite annular plane systolic excursion as a marker of hypovolemia in healthy blood donor volunteers.

AIM: The aim of this study is to compare the diameter of the inferior vena cava with tricuspid annular plane systolic excursion (TAPSE) measurement in order to determine the volume loss before and after blood donation in healthy volunteers. METHODS: This Institutional Review Board-approved single center, prospective, cross-sectional study included 60 healthy blood donors donating in a tertiary care hospital's blood bank. After obtaining written consent, systolic, diastolic, and mean arterial blood pressures along with pulse rate of the donors were measured in sitting and supine positions by the attending physician, then, inferior vena cava (IVC) and TAPSE measurements were made before and after blood donation. RESULTS: Statistically significant differences was found between standing systolic blood pressure and pulse rate, lying systolic blood pressure and pulse rate, IVC and TAPSE values before and after blood donation (p < 0.05). There was no difference between the other variables before and after blood donation. CONCLUSION: Our study revealed that, low IVC and TAPSE values correlated in determining blood loss after blood donation. TAPSE may be useful to predict blood loss in early stages of hypovolemic shock.

Measuring the ratio of femoral vein diameter to femoral artery diameter by ultrasound to estimate volume status.

BACKGROUND: Currently, the accepted effective method for assessing blood volume status, such as measuring central venous pressure (CVP) and mean pulmonary artery pressure (mPAP), is invasive. The purpose of this study was to explore the feasibility and validity of the ratio of the femoral vein diameter (FVD) to the femoral artery diameter (FAD) for predicting CVP and mPAP and to calculate the cut-off value for the FVD/FAD ratio to help judge a patient's fluid volume status. METHODS: In this study, 130 patients were divided into two groups: in group A, the FVD, FAD, and CVP were measured, and in group B, the FVD, FAD, and mPAP were measured. We measured the FVD and FAD by ultrasound. We monitored CVP by a central venous catheter and mPAP by a Swan-Ganz floating catheter. Pearson correlation coefficients were calculated. The best cut-off value for the FVD/FAD ratio for predicting CVP and mPAP was obtained according to the receiver operating characteristic (ROC) curve. RESULTS: The FVD/FAD ratio was strongly correlated with CVP (R = 0.87, P < 0.0000) and mPAP (R = 0.73, P < 0.0000). According to the ROC curve, an FVD/FAD ratio ≥ 1.495 had the best test characteristics to predict a CVP ≥ 12 cmH2O, and an FVD/FAD ratio ≤ 1.467 had the best test characteristics to predict a CVP ≤ 10 cmH2O. An FVD/FAD ratio ≥ 2.03 had the best test characteristics to predict an mPAP ≥ 25 mmHg. According to the simple linear regression curve of the FVD/FAD ratio and CVP, when the predicted CVP ≤ 5 cmH2O, the FVD/FAD ratio was ≤ 0.854. CONCLUSION: In this study, the measurement of the FVD/FAD ratio obtained via ultrasound was strongly correlated with CVP and mPAP, providing a non-invasive method for quickly and reliably assessing blood volume status and providing good clinical support.

Need for Objective Assessment of Volume Status in Critically Ill Patients with COVID-19: The Tri-POCUS Approach.

As the coronavirus disease 2019 (COVID-19) continues to spread across the globe, the knowledge of its epidemiology, clinical features, and management is rapidly evolving. Nevertheless, the data on optimal fluid management strategies for those who develop critical illness remain sparse. Adding to the challenge, the fluid volume status of these patients has been found to be dynamic. Some present with several days of malaise, gastrointestinal symptoms, and consequent hypovolemia requiring aggressive fluid resuscitation, while a subset develop acute respiratory distress syndrome with renal dysfunction and lingering congestion necessitating restrictive fluid management. Accurate objective assessment of volume status allows physicians to tailor the fluid management goals throughout this wide spectrum of critical illness. Conventional point-of-care ultrasonography (POCUS) enables the reliable assessment of fluid status and reducing the staff exposure. However, due to specific characteristics of COVID-19 (e.g., rapidly expanding lung lesions), a single imaging method such as lung POCUS will have significant limitations. Herein, we suggest a Tri-POCUS approach that represents concurrent bedside assessment of the lungs, heart, and the venous system. This combinational approach is likely to overcome the limitations of the individual methods and provide a more precise evaluation of the volume status in critically ill patients with COVID-19.

Vena cava inferior como factor predictor del shock en trauma: medición ecográfica / Inferior vena cava as a predictor of shock in trauma patients: sonographic measurement

Resumen Objetivo Establecer la medición ecográfica del diámetro de la vena cava inferior como factor predictor del shock en pacientes politraumatizados. Materiales y Método Estudio de corte transversal donde se determinó la medición ecográfica de la vena cava inferior a 40 pacientes que ingresaron a la Unidad de Politraumatizados (UPT) del Hospital General del Este "Dr. Domingo Luciani", en el período entre enero y abril de 2018. Se seleccionaron 2 grupos; el grupo 1: pacientes en shock , aquellos con tensión arterial sistólica menor a 90 mm Hg al ingreso, y el grupo 2: pacientes controles que mantuvieron cifras tensionales normales. El estudio de imagen de la vena cava inferior se realizó con el equipo de ecografía ALOKA prosound SSD-a5 y con el ultrasonido portátil MicroMaxx SonoSite , en el cual se midió el índice de colapsabilidad. Los hallazgos se registraron en la hoja de recolección de datos. El análisis estadístico se hizo con la prueba de t de student para muestras independientes y la valoración de puntos de corte diagnóstico se hizo con la prueba de ROC. Resultados La media del Índice de colapsabilidad (IC) de la VCI para el grupo control y de shock fue de 26 ± 12,7% y de 58,5 ± 5,9%, respectivamente; El índice de colapsabilidad fue > 50% en todos los pacientes del grupo de shock . Conclusiones La medición del diámetro de la VCI es un predictor de shock , siendo el IC el parámetro más sensible y específico.

Aim To establish the sonographic measurement of the diameter of the inferior vena cava as a predictor of shock in trauma patients. Materials and Method A cross-sectional study to determined the sonographic measurement of the inferior vena cava to 40 patients attended at Hospital Domingo Luciani trauma unit, in the period between January and April of 2018. Two groups were selected; group 1: shock patients, those with systolic blood pressure lower than 90 mm Hg, and the group 2: control patients that kept normal blood pressure. The image study of the inferior vena cava was carried out with the ALOKA prosound ultrasound equipment SSD a5 and with the portable ultrasound MicroMaxx SonoSite, in which the collapsibility index was measured. The findings were recorded in the data collection sheet. The statistical analysis proposed for the comparison of averages was made with the student's t-test for independent samples and the assessment of diagnostic cut-off points was made with a ROC curve. Results the mean of collapsability index of de IVC for control and shock group were 26 ± 12,7% and 58,5 ± 5,9%, respectively; The collapsability index (CI) was > 50% in all patients of shock group. Conclusions The measurement of the ICV diameter is a predictor of shock, being the IC the most sensitive and specific parameter.

Signs of post-traumatic hypovolemia on abdominal CT and their clinical importance: A systematic review.

PURPOSE: Our aim was to assess the findings of hypovolemia on abdominal CT that are most frequently seen in blunt abdominal trauma patients. When possible, we assessed the correlation of these CT signs with clinical outcome. METHODS: MEDLINE, CENTRAL and EMBASE were systematically searched. Two reviewers independently screened and included articles and performed the data-extraction. Primary outcomes of interest were the frequency of each sign and its correlation with mortality. Secondary outcomes were need for intervention, transfusion need, intensive care unit admission rate and length of stay. RESULTS: A flat inferior vena cava and an inferior vena cava halo, a diminished aortic calibre, shock bowel, altered enhancement of the liver, pancreas, adrenals, kidneys, spleen and gallbladder, peripancreatic fluid and splenic volume changes have been described in the setting of hypovolemic trauma patients to constellate a CT hypovolemic shock complex. It is argued that vascular signs represent the true hypovolemic state and the visceral signs represent hypoperfusion. There is no consensus on the frequency or clinical relevance of these signs, which at least partly can be explained by the heterogeneity in study design, study population, scanning protocols and outcome parameters. Available evidence suggests a good predictive value for occult shock and a higher mortality rate when a flat inferior vena cava is present. Evidence regarding the other signs is scarce. CONCLUSIONS: The hypovolemic shock complex is an entity of both vascular and visceral CT signs that can be seen in blunt trauma patients. It can offer guidance to a swift primary imaging survey in the acute trauma setting, allowing the radiologist to alert the treating physicians to possible pending hypovolemic shock.

Utilidad de la ecocardiografía transtorácica focalizada en emergencias hemodinámicas intraoperatorias / Usefulness of Focalized transthoracic ecocardiography in intraoperative hemodynamic emergencys

INTRODUCTION: Echocardiography represents one of the most important advances in the monitoring of critical patients. Initially available only in cardiovascular surgery, currently, there is transesophageal echocardiography (TEE) and transthoracic echocardiography (ETT) in non-cardiac surgery, for anesthesiologists. The advantages of ETT is a non-invasive tool, of lower cost than the transesophageal transducer and therefore more feasible to be overcrowded and available in the pavilion. OBJECTIVE: To evaluate the usefulness of TTE in patients with hemodynamic compromise during non-cardiac surgery. NATERIAL AND METHODS: In a prospective manner between April 2016 and September 2018, patients were studied who during their intraoperative period presented a compromise of their hemodynamic state, defined as an average blood pressure under 55 mm Hg, for more than 3 minutes and without response to the usual therapy based on vasopressors and volume. Each of these patients had a prospective protocol for focused ETT looking for the cause of this disorder, by a duly trained operator. RESULTS: 124 patients, with an average age of 67 years (range 42 to 93 years) were evaluated. In all cases, at least one echocardiographic window was obtained that allowed a diagnosis to be made and/or to guide the therapy. The main causes of hemodynamic compromise were hypovolemia (52%), poor left ventricular function (21%) and other causes such as pericardial effusion, suspected pulmonary thromboembolism, pulmonary pathology and suspected myocardial ischemia. DISCUSSION: The ETT could be a feasible tool to use in acute hemodynamic events, since it offers good quality windows that allow new decisions based on the diagnosis and also allows to guide the selected therapies. In addition, it has been shown to positively impact clinical behaviors in the perioperative period. ETT is a non-invasive monitor, reasonably easy to learn to use; In addition to directly visualizing cardiac structures, it allows differential diagnoses of the causes of intraoperative hypotension. The therapies can also be decided according to the echocardiographic images and control how they generate changes in the cardiac cavities and in the hemodynamic state of the patient.

INTRODUCCIÓN: La ecocardiografía representa uno de los más importantes avances en la monitorización de pacientes críticos. Inicialmente disponible sólo en cirugía cardiovascular, en la actualidad, se cuenta con ecocardiografía transesofágica (ETE) y ecocardiografía transtorácica (ETT) en cirugía no cardíaca, para los anestesiólogos. Las ventajas del ETT están en ser una herramienta no invasiva, de menor costo que el transductor transesofágico y, por lo tanto, más factible de ser masificada y estar disponible en pabellón. OBJETIVO: Evaluar la utilidad de ETT en pacientes con compromiso hemodinámico durante cirugía no cardiaca. MATERIAL Y MÉTODOS: En forma prospectiva entre abril de 2016 y septiembre del 2018, se estudiaron enfermos que durante su intraoperatorio presentaron compromiso de su estado hemodinámico, definido como una presión arterial media bajo 55 mm Hg, por más de 3 minutos y sin respuesta a la terapia habitual basada en vasopresores y volumen. A cada uno de estos enfermos se le realizó un protocolo prospectivo de ETT focalizado buscando la causa de esta alteración, por un operador debidamente entrenado. RESULTADOS: 124 pacientes, con edad promedio de 67 años (rango 42 a 93 años) fueron evaluados. En todos los casos se obtuvo al menos una ventana ecocardiográfica que permitió realizar un diagnóstico y/o guiar la terapia. Las principales causas de compromiso hemodinámico fueron hipovolemia (52%), mala función del ventrículo izquierdo (21%) y otras causas como derrame pericárdico, sospecha de tromboembolismo pulmonar, patología pulmonar y sospecha de isquemia miocárdica. La ETT podría ser una herramienta factible de utilizar en eventos hemodinámicos agudos, ya que ofrece ventanas de buena calidad que permiten tomar decisiones nuevas basadas en el diagnóstico y, además, permite guiar las terapias seleccionadas. Además, ha mostrado impactar de forma positiva las conductas clínicas en el perioperatorio. DISCUSIÓN: La ETT es un monitor no invasivo, razonablemente fácil de aprender a utilizar que además de visualizar de manera directa las estructuras cardíacas, permite realizar diagnósticos diferenciales de las causas de hipotensión intraoperatoria. Además, se puede decidir las terapias de acuerdo a las imágenes ecocardiográficas y controlar cómo éstas generan cambios en las cavidades cardíacas y en el estado hemodinámico del paciente.

Assessment of cerebral and renal autoregulation using near-infrared spectroscopy under normal, hypovolaemic and postfluid resuscitation conditions in a swine model: An observational study.

BACKGROUND: The impact of blood pressure changes on tissue oxygenation differs between vital organs and with blood volume conditions. OBJECTIVE: To assess cerebral and renal autoregulation simultaneously and compare the impact of blood pressure, hypovolaemia and fluid resuscitation on tissue oxygenation using near-infrared spectroscopy. DESIGN: Animal observational study. SETTING: An animal laboratory in Hamamatsu University School of Medicine, Hamamatsu, Japan, from April 2018 to August 2018. ANIMALS: Fifteen pigs, (mean ±â€ŠSD) 25.2 ±â€Š0.4 kg. INTERVENTIONS: The pigs were anaesthetised with 2.5% isoflurane and phenylephrine 0.5, 1, 2 and 5 µg kg min was administered in a stepwise fashion at 10-min intervals (baseline), followed by similar administration of sodium nitroprusside. Hypovolaemia was induced by a 600-ml bleed (33% of estimated total blood volume). Then phenylephrine was administered again (same protocol). Hypovolaemia was reversed by infusion of 600-ml hydroxyethyl starch. Phenylephrine and sodium nitroprusside were then administered again (same protocol). MAIN OUTCOME MEASURES: Average of the relation between mean arterial pressure (MAP) and cerebral or renal tissue oxygenation index (TOI) and individual TOI response during vasoactive drug infusions. RESULTS: The average relationship between MAP and cerebral or renal TOI both showed classic autoregulation patterns, whereas the renal TOI was more pressure-dependent than the cerebral TOI. Hypovolaemia shifted the relationship downward, reducing the cerebral and renal TOIs by approximately 5 and 20%, respectively, at similar MAPs. Subsequent fluid resuscitation preserved the autoregulatory pattern in both organs, not changing cerebral TOI but reducing renal TOI to 10% under baseline. TOI responses in both organs included paradoxical changes (tissue oxygenation changed inversely with MAP) in 60% of animals. Animals with paradoxical reactions maintained more stable cerebral and renal oxygenation. CONCLUSION: Renal oxygenation is more pressure-dependent than pressure-tolerant cerebral oxygenation, and autoregulation is not robust. Renal oxygenation decreased four-fold compared with cerebral oxygenation during hypovolaemia and two-fold during isovolaemic anaemia. Thus, paradoxical responses are part of normal autoregulatory function and beneficial for maintaining stable oxygenation.

Cerebral Blood Flow Response to Simulated Hypovolemia in Essential Hypertension: A Magnetic Resonance Imaging Study.

Hypertension is associated with raised cerebral vascular resistance and cerebrovascular remodeling. It is currently unclear whether the cerebral circulation can maintain cerebral blood flow (CBF) during reductions in cardiac output (CO) in hypertensive patients thereby avoiding hypoperfusion of the brain. We hypothesized that hypertension would impair the ability to effectively regulate CBF during simulated hypovolemia. In the present study, 39 participants (13 normotensive, 13 controlled, and 13 uncontrolled hypertensives; mean age±SD, 55±10 years) underwent lower body negative pressure (LBNP) at -20, -40, and -50 mmHg to decrease central blood volume. Phase-contrast MR angiography was used to measure flow in the basilar and internal carotid arteries, as well as the ascending aorta. CBF and CO decreased during LBNP (P<0.0001). Heart rate increased during LBNP, reaching significance at -50 mmHg (P<0.0001). There was no change in mean arterial pressure during LBNP (P=0.3). All participants showed similar reductions in CBF (P=0.3, between groups) and CO (P=0.7, between groups) during LBNP. There was no difference in resting CBF between the groups (P=0.36). In summary, during reductions in CO induced by hypovolemic stress, mean arterial pressure is maintained but CBF declines indicating that CBF is dependent on CO in middle-aged normotensive and hypertensive volunteers. Hypertension is not associated with impairments in the CBF response to reduced CO.

Comparison of inferior vena cava collapsibility, distensibility, and delta indices at different positive pressure supports and prediction values of indices for intravascular volume status

Background/aim: To compare the inferior vena cava (IVC) indices, identify their variation rates at positive pressure values and accurate predictive values for the volume status in patients with spontaneous respiration receiving different positive pressure support. Materials and methods: The study included 100 patients who were divided into 4 pressure support groups, according to the different pressure supports received, and 3 volume groups according to their CVP values. Ultrasonography was applied to all of the patients to define their IVC diameters at different pressure supports. Dynamic parameters were derived from the ultrasonographic assessment of the IVC diameter [collapsibility (CI-IVC), distensibility (dIVC), and delta (ΔIVC) indices]. Results: There were significant differences between the 3 indices (CI-IVC, dIVC, and ΔIVC) according to the pressure groups [(10/5), (10/0), (0/5), (t tube 0/0)]. The median value for the dIVC percentages was ≤18% for all of the positive pressure support hypervolemic groups, apart from the hypervolemic t tube group (19%). For the hypervolemic groups, the best estimation according to the cut-off value appeared to be for the dIVC. Values with the highest sensitivity for differentiation of the hypovolemic individuals were calculated with the dIVC. Conclusion: The dIVC had a more accurate predictive role in predicting the volume status when compared with the CI-IVC and ΔIVC, and may be used reliably with positive pressure supports.

Associations between changes in precerebral blood flow and cerebral oximetry in the lower body negative pressure model of hypovolemia in healthy volunteers.

Reductions in cerebral oxygen saturation (ScO2) measured by near infra-red spectroscopy have been found during compensated hypovolemia in the lower body negative pressure (LBNP)-model, which may reflect reduced cerebral blood flow. However, ScO2 may also be contaminated from extracranial (scalp) tissues, mainly supplied by the external carotid artery (ECA), and it is possible that a ScO2 reduction during hypovolemia is caused by reduced scalp, and not cerebral, blood flow. The aim of the present study was to explore the associations between blood flow in precerebral arteries and ScO2 during LBNP-induced hypovolemia. Twenty healthy volunteers were exposed to LBNP 20, 40, 60 and 80 mmHg. Blood flow in the internal carotid artery (ICA), ECA and vertebral artery (VA) was measured by Doppler ultrasound. Stroke volume for calculating cardiac output was measured by suprasternal Doppler. Associations of changes within subjects were examined using linear mixed-effects regression models. LBNP reduced cardiac output, ScO2 and ICA and ECA blood flow. Changes in flow in both ICA and ECA were associated with changes in ScO2 and cardiac output. Flow in the VA did not change during LBNP and changes in VA flow were not associated with changes in ScO2 or cardiac output. During experimental compensated hypovolemia in healthy, conscious subjects, a reduced ScO2 may thus reflect a reduction in both cerebral and extracranial blood flow.

Inspiratory collapse of the inferior vena cava and the kissing ventricle sign: markers of poor prognosis in emergency gastrointestinal bleeding. / El colapso inspiratorio de la vena cava inferior y la obliteración sistólica (kissing) ventricular izquierda: marcadores de mal pronóstico en la hemorragia gastrointestinal en urgencias.

OBJECTIVES: Gastrointestinal bleeding, one of the main reasons for emergency department visits, is associated with significant mortality, complications, and high health care spending. Studies have shown the usefulness of hemodynamic monitoring by ultrasound of the inferior vena cava (IVC), imaging of systolic obstruction of the left ventricle (the kissing sign), changes in cardiac output, or surrogates for cardiac output such as the left ventricular velocity time integral before and after a passive leg raise. There is currently no evidence for applying this approach to evaluating hypovolemia due to gastrointestinal bleeding. MATERIAL AND METHODS: We prospectively recruited 203 emergency department patients with gastrointestinal bleeding between August 2015 and April 2017; this sample size provided a 95% CI for a proportion of 5%, with a precision of 3% and expected losses of 15%. Recorded data were as follows: medical histories, observations during physical examinations, laboratory results, diagnostic variables, treatment details, clinical course, and ultrasound findings related to hemodynamics. RESULTS: Clinical course was worse in patients with evidence of hypovolemia such as a small (<1 cm) end-expiratory IVC diameter (IVCEE) or the kissing sign. Complications were more prevalent at 24 hours and 30 days, a finding that was not associated with the other clinical or laboratory variables commonly monitored. We also saw that both a small IVCEE and persistent inspiratory collapse of the IVC of more than 50% after a passive leg raise test might prove useful for identifying patients at risk for anemia at 24 hours, allowing time to start preventive measures. CONCLUSION: The analysis of IVCEE, inspiratory collapse of the IVC, or the kissing sign in combination with clinical and laboratory findings can facilitate the use of clinical practice algorithms that can encourage the efficient risk-based assignment of resources and improve prognosis.

OBJETIVO: La hemorragia digestiva (HD) constituye un problema médico con significativa morbimortalidad y elevado consumo de recursos sanitarios, y es uno de los motivos principales de consulta en los servicios de urgencias. Varios estudios han destacado la utilidad de la ecografía clínica en la monitorización hemodinámica, a partir del análisis de la vena cava inferior (VCI), visualizando la obliteración sistólica del ventrículo izquierdo ("kissing del VI") así como cambios en el gasto cardíaco (GC) o marcadores subrogados al GC como la integral velocidad tiempo (IVT) en el tracto de salida del VI, antes y después de la prueba de elevación pasiva de miembros inferiores (EPMI). En la actualidad, no hay evidencia directa relacionada con la aplicabilidad de este enfoque en la hipovolemia por HD. METODO: Entre agosto de 2015 y abril de 2017, se reclutaron prospectivamente 203 pacientes (nivel de confianza del 95%, precisión 3%, proporción 5%, pérdidas estimadas 15%), que consultaron en el servicio de urgencias por HD. Se recogieron los antecedentes médicos, la exploración física, los hallazgos analíticos, variables relacionadas con el diagnóstico, con el tratamiento, con la evolución clínica y variables ecográficas relacionadas con la situación hemodinámica. RESULTADOS: Los pacientes con datos de hipovolemia como un diámetro de VCI espiratorio (CAVAesp) < 1 cm o un "kissing del VI" presentaron peor evolución, con mayor presencia de complicaciones a las 24 horas y 30 días, hallazgo que no se observó con otros parámetros clínicos o analíticos comúnmente empleados. Además se observó que tanto la CAVAesp < 1 cm, como la persistencia del colapso inspiratorio de la VCI (CICAVA) > 50% tras la PLR podrían ser de utilidad para identificar a los pacientes en los que es esperable una anemización a las 24 horas. CONCLUSIONES: El análisis de marcadores ecográficos como la CAVAesp, CIVACA o el "kissing del VI", combinados con variables clínicas y de laboratorio, permitiría implementar algoritmos de actuación más eficientes y asignar mejor los recursos en función del perfil de riesgo, lo cual podría conducir a una mejora en el pronóstico.