Changes In Intravascular Volume Research Articles

Point of care ultrasound measurement of paralumbar caudal vena cava diameter and caudal vena cava to aortic ratio in hypovolemic dogs.

Accurate assessment of intravascular volume is critical for precise fluid prescription. In people, bedside or point of care ultrasound is used to measure the inferior vena cava, with or without paired aortic measurement, to estimate intravascular volume. To determine if point of care ultrasound measurement of the caudal vena cava (CVC) diameter or the CVC diameter to the abdominal aorta (Ao) diameter (CVC:Ao) at the paralumbar view are associated with changes in intravascular volume, mean arterial pressure (MAP), or cardiac output in normovolemic and hypovolemic dogs. 8 purpose-bred dogs. Pressure-targeted hemorrhagic shock was induced in purpose-bred dogs under general anesthesia. Dogs were exsanguinated to a mean arterial pressure of 40 mmHg, or a maximum 60% blood volume lost, then auto-transfused shed blood. At a left paralumbar view, longitudinal plane measurements of the abdominal CVC diameter and aortic diameter were obtained. Measurements were performed at 4 timepoints: baseline under anesthesia (TP1), after hemorrhagic shock was induced (TP2), after ½ of shed blood had been re-transfused (TP3), and post-resuscitation with completed re-transfusion (TP4). Additional variables collected included cardiac output using thermodilution and arterial blood pressure. CVC:Ao was not significantly different between timepoints and was not associated with changes in CO (p = 0.28) or MAP (p = 0.50). CVC diameter was significantly different between baseline (TP1) and hemorrhagic shock (TP2). CVC diameter was significantly different at TP2 compared to TP1 after controlling for the effect of CO (p = 0.03) and MAP (p = 0.001). Aortic diameter was also significantly different at TP2 (p = 0.002, p = 0.001) and TP3 (p = 0.023, p = 0.017) compared to TP1 after controlling for CO and MAP. Obtaining point of care ultrasound images for CVC:Ao measurement was feasible. With a marked decrease in intravascular volume, both CVC and Ao diameter decreased, resulting in an unchanged CVC:Ao. Despite changes in CVC and Ao diameters, these changes were not associated with measured changes in CO, emphasizing that CO is not a direct estimate of intravascular volume and is affected by many compensatory mechanisms. Additional studies are needed to determine the most accurate method for bedside measurement of intravascular volume status.

Prolonged Labor and Adverse Cardiac Outcomes in Pregnant Patients With Congenital Heart Disease

(Am J Obstet Gynecol. 2023;228(6):728.e1–728.e8) Congenital heart disease (CHD) is one of the most common types of birth defects and affects 8 to 9 per 1000 births. Many patients who have it are diagnosed in infancy, but some are not diagnosed until later in life. The number of patients with CHD who reach childbearing years has increased substantially. Pregnancy can pose difficult challenges, especially in labor and delivery. The physiologic changes that occur during delivery, including increased cardiac demand, rapid changes in intravascular volume, and blood loss, result in significant risk for patients with CHD. The European Registry of Pregnancy and Cardiac disease and the Cardiac Disease in Pregnancy 2 studies have demonstrated that the immediate postpartum period is the highest risk time for heart failure.

Predicting Lipid-Rich Plaque Progression in Coronary Arteries Using Multimodal Imaging and Wall Shear Stress Signatures.

Plaque composition and wall shear stress (WSS) magnitude act as well-established players in coronary plaque progression. However, WSS magnitude per se does not completely capture the mechanical stimulus to which the endothelium is subjected, since endothelial cells experience changes in the WSS spatiotemporal configuration on the luminal surface. This study explores WSS profile and lipid content signatures of plaque progression to identify novel biomarkers of coronary atherosclerosis. Thirty-seven patients with acute coronary syndrome underwent coronary computed tomography angiography, near-infrared spectroscopy intravascular ultrasound, and optical coherence tomography of at least 1 nonculprit vessel at baseline and 1-year follow-up. Baseline coronary artery geometries were reconstructed from intravascular ultrasound and coronary computed tomography angiography and combined with flow information to perform computational fluid dynamics simulations to assess the time-averaged WSS magnitude (TAWSS) and the variability in the contraction/expansion action exerted by WSS on the endothelium, quantifiable in terms of topological shear variation index (TSVI). Plaque progression was measured as intravascular ultrasound-derived percentage plaque atheroma volume change at 1-year follow-up. Plaque composition information was extracted from near-infrared spectroscopy and optical coherence tomography. Exposure to high TSVI and low TAWSS was associated with higher plaque progression (4.00±0.69% and 3.60±0.62%, respectively). Plaque composition acted synergistically with TSVI or TAWSS, resulting in the highest plaque progression (≥5.90%) at locations where lipid-rich plaque is exposed to high TSVI or low TAWSS. Luminal exposure to high TSVI, solely or combined with a lipid-rich plaque phenotype, is associated with enhanced plaque progression at 1-year follow-up. Where plaque progression occurred, low TAWSS was also observed. These findings suggest TSVI, in addition to low TAWSS, as a potential biomechanical predictor for plaque progression, showing promise for clinical translation to improve patient prognosis.

Mechanism-Based Modeling of Perioperative Variations in Hemoglobin Concentration in Patients Undergoing Laparoscopic Surgery.

Hemoglobin concentration ([Hb]) in the perioperative setting should be interpreted in the context of the variables and processes that may affect it to differentiate the dilution effects caused by changes in intravascular volume. However, it is unclear what variables and processes affect [Hb]. Here, we modeled the perioperative variations in [Hb] to identify the variables and processes that govern [Hb] and to describe their effects. We first constructed a mechanistic framework based on the main variables and processes related to the perioperative [Hb] variations. We then prospectively studied patients undergoing laparoscopic surgery, divided into 2 consecutive cohorts for the development and validation of the model. The study protocol consisted of serial measurements of [Hb] along with recordings of hemoglobin mass loss, blood volume loss, fluid infusion, urine volume, and inflammatory biomarkers measurements, up to 96 hours postoperatively. Mathematical fitting was performed using nonlinear mixed-effects. Additionally, we performed simulations to explore the effects of blood loss and fluid therapy protocols on [Hb]. We studied 154 patients: 118 enrolled in the development group and 36 in the validation group. We characterized the perioperative course of [Hb] using a mass balance model that accounted for hemoglobin losses during surgery, and a 2-compartment model that estimated fluid kinetics and intravascular volume changes. During model development, we found that urinary fluid elimination represented only 24% of the total fluid elimination, and that total fluid elimination was inhibited after surgery in a time-dependent manner and influenced by age. Also, covariate evaluation showed a significant association between the type of surgery and proportion of fluid eliminated via urine. In contrast, neither the type of infused solution, blood volume loss nor inflammatory biomarkers were found to correlate with model parameters. In the validation analysis, the model demonstrated a considerable predictive capacity, with 95% of the predicted [Hb] within -4.4 and +5.5 g/L. Simulations demonstrated that hemoglobin mass loss determined most of the postoperative changes in [Hb], while intravascular volume changes due to fluid infusion, distribution, and elimination induced smaller but clinically relevant variations. Simulated patients receiving standard fluid therapy protocols exhibited a hemodilution effect that resulted in a [Hb] decrease between 7 and 15 g/L at the end of surgery, and which was responsible for the lowest [Hb] value during the perioperative period. Our model provides a mechanistic and quantitative understanding of the causes underlying the perioperative [Hb] variations.

Detection of Postpartum Hemorrhage Using Compensatory Reserve Index in Patients Undergoing Cesarean Delivery.

Postpartum hemorrhage (PPH) is the leading cause of maternal death worldwide. Early recognition and management are imperative for improved outcomes. The compensatory reserve index (CRI) is a novel physiological parameter that trends changes in intravascular volume, by continuously comparing extracted photoplethysmogram waveforms to a reference model that was derived from a human model of acute blood loss. This study sought to determine whether the CRI pattern was differential between those who do and do not experience PPH during cesarean delivery and compare these results to the American Society of Anesthesiologists (ASA) standards for noninvasive monitoring. Parturients undergoing cesarean delivery were enrolled between February 2020 and May 2021. A noninvasive CRI monitor was applied to collect continuous CRI values throughout the intraoperative and immediate postpartum periods. Patients were stratified based on blood loss into PPH versus non-PPH groups. PPH was defined as a quantitative blood loss >1000 mL. Function-on-scalar (FoS) regression was used to compare trends in CRI between groups (PPH versus non-PPH) during the 10 to 60-minute window after delivery. Two subanalyses excluding patients who received general anesthesia and preeclamptics were performed. Fifty-one patients were enrolled in the study. Thirteen (25.5%) patients experienced PPH. Pregnant patients who experienced PPH had, on average, lower postdelivery CRI values (-0.13; 95% CI, -0.13 to -0.12; P < .001) than those who did not experience PPH. This persisted even when adjusting for preeclampsia and administration of uterotonics. The average mean arterial pressure (MAP) measurements were not statistically significant (-1.67; 95% CI, -3.57 to 0.22; P = .09). Similar trends were seen when excluding patients who underwent general anesthesia. When excluding preeclamptics, CRI values remained lower in those who hemorrhaged (-0.18; 95% CI, -0.19 to -0.17; P < .001). CRI detects changes in central volume status not distinguished by MAP. It has the potential to serve as a continuous, informative metric, notifying providers of acute changes in central volume status due to PPH during cesarean delivery.

Standardized blood volume changes monitored by capnodynamic hemodynamic variables: An experimental comparative study in pigs.

The capnodynamic method, based on Volumetric capnography and differential Fick mathematics, assess cardiac output in mechanically ventilated subjects. Capnodynamic and established hemodynamic monitoring parameters' capability to depict alterations in blood volume were investigated in a model of standardized hemorrhage, followed by crystalloid and blood transfusion. Ten anesthetized piglets were subjected to controlled hemorrhage (450 mL), followed by isovolemic crystalloid bolus and blood re-transfusion. Intravascular blood volume, and all hemodynamic variables, were determined twice after each intervention. The investigated hemodynamic variables were: cardiac output and stroke volume for capnodynamics and pulse contour analysis, respectively, pulse pressure and stroke volume variability and mean arterial pressure. One-way ANOVA and Tukey's test for multiple comparisons were used to identify significant changes. Trending was assessed by correlation and concordance. Concordance against intravascular volume changes for capnodynamic cardiac output and stroke volume were 96 and 94%, with correlations r = .78 and .68, (p < .0001) with significant changes for 6 and 5 of the 6 measuring points, respectively. Mean arterial pressure and pulse pressure variation had a concordance of 85% and 87%, r = .67 (p < .0001) and r = -.45 (p < .0001), respectively, and both changed significantly for 3 of 6 measuring points. Pulse contour stroke volume variation, stroke volume and cardiac output, showed concordance and correlation of 76%, r = -.18 (p = .11), 63%, r = .28 (p = .01) and 50%, r = .31 (p = .007), respectively and significant change for 1, 1 and 0 of the measuring points, respectively. Capnodynamic cardiac output and stroke volume did best depict the changes in intravascular blood volume. Pulse contour parameters did not follow volume changes in a reliable way.

Value of inferior vena cava diameter and inferior vena cava collapse index in the evaluation of peripartum volume: A prospective cohort study

ObjectiveThe maternal intravascular volume status assessed during and after gestation is valuable but challenging due to the influence of the substantial adaptive cardiovascular changes during pregnancy. The present study aimed to investigate the changes in the size of inferior vena cava (IVC) diameter and collapse index (IVC-CI) during perinatal delivery and whether it is affected by the change in intravascular volume during delivery. Study designA total of 31 full-term, singleton, and cephalic delivery women delivered by vagina with an estimated blood loss of >500 mL measured longitudinally between September 2019 and September 2020 in the Department of Obstetrics and Gynecology of The Third Hospital in China. The end-expiratory (IVCe) and end-inspiratory (IVCi) diameters of the inferior vena cava were measured at the first, second, and third stages of labor (T1, T2, and T3, respectively) and postpartum haemorrhage ≥500 mL (T4 and after rapid rehydration 500 mL (T5). The collapse index of IVC was calculated, and blood pressure and heart rate were measured. ResultsIVCe and IVC-CI changed significantly in a volume-dependent manner during the perinatal period (T1–T5; P < 0.05). IVCe narrowed significantly with volume reduction (after postpartum hemorrhage) and widened significantly with volume increase (after volume resuscitation). IVC-CI increases significantly with decreased capacity and decreases significantly with increased capacity. ConclusionThe width and collapse index of IVC reflect the circulatory volume changes during the parturient’s perinatal period with postpartum hemorrhage.

Intravascular, Interstitial and Intracellular Volume Changes During Short Term Deep Tissue Massage of the Calf: A Case Study.

The following case study demonstrates that the effectiveness of Deep Tissue Massage (DTM) can be monitored in real time with bioimpedance. DTM techniques are used as a medical treatment to help reduce swelling of the calves of congestive heart failure patients. Bioimpedance monitoring shows immediately how fluid is redistributed within the intravascular, interstitial and intracellular fluid compartments, and how long the redistribution lasts. Bioimpedance spectroscopy, as used in this study, is a non-invasive procedure that can be used to monitor compartment fluid volumes and changes during many fluid management procedures.

Temporal Changes in Electrolytes, Acid-Base, QTc Duration, and Point-of-Care Ultrasound during Inpatient Hemodialysis Sessions.

Of the more than 550,000 patients receiving maintenance hemodialysis (HD) in the United States, each has an average of 1.6 admissions annually (>880,000 inpatient HD sessions). Little is known about the temporal changes in laboratory values, ECGs, and intravascular and extravascular volume during inpatient HD sessions. In this prospective cohort study of hospitalized HD patients, we assessed intradialytic laboratory values (metabolic panels, blood gases, ionized calcium levels), ECGs, and sonographic measures of volume status. Among 30 participants undergoing HD (mean age 62 years; 53% men, 43% Black) laboratory values had the largest changes in the first hour of HD. There was no significant change in ionized calcium levels pre- to post-HD (change: -0.01±0.07, P=0.24); 12 of 30 and 17 of 30 patients had levels below the lower reference limit at the beginning and end of HD, respectively. The mean pH increased pre- to post-HD (change: 0.06±0.04, P<0.001); 21 of 30 had a pH above the upper reference limit post-HD. There was a trend toward longer median QTc duration from pre- to post-HD (change: 7.5 msec [-5 msec, 19 msec], P=0.07). The sum of B lines on lung ultrasound decreased from pre- to post-HD (median decrease: 3 [1, 7], P<0.01). The collapsibility index of the inferior vena cava increased pre- to post-HD (median increase: 4.8% [1.5%, 13.4%], P=0.01), whereas internal jugular vein diameter did not change (P=0.24). Among hospitalized patients undergoing HD, we found dynamic changes in laboratory values, QTc duration, and volume status. Further research is required to assess whether HD prescriptions can be tailored to alter these variations to potentially improve patient outcomes.

Use of Relative Blood Volume Monitoring to Reduce Intradialytic Hypotension in Hospitalized Patients Receiving Dialysis

Use of Relative Blood Volume Monitoring to Reduce Intradialytic Hypotension in Hospitalized Patients Receiving Dialysis

Critical Information from High Fidelity Arterial and Venous Pressure Waveforms During Anesthesia and Hemorrhage.

Peripheral venous pressure (PVP) waveform analysis is a novel, minimally invasive, and inexpensive method of measuring intravascular volume changes. A porcine cohort was studied to determine how venous and arterial pressure waveforms change due to inhaled and infused anesthetics and acute hemorrhage. Venous and arterial pressure waveforms were continuously collected, while each pig was under general anesthesia, by inserting Millar catheters into a neighboring peripheral artery and vein. The anesthetic was varied from inhaled to infused, then the pig underwent a controlled hemorrhage. Pearson correlation coefficients between the power of the venous and arterial pressure waveforms at each pig's heart rate frequency were calculated for each variation in the anesthetic, as well as before and after hemorrhage. An analysis of variance (ANOVA) test was computed to determine the significance in changes of the venous pressure waveform means caused by each variation. The Pearson correlation coefficients between venous and arterial waveforms decreased as anesthetic dosage increased. In an opposing fashion, the correlation coefficients increased as hemorrhage occurred. Anesthetics and hemorrhage alter venous pressure waveforms in distinctly different ways, making it critical for researchers and clinicians to consider these confounding variables when utilizing pressure waveforms. Further work needs to be done to determine how best to integrate PVP waveforms into clinical decision-making.

Inferior Vena Cava Diameter Measurement Provides Distinct and Complementary Information to Right Atrial Pressure in Acute Decompensated Heart Failure

Inferior vena cava (IVC) measurements correlate only modestly with right atrial pressure (RAP). Part of this inaccuracy is due to the high compliance of the venous system, where a large change in blood volume may result in only a small change in pressure. As such, the information provided by the IVC may be different rather than redundant. We analyzed patients in the ESCAPE (Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness) trial who had both pulmonary artery catheter and IVC measurements at baseline (n = 108). There was only a modest correlation between baseline RAP and IVC diameter (r = 0.41; P < 0.001). Hemoconcentration, defined as an increase in hemoglobin levels between admission and discharge, was correlated with decrease in IVC diameter (r = 0.35; P = 0.02) but not with a decrease in RAP (r = 0.01; P = 0.95). When patients had both IVC and RAP measurements that were below the median, survival rates were superior to the rates of those who had only 1 measurement below the median, and when both rates were above the median, patients fared the worst (P = 0.002). IVC and RAP have limited correlation with each another, and changes in intravascular volume appear to correlate better with IVC diameter rather than with RAP. Furthermore, complementary information is provided by pressure and volume assessments in acute decompensated heart failure.

Changes in inferior vena cava area represent a more sensitive metric than changes in filling pressures during experimental manipulation of intravascular volume and tone.

AimsRemote monitoring of pulmonary artery pressure has reduced heart failure (HF) hospitalizations in chronic HF as elevation of pulmonary artery pressure provides information that can guide treatment. The venous system is characterized by high capacitance, thus substantial increases in intravascular volume can occur before filling pressures increase. The inferior vena cava (IVC) is a highly compliant venous conduit and thus a candidate for early detection of change in intravascular volume. We aimed to compare IVC cross‐sectional area using a novel sensor with cardiac filling pressures during experimental manipulation of volume status, vascular tone, and cardiac function.Methods and resultsExperiments were conducted in sheep to manipulate volume status (colloid infusion), vascular tone (nitroglycerin infusion) and cardiac function (rapid cardiac pacing). A wireless implantable IVC sensor was validated ex‐vivo and in‐vivo, and then used to measure the cross‐sectional area of the IVC. Right‐ and left‐sided cardiac filling pressures were obtained via right heart catheterization. The IVC sensor provided highly accurate and precise measurements of cross‐sectional area in ex‐vivo and in‐vivo validation. IVC area changes were more sensitive than the corresponding changes in cardiac filling pressures during colloid infusion (p < 0.001), vasodilatation (p < 0.001) and cardiac dysfunction induced by rapid pacing (p ≤ 0.02).ConclusionsInferior vena cava area can be remotely and accurately measured in real time with a wireless implantable sensor. Changes in IVC area are more sensitive than corresponding changes in filling pressures following experimental volume loading and fluid redistribution. Additional research is warranted to understand if remote monitoring of the IVC may have advantages over pressure‐based monitors in HF.

Thoracic, Peripheral, and Cerebral Volume, Circulatory and Pressure Responses To PEEP During Simulated Hemorrhage in a Pig Model: a Case Study.

Positive end-expiratory pressure (PEEP) is a respiratory/ventilation procedure that is used to maintain or improve breathing in clinical and experimental cases that exhibit impaired lung function. Body fluid shift movement is not monitored during PEEP application in intensive care units (ICU), which would be interesting specifically in hypotensive patients. Brain injured and hypotensive patients are known to have compromised cerebral blood flow (CBF) autoregulation (AR) but currently, there is no non-invasive way to assess the risk of implementing a hypotensive resuscitation strategy and PEEP use in these patients.The advantage of electrical bioimpedance measurement is that it is noninvasive, continuous, and convenient. Since it has good time resolution, it is ideal for monitoring in intensive care units (ICU). The basis of its future use is to establish physiological correlates. In this study, we demonstrate the use of electrical bioimpedance measurement during bleeding and the use of PEEP in pig measurement.In an anesthetized pig, we performed multimodal recording on the torso and head involving electrical bioimpedance spectroscopy (EIS), fixed frequency impedance plethysmography (IPG), and bipolar (rheoencephalography – REG) measurements and processed data offline. Challenges (n=16) were PEEP, bleeding, change of SAP, and CO2 inhalation. The total measurement time was 4.12 hours.Systemic circulatory results: Bleeding caused a continuous decrease of SAP, cardiac output (CO), and increase of heart rate, temperature, shock index (SI), vegetative - Kerdo index (KI). Pulse pressure (PP) decreased only after second bleeding which coincided with loss of CBF AR. Pulmonary arterial pressure (PAP) increased during PEEP challenges as a function of time and bleeding.EIS/IPG results: Body fluid shift change was characterized by EIS-related variables. Electrical Impedance Spectroscopy was used to quantify the intravascular, interstitial, and intracellular volume changes during the application of PEEP and simulated hemorrhage. The intravascular fluid compartment was the primary source of blood during hemorrhage. PEEP produced a large fluid shift out of the intravascular compartment during the first bleeding period and continued to lose more blood following the second and third bleeding. Fixed frequency IPG was used to quantify the circulatory responses of the calf during PEEP and simulated hemorrhage. PEEP reduced the arterial blood flow into the calf and venous outflow from the calf.Head results: CBF AR was evaluated as a function of SAP change. Before bleeding, and after moderate bleeding, intracranial pressure (ICP), REG, and carotid flow pulse amplitudes (CFa) increased. This change reflected vasodilatation and active CBF AR. After additional hemorrhaging during PEEP, SAP, ICP, REG, CFa signal amplitudes decreased, indicating passive CBF AR. 1) The indicators of active AR status by modalities was the following: REG (n=9, 56 %), CFa (n=7, 44 %), and ICP (n=6, 38 %); 2) CBF reactivity was better for REG than ICP; 3) REG and ICP correlation coefficient were high (R2 = 0.81) during CBF AR active status; 4) PRx and REGx reflected active CBF AR status. CBF AR monitoring with REG offers safety for patients by preventing decreased CBF and secondary brain injury.We used different types of bioimpedance instrumentation to identify physiologic responses in the different parts of the body (that have not been discussed before) and how the peripheral responses ultimately lead to decreased cardiac output and changes in the head. These bioimpedance methods can improve ICU monitoring, increase the adequacy of therapy, and decrease mortality and morbidity.

Anesthesia Management in a Hypertrophic Cardiomyopathy Patient with Brain Tumor: A Case Report

Background: Brain tumour surgeries are high-risk because of their potential for postoperative fetal complications. This risk is exaggerated in the presence of hypertrophic cardiomyopathy (HCM). Hypertrophic cardiomyopathy includes asymmetric left ventricular hypertrophy with mitral valve dysfunction that obstructs the left ventricular outflow tract. Various postoperative factors may accelerate this obstruction and lead to life-threatening consequences. Hypertrophic obstructive cardiomyopathy (HOCM) is a type of HCM that obstructs the left ventricular outflow tract. The most important parameters are preload, afterload, and ventricular contraction, resulting from the surgical method, anesthesia factors, and changes in intravascular volume that are prone to fluctuations in HOCM patients in the postoperative period. These cases increase the risk of arrhythmias and myocardial ischemia and significantly increase patients' morbidity and mortality after surgery. It should avoid lowering blood pressure, increasing heart rate, and reducing preload and afterload in these patients. Cases Report: In this study, we reported a 59 years old man who complained of a speech disorder that had worsened three months ago and mentioned a history of hypertrophic cardiomyopathy. The patient underwent brain tumor surgery and was discharged from the hospital with proper management of anesthesia. Conclusion: Loading and maintaining sinus rhythm are recommended to prevent complications. We presented the intraoperative management of a patient with HCM undergoing a brain tumour resection and discussed its complications.

Can Inferior Vena Cava Diameter and Collapsibility Index Be a Predictor in Detecting Preoperative Intravascular Volume Change in Pediatric Patients?

Abstract Background: Inferior vena cava (IVC) ultrasound measurement is a reliable indicator used in the assessment of intravascular volume status. The aim of this study was to evaluate intravascular volume changes in pediatric patients by measuring the IVC diameter and collapsibility index (CI) in children whose oral feeding was restricted preoperatively. Material and Methods: From May 2018 to October 2018, a total of 55 pediatric patients who were scheduled for surgery were included in this prospective, observational, cohort study. Fasting and satiety IVC diameters and CIs of patients were determined by ultrasonographic evaluation twice: in the preoperative preliminary evaluation, when the patients were satiated, and before surgery, during a fasting period of 6–8 hours. Ultra-sonographic data were recorded and compared between fasting and satiety periods. Results: In the grey scale (B-mode), mean IVC diameter was significantly higher when the patients were satiated, compared to the measurements made just before surgery during the fasting period. In the M-mode, the mean IVC diameter was significantly higher only during the inspiratory phase when the patients were satiated, while during the expiratory phase it was detected to be statistically similar. Mean CI was significantly higher in the immediate preoperative period, compared to the assessment made when satiated. Conclusion: Preoperative ultrasound IVC diameter and CI measurement can be a practical and useful method for evaluating preoperative intravascular volume in children.

Aortic stiffness is sympathetically mediated in fructose‐induced salt‐sensitive hypertension

Introduction Hypertension is one of the leading risk factors for major adverse cardiovascular events (MACE). Likewise, suboptimal dietary habits, including high fructose and sodium intake, are major leading causes of mortality. High dietary fructose alone predisposes to salt-sensitivity of blood pressure, which is an independent, significant cardiovascular risk factor. Aortic stiffness is now recognized as the most robust predictor of MACE and renal failure. Sympathoexcitation also imparts increased cardiovascular risk. Emerging data show that sympathetic inputs strongly impact aortic stiffness, and renal sympathetic denervation improves aortic distensibility. Recently published studies from our laboratory showed that with even short-term fructose in combination with high salt intake renal sympathetic nerve activity (RSNA) is significantly elevated prior to any increase in blood pressure and is responsible for activation of the renin-angiotensin-aldosterone system (RAS). Most recently, we also reported increased aortic stiffness in the fructose-induced salt-sensitive hypertension rat model. The present investigation was designed to assess the impact of acute blockade of RAS and/or sympathetic nervous activity on cardiovascular function in a rat model of fructose- induced salt-sensitive hypertension. Methods Sprague-Dawley rats were placed on a diet containing either 20% fructose or 20% glucose in their drinking water while consuming normal sodium. After one week, the fructose group was switched to a 4% sodium chow (FHS) and the rats were maintained on their respective diets for two additional weeks. At the beginning of week three, arterial and venous catheters were implanted and rats allowed to recover for one day. The following day, aortic pulsed wave velocity was measured using Vevo3100 ultrasound at two time points: 1) at baseline and 2) after intravenous injection of either sympatholytic agent clonidine, RAS inhibitor enalapril or diuretic hydrochlorothiazide (HCTZ). Blood pressure and heart rate were monitored throughout the entire experiment. Results Intravenous administration of clonidine, a central sympatholytic agent, reduced MAP and PWV in FHS rats significantly (by 23 ± 3 mmHg and by 212 ± 39 mm/s, respectively). A similar decline in blood pressure occurred in control rats (27 mmHg) but PWV did not change. The dose of enalapril used to inhibit RAS was chosen to provide a similar decline in MAP as clonidine. The reduction in MAP was slightly less profound (17 ± 4 mmHg); nonetheless, only a minimal change was observed in PWV in FHS (10 ± 6 mm/s) and no change in control rats. The diuretic HCTZ given acutely did not change either MAP or PWV. Conclusion Increase in aortic stiffness after two weeks of fructose and high salt diet appears to be sympathetically driven, since the abrogation of the sympathetic activity with clonidine decreased PWV in FHS rats. The effects of the RAS blockade may require a longer period of treatment to permit vascular remodeling and other cellular mechanisms and, thus, may not have been observable in an acute setting. Likewise, the intravascular volume changes due to the diuretic may also require longer exposure.

A Prospective Observational Study of Plethysmograph Variability Index and Perfusion Index in Predicting Hypotension with Propofol Induction in Noncardiac Surgeries.

Context:Propofol induction is associated with hypotension due to changes in intravascular volume, tone of vessels and cardiac output. Plethysmograph variability index (PVI) and perfusion index (PI) are derived indices from pulse oximeter, used for assessing fluid responsiveness and vessel tone, respectively. We studied the utility of these indices in predicting hypotension due to propofol.Aims:The aim of the study is to test the baseline cutoff values of PVI > 15% and PI <1.05 in predicting hypotension with propofol induction.Settings and Design:This is a prospective double-blind observational study in tertiary care hospital.Methods:Institutional ethical committee approval was obtained. 106 surgical in-patients as per inclusion and exclusion criteria were randomly allotted by computer-generated random numbers. All patients were nil by mouth for 6 h. Injection midazolam and fentanyl were used as premedicants. Propofol at dose of 2 mg.kg−1 was used for induction. Masimo Radical 7® monitor was used for recording of PVI and PI from the upper limb. Baseline values of PVI and PI were recorded every minute from preinduction period till intubation. Standard monitors of noninvasive blood pressure, pulse oximeter, and electrocardiography were used. As per the occurrence of hypotension, patients were grouped as Group H (hypotension) and Group NH (no hypotension).Statistical Analysis:Data were analyzed with SPSS version 20. Quantitative data were analyzed using mean, standard deviation, interquartile range as per distribution. Shapiro–Wilk test with P < 0001 was used descriptive parameters. Scatter plot and Spearman correlation were used to find correlation between the two variables. Mann–Whitney U test was used to compare the two groups in terms of PVI and PI at different time points. Receiver operator characteristic curve was plotted for PI and PVI against hypotension, and cutoff value was calculated. Sensitivity, specificity, positive predictive value, negative value, and diagnostic accuracy of PI and PVI were calculated. P <0.05 was considered statistically significant.Results:Eighty-one patients (76.4%) who had hypotension were grouped into Group H and 25 patients (23.6%) without hypotension as Group NH. There was no difference between groups with respect to doses of midazolam (P = 0.28), fentanyl (P = 0.54), and propofol (P = 0.28). Baseline cutoff of PVI >15 had sensitivity of 58% and specificity of 56%, respectively. PI cutoff value of < 1.05 had sensitivity of 30.9% and specificity of 48%. The risk ratio of PVI cutoff and PI cutoff were 1.41 and 0.43, respectively. There was poor agreement between mean arterial blood pressure (MAP) estimation and prediction of hypotension by PVI (Cohen's kappa = 0.106, P = 0.218) and PI values (Cohen's kappa = −0.133, P = 0.054). Area under the receiver operator curve was 0.596 and 0.511 for PVI >15% and PI < 1.05, respectively. New cutoff values PVI >17.5% and PI > 0.76 were found. PVI and PI had poor diagnostic performance. There was no significant correlation of PVI and PI with hemodynamic variables such as heart rate, MAP, SBP, DBP, and PP.Conclusion:Baseline values of PVI >15% and PI < 1.05 are not good tools for predicting hypotension with propofol induction. New values of baseline cutoff of PVI >17.5% have high specificity, and PI > 0.76 has high sensitivity and positive predictive value.

P15 Effects of Stressed Intravascular Volume on Mean Systemic Filling Pressure and Cardiovascular Compliance in Ovine Postcardiotomy Model

The estimation of the mean systemic filling pressure (MSFP) is used in the intensive care setting as the ultimate guide to volume status. This study assessed the effects of standardised changes in stressed intravascular volume on MSFP, left ventricular volume (LVV), global cardiovascular (GCVC) and left ventricular compliance (LVC).

Why is Diuresis-related Weight Loss Not a Consistent Predictor of Clinical Outcomes in Heart Failure? -need to Account For Variability in Volume Status

Introduction Change in body weight is a common metric used to assess adequacy of decongestive therapy in patients hospitalized for heart failure (HF). However, the findings of clinical studies linking this metric to clinical decongestion and outcomes are mixed. We propose this reflects the failure to take into account biologic variability in intravascular volume status which would impact response to therapy. Methods Data were prospectively collected in hospitalized patients requiring diuresis. Plasma volume (PV) was measured using I-131-labelled albumin indicator-dilution methodology. The cohort was stratified by median diuresis-related weight loss and analyzed for 1-year outcome of HF-related mortality or 1st re-hospitalization, and the relation of change in weight to change in PV admission to discharge. Results The cohort was composed of 138 patients with median weight loss of 6 (IQR -3.2, -8.1) kg during hospitalization (5 IQR 4, 6 days). Greater than median weight loss (Figure 1) did not result in better outcomes. At the time of hospital discharge the subgroup with greater weight loss (N=61) paradoxically demonstrated greater absolute (4.8±1.0 vs. 4.2±1.0 liters, p<0.001) and relative PV expansion(+44±29% vs. +33±23% above normal, p=0.023). Also demonstrated was marked heterogeneity in PV status in both subgroups (Figure 2). Volumes for the cohort ranged from 17% with normal PV, 23% mild-moderate PV expansion, to 60% with persisting severe (≥ +25%) PV expansion at hospital discharge. In a cohort subgroup of 62 patients where PV was measured at hospital admission and discharge there was no clinically significant association between change in weight and change in PV (r=0.327, p=0.01). Conclusions Diuresis-related changes in weight reflect clinical decongestion but do not consistently reflect better HF outcomes and, importantly, do not accurately reflect changes in intravascular volume. A basis for this discordance is the significant patient-to-patient variability in volume both at admission and discharge which confounds interpretation of surrogate metrics of decongestion. Failure to account for the marked heterogeneity in volume status contributes to the observed discordance between metrics of clinical decongestion and HF outcomes. Change in body weight is a common metric used to assess adequacy of decongestive therapy in patients hospitalized for heart failure (HF). However, the findings of clinical studies linking this metric to clinical decongestion and outcomes are mixed. We propose this reflects the failure to take into account biologic variability in intravascular volume status which would impact response to therapy. Data were prospectively collected in hospitalized patients requiring diuresis. Plasma volume (PV) was measured using I-131-labelled albumin indicator-dilution methodology. The cohort was stratified by median diuresis-related weight loss and analyzed for 1-year outcome of HF-related mortality or 1st re-hospitalization, and the relation of change in weight to change in PV admission to discharge. The cohort was composed of 138 patients with median weight loss of 6 (IQR -3.2, -8.1) kg during hospitalization (5 IQR 4, 6 days). Greater than median weight loss (Figure 1) did not result in better outcomes. At the time of hospital discharge the subgroup with greater weight loss (N=61) paradoxically demonstrated greater absolute (4.8±1.0 vs. 4.2±1.0 liters, p<0.001) and relative PV expansion(+44±29% vs. +33±23% above normal, p=0.023). Also demonstrated was marked heterogeneity in PV status in both subgroups (Figure 2). Volumes for the cohort ranged from 17% with normal PV, 23% mild-moderate PV expansion, to 60% with persisting severe (≥ +25%) PV expansion at hospital discharge. In a cohort subgroup of 62 patients where PV was measured at hospital admission and discharge there was no clinically significant association between change in weight and change in PV (r=0.327, p=0.01). Diuresis-related changes in weight reflect clinical decongestion but do not consistently reflect better HF outcomes and, importantly, do not accurately reflect changes in intravascular volume. A basis for this discordance is the significant patient-to-patient variability in volume both at admission and discharge which confounds interpretation of surrogate metrics of decongestion. Failure to account for the marked heterogeneity in volume status contributes to the observed discordance between metrics of clinical decongestion and HF outcomes.