Quantitative fluid overload in severe aortic stenosis refines cardiac damage and associates with worse outcomes

AIMS

Cardiac decompensation in aortic stenosis (AS) involves extra-valvular cardiac damage and progressive fluid overload (FO). FO can be objectively quantified using bioimpedance spectroscopy. We aimed to assess the prognostic value of FO beyond established damage markers to guide risk stratification.

METHODS AND RESULTS

Consecutive patients with severe AS scheduled for transcatheter aortic valve implantation (TAVI) underwent prospective risk assessment with bioimpedance spectroscopy (BIS) and echocardiography. FO by BIS was defined as ≥1.0 L (0.0 L = euvolaemia). The extent of cardiac damage was assessed by echocardiography according to an established staging classification. Right-sided cardiac damage (rCD) was defined as pulmonary vasculature/tricuspid/right ventricular damage. Hospitalization for heart failure (HHF) and/or death served as primary endpoint. In total, 880 patients (81 ± 7 years, 47% female) undergoing TAVI were included and 360 (41%) had FO. Clinical examination in patients with FO was unremarkable for congestion signs in >50%. A quarter had FO but no rCD (FO+/rCD-). FO+/rCD+ had the highest damage markers, including N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels. After 2.4 ± 1.0 years of follow-up, 236 patients (27%) had reached the primary endpoint (29 HHF, 194 deaths, 13 both). Quantitatively, every 1.0 L increase in bioimpedance was associated with a 13% increase in event hazard (adjusted hazard ratio 1.13, 95% confidence interval 1.06-1.22, p < 0.001). FO provided incremental prognostic value to traditional risk markers (NT-proBNP, EuroSCORE II, damage on echocardiography). Stratification according to FO and rCD yielded worse outcomes for FO+/rCD+ and FO+/rCD-, but not FO-/rCD+, compared to FO-/rCD-.

CONCLUSION

Quantitative FO in patients with severe AS improves risk prediction of worse post-interventional outcomes compared to traditional risk assessment.

A Novel Method for Estimating Right Atrial Pressure With Point-of-Care Ultrasound

BACKGROUND

Current noninvasive estimation of right atrial pressure (RAP) by either bedside jugular venous pressure exam or inferior vena cava measurement during a comprehensive echocardiogram offers imprecise estimates of actual RAP.

METHODS

We enrolled 41 patients in a prospective, blinded study to validate a novel point-of-care ultrasound method using direct right atrial depth (RAD) measurement and jugular venous ultrasound to estimate RAP. Two subjects were excluded, and 39 were included in the final analysis. A parasternal long-axis view was obtained, and the depth of the noncoronary cusp attachment to the posterior left ventricular outflow tract was recorded as the RAD. This was added to an estimate of the jugular venous pressure obtained during a jugular vein ultrasound to calculate an estimated RAP (RAP_US). The RAP_US was compared to the RAP measurement during right heart catheterization (RAP_cath) both as measured and as corrected for where the catheter was zeroed.

RESULTS

The correlation coefficient between RAP_cath and RAP_US was +0.75; regression R², 0.56; and bias, -0.49 mm Hg (95% CI, -1.42 to +0.43 mm Hg), with the limits of agreement -5.56 to +7.24 mm Hg and accuracy of 3 mm Hg or less in 29 (74%) of the subjects. For the RAP_US corrected for the catheter zero point, the correlation coefficient between RAP_cath and RAP_US was +0.72; regression R², 0.52; and bias, -0.60 mm Hg (95% CI, -1.60 to +0.39 mm Hg), with the limits of agreement -5.56 to +7.24 mm Hg and accuracy of 3 mm Hg or less in 26 (67%) of the subjects.

CONCLUSION

This simple ultrasound evaluation of RAD and the right jugular vein correlates well with actual RAP and can accurately estimate RAP within 3 mm Hg in most patients. This has the potential to improve our bedside volume status exam, as well as improve the accuracy of RAP estimation during comprehensive echocardiogram.

Utility of fractional excretion of urea nitrogen in heart failure patients with chronic kidney disease

AIMS

Maintenance of euvolaemia with diuretics is critical in heart failure (HF) patients with chronic kidney disease (CKD); however, it is challenging because no reliable marker of volume status exists. Fractional excretion of urea nitrogen (FEUN) is a useful index of volume status in patients with renal failure. We aimed to examine whether FEUN is a surrogate marker of volume status for risk stratification in HF patients with CKD.

METHODS AND RESULTS

We examined 516 HF patients with CKD (defined as discharge estimated glomerular filtration rate < 60 mL/min/1.73 m² ) whose FEUN was measured at discharge (median age, 80 years; 58% male). The patients were divided into four groups according to quartile FEUN value at discharge: low-FEUN, FEUN ≤ 32.1; medium-FEUN, 32.1 < FEUN ≤ 38.0; high-FEUN, 38.0 < FEUN ≤ 43.7; and extremely-high-FEUN, FEUN > 43.7. FEUN was calculated by the following formula: (urinary urea × serum creatinine) × 100/(serum urea × urinary creatinine). During the 3 year follow-up, 131 HF readmissions occurred. Kaplan-Meier analysis showed that the HF readmission rate was significantly lower in the medium-FEUN group than in the other three groups (log-rank test, P = 0.029). Multivariate Cox regression analysis identified the low-FEUN, high-FEUN, and extremely-high-FEUN values as independent factors associated with post-discharge HF readmission. In the analysis of 130 patients who underwent right heart catheterization during hospitalization, a significant correlation between FEUN value and right atrial pressure was observed (R = 0.243, P = 0.005). Multivariate linear regression analysis revealed that FEUN value at discharge decreased in a dose-dependent manner with loop diuretics.

CONCLUSIONS

In HF patients with CKD, FEUN is a potential marker of volume status for risk stratification of post-discharge HF readmission. Low FEUN value (FEUN ≤ 32.1) may represent intravascular dehydration, whereas high FEUN value (FEUN > 38.0) may represent residual congestion; both of them were independent risk factors for HF readmission. FEUN may be useful to determine euvolaemia and guide fluid management in HF patients with CKD.

Assessment of Volume Status in Hospitalized Patients With Chronic Heart Failure

Assessment of volume status in hospitalized patients with heart failure is a critically important diagnostic skill that clinicians utilize frequently. However, accurate assessment is challenging and there is often significant inter-provider disagreement. This review serves as an appraisal of current methods of volume assessment amongst different categories of evaluation including patient history, physical exam, laboratory analysis, imaging, and invasive procedures. Within each category, this review highlights methods that are particularly sensitive or specific, or those that carry impactful positive or negative likelihood ratios. Utilization of the information that this review provides will allow clinicians to determine volume status of hospitalized heart failure patients more accurately and more precisely in order to provide appropriate and effective therapies.

Evaluation of lung ultrasound to detect volume overload in children undergoing dialysis

BACKGROUND

Lung ultrasound is a well-established technique to assess extravascular lung water, a proxy for volume status, in the adult population. Despite its utility, the data are limited supporting the use of ultrasound to evaluate fluid volume status among pediatric patients. Our study uses a simplified ultrasound protocol to evaluate changes in extravascular lung water, represented by b-lines, among pediatric patients undergoing hemodialysis.

METHODS

This prospective single-center study included children from birth to 18 years of age. The number of b-lines per ml/kg of fluid removed was compared prior to, at the midpoint, and following termination of dialysis. An 8-zone protocol was utilized, and b-lines were correlated to hemoconcentration measured by the CRIT-LINE® hematocrit.

RESULTS

Six patients with a total of 26 hemodialysis sessions were included in this study. The b-line measurements post-dialysis were 2.27 (p < 0.001; 94%CI -3.31, -1.22) lower relative to pre-dialysis. The number of b-lines was reduced by 1.69 (p < 0.001; -2.58, -0.80) between pre-dialysis and at the midpoint of dialysis and by 0.58 (p = 0.001; -0.90, -0.24) between the midpoint of dialysis and post-dialysis. A 1 mL/kg fluid loss correlated to a decrease in the original b-lines by 0.079. An inverse relationship (r = -0.54; 95% CI: -0.72, -0.34; p < 0.001) was noted between the b-lines and the patients' hematocrit levels.

CONCLUSIONS

A simplified 8-zone ultrasound protocol can assess fluid volume change in real time and correlates with hematocrit levels obtained throughout dialysis. This provides a valuable method for monitoring fluid status in volume overloaded patient populations. A higher resolution version of the Graphical abstract is available as Supplementary information.

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.

Accurate Estimation of Right-Filling Pressure Using Handheld Ultrasound Score in Patients with Heart Failure

INTRODUCTION

This study aims to evaluate the accuracy of bedside assessment of inferior vena cava (IVC) and right internal jugular (RIJ) vein in predicting right atrial (RA) pressure in heart failure patients.

METHODS

We prospectively studied 124 heart failure patients who were referred to our catheterization laboratory for right heart catheterizations to assess hemodynamics and to guide heart failure management. Just prior to the procedure, a handheld ultrasound examination was performed in each patient. The volume status was assessed by estimating RA pressure using end-expiratory IVC dimension, IVC respiratory collapsibility, and RIJ respiratory collapsibility. Patients were divided into 2 groups based on invasive RA pressure value. Multiple logistic regression models were used to identify factors associated with RA ≥10 mm Hg; a 3-point simple score was then created. The performance of this score was assessed using the receiver operating characteristics curve.

RESULTS

In this study 124 heart failure patients were included; median age was 59 years (interquartile range 48-65), and 40% were female. RIJ respiratory collapsibility <50%, end-expiratory IVC dimension ≥21 mm, and respiratory collapsibility <50% were significantly associated with elevated RA pressure, and were used to build the score. The area under the receiver operating characteristics curve (AUC) for the 3-point score was 0.84 (0.77-0.92), and it performed better than 2-point score using IVC characteristics alone (AUC 0.84 [0.77-0.92] vs 0.75 [0.67-0.83]; P = .003). Of 124 patients, 90 patients (72.5%) had concordant RA pressure and pulmonary capillary wedge pressure.

CONCLUSION

Concomitant ultrasound assessment of RIJ and IVC correlated better with RA pressure than IVC alone. A simple 3-point score can provide a useful and easily accessible tool to estimate volume status, and further guide management of heart failure patients.

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.

TFAST Accurate Diagnosis of Pleural and Pericardial Effusion, Caudal Vena Cava in Dogs and Cats

TFAST, a standardized and validated thoracic point-of-care ultrasound examination, includes 5 acoustic windows: bilaterally applied chest tube site and pericardial site views plus diaphragmatico-hepatic view, also part of AFAST/ Vet BLUE. TFAST is used for rapid detection of pneumothorax and pleural and pericardial effusion. By following a set of TFAST rules, image interpretation errors are avoided, including mistaking cardiac chambers for effusion. Moreover, TFAST echocardiography is used as a screening test for chamber size and soft tissue abnormalities, volume status and contractility, and intracardiac abnormalities.

AFAST Target-Organ Approach and Fluid Scoring System in Dogs and Cats

Point-of-care ultrasonography as part of the physical examination is becoming considered a core skill. AFAST includes 5 acoustic windows over the abdomen and serves as a rapid screening test for free fluid (ascites, retroperitoneal, pleural and pericardial effusion) and soft tissue abnormalities (target-organ approach), and has an abdominal fluid scoring system (semiquantitating volume). Moreover, add-on skills are possible without additional views that include characterizing the caudal vena cava and hepatic veins (volume status), measuring the urinary bladder (volume estimation and urine output), screening for free air (pneumoperitoneum, pneumoretroperitoneum), and assessing gastrointestinal motility.

Point-of-care ultrasound to assess volume status and pulmonary oedema in malaria patients

PURPOSE

Fluid management is challenging in malaria patients given the risks associated with intravascular fluid depletion and iatrogenic fluid overload leading to pulmonary oedema. Given the limitations of the physical examination in guiding fluid therapy, we evaluated point-of-care ultrasound (POCUS) of the inferior vena cava (IVC) and lungs as a novel tool to assess volume status and detect early oedema in malaria patients.

METHODS

To assess the correlation between IVC and lung ultrasound (LUS) indices and clinical signs of hypovolaemia and pulmonary oedema, respectively, concurrent clinical and sonographic examinations were performed in an observational study of 48 malaria patients and 62 healthy participants across age groups in Gabon.

RESULTS

IVC collapsibility index (CI) ≥ 50% on enrolment reflecting intravascular fluid depletion was associated with an increased number of clinical signs of hypovolaemia in severe and uncomplicated malaria. With exception of dry mucous membranes, IVC-CI correlated with most clinical signs of hypovolaemia, most notably sunken eyes (r = 0.35, p = 0.0001) and prolonged capillary refill (r = 0.35, p = 0.001). IVC-to-aorta ratio ≤ 0.8 was not associated with any clinical signs of hypovolaemia on enrolment. Among malaria patients, a B-pattern on enrolment reflecting interstitial fluid was associated with dyspnoea (p = 0.0003), crepitations and SpO₂ ≤ 94% (both p < 0.0001), but not tachypnoea (p = 0.069). Severe malaria patients had increased IVC-CI (p < 0.0001) and more B-patterns (p = 0.004) on enrolment relative to uncomplicated malaria and controls.

CONCLUSION

In malaria patients, POCUS of the IVC and lungs may improve the assessment of volume status and detect early oedema, which could help to manage fluids in these patients.

Lung Ultrasound: A "Biomarker" for Fluid Overload?

Fluid overload is associated with poor outcomes in patients with acute kidney injury as well as end-stage kidney disease. Lung ultrasound (LUS) has been used in many different settings and specialties including the emergency department, intensive care unit, trauma, cardiology, and nephrology. Although LUS has been a valuable tool in assessing pulmonary congestion, LUS findings may not always be pathognomonic for pulmonary congestion. Furthermore, the feasibility of doing an extensive LUS examination as has been done in research studies may be hard to implement within the clinical setting. This review will go over the use of LUS to evaluate for fluid overload, compare LUS with other markers of fluid overload, review limitations of LUS, and suggest potential future directions in the use of LUS in nephrology.

Preload dependence of pulmonary haemodynamics and right ventricular performance

AIMS

Systolic pulmonary artery pressure (SPAP) and right heart adaptation in relation to pre-existing preload are often disregarded. To determine volume-related changes in the pulmonary-right ventricle (RV) unit and the preload dependence of its components, we analysed pulmonary haemodynamics and right ventricular performance, taking advantage of the plasma volume removal associated to haemodialysis (HD).

METHODS AND RESULTS

Fifty-three stable patients on chronic HD with LVEF > 50% and without heart failure were recruited (mean age 63.0 ± 12.4 years; 31.2% women; hypertension in 89% and diabetes in 53%) and evaluated just before and after HD (mean ultrafiltration volume 2.4 ± 0.7 l). SPAP from both times were available in 39 patients. After HD, SPAP decreased (42.2 ± 12.6 to 33.7 ± 11.6 mmHg, p < 0.001) without modification of non-invasive pulmonary vascular resistance (1.75 ± 0.44 to 1.75 ± 0.40 eWU, p = 0.94). Age and drop in the E/e' ratio were the variables associated with greater reduction in PASP (p = 0.022 and p = 0.049, respectively). A significant reduction of right chamber sizes was observed, along with a diminution in measures of RV contractility, excluding RV longitudinal strain. Functional tricuspid regurgitation (FTR) diminution was observed in 26% of patients, occurring in every case with more than mild FTR. On multivariate analyses, left atrial size was the only predictor of pulmonary hypertension (defined as SPAP > 40 mmHg) (OR 1.29 (1.07-1.56), p = 0.006).

CONCLUSION

Rapid volemic changes may affect FTR grading, RV size and contractility, with RV longitudinal strain being less variable than conventional parameters. SPAP decreases after HD, and this reduction is related to age and greater diminution of the E/e' ratio.

Fluid overload in patients undergoing TAVR: what we can learn from the nephrologists

Aims

Fluid overload (FO) puts aortic stenosis (AS) patients at risk for heart failure (HF) and death. However, conventional FO assessment, including rapid weight gain, peripheral oedema, or chest radiography, is inaccurate. Bioelectrical impedance spectroscopy (BIS) allows objective and reproducible FO quantification, particularly if clinically unapparent. It is used in dialysis patients to establish dry weight goals. BIS has not been tested for prognostication in AS. This study aimed to evaluate whether BIS adds prognostic information in stable patients undergoing transcatheter aortic valve replacement (TAVR).

Methods and results

Consecutive patients scheduled for TAVR underwent BIS in addition to echocardiographic, clinical, and laboratory assessment. On BIS, mild FO was defined as >1.0 L and severe as >3.0 L. Combined HF hospitalization and/or all‐cause death was defined as primary endpoint. Three hundred forty‐four patients (81.5 ± 7.2 years old, 47.4% female) were prospectively included. FO by BIS was associated with clinical congestion signs, higher serum markers of cardiac injury, poorer left ventricular function, higher pulmonary pressures, and more severe tricuspid regurgitation (all P < 0.05). Yet, clinical examination was unremarkable in >30% in mild FO, only detected by BIS. During 12.1 ± 5.5 months, 67 (19.5%) events were recorded (40 deaths, 15 HF hospitalizations, and 12 both). Quantitatively, every 1 L increase in FO was associated with a 24% (HR 1.24, 95% CI 1.13–1.35, P < 0.001) increase in event hazard. This association persisted after adjustment for STS/EuroSCORE‐II, NT‐proBNP, left ventricular ejection fraction, and renal function.

Conclusions

In patients undergoing TAVR, FO by BIS is strongly associated with adverse outcomes. BIS measurement conveys prognostic information not represented in any currently used AS/TAVR risk assessments.

Plethysmography variability index (PVI) changes in preterm neonates with shock-an observational study

Shock is an acute state of circulatory dysfunction. The diagnosis of shock is complex in neonates. The relative sensitivity of current clinical or laboratory findings for detecting shock is largely unknown, especially for preterm neonates. For preload assessment, inferior vena cava (IVC) collapsibility can be a useful bedside echocardiography parameter. plethysmography variability index (PVI) is a marker of fluid responsive shock in adults and children, but not well defined in neonates. In this prospective observational study, we evaluated the changes in PVI in preterm neonates with shock. Among the 37 infants enrolled in the study, the mean blood pressure (MAP) was 45 (± 4 mm of Hg) and none of infants had hypotension. The mean pulse pressure was 28 mm of Hg, the mean PVI was 28% (±5), the mean arterial blood gas pH was 7.20 (±0.07), and the mean base deficit was 9.9 (±2.53) at the onset of shock. Thirty (96.77%) of the 31 infants with resolution of shock showed decrease in PVI with an average decrease of 11% (±5).Conclusion: Significant proportion of neonates show an increase in PVI at the onset of shock. What is Known: • Plethysmography Variability Index (PVI) is commonly used as a marker of volume status in paediatric population. • Changes in PVI may guide in giving volume boluses in patients with shock. What is New: • This study provides information of changes in PVI in preterm neonates with shock. • PVI may become a valuable tool to be used at bedside in preterm infants with shock.

Central venous pressure, global end-diastolic index, and the inferior vena cava collapsibility/distensibility indices to estimate intravascular volume status in critically ill children: A pilot study

BACKGROUND

The assessment of the volume status in critically ill paediatric patients in intensive care units is vitally important for fluid therapy management. The most commonly used parameter for detecting volume status is still central venous pressure (CVP); however, in recent years, various kinds of methods and devices are being used for volume assessment in intensive care units.

OBJECTIVES

We aimed to evaluate the relationship between CVP, the global end-diastolic index (GEDI), and ultrasound measurements of the collapsibility and distensibility indices of the inferior vena cava (IVC) in paediatric patients undergoing Pulse index Contour Cardiac Output (PiCCO) monitoring.

METHODS

Fifteen patients receiving PiCCO monitoring were prospectively included in the study. Forty-nine PiCCO measurements were evaluated, and simultaneous CVP values were noted. After each measurement, IVC collapsibility (in spontaneously breathing patients) and distensibility (in mechanically ventilated patients) indices were measured with bedside ultrasound.

RESULTS

The mean age was 93.2 ± 61.3 months. Significant and negative correlations of the GEDI were found with the IVC collapsibility index (in spontaneously breathing patients) and the IVC distensibility index (in mechanically ventilated patients) (r = -0.502, p < 0.001; r = -0.522, p = 0.001, respectively). A significant and weakly positive correlation was found between the GEDI and CVP (r = 0.346, p = 0.015), and a significant and negative correlation was found between the IVC collapsibility index and CVP (r = -0.482, p = 0.03). The correlation between the IVC distensibility index and CVP was significant and negative (r = -0.412, p = 0.04).

CONCLUSION

The use of PiCCO as an advanced haemodynamic monitoring method and the use of bedside ultrasound as a noninvasive method are useful to evaluate the volume status in critically ill paediatric patients in intensive care. These methods will gradually come to the fore in paediatric intensive care.

Carotid Artery Flow Time Measured by Point-of-Care Ultrasound Correlates with Volume Changes in Pediatric Hemodialysis Patients

Carotid artery flow time corrected for heart rate (CFTc) correlates with intravascular volume changes in adults but has not been studied adequately in the pediatric population. We studied how fluid status changes correlate with CFTc in pediatric patients undergoing hemodialysis. This prospective observational study involved pediatric patients aged 5-18 y undergoing chronic hemodialysis at a tertiary care children's hospital in the United States. We measured CFTc by point-of-care ultrasound before and after each hemodialysis session, including passive leg raise. One hundred sixty-eight CFTc measurements were obtained from a total of 21 patient encounters. Post-dialysis CFTc decreased by 21.7 ms (95% confidence interval: 12.3-31.0) (p < 0.001). Pre- and post-dialysis ∆CFTc measurements were proportionally correlated with volume removed in dialysis adjusted for weight (mL/kg) (R² = 0.224, p = 0.03). There was no significant change in mean CFTc with passive leg raise before or after hemodialysis. In children on hemodialysis, changes in CFTc were moderately correlated with decrease in intravascular volume after hemodialysis.

The Nephrologist as an Ultrasonographer

Ultrasonography is increasingly being used in the practice of nephrology, whether it is for diagnosis or management of acute or chronic kidney dysfunction, until progression to end-stage kidney disease, including preoperative assessment, access placement, and diagnosis and management of dysfunctional hemodialysis access. Point-of-care ultrasounds are also being used by nephrologists to help manage volume status, especially in patients admitted to the intensive care units, and more recently, for guiding fluid removal in the outpatient dialysis units. Fundamental knowledge of sonography has become invaluable to the nephrologist, and performance and interpretation of ultrasound has now become an essential tool for practicing nephrologists to provide patient-centered care, maximize efficiency, and minimize fragmentation of care. This review will address the growing role of ultrasonography in the management of a patient with CKD from the point of initial contact with the nephrologist throughout the spectrum of kidney disease and its consequences.

Improved Repeatability of the Estimation of Pulsatility of Inferior Vena Cava

The inferior vena cava (IVC) shows variations of cross section over time (pulsatility) induced by different stimulations (e.g., breathing and heartbeats). Pulsatility is affected by patients' volume status and can be investigated by ultrasound (US) measurements. An index of IVC pulsatility based on US visualization and called caval index (CI) was proposed as a non-invasive indirect measurement of the volume status. However, its estimation is not standardized, operator dependent and affected by movements of the vein and non-uniform pulsatility. We introduced a software that processes B-mode US video clips to track IVC movements and estimate CI on an entire portion of the vein. This method is here compared to the standard approach in terms of repeatability of the estimated CI, reporting on the variability over different respiratory cycles, longitudinal IVC sections and intra-/inter-observers. Our method allows to reduce the variability of CI assessment, making a step toward its standardization.

Point-of-Care Echocardiography Unveils Misclassification of Acute Kidney Injury as Hepatorenal Syndrome

INTRODUCTION

Fulfillment of the diagnostic criteria for -hepatorenal syndrome type 1 (HRS-1) requires prior failure of 2 days of intravenous volume expansion and/or diuretic withdrawal. However, no parameter of volume status is used to guide the need for volume expansion in patients with suspected HRS-1. We hypothesized that point-of-care echocardiography (POCE) may better characterize the volume status in patients with acute kidney injury (AKI) and cirrhosis to ascertain or disprove the diagnosis of HRS-1.

METHODS

A pilot observational study was conducted to determine the clinical utility of POCE-based examination of inferior vena cava diameter (IVCD) and collapsibility index (IVCCI) to assess intravascular volume status in patients with cirrhosis and AKI who had been deemed adequately volume-repleted and thereby assigned a clinical diagnosis of HRS-1. Early improvement in kidney function was defined as ≥20% decrease in serum creatinine (sCr) at 48-72 h.

RESULTS

A total of 53 patients were included. The mean sCr at the time of volume assessment was 3.2 ± 1.5 mg/dL, and the mean Model for End-Stage Liver Disease score was 29 ± 8. Fifteen (23%) patients had an IVCD <1.3 cm and IVCCI >40% and were reclassified as fluid-depleted, 11 (21%) had an IVCD >2 cm and IVCCI <40% and were reclassified as fluid-expanded, and 8 (15%) had and IVCD <1.3 cm and IVCCI <40% and were reclassified as having intra-abdominal hypertension (IAH). Twelve (23%) patients exhibited early improvement in kidney function following a POCE-guided therapeutic maneuver, that is, volume expansion, diuresis, or paracentesis for those deemed fluid-depleted, fluid-expanded or having IAH, respectively.

CONCLUSION

POCE-based assessment of volume status in cirrhotic individuals with AKI reveals marked heterogeneity. Unguided volume expansion in these patients may lead to premature or delayed diagnosis of HRS-1.

One approach to circulation and blood flow in the critical care unit

Evaluating and managing circulatory failure is one of the most challenging tasks for medical practitioners involved in critical care medicine. Understanding the applicability of some of the basic but, at the same time, complex physiological processes occurring during a state of illness is sometimes neglected and/or presented to the practitioners as point-of-care protocols to follow. Furthermore, managing hemodynamic shock has shown us that the human body is designed to fight to sustain life and that the compensatory mechanisms within organ systems are extraordinary. In this review article, we have created a minimalistic guide to the clinical information relevant when assessing critically ill patients with failing circulation. Measures such as organ blood flow, circulating volume, and hemodynamic biomarkers of shock are described. In addition, we will describe historical scientific events that led to some of our current medical practices and its validation for clinical decision making, and we present clinical advice for patient care and medical training.

Blood volume analysis as a guide for dry weight determination in chronic hemodialysis patients: a crossover study

BACKGROUND

Volume overload and depletion both lead to high morbidity and mortality. Achieving euvolemia is a challenge in patients with end stage kidney disease on hemodialysis (HD). Blood volume analysis (BVA) uses radiolabeled albumin to determine intravascular blood volume (BV). The measured BV is compared to an ideal BV (validated in healthy controls). We hypothesized that BVA could be used in HD to evaluate the adequacy of the current clinically prescribed "estimated dry weight" (EDW) and to titrate EDW in order to improve overall volume status. We were also interested in the reproducibility of BVA results in end stage kidney disease.

METHODS

Twelve adults on chronic HD were recruited; 10 completed the study. BVA (Daxor, New York, NY, USA) was used to measure BV at baseline. EDW was kept the same if the patient was deemed to be euvolemic by BVA otherwise, the prescribed EDW was changed with the aim that measured BV would match ideal BV. A second BVA measurement was done 1-3 months later in order to measure BV again.

RESULTS

Based on BVA, 6/10 patients were euvolemic at baseline and 5/10 were euvolemic at the second measurement. When comparing patients who had their prescribed EDW changed after the initial BVA to those who did not, both groups had similar differences between measured and ideal BV (P = 0.75). BV values were unchanged at the second measurement (P = 0.34) and there was no linear correlation between BV change and weight change (r² = 0.08).

CONCLUSIONS

This pilot study is the first longitudinal measurement of BVA in HD patients. It revealed that changing weight did not proportionally change intravascular BV. BV remained stable for 1-3 months. BVA may not be helpful in clinically stable HD patients but studies on patients with hemodynamic instability and uncertain volume status are needed.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02717533), first registered February 4, 2015.

[Point-of-care ultrasonography of the abdomen in emergency and intensive care medicine]

Point-of-care ultrasound is a fundamental part of diagnostic and therapeutic management in emergency and intensive care medicine. The availability of high-resolution mobile ultrasound systems allows high-quality imaging at the bedside of the patient. Point-of-care ultrasound is not a comprehensive differential diagnostic abdominal ultrasound examination. Rather, the aim of the method is to integrate easily detectable sonographic findings into the clinical context. From this, the necessary diagnostic or therapeutic procedures are derived. This article shows opportunities and limitations of this method. The structure of the article is given by the leading clinical symptoms. The focus is on the ultrasound examination and the characteristic sonographic findings with illustrative ultrasound images. This is followed by a short differential diagnostic interpretation. Further diagnostic or therapeutic management is also briefly addressed.

Is there an association between central venous pressure measurement and ultrasound assessment of the inferior vena cava?

INTRODUCTION

Early assessment of volume status is paramount in critically ill patients. Central venous pressure (CVP) measurement and ultrasound assessment of the inferior vena cava (IVC) are both used for volume assessment in the emergency centre. Recent data is conflicting over whether there is a correlation between CVP and ultrasound assessment of the IVC.

METHODS

This was a retrospective review of an audit previously performed in the Emergency Unit of Ngwelezane Hospital in Kwazulu-Natal. The audit involved measuring inferior vena cava collapsibility index (IVC-CI) within 5 min of CVP measurement. In this retrospective study, audit data were analysed to determine if an association exists.

RESULTS

Twenty-four patients were included. The median age of participants was 36 (IQR 42) years (95% CI 33-56). The median time to ultrasound was 18.6 (52.5) h (95% CI 7.5-36.2). The mean CVP was 13.7 ± 7.7 cm H₂O and mean IVC-CI was 39.4 ± 17.8%. Based on a Pearson correlation test, there was a weak negative correlation between CVP and IVC-CI, which was not statistically significant (r = -0.05, n = 24, p = 0.81, 95% CI -0.5 to 0.4) for all participants. However, among females there was a moderate negative correlation between CVP and IVC-CI, which was not statistically significant (r = -0.43, n = 7, p = 0.34, 95% CI -0.9 to 0.5), while among males there was a weak positive correlation, which was not statistically significant (r = 0.16, n = 17, p = 0.53, 95% CI -0.3 to 0.6).

DISCUSSION

There is no significant correlation between CVP and IVC-CI. Further validation research is required to support our preliminary findings of no significant correlation between CVP measurement and ultrasound assessment of the IVC. CVP and IVC ultrasound should be used as clinical adjuncts, and not as stand-alone measures of volume assessment.

Estimation and tracking of AP-diameter of the inferior vena cava in ultrasound images using a novel active circle algorithm

Medical research suggests that the anterior-posterior (AP)-diameter of the inferior vena cava (IVC) and its associated temporal variation as imaged by bedside ultrasound is useful in guiding fluid resuscitation of the critically-ill patient. Unfortunately, indistinct edges and gaps in vessel walls are frequently present which impede accurate estimation of the IVC AP-diameter for both human operators and segmentation algorithms. The majority of research involving use of the IVC to guide fluid resuscitation involves manual measurement of the maximum and minimum AP-diameter as it varies over time. This effort proposes using a time-varying circle fitted inside the typically ellipsoid IVC as an efficient, consistent and novel approach to tracking and approximating the AP-diameter even in the context of poor image quality. In this active-circle algorithm, a novel evolution functional is proposed and shown to be a useful tool for ultrasound image processing. The proposed algorithm is compared with an expert manual measurement, and state-of-the-art relevant algorithms. It is shown that the algorithm outperforms other techniques and performs very close to manual measurement.

Finger and forehead photoplethysmography-derived pulse-pressure variation and the benefits of baseline correction

To non-invasively predict fluid responsiveness, respiration-induced pulse amplitude variation (PAV) in the photoplethysmographic (PPG) signal has been proposed as an alternative to pulse pressure variation (PPV) in the arterial blood pressure (ABP) signal. However, it is still unclear how the performance of the PPG-derived PAV is site-dependent during surgery. The aim of this study is to compare finger- and forehead-PPG derived PAV in their ability to approach the value and trend of ABP-derived PPV. Furthermore, this study investigates four potential confounding factors, (1) baseline variation, (2) PPV, (3) ratio of respiration and heart rate, and (4) perfusion index, which might affect the agreement between PPV and PAV. In this work, ABP, finger PPG, and forehead PPG were continuously recorded in 29 patients undergoing major surgery in the operating room. A total of 91.2 h data were used for analysis, from which PAV and PPV were calculated and compared. We analyzed the impact of the four factors using a multiple linear regression (MLR) analysis. The results show that compared with the ABP-derived PPV, finger-derived PAV had an agreement of 3.2 ± 5.1%, whereas forehead-PAV had an agreement of 12.0 ± 9.1%. From the MLR analysis, we found that baseline variation was a factor significantly affecting the agreement between PPV and PAV. After correcting for respiration-induced baseline variation, the agreements for finger- and forehead-derived PAV were improved to reach an agreement of − 1.2 ± 3.8% and 3.3 ± 4.8%, respectively. To conclude, finger-derived PAV showed better agreement with ABP-derived PPV compared to forehead-derived PAV. Baseline variation was a factor that significantly affected the agreement between PPV and PAV. By correcting for the baseline variation, improved agreements were obtained for both the finger and forehead, and the difference between these two agreements was diminished. The tracking abilities for both finger- and forehead-derived PAV still warrant improvement for wide use in clinical practice. Overall, our results show that baseline-corrected finger- and forehead-derived PAV may provide a non-invasive alternative for PPV.

Assessment of Volume Status Using Ultrasonography

Ultrasonography is a first-line diagnostic tool when evaluating volume status in the critical care patient population. Ultrasonography leads to a prompt diagnosis and more appropriate management plan, while decreasing health care costs, time to diagnosis, hospital length of stay, time to definitive operation, and mortality. It is recommended that critical care providers treating critically ill patients be skilled and competent in critical care ultrasonography. As the critical care population and the shortage of critical care physicians increases, advanced practice providers are becoming more prevalent in critical care areas and should be competent in this skill as well.

Practical Assessment of Volume Status in Daily Practice

Fluid therapy is considered the cornerstone of treatment for patients suffering from various medical ailments particularly in emergency and critical care situations where hypovolemia commonly occurs. The ability to accurately assess a patient's volume status is critical to the decision making process when synthesizing and implementing a fluid therapy plan. Both extremes, over supplementation or not supplementing enough fluid can be detrimental to the patient. Precisely assessing a patient's blood volume without access to advanced often complicated equipment and monitoring devices is challenging. The aim of this paper is to review the practical means and tools available to aide in estimating a patient's volume status.

The standard deviation of extracellular water/intracellular water is associated with all-cause mortality and technique failure in peritoneal dialysis patients

PURPOSE

The mortality rate of peritoneal dialysis (PD) patients is still high, and the predicting factors for PD patient mortality remain to be determined. This study aimed to explore the relationship between the standard deviation (SD) of extracellular water/intracellular water (E/I) and all-cause mortality and technique failure in continuous ambulatory PD (CAPD) patients.

METHODS

All 152 patients came from the PD Center between January 1st 2006 and December 31st 2007. Clinical data and at least five-visit E/I ratio defined by bioelectrical impedance analysis were collected. The patients were followed up till December 31st 2010. The primary outcomes were death from any cause and technique failure. Kaplan-Meier analysis and Cox proportional hazards models were used to identify risk factors for mortality and technique failure in CAPD patients.

RESULTS

All patients were followed up for 59.6 ± 23.0 months. The patients were divided into two groups according to their SD of E/I values: lower SD of E/I group (≤0.126) and higher SD of E/I group (>0.126). The patients with higher SD of E/I showed a higher all-cause mortality (log-rank χ (2) = 10.719, P = 0.001) and technique failure (log-rank χ (2) = 9.724, P = 0.002) than those with lower SD of E/I. Cox regression analysis found that SD of E/I independently predicted all-cause mortality (HR  3.551, 95 % CI 1.442-8.746, P = 0.006) and technique failure (HR  2.487, 95 % CI 1.093-5.659, P = 0.030) in CAPD patients after adjustment for confounders except when sensitive C-reactive protein was added into the model.

CONCLUSION

The SD of E/I was a strong independent predictor of all-cause mortality and technique failure in CAPD patients.

[Hemodynamic monitoring in intensive care and emergency medicine : Integration of clinical signs and ultrasound findings]

Hemodynamic monitoring is required in critically ill patients presenting with circulatory shock. Besides the clinical evaluation, noninvasive technologies can be used. Guidelines on volume resuscitation and cardiogenic shock already recommend bedside ultrasound as a diagnostic tool. To differentiate the cause of circulatory shock and monitor the effects of therapies, hemodynamic monitoring is necessary. This review discusses possibilities of the different invasive and noninvasive monitoring tools with a focus on the integration of clinical and sonographic parameters.

Fluid management of the neurological patient: a concise review

Maintenance fluids in critically ill brain-injured patients are part of routine critical care. Both the amounts of fluid volumes infused and the type and tonicity of maintenance fluids are relevant in understanding the impact of fluids on the pathophysiology of secondary brain injuries in these patients. In this narrative review, current evidence on routine fluid management of critically ill brain-injured patients and use of haemodynamic monitoring is summarized. Pertinent guidelines and consensus statements on fluid management for brain-injured patients are highlighted. In general, existing guidelines indicate that fluid management in these neurocritical care patients should be targeted at euvolemia using isotonic fluids. A critical appraisal is made of the available literature regarding the appropriate amount of fluids, haemodynamic monitoring and which types of fluids should be administered or avoided and a practical approach to fluid management is elaborated. Although hypovolemia is bound to contribute to secondary brain injury, some more recent data have emerged indicating the potential risks of fluid overload. However, it is acknowledged that many factors govern the relationship between fluid management and cerebral blood flow and oxygenation and more research seems warranted to optimise fluid management and improve outcomes.

Current status of ultrasound-guided surgery in the treatment of breast cancer

The primary goal of breast-conserving surgery (BCS) is to obtain tumour-free resection margins. Margins positive or focally positive for tumour cells are associated with a high risk of local recurrence, and in the case of tumour-positive margins, re-excision or even mastectomy are sometimes needed to achieve definite clear margins. Unfortunately, tumour-involved margins and re-excisions after lumpectomy are still reported in up to 40% of patients and additionally, unnecessary large excision volumes are described. A secondary goal of BCS is the cosmetic outcome and one of the main determinants of worse cosmetic outcome is a large excision volume. Up to 30% of unsatisfied cosmetic outcome is reported. Therefore, the search for better surgical techniques to improve margin status, excision volume and consequently, cosmetic outcome has continued. Nowadays, the most commonly used localization methods for BCS of non-palpable breast cancers are wire-guided localization (WGL) and radio-guided localization (RGL). WGL and RGL are invasive procedures that need to be performed pre-operatively with technical and scheduling difficulties. For palpable breast cancer, tumour excision is usually guided by tactile skills of the surgeon performing “blind” surgery. One of the surgical techniques pursuing the aims of radicality and small excision volumes includes intra-operative ultrasound (IOUS). The best evidence available demonstrates benefits of IOUS with a significantly high proportion of negative margins compared with other localization techniques in palpable and non-palpable breast cancer. Additionally, IOUS is non-invasive, easy to learn and can centralize the tumour in the excised specimen with low amount of healthy breast tissue being excised. This could lead to better cosmetic results of BCS. Despite the advantages of IOUS, only a small amount of surgeons are performing this technique. This review aims to highlight the position of ultrasound-guided surgery for malignant breast tumours in the search for better oncological and cosmetic outcomes.

Surgeon-performed bedside ultrasound to assess volume status: a feasibility study

PURPOSE

Rapid assessment of volume status in children is often difficult. The purpose of this study was to evaluate the feasibility of surgeon-performed ultrasound to assess volume status in patients with hypertrophic pyloric stenosis.

METHODS

Ultrasounds were performed on admission and before operation. The diameters of the inferior vena cava (IVC) and aorta (Ao) were measured and IVC/Ao ratios were calculated. Electrolytes were measured on admission and repeated if warranted. Logistic regression was used to associate the clinical outcome, defined as CO2 ≤30 mEq/L, with IVC/Ao ratios. Predictive capacity was estimated from the logistic regression for IVC/Ao ratios. Linear regression was used to estimate associations between CO2 values and IVC/Ao ratios.

RESULTS

Thirty-one patients were enrolled. The IVC/Ao ratio is highly associated with actual CO2 values (P < 0.001) and the clinical outcome (P = 0.004). For every 0.05 unit increase in IVC/Ao ratio, predicted CO2 decreased 1.1 units. For every 0.05 unit increase in the IVC/Ao ratio, the odds of having a CO2 ≤30 mEq/L increased 48% [OR = 1.48, 95% CI (1.13,1.94)]. Predictive capacity is maximized at an IVC/Ao ratio of 0.75 as 83.9 % of subjects were correctly classified and specificity and PPV = 100%.

CONCLUSIONS

Surgeon-performed ultrasound to determine IVC/Ao ratio is feasible. An IVC/Ao ratio of 0.75 predicted adequate resuscitation.

Alternative methods to central venous pressure for assessing volume status in critically ill patients

INTRODUCTION

Early goal-directed therapy increases survival in persons with sepsis but requires placement of a central line. We evaluate alternative methods to measuring central venous pressure (CVP) to assess volume status, including peripheral venous pressure (PVP) and stroke volume variation (SVV), which may facilitate nurse-driven resuscitation protocols.

METHODS

Patients were enrolled in the emergency department or ICU of an academic medical center. Measurements of CVP, PVP, SVV, shoulder and elbow position, and dichotomous variables Awake, Movement, and Vented were measured and recorded 7 times during a 1-hour period. Regression analysis was used to predict CVP from PVP and/or SVV, shoulder/elbow position, and dichotomous variables.

RESULTS

Twenty patients were enrolled, of which 20 had PVP measurements and 11 also had SVV measurements. Multiple regression analysis demonstrated significant predictive relationships for CVP using PVP (CVP = 6.7701 + 0.2312 × PVP - 0.1288 × Shoulder + 12.127 × Movement - 4.4805 × Neck line), SVV (CVP = 14.578 - 0.3951 × SVV + 18.113 × Movement), and SVV and PVP (CVP = 4.2997 - 1.1675 × SVV + 0.3866 × PVP + 18.246 × Awake + 0.1467 × Shoulder = 0.4525 × Elbow + 15.472 × Foot line + 10.202 × Arm line).

DISCUSSION

PVP and SVV are moderately good predictors of CVP. Combining PVP and SVV and adding variables related to body position, movement, ventilation, and sleep/wake state further improves the predictive value of the model. The models illustrate the importance of standardizing patient position, minimizing movement, and placing intravenous lines proximally in the upper extremity or neck.