Correlation between measured inferior vena cava diameter and right atrial pressure depends on the echocardiographic method used in patients who are mechanically ventilated

What are the echocardiographic findings of acute right ventricular strain that suggest pulmonary embolism?

INTRODUCTION

Pulmonary embolism (PE) is a potentially fatal disease encountered in the hospital setting. Prompt diagnosis and management can improve outcomes and survival. Unfortunately, a PE may be difficult to diagnose in a timely manner. Point-of-care ultrasound (POCUS) can assist in the evaluation for suspected PE by assessing for acute right ventricular strain. Physicians should thus be aware of these echocardiographic findings.

OBJECTIVE

This manuscript will review ten echocardiographic findings of right ventricular strain that may suggest a diagnosis of PE. It will provide a description of each finding along with the associated pathophysiology. It will also summarize the literature for the diagnostic utility of echocardiography for this indication, while providing reference parameters where applicable. Along with labeled images and video clips, the review will then illustrate how to evaluate for each of the ten findings, while offering pearls and pitfalls in this bedside evaluation.

DISCUSSION

The ten echocardiographic findings of right ventricular strain are: increased right ventricle: left ventricle size ratio, abnormal septal motion, McConnell's sign, tricuspid regurgitation, elevated pulmonary artery systolic pressure, decreased tricuspid annular plane systolic excursion, decreased S', pulmonary artery mid-systolic notching, 60/60 sign, and speckle tracking demonstrating decreased right ventricular free wall strain.

CONCLUSIONS

Physicians must recognize and understand the echocardiographic findings and associated pathophysiology of right ventricular strain. In the proper clinical context, these findings can point toward a diagnosis of PE and thereby lead to earlier initiation of directed management.

The Future of Cardiac Ultrasound in the Neonatal Intensive Care Unit

Cardiac ultrasound is increasingly used to guide hemodynamic decision making in the neonatal intensive care unit (NICU). This article focuses on likely future progress in training, accreditation, digital connectivity, miniaturization, and modality development. Many documents have been published internationally to guide cardiac ultrasound training, accreditation, and implementation in the NICU, but challenges remain in providing assessments of hemodynamic status without risking missed structural diagnoses. Advances in simulation training and digital connectivity provide an opportunity to standardize approaches across institutions and continents. Development of machine learning and ultrasound modalities in turn provide huge scope for improving robustness and completeness of assessment.

Point-of-Care Ultrasound Assessment of the Inferior Vena Cava in Mechanically Ventilated Critically Ill Children

OBJECTIVES

The objective of this study was to compare the ultrasound-measured inferior vena cava distensibility index (IVCdi), inferior vena cava distensibility variability (IVCdv), and inferior vena cava-to-aorta ratio (IVC/Ao) to other common methods to assess fluid status in mechanically ventilated pediatric critically ill patients. These methods include central venous pressure (CVP), percent fluid overload by weight (%FOw), and percent fluid overload by volume (%FOv).

METHODS

This was a prospective observational study of a convenience sample of 50 mechanically ventilated pediatric patients. Ultrasound measurements of the inferior vena cava and aorta were obtained, and the IVCdi, IVCdv, and IVC/Ao were calculated and compared to CVP, %FOw, and %FOv.

RESULTS

The median %FOw was 5%, and the median %FOv was 10%. The mean CVP ± SD was 8.6 ± 4 mm Hg. The CVP had no significant correlation with %FOw or %FOv. There was no significant correlation of the IVCdi with CVP (r = -0.145; P = .325) or %FOv (r = 0.119; P = .420); however, the IVCdi had a significant correlation with %FOw (P = .012). There was also no significant relationship of the IVCdv with CVP (r = -0.135; P = .36) or %FOv (r = 0.128; P = .385); however, there was a significant correlation between the IVCdv and %FOw (P = .012). There was no relationship between the IVC/Ao and any other measures of fluid status.

CONCLUSIONS

In this cohort of mechanically ventilated pediatric intensive care unit patients, many commonly used markers of fluid status showed weak correlations with each other. The IVCdi and IVCdv significantly correlated with %FOw and may have potential as markers for fluid overload in this patient population.

Coronary Sinus Diameter to Inferior Vena Cava Diameter Ratio in the Diagnosis of Cardiac Tamponade: A Novel Approach

BACKGROUND

In cardiac tamponade, coronary sinus (CS) as an intrapericardial structure can be easily compressed, whereas inferior vena cava (IVC) dilates. This inverse relationship may augment their roles in the evaluation of tamponade imaging.

AIM

We assessed the usefulness of computerized tomographic measures of CS diameter and also CS/IVC ratio to predict tamponade in clinically stable patients with large pericardial effusion.

METHODS

Sixty-six clinically stable patients who had large pericardial effusions were included. Coronary sinus diameter was measured from the point at 1 cm proximal to the CS ostium. Inferior vena cava diameter was measured from the segment between its right atrial orifice and hepatic vein.

RESULTS

Patients with tamponade had smaller CS diameter and CS/IVC ratio. After adjusting with other parameters, only either CS diameter or CS/IVC ratio predicted tamponade, respectively. (Nagelkerke r value for CS was 53.7% and 72.1% for CS/IVC ratio). In Receiver Operating Characteristic Curve analysis, a cutoff value of 6.85 mm for CS diameter had 82.6% sensitivity and 83.7% specificity and a cutoff value of 27% for CS/IVC ratio had 87.0% sensitivity and 86.0% specificity for predicting cardiac tamponade.

CONCLUSIONS

The tomographic measures of both the CS diameter and the CS/IVC ratio predicted tamponade in clinically stable patients with large pericardial effusion. Compared with CS diameter, CS/IVC ratio seemed to be a more powerful predictor of tamponade.

Inferior Vena Cava Diameter Predicts Nephropathy in Patients Late After Fontan Palliation

Single ventricle congenital heart defect patients have improved survival with Fontan palliation. However, they remain at risk for nephropathy, as indicated by pathologic microalbuminuria. We sought to investigate whether echocardiographic measures of the inferior vena cava diameter (a surrogate for elevated CVP) indexed to the body surface area (iIVC) or cardiac index (CI) can predict the presence of nephropathy in Fontan patients. We performed a single-center case-control study, including 39 asymptomatic Fontan (age 14.8 ± 7.9 years) and 29 healthy controls (age 12.7 ± 2.7 years). The primary outcome was abnormal microalbumin-creatinine ratio (MCR) from the first-morning void urine in Fontan patients. Measurements of iIVC and CI were derived using transthoracic echocardiography by two investigators with a high intra-class correlation coefficient (ICC = 0.97). Group comparison between Fontan and controls as well as between Fontan with normal and abnormal MCR was performed using Fisher's exact and t tests. Pearson and Spearman's correlations and multivariate regressions were performed to analyze the relations between the MCR, iIVC, and CI. Abnormal MCR was noted in 13/39(33%) of Fontan patients. The mean iIVC was larger in the Fontan compared to controls (p < 0.0001) and in Fontan with abnormal MCR compared to those with normal MCR (p = 0.0006). A positive correlation (r = 0.62; p < 0.001) was noted between MCR and iIVC. All patients with abnormal MCR had the iIVC > 1 cm/m². There were no significant relations between the CI and MCR. Significant prevalence of nephropathy late after Fontan palliation warrents screening. Echocardiographic measurement of iIVC could serve as one of the screening measures. The finding of the iIVC diameter > 1 cm/m² should prompt further renal evaluation.

Can non-invasive ventilation modify central venous pressure? Comparison between invasive measurement and ultrasonographic evaluation

Central venous pressure (CVP) is primarily measured to assess intravascular volume status and heart preload. In clinical practice, the measuring device most commonly used in emergency departments and intensive care units, is an electronic transducer that interconnects a central venous catheter (CVC) with a monitoring system. Non-invasive ventilation (NIV) consists in a breathing support that supplies a positive pressure in airways through a mask or a cask though not using an endotracheal prosthesis. In emergency settings, non-invasive ultrasonography evaluation of CVP, and hence of intravascular volume status entail the measurement by a subxiphoid approach of inferior vena cava diameter and its variations in relation to respiratory activity. In the literature, there are many studies analyzing the ability to estimate CVP through ultrasonography, rating inspiratory and expiratory vena cava diameters and their ratio, defined as inferior vena cava collapsibility index (IVC-CI). At the same time, the effects of invasive mechanical ventilation on blood volume and the correlation during ventilation between hemodynamic invasive measurement of CVP and inferior vena cava diameters have already been demonstrated. Nevertheless, there are no available data regarding the hemodynamic effects of NIV and the potential correlations during this kind of ventilation between invasive and non-invasive CVP measurements. Therefore, this study aims to understand whether there exists or not an interrelationship between the values of CVP assessed invasively through a CVC and non-invasively through the IVC-CI in patients with severe respiratory distress, and above all to evaluate if these means of assessment can be influenced using NIV.

Diagnostic Accuracy of the Inferior Vena Cava Collapsibility to Predict Fluid Responsiveness in Spontaneously Breathing Patients With Sepsis and Acute Circulatory Failure

OBJECTIVE

To investigate whether the collapsibility index of the inferior vena cava recorded during a deep standardized inspiration predicts fluid responsiveness in nonintubated patients.

DESIGN

Prospective, nonrandomized study.

SETTING

ICUs at a general and a university hospital.

PATIENTS

Nonintubated patients without mechanical ventilation (n = 90) presenting with sepsis-induced acute circulatory failure and considered for volume expansion.

INTERVENTIONS

We assessed hemodynamic status at baseline and after a volume expansion induced by a 30-minute infusion of 500-mL gelatin 4%.

MEASUREMENTS AND MAIN RESULTS

We measured stroke volume index and collapsibility index of the inferior vena cava under a deep standardized inspiration using transthoracic echocardiography. Vena cava pertinent diameters were measured 15-20 mm caudal to the hepatic vein junction and recorded by bidimensional imaging on a subcostal long-axis view. Standardized respiratory cycles consisted of a deep standardized inspiration followed by passive exhalation. The collapsibility index expressed in percentage equaled the ratio of the difference between end-expiratory and minimum-inspiratory diameter over the end-expiratory diameter. After volume expansion, a relevant (≥ 10%) stroke volume index increase was recorded in 56% patients. In receiver operating characteristic analysis, the area under curve for that collapsibility index was 0.89 (95% CI, 0.82-0.97). When such index is superior or equal to 48%, fluid responsiveness is predicted with a sensitivity of 84% and a specificity of 90%.

CONCLUSIONS

The collapsibility index of the inferior vena cava during a deep standardized inspiration is a simple, noninvasive bedside predictor of fluid responsiveness in nonintubated patients with sepsis-related acute circulatory failure.

Evaluation of the utility of cardiac ultrasonography of patients in a surgical intensive care unit

Background

Ultrasonography is being more commonly used by intensivists to assess the hemodynamic status of patients in intensive care units (ICUs) and for other purposes.

Objective

To review the indications for and evaluate the impact of cardiac ultrasonography (CUS) on the management of patients in a surgical ICU (SICU).

Method

We conducted a retrospective observational cohort study of patients in the SICU who underwent CUS performed by intensivists at King Chulalongkorn Memorial Hospital from January 2011 to March 2013. CUS was used to determine (1) preload (using inferior vena cava (IVC) diameter and collapsibility index), (2) cardiac contractility (using subjective assessment and fractional shortening), and (3) other miscellaneous findings.

Result

We included data from 157 patients (96 male and 61 female) whose age ranged from 15 to 99 years (mean 63.5 years) in the study. CUS was performed 190 times in these 157 patients. The most common indication for CUS was hemodynamic status assessment (78), followed by shock (69), oliguria (35), and other (8). CUS results led to 71 changes in management (37% of cases) ; namely, fluid challenge (38), inotropic drug management (7), drainage of pleural/abdominal fluid (12), and other changes (14). A weakly-positive correlation between the IVC diameter and CVP (Pearson’s r = 0.45) was demonstrated. The overall mortality rate was 14.6%.

Conclusion

CUS performed by intensivists can be used to assess the hemodynamic status of patients in the SICU, especially those with shock or oliguria, and lead to changes in the management of these patients.

Image-based resuscitation of the hypotensive patient with cardiac ultrasound: An evidence-based review

This article is a detailed review of the literature regarding the use of cardiac ultrasound for the resuscitation of hypotensive patients. In addition, figures regarding windows and description of how to perform the test are included.

Critical Care Basic Ultrasound Learning Goals for American Anesthesiology Critical Care Trainees: Recommendations from an Expert Group

OBJECTIVE

In this review, we define learning goals and recommend competencies concerning focused basic critical care ultrasound (CCUS) for critical care specialists in training.

DESIGN

The narrative review is, and the recommendations contained herein are, sponsored by the Society of Critical Care Anesthesiologists. Our recommendations are based on a structured literature review by an expert panel of anesthesiology intensivists and cardiologists with formal training in ultrasound. Published descriptions of learning and training routines from anesthesia-critical care and other specialties were identified and considered. Sections were written by groups with special expertise, with dissent included in the text.

RESULTS

Learning goals and objectives were identified for achieving competence in the use of CCUS at a specialist level (critical care fellowship training) for diagnosis and monitoring of vital organ dysfunction in the critical care environment. The ultrasound examination was divided into vascular, abdominal, thoracic, and cardiac components. For each component, learning goals and specific skills were presented. Suggestions for teaching and training methods were described.

DISCUSSION

Immediate bedside availability of ultrasound resources can dramatically improve the ability of critical care physicians to care for critically ill patients. Anesthesia--critical care medicine training should have definitive expectations and performance standards for basic CCUS interpretation by anesthesiology--critical care specialists. The learning goals in this review reflect current trends in the multispecialty critical care environment where ultrasound-based diagnostic strategies are already frequently applied. These competencies should be formally taught as part of an established anesthesiology-critical care medicine graduate medical education programs.

Echocardiographic Assessment of Right Atrial Pressure in a Pediatric and Young Adult Population

Right atrial pressure (RAP) reflects right-sided cardiac hemodynamics and is useful in management of patients with cardiac and systemic disease. Studies in older adults demonstrated that inferior vena cava (IVC) diameter, IVC collapsibility index, hepatic vein systolic filling fraction (SFF), and right atrial volume (RAV) correlated with mean RAP at catheterization. This study aimed to assess the utility of echocardiographic parameters for assessment of RAP in children and young adults. Patients with pulmonary hypertension or heart transplantation undergoing right heart catheterization were recruited for this prospective observational pilot study. Transthoracic echocardiographic assessment of RAP was performed simultaneously with catheterization. For each parameter, three consecutive cardiac cycles were recorded. Long- and short-axis images of the IVC were obtained. RAV was assessed by area-length and biplane methods. IVC diameters and RAV were indexed to body surface area (BSA)(0.5) and (BSA)(1.4), respectively. Relationships between echocardiographic parameters and mean RAP were correlated using "Pearson's r." Fifty subjects aged 0.3-23 years (median 13, mean 12.3 ± 7 years) were enrolled. Mean RAP correlated modestly with RAV (r = 0.51, p < 0.001). Long-axis IVCmax (r = 0.30, p < 0.05) and tricuspid E wave velocity (r = 0.36, p < 0.01) also correlated with mean RAP. RV free wall tissue Doppler velocities, IVC collapsibility index, and hepatic vein SFF had no relation to mean RAP. In a pediatric and young adult population with pulmonary hypertension or heart transplantation, echocardiographic assessment of RAV and long-axis IVCmax provided a reasonable estimate of mean RAP. IVC collapsibility index and hepatic vein SFF demonstrated no association with mean RAP.

Measurement of Central Venous Pressure Using Ultrasound in Emergency Department

Background:

In order to assessment of intravascular fluid measurement of central venous pressure (CVP) is used via central venous catheterization (CVC). This procedure is highly invasive and may cause serious complications such as pneumothorax, infection, hematoma and etc. It is so valuable procedure if we can uses a less invasive or noninvasive procedure to assess patients intravascular fluid in critical positions.

Objectives:

In this study, the ultrasound was used to measure the central venous pressure (CVP).

Patients and Methods:

In this study, patients with Central venous catheterization were selected using simple random sampling. The largest diameter of longitudinal, transverse views and the cross-section of inferior vena cava (IVC) and internal jugular vein (IJV) were measured using the ultrasound in the bedside of the patients. Central venous pressure was measured using routine methods. Correlations between variables were analyzed using SPSS and linear regression.

Results:

Twenty patients with the mean age of 60.3 were studied. The main reason for cardiac catheterization was shock. There are no relationship between anterior posterior diameter of inferior vena cava and CVP of patients (P = 0.257). The longest diameter of IVC in ultrasonographic transverse view had significant association with CVP of patients (P = 0.045) but in patients with BMI > 25 it was not significant. Cross section of internal jugular vein had significant association with CVP of patients (P = 0.003). Longitudinal diameter of internal jugular vein had no significant association with CVP of patients (P = 0.052), but transverse diameter of internal jugular generally had significant association with CVP of patients (P = 0.003). Cross section of internal jugular had significant association with CVP (P = 0.001).

Conclusions:

Noninvasive assessment of the patient hydration condition using the ultrasound is a simple and practicable measure in emergency. With regard to the considerations, it is possible to estimate CVP via diameter measurement and cross-section of the central veins.

Does inferior vena cava respiratory variability predict fluid responsiveness in spontaneously breathing patients?

INTRODUCTION

We have almost no information concerning the value of inferior vena cava (IVC) respiratory variations in spontaneously breathing ICU patients (SBP) to predict fluid responsiveness.

METHODS

SBP with clinical fluid need were included prospectively in the study. Echocardiography and Doppler ultrasound were used to record the aortic velocity-time integral (VTI), stroke volume (SV), cardiac output (CO) and IVC collapsibility index (cIVC) ((maximum diameter (IVCmax)- minimum diameter (IVCmin))/ IVCmax) at baseline, after a passive leg-raising maneuver (PLR) and after 500 ml of saline infusion.

RESULTS

Fifty-nine patients (30 males and 29 females; 57 ± 18 years-old) were included in the study. Of these, 29 (49 %) were considered to be responders (≥10 % increase in CO after fluid infusion). There were no significant differences between responders and nonresponders at baseline, except for a higher aortic VTI in nonresponders (16 cm vs. 19 cm, p = 0.03). Responders had a lower baseline IVCmin than nonresponders (11 ± 5 mm vs. 14 ± 5 mm, p = 0.04) and more marked IVC variations (cIVC: 35 ± 16 vs. 27 ± 10 %, p = 0.04). Prediction of fluid-responsiveness using cIVC and IVCmax was low (area under the curve for cIVC at baseline 0.62 ± 0.07; 95 %, CI 0.49-0.74 and for IVCmax at baseline 0.62 ± 0.07; 95 % CI 0.49-0.75). In contrast, IVC respiratory variations >42 % in SBP demonstrated a high specificity (97 %) and a positive predictive value (90 %) to predict an increase in CO after fluid infusion.

CONCLUSIONS

In SBP with suspected hypovolemia, vena cava size and respiratory variability do not predict fluid responsiveness. In contrast, a cIVC >42 % may predict an increase in CO after fluid infusion.

Early markers of right heart involvement in regular smokers by Pocket Size Imaging Device

PURPOSE

To test the diagnostic power of Pocket Size Imaging Device (PSID) in detecting early signs of right heart (RH) involvement in regular smokers (RS) free of overt cardiac involvement.

METHODS

One-hundred-forty-three regular smokers and 51 healthy controls, comparable for age and sex, underwent physical exam (PE), PSID exam and standard echocardiography. Based on a simplified Boston score, ≥1 of clinical signs (jugular venous distension, hepatomegaly, peripheral pitting oedema and abnormal pulmonary sounds) were considered indicative of RH involvement. A composite score (1 to 4) obtained by summing the points of four quantitative RH abnormalities detectable by PSID (inferior vena cava [IVC] dilatation, reduced IVC respiratory variation, right ventricular dilatation and right atrial dilatation), was generated and ≥1 of PSID abnormal signs was considered indicative of RH involvement.

RESULTS

Boston score was not significantly different between the two groups. By using PSID, smokers exhibited greater IVC diameter (p < 0.0001), right atrial diameter (p < 0.002) and higher PSID score (p < 0.005) than controls. Compared to PE, the additional diagnostic power of PSID (≥1 abnormal sign of both Boston and PSID score) was 44.9% in smokers. By dividing smokers in tertiles according to number of cigarettes per day, the third tertile showed the largest values of both IVC and right atrial dimension. Differences were confirmed by standard echocardiography. Reproducibility of PSID measurements and concordance of linear measurements between PSID and standard echo measurements was very good except for concordance of right ventricular basal diameter.

CONCLUSIONS

PSID detects early ultrasound signs of RH involvement in regular otherwise healthy smokers in comparison with PE.

Correlation between Pulmonary Artery Pressure Measured by Echocardiography and Right Heart Catheterization in Patients with Rheumatic Mitral Valve Stenosis (A Prospective Study)

INTRODUCTION

Right heart catheterization (RHC) remains the gold standard for hemodynamic assessment of the right heart and pulmonary artery. However, this is an invasive tool, and noninvasive alternatives such as transthoracic echocardiography (TTE) are preferable. Nonetheless, the correlation between measurements by TTE and RHC are debated. In this study, we prospectively examined the correlation between systolic and mean pulmonary artery pressures (sPAP and mPAP) measured by RHC and TTE in patients with hemodynamically significant rheumatic mitral stenosis (MS).

MATERIAL AND METHODS

Three hundred patients with hemodynamically significant MS undergoing TTE who were scheduled to undergo RHC within 24 hours were analyzed. PAP measurements were taken for all patients by RHC (sPAP(RHC), mPAP(RHC)). Maximum velocity of tricuspid regurgitation (TR) jet obtained by continuous-wave Doppler with adding right atrial (RA) pressure was used for measuring sPAP by TTE (sPAP(TRVmax)). Mean PAP was measured using either pulmonary artery acceleration time (mPAP(PAAT)) method or by adding RA pressure to velocity-time integral of TR jet (mPAP(TRVTI)).

RESULTS

A good correlation between sPAP(RHC) and sPAP(TRVmax) (r = 0.89, P < 0.001), between mPAP(RHC) and mPAP(PAAT) (r = 0.9, P < 0.001), and between mPAP(RHC) and mPAP(TRVTI) (r = 0.92, P < 0.001) was found. Sensitivity and specificity of sPAP(TRV) max in detecting pulmonary hypertension (PH) were 92.8% and 86.6% and of mPAP(PAAT) were 94.1% and 73.3%, respectively.

CONCLUSION

The noninvasive assessment of sPAP and mPAP by TTE correlates well with invasive measurements and has an acceptable specificity and sensitivity in detecting PH in patients with hemodynamically significant MS.

International evidence-based recommendations for focused cardiac ultrasound

BACKGROUND

Focused cardiac ultrasound (FoCUS) is a simplified, clinician-performed application of echocardiography that is rapidly expanding in use, especially in emergency and critical care medicine. Performed by appropriately trained clinicians, typically not cardiologists, FoCUS ascertains the essential information needed in critical scenarios for time-sensitive clinical decision making. A need exists for quality evidence-based review and clinical recommendations on its use.

METHODS

The World Interactive Network Focused on Critical UltraSound conducted an international, multispecialty, evidence-based, methodologically rigorous consensus process on FoCUS. Thirty-three experts from 16 countries were involved. A systematic multiple-database, double-track literature search (January 1980 to September 2013) was performed. The Grading of Recommendation, Assessment, Development and Evaluation method was used to determine the quality of available evidence and subsequent development of the recommendations. Evidence-based panel judgment and consensus was collected and analyzed by means of the RAND appropriateness method.

RESULTS

During four conferences (in New Delhi, Milan, Boston, and Barcelona), 108 statements were elaborated and discussed. Face-to-face debates were held in two rounds using the modified Delphi technique. Disagreement occurred for 10 statements. Weak or conditional recommendations were made for two statements and strong or very strong recommendations for 96. These recommendations delineate the nature, applications, technique, potential benefits, clinical integration, education, and certification principles for FoCUS, both for adults and pediatric patients.

CONCLUSIONS

This document presents the results of the first International Conference on FoCUS. For the first time, evidence-based clinical recommendations comprehensively address this branch of point-of-care ultrasound, providing a framework for FoCUS to standardize its application in different clinical settings around the world.

Appraising cardiac dysfunction in liver transplantation: an ongoing challenge

End-stage liver disease (ESLD) is a multisystemic disease that adversely and mutually aggravates other organs such as the heart. Cardiac dysfunction in ESLD encompasses a spectrum of disease that could be aggravated, precipitated or be occurring hand-in-hand with coexisting aetiological factors precipitating cirrhosis. Additionally and more complexly, liver transplantation, the curative modality of ESLD, is responsible for additional intra- and postoperative short- and long-term cardiac morbidity. The phenotypic distinction of the different forms of cardiac dysfunction in ESLD albeit important prognostically and therapeutically is not allowed by the current societal recommendations, due to conceptual, and methodological limitations in the appraisal of cardiac function and structure in ESLD and in designing studies that are based on this appraisal. This review comprehensively discusses the spectrum of cardiac dysfunction in ESLD, discusses the limitations of the current appraisal of cardiac dysfunction in ESLD, and proposes a hypothetical approach for studying cardiac dysfunction in liver transplant candidates.

Can Nephrologists Use Ultrasound to Evaluate the Inferior Vena Cava? A Cross-Sectional Study of the Agreement between a Nephrologist and a Cardiologist

Background/Aims

The costs and the need for a specialist impair the implementation of ultrasonography for evaluating the inferior vena cava (IVC) to assess the volemic status in hemodialysis patients. We investigated whether a nephrologist with limited ultrasound training can accurately assess the IVC in patients undergoing hemodialysis.

Methods

A cardiologist and a nephrologist consecutively measured the indexed IVC expiratory diameter (VCDi) and the IVC collapsibility index (IVCCI) of 52 patients during hemodialysis sessions. In protocol I, the nephrologist used a regular ultrasound system (RUS) and the cardiologist used a cardiovascular ultrasound equipment; in protocol II, the machines were interchanged. Pearson and kappa coefficients and the interexaminer agreement by the Bland-Altman method were calculated.

Results

The VCDi measurements showed a strong correlation in both protocols (r = 0.88 and 0.84 in protocols I and II, respectively). The volemic classifications were excellent in protocol I (kappa = 0.82 and 0.93 by VCDi and IVCCI, respectively) and substantial in protocol II (kappa = 0.77 and 0.75 by VCDi and IVCCI, respectively). The interexaminer agreement on the VCDi measurements was very good in both protocols.

Conclusions

Ultrasound evaluation of the IVC can be performed by nephrologists using an RUS to assess the volemic status in hemodialysis patients.

The diameter of the inferior vena cava provides a noninvasive way of calculating central venous pressure in neonates

AIM

To explore a less invasive way of assessing preload in neonates than fitting catheters to measure central venous pressure (CVP). This study evaluated the relationship between inferior vena cava (IVC) measurements and gestational age (GA) or body weight (BW) in term and premature infants and the correlation between those measurements and CVP in sick infants under mechanical ventilation.

METHODS

We studied 57 clinically stable infants, together with 14 sick infants fitted with central venous catheters to measure CVP. Subcostal transverse views were recorded at the level of the left branch of portal vein, and the minimum (DS ) and maximum (DL ) diameters of the IVC were measured. We evaluated the values of DS and DL and the S/L ratio (DS divided by DL ) in the clinically stable infants and the correlation between S/L and CVP in the sick infants with central catheters.

RESULTS

DS and DL correlated positively and strongly with both GA and BW, whereas S/L was almost independent of both GA and BW and correlated strongly with CVP.

CONCLUSION

At the subcostal transverse views, S/L is much less affected by either GA or BW than DS or DL and correlates strongly with CVP in mechanically ventilated infants.

Does bedside sonographic measurement of the inferior vena cava diameter correlate with central venous pressure in the assessment of intravascular volume in children?

OBJECTIVES

Previous studies demonstrated that the collapsibility index (percent decrease in inferior vena cava [IVC] diameter with inspiration) of 50% or greater and an IVC/aorta ratio of 0.8 or less correlated with a low intravascular volume. Our study sought to determine if bedside ultrasound (BUS) measurements of the IVC diameter correlate with central venous pressure (CVP) measurements as an indicator of intravascular volume status in acutely ill children.

METHODS

A convenience sample of children younger than 21 years who were admitted to the pediatric critical care unit and required CVP monitoring had BUS measurements of both IVC and aortic diameters with simultaneous CVP measurement. The collapsibility index (sagittal view) and IVC/aorta ratio (transverse view) were calculated from these measurements. A CVP of 8 mm Hg or less was considered as a marker for decreased intravascular volume.

RESULTS

Of the 51 participants, 21 (43%) had a CVP of 8 mm Hg or less. Eight (16%) of 51 children had a collapsibility index 50% or greater, and 8 (18%) of 43 had an IVC/aorta ratio of 0.8 or less. The sensitivity of a collapsibility index 0.5 or greater to predict a CVP of 8 mm Hg or less was 14%, the specificity was 83%, the positive predictive value was 38%, and the negative predictive value was 57%. Neither collapsibility index (r = -0.23, P = 0.11) nor IVC/aorta (r = -0.19, P = 0.22) correlated with CVP in assessing intravascular volume in our study population.

CONCLUSIONS

Based on these data, the IVC and aortic measurements by BUS are not reliable indicators of intravascular volume (as determined by CVP) in acutely ill children.

Impact of intra-abdominal pressure on retrohepatic vena cava shape and flow in mechanically ventilated pigs

Conflicting results have been found regarding correlations between right atrial pressure (RAP) and inferior vena cava (IVC) diameter in mechanically ventilated patients. This finding could be related to an increase in intra-abdominal pressure (IAP). This study was designed to clarify whether variations in IVC flow rate caused by positive pressure ventilation are associated with changes in the retrohepatic IVC cross-section (ΔIVC) during major changes in volume status and IAP. Nine pigs were anesthetized, mechanically ventilated and equipped. IAP was set at 0, 15 and 30 mmHg during two conditions, i.e. normovolemia and hypovolemia, generated by blood removal to obtain a mean arterial pressure value lower than 60 mmHg. At each IAP increment, cardiac output, IVC flow and surface area were respectively assessed by flowmeters and transesophageal echocardiography. At normal IAP, even in presence of respiratory changes in IVC flows, no ΔIVC were observed during the two conditions. At high IAP, neither ΔIVC nor modulations of IVC flow were observed whatever the volemic status. The majority of animals with an IVC area of less than 0.65 cm(2) showed evidence of IAP greater than RAP values. Negative RAP-IAP pressure gradients were found to occur with an IVC area of less than 0.65 cm(2), suggesting that IVC dimensions determined using standard ultrasound techniques may indicate the direction of the RAP-IAP gradient. The clinical relevance of the present findings is that volume status should not be estimated from retrohepatic IVC dimensions in cases of high IAP.

Demonstration of inferior vena cava compression by probe pressure during subxiphoid echocardiography

We sought to compare the inferior vena cava diameter measured by transthoracic echocardiography and by transesophageal echocardiography in human and animals. Transthoracic echocardiography yielded lower inferior vena cava diameter values than transesophageal echocardiography. Adult and pediatric intensivists should pay attention to the risk of false measurement of the inferior vena cava anterior-posterior diameter that may be due to compression of the inferior vena cava by the sonographic probe when the subxiphoid view is used.

Does a simple bedside sonographic measurement of the inferior vena cava correlate to central venous pressure?

BACKGROUND

Bedside ultrasound has been suggested as a non-invasive modality to estimate central venous pressure (CVP).

OBJECTIVE

Evaluate a simple bedside ultrasound technique to measure the diameter of the inferior vena cava (IVC) and correlate to simultaneously measured CVP. Secondary comparisons include anatomic location, probe orientation, and phase of respiration.

METHODS

An unblinded prospective observation study was performed in an emergency department and critical care unit. Subjects were a convenience sample of adult patients with a central line at the superior venocaval-atrial junction. Ultrasound measured transverse and longitudinal diameters of the IVC at the subxiphoid, suprailiac, and mid-abdomen, each measured at end-inspiration and end-expiration. Correlation and regression analysis were used to relate CVP and IVC diameters.

RESULTS

There were 72 subjects with a mean age of 67 years (range 21-94 years), 37 (53%) male, enrolled over 9 months. Seven subjects were excluded for tricuspid valvulopathy. Primary diagnoses were: respiratory failure 12 (18%), sepsis 11 (17%), and pancreatitis 3 (5%). There were 28 (43%) patients mechanically ventilated. Adequate measurements were obtainable in 57 (89%) using the subxiphoid, in 44 (68%) using the mid-abdomen, and in 28 (43%) using the suprailiac views. The correlation coefficients were statistically significant at 0.49 (95% confidence interval [CI] 0.26-0.66), 0.51 (95% CI 0.23-0.71), and 0.50 (95% CI 0.14-0.74) for end-inspiratory longitudinal subxiphoid, midpoint, and suprailiac views, respectively. Transverse values were statistically significant at 0.42 (95% CI 0.18-0.61), 0.38 (95% CI 0.09-0.61), and 0.67 (95% CI 0.40-0.84), respectively. End-expiratory measurements gave similar or slightly less significant values.

CONCLUSION

The subxiphoid was the most reliably viewed of the three anatomic locations; however, the suprailiac view produced superior correlations to the CVP. Longitudinal views generally outperformed transverse views. A simple ultrasound measure of the IVC yields weak correlation to the CVP.

Emergency echocardiography

Emergency echocardiography refers to the use of cardiac ultrasound to address critical and time-sensitive clinical questions during the initial evaluation and treatment of the critically ill patient presenting to the emergency department. The information obtained can be pivotal to a physician's clinical decision making and can guide further diagnostic or therapeutic interventions. This article provides an evidence-based discussion of the common uses of emergency transthoracic echocardiography, as well as its benefits and limitations in the current practice of emergency medicine.

Usefulness of respiratory variation of inferior vena cava diameter for estimation of elevated central venous pressure in children with cardiovascular disease

BACKGROUND

The purpose of the present study was to determine the relationship of inferior vena cava diameter (IVCD) and its respirophasic variation (IVC collapsibility index: IVCCI) with central venous pressure (CVP), and thereby to provide reference cut-offs for such IVC parameters to estimate elevation in CVP in pediatric patients with cardiovascular disease.

METHODS AND RESULTS

The study involved consecutive pediatric patients (n = 118) with various heart diseases who either had a central venous catheter in the cardiac intensive care unit or underwent cardiac catheterization. The maximum (IVCD(max)) and minimum (IVCD(min)) diameters of IVC were measured on ultrasound simultaneously with measurements of mean CVP. IVCD(max), IVCD(min) and IVCCI correlated significantly with CVP (R² = 0.26, 0.47 and 0.41, respectively) in spontaneously breathing patients, but not in mechanically ventilated patients. Receiver operator characteristic curve analysis indicated that IVCCI under spontaneous breathing had the best area under the curve, with sensitivity of 1.0 and specificity of 0.98 for a cut-off of 0.22 to predict elevated CVP ≥ 10 mmHg.

CONCLUSIONS

IVCCI seems to be a useful and accurate non-invasive index for estimation of elevated CVP in pediatric patients with cardiovascular disease.

Use of ultrasound in the ICU

Echography has developed as an indispensable tool in diagnosis and subsequent therapy in the critically ill. Although pulmonary and abdominal ultrasounds play a major role in their management, this article will discuss the advantages and indications of echocardiography in the intensive care unit (ICU). The assessment of morphological abnormalities, left or right ventricular malfunction, pulmonary arterial hypertension and valvular dysfunctions is a routine indication of echocardiography. Actually, besides contractility, several preload and even afterload indicators can also be assessed. In short, this bedside tool rapidly provides insight in the haemodynamics without invasive pressure estimations.

Respiratory maneuvers in echocardiography: a review of clinical applications

During echocardiographic examination, respiration induces cyclic physiological changes of intracardiac haemodynamics, causing normal variations of the right and left ventricle Doppler inflows and outflows and physiological variation of extracardiac flows. The respiration related hemodynamic variation in intra and extracardiac flows may be utilized in the echocardiography laboratory to aid diagnosis in different pathological states. Nevertheless, physiologic respiratory phases can cause excessive translational motion of cardiac structures, lowering 2D image quality and interfering with optimal Doppler interrogation of flows or tissue motion.

This review focuses on the impact of normal respiratory cycle and provocative respiratory maneuvers in echocardiographic examination, both in physiological and pathological states, emphasizing their applications in specific clinical situations.

Intensivist use of hand-carried ultrasonography to measure IVC collapsibility in estimating intravascular volume status: correlations with CVP

BACKGROUND

Volume status assessment is an important aspect of patient management in the surgical intensive care unit (SICU). Echocardiologist-performed measurement of IVC collapsibility index (IVC-CI) provides useful information about filling pressures, but is limited by its portability, cost, and availability. Intensivist-performed bedside ultrasonography (INBU) examinations have the potential to overcome these impediments. We used INBU to evaluate hemodynamic status of SICU patients, focusing on correlations between IVC-CI and CVP.

STUDY DESIGN

Prospective evaluation of hemodynamic status was conducted on a convenience sample of SICU patients with a brief (3 to 10 minutes) INBU examination. INBU examinations were performed by noncardiologists after 3 hours of didactics in interpreting and acquiring two-dimensional and M-mode images, and > or =25 proctored examinations. IVC-CI measurements were compared with invasive CVP values.

RESULTS

Of 124 enrolled patients, 101 had CVP catheters (55 men, mean age 58.3 years, 44.6% intubated). Of these, 18 patients had uninterpretable INBU examinations, leaving 83 patients with both CVP monitoring devices and INBU IVC evaluations. Patients in three IVC-CI ranges (<0.20, 0.20 to 0.60, and >0.60) demonstrated significant decrease in mean CVP as IVC-CI increased (p = 0.023). Although <5% of patients with IVC-CI <0.20 had CVP <7 mmHg, >40% of this group had a CVP >12 mmHg. Conversely, >60% of patients with IVC-CI >0.6 had CVP <7 mmHg.

CONCLUSIONS

Measurements of IVC-CI by INBU can provide a useful guide to noninvasive volume status assessment in SICU patients. IVC-CI appears to correlate best with CVP in the setting of low (<0.20) and high (>0.60) collapsibility ranges. Additional studies are needed to confirm and expand on findings of this study.

The Right Subclavian Vein Can Be Used as a Surrogate of the Inferior Vena Cava, as an Echocardiographic Indicator of Systemic Venous Congestion

Respiratory variations in the caliber of the inferior vena cava, imaged in the subcostal view with the patient supine, correlated well with respiratory variation in the caliber of the right subclavian vein with the patient reclining at a 45 degrees angle. The subclavian vein was imaged by a right supraclavicular approach. We suggest that the right subclavian vein caliber be used as a surrogate of the inferior vena cava caliber when the latter cannot be used because of obesity, epigastric tenderness, or other reasons.

Inferior vena cava diameter and central venous pressure correlation during cardiac surgery

OBJECTIVE

The purpose of this study was to determine whether a relationship exists between the inferior vena cava diameter (IVCD) or the superior vena cava diameter (SVCD) measured at the point of entry into the right atrium using transesophageal echocardiography (TEE) and the central venous pressure (CVP) under different experimental conditions.

DESIGN

Prospective study.

SETTING

University hospital, single institution.

PARTICIPANTS

Seventy patients undergoing elective cardiac surgery.

INTERVENTIONS

CVP, IVCD, and SVCD were measured in a 2-dimensional, long-axis midesophageal bicaval view at end-diastole with electrocardiographic synchronization. Data were recorded during suspended ventilation, before and after leg elevation, and at different levels of positive end-expiratory pressure (0, 5, and 10 cmH(2)O).

MEASUREMENTS AND MAIN RESULTS

The relationship between IVCD and CVP had 2 portions: A first (CVP <or=11 mmHg) in which the IVCD showed a strong correlation with the CVP (R = 0.801, p < 0.001; CVP = 2.009 + [0.312 * IVCD]) and a second (CVP >11 mmHg) in which the correlation was poor (R = 0.272, p = 0.065). No correlation between SVCD and CVP was observed.

CONCLUSION

A strong correlation between TEE-derived IVCD measured at the point of entry into the right atrium and CVP was observed in cardiac surgical patients when CVP was <or=11 mmHg.

Handcarried ultrasound measurement of the inferior vena cava for assessment of intravascular volume status in the outpatient hemodialysis clinic

Accurate intravascular volume assessment is critical in the treatment of patients who receive chronic hemodialysis (HD) therapy. Clinically assessed dry weight is a poor surrogate of intravascular volume; however, ultrasound assessment of the inferior vena cava (IVC) is an effective tool for volume management. This study sought to determine the feasibility of using operators with limited ultrasound experience to assess IVC dimensions using hand-carried ultrasounds (HCU) in the outpatient clinical setting. The IVC was assessed in 89 consecutive patients at two outpatient clinics before and after HD. Intradialytic IVC was recorded during episodes of hypotension, chest pain, or cramping. High-quality IVC images were obtained in 79 of 89 patients. Despite that 89% of patients presented at or above dry weight, 39% of these patients were hypovolemic by HCU. Of the 75% of patients who left HD at or below goal weight, 10% were still hypervolemic by HCU standards. Hypovolemic patients had more episodes of chest pain and cramping (33 versus 14%, P = 0.06) and more episodes of hypotension (22 versus 3%, P = 0.02). The clinic with a higher prevalence of predialysis hypovolemia had significantly more intradialytic adverse events (58 versus 27%; P = 0.01). HCU measurement of the IVC is a feasible option for rapid assessment of intravascular volume status in an outpatient dialysis setting by operators with limited formal training in echocardiography. There is a poor relationship between dry weight goals and IVC collapsibility. Practice variation in the maintenance of volume status is correlated with significant differences in intradialysis adverse events.