Inferior vena cava collapsibility to guide fluid removal in slow continuous ultrafiltration: a pilot study

Inferior vena cava ultrasound and other techniques for assessment of intravascular and extravascular volume: an update

Goals of volume management are to accurately assess intravascular and extravascular volume and predict response to volume administration, vasopressor support or volume removal. Data are reviewed that support the following: (i) Dynamic parameters reliably guide volume administration and may improve clinical outcomes compared with static parameters, but some are invasive or only validated with mechanical ventilation without spontaneous breathing. (ii) Ultrasound visualization of inferior vena cava (IVC) diameter variations with respiration reliably assesses intravascular volume and predicts volume responsiveness. (iii) Although physiology of IVC respiratory variations differs with mechanical ventilation and spontaneous breathing, the IVC collapsibility index (CI) and distensibility index are interconvertible. (iv) Prediction of volume responsiveness by IVC CI is comparable for mechanical ventilation and spontaneous breathing patients. (v) Respiratory variations of subclavian/proximal axillary and internal jugular veins by ultrasound are alternative sites, with comparable reliability. (vi) Data support clinical applicability of IVC CI to predict hypotension with anesthesia, guide ultrafiltration goals, predict dry weight, predict intra-dialytic hypotension and assess acute decompensated heart failure. (vii) IVC ultrasound may complement ultrasound of heart and lungs, and abdominal organs for venous congestion, for assessing and managing volume overload and deresuscitation, renal failure and shock. (viii) IVC ultrasound has limitations including inadequate visualization. Ultrasound data should always be interpreted in clinical context. Additional studies are required to further assess and validate the role of bedside ultrasonography in clinical care.

Proceedings of the 2022 UAB CRRT Academy: Non-Invasive Hemodynamic Monitoring to Guide Fluid Removal with CRRT and Proliferation of Extracorporeal Blood Purification Devices

In 2022, we celebrated the 15th anniversary of the University of Alabama at Birmingham (UAB) Continuous Renal Replacement Therapy (CRRT) Academy, a 2-day conference attended yearly by an international audience of over 100 nephrology, critical care, and multidisciplinary trainees and practitioners. This year, we introduce the proceedings of the UAB CRRT Academy, a yearly review of select emerging topics in the field of critical care nephrology that feature prominently in the conference. First, we review the rapidly evolving field of non-invasive hemodynamic monitoring and its potential to guide fluid removal by renal replacement therapy (RRT). We begin by summarizing the accumulating data associating fluid overload with harm in critical illness and the potential for harm from end-organ hypoperfusion caused by excessive fluid removal with RRT, underscoring the importance of accurate, dynamic assessment of volume status. We describe four applications of point-of-care ultrasound used to identify patients in need of urgent fluid removal or likely to tolerate fluid removal: lung ultrasound, inferior vena cava ultrasound, venous excess ultrasonography, and Doppler of the left ventricular outflow track to estimate stroke volume. We briefly introduce other minimally invasive hemodynamic monitoring technologies before concluding that additional prospective data are urgently needed to adapt these technologies to the specific task of fluid removal by RRT and to learn how best to integrate them into practical fluid-management strategies. Second, we focus on the growth of novel extracorporeal blood purification devices, starting with brief reviews of the inflammatory underpinnings of multiorgan dysfunction and the specific applications of pathogen, endotoxin, and/or cytokine removal and immunomodulation. Finally, we review a series of specific adsorptive technologies, several of which have seen substantial clinical use during the COVID-19 pandemic, describing their mechanisms of target removal, the limited existing data supporting their efficacy, ongoing and future studies, and the need for additional prospective trials.

Measurement of Blood Volume in Patients with Heart Failure: Clinical Relevance, Surrogates, Historical Background and Contemporary Methodology

The development of clinical congestion resulting from volume overload, either by renal fluid retention or redistribution of blood volume from venous reservoirs, is a recurrent scenario in patients with chronic heart failure (HF). As a result, the treatment of congestion, most commonly by initiating aggressive diuretic therapy, is a front-line issue in the management of patients with HF. However, the association of clinical congestion and volume overload with physical signs and symptoms, as well as other surrogates of volume assessment, has limitations in accuracy and, therefore, reliability to direct appropriate interventions. The ability to quantitate intravascular volume and identify the variability in volume profiles among patients with HF can uniquely inform individualized volume management and aid in risk stratification. This tool is provided by contemporary nuclear medicine-based BVA-100 methodology, which uses the well-established indicator-dilution principle and is a requested topic for discussion in this review.

Inferior Vena Cava Ultrasonography for Volume Status Evaluation: An Intriguing Promise Never Fulfilled

The correct determination of volume status is a fundamental component of clinical evaluation as both hypovolaemia (with hypoperfusion) and hypervolaemia (with fluid overload) increase morbidity and mortality in critically ill patients. As inferior vena cava (IVC) accounts for two-thirds of systemic venous return, it has been proposed as a marker of volaemic status by indirect assessment of central venous pressure or fluid responsiveness. Although ultrasonographic evaluation of IVC is relatively easy to perform, correct interpretation of the results may not be that simple and multiple pitfalls hamper its wider application in the clinical setting. In the present review, the basic elements of the pathophysiology of IVC behaviour, potential applications and limitations of its evaluation are discussed.

How to Determine Fluid Management Goals during Continuous Kidney Replacement Therapy in Patients with AKI: Focus on POCUS

The utilization of kidney replacement therapies (KRT) for fluid management of patients who are critically ill has significantly increased over the last years. Clinical studies have suggested that both fluid accumulation and high fluid removal rates are associated with adverse outcomes in the critically ill population receiving KRT. Importantly, the ideal indications and/or fluid management strategies that could favorably affect these patients are unknown; however, differentiating clinical scenarios in which effective fluid removal may provide benefit to the patient by avoiding congestive organ injury, compared with other settings in which this intervention may result in harm, is direly needed in the critical care nephrology field. In this review, we describe observational data related to fluid management with KRT, and examine the role of point-of-care ultrasonography as a potential tool that could provide physiologic insights to better individualize decisions related to fluid management through KRT.

Monitoring patients with acute dyspnea with serial point-of-care ultrasound of the inferior vena cava (IVC) and the lungs (LUS): a systematic review

PURPOSE

The primary aim was to investigate if treatment guided by serial ultrasound of the inferior vena cava-collapsibility index (IVC-CI) and B-lines on lung ultrasound (LUS) could reduce mortality, readmissions, and length of stay (LOS) in acutely dyspneic patients admitted to a hospital, compared to standard monitoring. The secondary aim was to determine how the changes of B-lines and IVC-CI are correlated to vitals and symptoms.

METHODS

A systematic search was conducted on PubMed, Embase, Cochrane, Google Scholar, Web of Science, Scopus, OpenGrey, ProQuest, and databases for ongoing trials. The risk of bias was assessed according to study design.

RESULTS

Of the 8258 studies identified, 50 were selected for full-text screening, and 24 studies were chosen for data extraction (19 pre-post-, two non-randomized controlled-, two randomized controlled-, and one retrospective cohort study), covering 2040 patients. Most studies were single-center and had small study populations with only heart failure patients. The risk of bias was high. No studies evaluated how the difference between two ultrasound measurements correlated with the primary outcomes. Seven studies reported that a decline in either B-lines or IVC size, or an increased IVC-CI reduced mortality, readmissions, and LOS when correlated to a single ultrasound measurement. All studies showed changes in the IVC-CI and B-lines, but these were not related to vitals or symptoms.

CONCLUSION

B-lines and IVC-CI are dynamic variables that change over time and with treatment. A single ultrasound measurement can influence prognostic outcomes, but it remains uncertain if repeated scans can have the same impact.

New aspects in cardiorenal syndrome and HFpEF

Cardiorenal syndrome (CRS) is a complex disease in which the heart and kidneys are simultaneously affected, and subsequently, the malfunction of one organ promotes the deterioration of the other. Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common form of HF. The pathophysiology of CRS is not well known and several mechanisms have been proposed. An elevation of central venous pressure seems to be one of the key points to consider, among others such as an increase in intraabdominal pressure. Several diagnostic tools have been identified to establish the diagnosis of CRS in patients with HFpEF. Currently, the availability of biomarkers of renal and cardiac injury, the use of pulmonary ultrasound, the monitoring of the size of the inferior vena cava and the study of the renal venous pattern offer a new dimension in accurately diagnosing and quantifying organ damage in CRS. Beyond the symptomatic treatment of congestion, until recently specific therapeutic tools for patients with CRS and HFpEF were not available. Interestingly, the development of new drugs such as the angiotensin/neprilysin inhibitors and sodium-glucose cotransporter-2 (SGLT-2) inhibitors offer new therapeutic strategies with potential benefits in reduction of cardiorenal adverse outcomes in this population. Randomized clinical trials that focus on patients with HFpEF are currently ongoing to delineate optimal new treatments that may be able to modify their prognosis. In addition, multidisciplinary teamwork (nephrologist, cardiologist and nurse) is expected to decrease the number of visits and the rate of hospitalizations, with a subsequent patient benefit.

Comparison of vena cava distensibility index and pulse pressure variation for the evaluation of intravascular volume in critically ill children

OBJECTIVE

In this study, the authors aimed to evaluate the effectiveness of the vena cava distensibility index and pulse pressure variation as dynamic parameters for estimating intravascular volume in critically ill children.

METHODS

Patients aged 1 month to 18 years, who were hospitalized in the present study's pediatric intensive care unit, were included in the study. The patients were divided into two groups according to central venous pressure: hypovolemic (< 8 mmHg) and non-hypovolemic (central venous pressure ≥ 8 mmHg) groups. In both groups, vena cava distensibility index was measured using bedside ultrasound and pulse pressure variation. Measurements were recorded and evaluated under arterial monitoring.

RESULTS

In total, 19 (47.5%) of the 40 subjects included in the study were assigned to the central venous pressure ≥ 8 mmHg group, and 21 (52.5%) to the central venous pressure < 8 mmHg group. A moderate positive correlation was found between pulse pressure variation and vena cava distensibility index (r = 0.475, p < 0.01), while there were strong negative correlations of central venous pressure with pulse pressure variation and vena cava distensibility index (r = -0.628, p < 0.001 and r = -0.760, p < 0.001, respectively). In terms of predicting hypovolemia, the predictive power for vena cava distensibility index was > 16% (sensitivity, 90.5%; specificity, 94.7%) and that for pulse pressure variation was > 14% (sensitivity, 71.4%; specificity, 89.5%).

CONCLUSION

Vena cava distensibility index has higher sensitivity and specificity than pulse pressure variation for estimating intravascular volume, along with the advantage of non-invasive bedside application.

Early Goal-Directed Renal Replacement Therapy in Acute Decompensated Heart Failure Patients with Cardiorenal Syndrome

INTRODUCTION

The aim of this study was to clarify the efficacy of early goal-directed renal replacement therapy (GDRRT) for treatment of cardiorenal syndrome (CRS) patients after acute decompensated heart failure (ADHF).

METHODS

In the retrospective, observational study, we enrolled 54 patients in the early GDRRT group and 63 patients in the late GDRRT group. Baseline characteristics, clinical data at initiation renal replacement therapy time, and the clinical outcome were collected and several parameters were compared and analyzed between 2 groups.

RESULTS

The urine volume at GDRRT initiation time in the early group was higher than that in the late GDRRT group (1,060.3 ± 332.1 vs. 300.5 ± 148.3 mL, p < 0.001). Hemodynamic parameters such as mean artery pressure were higher (70.06 ± 32.99 vs. 54.34 ± 40.88 mm Hg, p = 0.012), the heart rate was slower (80.17 ± 15.26 vs. 99.21 ± 25.45 bpm, p = 0.002), and the diameter of inferior vena cava was narrower (22.00 ± 1.91 vs. 25.77 ± 5.5 mm, p = 0.04) in early GDRRT. Primary end point was inhospital all-cause mortality and cardiovascular mortality, which was obviously lower in the early GDRRT group (respectively 24.1 vs. 60.3%, p = 0.002 and 20.3 vs. 50.8%, p = 0.005). The second end point of kidney recovery in the early GDRRT group was much better than that in the latter GDRRT group (p = 0.018). Moreover, urine volume after GDRRT of the early group was more significant than that of the late group (1,432 ± 172 vs. 702 ± 183 mL, p = 0.005).

CONCLUSION

This study clarified the effectiveness of the early GDRRT strategy in ADHF patients suffered from CRS, which reduced inhospital mortality and improved the urine output and clinical kidney recovery outcome.

Point-of-Care Ultrasound in Acute Care Nephrology

The use of point-of-care ultrasound (POCUS) is rapidly increasing in nephrology. It provides the opportunity to obtain complementary information that is more accurate than the classic physical examination. One can quickly follow the physical examination with a systematic POCUS evaluation of the kidneys, ureter bladder, inferior vena cava, heart, and lungs, which can provide diagnostic information and an accurate assessment of the patient's hemodynamics and volume status. Moreover, because it is safe and relatively easy to perform, it can be performed in a repeated manner as often as necessary so that the physician can reassess the patient's hemodynamics and volume status and adjust their therapy accordingly, permitting a more personalized approach to patient care (rather than blindly following protocols), especially to patients in acute care nephrology. Despite these advantages, nephrologists have been slow to adopt this diagnostic modality, perhaps because of lack of expertise. This review will provide an overview of the most commonly used POCUS examinations performed by nephrologists in the acute care setting. Its aim is to spark interest in in POCUS and to lay the foundation for readers to pursue more advanced training so that POCUS becomes a readily available tool in your diagnostic arsenal.

Diagnosis of Acute Heart Failure Using Inferior Vena Cava Ultrasound: Systematic Review and Meta-analysis

OBJECTIVES

The utility of bedside inferior vena cava (IVC) ultrasound (US) in the diagnosis of heart failure (HF) is unclear. The aim of this study was to determine whether IVC parameters in patients with acute heart failure (AHF) are statistically different from those without HF.

METHODS

The MEDLINE database of English-language publications from 1966 to August 2018 was searched. Retrospective and prospective studies that included either IVC expiratory diameter (IVC_exp ) or IVC collapsibility index (IVC-CI) values were collected in patients with and without HF. to determine whether there was a statistical difference in the IVC parameters between these groups.

RESULTS

A total of 27 articles with a total of 1472 patients with AHF were included. The standard mean differences for the IVC_exp and IVC-CI for the control group versus the AHF group were found to be statistically significant (P < .0001). The combined mean IVC_exp values were 15.11 mm (95% confidence interval [CI], 14.19-16.02 mm) for the control group and 20.26 mm (95% CI, 14.82-25.71 mm) for the AHF group. The combined mean IVC-CI values were 61.6% (95% CI, 48.4%-74.7%) for the control group and 30.5% (95% CI, 26.4%-34.6%) for the AHF group.

CONCLUSIONS

Bedside IVC US showed that a statistically significant difference existed in the IVC parameters between patients with and without AHF. Based on mean calculations, an IVC_exp of greater than 2.0 cm and an IVC-CI of less than 30% are reasonable cutoffs to suggest that a patient with acute dyspnea is more likely to have AHF than a non-AHF condition. Given the high degree of heterogeneity across the studies and the high risk of bias, larger randomized studies are warranted to explore the use of IVC US in patients with HF.

The Cardiorenal Syndrome in Heart Failure

Abnormal fluid handling leads to physiologic abnormalities in multiple organ systems. Deranged hemodynamics, neurohormonal activation, excessive tubular sodium reabsorption, inflammation, oxidative stress, and nephrotoxic medications are important drivers of harmful cardiorenal interactions in patients with heart failure. Accurate quantitative measurement of fluid volume is vital to individualizing therapy for such patients. Blood volume analysis and pulmonary artery pressure monitoring seem the most reliable methods for assessing fluid volume and guiding decongestive therapies. Still the cornerstone of decongestive therapy, diuretics' effectiveness decreases with progression of heart failure. Extracorporeal ultrafiltration, an alternative to diuretics, has been shown to reduce heart-failure events.

Ultrasound-based clinical profiles for predicting the risk of intradialytic hypotension in critically ill patients on intermittent dialysis: a prospective observational study

BACKGROUND

Intradialytic hypotension, a complication of intermittent hemodialysis, decreases the efficacy of dialysis and increases long-term mortality. This study was aimed to determine whether different predialysis ultrasound cardiopulmonary profiles could predict intradialytic hypotension.

METHODS

This prospective observational single-center study was performed in 248 critically ill patients with acute kidney injury undergoing intermittent hemodialysis. Immediately before hemodialysis, vena cava collapsibility was measured by vena cava ultrasound and pulmonary congestion by lung ultrasound. Factors predicting intradialytic hypotension were identified by multiple logistic regression analysis.

RESULTS

Intradialytic hypotension was observed in 31.9% (n = 79) of the patients, interruption of dialysis because of intradialytic hypotension occurred in 6.8% (n = 31) of the sessions, and overall 28-day mortality was 20.1% (n = 50). Patients were classified in four ultrasound profiles: (A) 108 with B lines > 14 and vena cava collapsibility > 11.5 mm m^-2, (B) 38 with B lines < 14 and vena cava collapsibility ≤ 11.5 mm m^-2, (C) 36 with B lines > 14 and vena cava collapsibility Di ≤ 11.5 mm m^-2, and (D) 66 with B lines < 14 and vena cava collapsibility > 11.5 mm m^-2. There was an increased risk of intradialytic hypotension in patients receiving norepinephrine (odds ratios = 15, p = 0.001) and with profiles B (odds ratios = 12, p = 0.001) and C (odds ratios = 17, p = 0.001).

CONCLUSION

In critically ill patients on intermittent hemodialysis, the absence of hypervolemia as assessed by lung and vena cava ultrasound predisposes to intradialytic hypotension and suggests alternative techniques of hemodialysis to provide better hemodynamic stability.

Impact of body characteristics on ultrasound-measured inferior vena cava parameters in Chinese children

Ultrasound-measured inferior vena cava (IVC) and abdominal aorta (Ao)-associated parameters have been used to predict volume status for decades, yet research focusing on the impact of individual physical characteristics, including gender, height/weight, body surface area (BSA), and age, assessed simultaneously on those parameters in Chinese children is lacking. The aim of the present study was to explore the impact of individual characteristics on maximum IVC diameter (IVCmax), Ao, and IVCmax/Ao in healthy Chinese children. From September to December 2015, 200 healthy children from 1 to 13 years of age were enrolled. IVCmax and Ao diameters were measured by 2D ultrasound. We found that age (years), height (cm), weight (kg), waist circumference (cm), and BSA (m²) were positively correlated with IVCmax and Ao. Multivariate linear regression showed that age was the only independent variable for IVCmax (mm) in female children, height was the only independent variable for IVCmax in male children, and age was the only independent variable for Ao in both females and males. IVCmax/Ao was not significantly influenced by the subjects’ characteristics. In conclusion, IVCmax and Ao were more susceptible to subjects’ characteristics than IVCmax/Ao. IVCmax/Ao could be a reliable and practical parameter in Chinese children as it was independent of age, height, and weight.

Relationship of inferior vena cava collapsibility to ultrafiltration volume achieved in critically ill hemodialysis patients

Background

Ultrasound (US) assessment of intravascular volume may improve volume management of dialysis patients. We investigated the relationship of intravascular volume evaluated by inferior vena cava (IVC) US to net volume changes with intermittent hemodialysis (HD) in critically ill patients.

Methods

A retrospective cohort of 113 intensive care unit patients in 244 encounters had clinical assessment of intravascular volume followed by US of respiratory/ventilatory variation of IVC diameter, and had HD within 24 h. IVC collapsibility index (IVC CI)=(IVCmax–IVCmin)/IVCmax*100%. Volume management was guided by clinical data plus IVC US findings. Intradialytic hypotension (IDH) was categorized by severity from none to inability to tolerate HD.

Results

Linear regression correlating n-weighted proportions of encounters achieving net volume removal of ≥0.5 L, ≥1.0 L, ≥1.5 L, and ≥2.0 L strongly correlated across the range of IVC CI (R²=0.87–0.64). Sensitivity and specificity analysis showed IVC CI was a better predictor than IVCmax of achieving net ultrafiltration (UF) volumes. Mean central venous pressure, pulmonary artery occlusion pressure, and cardiac output were poor predictors by logistic regression and receiver operating curve analyses. IVC CI <20% was the approximate optimal cutoff for achieving ≥0.5 L to ≥2.0 L net UF volumes. Net volume change achieved tended to be less than recommended and may have been limited by the development of IDH. Severity of IDH did not correlate with UF rate in mL/kg/h. χ² analysis showed pre-US clinical intravascular volume assessments had poor concordance with IVC CI categories.

Conclusion

IVC US may be a useful tool for predicting whether critically ill patients will achieve volume removal with HD.

Perioperative transesophageal echocardiography for non-cardiac surgery

PURPOSE

The use of transesophageal echocardiography (TEE) has evolved to include patients undergoing high-risk non-cardiac procedures and patients with significant cardiac disease undergoing non-cardiac surgery. Implementation of basic TEE education in training programs has increased across a broad spectrum of procedures in the perioperative arena. This paper describes the use of perioperative TEE in non-cardiac surgery and provides an overview of the basic TEE examination.

PRINCIPAL FINDINGS

Perioperative TEE is used to monitor hemodynamic parameters in non-cardiac procedures where there is a high risk of hemodynamic instability. Its use extends to include moderate-risk procedures for patients with significant cardiac diseases such as low ejection fraction, hypertrophic cardiomyopathy, severe valve lesions, or congenital heart disease. Vascular procedures involving the aorta, blunt trauma, and liver transplantation are all examples of procedures that may benefit from TEE. Transesophageal echocardiography examination allows assessment of volume status, ventricular function, diagnosis of gross valvular pathology and pericardial tamponade, as well as close monitoring of cardiac output, response to therapy, and the impact of ongoing surgical manipulation. In patients with unexplained and unexpected hemodynamic instability, "rescue TEE" can be used to help identify the underlying cause.

CONCLUSIONS

Perioperative TEE is emerging as a preferred tool to manage hemodynamics in high-risk procedures and in high-risk patients undergoing non-cardiac surgery. A rescue TEE examination protocol is a helpful approach for early identification of the etiology of hemodynamic instability.

Clarifications on Continuous Renal Replacement Therapy and Hemodynamics

Objective:

Continuous renal replacement therapy (CRRT) is a continuous process of bedside blood purification which is widely used in the treatment of acute kidney injury (AKI) and for fluid management. However, since AKI and fluid overload are often found to be associated with hemodynamic abnormalities, determining the relationship between CRRT and hemodynamics remains a challenge in the treatment of critically ill patients. The aim of this review was to summarize key points in the relationship between CRRT and hemodynamics and to understand and monitor renal hemodynamics in critically ill patients, especially those with AKI.

Data Sources:

This review was based on data in articles published in the PubMed databases up to January 30, 2017, with the following keywords: “continuous renal replacement therapy,” “Hemodynamics,” and “Acute kidney injury.”

Study Selection:

Original articles and critical reviews on CRRT were selected for this review.

Results:

CRRT might treat AKI by hemodynamic therapy, and it was an important form of hemodynamic therapy. The targets of hemodynamic therapy should be established when using CRRT. Therefore, hemodynamic management and stability were very important during CRRT. Most studies suggested that renal hemodynamics should be clearly identified.

Conclusions:

CRRT is not only a replacement for organ function, but an important form of hemodynamic therapy. Improved hemodynamic management of critically ill patients can be achieved by establishing specific therapeutic hemodynamic targets and maintaining circulatory stability during CRRT. Over the long term, observation of renal hemodynamics will provide greater opportunities for the progression of CRRT hemodynamic therapy.

Predictors to Intravenous Fluid Responsiveness

Management with intravenous fluids can improve cardiac output in some surgical patients. Management with static preload indicators, such as central venous pressure and pulmonary artery occlusion pressure, has not demonstrated a suitable relationship with changes in the cardiac output induced by intravenous fluid therapy. Dynamic indicators, such as the variability of arterial pulse pressure or stroke volume variation, have demonstrated a suitable relationship. Since improvement in cardiac output does not guarantee an adequate perfusion pressure, in patients with hypotension, it is also necessary to know whether arterial pressure will also increase with intravenous fluid therapy. In this regard, the functional assessment of arterial load by dynamic arterial elastance could help to determine which patients will improve not only their cardiac output but also their mean arterial pressure.

Predictors to Intravenous Fluid Responsiveness

Management with intravenous fluids can improve cardiac output in some surgical patients. Management with static preload indicators, such as central venous pressure and pulmonary artery occlusion pressure, has not demonstrated a suitable relationship with changes in the cardiac output induced by intravenous fluid therapy. Dynamic indicators, such as the variability of arterial pulse pressure or stroke volume variation, have demonstrated a suitable relationship. Since improvement in cardiac output does not guarantee an adequate perfusion pressure, in patients with hypotension, it is also necessary to know whether arterial pressure will also increase with intravenous fluid therapy. In this regard, the functional assessment of arterial load by dynamic arterial elastance could help to determine which patients will improve not only their cardiac output but also their mean arterial pressure.

Use of ultrasound by registered nurses-a systematic literature review

BACKGROUND

In Western Australia (WA), most stable patients undergoing haemodialysis receive treatment in a satellite setting where no doctors are on-site during treatment hours, so nurses must make critical decisions about fluid removal. Some patients regularly experience adverse events during dialysis (intradialytic), often due to excessive ultrafiltration goals, with intradialytic hypotension being particularly challenging. Ultrasound of the inferior vena cava has been previously demonstrated being a rapid and non-invasive method for volume assessment on haemodialysis patients, thus could hold valuable information for the treating nurse.

AIM

This paper examines the existing literature in regards to the use of ultrasound measurements of the inferior vena cava in patients on haemodialysis for objective assessment of their intravascular volume status by renal nurses.

METHOD

A systematic literature review was performed within medical and nursing databases including CINAHL Plus with Full Text, SCOPUS, Web of Science and MEDLINE.

RESULTS

Renal nurses are conscious of the significance of intradialytic hypotension and have only limited options for its prevention. Ultrasound of the inferior vena cava could add another objective dimension for intravascular volume assessment and prevention of intradialytic hypotension, but to date renal nurses have not been using this technique.

CONCLUSIONS

Ultrasound of the inferior vena cava has the potential to assist in defining the ultrafiltration goal for that particular dialysis session, thus reducing the risk of intradialytic hypotension. Additionally, it has potential to change current renal nursing practice when added to clinical nursing assessment methods. Further studies are required to validate this assessment tool carried out by a renal nurse compared with a skilled ultrasonographer.

Point-of-care ultrasonography as a training milestone for internal medicine residents: the time is now

Point-of-care (POC) ultrasonography is considered fundamental in emergency medicine training and recently has become a milestone in critical care fellowship programs as well. Currently, there is no such standard requirement for internal medicine residency programs in the United States. We present a new case and briefly review another case at our institution – a community hospital – in which internal medicine house staff trained in ultrasonography were able to uncover unexpected and critical diagnoses that significantly changed patient care and outcomes. We also review the growing evidence of the application of ultrasound in the diagnosis of a myriad of conditions encountered in general internal medicine as well as the mounting data on the ability of internal medicine residents to apply this technology accurately at the bedside. We advocate that the literature has sufficiently established the role of POC ultrasonography in general internal medicine that there should no longer be any delay in giving this an official place in the development of internal medicine trainees. This may be particularly useful in the community hospital setting where 24-h echocardiography or other sonography may not be readily available.

Ultrasonographic caval indices do not significantly contribute to predicting fluid responsiveness immediately after coronary artery bypass grafting when compared to passive leg raising

Background

Appropriate fluid management is one of the most important elements of early goal-directed therapy after cardiothoracic surgery. Reliable determination of fluid responsivenss remains the fundamental issue in volume therapy.

The purpose of the study was to assess the usefulness of dynamic IVC-derived parameters (collapsibility index, distensibility index) in comparison to passive leg raising, in postoperative fluid management in mechanically ventilated patients with left ventricular ejection fraction ≥ 30 %, immediately after elective coronary artery bypass grafting.

Methods

Prospective observational case series study including 35 patients with LVEF ≥ 30 %, undergoingelective coronary artery bypass grafting was conducted. Transthoracic echocardiography, passive leg raising and intravenous administration of saline were performed in all study subjects. Dynamic parameters derived from ultrasonographic assessment of the IVC diameter (collapsibility index–CI and distensibility index–DI), cardiac output

Results

There were 24 (68.57 %) responders in the study population. There were no statistical differences between the groups in relation to: clinical parameters, pre- and postoperative LVEF, fluid balance and CVP. Change in cardiac output after passive leg raising correlated significantly with that after the volume expansion (p=0.000, r=0.822). Dynamic IVC derivatives were slightly higher in fluid responders, however this trend did not reach statistical significance. None of the caval indices correlated with fluid responsiveness.

Conclusion

Dynamic IVC-derived parameters do not predict fluid responsiveness in mechanically ventilated patients with preserved ejection fraction immediately after elective coronary artery bypass grafting. Passive leg raising is not inferior to volume expansion in differentiating between fluid responders and nonresponders. Immediate fluid challenge after CABG is safe and well tolerated.

Electronic supplementary material

The online version of this article (doi:10.1186/s12947-016-0065-4) contains supplementary material, which is available to authorized users.

Influence of Diaphragmatic Motion on Inferior Vena Cava Diameter Respiratory Variations in Healthy Volunteers

BACKGROUND

The collapsibility index of inferior vena cava (cIVC) is widely used to decide fluid infusion in spontaneously breathing intensive care unit patients. The authors hypothesized that high inspiratory efforts may induce false-positive high cIVC values. This study aims at determining a value of diaphragmatic motion recorded by echography that could predict a high cIVC (more than or equal to 40%) in healthy volunteers.

METHODS

The cIVC and diaphragmatic motions were recorded for three levels of inspiratory efforts. Right and left diaphragmatic motions were defined as the maximal diaphragmatic excursions. Receiver operating characteristic curves evaluated the performance of right diaphragmatic motion to predict a cIVC more than or equal to 40% defining the best cutoff value.

RESULTS

Among 52 included volunteers, interobserver reproducibility showed a generalized concordance correlation coefficient (ρc) above 0.9 for all echographic parameters. Right diaphragmatic motion correlated with cIVC (r = 0.64, P < 0.0001). Univariate analyses did not show association between cIVC and age, sex, weight, height, or body mass index. The area under the receiver operating characteristic curves for cIVC more than or equal to 40% was 0.87 (95% CI, 0.81 to 0.93). The best diaphragmatic motion cutoff was 28 mm (Youden Index, 0.65) with sensitivity of 89% and specificity of 77%. The gray zone area was 25 to 43 mm.

CONCLUSIONS

Inferior vena cava collapsibility is affected by diaphragmatic motion. During low inspiratory effort, diaphragmatic motion was less than 25 mm and predicted a cIVC less than 40%. During maximal inspiratory effort, diaphragmatic motion was more than 43 mm and predicted a cIVC more than 40%. When diaphragmatic motion ranged from 25 to 43 mm, no conclusion on cIVC value could be done.

[Prognostic value of measuring the diameter and inspiratory collapse of the inferior vena cava in acute heart failure]

OBJECTIVES

To assess the utility of measuring the diameter and collapse of the inferior vena cava (IVC) in acute heart failure (AHF), its relationship with the prognosis and serum biomarkers of congestion.

PATIENTS AND METHODS

An observational prospective study was conducted that included 85 patients with AHF, classifying them into 4 groups according to IVC diameter (≤ or >20mm) and inspiratory collapse (< or ≥50%) at admission. The endpoints were mortality due to HF and the combined event of mortality and readmission for HF at 180 days.

RESULTS

Some 24.7% of the patients had an undilated IVC and ≥50% collapse (group 1); 20% had an undilated IVC and <50% collapse (group 2), 5.9% had a dilated IVC and ≥50% collapse (group 3); and 49.4% had a dilated IVC and <50% collapse (group 4). The lack of inspiratory collapse but not IVC dilation was related to higher concentrations of urea (P=.007), creatinine (P=.004), uric acid (P=.008), NT-proBNP (P=.009) and CA125 (P=.005). Survival free of the combined event at 180 days was lower in those patients with no IVC collapse.

CONCLUSIONS

Dilation and the absence of the inspiratory collapse of the IVC are common in the context of AHF. The lack of inspiratory collapse of the IVC during the decompensation phase identifies a subgroup of patients with poorer prognosis at 6 months.

Inferior vena cava collapsibility loses correlation with internal jugular vein collapsibility during increased thoracic or intra-abdominal pressure

PURPOSE

Point-of-care ultrasound evaluates inferior vena cava (IVC) and internal jugular vein (IJV) measurements to estimate intravascular volume status. The reliability of the IVC and IJV collapsibility index during increased thoracic or intra-abdominal pressure remains unclear.

METHODS

Three phases of sonographic scanning were performed: spontaneous breathing phase, increased thoracic pressure phase via positive pressure ventilation (PPV) phase, and increased intra-abdominal pressure (IAP) phase via laparoscopic insufflation to 15 mmHg. IVC measurements were done at 1-2 cm below the diaphragm and IJV measurements were done at the level of the cricoid cartilage during a complete respiratory cycle. Collapsibility index was calculated by (max diameter - min diameter)/max diameter × 100 %. Chi square, t test, correlation procedure (CORR) and Fisher's exact analyses were completed.

RESULTS

A total of 144 scans of the IVC and IJV were completed in 16 patients who underwent laparoscopic surgery. Mean age was 46 ± 15 years, with 75 % female and 69 % African-American. IVC and IJV collapsibility correlated in the setting of spontaneous breathing (r (2) = 0.86, p < 0.01). IVC collapsibility had no correlation with the IJV in the setting of PPV (r (2) = 0.21, p = 0.52) or IAP (r (2) = 0.26, p = 0.42). Maximal IVC diameter was significantly smaller during increased IAP (16.5 mm ± 4.9) compared to spontaneous breathing (20.6 mm ± 4.8, p = 0.04) and PPV (21.8 mm ± 5.6, p = 0.01).

CONCLUSION

IJV and IVC collapsibility correlated during spontaneous breathing but there was no statistically significant correlation during increased thoracic or intra-abdominal pressure. Increased intra-abdominal pressure was associated with a significant smaller maximal IVC diameter and cautions the reliability of IVC diameter in clinical settings that are associated with intra-abdominal hypertension or abdominal compartment syndrome.

Inferior Vena Cava and Hemodynamic Congestion

BACKGROUND

Among the indices able to replace invasive central venous pressure (CVP) measurement for patients with acute decompensated heart failure (ADHF) the diameters of the inferior vena cava (IVC) and their respiratory fluctuations, so-called IVC collapsibility index (IVCCI), measured by echocardiography, have recently gained ground as a quite reliable proxy of CVP.

OBJECTIVES

The aims of our study were to compare three different ways of evaluating cardiac overload by using the IVC diameters and/or respiratory fluctuations and by calculating the inter-method agreement.

PATIENTS AND METHODS

Medical records of patients hospitalized for right or bi-ventricular acute decompensated heart failure from January to December 2013 were retrospectively evaluated. The predictive significance of the IVC expiratory diameter and IVC collapsibility index (IVCCI) was analyzed using three different methods, namely a) the criteria for the indirect estimate of right atrial pressure by Rudski et al. (J Am Soc Echocardiogr. 2010); b) the categorization into three IVCCI classes by Stawicki et al. (J Am Coll Surg. 2009); and c) the subdivision based on the value of the maximum IVC diameter by Pellicori et al. (JACC Cardiovasc Imaging. 2013).

RESULTS

Among forty-seven enrolled patients, those classified as affected by persistent congestion were 22 (46.8%) using Rudski's criteria, or 16 (34%) using Stawicki's criteria, or 13 (27.6%) using Pellicori's criteria. The inter-rater agreement was rather poor by comparing Rudski's criteria with those of Stawicki (Cohen's kappa = 0.369; 95% CI 0.197 to 0.54), as well as by comparing Rudski's criteria with those of Pellicori (Cohen's kappa = 0.299; 95% CI 0.135 to 0.462). Further, a substantially unsatisfactory concordance was also found for Stawicki's criteria compared to those of Pellicori (Cohen's kappa= 0.468; 95% CI 0.187 to 0.75).

CONCLUSIONS

The abovementioned IVC ultrasonographic criteria for hemodynamic congestion appear clearly inconsistent. Alternatively, a sequential or simultaneous combination of clinical scores of congestion, IVC ultrasonographic indices, and circulating levels of natriuretic peptides could be warranted.

Interrater agreement between expert and novice in measuring inferior vena cava diameter and collapsibility index

BACKGROUND

In critical care medicine, US views of the inferior vena cava (IVC) and its change with respiration are used to estimate the intravascular volume status of unwell patients and, in particular, to answer the question: 'Is this patient likely to be fluid responsive?' Most commonly in the literature, the subxiphisternal (SX) window in the longitudinal plane is utilised. To date, no study has specifically assessed interrater agreement in estimating IVC diameter between emergency medicine specialists (experts) and trainees (learners).

OBJECTIVES

To determine the interrater agreement between an expert (senior emergency specialist with US qualifications) and learner (emergency medicine trainee) when measuring IVC diameter (IVCD) and IVC collapsibility index (IVCCI) in the SX longitudinal US window in healthy volunteers.

METHODS

Healthy volunteers (ED staff) were scanned in the supine position using a sector (cardiac) probe of a portable US machine, in the SX longitudinal position. The maximum and minimum diameters of the IVC were measured in each of these positions and the IVCCI calculated. Results were analysed using Bland-Altman plots.

RESULTS

In the longitudinal SX window, the operators' measurements of maximum IVCD differed by an average of 1.9 mm (95% limits of agreement -9.4 mm to +5.5 mm) and their measurement of IVCCI differed by an average of 4% (95% limits of agreement -30% to 38%).

CONCLUSIONS

The wide 95% limits of agreement demonstrate a poor interrater agreement between the IVC US measurements obtained by expert and learner users in the assessment of fluid status. These ranges are greater than clinically acceptable.

Diagnostic point-of-care ultrasound for hospitalists

We review the literature on diagnostic point-of-care ultrasound applications most relevant to hospital medicine and highlight gaps in the evidence base. Diagnostic point-of-care applications most relevant to hospitalists include cardiac ultrasound for left ventricular systolic function, pericardial effusion, and severe mitral regurgitation; lung ultrasound for pneumonia, pleural effusion, pneumothorax, and pulmonary edema; abdominal ultrasound for ascites, aortic aneurysm, and hydronephrosis; and venous ultrasound for central venous volume assessment and lower extremity deep venous thrombosis. Hospitalists and other frontline providers, as well as physician trainees at various levels of training, have moderate to excellent diagnostic accuracy after brief training programs for most of these applications. Despite the evidence supporting the diagnostic accuracy of point-of-care ultrasound, experimental evidence supporting its clinical use by hospitalists is limited to cardiac ultrasound.

Bedside ultrasonographic measurement of the inferior vena cava fails to predict fluid responsiveness in the first 6 hours after cardiac surgery: a prospective case series observational study

OBJECTIVE

To assess validity of respiratory variation of inferior vena cava (IVC) diameter to predict fluid responsiveness and guide fluid therapy in mechanically ventilated patients during the first 6 hours after elective cardiac surgery.

DESIGN

Prospective observational case series study.

SETTING

Single-center hospital.

PATIENTS

50 consecutive patients undergoing elective cardiac surgery.

INTERVENTIONS

Transthoracic bedside echocardiography.

MEASUREMENTS AND MAIN RESULTS

Parameters derived from ultrasonographic assessment of the IVC diameter (collapsibility index [CI], distensibility index [DI], and IVC/aorta index). In the whole study group, change in fluid balance correlated with change in IVC maximum diameter (p = 0.034, r = 0.176). IVC-CI and IVC-DI correlated with IVC/aorta index. A weak correlation between central venous pressure (CVP) and IVC-derived parameters (IVC-CI and IVC-DI) was noticed. Despite statistical significance (p<0.05), all observed correlations expressed low statistical power (r<0.21). There were no statistically significant differences between fluid responders and nonresponders in relation to clinical parameters, CVP, ultrasound IVC measurement, and IVC-derived indices.

CONCLUSION

Dynamic IVC-derived parameters (IVC-CI, IVC-DI, and IVC/aorta index) and CVP are not reliable predictors of fluid responsiveness in the first 6 hours after cardiac surgery. Complexity of physiologic factors modulating cardiac performance in this group may be responsible for the difficulty in finding a plausible monitoring tool for fluid guidance. Bedside ultrasonographic measurement of IVC is unable to predict fluid responsiveness in the first 6 hours after cardiac surgery.

The caval index: an adequate non-invasive ultrasound parameter to predict fluid responsiveness in the emergency department?

Background

Fluid therapy is the first important step in patients with signs of shock but assessment of the volume status is difficult and invasive measurements are not readily available in the emergency department. We have investigated whether the respiratory variation in diameter of the inferior vena cava is a reliable parameter to predict fluid responsiveness in spontaneous breathing emergency department patients with signs of shock.

Methods

All patients admitted to the emergency department during a 15 week period were screened for signs of shock. If the attending physician planned to give a fluid challenge, the caval index was determined by transabdominal ultrasonography in supine position. Immediately afterwards 500 ml NaCl 0.9% was administered in 15 minutes and the clinical response was observed. An adequate response was defined as an increase in systolic blood pressure of at least 10 mm Hg. Based on this definition patients were divided into responders and non-responders.

Results

After selection a total number of 45 patients was included. A low caval index (< 36.5%) in patients with signs of shock reliably predicted the absence of an adequate response to fluid therapy (negative predictive value 92%). The positive predictive value of a high caval index was much lower (48%) despite the fact that responders had a significantly higher pre-infusion caval index than non-responders (48.7% vs 31.8%, p 0.014).

Conclusions

In spontaneously breathing patients with signs of shock in the emergency department, a high caval index (>36.5%) does not reliably predict fluid responsiveness in our study, while a low caval index (<36.5%) makes fluid responsiveness unlikely. An explanation for the absence of a blood pressure response in the group of patients with a low high caval index might be that these patients represent a group requiring more volume therapy than 500 ml.

Preoperative fasting does not affect haemodynamic status: a prospective, non-inferiority, echocardiography study

BACKGROUND

The link between preoperative fasting and hypovolaemia remains unclear. We tested the hypothesis that preoperative fasting does not significantly increase the proportion of patients with hypovolaemia according to transthoracic echocardiography (TTE) criteria.

METHODS

Patients of ASA status I-III and without bowel preparation were included in a non-inferiority, prospective, single-centre trial. Patients underwent passive leg raising (PLR) test and TTE at admission (Day 0) and after 8 h fasting (Day 1). The primary hypothesis was that an 8 h preoperative fasting does not increase the proportion (margin=5%) of patients with a positive PLR test ('functional approach'). The secondary hypothesis was that echocardiographic filling pressures or stroke volume (margin 10%) are not affected by preoperative fasting ('static approach').

RESULTS

One hundred patients were included and 98 analysed. After an 8 h fasting, the change in the proportion of responders to PLR was -6.1% [95% confidence interval (CI)=-16.0 to 3.8] of responders to PLR test on Day 0 when compared with Day 1. Because 95% CI was strictly inferior to 5%, there was no significant increase in the proportion of PLR responders on Day 1 when compared with Day 0. The 95% CI changes of static variables were always fewer than 10%, meaning that preoperative fasting induced significantly no relevant changes in static variables.

CONCLUSION

Preoperative fasting did not alter TTE dynamic and static preload indices in ASA I-III adult patients. These results suggest that preoperative fasting does not induce significant hypovolaemia. Clinical trial registration NCT 01258361.

The gray zone of the qualitative assessment of respiratory changes in inferior vena cava diameter in ICU patients

Introduction

Transthoracic echocardiography (TTE) is a useful tool for minimally invasive hemodynamic monitoring in the ICU. Dynamic indices (such as the inferior vena cava distensibility index (dIVC)) can be used to predict fluid responsiveness in mechanically ventilated patients. Although quantitative use of the dIVC has been validated, the routinely used qualitative (visual) approach had not been assessed before the present study.

Methods

Qualitative and quantitative assessments of the dIVC were compared in a prospective, observational study. After operators with differing levels in critical care echocardiography had derived a qualitative dIVC, the last (expert) operator performed a standard, numeric measurement of the dIVC (referred to as the quantitative dIVC). Two groups of patients were separated into two groups: group (dIVC < 18%) and group (dIVC ≥ 18%).

Results

In total, 114 patients were assessed for inclusion, and 97 (63 men and 34 women) were included. The mean sensitivity and specificity values for qualitative assessment of the dIVC by an intensivist were 80.7% and 93.7%, respectively. A qualitative evaluation detected all quantitative dIVCs >40%. Most of the errors concerned quantitative dIVCs of between 15% and 30%. In the dIVC <18% group, two qualitative evaluation errors were noted for quantitative dIVCs of between 0 and 10%. The average of positive predictive values and negative predictive values for qualitative assessment of the dIVC by residents, intensivists and cardiologists were 83%, 83%, and 90%; and 92%, 94%, and 90%, respectively. The Fleiss kappa for all operators was estimated to be 0.68, corresponding to substantial agreement.

Conclusion

The qualitative dIVC is a rather easy and reliable assessment for extreme numeric values. It has a gray zone between 15% and 30%. The highest and lowest limitations of the gray area are rather tedious to define.

Despite reliability of the qualitative assessment when it comes to extreme to numerical values, the quantitative dIVC measurement must always be done within a hemodynamic assessment for intensive care patients. The qualitative approach can be easily integrated into a fast hemodynamic evaluation by using portable ultrasound scanner for out-of-hospital patients.

Hospitalists' ability to use hand-carried ultrasound for central venous pressure estimation after a brief training intervention: a pilot study

BACKGROUND

Access to hand-carried ultrasound technology for noncardiologists has increased significantly, yet development and evaluation of training programs are limited.

OBJECTIVE

We studied a focused program to teach hospitalists image acquisition of inferior vena cava (IVC) diameter and IVC collapsibility index with interpretation of estimated central venous pressure (CVP).

METHODS

Ten hospitalists completed an online educational module prior to attending a 1-day in-person training session that included directly supervised IVC imaging on volunteer subjects. In addition to making quantitative assessments, hospitalists were also asked to visually assess whether the IVC collapsed more than 50% during rapid inspiration or a sniff maneuver. Skills in image acquisition and interpretation were assessed immediately after training on volunteer patients and prerecorded images, and again on volunteer patients at least 6 weeks later.

RESULTS

Eight of 10 hospitalists acquired adequate IVC images and interpreted them correctly on 5 of the 5 volunteer subjects and interpreted all 10 prerecorded images correctly at the end of the 1-day training session. At 7.4 ± 0.7 weeks (range, 6.9-8.6 weeks) follow-up, 9 of 10 hospitalists accurately acquired and interpreted all IVC images in 5 of 5 volunteers. Hospitalists were also able to accurately determine whether the IVC collapsibility index was more than 50% by visual assessment in 180 of 198 attempts (91% of the time).

CONCLUSIONS

After a brief training program, hospitalists acquired adequate skills to perform and interpret hand-carried ultrasound IVC images and retained these skills in the near term. Though calculation of the IVC collapsibility index is more accurate, coupling a qualitative assessment with the IVC maximum diameter measurement may be acceptable in aiding bedside estimation of CVP.

Respiratory variations of inferior vena cava diameter to predict fluid responsiveness in spontaneously breathing patients with acute circulatory failure: need for a cautious use

INTRODUCTION

To investigate whether respiratory variation of inferior vena cava diameter (cIVC) predict fluid responsiveness in spontaneously breathing patients with acute circulatory failure (ACF).

METHODS

Forty patients with ACF and spontaneous breathing were included. Response to fluid challenge was defined as a 15% increase of subaortic velocity time index (VTI) measured by transthoracic echocardiography. Inferior vena cava diameters were recorded by a subcostal view using M Mode. The cIVC was calculated as follows: (Dmax - Dmin/Dmax) × 100 and then receiver operating characteristic (ROC) curves were generated for cIVC, baseline VTI, E wave velocity, E/A and E/Ea ratios.

RESULTS

Among 40 included patients, 20 (50%) were responders (R). The causes of ACF were sepsis (n = 24), haemorrhage (n = 11), and dehydration (n = 5). The area under the ROC curve for cIVC was 0.77 (95% CI: 0.60-0.88). The best cutoff value was 40% (Se = 70%, Sp = 80%). The AUC of the ROC curves for baseline E wave velocity, VTI, E/A ratio, E/Ea ratio were 0.83 (95% CI: 0.68-0.93), 0.78 (95% CI: 0.61-0.88), 0.76 (95% CI: 0.59-0.89), 0.58 (95% CI: 0.41-0.75), respectively. The differences between AUC the ROC curves for cIVC and baseline E wave velocity, baseline VTI, baseline E/A ratio, and baseline E/Ea ratio were not statistically different (p = 0.46, p = 0.99, p = 1.00, p = 0.26, respectively).

CONCLUSION

In spontaneously breathing patients with ACF, high cIVC values (>40%) are usually associated with fluid responsiveness while low values (< 40%) do not exclude fluid responsiveness.

Qualitative Assessment of the Inferior Vena Cava: Useful Tool for the Evaluation of Fluid Status in Critically Ill Patients

Inferior vena cava (IVC) diameter change on limited transthoracic echocardiogram (LTTE) can provide a useful guide of fluid status evaluation in critically ill patients. Institutional review board approval was obtained. Prospective evaluation of hemodynamic status was performed in hypotensive patients via LTTE. Images were obtained using an ultrasound machine without M-mode capability. Qualitative assessment of the IVC was obtained via subxyphoid window. FLAT IVC was defined as diameter less than 2 cm and FAT IVC when the vein was equal or larger than 2 cm. Collapsibility was assessed by observing respiratory variation of the vessel. Lactate was measured before and after therapy was initiated. A follow-up LTTE was obtained after fluid challenge. A total of 108 LTTE were performed. Patients’ age ranged from 18 to 89 years with an average of 53. Admission diagnosis was blunt trauma in 66 patients, penetrating trauma in 17, whereas 25 had nontraumatic intra-abdominal emergency. Sixty-nine patients were receiving mechanical ventilation at time of LTTE. Seventy-three patients had a FLAT IVC, and received fluid challenge as therapy. All patients had a change in IVC volume from “FLAT” to “FAT” after the fluid challenge. Seventy-one patients (97%) had resolution of hypotension after the first fluid challenge. Two patients had persistent hypotension and received a second fluid challenge. Follow-up LTTE demonstrated a FAT IVC and lack of collapsibility. Lactate decreased in all 73 patients after therapy guided by LTTE ( P < 0.00001) Evaluation of the IVC diameter via LTTE offers a rapid, non invasive way to evaluate fluid status in critically ill patients.

Hemodynamic monitoring in the critically ill: spanning the range of kidney function

Critically ill patients often have deranged hemodynamics. Physical examination, central venous pressure, and pulmonary artery occlusion pressure ("wedge") have been shown to be unreliable at assessing volume status, volume responsiveness, and adequacy of cardiac output in critically ill patients. Thus, invasive and noninvasive cardiac output monitoring is a core feature of evaluating and managing a hemodynamically unstable patient. In this review, we discuss the various techniques and options of cardiac output assessment available to clinicians for hemodynamic monitoring in the intensive care unit. Issues related to patients with kidney disease, such as timing and location of arterial and central venous catheters and the approach to hemodynamics in patients treated by long-term dialysis also are discussed.

Limited transthoracic echocardiogram: so easy any trauma attending can do it

BACKGROUND

Limited transthoracic echocardiogram (LTTE) represents an attractive alternative to formal transthoracic echocardiogram (TTE), because it does not require an echocardiogram machine. Our hypothesis is that trauma attendings can learn LTTE effectively with minimal training.

METHODS

Seven attendings at a Level I trauma center received didactic and hands-on training in LTTE and performed this test on hypotensive patients to evaluate for contractility, fluid status, and pericardial effusion. Therapy to improve perfusion (administration of fluids, ionotropes, or vasopressors) was guided by LTTE findings. Perfusion status was determined by serum lactate level before and 6 hours after LTTE. Findings were compared with cardiology-performed TTE.

RESULTS

Range of postresidency training was 1 year to 29 years. LTTE teaching entailed 70 minutes of didactics and 25 minutes of hands-on. In all, 52 LTTEs were performed; two patients were excluded due to blunt trauma arrest. Age ranged from 22 years to 89 years with an average of 55 years. Admission diagnosis was blunt trauma (n = 34), penetrating trauma (n = 3), and intra-abdominal sepsis (n = 13). Average time for LTTE was 4 minutes 38 seconds. Cardiology-performed TTE was obtained in all patients, and correlation with LTTE was 100%. A total of 37 patients received intravenous fluid, 9 received vasopressors, and 4 received ionotropes as guided by LTTE findings, with lactate reduction in all patients (p < 0.00001). Attendings scored a mean of 88% in a written test after training.

CONCLUSIONS

Trauma attendings can successfully learn LTTE with minimal training and use the technique as a resuscitation tool in the hypotensive patient.

Inferior vena cava assessment in the bedside diagnosis of acute heart failure

OBJECTIVES

The objective of this study was to determine the test characteristics of the caval index and caval-aortic ratio in predicting the diagnosis of acute heart failure in patients with undifferentiated dyspnea in the emergency department (ED).

METHODS

This prospective observational study was performed at an urban ED that enrolled patients, 50 years or older, with acute dyspnea. A sonographic caval index was calculated as the percentage decrease in the inferior vena cava (IVC) diameter during respiration. A caval-aortic ratio was defined by the maximum IVC diameter divided by the aortic diameter. The sensitivity, specificity, and likelihood ratios of these measurements associated with heart failure were estimated.

RESULTS

Eighty-nine patients were enrolled in the study with a mean age of 68 years. A caval index of less than 33% had 80% sensitivity (95% confidence interval [CI], 63%-91%) and 81% specificity (95% CI, 68%-90%) in diagnosing acute heart failure, whereas an index of less than 15% had a 37% sensitivity (95% CI, 22%-55%) and 96% specificity (95% CI, 86%-99%). The sensitivity of a caval-aortic ratio of more than 1.2 was 33% (95% CI, 18%-52%) and the specificity was 96% (95% CI, 86%-99%). Positive likelihood ratios were 10 for a caval index of less than 15%, 4.3 for an index of less than 33%, and 8.3 for a caval-aortic ratio of more than 1.2.

CONCLUSION

Bedside assessments of the caval index or caval-aortic ratio may be useful clinical adjuncts in establishing the diagnosis of acute heart failure in patients with undifferentiated dyspnea.

Correlation between IVC dimensions and volume status on CT scan

BACKGROUND

End points of resuscitation in trauma patients are difficult to define. The size of the inferior vena cava (IVC) on CT scan may accurately indicate volume status and guide resuscitation efforts. Our hypothesis was that IVC "flatness" on CT scan reflects volume status in hemodynamically normal trauma patients.

METHODS

The study population was drawn from a database of trauma patients who had abdominal CT scans and lactate levels drawn on arrival. Lactate was chosen as a marker of volume status since hypotensive patients were unlikely to undergo CT. Anteroposterior (AP) and transverse (TV) diameters of the IVC were measured at the suprarenal and infrarenal locations. A flatness index was calculated for each location (TV ÷ AP) and this value was correlated with heart rate, blood pressure, and lactate.

RESULTS

There was no difference in IVC flatness at the suprarenal or infrarenal position for patients with an elevated lactate compared with those with a normal lactate: 1.54 ± 0.18 versus 1.43 ± 0.08 (P = 0.2) suprarenal and 1.54 ± 0.46 versus 1.68 ± 0.58 (P = 0.4) infrarenal. IVC flatness at the suprarenal location weakly correlated with blood pressure (r = -0.29). IVC flatness did not correlate with blood pressure at the infrarenal location (r = -0.1). IVC flatness did not correlate with heart rate (P > 0.3) or age (P > 0.2).

CONCLUSION

These results did not demonstrate a correlation between IVC flatness and the markers of intravascular volume of heart rate, blood pressure, or lactate. IVC flatness on CT scan is not a valid indicator of volume status in hemodynamically normal trauma patients.

Transthoracic focused rapid echocardiographic examination: real-time evaluation of fluid status in critically ill trauma patients

BACKGROUND

A transthoracic focused rapid echocardiographic evaluation (FREE) was developed to answer specific questions about treatment direction regarding the use of fluid versus ionotropes in trauma patients. Our objective was to evaluate the clinical utility of the information obtained by this diagnostic test.

METHODS

The FREE was performed by an ultrasonographer or an intensivist and interpreted by a surgical intensivist using a full service portable echo machine (Vivid i; GE Healthcare). The clinical team ordering the examination was surveyed before and after the test was performed.

RESULTS

During a 9-month study period, the FREE was performed in 53 patients admitted to our trauma critical care units. In 80% of patients, an estimated ejection fraction was obtained. Moderate and severe left ventricular dysfunction was diagnosed in 56% of patients, and right heart dysfunction was found in 25% of the patients. Inferior vena cava (IVC) diameter and IVC respiratory variation was visualized in 80% of patients. In 87% (46 of 53), the FREE was able to answer the clinical question asked by the primary team. Strikingly, in 54% of patients, the plan of care was modified as a result of the FREE examination.

CONCLUSIONS

IVC diameter and IVC respiratory variation was able to be obtained in the majority of cases, giving an estimate of fluid status. Estimation of ejection fraction was useful in guiding the treatment plan regarding the requirement of fluid boluses versus ionotropic support. We conclude that the FREE can provide meaningful data in difficult to image critically ill trauma patients.