Bedside sonographic measurement of the inferior vena cava caval index is a poor predictor of fluid responsiveness in emergency department patients

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.

[Hemodynamic monitoring of critically ill patients : Bedside integration of data]

BACKGROUND

Hemodynamic monitoring of critically ill patients is a key issue in intensive care medicine. Indication and application of invasive hemodynamic monitoring is a highly complex matter and requires thorough professional education and training.

MATERIALS AND METHODS

A literature review was performed.

RESULTS

A pragmatic approach can be divided into several steps such as medical history, physical examination, imaging, and laboratory results, which support the primary working diagnosis and allow further clarification of the underlying pathophysiology. Invasive arterial blood pressure and cardiac output measurement as well as components of the functional hemodynamic monitoring help to assess fluid responsiveness and to guide volume loading, diuretic therapy as well as administration of vasoactive or positive inotrope substances.

CONCLUSIONS

All information gathered through medical history, physical examination, imaging, and hemodynamic monitoring help to form an overall picture and should be reevaluated regularly and in individual cases very closely depending on the hemodynamic instability of the patient. Target values are strictly indicative and are not binding taking into account that each patient has its unique pathophysiological profile.

Optimizing the value of measuring inferior vena cava diameter in shocked patients

Point-of-care ultrasound has been increasingly used in evaluating shocked patients including the measurement of inferior vena cava (IVC) diameter. Operators should standardize their technique in scanning IVC. Relative changes are more important than absolute numbers. We advise using the longitudinal view (B mode) to evaluate the gross collapsibility, and the M mode to measure the IVC diameter. Combining the collapsibility and diameter size will increase the value of IVC measurement. This approach has been very useful in the resuscitation of shocked patients, monitoring their fluid demands, and predicting recurrence of shock. Pitfalls in measuring IVC diameter include increased intra-thoracic pressure by mechanical ventilation or increased right atrial pressure by pulmonary embolism or heart failure. The IVC diameter is not useful in cases of increased intra-abdominal pressure (abdominal compartment syndrome) or direct pressure on the IVC. The IVC diameter should be combined with focused echocardiography and correlated with the clinical picture as a whole to be useful.

Assessment of volume status and fluid responsiveness in the emergency department: a systematic approach

When treating acutely ill patients in the emergency department (ED), the successful management of a variety of medical conditions, such as sepsis, acute kidney injury, and pancreatitis, is highly dependent on the correct assessment and optimization of a patient's intravascular volume status. Therefore, it is crucial that the ED physician knows and uses available means to assess intravascular volume status to adequately guide fluid therapy. This review focuses on techniques for volume status assessment that are available in the ED including basic clinical and laboratory findings, apparatus-based tests such as sonography and chest x-ray, and functional tests to evaluate fluid responsiveness. Furthermore, we provide an outlook on promising innovative, noninvasive technologies that might be used for advanced hemodynamic monitoring in the ED.

A rational approach to fluid therapy in sepsis

Aggressive fluid resuscitation to achieve a central venous pressure (CVP) greater than 8 mm Hg has been promoted as the standard of care, in the management of patients with severe sepsis and septic shock. However recent clinical trials have demonstrated that this approach does not improve the outcome of patients with severe sepsis and septic shock. Pathophysiologically, sepsis is characterized by vasoplegia with loss of arterial tone, venodilation with sequestration of blood in the unstressed blood compartment and changes in ventricular function with reduced compliance and reduced preload responsiveness. These data suggest that sepsis is primarily not a volume-depleted state and recent evidence demonstrates that most septic patients are poorly responsive to fluids. Furthermore, almost all of the administered fluid is sequestered in the tissues, resulting in severe oedema in vital organs and, thereby, increasing the risk of organ dysfunction. These data suggest that a physiologic, haemodynamically guided conservative approach to fluid therapy in patients with sepsis would be prudent and would likely reduce the morbidity and improve the outcome of this disease.

Inferior Vena Cava Assessment: Correlation with CVP and Plethora in Tamponade

Bedside assessment of intravascular volume status plays an important role in the management of critically ill patients, guiding fluid replacement therapy and the use of vasopressor agents. Despite controversy in the existing evidence, many clinicians advocate the use of inferior vena cava ultrasound (IVC-US) in the assessment of intravascular volume status in critically ill patients. Respirophasic variation in IVC diameter may provide useful information regarding intravascular volume status, particularly in patients with high and low caval indices. However, due to conflicting results of small-scale clinical trials of divergent sample populations, there is insufficient evidence to support routine US assessment of the IVC to determine fluid responsiveness in spontaneous breathing with circulatory compromise. Additional large-scale clinical trials are required to determine the accuracy of IVC-US measurements in diverse populations and to ascertain the effects on IVC dimensions that result from cardiac dysfunction and intra-abdominal hypertension.

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.

Can emergency physicians perform common carotid Doppler flow measurements to assess volume responsiveness?

Introduction

Common carotid flow measurements may be clinically useful to determine volume responsiveness. The objective of this study was to assess the ability of emergency physicians (EP) to obtain sonographic images and measurements of the common carotid artery velocity time integral (VTi) for potential use in assessing volume responsiveness in the clinical setting.

Methods

In this prospective observational study, we showed a five-minute instructional video demonstrating a technique to obtain common carotid ultrasound images and measure the common carotid VTi to emergency medicine (EM) residents. Participants were then asked to image the common carotid artery and obtain VTi measurements. Expert sonographers observed participants imaging in real time and recorded their performance on nine performance measures. An expert sonographer graded image quality. Participants were timed and answered questions regarding ease of examination and their confidence in obtaining the images.

Results

A total of 30 EM residents participated in this study and each performed the examination twice. Average time required to complete one examination was 2.9 minutes (95% CI [2.4–3.4 min]). Participants successfully completed all performance measures greater than 75% of the time, with the exception of obtaining measurements during systole, which was completed in 65% of examinations. Median resident overall confidence in accurately performing carotid VTi measurements was 3 (on a scale of 1 [not confident] to 5 [confident]).

Conclusion

EM residents at our institution learned the technique for obtaining common carotid artery Doppler flow measurements after viewing a brief instructional video. When assessed at performing this examination, they completed several performance measures with greater than 75% success. No differences were found between novice and experienced groups.

Sonographic inferior vena cava measurements to assess hydration status in college football players during preseason camp

OBJECTIVES

The purpose of this study was to determine whether sonographic measurement of the inferior vena cava (IVC) in college football players during preseason camp is a reliable way to detect and monitor dehydration. Our primary hypothesis was that IVC diameter measurements, the postpractice caval index, and expiratory diameter were significantly related to percent weight loss after a preseason football practice.

METHODS

A prospective cohort sample of Division I intercollegiate football players in preseason training camp was recruited before practice. All football players on the active roster who were at least 18 years of age were eligible to participate in the study. Sonographic IVC measurements were obtained in the long axis using either the subcostal or subxiphoid approach during inspiration and expiration both before and after an approximately 3-hour practice with moderate to high levels of exertion at high ambient temperatures. Player weights were recorded in the locker room before and after practice.

RESULTS

A total of 27 prepractice and postpractice sonographic measurements were obtained. The postpractice expiratory IVC diameter was significantly related to percent weight loss after practice (R(2) = 0.153; P = .042), with the IVC diameter being significantly inversely correlated with percent weight loss; the regression coefficient was -1.07 (95% confidence interval, -2.09 to -0.04). There was no statistically significant relationship between percent weight loss and the postpractice caval index; the regression coefficient was 0.245 (95% confidence interval, -0.10 to 0.59; R(2) = 0.078; P = .16).

CONCLUSIONS

The postpractice expiratory IVC diameter was significantly related to percent weight loss after practice, whereas the caval index was not found to correlate with weight loss.

Assessing volume status and fluid responsiveness in the emergency department

Resuscitation with intravenous fluid can restore intravascular volume and improve stroke volume. However, in unstable patients, approximately 50% of fluid boluses fail to improve cardiac output as intended. Increasing evidence suggests that excess fluid may worsen patient outcomes. Clinical examination and vital signs are unreliable predictors of the response to a fluid challenge. We review the importance of fluid management in the critically ill, methods of evaluating volume status, and tools to predict fluid responsiveness.

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.

Optimizing oxygen delivery in the critically ill: assessment of volume responsiveness in the septic patient

BACKGROUND

Assessing volume responsiveness, defined as an increase in cardiac index after infusion of fluids, is important when caring for critically ill patients in septic shock, as both under- and over-resuscitation can worsen outcomes. This review article describes the currently available methods of assessing volume responsiveness for critically ill patients in the emergency department, with a focus on patients in septic shock.

OBJECTIVE

The single-pump model of the circulation utilizing cardiac-filling pressures is reviewed in detail. Additionally, the dual-pump model evaluating cardiopulmonary interactions both invasively and noninvasively will be described.

DISCUSSION

Cardiac filling pressures (central venous pressure and pulmonary artery occlusion pressure) have poor performance characteristics when used to predict volume responsiveness. Cardiopulmonary interaction assessments (inferior vena cava distensibility/collapsibility, systolic pressure variation, pulse pressure variation, stroke volume variation, and aortic flow velocities) have superior test characteristics when measured either invasively or noninvasively.

CONCLUSION

Cardiac filling pressures may be misleading if used to determine volume responsiveness. Assessment of cardiopulmonary interactions has superior performance characteristics, and should be preferentially used for septic shock patients in the emergency department.

Ultrasonographic measurement of the respiratory variation in the inferior vena cava diameter is predictive of fluid responsiveness in critically ill patients: systematic review and meta-analysis

Respiratory variation in the inferior vena cava (ΔIVC) has been extensively studied with respect to its value in predicting fluid responsiveness, but the results are conflicting. This systematic review was aimed at investigating the diagnostic accuracy of ΔIVC in predicting fluid responsiveness. Databases including Medline, Embase, Scopus and Web of Knowledge were searched from inception to May 2013. Studies exploring the diagnostic performance of ΔIVC in predicting fluid responsiveness were included. To allow for more between- and within-study variance, a hierarchical summary receiver operating characteristic model was used to pool the results. Subgroup analyses were performed for patients on mechanical ventilation, spontaneously breathing patients and those challenged with colloids and crystalloids. A total of 8 studies involving 235 patients were eligible for analysis. Cutoff values of ΔIVC varied across studies, ranging from 12% to 40%. The pooled sensitivity and specificity in the overall population were 0.76 (95% confidence interval [CI]: 0.61-0.86) and 0.86 (95% CI: 0.69-0.95), respectively. The pooled diagnostic odds ratio (DOR) was 20.2 (95% CI: 6.1-67.1). The diagnostic performance of ΔIVC appeared to be better in patients on mechanical ventilation than in spontaneously breathing patients (DOR: 30.8 vs. 13.2). The pooled area under the receiver operating characteristic curve was 0.84 (95% CI: 0.79-0.89). Our study indicates that ΔIVC measured with point-of-care ultrasonography is of great value in predicting fluid responsiveness, particularly in patients on controlled mechanical ventilation and those resuscitated with colloids.

Fluid responsiveness predicted by elevation of PEEP in patients with septic shock

BACKGROUND

The assessment of whether a patient is fluid responsive can be difficult in clinical practice. Invasive filling pressures are inadequate indicators of preload and fluid responsiveness in critically ill patients. Dynamic indices may be unreliable in clinical practice because of arrhythmias or spontaneous breathing efforts. Elevation of positive end-expiratory pressure (PEEP) causes cardiorespiratory interactions, which may produce signs of hypovolaemia. Our aim was to assess whether haemodynamic changes during a short elevation of PEEP would predict fluid responsiveness in patients with septic shock.

METHODS

We performed a prospective observational study in 20 patients with septic shock on mechanical ventilation. We assessed the following changes in haemodynamic variables during a temporary elevation of PEEP from 10 cm H2O to 20 cm H2O during an end-expiratory pause: mean arterial pressure (MAP), systolic arterial pressure, pulse pressure, central venous pressure, pulmonary artery occlusion pressure, left ventricular end diastolic area and aortic velocity-time integral. We defined fluid responsiveness as an increase in cardiac output of 15% to a subsequent fluid challenge.

RESULTS

Decrease in MAP related to elevation of PEEP predicted fluid responsiveness (P = 0.003). The best cut-off value of ΔMAP for clinical use was -8%, with a negative predictive value for fluid responsiveness of 100%.

CONCLUSION

In patients with septic shock, the absence of decrease in MAP during an elevation of PEEP may be used to identify patients who will not increase their cardiac output in response to fluid challenge.