Respiratory changes of the inferior vena cava diameter predict fluid responsiveness in spontaneously breathing patients with cardiac arrhythmias

Predicting fluid responsiveness in spontaneously breathing parturients undergoing caesarean section via carotid artery blood flow and velocity time integral measured by carotid ultrasound: a prospective cohort study

BACKGROUND

Present evidence suggests that the Doppler ultrasonographic indices, such as carotid artery blood flow (CABF) and velocity time integral (VTI), had the ability to predict fluid responsiveness in non-obstetric patients. The purpose of this study was to assess their capacity to predict fluid responsiveness in spontaneous breathing parturients undergoing caesarean section and to determine the effect of detecting and management of hypovolemia (fluid responsiveness) on the incidence of hypotension after anaesthesia.

METHODS

A total of 72 full term singleton parturients undergoing elective caesarean section were enrolled in this study. CABF, VTI, and hemodynamic parameters were recorded before and after fluid challenge and assessed by carotid artery ultrasonography. Fluid responsiveness was defined as an increase in stroke volume index (SVI) of 15% or more after the fluid challenge.

RESULTS

Thirty-one (43%) patients were fluid responders. The area under the ROC curve to predict fluid responsiveness for CABF and VTI were 0.803 (95% CI, 0.701-0.905) and 0.821 (95% CI, 0.720-0.922). The optimal cut-off values of CABF and VTI for fluid responsiveness was 175.9 ml/min (sensitivity of 74.0%; specificity of 78.0%) and 8.7 cm/s (sensitivity of 67.0%; specificity of 90.0%). The grey zone for CABF and VTI were 114.2-175.9 ml/min and 6.8-8.7 cm/s. The incidence of hypotension after the combined spinal-epidural anaesthesia (CSEA) was significantly higher in the Responders group 25.8% (8/31) than in the Non-Responders group 17.1(7/41) (P < 0.001). The total incidence of hypotension after CSEA of the two groups was 20.8% (15/72).

CONCLUSIONS

Ultrasound evaluation of CABF and VTI seem to be the feasible parameters to predict fluid responsiveness in parturients undergoing elective caesarean section and detecting and management of hypovolemia (fluid responsiveness) could significantly decrease incidence of hypotension after anaesthesia.

TRIAL REGISTRATION

The trial was registered at the Chinese Clinical Trial Registry (ChiCTR) ( www.chictr.org ), registration number was ChiCTR1900022327 (The website link: https://www.chictr.org.cn/showproj.html?proj=37271 ) and the date of trial registration was in April 5, 2019. This study was performed in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee of Women's Hospital, Zhejiang University School of Medicine (20,180,120).

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.

Role of Inferior Vena Cava Collapsibility Index in the Prediction of Hypotension Associated With Central Neuraxial Block: A Prospective Observational Study

BACKGROUND

There are only a few studies on perioperative use of inferior vena cava collapsibility index (IVCCI) to predict hypotension after anesthesia. The study aimed to evaluate IVCCI as predictor of hypotension in patients receiving central neuraxial block (CNB) for elective surgery.

METHOD

One hundred patients of ASA grade I/II, aged 18-60 years undergoing elective surgery under CNB were enrolled. Ultrasound IVC examination was performed preoperatively and the patients were allocated to Group C (Collapsing group: IVCCI ≥50%) or Group NC (Non-Collapsing group: IVCCI <50%). Thereafter, in the operation theatre, the patient was given CNB and observed for development of hypotension. The hypotension was treated with additional fluid bolus (5 mL kg-1 over 10 minutes) and/or vasopressor (mephentramine 6 mg IV). The primary objective was to compare the incidence of hypotension; the secondary objective was to compare the fluid and vasopressor requirement in the Groups C and NC.

RESULT

Six patients were excluded from study due to poor visualization of IVC. The mean IVCCI for Group C (n = 53) was 56.06 ± 4.62% and Group NC (n = 41) was 34.01 ± 8.94%. The incidence of hypotension was 56.60% (20/53) in Group C and 4.87% (2/41) in Group NC (P < .001). The vasopressor and fluid requirement was also statistically significantly higher in Group C compared with Group NC (P < .001).

CONCLUSION

Preoperative ultrasound assessment of IVCCI is useful in predicting hypotension after CNB in patients receiving CNB for elective surgery.

RESPIRATION-RELATED VARIATIONS IN CENTRAL VENOUS PRESSURE AS PREDICTORS OF FLUID RESPONSIVENESS IN SPONTANEOUSLY BREATHING PATIENTS

ABSTRACT

Objective : The hemodynamic parameters used to accurately predict fluid responsiveness (FR) in spontaneously breathing patients (SB) require specific material and expertise. Measurements of the central venous pressure (CVP) are relatively simple and, importantly, are feasible in many critically ill patients. We analyzed the accuracy of respiration-related variations in CVP (vCVP) to predict FR in SB patients and examined the optimization of its measurement using a standardized, deep inspiratory maneuver. Patients and Methods : We performed a monocentric, prospective, diagnostic evaluation. Spontaneously breathing patients in intensive care units with a central venous catheter were prospectively included. The vCVP was measured while the patient was spontaneously breathing, both with (vCVP-st) and without (vCVP-ns) a standardized inspiratory maneuver, and calculated as: Minimum inspiratory v-wave peak pressure - Maximum expiratory v-wave peak pressure. A passive leg raising-induced increase in the left ventricular outflow tract velocity-time integral ≥10% defined FR. Results : Among 63 patients, 38 (60.3%) presented FR. The vCVP-ns was not significantly different between responders and nonresponders (-4.9 mm Hg [-7.5 to -3.1] vs. -4.1 mm Hg [-5.4 to 2.8], respectively; P = 0.15). The vCVP-st was lower in responders than nonresponders (-9.7 mm Hg [-13.9 to -6.2] vs. -3.6 mm Hg [-10.6 to -1.6], respectively; P = 0.004). A vCVP-st < -4.7 mm Hg predicted FR with 89.5% sensitivity, a specificity of 56.0%, and an area under the receiver operating characteristic curve of 0.72 (95% CI, 0.58 to 0.86) ( P = 0.004). Conclusion : When a central venous catheter is present, elevated values for vCVP-st may be useful to identify spontaneously breathing patients unresponsive to volume expansion. Nevertheless, the necessity of performing a standardized, deep-inspiration maneuver may limit its clinical application.

Predictors of fluid responsiveness in the operating room: a narrative review

Prediction of fluid responsiveness has been considered an essential tool for modern fluid management. However, most studies in this field have focused on patients in intensive care unit despite numerous research throughout several decades. Therefore, the present narrative review aims to show the representative method's feasibility, advantages, and limitations in predicting fluid responsiveness, focusing on the operating room environments. Firstly, we described the predictors of fluid responsiveness based on heart-lung interaction, including pulse pressure and stroke volume variations, the measurement of respiratory variations of inferior vena cava diameter, and the end-expiratory occlusion test and addressed their limitations. Subsequently, the passive leg raising test and mini-fluid challenge tests were also mentioned, which assess fluid responsiveness by mimicking a classic fluid challenge. In the last part of this review, we pointed out the pitfalls of fluid management based on fluid responsiveness prediction, which emphasized the importance of individualized decision-making. Understanding the available representative methods to predict fluid responsiveness and their associated benefits and drawbacks through this review will aid anesthesiologists in choosing the most reliable methods for optimal fluid administration in each patient during anesthesia in the operating room.

The use of bedside echocardiography in the care of critically ill patients - a joint consensus document of the Associação de Medicina Intensiva Brasileira, Associação Brasileira de Medicina de Emergência and Sociedade Brasileira de Medicina Hospitalar. Part 2 - Technical aspects

Echocardiography in critically ill patients has become essential in the evaluation of patients in different settings, such as the hospital. However, unlike for other matters related to the care of these patients, there are still no recommendations from national medical societies on the subject. The objective of this document was to organize and make available expert consensus opinions that may help to better incorporate echocardiography in the evaluation of critically ill patients. Thus, the Associação de Medicina Intensiva Brasileira, the Associação Brasileira de Medicina de Emergência, and the Sociedade Brasileira de Medicina Hospitalar formed a group of 17 physicians to formulate questions relevant to the topic and discuss the possibility of consensus for each of them. All questions were prepared using a five-point Likert scale. Consensus was defined a priori as at least 80% of the responses between one and two or between four and five. The consideration of the issues involved two rounds of voting and debate among all participants. The 27 questions prepared make up the present document and are divided into 4 major assessment areas: left ventricular function, right ventricular function, diagnosis of shock, and hemodynamics. At the end of the process, there were 17 positive (agreement) and 3 negative (disagreement) consensuses; another 7 questions remained without consensus. Although areas of uncertainty persist, this document brings together consensus opinions on several issues related to echocardiography in critically ill patients and may enhance its development in the national scenario.

Fluid responsiveness assessment using inferior vena cava collapsibility among spontaneously breathing patients: Systematic review and meta-analysis

OBJECTIVE

To synthesize the evidence about diagnostic accuracy of inferior vena cava collapsibility (IVCc) in prediction of fluid responsiveness among spontaneously breathing patients.

DESIGN

Systematic review of diagnostic accuracy studies.

SETTING

Intensive care units or emergency departments.

PATIENTS AND PARTICIPANTS

spontaneously breathing patients with indication for fluid bolus administration.

INTERVENTIONS

A search was conducted in MEDLINE and EMBASE. We included studies assessing IVCc accuracy for fluid responsiveness assessment with a standard method for cardiac output measure as index test.

MAIN VARIABLES OF INTEREST

General information (year, setting, cutoffs, standard method), sensitivity, specificity, and area under the receiving operator characteristics curve (AUROC). Risk of bias was assessed with QUADAS 2 tool. We obtained the pooled sensitivity, specificity and summary ROC curve, with estimated confidence intervals from a bivariate model. We also calculated positive and negative likelihood ratios and developed a Fagon nomogram.

RESULTS

Eight studies were included with 497 patients. Overall, the studies presented a high risk of bias. IVCc sensitivity was 63% (95% CI - 46-78%) and specificity 83% (95% CI - 76-87%). Despite moderate accuracy of IVCc (SROC 0.83, 95% CI - 0.80-0.86), post-test probability of being fluid responsive based on a 50% pre-test probability led to considerable misclassification.

CONCLUSIONS

IVCc had moderate accuracy for fluid responsiveness assessment in spontaneously breathing patients and should not be used in isolation for this purpose.

Caudal vena cava measurements and fluid responsiveness in hospitalized cats with compromised hemodynamics and tissue hypoperfusion

OBJECTIVE

To evaluate the use of the caudal vena cava collapsibility index (CVCCI) and the inspiratory/minimum and expiratory/maximum diameters of the vena cava to predict fluid responsiveness in hospitalized, critically ill cats with hemodynamic and tissue perfusion abnormalities.

DESIGN

Diagnostic test study in a prospective cohort of hospitalized cats.

SETTING

Private practice referral hospital.

ANIMALS

Twenty-four hospitalized cats with spontaneous breathing and compromised hemodynamics and tissue hypoperfusion.

INTERVENTIONS

Ultrasonographic examination before and after fluid expansion with 10 ml/kg of lactated Ringer's solution.

MEASUREMENTS AND MAIN RESULTS

Fluid responsiveness was evaluated using the velocity-time integral (VTI) of the subaortic blood flow, by measuring it before and after a fluid load of 10 ml/kg of lactated Ringer's solution. The CVCCI was calculated using the following formula: (maximum diameter - minimum diameter / maximum diameter) × 100. Ten cats were fluid responders (42 %) and 14 were nonresponders (58 %). The area under the receiver operating characteristic curve (AUROC) with their 95% confidence interval for the predictors and the best cutoff values were as follows: CVCCI, AUROC = 0.83 (0.66-1.00) and cutoff = 31%; inspiratory/minimum diameter, AUROC = 0.86 (0.70-1.00) and cutoff = 0.24 cm; expiratory/maximum diameter, AUROC = 0.88 (0.74-1.00) and cutoff = 0.22 cm. A significant lineal correlation was observed between the percentage of increase in VTI after expansion and CVCCI (r_s  = 0.68, P < 0.001), expiratory/maximum diameter (r_s  = -0.72, P < 0.001), and inspiratory/minimum diameter (r_s  = -0.71, P < 0.001). The intraobserver and interobserver variability was low for VTI, and the expiratory/maximum diameter and inspiratory/minimum diameter were high for CVCCI.

CONCLUSIONS

Caudal vena cava measurements could be useful to predict the response to fluids in hospitalized cats with hemodynamic and tissue perfusion alterations. Additional studies are required to draw definitive conclusions about the role of these variables to guide fluid administration in cats.

The Cardiac Caval Index: Improving Noninvasive Assessment of Cardiac Preload

OBJECTIVES

Inferior vena cava (IVC) pulsatility quantified by the Caval Index (CI) is characterized by poor reliability, also due to the irregular magnitude of spontaneous respiratory activity generating the major pulsatile component. The aim of this study was to test whether the IVC cardiac oscillatory component could provide a more stable index (Cardiac CI-CCI) compared to CI or respiratory CI (RCI).

METHODS

Nine healthy volunteers underwent long-term monitoring in supine position of IVC, followed by 3 minutes passive leg raising (PLR). CI, RCI, and CCI were extracted from video recordings by automated edge-tracking and CCI was averaged over each respiratory cycle (aCCI). Cardiac output (CO), mean arterial pressure (MAP) and heart rate (HR) were also recorded during baseline (1 minutes prior to PLR) and PLR (first minute).

RESULTS

In response to PLR, all IVC indices decreased (P < .01), CO increased by 4 ± 4% (P = .055) while HR and MAP did not vary. The Coefficient of Variation (CoV) of aCCI (13 ± 5%) was lower than that of CI (17 ± 5%, P < .01), RCI (26 ± 7%, P < .001) and CCI (25 ± 7%, P < .001). The mutual correlations in time of the indices were 0.81 (CI-RCI), 0.49 (CI-aCCI) and 0.2 (RCI-aCCI).

CONCLUSIONS

Long-term IVC monitoring by automated edge-tracking allowed us to evidence that 1) respiratory and averaged cardiac pulsatility components are uncorrelated and thus carry different information and 2) the new index aCCI, exhibiting the lowest CoV while maintaining good sensitivity to blood volume changes, may overcome the poor reliability of CI and RCI.

Comparison of inferior vena cava collapsibility and central venous pressure in assessing volume status in shocked patients

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An accurate diagnosis of shock state can be challenging, particularly in low-income countries, such as African countries, because physical signs of hypovolaemic, distributive, cardiogenic, and obstructive shock frequently overlap.

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Low-income countries therefore require easy and noninvasive methods, such as ultrasound devices.

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This study aims to provide an accurate estimation of intravascular volume status using bedside noninvasive methods as an essential part of the management of shocked patients.

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We discovered that the inferior vena cava collapsibility index (IVC-ci) could be a good tool with moderate reliability for detecting fluid responsiveness because it is a less invasive and fast method.

Introduction

Determination of intravascular volume status in patients admitted to the emergency centre is critical. Physical signs of hypovolaemic, distributive, cardiogenic, and obstructive shock frequently overlap, making an accurate diagnosis of shock state difficult. This is problematic because fluid loading is considered the first step in haemodynamically unstable patients’ resuscitation. Yet, multiple studies have shown that only approximately 50% of haemodynamically unstable patients in the intensive care unit and operating theatre respond to a fluid challenge. This study aims to provide an accurate estimation of intravascular volume status using bedside noninvasive methods as an essential part of the assessment of volume status in shocked patients.

Methodology

This is a cross-sectional analytical study conducted on 102 shocked patients presented to the emergency centre. IV fluid boluses were standardized to be administered at 500 mL every 30 min over 120 min, as clinically indicated. Concurrent measurements of inferior vena cava collapsibility index (IVC-ci) were performed shortly before the initiation of IV bolus (i.e., time 0), and then at 30, 90, and 120 min, we measured both venous collapsibility index (CI) and central venous pressure (CVP). At each session, we recorded patient demographics, fluid responsiveness, and vital sign assessments.

Results

We discovered that IVC-ci at cut-off point 40 has a sensitivity of 93.3% and specificity of 70.7% with an AUC of 0.908 and a good 95% CI (0.84–0.975), implying that IVC-ci of 40% or higher can indicate fluid responsiveness in shocked patients. CVP, despite having a good sensitivity of 88.6%, high specificity of 100%, and a significant p-value, is not a reliable detector of fluid responsiveness due to its small AUC value and low 95% CI.

Conclusion

IVC-ci could be a good tool with moderate reliability for detecting fluid responsiveness because it is a less invasive and fast method.

Ultrasound dynamic monitoring of IVCD to guide application of CRRT in patients with renal failure combined with acute heart failure

We explored the application value of bedside ultrasound dynamic monitoring of the inferior vena cava diameter (IVCD) and collapse with sniff (inferior vena cava collapsibility index [IVCCI]) to guide dehydration adjustment in continuous renal replacement therapy (CRRT) in patients with combined renal failure and acute heart failure. We selected 90 patients with combined renal and acute heart failure who required CRRT in the intensive care unit (ICU) from January 2019 to June 2021. According to different blood volume assessment methods, patients were randomly divided into ultrasound, experience, and control groups. We compared serum creatinine, potassium, and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels; time to improved heart failure symptoms; CRRT time; ventilator use; ICU length of stay; vasopressor use; and incidence of adverse events among groups. There were no significant differences in serum creatinine, potassium, and NT-proBNP levels in pairwise comparisons among groups before and after CRRT (P > 0.05). The time to improved heart failure symptoms, CRRT time, and ICU length of stay in the ultrasound and experience groups were lower than those in the control group; the differences were statistically significant (P < 0.05). Ventilator use duration was lower in the ultrasound and experience groups compared with the control group, with a statistically significant difference between the ultrasound and control groups (P < 0.05). The duration of vasopressor use in the ultrasound and control groups was lower than that in the experience group; the difference was statistically significant (P < 0.05). The incidence of adverse events was lower in the ultrasound group compared with the experience and control groups; the difference was statistically significant (P < 0.05). Ultrasound dynamic monitoring of IVCD and collapse with sniff can accurately assess blood volume status, and provide guidance for dehydration adjustments in CRRT and rapid relief of heart failure symptoms in patients with combined renal and acute heart failure.

Inferior vena cava ultrasonography in the assessment of intravascular volume status and fluid responsiveness in the emergency department and intensive care unit: A critical analysis review

Rapid evaluation of intravascular volume status is vital; either excessive or limited fluid administration may result in adverse patient outcomes. In this narrative review, critical analysis of pertinent diagnostic accuracy studies is developed to delineate the role of inferior vena cava ultrasound measurements in the assessment of both intravascular volume status and fluid responsiveness in the emergency department and intensive care unit. In addition, limitations, and technical considerations of inferior vena cava ultrasound measurements as well as directions for future research are thoroughly discussed.

Prediction of post-induction hypotension by point-of-care echocardiography: A prospective observational study

BACKGROUND

Post-induction hypotension (PIH) is a common side effect of general anaesthesia and is associated with poor perioperative outcomes. We assessed the ability of two point-of-care echocardiographic variables to predict the occurrence of PIH: the passive leg raising-induced changes in the velocity-time integral of the left ventricular outflow tract (ΔVTI-PLR) and the inferior vena cava collapsibility index (IVC-CI).

METHODS

We studied 64 patients > 50 years scheduled for elective abdominal surgery. ΔVTI-PLR and IVC-CI were prospectively obtained before general anaesthesia induction. PIH was defined by a systolic arterial pressure < 90 mmHg or a mean arterial pressure < 65 mmHg or by a decrease in systolic or mean arterial pressure > 30% from pre-induction level. Intraclass correlation coefficients (ICCs) were calculated to assess the reproducibility of echocardiographic measurements. Receiver operating characteristic (ROC) curves with 95% confidence intervals (CIs) were generated to test the ability of ΔVTI-PLR and IVC-CI to predict the occurrence of PIH.

RESULTS

PIH occurred in 33 (51%) patients. The ICCs for VTI and IVC measurements showed excellent reproducibility. The occurrence of PIH was accurately predicted by ΔVTI-PLR with an area under the ROC curve (AUROC) of 0.89 (95% CI: 0.80-0.97), a threshold value of 18% with a sensitivity of 88% (95% CI: 71-97%) and a specificity of 84% (95% CI: 66-94%). The occurrence of PIH was poorly predicted by IVC-CI with an AUROC of 0.68 (95% CI: 0.54-0.80) and a threshold value of 42%.

CONCLUSIONS

ΔVTI-PLR, unlike IVC-CI, could reliably predict the occurrence of PIH. The use of ΔVTI-PLR could help individualise anaesthesia management to prevent PIH.

Automated versus manual B-lines counting, left ventricular outflow tract velocity time integral and inferior vena cava collapsibility index in COVID-19 patients

Background and Aims:

The incorporation of artificial intelligence (AI) in point-of-care ultrasound (POCUS) has become a very useful tool to quickly assess cardiorespiratory function in coronavirus disease (COVID)-19 patients. The objective of this study was to test the agreement between manual and automated B-lines counting, left ventricular outflow tract velocity time integral (LVOT-VTI) and inferior vena cava collapsibility index (IVC-CI) in suspected or confirmed COVID-19 patients using AI integrated POCUS. In addition, we investigated the inter-observer, intra-observer variability and reliability of assessment of echocardiographic parameters using AI by a novice.

Methods:

Two experienced sonographers in POCUS and one novice learner independently and consecutively performed ultrasound assessment of B-lines counting, LVOT-VTI and IVC-CI in 83 suspected and confirmed COVID-19 cases which included both manual and AI methods.

Results:

Agreement between automated and manual assessment of LVOT-VTI, and IVC-CI were excellent [intraclass correlation coefficient (ICC) 0.98, P < 0.001]. Intra-observer reliability and inter-observer reliability of these parameters were excellent [ICC 0.96-0.99, P < 0.001]. Moreover, agreement between novice and experts using AI for LVOT-VTI and IVC-CI assessment was also excellent [ICC 0.95-0.97, P < 0.001]. However, correlation and intra-observer reliability between automated and manual B-lines counting was moderate [(ICC) 0.52-0.53, P < 0.001] and [ICC 0.56-0.69, P < 0.001], respectively. Inter-observer reliability was good [ICC 0.79-0.87, P < 0.001]. Agreement of B-lines counting between novice and experts using AI was weak [ICC 0.18, P < 0.001].

Conclusion:

AI-guided assessment of LVOT-VTI, IVC-CI and B-lines counting is reliable and consistent with manual assessment in COVID-19 patients. Novices can reliably estimate LVOT-VTI and IVC-CI using AI software in COVID-19 patients.

Diagnostic Accuracy of Ultrasonographic Respiratory Variation in the Inferior Vena Cava, Subclavian Vein, Internal Jugular Vein, and Femoral Vein Diameter to Predict Fluid Responsiveness: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to investigate the ultrasonographic variation of the diameter of the inferior vena cava (IVC), internal jugular vein (IJV), subclavian vein (SCV), and femoral vein (FV) to predict fluid responsiveness in critically ill patients. Relevant articles were obtained by searching PubMed, EMBASE, and Cochrane databases (articles up to 21 October 2021). The number of true positives, false positives, false negatives, and true negatives for the index test to predict fluid responsiveness was collected. We used a hierarchical summary receiver operating characteristics model and bivariate model for meta-analysis. Finally, 30 studies comprising 1719 patients were included in this review. The ultrasonographic variation of the IVC showed a pooled sensitivity and specificity of 0.75 and 0.83, respectively. The area under the receiver operating characteristics curve was 0.86. In the subgroup analysis, there was no difference between patients on mechanical ventilation and those breathing spontaneously. In terms of the IJV, SCV, and FV, meta-analysis was not conducted due to the limited number of studies. The ultrasonographic measurement of the variation in diameter of the IVC has a favorable diagnostic accuracy for predicting fluid responsiveness in critically ill patients. However, there was insufficient evidence in terms of the IJV, SCV, and FV.

Optimizing Fluid Resuscitation and Preventing Fluid Overload in Patients with Septic Shock

Intravenous fluid administration remains an important component in the care of patients with septic shock. A common error in the treatment of septic shock is the use of excessive fluid in an effort to overcome both hypovolemia and vasoplegia. While fluids are necessary to help correct the intravascular depletion, vasopressors should be concomitantly administered to address vasoplegia. Excessive fluid administration is associated with worse outcomes in septic shock, so great care should be taken when deciding how much fluid to give these vulnerable patients. Simple or strict "recipes" which mandate an exact amount of fluid to administer, even when weight based, are not associated with better outcomes and therefore should be avoided. Determining the correct amount of fluid requires the clinician to repeatedly assess and consider multiple variables, including the fluid deficit, organ dysfunction, tolerance of additional fluid, and overall trajectory of the shock state. Dynamic indices, often involving the interaction between the cardiovascular and respiratory systems, appear to be superior to traditional static indices such as central venous pressure for assessing fluid responsiveness. Point-of-care ultrasound offers the bedside clinician a multitude of applications which are useful in determining fluid administration in septic shock. In summary, prevention of fluid overload in septic shock patients is extremely important, and requires the careful attention of the entire critical care team.

Does respiratory variation in inferior vena cava diameter predict fluid responsiveness in adult patients? A systematic review and meta-analysis of diagnostic accuracy studies

Objectives:

To systematically review the diagnostic utility of the respiratory variation of the inferior vena cava diameter measured using ultrasonography for predicting fluid responsiveness in adult patients and compare the three commonly used equations, inferior vena cava distensibility, inferior vena cava collapsibility and inferior vena cava variability.

Methods:

We searched PubMed, Scopus, Web of Science and Cochrane library, and included studies investigating the diagnostic accuracy of the respiratory variation of the inferior vena cava measured using ultrasonography compared to a reference standard for measuring cardiac output after a fluid challenge for fluid responsiveness, and stratified participants as fluid responsive or not. We included studies conducted in the emergency department or intensive care unit. We excluded studies on paediatric, prehospital, cancer, pregnant, dialysis patients or healthy volunteers.

Results:

We retrieved 270 records and excluded 171 because of irrelevance, patient population or publication type. We screened the abstracts of 99 studies and then the full texts of 42 studies. Overall, 21 studies with 1321 patients were included, of whom 689 (52%) were fluid responsive. The mean threshold value for positive inferior vena cava distensibility, inferior vena cava collapsibility and inferior vena cava variability was 17%, 35% and 12%, respectively. The heterogeneity between studies was high. Bivariate diagnostic random-effects meta-analysis was used to calculate the summary receiver operating characteristics curves. The overall accuracy, sensitivity and specificity of respiratory variation of the inferior vena cava diameter were 0.85, 0.72 and 0.81, respectively. The accuracy of inferior vena cava distensibility and inferior vena cava collapsibility was similar. The diagnostic utility of respiratory variation of the inferior vena cava diameter was lower but not statistically significant in mechanically ventilated patients compared with spontaneous breathing for predicting fluid responsiveness.

Conclusion:

The respiratory variation of the inferior vena cava diameter has moderate diagnostic utility for predicting fluid responsiveness independent of the equation used.

Ultrasound Assessment of the Inferior Vena Cava for Fluid Responsiveness: Making the Case for Skepticism

Determining whether a patient in shock is in a state of fluid responsiveness (FR) has long been the Holy Grail for clinicians who care for acutely ill patients. While various tools have been put forth as solutions to this important problem, ultrasound assessment of the inferior vena cava has received particular attention of late. Dozens of studies have examined its ability to determine whether a patient should receive volume expansion, and general enthusiasm has been strengthened by the fact that it is easy to perform and non-invasive, unlike many competing FR tests. A deeper examination of the technique, however, reveals important concerns regarding inaccuracies in measurement and a high prevalence of confounding factors. Furthermore, a detailed review of the evidence (small individual studies, multiple meta-analyses, and a single large trial) reveals that the tool performs poorly in general and is unlikely to be helpful at the bedside in circumstances where genuine clinical uncertainty exists.

Inferior Vena Cava Collapsibility Index: Clinical Validation and Application for Assessment of Relative Intravascular Volume

Accurate assessment of relative intravascular volume is critical to guide volume management of patients with acute or chronic kidney disorders, particularly those with complex comorbidities requiring hospitalization or intensive care. Inferior vena cava (IVC) diameter variability with respiration measured by ultrasound provides a dynamic noninvasive point-of-care estimate of relative intravascular volume. We present details of image acquisition, interpretation, and clinical scenarios to which IVC ultrasound can be applied. The variation in IVC diameter over the respiratory or ventilatory cycle is greater in patients who are volume responsive than those who are not volume responsive. When 2 recent prospective studies of spontaneously breathing patients (n = 214) are added to a prior meta-analysis of 181 patients, for a total of 7 studies of 395 spontaneously breathing patients, IVC collapsibility index (CI) had a pooled sensitivity of 71% and specificity of 81% for predicting volume responsiveness, which is similar to a pooled sensitivity of 75% and specificity of 82% for 9 studies of 284 mechanically ventilated patients. IVC maximum diameter <2.1 cm, that collapses >50% with or without a sniff is inconsistent with intravascular volume overload and suggests normal right atrial pressure (0-5 mmHg). Inferior vena cava collapsibility (IVC CI) < 20% with no sniff suggests increased right atrial pressure and is inconsistent with overt hypovolemia in spontaneously breathing or ventilated patients. These IVC CI cutoffs do not appear to vary greatly depending on whether patients are breathing spontaneously or are mechanically ventilated. Patients with lower IVC CI are more likely to tolerate ultrafiltration with hemodialysis or improve cardiac output with ultrafiltration. Our goal for IVC CI generally ranges from 20% to 50%, respecting potential biases to interpretation and overriding clinical considerations. IVC ultrasound may be limited by factors that affect IVC diameter or collapsibility, clinical interpretation, or optimal visualization, and must be interpreted in the context of the entire clinical situation.

Measurement site of inferior vena cava diameter affects the accuracy with which fluid responsiveness can be predicted in spontaneously breathing patients: a post hoc analysis of two prospective cohorts

Background

The collapsibility index of the inferior vena cava (cIVC) has potential for predicting fluid responsiveness in spontaneously breathing patients, but a standardized approach for measuring the inferior vena cava diameter has yet to be established.

The aim was to test the accuracy of different measurement sites of inferior vena cava diameter to predict fluid responsiveness in spontaneously breathing patients with sepsis-related circulatory failure and examine the influence of a standardized breathing manoeuvre.

Results

Among the 81 patients included in the study, the median Simplified Acute Physiologic Score II was 34 (24; 42). Sepsis was of pulmonary origin in 49 patients (60%). Median volume expansion during the 24 h prior to study inclusion was 1000 mL (0; 2000). Patients were not severely ill: none were intubated, only 20% were on vasopressors, and all were apparently able to perform a standardized breathing exercise. Forty-one (51%) patients were responders to volume expansion (i.e. a ≥ 10% stroke volume index increase). The cIVC was calculated during non-standardized (cIVC-ns) and standardized breathing (cIVC-st) conditions. The accuracy with which both cIVC-ns and cIVC-st predicted fluid responsiveness differed significantly by measurement site (interaction p < 0.001 and < 0.0001, respectively). Measuring inferior vena cava diameters 4 cm caudal to the right atrium predicted fluid responsiveness with the best accuracy. At this site, a standardized breathing manoeuvre also significantly improved predictive power: areas under ROC curves [mean and (95% CI)] for cIVC-ns = 0.85 [0.78–0.94] versus cIVC-st = 0.98 [0.97–1.0], p < 0.001. When cIVC-ns is superior or equal to 33%, fluid responsiveness is predicted with a sensitivity of 66% and a specificity of 92%. When cIVC-st is superior or equal to 44%, fluid responsiveness is predicted with a sensitivity of 93% and a specificity of 98%.

Conclusion

The accuracy with which cIVC measurements predict fluid responsiveness in spontaneously breathing patients depends on both the measurement site of inferior vena cava diameters and the breathing regime. Measuring inferior vena cava diameters during a standardized inhalation manoeuvre at 4 cm caudal to the right atrium seems to be the method by which to obtain cIVC measurements best-able to predict patients’ response to volume expansion.

New algorithm to quantify cardiopulmonary interaction in patients with atrial fibrillation: a proof-of-concept study

BACKGROUND

Traditional formulas to calculate pulse pressure variation (PPV) cannot be used in patients with atrial fibrillation (AF). We have developed a new algorithm that accounts for arrhythmia-induced pulse pressure changes, allowing us to isolate and quantify ventilation-induced pulse pressure variation (VPPV). The robustness of the algorithm was tested in patients subjected to altered loading conditions. We investigated whether changes in VPPV imposed by passive leg raising (PLR) were proportional to the pre-PLR values.

METHODS

Consenting patients with active AF scheduled for an ablation of the pulmonary vein under general anaesthesia and mechanical ventilation were included. Loading conditions were altered by PLR. ECG and invasive pressure data were acquired during 60 s periods before and after PLR. A generalised additive model was constructed for each patient on each observation period. The impact of AF was modelled on the two preceding RR intervals of each beat (RR₀ and RR_-1). The impact of ventilation and the long-term pulse pressure trends were modelled as separate splines. Ventilation-induced pulse pressure variation was defined as the percentage of the maximal change in pulse pressure during the ventilation cycle.

RESULTS

Nine patients were studied. The predictive abilities of the models had a median r² of 0.92 (inter-quartile range: 89.2-94.2). Pre-PLR VPPV ranged from 0.1% to 27.9%. After PLR, VPPV decreased to 0-11.3% (P<0.014). The relation between the Pre-PLR values and the magnitude of the changes imposed by the PLR was statistically significant (P<0.001).

CONCLUSIONS

Our algorithm enables quantification of VPPV in patients with AF with the ability to detect changing loading conditions.

Association of inferior vena cava diameter ratio measured on computed tomography scans with the outcome of patients with septic shock

The collapsibility and diameter of the inferior vena cava (IVC) are known to predict the volume state in critically ill patients. However, no study has examined the prognostic value of the IVC diameter ratio measured on computed tomography (CT) in patients with septic shock. A retrospective observational study was conducted on adult septic shock patients visiting the emergency department at a university hospital in Korea. The IVC diameter ratio was calculated by dividing the maximal transverse and anteroposterior diameters. Multivariable logistic regression analysis was conducted to investigate whether the IVC diameter ratio predicted in-hospital mortality. The area under the curve (AUC) was calculated, and the sensitivity, specificity, positive predictive value, and negative predictive value with the cut-off values were computed. A total of 423 adult septic shock patients were included, and the in-hospital mortality rate was 17%. The median IVC diameter ratio in non-survivors was significantly greater than in survivors (1.56 cm vs 1.4 cm, P = .004). The IVC diameter ratio was found to be significantly associated with in-hospital mortality on multivariate logistic regression analysis after adjustment for confounding variables (odds ratio = 1.48, confidence interval: 1.097-1.998, P = 0.01). The AUC for IVC diameter ratio was 0.607. A cut-off IVC diameter ratio of ≥1.31 cm had 75% sensitivity and 42% specificity for predicting in-hospital mortality. The IVC diameter ratio measured on CT may to be helpful in predicting the prognosis of septic shock patients. However, due to its low diagnostic performance and sensitivity, further research is warranted.

Prediction of fluid responsiveness in spontaneously breathing patients

In patients with acute circulatory failure, the primary goal of volume expansion is to increase cardiac output. However, this expected effect is inconstant, so that in many instances, fluid administration does not result in any haemodynamic benefit. In such cases, fluid could only exert some deleterious effects. It is now well demonstrated that excessive fluid administration is harmful, especially during acute respiratory distress syndrome and in sepsis or septic shock. This is the reason why some tests and indices have been developed in order to assess “fluid responsiveness” before deciding to perform volume expansion. While preload markers have been used for many years for this purpose, they have been repeatedly shown to be unreliable, which is mainly related to physiological issues. As alternatives, “dynamic” indices have been introduced. These indices are based upon the changes in cardiac output or stroke volume resulting from various changes in preload conditions, induced by heart-lung interactions, postural manoeuvres or by the infusion of small amounts of fluids. The haemodynamic effects and the reliability of these “dynamic” indices of fluid responsiveness are now well described. From their respective advantages and limitations, it is also possible to describe their clinical interest and the clinical setting in which they are applicable.

Ultrasound Measurement of Inferior Vena Cava Collapsibility as a Tool to Predict Propofol-Induced Hypotension

Background:

Hypotension is common under anesthesia and can cause organ underperfusion and ischemia, especially during induction. This could be because of the cardiovascular depressant and vasodilatory effects of anesthetic agents, as well as lack of surgical stimulation.

Aim of Study:

The aim was to evaluate the utility of preinduction inferior vena cava (IVC) measurement to predict significant hypotension after induction of anesthesia with propofol.

Settings and Design:

This was a prospective, open-label study conducted in a tertiary care institute.

Subjects and Methods:

This study was conducted on 50 patients undergoing general anesthesia. Ultrasound machine (Mindray® M7) was used to visualize IVC. The measurements taken were maximum diameter of IVC (IVC_max) and minimum diameter of IVC (IVC_min). IVC collapsibility index (IVC-CI) was calculated as (IVC_max − IVC_min)/IVC_max and was expressed as a ratio.

Statistical Tests Used:

Receiver operating characteristic (ROC) curve analysis and Chi-square test were used for statistical tests.

Results:

The relation between significant hypotension and IVC-CI was evaluated using ROC curve analysis. We found the area under curve to be 0.959 and a cutoff of 0.43 (43% collapsibility). The association of significant hypotension with IVC-CI of >43% was calculated and found to be statistically significant (P < 0.001). The sensitivity of IVC CI of >43% in predicting development of significant hypotension was 86.67% and the specificity was 94.29%. It had very high negative and positive predictive values (94.29% and 86.67%, respectively) with an accuracy of 92%.

Conclusion:

Patients with an IVC collapsibility of more than 43%, as assessed by ultrasonography, are more likely to develop significant hypotension after induction with propofol.

Systematic assessment of fluid responsiveness during early septic shock resuscitation: secondary analysis of the ANDROMEDA-SHOCK trial

BACKGROUND

Fluid boluses are administered to septic shock patients with the purpose of increasing cardiac output as a means to restore tissue perfusion. Unfortunately, fluid therapy has a narrow therapeutic index, and therefore, several approaches to increase safety have been proposed. Fluid responsiveness (FR) assessment might predict which patients will effectively increase cardiac output after a fluid bolus (FR+), thus preventing potentially harmful fluid administration in non-fluid responsive (FR-) patients. However, there are scarce data on the impact of assessing FR on major outcomes. The recent ANDROMEDA-SHOCK trial included systematic per-protocol assessment of FR. We performed a post hoc analysis of the study dataset with the aim of exploring the relationship between FR status at baseline, attainment of specific targets, and clinically relevant outcomes.

METHODS

ANDROMEDA-SHOCK compared the effect of peripheral perfusion- vs. lactate-targeted resuscitation on 28-day mortality. FR was assessed before each fluid bolus and periodically thereafter. FR+ and FR- subgroups, independent of the original randomization, were compared for fluid administration, achievement of resuscitation targets, vasoactive agents use, and major outcomes such as organ dysfunction and support, length of stay, and 28-day mortality.

RESULTS

FR could be determined in 348 patients at baseline. Two hundred and forty-two patients (70%) were categorized as fluid responders. Both groups achieved comparable successful resuscitation targets, although non-fluid responders received less resuscitation fluids (0 [0-500] vs. 1500 [1000-2500] mL; p 0.0001), exhibited less positive fluid balances, but received more vasopressor testing. No difference in clinically relevant outcomes between FR+ and FR- patients was found, including 24-h SOFA score (9 [5-12] vs. 8 [5-11], p = 0.4), need for MV (78% vs. 72%, p = 0.16), need for RRT (18% vs. 21%, p = 0.7), ICU-LOS (6 [3-11] vs. 6 [3-16] days, p = 0.2), and 28-day mortality (40% vs. 36%, p = 0.5). Only thirteen patients remained fluid responsive along the intervention period.

CONCLUSIONS

Systematic assessment allowed determination of fluid responsiveness status in more than 80% of patients with early septic shock. Fluid boluses could be stopped in non-fluid responsive patients without any negative impact on clinical relevant outcomes. Our results suggest that fluid resuscitation might be safely guided by FR assessment in septic shock patients.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03078712. Registered retrospectively on March 13, 2017.

A Two Parameters for the Evaluation of Hypovolemia in Patients with Septic Shock: Inferior Vena Cava Collapsibility Index (IVCCI), Delta Cardiac Output

Background

The aim of this study was to determine the correlation between inferior vena cava collapsibility index and changes in cardiac output measured during passive leg raising test in patients with spontaneous breathing and septic shock.

Material/Methods

Fifty-six patients were included in the study. All of these 56 patients were diagnosed with septic shock and had spontaneous breathing under continuous positive airway pressure. Patients exclusions included: patients with cardiac pathology, not septic shock, pregnant, spontaneous breathing, increased intra-abdominal pressure, inferior vena cava could not be visualized, arrhythmia and pulmonary hypertension.

Exclusion criteria for the study were as follows: 1) left ventricular systolic dysfunction, 2) cardiomyopathy, 3) medium severe heart valve disease, 4) patients with arrhythmia; 5) pulmonary hypertension, 6) patients without spontaneous breathing (for inferior vena cava collapsibility index, it is not evaluated), 7) patients with >60 mmHg CO₂ in arterial blood gas; 8) pregnant patients; 9) patients with neurogenic shock, cerebrovascular incident or traumatic brain injury, 10) patients whose inferior vena cava and parasternal long axis cannot be visualized, and 11) patients with increased intra-abdominal pressure.

Patients were placed in neutral supine position, and the inferior vena cava collapsibility index and cardiac output 1 were recorded. In passive leg raising test, after which the cardiac output 2 is recorded in terms of L/min. The percentage increase between the 2 cardiac outputs was calculated and recorded.

Results

A moderately positive correlation was also observed between the inferior vena cava collapsibility index and delta cardiac output (r=0.459; r2=0.21), which was statistically significant (P<0.001). The cutoff value for the delta cardiac output was 29.5.

Conclusions

In conclusion, we found that the inferior vena cava collapsibility index, which is one of the dynamic parameters used in the diagnosis of hypovolemia in patients with septic shock, is correlated with delta cardiac output after leg raising test. We believe that, based on a clinician’s experience, looking at 1 of these 2 parameters is sufficient for the identification of hypovolemia in patients diagnosed with septic shock.

Performance of a 25% Inferior Vena Cava Collapsibility in Detecting Fluid Responsiveness When Assessed by Novice Versus Expert Physician Sonologists

OBJECTIVES

Inferior vena cava collapsibility (cIVC) measured by point-of-care ultrasound (POCUS) has been proposed as a noninvasive means of assessing fluid responsiveness. We aimed to prospectively evaluate the performance of a 25% cIVC cutoff value to detect fluid responsiveness among spontaneously breathing intensive care unit (ICU) patients when assessed with POCUS by novice versus expert physician sonologists.

METHODS

Prospective observational study of spontaneously breathing ICU patients. Fluid responsiveness was defined as a >10% increase in cardiac index following a 500 mL fluid bolus, measured by bioreactance. Novice sonologist measured cIVC with POCUS. Their measurements were later compared to an expert physician sonologist who independently reviewed the POCUS images and assessed cIVCs.

RESULTS

Of the 85 participants, 44 (52%) were fluid responders. A 25% cIVC cutoff value performed better when assessed by expert sonologists than novice physician sonologists (receiver-operator characteristic curve, ROC = 0.82 [0.74-0.88] vs ROC = 0.69 [0.60-0.77]).

CONCLUSIONS

A 25% cIVC cutoff value measured by POCUS detects fluid responsiveness. However, the experience of the physician sonologist affects test performance and should be considered when interpreting and clinically using cIVC to direct intravenous fluid resuscitation.

Role of inferior vena cava collapsibility index in the prediction of hypotension associated with general anesthesia: an observational study

BACKGROUND

Intraoperative hypotension increases 30-day mortality and the risks of myocardial injury and acute renal failure. Patients with inadequate volume reserve before the induction of anesthesia are highly exposed. The identification of latent hypovolemia is therefore crucial. Ultrasonographic measurement of the inferior vena cava collapsibility index (IVCCI) is able to detect volume responsiveness in circulatory shock. No current evidence is available regarding whether preoperative measurement of the IVCCI could identify patients at high risk for hypotension associated with general anesthesia.

METHODS

A total of 102 patients undergoing elective general surgery under general anesthesia with standardized propofol induction were recruited for this prospective observational study. The IVCCI was measured under spontaneous breathing. A collapsing (IVCCI≧50%) (CI+) and a noncollapsing (CI-) group were formed. Immediate postinduction changes in systolic and mean blood pressure were compared. The performance of the IVCCI as a diagnostic tool for predicting hypotension (systolic pressure < 90 mmHg or a ≥ 30% drop from the baseline) was evaluated by ROC curve analysis.

RESULTS

A total of 83 patients were available for analysis, with 20 in the CI+ and 63 in the CI- group, we excluded 19 previously eligible patients due to inadequate visualization of the IVC (7 cases), lack of adherence to the protocol (8 cases), missing data (2 cases) or change in anesthesiologic management (2 cases). The mean decrease in systolic pressure in the CI+ group was 53.8 ± 15.3 compared to 35.8 ± 18.1 mmHg in CI- patients (P = 0.0001). The relative mean arterial pressure change medians were 34.1% (IQR 23.2-43.0%) and 24.2% (IQR 17.2-30.2%), respectively (P = 0.0029). The ROC curve analysis for IVCCI showed an AUC of 64.8% (95% CI 52.1-77.5%). The selected 50% level of the IVCCI had a sensitivity of only 45.5% (95% CI 28.1-63.7%), but the specificity was high at 90.0% (78.2-96.7%). The positive predictive value was 75.0% (95% CI 50.9-91.3%), and the negative predictive value was 71.4% (95% CI 58.7-82.1%).

CONCLUSION

In spontaneously breathing preoperative noncardiac surgical patients, preoperatively detected IVCCI≧50% can predict postinduction hypotension with high specificity but low sensitivity. Despite moderate performance, IVCCI is an easy, noninvasive and attractive option to identify patients at risk and should be explored further.

Approach of minimal invasive monitoring and initial treatment of the septic patient in emergency medicine

Sepsis and septic shock constitute a complex disease condition that requires the engagement of several medical specialties. A great number of patients with this disease are constantly admitted to the emergency department, which warrants the need for emergency physicians to lead in the recognition and early management of septic patients. Timely and appropriate interventions may help reduce mortality in a disease with an unacceptably high mortality rate. Poor control of cellular hypoperfusion is one of the most influential mechanisms contributing to the high mortality rate in these patients. This article aims to make an evidence-based approach and an algorithm for the active identification of hypoperfusion in patients with suspicion of severe infection, based on both clinical variables (capillary refill, mottling index, left ventricular function by ultrasound, temperature gradient, etc.) and laboratory-measured variables (lactate, central venous oxygen saturation [ScvO₂], and venous-to-arterial carbon dioxide tension difference [P (v-a) CO₂]). Such variables are feasible to use in the emergency department and would help to explain the cause behind the inadequate oxygen use by cells, thereby guiding treatment at the macrovascular, microvascular, or cellular level.