Does Respiratory Variation in Inferior Vena Cava Diameter Predict Fluid Responsiveness in Mechanically Ventilated Patients? A Systematic Review and Meta-analysis

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the older adults are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the older adults. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

Advances in Point-of-Care Ultrasound in Pediatric Acute Care Medicine

Pediatric point-of-care ultrasonography (POCUS) has grown in utilization and is now an integral part of pediatric acute care. Applications within the pediatric critical care, neonatology and pediatric emergency were once limited to evaluation of undifferentiated shock states, abdominal free fluid assessments in trauma resuscitation and procedural guidance. The body of pediatric POCUS literature is ever expanding and recently published international consensus guidelines are available to guide implementation into clinical practice. The authors present a review of emerging applications and controversies within thoracic, hemodynamic, neurologic, and ocular POCUS in pediatric acute care medicine.

Echocardiography in the Ventilated Patient: What the Clinician Has to Know

Heart and lung sharing the same anatomical space are influenced by each other. Spontaneous breathing induces dynamic changes in intrathoracic pressure, impacting cardiac function, particularly the right ventricle. In intensive care units (ICU), mechanical ventilation (MV) and therefore positive end-expiratory pressure (PEEP) are often applied, and this inevitably influences cardiac function. In ventilated patients, the use of positive pressures leads to an increase in intrathoracic pressure and, consequently, to a reduction in the right ventricular preload and thus cardiac output. The clinician working in the intensive care unit must be able to assess the effects MV has on the heart in order to set it up appropriately and to manage any complications. The echocardiographic evaluation of the ventilated patient has the main purpose of studying the right ventricle; in fact, they are the ones most affected by PEEP. It is therefore necessary to assess the size, thickness, and systolic function of the right ventricle. In the mechanically ventilated patient, it may be difficult to assess the volemic status and fluid responsiveness, in fact, the study of the inferior vena cava (IVC) is not always reliable in these patients. In patients with MV, it is preferable to assess fluid responsiveness with dynamic methods such as the end-expiration occlusion (EEO) test, passive leg raise (PLR), and fluid challenge (FC). The study of the diaphragm is also essential to identify possible complications, manage weaning, and provide important prognostic information. This review describes the basis for echocardiographic evaluation of the mechanically ventilated patient with the aim of supporting the clinician in managing the consequences of MV for heart-lung interaction.

Stroke volume variation induced by lung recruitment maneuver to predict fluid responsiveness in patients receiving mechanical ventilation: A systematic review and meta-analysis

STUDY OBJECTIVE

The aim of this study was to evaluate the accuracy of lung recruitment maneuver induced stroke volume variation (ΔSVLRM) in predicting fluid responsiveness in mechanically ventilated adult patients by systematic review and meta-analysis.

METHODS

A comprehensive electronic search of relevant literature was conducted in PubMed, Web of Science, Cochrane Library, Ovid Medline, Embase and Chinese databases (including China National Knowledge Infrastructure, Wanfang and VIP databases). Review Manager 5.4, Meta-DiSc 1.4 and STATA 16.0 were selected for data analysis, and QUADAS-2 tool was used for quality assessment. Data from selected studies were pooled to obtain sensitivity, specificity, diagnostic likelihood ratio (DLR) of positive and negative, diagnostic odds ratio (DOR), and summary receiver operating characteristic curve.

RESULTS

A total of 6 studies with 256 patients were enrolled through March 2024. The risk of bias and applicability concerns for each included study were low, and there was no significant publication bias. There was moderate to substantial heterogeneity for the non-threshold effect, but not for the threshold effect. The combined sensitivity and specificity were 0.84 (95% CI, 0.77-0.90) and 0.79 (95% CI, 0.70-0.86), respectively. The DOR and the area under the curve (AUC) were 22.15 (95%CI, 7.62-64.34) and 0.90 (95% CI, 0.87-0.92), respectively. The positive and negative predictive values of DLR were 4.53 (95% CI, 2.50-8.18) and 0.19 (95% CI, 0.11-0.35), respectively. Fagan's nomogram showed that with a pre-test probability of 52%, the post-test probability reached 83% and 17% for the positive and negative tests, respectively.

CONCLUSIONS

Based on the currently available evidence, ΔSVLRM has a good diagnostic value for predicting the fluid responsiveness in adult patients undergoing mechanical ventilation. Given the heterogeneity and limitations of the published data, further studies with large sample sizes and different clinical settings are needed to confirm the diagnostic value of ΔSVLRM in predicting fluid responsiveness. PROSPERO registration number: CRD42023490598.

BILL Strategy: Points to Consider During the Performance and Interpretation of Critical Care Echocardiography

The growing utilization of critical care echocardiography (CCE) by clinicians necessitates a meticulous review of clinical conditions in critically ill patients, both before and during the examination. The reviewing process of clinical conditions minimizes the risk of overlooking or misinterpreting crucial findings. This article proposes a comprehensive strategy, namely BILL strategy, to integrate into the CCE protocol, where "B" represents baseline respiratory and hemodynamic support, "I" signifies information gleaned from invasive monitoring, including central venous pressure and thermodilution-derived cardiac output, the first "L" denotes laboratory results such as central venous oxygen saturation, troponin, and brain natriuretic peptide, and the second "L" refers to lung ultrasound data. Combining the BILL strategy with CCE can enhance comprehensive understanding of critical conditions, potentially leading to improved diagnostic accuracy and patient outcomes.

Respiratory variation in the internal jugular vein does not predict fluid responsiveness in the prone position during adolescent idiopathic scoliosis surgery: a prospective cohort study

BACKGROUND

Respiratory variation in the internal jugular vein (IJVV) has not shown promising results in predicting volume responsiveness in ventilated patients with low tidal volume (Vt) in prone position. We aimed to determine whether the baseline respiratory variation in the IJVV value measured by ultrasound might predict fluid responsiveness in patients with adolescent idiopathic scoliosis (AIS) undergoing posterior spinal fusion (PSF) with low Vt.

METHODS

According to the fluid responsiveness results, the included patients were divided into two groups: those who responded to volume expansion, denoted the responder group, and those who did not respond, denoted the non-responder group. The primary outcome was determination of the value of baseline IJVV in predicting fluid responsiveness (≥15% increases in stroke volume index (SVI) after 7 ml·kg-1 colloid administration) in patients with AIS undergoing PSF during low Vt ventilation. Secondary outcomes were estimation of the diagnostic performance of pulse pressure variation (PPV), stroke volume variation (SVV), and the combination of IJVV and PPV in predicting fluid responsiveness in this surgical setting. The ability of each parameter to predict fluid responsiveness was assessed using a receiver operating characteristic curve.

RESULTS

Fifty-six patients were included, 36 (64.29%) of whom were deemed fluid responsive. No significant difference in baseline IJVV was found between responders and non-responders (25.89% vs. 23.66%, p = 0.73), and no correlation was detected between baseline IJVV and the increase in SVI after volume expansion (r = 0.14, p = 0.40). A baseline IJVV greater than 32.00%, SVV greater than 14.30%, PPV greater than 11.00%, and a combination of IJVV and PPV greater than 64.00% had utility in identifying fluid responsiveness, with a sensitivity of 33.33%, 77.78%, 55.56%, and 55.56%, respectively, and a specificity of 80.00%, 50.00%, 65.00%, and 65.00%, respectively. The area under the receiver operating characteristic curve for the baseline values of IJVV, SVV, PPV, and the combination of IJVV and PPV was 0.52 (95% CI, 0.38-0.65, p=0.83), 0.54 (95% CI, 0.40-0.67, p=0.67), 0.58 (95% CI, 0.45-0.71, p=0.31), and 0.57 (95% CI, 0.43-0.71, p=0.37), respectively.

CONCLUSIONS

Ultrasonic-derived IJVV lacked accuracy in predicting fluid responsiveness in patients with AIS undergoing PSF during low Vt ventilation. In addition, the baseline values of PPV, SVV, and the combination of IJVV and PPV did not predict fluid responsiveness in this surgical setting.

TRAIL REGISTRATION

This trial was registered at www.chictr.org (ChiCTR2200064947) on 24/10/2022. All data were collected through chart review.

THE ACCURACY OF INFERIOR VENA CAVA DISTENSIBILITY THROUGH THE TRANSHEPATIC APPROACH TO PREDICT FLUID RESPONSIVENESS IN PATIENTS WITH SEPTIC SHOCK AFTER EMERGENCY LAPAROTOMY

ABSTRACT

Background: We aimed to evaluate the ability of inferior vena cava (IVC) distensibility using the transhepatic approach to predict fluid responsiveness in mechanically ventilated patients with septic shock after emergency laparotomy. Methods: This prospective observational study included mechanically ventilated paralyzed adult who had septic shock after emergency laparotomy. The IVC dimensions were measured through the transhepatic and subxiphoid approaches. The fluid responsiveness was confirmed with >15% increase in cardiac output after 500 mL of fluid bolus. The outcomes were the ability of transhepatic (primary outcome) and subxiphoid approach to predict fluid responders using the area under the receiver operating characteristics curve analysis. The gray zone for the two approaches was calculated. Results: Data from 51 patients were analyzed, and the number of fluid responders was 30 of 52 (58%). The transhepatic approach was feasible in all patients, whereas the subxiphoid approach was only feasible in 42 patients. The area under the receiver operating characteristics curve (95% confidence interval) for the transhepatic IVC distensibility was 0.88 (0.76-0.95), and it was comparable with that of the subxiphoid approach (0.81 [0.66-0.92], P = 0.417). The gray zone for the transhepatic IVC distensibility was 17% to 35% including 24 of 51 patients (47%), whereas the gray zone for the subxiphoid IVC distensibility was 13% to 34% including 18 of 42 patients (43%). Conclusion: In conclusion, the transhepatic approach for evaluation of IVC distensibility showed good accuracy in predicting fluid responsiveness in patients with septic shock after emergency laparotomy. The transhepatic approach showed the same accuracy as the subxiphoid approach with the advantage of being feasible in larger number of patients.

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.

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the elderly are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the elderly. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

Point-of-care ultrasonography to predict fluid responsiveness in children: A systematic review and meta-analysis

BACKGROUND

Point-of-care ultrasonography (POCUS) is proposed as a valuable method for hemodynamic monitoring and several ultrasound-based predictors of fluid responsiveness have been studied. The main objective of this study was to assess the accuracy of these predictors in children.

METHODS

PubMed, Embase, Scopus, ClinicalTrials.gov, and Cochrane Library databases were searched for relevant publications through July 2022. Pediatric studies reporting accuracy estimates of ultrasonographic predictors of fluid responsiveness were included since they had used a standard definition of fluid responsiveness and had performed an adequate fluid challenge.

RESULTS

Twenty-three studies involving 1028 fluid boluses were included, and 12 predictors were identified. A positive response to fluid infusion was observed in 59.7% of cases. The vast majority of participants were mechanically ventilated (93.4%). The respiratory variation in aortic blood flow peak velocity (∆Vpeak) was the most studied predictor, followed by the respiratory variation in inferior vena cava diameter (∆IVC). The pooled sensitivity and specificity of ∆Vpeak were 0.84 (95% CI, 0.76-0.90) and 0.82 (95% CI, 0.75-0.87), respectively, and the area under the summary receiver operating characteristic curve (AUSROC) was 0.89 (95% CI, 0.86-0.92). The ∆IVC presented a pooled sensitivity and specificity of 0.79 (95% CI, 0.62-0.90) and 0.70 (95% CI, 0.51-0.84), respectively, and an AUSROC of 0.81 (95% CI, 0.78-0.85). Significant heterogeneity in accuracy estimates across studies was observed.

CONCLUSIONS

POCUS has the potential to accurately predict fluid responsiveness in children. However, only ∆Vpeak was found to be a reliable predictor. There is a lack of evidence supporting the use of POCUS to guide fluid therapy in spontaneously breathing children.

Accuracy of echocardiography and ultrasound protocol to identify shock etiology in emergency department

Background

Early diagnosis and appropriate management of shock aimed at prevention of prolonged hypoperfusion has shown to decrease morbidity and mortality in patients with undifferentiated shock. However, there is often a challenge in emergency department (ED) – where diagnosis is mainly based on clinical signs and standard monitoring parameters. Early use of point of care ultrasound could reduce the diagnostic time and improve diagnostic accuracy.

Purpose

The aim of this study is to investigate the accuracy of echocardiography - ultrasound protocol to identify the cause of shock in ED.

Method

The study was conducted on 150 shocked patients admitted to emergency department of Alexandria Main University Hospital from December 2018 to December 2020. The study was conducted to reach initial impression about shock etiology which was then compared to final diagnosis to determine accuracy, agreement, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).

Results

One hundred forty patients were included in the study (10 patients were excluded). The protocol was 100% accurate for diagnosing cases with obstructive and mixed obstructive distributive shock. It showed excellent rule- out characteristics for cardiogenic shock (sensitivity and NPV = 100%). There was almost perfect agreement between provisional and final shock type for mixed distributive cardiogenic shock (kappa 0.915). Echo- US protocol had lowest agreement and PPV for patients with hypovolemic shock Kappa 0.48 and 35% respectively.

Conclusion

The Echo- US protocol showed a high accuracy in identifying shock etiology in ED and is likely a promising diagnostic tool in emergency care.

Different preoperative fluids do not affect the hemodynamic status but gastric volume: results of a randomized crossover pilot study

Background and objective

Inferior vena cava (IVC) examination has been reported as a noninvasive method for evaluating the hemodynamic state. We conducted this crossover pilot study to investigate the effects of the administration of water and high-carbohydrate-containing fluids on the hemodynamic status of volunteers through collapsibility index of IVC (IVCCI) measurement.

Methods

Twenty volunteers were randomly assigned to a water or high-carbohydrate group according to computer-generated random numbers in a 1:1 ratio. In the water group, volunteers received water (5 mL/kg), and in the high-carbohydrate group, patients received carbohydrate drinks (5 mL/kg). Respiratory variations in the IVC diameter, gastric volume, and blood pressure and heart rates in erect and supine positions were measured at admission (T1), 1 h (T2), 2 h (T3), 3 h (T4), and 4 h (T5).

Results

When considering participants with an IVCCI of more than 42%, there were no significant differences between the water and carbohydrate drink groups at each time point (all p > 0.05). At T2, more participants had an empty stomach in water group than in carbohydrate drink group (p < 0.001). At T3, 30% of the participants could not empty their stomachs in carbohydrate drink group. However, with regard to the number of volunteers with empty stomach at T3, there was no significant difference between water and carbohydrate drink group. Repeated measures data analysis demonstrated that IVCCI showed no significant differences over time (p = 0.063 for T1-T5). There were no differences between water and carbohydrate drinks (p = 0.867).

Conclusion

Our results suggested that neither water nor carbohydrate drinking affected the hemodynamic status through IVCCI measurement over time, up to 4 h after drinking. Furthermore, carbohydrate drinking might delay gastric emptying at 1 h, but not 2 h after drinking, in comparison with water.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01697-3.

Ultrasound assessment of the inferior vena cava in children: A comparison of sub-xiphoid and right lateral coronal views

OBJECTIVES

The inferior vena cava collapsibility index (IVCCI) has been used to assess the respiratory variation of the inferior vena cava (IVC) diameter and hence intravascular volume. The sub-xiphoid view (SXV) is the standard view to evaluate the IVC. The right lateral transabdominal view (RLV) has been shown in adults to be an alternative view to evaluate the IVC when the SXV is not feasible. The aim of the study was to compare IVC dimensions from these two views and thus determine whether the RLV view can be used instead of the SXV in pediatric patients.

METHODS

We conducted a single-center prospective observational crossover study. Study subjects were ASA physical status 1-2 children, 1-12 years of age scheduled for elective surgery under general anesthesia. Anesthesia was maintained by mask with spontaneous ventilation with end-tidal sevoflurane at 2%-5% after the induction of anesthesia. IVCCI was measured using M-mode in both the SXV and RLV.

RESULTS

The study cohort included 50 children with a mean age of 5.1 years. The median value for the IVCCI-sx was 0.45 (IQR: 0.28-0.70) while the IVCCI-rl was 0.30 (0.19-0.5). The mean difference between the two groups was 0.12 (95% CI: 0.177-0.066, p < .001, two-tailed paired t-test). Spearman's rank correlation coefficient was 0.66. The univariate linear regression model was IVCCIsx = 0.21 + 0.77 × IVCCIrl.

CONCLUSIONS

IVCCIrl was lower than IVCCIsx. IVCCI measured from the right lateral view tended to overestimate the patient's fluid-responsiveness and therefore these two values are not interchangeable.

Respiratory-Cardiovascular Interactions During Mechanical Ventilation: Physiology and Clinical Implications

Positive-pressure inspiration and positive end-expiratory pressure (PEEP) increase pleural, alveolar, lung transmural, and intra-abdominal pressure, which decrease right and left ventricular (RV; LV) preload and LV afterload and increase RV afterload. The magnitude and clinical significance of the resulting changes in ventricular function are determined by the delivered tidal volume, the total level of PEEP, the compliance of the lungs and chest wall, intravascular volume, baseline RV and LV function, and intra-abdominal pressure. In mechanically ventilated patients, the most important, adverse consequences of respiratory-cardiovascular interactions are a PEEP-induced reduction in cardiac output, systemic oxygen delivery, and blood pressure; RV dysfunction in patients with ARDS; and acute hemodynamic collapse in patients with pulmonary hypertension. On the other hand, the hemodynamic changes produced by respiratory-cardiovascular interactions can be beneficial when used to assess volume responsiveness in hypotensive patients and by reducing dyspnea and improving hypoxemia in patients with cardiogenic pulmonary edema. Thus, a thorough understanding of the physiological principles underlying respiratory-cardiovascular interactions is essential if critical care practitioners are to anticipate, recognize, manage, and utilize their hemodynamic effects. © 2022 American Physiological Society. Compr Physiol 12:1-24, 2022.

Inferior Vena Cava Edge Tracking Echocardiography: A Promising Tool with Applications in Multiple Clinical Settings

Ultrasound (US)-based measurements of the inferior vena cava (IVC) diameter are widely used to estimate right atrial pressure (RAP) in a variety of clinical settings. However, the correlation with invasively measured RAP along with the reproducibility of US-based IVC measurements is modest at best. In the present manuscript, we discuss the limitations of the current technique to estimate RAP through IVC US assessment and present a new promising tool developed by our research group, the automated IVC edge-to-edge tracking system, which has the potential to improve RAP assessment by transforming the current categorical classification (low, normal, high RAP) in a continuous and precise RAP estimation technique. Finally, we critically evaluate all the clinical settings in which this new tool could improve current practice.

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.

Carotid vs aortic velocity time integral and peak velocity to predict fluid responsiveness in mechanically ventilated patients. A comparative study

BACKGROUND

The carotid artery velocity-time integral (CVTI) and the carotid Doppler peak velocity (cDPV), as well as measures of their variation induced by the respiratory cycle, have been proposed as fast and easy to obtain ultrasound measures for assessing fluid responsiveness in intensive care unit patients. To investigate this possibility, we conducted a prospective observational study in hemodynamically unstable patients under mechanical ventilation.

METHODS

From May 1 to December 31, 2019, we conducted a prospective observational study involving 50 hemodynamically unstable patients under mechanical ventilation. We obtained a total of 800 Doppler ultrasound measurements from the left common carotid artery and at the level of the aortic annulus in the apical five-chamber view. The two measurements were performed before and after a 7 mL/kg fluid challenge and within the first hour of the onset of hemodynamic instability. The maximum Doppler peak velocity, the minimum Doppler peak velocity, and the maximum and minimum VTI at both the aortic and carotid level were acquired.

RESULTS

Twenty-eight (56%) patients showed a ≥15% increase in AoVTI after the fluid challenge, and were therefore identified as "fluid responders". All Doppler measurements were always significantly greater (p <0.0001) in fluid responders in relation to both carotid and aortic parameters. Good agreement between the above-mentioned measurements was found: Cohen's kappa coefficient between the carotid and aortic ΔDPV was 0.76 (95% CI 0.58 - 0.94); and between the Carotid and Aortic ΔVTI it was 0.84 (95% CI 0.68 - 0.99).

CONCLUSIONS

CDPV was found to predict fluid responsiveness in unstable mechanically ventilated patients.

Point-of-care ultrasound assessment of the inferior vena cava distensibility index in mechanically ventilated children in the operating room

Background and aim

Point-of-care ultrasound imaging of the inferior vena cava distensibility index is a potential indicator for determining fluid overload and dehydration in the mechanically ventilated patients. Data on inferior vena cava distensibility index and inferior vena cava distensibility variability are limited in mechanically ventilated pediatric patients. That is why our aim in this study was to measure inferior vena cava distensibility index and to obtain mean values in pediatric patients, ventilated in the operating room before the ambulatory surgical procedure started.

Materials and methods

This crosssectional study was performed between February 2019 and February 2020. Ultrasonographic measurements were performed in a total of 125 children.

Results

In a period of 13 months, the measurements were performed in a total of 125 children, of which 120 (62.5% male) met the criteria and were included in the study. Overall inferior vena cava distensibility index (%): mean ± SD: 6.8 ± 4.0, median (min–max): 5.7 (1.4–19.6), IQR: 3.8–8.7. Overall inferior vena cava distensibility variability (%): mean ± SD: 6.5 ± 3.7, median (min–max): 5.5 (1.4–17.8), IQR: 3.7–8.4.

Conclusion

Our study is the largest series of children in the literature in which inferior vena cava distensibility index measurements were investigated.

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.

Respiratory variability of inferior vena cava at different mechanical ventilator settings

BACKGROUND

Assessment of the respiratory changes of the inferior vena cava (IVC) diameter have been investigated as a reliable tool to estimate the volume status in mechanically ventilated and spontaneously breathing patients. Our purpose was to compare the echocardiographic measurements the IVC diameter, stroke volume and cardiac output in different positive pressure ventilation parameters.

METHODS

This prospective clinical study with crossover design was conducted in the Intensive Care Unit (ICU). Twenty-five sedated, paralyzed, intubated, and mechanically ventilated patients with volume control mode (CMV) in the ICU due to respiratory failure were included in the study. Positive End-Expiratory Pressure (PEEP) and Tidal Volume (TV) were changed in each patient consecutively (Group A: TV 6 ml/kg, PEEP 5 cmH20, B: TV 6, PEEP 8, C: TV 8, PEEP 5, D: TV 8, PEEP 8) and the changes in vital parameters, central venous pressure (CVP) and ultrasonographic changes in IVC and cardiac parameters were measured. All measures were compared between groups by robust repeated measures ANOVA with trimmed mean.

RESULTS

The respiratory changes of the IVC diameter and echocardiographic parameters showed no significant difference in separate mechanical ventilator settings. Significant difference was found in peak and plateau pressure values among groups (p < 0.05).

CONCLUSION

The results of our study suggest that IVC related parameters are not affected with different ventilatory settings. Further studies are needed to confirm the reliability of these parameters as a predictor of fluid assessment.

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.

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.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparative Analysis of the Collapsibility Index and Distensibility Index of the Inferior Vena Cava Through Echocardiography with Pulse Pressure Variation That Predicts Fluid Responsiveness in Surgical Patients: An Observational Controlled Trial

OBJECTIVE

The objective for the present study was to compare the collapsibility (IcIVC) and distensibility (IdIVC) indices of the inferior vena cava with pulse pressure variation (PPV) and determine the accuracy and cutoff points of IcIVC and IdIVC that best predict response to intravenous fluid therapy in surgical patients.

DESIGN

Observational, prospective, nonblinded, single center.

SETTING

Hospital do Servidor Público Estadual de São Paulo, in São Paulo, Brazil.

PARTICIPANTS

Volunteer surgical patients.

INTERVENTIONS

This prospective study evaluated adult surgical patients before and after they underwent mechanical ventilation. IcIVC and IdIVC measurements were obtained with echocardiography and PPV through arterial catheterization.

MEASUREMENTS AND MAIN RESULTS

Twenty-two patients with a mean age of 55.7 ± 10.9 years were included; 31.8% of the study participants had PPV values >13% and were shown to be responsive to fluid. A good correlation was detected between PPV and icIVC (R² = 0.71; p < 0.001) and between PPV and idIVC (R² = 0.79; p < 0.001). The area under the receiver operating characteristic curve was 0.98 for icIVC (95% confidence interval 0.81-0.99; p < 0.001) and 0.88 for idIVC (95% confidence interval 0.67-0.98; p < 0.001).

CONCLUSIONS

PPV was found to have good correlation with the inferior vena cava diameter variation using echocardiography in surgical patients undergoing spontaneous and artificial ventilation. The cutoff values that best predicted PPV >13% were >40% for icIVC and >17.6% for idIVC.

Value of respiratory variation of aortic peak velocity in predicting children receiving mechanical ventilation: a systematic review and meta-analysis

Background

Accurate volume assessment is crucial in children under fluid therapy. Over the last decade, respiratory variation of aortic peak velocity (△VPeak) has been applied in intensive care unit and surgeries to help clinicians guide fluid management. The aim of this systematic review and meta-analysis was to test diagnostic performance of △VPeak in predicting fluid responsiveness of ventilated children and to explore the potential factors that influence the accuracy of △VPeak.

Methods

We searched PubMed, Embase, and Cochrane from inception to April 2019 that evaluated association between △VPeak and fluid responsiveness after fluid challenge in children receiving mechanical ventilation. Data synthesis was performed within the bivariate mixed-effects regression model modified for synthesis of diagnostic test data.

Results

Eleven studies with a total of 302 pediatric patients were included in our meta-analysis. The pooled sensitivity and specificity of △VPeak was 0.89 (95%CI = 0.77 to 0.95) and 0.85 (95%CI = 0.77 to 0.91), respectively. The diagnostic odds ratio (DOR) of △VPeak was 48 (95%CI = 15 to 155). SROC yielded an area under the curve of 0.91 (95%CI = 0.88–0.93). The △VPeak cutoff value was nearly conically symmetrical distribution and varied from 7 to 20%. After excluding several extreme studies, most data were centered between 12 and 13%. The medium and mean cutoff values of △VPeak were 12.2% and 12.7%, respectively. In subgroup analysis, compared to total data analysis, △VPeak performed weaker in the younger children group (mean ages < 25 months), with lower area under the summary receiver operating characteristic curve (AUSROC) of 0.80 (0.76 to 0.83), but stronger in the older children group (mean ages > 25 months), with AUSROC of 0.96 (0.94 to 0.97).

Conclusions

Overall, △VPeak has a good ability in predicting fluid responsiveness of children receiving mechanical ventilation, but this ability decreases in younger children (mean age < 25 months). The optimal threshold of △VPeak to predict fluid responsiveness in ventilated children is reliable between 12 and 13%.

Trial registration

The study protocol was registered prospectively on PROSPERO no. CRD42019129361.

Respiratory variations of inferior vena cava fail to predict fluid responsiveness in mechanically ventilated patients with isolated left ventricular dysfunction

Background

Respiratory variation of inferior vena cava is problematic in predicting fluid responsiveness in patients with right ventricular dysfunction. However, its effectiveness in patients with isolated left ventricular systolic dysfunction (ILVD) has not been reported. We aimed to explore whether inferior vena cava diameter distensibility index (dIVC) can predict fluid responsiveness in mechanically ventilated ILVD patients.

Methods

Patients admitted to the intensive care unit who were on controlled mechanical ventilation and in need of a fluid responsiveness assessment were screened for enrolment. Several echocardiographic parameters, including dIVC, tricuspid annular plane systolic excursion (TAPSE), left ventricular ejection fraction (LVEF), and LV outflow tract velocity–time integral (VTI) before and after passive leg raising (PLR) were collected. Patients with LV systolic dysfunction only (TAPSE ≥ 16 mm, LVEF < 50%) were considered to have isolated left ventricular systolic dysfunction (ILVD).

Results

One hundred and twenty-nine subjects were enrolled in this study, among them, 28 were labelled ILVD patients, and the remaining 101 were patients with normal LV function (NLVF). The value of dIVC in ILVD patients was as high as that in NLVF patients, (20% vs. 16%, p = 0.211). The ILVD group contained a much lower proportion of PLR responders than NLVF patients did (17.9% vs. 53.2%, p < 0.001). No correlation was detected between dIVC and ΔVTI in ILVD patients (r = 0.196, p = 0.309). dIVC was correlated with ΔVTI in NLVF patients (r = 0.722, p < 0.001), and the correlation was strengthened compared with that derived from all patients (p = 0.020). A receiver-operating characteristic (ROC) analysis showed that the area-under-the-curve (AUC) of dIVC for determining fluid responsiveness from ILVD patients was not statistically significant (p = 0.251). In NLVF patients, ROC analysis revealed an AUC of 0.918 (95% CI 0.858–0.978; p < 0.001), which was higher than the AUC derived from all patients (p = 0.033). Patients with LVEF below 40% had a lower ΔVTI and fewer PLR responders than those with LVEF 40–50% and LVEF above 50% (p < 0.001).

Conclusion

dIVC should be used with caution when critically ill patients on controlled mechanical ventilation display normal right ventricular function in combination with abnormal left ventricular systolic function.

Fluid responsiveness in the pediatric population

It is challenging to predict fluid responsiveness, that is, whether the cardiac index or stroke volume index would be increased by fluid administration, in the pediatric population. Previous studies on fluid responsiveness have assessed several variables derived from pressure wave measurements, plethysmography (pulse oximeter plethysmograph amplitude variation), ultrasonography, bioreactance data, and various combined methods. However, only the respiratory variation of aortic blood flow peak velocity has consistently shown a predictive ability in pediatric patients. For the prediction of fluid responsiveness in children, flow- or volume-dependent, noninvasive variables are more promising than pressure-dependent, invasive variables. This article reviews various potential variables for the prediction of fluid responsiveness in the pediatric population. Differences in anatomic and physiologic characteristics between the pediatric and adult populations are covered. In addition, some important considerations are discussed for future studies on fluid responsiveness in the pediatric population.

Evaluation of volume responsiveness by pulse pressure variability and inferior vena cava dispensability index at different tidal volumes by mechanical ventilation

This study investigated the effects of tidal volume (TV) on the diagnostic value of pulse pressure variation (PPV) and the inferior vena cava dispensability index (IVC-DI) for volume responsiveness during mechanical ventilation. In patients undergoing elective surgery with mechanical ventilation, different TVs of 6, 9, and 12 mL/kg were given for two min. The left ventricular outflow tract velocity-time integral (VTI) was measured by transthoracic echocardiography. The IVC-DI was measured at sub-xyphoid transabdominal long axis. The PPV was measured via the radial artery and served as baseline. Index measurements were repeated after fluid challenge. VTI increased by more than 15% after fluid challenge, which was considered as volume responsive. Seventy-nine patients were enrolled, 38 of whom were considered positive volume responsive. Baseline data between the response group and the non-response group were similar. Receiver operating characteristic curve confirmed PPV accuracy in diagnosing an increase in volume responsiveness with increased TV. When TV was 12 mL/kg, the PPV area under the curve (AUC) was 0.93 and the threshold value was 15.5%. IVC-DI had the highest diagnostic accuracy at a TV of 9 mL/kg and an AUC of 0.79, with a threshold value of 15.3%. When TV increased to 12 mL/kg, the IVC-DI value decreased. When the TV was 9 and 12 mL/kg, PPV showed improved performance in diagnosing volume responsiveness than did IVC-DI. PPV diagnostic accuracy in mechanically ventilated patients was higher than IVC-DI. PPV accuracy in predicting volume responsiveness was increased by increasing TV.

Resuscitative Cardiopulmonary Ultrasound and Transesophageal Echocardiography in the Emergency Department

Resuscitative ultrasound describes point-of-care applications that provide diagnostic information, physiologic monitoring, and procedural guidance in critically ill patients. This article reviews the evaluation of ventricular function, identification of pericardial effusion and tamponade, evaluation of preload and fluid responsiveness, and hemodynamic monitoring, as some of the main applications where this modality can help emergency physicians during resuscitation of critically ill patients.