Variability in the Physiologic Response to Fluid Bolus in Pediatric Patients Following Cardiac Surgery

Accuracy of Respiratory Variation in Inferior Vena Cava Diameter to Predict Fluid Responsiveness in Children Under Mechanical Ventilation

Proper assessment of fluid responsiveness using accurate predictors is crucial to guide fluid therapy and avoid the serious adverse effects of fluid overload. The main objective of this study was to investigate the accuracy of respiratory variations in inferior vena cava diameter (∆IVC) to predict fluid responsiveness in mechanically ventilated children. This prospective single-center study included 32 children (median age and weight of 17 months and 10 kg, respectively) who received a fluid infusion of 10 ml kg-1 of crystalloid solutions over 10 min. ∆IVC and respiratory variation in aortic blood flow peak velocity (∆Vpeak) were determined over one controlled respiratory cycle before and after fluid loading. Thirteen (41%) participants were fluid-responders. ∆IVC, ∆Vpeak, stroke volume index, and cardiac index were found to be predictors of fluid responsiveness. However, the area under the ROC curve of ∆IVC was smaller when compared to ∆Vpeak (0.709 vs. 0.935, p < 0.012). The best cut-off values were 7.7% for ∆IVC (sensitivity, 69.2%; specificity 78.9%, positive predictive value, 69.2%; and negative predictive value, 78.9%) and 18.2% for ∆Vpeak (sensitivity, 84.6%; specificity, 89.5%; positive predictive value, 84.6%; negative predictive value, 89.5%). Changes in stroke volume were positively correlated with ∆IVC (ρ = 0.566, p < 0.001) and ∆Vpeak (ρ = 0.603, p < 0.001). A significant correlation was also found between changes in MAP and ∆Vpeak (ρ = 0.382; p = 0.031), but the same was not observed with ∆IVC (ρ = 0.011; p = 0.951). In conclusion, ∆IVC was found to have a moderate accuracy in predicting fluid responsiveness in mechanically ventilated children and is an inferior predictor when compared to ∆Vpeak.

Physiological changes after fluid bolus therapy in cardiac surgery patients: A propensity score matched case-control study

Objective

Fluid bolus therapy (FBT) is ubiquitous in intensive care units (ICUs) after cardiac surgery. However, its physiological effects remain unclear.

Design

: We performed an electronic health record-based quasi-experimental ICU study after cardiac surgery. We applied propensity score matching and compared the physiological changes after FBT episodes to matched control episodes where despite equivalent physiology no fluid bolus was given.

Setting

The study was conducted in a multidisciplinary ICU of a tertiary-level academic hospital.

Participants

The study included 2,736 patients who underwent Coronary Artery Bypass Grafting and/or heart valve surgery.

Main Outcome Measures

Changes in cardiac output (CO) and mean arterial pressure (MAP) during the 60 minutes following FBT.

Results

We analysed 3572 matched fluid bolus (FB) episodes. After FBT, but not in control episodes, CO increased within 10 min, with a maximum increase of 0.2 l/min (95%CI 0.1 to 0.2) or 4% above baseline at 40 min (p < 0.0001 vs. controls). CO increased by > 10% from baseline in 60.6% of FBT and 49.1% of control episodes (p < 0.0001). MAP increased by > 10% in 51.7% of FB episodes compared to 53.4% of controls. Finally, FBT was not associated with changes in acid-base status or oxygen delivery.

Conclusion

In this quasi-experimental comparative ICU study in cardiac surgery patients, FBT was associated with statistically significant but numerically small increases in CO. Nearly half of FBT failed to induce a positive CO or MAP response.

Performance of Tools and Measures to Predict Fluid Responsiveness in Pediatric Shock and Critical Illness: A Systematic Review and Meta-Analysis

OBJECTIVES

In this systematic review and meta-analysis we asked: Do predictors of fluid responsiveness in children perform comparably: 1) in the PICU as in non-PICU settings? 2) in shock states compared with nonshock states? Additionally, 3) is there an association between preload responsiveness and clinical response?

DATA SOURCES

Ovid Medline, PubMed, and Embase databases were searched from inception through May 2022.

STUDY SELECTION

Included studies reported physiological response to IV fluid administration in humans less than 18 years. Only studies reporting an area under the receiver operating characteristic curve (AUROC) were included for descriptive analysis. Only studies for which a se could be estimated were included for meta-analysis.

DATA EXTRACTION

Title, abstract, full text screening, and extraction were completed by two authors (S.B.W., J.M.W.). Variables extracted included predictors ("tools") and outcome measures ("reference tests") of fluid responsiveness, demographic, and clinical variables.

DATA SYNTHESIS

We identified 62 articles containing 204 AUROCs for 55 tools, primarily describing mechanically ventilated children in an operating room or PICU. Meta-analysis across all tools showed poor predictive performance (AUROC, 0.66; 95% CI, 0.63-0.69), although individual performance varied greatly (range, 0.49-0.87). After controlling for PICU setting and shock state, PICU setting was associated with decreased predictive performance (coefficient, -0.56; p = 0.0007), while shock state was associated with increased performance (0.54; p = 0.0006). Effect of PICU setting and shock state on each tool was not statistically significant but analysis was limited by sample size. The association between preload responsiveness and clinical response was rarely studied but results did not suggest an association. Ultrasound measurements were prone to inherent test review and incorporation biases.

CONCLUSIONS

We suggest three opportunities for further research in fluid responsiveness in children: 1) assessing predictive performance of tools during resuscitation in shock states; 2) separating predictive tool from reference test when using ultrasound techniques; and 3) targeting decreasing time in a shock state, rather than just increase in preload.

Cardiac output monitoring in children: a review

Cardiac output monitoring enables physiology-directed management of critically ill children and aids in the early detection of clinical deterioration. Multiple invasive techniques have been developed and have demonstrated ability to improve clinical outcomes. However, all require invasive arterial or venous catheters, with associated risks of infection, thrombosis and vascular injury. Non-invasive monitoring of cardiac output and fluid responsiveness in infants and children is an active area of interest and several proven techniques are available. Novel non-invasive cardiac output monitors offer a promising alternative to echocardiography and have proven their ability to influence clinical practice. Assessment of perfusion remains a challenge; however, technologies such as near-infrared spectroscopy and photoplethysmography may prove valuable clinical adjuncts in the future.

Fluid bolus administration in children, who responds and how? A systematic review and meta-analysis

BACKGROUND

Fluid boluses are frequently utilized in children. Despite their frequency of use, there is little objective data regarding the utility of fluid boluses, who they benefit the most, and what the effects are.

AIMS

This study aimed to conduct pooled analyses to identify those who may be more likely to respond to fluid boluses as well as characterize clinical changes associated with fluid boluses.

METHODS

A systematic review of the literature and meta-analysis was conducted to identify pediatric studies investigating the response to fluid boluses and clinical changes associated with fluid boluses.

RESULTS

A total of 15 studies with 637 patients were included in the final analyses with a mean age of 650 days ± 821.01 (95% CI 586 to 714) and a mean weight of 10.5 kg ± 7.19 (95% CI 9.94 to 11.1). The mean bolus volume was 12.14 ml/kg ± 4.09 (95% CI 11.8 to 12.5) given over a mean of 19.55 min ± 10.16 (95% CI 18.8 to 20.3). The following baseline characteristics were associated with increased likelihood of response [represented in mean difference (95% CI)]: greater age [207.2 days (140.8 to 273.2)], lower cardiac index [-0.5 ml/min/m² (-0.9 to -0.3)], and lower stroke volume [-5.1 ml/m² (-7.9 to -2.3)]. The following clinical parameters significantly changed after a fluid bolus: decreased HR [-5.6 bpm (-9.8 to -1.3)], increased systolic blood pressure [7.7 mmHg (1.0 to 14.4)], increased mean arterial blood pressure [5.5 mmHg (3.1 to 7.8)], increased cardiac index [0.3 ml/min/m² (0.1 to 0.6)], increased stroke volume [4.3 ml/m² (3.5 to 5.2)], increased central venous pressure [2.2 mmHg (1.1 to 3.3)], and increased systemic vascular resistance [2.1 woods units/m² (0.1 to 4.2)].

CONCLUSION

Fluid blouses increase arterial blood pressure or cardiac output by 10% in approximately 56% of pediatric patients. Fluid blouses lead to significant decrease in HR and significant increases in cardiac output, stroke volume, and systemic vascular resistance. Limited published data are available on the effects of fluid blouses on systemic oxygen delivery.

Carotid doppler ultrasonography as a method to predict fluid responsiveness in mechanically ventilated children

AIMS

The aim of this study was to investigate whether respiratory variations in carotid and aortic blood flows measured by Doppler ultrasonography could accurately predict fluid responsiveness in critically ill children.

METHODS

This was a prospective single-center study including mechanically ventilated children who underwent fluid replacement at the discretion of the attending physician. Response to fluid load was defined by a stroke volume increase of more than 15%. Maximum and minimum values of velocity peaks were determined over one controlled respiratory cycle before and after volume expansion. Respiratory changes in velocity peak of the carotid (∆Vpeak_Ca) and aortic (∆Vpeak_Ao) blood flows were calculated as the difference between the maximum and minimum values divided by the mean of the two values and were expressed as a percentage.

RESULTS

A total of 30 patients were included, of which twelve (40%) were fluid responders and 18 (60%) non-responders. Before volume expansion, both ∆Vpeak_Ca and ∆Vpeak_Ao were higher in responders than in non-responders (17.1% vs 4.4%; p < .001 and 22.8% vs 6.4%; p < .001, respectively). ∆Vpeak_Ca could effectively predict fluid responsiveness (AUC 1.00, 95% CI 0.88-1.00), as well as ∆Vpeak_Ao (AUC 0.94, 95% CI 0.80-0.99). The best cutoff values were 10.6% for ∆Vpeak_Ca (sensitivity, specificity, positive predictive value and negative predictive value of 100%) and 18.2% for ∆Vpeak_Ao (sensitivity, 91.7%; specificity, 88.9%; positive predictive value, 84.6%; negative predictive value, 94.1%). Volume expansion-induced changes in stroke volume correlated with the ∆Vpeak_Ca and ∆Vpeak_Ao before volume expansion (ρ of 0.70 and 0.61, respectively; p < .001 for both).

CONCLUSIONS

Analysis of respiratory changes in carotid and aortic blood flows are accurate methods for predicting fluid responsiveness in children under invasive mechanical ventilation.

The physiologic responses to a fluid bolus administration in old and young healthy adults

BACKGROUND

Organ function is known to decline with age. Optimizing cardiac, pulmonary and renal function in older adults has led to significant improvements in perioperative care. However, when substantial blood loss and fluid shifts occur, perioperative outcomes still remains poor, especially in older adults. We suspect that this could be due to age-related changes in endothelial function-an organ controlling the transport of fluid and solutes. The capillary filtration coefficient (CFC) is an important determinant of fluid transport. The CFC can be measured in vivo, which provides a tool to estimate endothelial barrier function. We have previously shown that the CFC increases when giving a fluid bolus resulting in increased vascular and extravascular volume expansion, in young adults. This study aimed to compare the physiologic determinants of fluid distribution in young versus older adults so that clinicians can best optimize perioperative fluid therapy.

METHODS

Ten healthy young volunteers (ages 21-35) and nine healthy older volunteers (ages 60-75) received a 10 mL/kg fluid bolus over the course of twenty minutes. Hemodynamics, systolic and diastolic heart function, fluid volumetrics and microcirculatory determinants were measured before, during, and after the fluid bolus.

RESULTS

Diastolic function was reduced in older versus younger adults before and after fluid bolus (P < 0.01). Basal CFC and plasma oncotic pressure were lower in the older versus younger adults. Further, CFC did not increase in older adults following the fluid bolus, whereas it did in younger adults (p < 0.05). Cumulative urinary output, while lower in older adults, was not significantly different (p = 0.059). Mean arterial pressure and systemic vascular resistance were elevated in the older versus younger adults (p < 0.05).

CONCLUSION

Older adults show a less reactive CFC to a fluid bolus, which could reduce blood to tissue transport of fluid. Diastolic dysfunction likely contributes to fluid maldistribution in older adults.

BESTFIT-T3: A Tiered Monitoring Approach to Persistent/Recurrent Paediatric Septic Shock - A Pilot Conceptual Report

Objective

Persistent shock (PS) or recurrent shock (RS) after initial fluids and vasoactives can be secondary to myriad complex mechanisms, and these patients can have a high mortality. We developed a noninvasive tiered hemodynamic monitoring approach which included, in addition to basic echocardiography, cardiac output monitoring and advanced Doppler studies to determine the etiology and provide targeted therapy of PS/RS.

Design

Prospective observational study.

Setting

Tertiary Care Pediatric Intensive Care Unit, India.

Methods

A pilot conceptual report describing the clinical presentation of 10 children with PS/RS using advanced ultrasound and noninvasive cardiac output monitoring. Children with PS/RS after initial fluids and vasoactive agents despite basic echocardiography underwent BESTFIT + T3 (Basic Echocardiography in Shock Therapy for Fluid and Inotrope Titration) with lung ultrasound and advanced 3-tiered monitoring (T1-3).

Results

Among 10/53 children with septic shock and PS/RS over a 24-month study period, BESTFIT + T3 revealed combinations of right ventricular dysfunction, diastolic dysfunction (DD), altered vascular tone, and venous congestion (VC). By integrating information obtained by BESTFIT + T1-3 and the clinical context, we were able to modify the therapeutic regimen and successfully reverse shock in 8/10 patients.

Conclusion

We present our pilot results with BESTFIT + T3, a novel approach that can noninvasively interrogate major cardiac, arterial, and venous systems that may be particularly useful in regions where expensive rescue therapies are out of reach. We suggest that, with practice, intensivists already experienced in bedside POCUS can use the information obtained by BESTFIT + T3 to direct time-sensitive precision cardiovascular therapy in persistent/recurrent pediatric septic shock.

How to cite this article

Natraj R, Ranjit S. BESTFIT-T3: A Tiered Monitoring Approach to Persistent/Recurrent Paediatric Septic Shock - A Pilot Conceptual Report. Indian J Crit Care Med 2022;26(7):863-870.

Characteristics and Physiologic Changes After 4% Albumin Fluid Boluses in a PICU

OBJECTIVES

To describe the characteristics, hemodynamic, and physiologic changes after 4% albumin fluid boluses in critically ill children.

DESIGN

Retrospective observational study.

SETTING

Single-center PICU.

PATIENTS

Children in a cardiac and general PICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Between January 2017 and May 2019, there were 1,003 fluid boluses of 4% albumin during 420 of 5,731 admissions (7.8%), most commonly in children with congenital/acquired heart disease (71.2%) and sepsis (7.9%). The median fluid bolus dose was 10 mL/kg (interquartile range, 5.8-14.6 mL/kg), and its duration 30 minutes (interquartile range, 14.0-40.0 min; n = 223). After the fluid bolus, a significant change in mean arterial pressure (2.3 mm Hg [5.1%], 2.7 mm Hg [5.8%], 2.9 mm Hg [6.1%], and 3.8 mm Hg [8.0%] at 1, 2, 3, and 4 hr, respectively [p ≤ 0.001]) only occurred in children less than or equal to 12 months old. A mean arterial pressure response, defined by an increase greater than or equal to 10% from baseline, occurred in 290 of 887 patients (33%) with maximal response at 1 hour. Hypotension at baseline predicted the magnitude of mean arterial pressure increase at 60 (coefficient 24.3 [95% CI, 0.79-7.87]; p = 0.04) and 120 minutes (coefficient 26.1 [95% CI, 2.75-48.2]; p = 0.02). There were no biochemical or hematocrit changes within 4 hours of the fluid bolus. Urine output for the entire cohort was 2 mL/kg/hr at baseline and did not change with the fluid bolus.

CONCLUSIONS

Fluid boluses of 4% albumin were common and predominantly in children with cardiac disease and sepsis with a median dose of 10 mL/kg given over half an hour. Such treatment was associated with significant hemodynamic changes only in children less than 12 months old, and we failed to identify an association with urine output.

Variability in the Hemodynamic Response to Fluid Bolus in Pediatric Septic Shock

OBJECTIVES

Fluid boluses are commonly administered to improve the cardiac output and tissue oxygen delivery in pediatric septic shock. The objective of this study is to evaluate the effect of an early fluid bolus administered to children with septic shock on the cardiac index and mean arterial pressure, as well as on the hemodynamic response and its relationship with outcome.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

We prospectively collected hemodynamic data from children with septic shock presenting to the emergency department or the PICU who received a fluid bolus (10 mL/kg of Ringers Lactate over 30 min). A clinically significant response in cardiac index-responder and mean arterial pressure-responder was both defined as an increase of greater than or equal to 10% 10 minutes after fluid bolus.

MEASUREMENTS AND MAIN RESULTS

Forty-two children with septic shock, 1 month to 16 years old, median Pediatric Risk of Mortality-III of 13 (interquartile range, 9-19), of whom 66% were hypotensive and received fluid bolus within the first hour of shock recognition. Cardiac index- and mean arterial pressure-responsiveness rates were 31% and 38%, respectively. We failed to identify any association between cardiac index and mean arterial pressure changes (r = 0.203; p = 0.196). Cardiac function was similar in mean arterial pressure- and cardiac index-responders and nonresponders. Mean arterial pressure-responders increased systolic, diastolic, and perfusion pressures (mean arterial pressure - central venous pressure) after fluid bolus due to higher indexed systemic vascular resistance and arterial elastance index. Mean arterial pressure-nonresponders required greater vasoactive-inotrope support and had higher mortality.

CONCLUSIONS

The hemodynamic response to fluid bolus in pediatric septic shock was variable and unpredictable. We failed to find a relationship between mean arterial pressure and cardiac index changes. The adverse effects of fluid bolus extended beyond fluid overload and, in some cases, was associated with reduced mean arterial pressure, perfusion pressures and higher vasoactive support. Mean arterial pressure-nonresponders had increased mortality. The response to the initial fluid bolus may be helpful to understand each patient's individualized physiologic response and guide continued hemodynamic management.