Two-liner…
A look at the evolving concept of venous congestion and the haemodynamic assessment in critically ill children and adults. The literature exploring its nuances continues to grow in adults but remains poorly understood in paediatric populations.[1]
Fred is a 3-year-old boy who presents to the emergency department. He was previously healthy and presented with a 3-day history of cough, fevers, low appetite, and decreased energy. His parents reported he had not been himself, listless and refusing anything to eat or drink, and his urine output has decreased in the past 24 hours.
On examination, he was mottled with cool extremities. He appeared tired, passive, and listless. As the PICU Registrar, you are called to review him. He has received 20ml/kg in 5 to 10ml/kg aliquots in the ED, as his blood pressure ‘keeps dropping’, and the ED team is concerned about possible sepsis. He has been started on timely broad-spectrum antibiotics according to hospital protocol.
You are worried as his oxygen requirements are increasing, and his blood pressure is lower than you are happy with, so decide to admit him to the PICU. Before transfer, he received another 20 ml/kg of IVF.
In the PICU, he is intubated for worsening respiratory distress. He has had some additional episodes of hypotension post-intubation, which is treated with further volume resuscitation. Despite 60ml/kg, his systolic blood pressure is back in the low 50s. Before considering a further fluid bolus, you do a point-of-care ultrasound (POCUS).
The cardiac assessment shows normal left ventricular function; however, the right ventricle (RV) is mildly dilated with mild dysfunction. The inferior vena cava (IVC) is dilated with minimal respiro-phasic variability, and the hepatic vein shows abnormality with S-wave reversal (a finding of severe congestion) as seen in Figure 1. This is also demonstrated in the portal vein with high pulsatility, which indicates congestion, as seen in Figure 2. To add to this, there is a biphasic intra-renal Doppler signal suggestive of congestion Figure 3.,
Watching these signs, you pause… he’s had 60ml/kg as fluid boluses, but what do you do with these signs?
Volume resuscitation has historically been the first-line therapy for patients in septic shock. This patient, who you presumed septic and hypovolaemic, has signs of severe venous congestion.
Is more fluid the answer? Or should early initiation of vasopressors or inodilators be the first line in this 3-year-old boy? Let’s dive deep and find out…
What is Venous Congestion?
Venous congestion refers to elevated venous pressures that result in impaired venous drainage from organs, particularly the kidneys, liver, gut, and brain.
Importantly, venous congestion is distinct from ‘volume overload.’
Venous congestion represents increased pressure within the venous system caused by the complex interplay between cardiac function and filling. Encapsulated organs, such as the kidneys, are particularly vulnerable, as their limited capacity for swelling creates a vicious cycle of congestion-mediated renal oedema (“renosarca”)[2].
The venous pressure for a given organ is just as important as the arterial pressure because, together, these variables determine the perfusion pressure (= arterial pressure – venous pressure) for that organ. This perfusion pressure is critical in maintaining optimal blood flow to each organ and its effective function.
In adults, venous congestion has been associated with acute kidney injury (AKI), increased need for renal replacement therapy, and higher mortality for multiple populations of critically ill patients[3-5]. Understanding venous congestion in pediatric patients may identify new causal pathways of organ injury for critically ill patients, with potential treatment implications.
How Do We Measure Venous Congestion?
Venous congestion is often identified in adults by Doppler ultrasound techniques, which evaluate flow in key venous structures: the inferior vena cava (IVC), hepatic vein (HV), portal vein (PV), and intrarenal veins.
The Venous Excess Ultrasound (VExUS) score combines these measurements into a standardized grading system, validated primarily in the adult cardiac surgical population[5].
One common question is: Can central venous pressure (CVP) predict organ-level congestion?
The short answer… No.
Although at a population level, elevated CVP is associated with acute kidney injury (AKI) and other adverse outcomes, the sensitivity and specificity to predict these outcomes for an individual patient is poor. This is because central pressures may not always be pathologically transmitted to the organs we care about (e.g. the kidneys). Additionally, intrathoracic, intra-abdominal, and even local pressures can impact the congestion at the organ level. Taken together, the adult critical care community has shifted towards assessing for venous congestion at the organ level with Doppler ultrasound.
Some measurement techniques in paediatric patients differ from adults due to anatomical and physiological differences. This is particularly true regarding assessing the IVC for congestion given the variation in size of the vessel with age and a convention to assess the IVC in the short axis (rather than the long axis) [6].
Other authors have used measures of IVC congestion, such as the IVC-aorta ratio and IVC collapsibility index. These significant differences between pediatric and adult patients raise important questions about the optimal approach to assessing for venous congestion in pediatric patients.
Venous Congestion in Adult Critical Care
In adults, venous congestion is a well-recognized contributor to organ dysfunction in many conditions, including septic shock and heart failure. Approximately 20% of adults with septic shock in the ICU exhibit venous congestion, with significant implications for prognosis and treatment.[3]
Interventions in adults typically focus on identifying the underlying cause of congestion—whether volume excess, cardiac dysfunction, or pulmonary hypertension—and then tailoring treatment accordingly. Depending on the pathophysiology, strategies include fluid restriction, diuretics, renal replacement therapy, inodilators, vasopressors, and pulmonary vasodilators. Several large observational and controlled trials assessing these strategies are underway.
Hemodynamic Phenotyping in Paediatrics
While the principles of haemodynamic phenotyping—categorising patients based on measurable cardiovascular characteristics—are broadly applied across ages, paediatric patients pose unique challenges and are currently being investigated [7].
Children’s physiological differences, such as a lower prevalence of diastolic dysfunction and distinct developmental cardiac and vascular characteristics, may alter the presentation and significance of venous congestion. For example, pediatric patients are less prone to the types of diastolic dysfunction commonly observed in adults, potentially changing the prevalence of venous congestion.
Venous Congestion in Pediatric Patients: What We Know
The current literature on venous congestion in paediatrics is limited[8-10]. A study of children with cerebral malaria in Malawi found no venous congestion despite a high prevalence of AKI [9]. This finding contrasts sharply with adult populations, where venous congestion is a frequent finding in septic shock and a significant contributor to AKI [3]. These differences underscore the need for further research to clarify the role of venous congestion in pediatric critical care.
Key Differences Between Adults and Paediatrics
- Thresholds for Congestion: Due to physiological differences, the thresholds for clinically significant venous congestion likely differ between children and adults. Even within adult populations, thresholds vary across conditions like septic shock and cardiac dysfunction, suggesting the need for pediatric-specific criteria.
- Measurement Techniques: While Doppler ultrasound remains the cornerstone for assessing venous congestion, pediatric adaptations, such as short-axis IVC imaging or IVC-to-aorta size indexing, may improve accuracy and reliability in children. These remain key areas of study[11,12].
- Prevalence: How common venous congestion occurs in critically ill children is unclear. There is evidence, however, that volume overload is associated with increased morbidity and mortality for PICU patients[13-18]. Venous congestion may likely be an important yet underrecognized cause of organ failure in select patient populations, such as those predisposed to cardiac dysfunction (e.g. congenital heart disease, septic cardiomyopathy), aggressive volume resuscitation (e.g. septic shock, oncology patients), or where RV function may be compromised [19, 20] (e.g. pulmonary hypertension, pARDS).
- Treatment Strategies: In adults, treating venous congestion focuses on identifying the underlying cause and implementing targeted therapies. In paediatrics, different causes of congestion may necessitate different treatments. In the adult population, for example, most cases of volume-overloaded congestion respond well to diuretics, as these are often related to left heart failure. For pediatric patients, therapy is dual-focused, focusing on optimising cardiac function, reducing pulmonary pressures, and correcting fluid overload in this complex patient group.
A conundrum within children is the time course of venous congestion:
- Is it as acute as the adult population or a slower secondary phenomenon?
- Should we be doing serial bedside monitoring?
Having found severe venous congestion, timely vasopressors and inodilators are started instead of further fluid boluses to restore organ perfusion.
The mottling improved, and markers of venous congestion repeated less than 12 hours later began normalising. His urine output also improved.
This suggests that RV dysfunction was an important contributor to organ-level congestion, which improved through optimizing cardiac function.
Bottom line…
Venous congestion is a critical but understudied phenomenon in pediatric critical care.
While adult literature provides a framework for understanding its pathophysiology, measurement, and management, pediatric-specific adaptations are essential.
Differences in thresholds, assessment techniques, and underlying causes underscore the need for further research to define the role of venous congestion in children and tailor interventions accordingly.
By addressing these gaps, we can improve hemodynamic assessments and meaningful outcomes for critically ill pediatric patients.
References
1. Menéndez-Suso, J.J., D. Rodríguez-Álvarez, and M. Sánchez-Martín, Feasibility and Utility of the Venous Excess Ultrasound Score to Detect and Grade Central Venous Pressure Elevation in Critically Ill Children. J Ultrasound Med, 2023. 42(1): p. 211-220.
2. Perez Nieto, O.R., et al., Aiming for zero fluid accumulation: First, do no harm. Anaesthesiol Intensive Ther, 2021. 53(2): p. 162-178.
3. Prager, R., et al., Venous congestion in septic shock quantified with point-of-care ultrasound: a pilot prospective multicentre cohort study. Can J Anaesth, 2024. 71(5): p. 640-649.
4. Bhardwaj, V., et al., Combination of Inferior Vena Cava Diameter, Hepatic Venous Flow, and Portal Vein Pulsatility Index: Venous Excess Ultrasound Score (VEXUS Score) in Predicting Acute Kidney Injury in Patients with Cardiorenal Syndrome: A Prospective Cohort Study. Indian J Crit Care Med, 2020. 24(9): p. 783-789.
5. Beaubien-Souligny, W., et al., Quantifying systemic congestion with Point-Of-Care ultrasound: development of the venous excess ultrasound grading system. Ultrasound J, 2020. 12(1): p. 16.
6. Kaptein, E.M. and M.J. Kaptein, Inferior vena cava ultrasound and other techniques for assessment of intravascular and extravascular volume: an update. Clinical Kidney Journal, 2023. 16(11): p. 1861-1877.
7. Darnell, R., et al., Protocol for a Randomized Controlled Trial to Evaluate a Permissive Blood Pressure Target Versus Usual Care in Critically Ill Children with Hypotension (PRESSURE). Pediatric Critical Care Medicine, 2024. 25(7): p. 629-637.
8. Natraj, R., et al., Venous Congestion Assessed by Venous Excess Ultrasound (VExUS) and Acute Kidney Injury in Children with Right Ventricular Dysfunction. Indian J Crit Care Med, 2024. 28(5): p. 447-452.
9. Lintner Rivera, M., et al., Point-of-care Ultrasound to Assess Hemodynamic Contributors to Acute Kidney Injury in Pediatric Patients With Cerebral Malaria: A Pilot Study. Pediatr Infect Dis J, 2023. 42(10): p. 844-850.
10. Voccaro, The VExUS Score in assessing the volemic status of paediatric nephropathic patients 2024: ECR24.
11. Kusumastuti, N.P., A. Latief, and A.H. Pudjiadi, Inferior Vena Cava/Abdominal Aorta Ratio as a Guide for Fluid Resuscitation. J Emerg Trauma Shock, 2021. 14(4): p. 211-215.
12. Walker, S.B., et al., Performance of Tools and Measures to Predict Fluid Responsiveness in Pediatric Shock and Critical Illness: A Systematic Review and Meta-Analysis. Pediatr Crit Care Med, 2024. 25(1): p. 24-36.
13. Selewski, D.T. and S.L. Goldstein, The role of fluid overload in the prediction of outcome in acute kidney injury. Pediatr Nephrol, 2018. 33(1): p. 13-24.
14. Raina, R., et al., Fluid Overload in Critically Ill Children. Front Pediatr, 2018. 6: p. 306.
15. Gist, K.M., et al., Assessment of the Independent and Synergistic Effects of Fluid Overload and Acute Kidney Injury on Outcomes of Critically Ill Children. Pediatr Crit Care Med, 2020. 21(2): p. 170-177.
16. Li, Y., et al., Early fluid overload is associated with acute kidney injury and PICU mortality in critically ill children. Eur J Pediatr, 2016. 175(1): p. 39-48.
17. Arikan, A.A., et al., Fluid overload is associated with impaired oxygenation and morbidity in critically ill children. Pediatr Crit Care Med, 2012. 13(3): p. 253-8.
18. Selewski, D.T., et al., Impact of the Magnitude and Timing of Fluid Overload on Outcomes in Critically Ill Children: A Report From the Multicenter International Assessment of Worldwide Acute Kidney Injury, Renal Angina, and Epidemiology (AWARE) Study. Crit Care Med, 2023. 51(5): p. 606-618.
19. Himebauch, A.S., et al., Early Right Ventricular Systolic Dysfunction and Pulmonary Hypertension Are Associated With Worse Outcomes in Pediatric Acute Respiratory Distress Syndrome. Crit Care Med, 2018. 46(11): p. e1055-e1062.
20. Himebauch, A.S., et al., New or Persistent Right Ventricular Systolic Dysfunction Is Associated With Worse Outcomes in Pediatric Acute Respiratory Distress Syndrome. Pediatr Crit Care Med, 2020. 21(2): p. e121-e128.
