Fluid management in acute kidney injury: from evaluating fluid responsiveness towards assessment of fluid tolerance

Sound waves and solutions: Point-of-care ultrasonography for acute kidney injury in cirrhosis

This article delves into the intricate challenges of acute kidney injury (AKI) in cirrhosis, a condition fraught with high morbidity and mortality. The complexities arise from distinguishing between various causes of AKI, particularly hemodynamic AKI, in cirrhotic patients, who experience hemodynamic changes due to portal hypertension. The term "hepatocardiorenal syndrome" is introduced to encapsulate the intricate interplay among the liver, heart, and kidneys. The narrative emphasizes the often-overlooked aspect of cardiac function in AKI assessments in cirrhosis, unveiling the prevalence of cirrhotic cardiomyopathy marked by impaired diastolic function. The conventional empiric approach involving volume expansion and vasopressors for hepatorenal syndrome is critically analyzed, highlighting potential risks and variable patient responses. We advocate for a nuanced algorithm for AKI evaluation in cirrhosis, prominently featuring point-of-care ultrasonography (POCUS). POCUS applications encompass assessing fluid tolerance, detecting venous congestion, and evaluating cardiac function.

Hemodynamic Changes in Intrarenal Blood Flow are Associated With Poor Prognosis in Patients With Acute Decompensated Heart Failure

AIM

To evaluate a potential role of different patterns of intrarenal blood flow using Doppler ultrasound as a part of determining the severity of venous congestion, predicting impairment of renal function and an unfavorable prognosis in patients with acute decompensated chronic heart failure (ADCHF).

MATERIAL AND METHODS

This prospective observational single-site study included 75 patients admitted in the intensive care unit for ADCHF. Upon admission all patients underwent bedside renal venous Doppler ultrasound to determine the blood flow pattern (continuous, biphasic, monophasic). In one hour after the initiation of intravenous diuretic therapy, sodium concentration was measured in a urine sample. The primary endpoint was the development of acute kidney injury (AKI). The secondary endpoints were the development of diuretic resistance (a need to increase the furosemide daily dose by more than 2 times compared with the baseline), decreased natriuretic response (defined as urine sodium concentration less than 50-70 mmol/l), and in-hospital death.

RESULTS

According to the data of Doppler ultrasound, normal renal blood flow was observed in 40 (53%) patients, biphasic in 21 (28%) patients, and monophasic in 14 (19%) patients. The monophasic pattern of intrarenal blood flow was associated with the highest incidence of AKI: among 14 patients in this group, AKI developed in 100% of cases (OR 3.8, 95% CI: 2.5-5.8, p<0.01), while among patients with normal and moderate impairment of renal blood flow, there was no significant increase in the risk of developing AKI. The odds of in-hospital death were increased 25.77 times in patients with monophasic renal blood flow (95% CI: 5.35-123.99, p<0.001). Patients with a monophasic intrarenal blood flow pattern were also more likely to develop diuretic resistance compared to patients with other blood flow patterns (p<0.001) and had a decreased sodium concentration to less than 50 mmol/l (p<0.001) in a spot urine test obtained one hour after the initiation of furosemide administration.

CONCLUSION

Patients with monophasic intrarenal blood flow are at a higher risk of developing AKI, diuretic resistance with decreased natriuretic response, and in-hospital death.

Diagnostic accuracy of venous system ultrasound for subtypes of acute kidney injury

BACKGROUND

Management of acute kidney injury (AKI) in the ED can be difficult due to uncertainty regarding the aetiology. This study investigated the diagnostic value of venous system ultrasound for determining the aetiological subtypes of AKI in the ED.

METHODS

This multidisciplinary prospective cohort study was conducted in a single academic ED over the course of a year. Adult patients with AKI were evaluated using the venous excess ultrasound (VExUS) score, which is a four-step ultrasound protocol. The protocol begins with the inferior vena cava (IVC) measurement and examines organ flow patterns, including portal, hepatic and renal veins in the presence of dilated IVC. The AKI subtypes (hypovolaemia, cardiorenal, systemic vasodilatation and renal) were adjudicated by nephrologists and emergency physicians, considering data that became available during the hospitalisation. We determined the diagnostic test characteristics of VExUS for identifying each of the four AKI aetiological subtypes.

RESULTS

150 patients with AKI were included in the study. Hypovolaemia was the most frequent finally adjudicated cause of AKI (66%), followed by cardiorenal (18%), systemic vasodilatation (8.7%) and renal (7.3%). In diagnosing the cardiorenal subtype, the area under the curve (AUC) for VExUS grade >0 was 0.819, with 77.8% sensitivity and 80.5% specificity, and the AUC for IVC maximum diameter >20.4 mm was 0.865, with 74.1% sensitivity and 86.2% specificity. For the hypovolaemia subtype, the AUC for VExUS grade ≤0 was 0.711, with 83.8% sensitivity and 56.9% specificity, and the AUC for IVC maximum diameter ≤16.8 mm was 0.736, with 73.7% sensitivity and 68.6% specificity. None of the parameters achieved adequate test characteristics for renal and systemic vasodilatation subtypes.

CONCLUSION

The VExUS score has good diagnostic accuracy for cardiorenal AKI and fair accuracy for hypovolaemic AKI but cannot identify renal and systemic vasodilatation subtypes. It should not therefore be used in isolation to determine the cause of AKI in the ED.

TRIAL REGISTRATION NUMBER

NCT04948710.

Coexistence of a fluid responsive state and venous congestion signals in critically ill patients: a multicenter observational proof-of-concept study

BACKGROUND

Current recommendations support guiding fluid resuscitation through the assessment of fluid responsiveness. Recently, the concept of fluid tolerance and the prevention of venous congestion (VC) have emerged as relevant aspects to be considered to avoid potentially deleterious side effects of fluid resuscitation. However, there is paucity of data on the relationship of fluid responsiveness and VC. This study aims to compare the prevalence of venous congestion in fluid responsive and fluid unresponsive critically ill patients after intensive care (ICU) admission.

METHODS

Multicenter, prospective cross-sectional observational study conducted in three medical-surgical ICUs in Chile. Consecutive mechanically ventilated patients that required vasopressors and admitted < 24 h to ICU were included between November 2022 and June 2023. Patients were assessed simultaneously for fluid responsiveness and VC at a single timepoint. Fluid responsiveness status, VC signals such as central venous pressure, estimation of left ventricular filling pressures, lung, and abdominal ultrasound congestion indexes and relevant clinical data were collected.

RESULTS

Ninety patients were included. Median age was 63 [45-71] years old, and median SOFA score was 9 [7-11]. Thirty-eight percent of the patients were fluid responsive (FR+), while 62% were fluid unresponsive (FR-). The most prevalent diagnosis was sepsis (41%) followed by respiratory failure (22%). The prevalence of at least one VC signal was not significantly different between FR+ and FR- groups (53% vs. 57%, p = 0.69), as well as the proportion of patients with 2 or 3 VC signals (15% vs. 21%, p = 0.4). We found no association between fluid balance, CRT status, or diagnostic group and the presence of VC signals.

CONCLUSIONS

Venous congestion signals were prevalent in both fluid responsive and unresponsive critically ill patients. The presence of venous congestion was not associated with fluid balance or diagnostic group. Further studies should assess the clinical relevance of these results and their potential impact on resuscitation and monitoring practices.

Meaning and Management of Perioperative Oliguria

Perioperative oliguria is an alarm signal. The initial assessment includes closer patient monitoring, evaluation of volemic status, risk-benefit of fluid challenge or furosemide stress test, and investigation of possible perioperative complications.

Critical Care Echocardiography: Assessing Left and Right Ventricular Function in the Intensive Care Unit

In this review we explore Left Ventricular and Right Ventricular parameters that intensivists can use to evaluate, manage, and monitor the critically ill. Understanding these parameters, their clinical relevance, and potential pitfalls, is crucial for thorough and accurate patient assessment and management. Critical Care Echocardiography encompasses all the advanced cardiac and non-cardiac skillset needed to integrate the findings of Left Ventricular and Right Ventricular size and function. We advocate for a physiologic approach to the critically ill patient, tailoring therapy to reverse the etiology while simultaneously supporting circulation based on a sound understanding of left and right ventricular pressures, volumes, and flow.

The Role of Pre- and Post-Transplant Hydration Status in Kidney Graft Recovery and One-Year Function

Background and Objectives: Early improvements to graft function are crucial for good outcomes in kidney transplantation (kTx). Various factors can influence early graft function. This study aimed to evaluate the pre- and post-transplant hydration statuses of kTx recipients using bioimpedance analysis (BIA) and lung ultrasonography (LUS) and to investigate the hydration status' relationship with the function of the transplanted kidney during the first year after transplantation. Materials and Methods: This observational prospective cohort study included deceased kidney recipients transplanted in the Hospital of the Lithuanian University of Health Sciences between September 2016 and January 2023. BIA and LUS were performed before transplantation, on days 3 and 7, and at discharge. Data on recipient and donor clinical characteristics were collected. Graft function was evaluated according to the serum creatinine reduction ratio and the need for dialysis. Hydration status was evaluated by calculating B-lines (BL) on LUS and the ratio of extracellular/total body water on BIA. Results: Ninety-eight kTx recipients were included in the study. Patients with immediate graft function (IGF) were compared to those with slow or delayed graft function (SGF + DGF). Recipients in the SGF + DGF group had a higher sum of BL on LUS before transplantation. After transplantation in early postoperative follow-up, both groups showed hyperhydration as determined by BIA and LUS. After one year, recipients with no BL before transplantation had better graft function than those with BL. Logistic regression analysis showed that having more than one BL in LUS was associated with a 2.5 times higher risk of SGF or DGF after transplantation. Conclusions: This study found that lung congestion detected by LUS before kTx was associated with slower graft recovery and worse kidney function after 1 year. Meanwhile, the hyperhydration status detected by BIA analysis did not correlate with the function of the transplanted kidney.

Correlation of Internal Jugular Vein Collapsibility With Central Venous Pressure in Patients With Liver Cirrhosis

We aimed to compare internal jugular vein and inferior vena cava ultrasonography as predictors of central venous pressure in cirrhotic patients. We performed ultrasound assessments of the internal jugular vein (IJV) and the inferior vena cava and then invasively measured central venous pressure (CVP). We then compared their correlation with CVP and performed area under the receiver operating characteristic curves to determine which had best sensitivity and specificity. IJV cross-sectional area collapsibility index at 30° correlated better with CVP ( r = -0.56, P < 0.001), and an IJV AP-CI at 30° ≤ 24.8% was better at predicting a CVP ≥8 mm Hg, with 100% sensitivity and 97.1% specificity. Thus, IJV point-of-care ultrasound might be superior than inferior vena cava point-of-care ultrasound as a predictor of CVP in cirrhotic patients.

Cardiopulmonary interactions-which monitoring tools to use?

Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient's condition, enabling accurate assessment and patient care.

Haemodynamic support for paediatric septic shock: a global perspective

Septic shock is a leading cause of hospitalisation, morbidity, and mortality for children worldwide. In 2020, the paediatric Surviving Sepsis Campaign (SSC) issued evidence-based recommendations for clinicians caring for children with septic shock and sepsis-associated organ dysfunction based on the evidence available at the time. There are now more trials from multiple settings, including low-income and middle-income countries (LMICs), addressing optimal fluid choice and amount, selection and timing of vasoactive infusions, and optimal monitoring and therapeutic endpoints. In response to developments in adult critical care to trial personalised haemodynamic management algorithms, it is timely to critically reassess the current state of applying SSC guidelines in LMIC settings. In this Viewpoint, we briefly outline the challenges to improve sepsis care in LMICs and then discuss three key concepts that are relevant to management of children with septic shock around the world, especially in LMICs. These concepts include uncertainties surrounding the early recognition of paediatric septic shock, choices for initial haemodynamic support, and titration of ongoing resuscitation to therapeutic endpoints. Specifically, given the evolving understanding of clinical phenotypes, we focus on the controversies surrounding the concepts of early fluid resuscitation and vasoactive agent use, including insights gained from experience in LMICs and high-income countries. We outline the key components of sepsis management that are both globally relevant and translatable to low-resource settings, with a view to open the conversation to the large variety of treatment pathways, especially in LMICs. We emphasise the role of simple and easily available monitoring tools to apply the SSC guidelines and to tailor individualised support to the patient's cardiovascular physiology.

Volume Management with Kidney Replacement Therapy in the Critically Ill Patient

While the administration of intravenous fluids remains an important treatment, the negative consequences of subsequent fluid overload have raised questions about when and how clinicians should pursue avenues of fluid removal. Decisions regarding fluid removal during critical illness are complex even for patients with preserved kidney function. This article seeks to apply general concepts of fluid management to the care of patients who also require KRT. Because optimal fluid management for any specific patient is likely to change over the course of critical illness, conceptual models using phases of care have been developed. In this review, we will examine the implications of one such model on the use of ultrafiltration during KRT for volume removal in distributive shock. This will also provide a useful lens to re-examine published data of KRT during critical illness. We will highlight recent prospective trials of KRT as well as recent retrospective studies examining ultrafiltration rate and mortality, review the results, and discuss applications and shortcomings of these studies. We also emphasize that current data and techniques suggest that optimal guidelines will not consist of recommendations for or against absolute fluid removal rates but will instead require the development of dynamic protocols involving frequent cycles of reassessment and adjustment of net fluid removal goals. If optimal fluid management is dynamic, then frequent assessment of fluid responsiveness, fluid toxicity, and tolerance of fluid removal will be needed. Innovations in our ability to assess these parameters may improve our management of ultrafiltration in the future.