Mediators of the Impact of Hourly Net Ultrafiltration Rate on Mortality in Critically Ill Patients Receiving Continuous Renal Replacement Therapy

The interaction of net ultrafiltration rate with urine output and fluid balance after continuous renal replacement therapy initiation: A multi-Centre study

PURPOSE

During continuous renal replacement therapy (CRRT), a high net ultrafiltration rate (NUF) may worsen the decrease in urine output (UO) associated with starting CRRT. However, fluid balance (FB) may modulate this association. We aimed to examine the relationship between NUF, UO and FB at the start of CRRT.

METHODS

A retrospective cohort study of 1030 CRRT-treated patients admitted to two tertiary ICUs.

RESULTS

Median age was 60 years (IQR, 48-70), median APACHE III was 94 (IQR, 76-114) and median NUF rate was 0.7 mL/kg/h. In the 24 h after CRRT started, the mean hourly UO decreased from 25.5 mL to 11.9 mL (P < 0.001). Moreover, after adjusting for multiple confounders on multivariable analysis, a higher NUF was not significantly associated with a lower UO (-1.5 mL/kg for every 1 mL/kg/h increase in NUF; 95% CI -3.1 to 0.04; p = 0.064). In addition, pre-CRRT FB did not modulate the above relationship between higher NUF and lower UO.

CONCLUSION

A higher NUF rate was not significantly associated with a greater immediate and sustained reduction in UO after CRRT commencement. FB before CRRT was also not associated with a greater reduction in UO. These findings do not provide evidence for an effect of NUF on renal function.

Proceedings of the 2022 UAB CRRT Academy: Non-Invasive Hemodynamic Monitoring to Guide Fluid Removal with CRRT and Proliferation of Extracorporeal Blood Purification Devices

In 2022, we celebrated the 15th anniversary of the University of Alabama at Birmingham (UAB) Continuous Renal Replacement Therapy (CRRT) Academy, a 2-day conference attended yearly by an international audience of over 100 nephrology, critical care, and multidisciplinary trainees and practitioners. This year, we introduce the proceedings of the UAB CRRT Academy, a yearly review of select emerging topics in the field of critical care nephrology that feature prominently in the conference. First, we review the rapidly evolving field of non-invasive hemodynamic monitoring and its potential to guide fluid removal by renal replacement therapy (RRT). We begin by summarizing the accumulating data associating fluid overload with harm in critical illness and the potential for harm from end-organ hypoperfusion caused by excessive fluid removal with RRT, underscoring the importance of accurate, dynamic assessment of volume status. We describe four applications of point-of-care ultrasound used to identify patients in need of urgent fluid removal or likely to tolerate fluid removal: lung ultrasound, inferior vena cava ultrasound, venous excess ultrasonography, and Doppler of the left ventricular outflow track to estimate stroke volume. We briefly introduce other minimally invasive hemodynamic monitoring technologies before concluding that additional prospective data are urgently needed to adapt these technologies to the specific task of fluid removal by RRT and to learn how best to integrate them into practical fluid-management strategies. Second, we focus on the growth of novel extracorporeal blood purification devices, starting with brief reviews of the inflammatory underpinnings of multiorgan dysfunction and the specific applications of pathogen, endotoxin, and/or cytokine removal and immunomodulation. Finally, we review a series of specific adsorptive technologies, several of which have seen substantial clinical use during the COVID-19 pandemic, describing their mechanisms of target removal, the limited existing data supporting their efficacy, ongoing and future studies, and the need for additional prospective trials.

Earlier continuous renal replacement therapy is associated with reduced mortality in rhabdomyolysis patients

Background

Continuous renal replacement therapy (CRRT) is commonly employed for rhabdomyolysis (RM) patients. However, the optimal initiation timing of CRRT and prognostic factors were not well evaluated for patients with RM. We aimed to investigate the efficacy of CRRT timing on mortality and the risk factors for death in RM patients who received CRRT.

Methods

RM patients who received CRRT between 1 May 2010 and 31 May 2021 in our center were retrospectively included. Univariate and multivariate logistic analyses were performed to identify the risk factors for primary outcome (90-day mortality).

Results

A total of 134 patients were included in our study. The 90-day mortality rate was 38.06%. The median time from CRRT initiation to peak CK occurrence was 4.8 h (IQR −16, 14), 67 patients received CRRT before 4.8 h after peak CK occurrence (early CRRT), and 67 patients received CRRT beyond 4.8 h after peak CK occurrence (late CRRT). Multivariate logistic regression analysis showed that the time from CRRT initiation to the peak CK (per 1 h, OR 1.026, 95% CI 1.004–1.049, p = 0.023), late CRRT (OR 3.082, 95% CI 1.072–8.859, p = 0.037), elevated serum cardiac troponin I (cTnI) (per 1 ng/mL, OR 1.218, 95% CI 1.011–1.468, p = 0.038), older age (per 1 year, OR 1.042, 95% CI 1.003–1.081, p = 0.032), and need of mechanical ventilation support (OR 4.632, 95% CI 1.292–16.61, p = 0.019) were independent risk factors for 90-day mortality.

Conclusions

Earlier CRRT initiation before 4.8 h after peak CK occurrence was associated with lower 90-day patient mortality.

How to Determine Fluid Management Goals during Continuous Kidney Replacement Therapy in Patients with AKI: Focus on POCUS

The utilization of kidney replacement therapies (KRT) for fluid management of patients who are critically ill has significantly increased over the last years. Clinical studies have suggested that both fluid accumulation and high fluid removal rates are associated with adverse outcomes in the critically ill population receiving KRT. Importantly, the ideal indications and/or fluid management strategies that could favorably affect these patients are unknown; however, differentiating clinical scenarios in which effective fluid removal may provide benefit to the patient by avoiding congestive organ injury, compared with other settings in which this intervention may result in harm, is direly needed in the critical care nephrology field. In this review, we describe observational data related to fluid management with KRT, and examine the role of point-of-care ultrasonography as a potential tool that could provide physiologic insights to better individualize decisions related to fluid management through KRT.

Hemodynamic instability during connection to continuous kidney replacement therapy in critically ill pediatric patients

BACKGROUND

Emerging data suggest evidence of organ hypoperfusion during continuous kidney replacement therapy (CKRT). To facilitate kidney and global recovery, we must understand the hemodynamic risks associated with CKRT. We aimed to investigate frequency of hemodynamic instability and association with patient outcomes in pediatric CKRT.

METHODS

In a single-center study of CKRT patients between September 2016 and October 2018, we collected hemodynamic data using archived high-resolution physiologic data before and after connection. Primary outcome was hypotension defined as ≥ 20% decrease in baseline mean arterial pressure (MAP) for ≥ 2 consecutive minutes in the 60 min following connection. Secondary outcomes were tachycardia (≥ 20% increase in heart rate (HR)) and hemodynamic interventions.

RESULTS

Seventy-one patients median age 54 months (IQR 7-144), weight 16.7 kg (IQR 8-41), on hemodiafiltration had 304 filter connections, 4 (IQR 1-7) filters per patient; the median duration of CKRT was 9 days (IQR 3-20). The most common CKRT indication was AKI with fluid overload (48/71, 69%). There were 78 (27%) hypotension and 42 (14%) tachycardia events; cumulative duration of hypotension was 14 min IQR (3-31.75). Teams provided intervention in 17/304 (6%) of connections. Pediatric Logistic Organ Dysfunction 2 was the only independent predictor of hypotension (aOR 2.12 (CI 1.02-4.41)).

CONCLUSIONS

One in four and one in six pediatric CKRT filter connections were complicated by hypotension and tachycardia, respectively. Higher illness severity at CKRT initiation was independently associated with hypotension. Impact of CKRT-associated hemodynamic instability on global patient outcomes requires further targeted study. A higher resolution version of the Graphical abstract is available as Supplementary information.

Assessment of prescribed vs. achieved fluid balance during continuous renal replacement therapy and mortality outcome

Background

Fluid management during continuous renal replacement therapy (CRRT) requires accuracy in the prescription of desired patient fluid balance (FBGoal) and precision in the attainable patient fluid balance (FBAchieved). Herein, we examined the association of the gap between prescribed vs. achieved patient fluid balance during CRRT (%FBGap) with hospital mortality in critically ill patients.

Methods

Cohort study of critically ill adults with acute kidney injury (AKI) requiring CRRT and a prescription of negative fluid balance (mean patient fluid balance goal of negative ≥0.5 liters per day). Fluid management parameters included: 1) NUF (net ultrafiltration rate); 2) FBGoal; 3) FBAchieved; and 4) FBGap (% gap of fluid balance achieved vs. goal), all adjusted by patient’s weight (kg) and duration of CRRT (hours).

Results

Data from 653 patients (median of 102.2 patient-hours of CRRT) were analyzed. Mean (SD) age was 56.7 (14.6) years and 61.9% were male. Hospital mortality rate was 64%. Despite FBGoal was similar in patients who died vs. survived, survivors achieved greater negative fluid balance during CRRT than non-survivors: median FBAchieved -0.25 [-0.52 to -0.05] vs. 0.06 [-0.26 to 0.62] ml/kg/h, p<0.001. Median NUF was lower in patients who died vs. survived: 1.06 [0.63–1.47] vs. 1.22 [0.82–1.69] ml/kg/h, p<0.001, and median %FBGap was higher in patients who died (112.8%, 61.5 to 165.7) vs. survived (64.2%, 30.5 to 91.8), p<0.001. In multivariable models, higher %FBGap was independently associated with increased risk of hospital mortality: aOR (95% CI) 1.01 (1.01–1.02), p<0.001. NUF was not associated with hospital mortality when adjusted by %FBGap and other clinical parameters: aOR 0.96 (0.72–1.28), p = 0.771.

Conclusions

Higher %FBGap was independently associated with an increased risk of hospital mortality in critically ill adults with AKI on CRRT in whom clinicians prescribed negative fluid balance via CRRT. %FBGap represents a novel quality indicator of CRRT delivery that could assist with operationalizing fluid management interventions during CRRT.

Mediators of neutrophil lymphocyte ratio in the relationship between ondansetron pre-treatment and the mortality of ICU patients on mechanical ventilation: causal mediation analysis from the MIMIC-IV database

AIMS

The mortality of critically ill patients undergoing mechanical ventilation (MV) is high and few strategies are available. We explored the relationship between ondansetron pre-treatment, the neutrophil:lymphocyte ratio (NLR), and platelet:lymphocyte ratio (PLR), and mortality of ventilated patients in the intensive care unit.

METHODS

We developed a retrospective cohort study that involved patients undergoing MV in the Multiparameter Intelligent Monitoring in Intensive Care IV (MIMIC-IV) database. Causal mediation analysis was conducted to assess the relationship of ondansetron use and mortality and explore the potential causal pathway mediated by the NLR or PLR. The primary outcome was 28-day mortality.

RESULTS

A total of 17,927 eligible patients was obtained (5665 had taken ondansetron before MV initiation and 12,262 patients had not). The OR for 28-day mortality for ondansetron use uncorrelated with the mediator (NLR, PLR) was 0.72 (95%CI=0.64-0.81, P <0.001). Ondansetron was also associated with a reduction in 28-day mortality after controlling for the mediator of NLR (OR = 0.98, 95%CI = 0.97-0.99, P < 0.01). For the indirect effect, the NLR could explain 13.47% (95%CI = 8.59-20.54%, P < 0.01) of the impact of ondansetron use on 28-day mortality. The proportion mediated increased to 21.50% (95%CI = 12.36-47.44%, P < 0.01) for 90-day mortality. Adjusted mediation analysis revealed no suggestion of a causal mediation pathway for this effect by the PLR (P = 0.12).

CONCLUSIONS

NLR may play substantial roles in the relationship between ondansetron pre-treatment before initiation of mechanical ventilation and the reduction of death risk in ventilated patients.

The Association of an Early Net Ultrafiltration Rate and 28-Day Mortality in Patients Receiving Continuous Kidney Replacement Therapy

Background: An early net ultrafiltration (NUF) rate may be associated with prognosis in patients receiving continuous kidney replacement therapy (CKRT). In this study, we tested whether high or low early NUF rates in patients treated with CKRT were associated with increased mortality. Methods: We conducted a retrospective, observational study among all patients in the Medical Information Mart for Intensive Care IV database who received CKRT for more than 24 h within 14 days after intensive care unit admission. We defined the early (initial 48 h) NUF rate as the amount of fluid removal per hour adjusted by the patients' weight and took it as a classified variable (low rate: <1.6, moderate rate: 1.6-3.1 and high rate: > 3.1 ml/kg/h). The association between 28-day mortality and the NUF rate was analyzed by logistic regression and mediation analyses. Results: A total of 911 patients were included in our study. The median NUF rate was 2.71 (interquartile range 1.90-3.86) ml/kg/h and the 28-day mortality was 40.1%. Compared with the moderate NUF rate, the low NUF rate (adjusted odds ratio 1.56, 95% CI 1.04-2.35, p = 0.032) and high NUF rate (adjusted odds ratio 1.43, 95% CI 1.02-2.01, p = 0.040) were associated with higher 28-day mortality. The putative effect of high or low NUF rates on 28 day mortality was not direct [adjusted average direct effects (ADE) for a low NUF rate = 0.92, p = 0.064; adjusted ADE for a high NUF rate = 1.03, p = 0.096], but mediated by effects of the NUF rate on fluid balance during the same period [adjusted average causal mediation effects (ACME) 0.96, p = 0.010 for a low NUF rate; adjusted ACME 0.99, p = 0.042 for a high NUF rate]. Moreover, we found an increase trend in the NUF rate corresponding to the lowest mortality when fluid input increased. Conclusion: Compared with NUF rates between 1.6-3.1 ml/kg/h in the first 48 h of CKRT, NUF rates > 3.1 and <1.6 ml/kg/h were associated with higher mortality.

Survey of U.S. Critical Care Practitioners on Net Ultrafiltration Prescription and Practice among Critically Ill Patients Receiving Kidney Replacement Therapy

INTRODUCTION

The current prescription and practice of net ultrafiltration among critically ill patients receiving kidney replacement therapy in the U.S. are unclear.

AIM OF THE STUDY

To assess the attitudes of U.S. critical care practitioners on net ultrafiltration (UFNET) prescription and practice among critically ill patients with acute kidney injury treated with kidney replacement therapy.

METHODS

A secondary analysis was conducted of a multinational survey of intensivists, nephrologists, advanced practice providers, and ICU and dialysis nurses practising in the U.S.

RESULTS

Of 1,569 respondents, 465 (29.6%) practitioners were from the U.S. Mainly were nurses and advanced practice providers (58%) and intensivists (38.2%). The median duration of practice was 8.7 (IQR, 4.2-19.4) years. Practitioners reported using continuous kidney replacement therapy (as the first modality in 60% (IQR 20%-90%) for UFNET. It was found that there was a significant variation in assessment of prescribed-to-delivered dose of UFNET, use of continuous kidney replacement therapy for UFNET, methods used to achieve UFNET, and assessment of net fluid balance during continuous kidney replacement therapy. There was also variation in interventions performed for managing hemodynamic instability, perceived barriers to UFNET, belief that early and protocol-based fluid removal is beneficial, and willingness to enroll patients in a clinical trial.

CONCLUSIONS

There was considerable practice variation in UFNET among critical care practitioners in the U.S., reflecting the need to generate evidence-based practice guidelines for UFNET.

Association between Net Ultrafiltration Rate and Renal Recovery among Critically Ill Adults with Acute Kidney Injury Receiving Continuous Renal Replacement Therapy: An Observational Cohort Study

INTRODUCTION

Higher net ultrafiltration (UFNET) rates are associated with mortality among critically ill patients with acute kidney injury (AKI) and treated with continuous renal replacement therapy (CRRT).

OBJECTIVE

The aim of the study was to discover whether UFNET rates are associated with renal recovery and independence from renal replacement therapy (RRT).

METHODS

Retrospective cohort study using data from the Randomized Evaluation of Normal versus Augmented Level of Renal Replacement Therapy trial that enrolled 1,433 critically ill patients with AKI and treated with CRRT between December 2005 and November 2008 across 35 intensive care units in Australia and New Zealand. We examined the association between UFNET rate and time to independence from RRT by day 90 using competing risk regression after accounting for mortality. The UFNET rate was defined as the volume of fluid removed per hour adjusted for patient body weight.

RESULTS AND CONCLUSIONS

Median age was 67.3 (interquartile range [IQR], 57-76.3) years, 64.4% were male, median Acute Physiology and Chronic Health Evaluation-III score was 100 (IQR, 84-118), and 634 (44.2%) died by day 90. Kidney recovery occurred in 755 patients (52.7%). Using tertiles of UFNET rates, 3 groups were defined: high, >1.75; middle, 1.01-1.75; and low, <1.01 mL/kg/h. Proportion of patients alive and independent of RRT among the groups were 47.8 versus 57.2 versus 53.0%; p = 0.01. Using competing risk regression, higher UFNET rate tertile compared with middle (cause-specific hazard ratio [csHR], 0.79, 95% CI, 0.66-0.95; subdistribution hazard ratio [sHR], 0.80, 95% CI, 0.67-0.97) and lower (csHR, 0.69, 95% CI, 0.56-0.85; sHR, 0.78, 95% CI 0.64-0.95) tertiles were associated with a longer time to independence from RRT. Every 1.0 mL/kg/h increase in rate was associated with a lower probability of kidney recovery (csHR, 0.81, 95% CI, 0.74-0.89; and sHR, 0.87, 95% CI, 0.80-0.95). Using the joint model, longitudinal increases in UFNET rates were also associated with a lower renal recovery (β = -0.29, p < 0.001). UFNET rates >1.75 mL/kg/h compared with rates 1.01-1.75 and <1.01 mL/kg/h were associated with a longer duration of dependence on RRT. Randomized clinical trials are required to confirm this UFNET rate-outcome relationship.

Ultrafiltration in critically ill patients treated with kidney replacement therapy

Management of fluid overload is one of the most challenging problems in the care of critically ill patients with oliguric acute kidney injury. Various clinical practice guidelines support fluid removal using ultrafiltration during kidney replacement therapy. However, ultrafiltration is associated with considerable risks. Emerging evidence from observational studies suggests that both slow and fast rates of net fluid removal (that is, net ultrafiltration (UFNET)) during continuous kidney replacement therapy are associated with increased mortality compared with moderate UFNET rates. In addition, fast UFNET rates are associated with an increased risk of cardiac arrhythmias. Experimental studies in patients with kidney failure who were treated with intermittent haemodialysis suggest that fast UFNET rates are also associated with ischaemic injury to the heart, brain, kidney and gut. The UFNET rate should be prescribed based on patient body weight in millilitres per kilogramme per hour with close monitoring of patient haemodynamics and fluid balance. Dialysate cooling and sodium modelling may prevent haemodynamic instability and facilitate large volumes of fluid removal in patients with kidney failure who are treated with intermittent haemodialysis, but the effects of this strategy on organ injury are less well studied in critically ill patients treated with continuous kidney replacement therapy. Randomized trials are required to examine whether moderate UFNET rates are associated with a reduced risk of haemodynamic instability, organ injury and improved outcomes in critically ill patients.

Kidney Replacement Therapy for Fluid Management

Emerging evidence from observational studies suggests that both slower and faster net ultrafiltration rates during kidney replacement therapy are associated with increased mortality in critically ill patients with acute kidney injury and fluid overload. Faster rates are associated with ischemic organ injury. The net ultrafiltration rate should be prescribed based on patient body weight in milliliters per kilogram per hour, with close monitoring of patient hemodynamics and fluid balance. Randomized trials are required to examine whether moderate net ultrafiltration rates compared with slower and faster rates are associated with reduced risk of hemodynamic instability, organ injury, and improved outcomes.