Early initiation renal replacement therapy for fluid management to reduce central venous pressure is more conducive to renal function recovery in patients with acute kidney injury

Current Fluid Management Practice in Critically Ill Adults on Continuous Renal Replacement Therapy: A Binational, Observational Study

INTRODUCTION

In critically ill patients undergoing continuous renal replacement therapy (CRRT), a positive fluid balance (FB) is associated with adverse outcomes. However, current FB management practices in CRRT patients are poorly understood. We aimed to study FB and its components in British and Australian CRRT patients to inform future trials.

METHODS

We obtained detailed electronic health record data on all fluid-related variables during CRRT and hourly FB for the first 7 days of treatment.

RESULTS

We studied 1,616 patients from three tertiary intensive care units (ICUs) in two countries. After the start of CRRT, the mean cumulative FB became negative at 31 h and remained negative over 7 days to a mean nadir of -4.1 L (95% confidence interval (CI) of -4.6 to -3.5). The net ultrafiltration (NUF) rate was the dominant fluid variable (-67.7 mL/h; standard deviation (SD): 75.7); however, residual urine output (-34.7 mL/h; SD: 54.5), crystalloid administration (48.1 mL/h; SD: 44.6), and nutritional input (36.4 mL/h; SD: 29.7) significantly contributed to FB. Patients with a positive FB after 72 h of CRRT were more severely ill, required high-dose vasopressors, and had high lactate concentrations (5.0 mmol/L; interquartile range: 2.3-10.5). A positive FB was independently associated with increased hospital mortality (odds ratio: 1.70; 95% CI; p = 0.004).

CONCLUSION

In the study ICUs, most CRRT patients achieved a predominantly NUF-dependent negative FB. Patients with a positive FB at 72 h had greater illness severity and haemodynamic instability. Achieving equipoise for conducting trials that target a negative early FB in such patients may be difficult.

Integrative Pharmacology in the Treatment of Substance Use Disorders

The detrimental physical, mental, and socioeconomic effects of substance use disorders (SUDs) have been apparent to the medical community for decades. However, it has become increasingly urgent in recent years to develop novel pharmacotherapies to treat SUDs. Currently, practitioners typically rely on monotherapy. Monotherapy has been shown to be superior to no treatment at all for most substance classes. However, many randomized controlled trials (RCTs) have revealed that monotherapy leads to poorer outcomes when compared with combination treatment in all specialties of medicine. The results of RCTs suggest that monotherapy frequently fails since multiple dysregulated pathways, enzymes, neurotransmitters, and receptors are involved in the pathophysiology of SUDs. As such, research is urgently needed to determine how various neurobiological mechanisms can be targeted by novel combination treatments to create increasingly specific yet exceedingly comprehensive approaches to SUD treatment. This article aims to review the neurobiology that integrates many pathophysiologic mechanisms and discuss integrative pharmacology developments that may ultimately improve clinical outcomes for patients with SUDs. Many neurobiological mechanisms are known to be involved in SUDs including dopaminergic, nicotinic, N-methyl-D-aspartate (NMDA), and kynurenic acid (KYNA) mechanisms. Emerging evidence indicates that KYNA, a tryptophan metabolite, modulates all these major pathophysiologic mechanisms. Therefore, achieving KYNA homeostasis by harmonizing integrative pathophysiology and pharmacology could prove to be a better therapeutic approach for SUDs. We propose KYNA-NMDA-α7nAChRcentric pathophysiology, the "conductor of the orchestra," as a novel approach to treat many SUDs concurrently. KYNA-NMDA-α7nAChR pathophysiology may be the "command center" of neuropsychiatry. To date, extant RCTs have shown equivocal findings across comparison conditions, possibly because investigators targeted single pathophysiologic mechanisms, hit wrong targets in underlying pathophysiologic mechanisms, and tested inadequate monotherapy treatment. We provide examples of potential combination treatments that simultaneously target multiple pathophysiologic mechanisms in addition to KYNA. Kynurenine pathway metabolism demonstrates the greatest potential as a target for neuropsychiatric diseases. The investigational medications with the most evidence include memantine, galantamine, and N-acetylcysteine. Future RCTs are warranted with novel combination treatments for SUDs. Multicenter RCTs with integrative pharmacology offer a promising, potentially fruitful avenue to develop novel therapeutics for the treatment of SUDs.

Current management of fluid balance in critically ill patients with acute kidney injury: A scoping review

Objective

The overall objective of this scoping review is to assess the extent of the literature related to the fluid management of critically ill patients with acute kidney injury (AKI).

Introduction

AKI is common in critically ill patients where fluid therapy is a mainstay of treatment. An association between fluid balance (FB) and adverse patient-centred outcomes in critically ill patients with AKI regardless of severity has been demonstrated. The evidence for the prospective intervention of FB and its impact on outcomes is unknown.

Inclusion criteria

All studies investigating FB in patients with AKI admitted to an intensive care unit were included. Literature not related to FB in the critically ill patient with AKI population was excluded.

Methods

We searched MEDLINE, EMBASE, and CINAHL from January 1st, 2012, onwards. We included primary research studies, experimental and observational, recruiting adult participants admitted to an intensive care unit who had an AKI. We extracted data on study and patient characteristics, as well as FB, renal-based outcomes, and patient-centred outcomes. Two reviewers independently screened citations for eligible studies and performed data extraction.

Results

Of the 13,767 studies reviewed, 22 met the inclusion criteria. Two studies examined manipulation of fluid input, 18 studies assessed enhancing fluid removal, and two studies applied a restrictive fluid protocol. Sixteen studies examined patients receiving renal replacement therapy, five studies included non-renal replacement therapy patients, and one study included both. Current evidence is broad with varied approaches to managing fluid input and fluid removal. The studies did not demonstrate a consensus approach for any aspect of the fluid management of critically ill patients. There was a limited application of a restrictive fluid protocol with no conclusions possible.

Conclusions

The current body of evidence for the management of FB in critically ill patients with AKI is limited in nature. The current quality of evidence is unable to guide current clinical practice. The key outcome of this review is to highlight areas for future research.

Impact of Continuous Renal Replacement Therapy Initiation on Urine Output and Fluid Balance: A Multicenter Study

INTRODUCTION

The effect of continuous renal replacement therapy (CRRT) on renal function is poorly understood. However, the initiation of CRRT may induce oliguria. We aimed to investigate the impact of CRRT commencement on urine output (UO).

METHODS

This was a retrospective cohort study in two intensive care units. We included all patients who underwent CRRT and collected data on hourly UO and fluid balance before and after CRRT commencement. We performed an interrupted time series analysis using segmented regression to assess the relationship between CRRT commencement and UO.

RESULTS

We studied 1,057 patients. Median age was 60.7 years (interquartile range [IQR], 48.3-70.6), and the median APACHE III was 95 (IQR, 76-115). Median time to CRRT was 17 h (IQR, 5-49). With start of CRRT, the absolute difference in mean hourly UO and mean hourly fluid balance was -27.0 mL/h (95% CI: -32.1 to -21.8; p value < 0.01) and - 129.3 mL/h (95% CI: -169.2 to -133.3), respectively. When controlling for pre-CRRT temporal trends and patient characteristics, there was a rapid post-initiation decrease in UO (-0.12 mL/kg/h; 95% CI: -0.17 to -0.08; p value < 0.01) and fluid balance (-78.1 mL/h; 95% CI: -87.9 to -68.3; p value < 0.01), which was sustained over the first 24 h of CRRT. Change in UO and fluid balance were only weakly correlated (r -0.29; 95% CI: -0.35 to -0.23; p value < 0.01).

CONCLUSION

Commencement of CRRT was associated with a significant decrease in UO that could not be explained by extracorporeal fluid removal.

Comprehensive Management of Blood Pressure in Patients with Septic AKI

Acute kidney injury (AKI) is one of the serious complications of sepsis in clinical practice, and is an important cause of prolonged hospitalization, death, increased medical costs, and a huge medical burden to society. The pathogenesis of AKI associated with sepsis is relatively complex and includes hemodynamic abnormalities due to inflammatory response, oxidative stress, and shock, which subsequently cause a decrease in renal perfusion pressure and eventually lead to ischemia and hypoxia in renal tissue. Active clinical correction of hypotension can effectively improve renal microcirculatory disorders and promote the recovery of renal function. Furthermore, it has been found that in patients with a previous history of hypertension, small changes in blood pressure may be even more deleterious for kidney function. Therefore, the management of blood pressure in patients with sepsis-related AKI will directly affect the short-term and long-term renal function prognosis. This review summarizes the pathophysiological mechanisms of microcirculatory disorders affecting renal function, fluid management, vasopressor, the clinical blood pressure target, and kidney replacement therapy to provide a reference for the clinical management of sepsis-related AKI, thereby promoting the recovery of renal function for the purpose of improving patient prognosis.

High cut-off membranes in patients requiring renal replacement therapy: a systematic review and meta-analysis

BACKGROUND

Whether high cut-off (HCO) membranes are more effective than high-flux (HF) membranes in patients requiring renal replacement therapy (RRT) remains controversial. The aim of this systematic review was to investigate the efficacy of HCO membranes regarding the clearance of inflammation-related mediators, β2-microglobulin and urea; albumin loss; and all-cause mortality in patients requiring RRT.

METHODS

We searched all relevant studies on PubMed, Embase, Web of Science, the Cochrane Library, and China National Knowledge Infrastructure, with no language or publication year restrictions. Two reviewers independently selected studies and extracted data using a prespecified extraction instrument. Only randomized controlled trials (RCTs) were included. Summary estimates of standardized mean differences (SMDs) or weighted mean differences (WMDs) and risk ratios (RRs) were obtained by fixed-effects or random-effects models. Sensitivity analyses and subgroup analyses were performed to determine the source of heterogeneity.

RESULTS

Nineteen RCTs involving 710 participants were included in this systematic review. Compared with HF membranes, HCO membranes were more effective in reducing the plasma level of interleukin-6 (IL-6) (SMD -0.25, 95% confidence interval (CI) -0.48 to -0.01, P   =  0.04, I2  = 63.8%); however, no difference was observed in the clearance of tumor necrosis factor-α (TNF-α) (SMD 0.03, 95% CI -0.27 to 0.33, P  = 0.84, I2  = 4.3%), IL-10 (SMD 0.22, 95% CI -0.12 to 0.55, P  = 0.21, I2  = 0.0%), or urea (WMD -0.27, 95% CI -2.77 to 2.23, P  = 0.83, I2  = 19.6%). In addition, a more significant reduction ratio of β 2 -microglobulin (WMD 14.8, 95% CI 3.78 to 25.82, P  = 0.01, I2  = 88.3%) and a more obvious loss of albumin (WMD -0.25, 95% CI -0.35 to -0.16, P  < 0.01, I2  = 40.8%) could be observed with the treatment of HCO membranes. For all-cause mortality, there was no difference between the two groups (risk ratio [RR] 1.10, 95% CI 0.87 to 1.40, P  = 0.43, I2  = 0.0%).

CONCLUSIONS

Compared with HF membranes, HCO membranes might have additional benefits on the clearance of IL-6 and β 2-microglobulin but not on TNF-α, IL-10, and urea. Albumin loss is more serious with the treatment of HCO membranes. There was no difference in all-cause mortality between HCO and HF membranes. Further larger high-quality RCTs are needed to strengthen the effects of HCO membranes.

Chronic, Combined Cardiac and Renal Dysfunction Exacerbates Renal Venous Pressure-Induced Suppression of Renal Function in Rats

Background and Objective

Increased renal venous pressure (RVP) is common in combined heart and kidney failure. We previously showed that acute RVP elevation depresses renal blood flow (RBF), glomerular filtration rate (GFR), and induces renal vasoconstriction in the absence of changes in blood pressure in healthy rats. We used our established rodent model of chronic combined heart and kidney failure (H/KF) to test whether RVP elevation would impair cardiovascular stability, renal perfusion and exacerbate renal dysfunction.

Methods

Male rats were subjected to 5/6 nephrectomy (SN_x or Sham) and 6% high salt diet followed 7 weeks later by ligation of the left anterior descending coronary artery (CL or Sham). Experimental groups: CL + SN_x (n = 12), Sham CL + SN_x (n = 9), CL+ Sham SN_x (n = 6), and Sham Control (n = 6). Six weeks later, anesthetized rats were subjected to an acute experiment whereupon mean arterial pressure (MAP), heart rate (HR), RVP, RBF, and GFR were measured at baseline and during elevation of RVP to 20–25 mmHg for 120 min.

Results

Baseline MAP, HR, RBF, and renal vascular conductance (RVC) were comparable among groups. Baseline GFR was significantly depressed in CL + SN_x and Sham CL + SN_x groups compared to Sham Control and CL + Sham SN_x groups. Upon RVP increase, MAP and HR fell in all groups. Increased RVP exacerbated the reduction in RBF in CL + SN_x (−6.4 ± 0.9 ml/min) compared to Sham Control (−3.7 ± 0.9 ml/min, p < 0.05) with intermediate responses in Sham CL + SN_x (−6.8 ± 1.3 ml/min) and CL + Sham SN_x (−5.1 ± 0.4 ml/min) groups. RVP increase virtually eliminated GFR in CL + SN_x (−99 ± 1%), Sham CL + SN_x (−95 ± 5%), and CL + Sham SN_x (−100%) groups compared to Sham Control (−84 ± 15% from baseline; p < 0.05). Renal vascular conductance dropped significantly upon RVP increase in rats with HF (CL + SN_x: −0.035 ± 0.011; CL + Sham SN_x: −0.050 ± 0.005 ml/min·mmHg⁻¹, p < 0.05) but not Sham CL + SN_x (−0.001 ± 0.019 ml/min·mmHg⁻¹) or Control (−0.033 ± mL/min·mmHg⁻¹).

Conclusion

Chronic combined heart and kidney failure primarily impairs renal hemodynamic stability in response to elevated RVP compared to healthy rats.