Nigel Fealy

Myoglobin clearance by super high-flux hemofiltration in a case of severe rhabdomyolysis: a case report

ObjectiveTo test the ability of a novel super high-flux (SHF) membrane with a larger pore size to clear myoglobin from serum.SettingThe intensive care unit of a university teaching hospital.SubjectA patient with serotonin syndrome complicated by severe rhabodomyolysis and oliguric acute renal failureMethodInitially continuous veno-venous hemofiltration was performed at 2 l/hour ultrafiltration (UF) with a standard polysulphone 1.4 m2 membrane (cutoff point, 20 kDa), followed by continuous veno-venous hemofiltration with a SHF membrane (cutoff point, 100 kDa) at 2 l/hour UF, then at 3 l/hour UF and then at 4 l/hour UF, in an attempt to clear myoglobin.ResultsThe myoglobin concentration in the ultrafiltrate at 2 l/hour exchange was at least five times greater with the SHF membrane than with the conventional membrane (>100,000 μg/l versus 23,003 μg/l). The sieving coefficients with the SHF membrane at 3 l/hour UF and 4 l/hour UF were 72.2% and 68.8%, respectively. The amount of myoglobin removed with the conventional membrane was 1.1 g/day compared with 4.4–5.1 g/day for the SHF membrane. The SHF membrane achieved a clearance of up to 56.4 l/day, and achieved a reduction in serum myoglobin concentration from >100,000 μg/l to 16,542 μg/l in 48 hours.ConclusionsSHF hemofiltration achieved a much greater clearance of myoglobin than conventional hemofiltration, and it may provide a potential modality for the treatment of myoglobinuric acute renal failure.

Pre-Dilution vs. Post-Dilution during Continuous Veno-Venous Hemofiltration: Impact on Filter Life and Azotemic Control

Background/Aims: To determine the impact of replacement fluid infusion site on filter life and azotemic control during continuous veno-venous hemofiltration (CVVH). Methods:Pre-dilution CVVH was conducted from February 2001 to December 2001 and then practice was changed to post-dilution (from January 2002 to July 2002). Filter life was prospectively observed and the following data obtained for each filter: starting date and time, ending date and time, heparin use, heparin dose and protamine use. Daily creatinine, urea, INR, APTT and platelet count were also collected. Results: Forty-eight patients were studied (33 in pre-dilution and 15 in post-dilution) for a total of 309 filters (202 in pre-dilution and 107 in post-dilution). The median filter life was significantly shorter in the post-dilution period (18.0 vs. 13.0 h, p = 0.021). Multivariate linear regression analysis showed that pre-dilution was a significant independent predictor of increased filter life (p = 0.029), together with platelet count (p = 0.0035) and heparin dose (p = 0.046). There was no significant improvement in daily creatinine and/or urea reduction in the post-dilution period (% Δ creatinine: 7.9 vs. 10.2%/day, p = 0.99, urea: 5.4 vs. 9.7%/ day, p = 0.78). Conclusions: Post-dilution was associated with reduced filter life without any beneficial effect on daily changes in urea and creatinine levels. Pre-dilution appears a preferable technical approach to CVVH.

A pilot randomized controlled comparison of extended daily dialysis with filtration and continuous veno-venous hemofiltration: fluid removal and hemodynamics.

Objectives Extended intermittent dialytic techniques are increasingly being reported in the treatment of ARF in the ICU but few randomized controlled trials exist. We compared one such technique to a technique of continuous renal replacement therapy with regard to fluid removal and hemodynamics. Methods Sixteen critically ill patients with ARF were enrolled in a randomized controlled trial at the ICU of a tertiary hospital. We randomized eight patients to three consecutive days of treatment with either Extended Daily Dialysis with filtration (EDDf) or Continuous Veno-Venous Hemofiltration (CVVH) and compared fluid removal and hemodynamics during treatment. Results A total of 16.6 liters of fluid were removed during EDDf (830 mL/day over 20 treatment days) compared with 15.4 liters (700 ml/day over 22 treatment days) during CVVH. Median fluid removal per day was 1837 mL in the EDDf group compared with 1410 mL per day in the CVVH group, p=0.674. Median hourly fluid removal rate was 252 mL for EDDf and 128 mL for CVVH (p<0.01). Mean arterial pressure in the EDDf group was lower at two hours after starting treatment (76 mmHg vs. 94 mmHg) in the CVVH group; p= 0.031. There was no significant difference between groups for heart rate, CVP and noradrenaline dose at all time intervals measured. Conclusions Adequate prescribed fluid removal was achieved with both techniques. However, as expected, fluid was removed at a faster rate during EDDf. This was initially associated with a lower blood pressure than during CVVH where blood pressure increased.

Early mobilization on continuous renal replacement therapy is safe and may improve filter life

IntroductionDespite studies demonstrating benefit, patients with femoral vascular catheters placed for continuous renal replacement therapy are frequently restricted from mobilization. No researchers have reported filter pressures during mobilization, and it is unknown whether mobilization is safe or affects filter lifespan. Our objective in this study was to test the safety and feasibility of mobilization in this population.MethodsA total of 33 patients undergoing continuous renal replacement therapy via femoral, subclavian or internal jugular vascular access catheters at two general medical-surgical intensive care units in Australia were enrolled. Patients underwent one of three levels of mobilization intervention as appropriate: (1) passive bed exercises, (2) sitting on the bed edge or (3) standing and/or marching. Catheter dislodgement, haematoma and bleeding during and following interventions were evaluated. Filter pressure parameters and lifespan (hours), nursing workload and concern were also measured.ResultsNo episodes of filter occlusion or failure occurred during any of the interventions. No adverse events were detected. The intervention filters lasted longer than the nonintervention filters (regression coefficient = 13.8 (robust 95% confidence interval (CI) = 5.0 to 22.6), P = 0.003). In sensitivity analyses, we found that filter life was longer in patients who had more position changes (regression coefficient = 2.0 (robust 95% CI = 0.6 to 3.5), P = 0.007). The nursing workloads between the intervention shift and the following shift were similar.ConclusionsMobilization during renal replacement therapy via a vascular catheter in patients who are critically ill is safe and may increase filter life. These findings have significant implications for the current mobility restrictions imposed on patients with femoral vascular catheters for renal replacement therapy.Trial registrationAustralian and New Zealand Clinical Trials Registry ACTRN12611000733976 (registered 13 July 2011)

Nursing for Renal Replacement Therapies in the Intensive Care Unit: Historical, Educational, and Protocol Review

Nurses have made a significant contribution to the development and application of dialysis in the 1950s and continuous renal replacement therapies (CRRT) in the Intensive Care Unit (ICU) setting from the 1980s. Any treatment requires patient and machine-circuit preparation, connection of the extracorporeal circuit (EC) to the patient vascular access catheter and regular tasks to maintain a treatment in progress. During treatment, nurses prepare fluids, adjust fluid settings to provide fluid balance, prepare electrolyte additives, monitor acid base and electrolyte levels, monitor patient and machine ‘vital signs’, and then when necessary diagnose circuit clotting and perform a disconnection of the EC from the patient. All of these aspects of CRRT nursing are essential to a suitable nursing policy or protocol. This paper provides a clinical review for this every day sequence when using CRRT in the ICU setting.

Clinical nursing for the application of continuous renal replacement therapy in the intensive care unit.

Treatment of critically ill patients with continuous renal replacement therapy (CRRT) requires a set of new skills and knowledge base for the intensive care unit (ICU) nurse. After a decision to treat is made, nurses effectively manage the technique by following a series of steps in sequence. These sequential steps include patient and machine circuit preparation, connection of the extracorporeal circuit (EC) to the patient’s vascular access, and nursing management of a treatment in progress. During treatment, nurses prepare fluids, adjust fluid settings to provide fluid balance, prepare electrolyte additives, monitor acid base and electrolyte levels, monitor patient and machine “vital signs,” and, when necessary, diagnose circuit clotting and perform a disconnection of the EC from the patient. All of these aspects of CRRT nursing are essential for a successful CRRT nursing policy or protocol. This chapter provides a clinical review for this every day sequence when using CRRT in the ICU setting.

Screening and study enrolment in the Randomized Evaluation of Normal vs. Augmented Level (RENAL) Replacement Therapy Trial

Background and Objectives: Aspects of trial design, screening and study efficiency can affect recruitment and the findings of the trial itself. A clear understanding of the screening and study inclusion process will assist clinicians in interpreting trial results. Design: Prospective observational data collection on all patients screened for possible inclusion in a randomized controlled trial of normal vs. augmented renal replacement therapy in critically ill patients (the RENAL Trial). Setting: 35 hospitals in Australia and New Zealand. Participants: All patients screened for the RENAL Trial. Results: We screened 4,551 patients. Of these patients, 767 were ineligible because of lack of inclusion criteria and 2,085 because of exclusion criteria. Of the remaining 1,699, 1,508 (88.7%) were enrolled. The three most common exclusion criteria which prevented recruitment of potentially eligible patients were that the patient had end-stage kidney failure and was already on chronic dialysis (484; 23.2%), the patient’s body weight was either <60 or >120 kg (456; 21.8%), and the fact that the patient had already received renal replacement therapy during the index admission. Important modifiable impediments to recruitment were inability to obtain consent in 191 cases, unavailability of research staff in 124 cases, physician objection in 89 cases, and inability to deliver the trial protocol in 78 cases. Conclusion: The RENAL Trial’s enrolment efficiency was high and compared favourably with previous large intensive care units trials and with that of trials in patients with acute renal failure. The high rate of enrolment suggests that the results can be applied with confidence to most patients with de novo acute renal failure. The loss of close to 1.5% of patients due to consent issues highlights a common problem in critical care trials. The low rate of physician objection suggests clinical equipoise.

Beta2-microglobulin removal and plasma albumin levels with high cut-off hemodialysis.

Purpose. β2-microglobulin (β2MG) is pivotal to the pathogenesis of dialysis-related amyloidosis. We compared the effects of high cut-off hemodialysis (HCO-HD) with those of standard high-flux hemodialysis (HF-HD) regarding the concentration and clearance of β2MG and albumin. Design. We enrolled ten patients with acute renal failure in a double-blind, cross-over, randomized controlled trial. Procedures Each patient received four hours of HCO-HD (estimated in vivo cutoff 50–60 kDa) and four hours of HF-HD (estimated in vivo cutoff 15–20 kDa) in random order. Statistical methods and outcome measures: As data lacked normal distribution, we used non-parametric statistical analysis. Plasma and dialysate concentrations of β2MG and albumin were measured at baseline and after four hours of each study treatment. Main findings. We found significantly greater diffusive β2MG clearances for HCO-HD compared to HF-HD (at the start: 71.8 ml/min vs. 5.1 ml/min; P=0.008 and at the end: 68.8 ml/min vs. 5.7 ml/min; P=0.008). We found a reduction in plasma β2MG concentrations of -31.6% during HCO-HD compared to an increase by 25.7% during HF-HD; P=0.008. At baseline (HCO-HD: 26.0 g/L vs. HF-HD: 26.5 g/L), and at the end of both treatments, plasma albumin concentrations were comparable (HCO-HD: 25.5 g/L vs. HF-HD: 26.5 g/L; P=0.25). During HCO-HD, albumin clearance was 1.9 ml/min at the start and decreased significantly to 0.8 ml/min at the end; P=0.008. HF-HD had an albumin clearance of 0.01 ml/min. Conclusions. HCO-HD was more effective in decreasing plasma β2MG concentrations than standard HF-HD and did not reduce plasma albumin levels. Further studies of HCO-HD in the treatment of dialysis-related β2MG accumulation appear warranted. (ClinicalTrials.gov number, NCT00333593 [ClinicalTrials.gov]) (Int J Artif Organs 2007; 30: 385–92)

Amino Acid Balance with Extended Daily Diafiltration in Acute Kidney Injury

Background: The impact of hybrid dialysis therapies on amino acid (AA) balance in critically ill patients with acute kidney injury is unknown. Methods: We examined prospectively the AA balance with extended daily diafiltration (EDDF). Results: We studied 7 patients. AA clearances with EDDF ranged from 21.6 ml/min (tryptophan) to 66.9 ml/min (taurine). AA loss was 4.2 (IQR 1.4–12.3) g/day and 4.5% of daily protein intake for patients on enteral nutrition (EN). Percentage AA loss per hour on EDDF was highest for glutamine (32.1%) and lowest for glutamic acid (0.8%). Blood AA levels correlated with corresponding EDDF losses. Median total nitrogen appearance was 25.0 (IQR 20.6–29.3) g/day for patients on EN. This resulted in a negative nitrogen balance of –10.7 (IQR –16.6 to –1.4) g/day, of which 6.5% was attributable to AA loss. Conclusions: AA loss with EDDF was limited, but with much individual variability, and contributed to a strongly negative daily nitrogen balance.

Premature circuit clotting due to likely mechanical failure during continuous renal replacement therapy.

Objective: Failure of extracorporeal circuit (EC) function during continuous renal replacement therapy (CRRT) appears most likely due to progressive circuit clotting or, in some cases, most likely due to mechanical problems that affect flow. We aimed to study the incidence of such likely mechanical circuit failure (MCF). Design and Setting: Retrospective observational study in an adult ICU of a tertiary hospital. Patients and Measurements: We studied 30 patients treated with CRRT via femoral vein vascular access. We obtained information on age, gender, diagnosis, mode of CRRT, circuit life, and blood chemistry. We defined MCF as ‘likely’ if there was a reduction of between 60 and 80% in circuit life compared to the previous or following circuit life and ‘very likely’ if such a reduction was between 81 and 100%. Results: We studied 166 circuits in 30 different patients. Of these 26 were electively disconnected leaving 140 circuits with unplanned cessation of function. Among these circuits, likely MCF affected 10 circuits (7.1%) and very likely MCF affected 9 circuits (6.4%) for a total of 19 (13.6%) circuits. Conclusion: Mechanical circuit failure appears to affect approximately 1 in 8 circuits. Prospective studies are needed to understand why MCF occurs.