A pilot randomised controlled comparison of continuous veno–venous haemofiltration and extended daily dialysis with filtration: effect on small solutes and acid–base balance

Background and aims Continuous veno–venous haemofiltration (CVVH) is an established treatment for acute renal failure (ARF). Recently, extended intermittent dialytic techniques have been proposed for the treatment of ARF. The aim of this study was to compare these two approaches. Setting Intensive care unit of tertiary hospital. Subjects Sixteen critically ill patients with ARF. Design Randomised controlled trial. Intervention We randomised sixteen patients to three consecutive days of treatment with either CVVH (8) or extended daily dialysis with filtration (EDDf) (8) and compared small-solute, electrolyte and acid–base control. Results There was no significant difference between the two therapies for urea or creatinine levels over 3 days. Of 80 electrolyte measurements taken before treatment, 19 were abnormal. All values were corrected as a result of treatment, except for one patient in the CVVH group who developed hypophosphataemia (0.54 mmol/l) at 72 h. After 3 days of treatment, there was a mild but persistent metabolic acidosis in the EDDf group compared to the CVVH group (median bicarbonate: 20 mmol/l vs. 29 mmol/l: p = 0.039; median base deficit: –4 mEq/l vs. –2.1 mEq/l, p = 0.033). Conclusions CVVH and EDDf as prescribed achieved similar control of urea, creatinine and electrolytes. Acidosis was better controlled with CVVH. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Prevention of contrast media nephrotoxicity--the story so far

Contrast media nephrotoxicity (CMN) in patients with pre-existing renal impairment remains a clinically significant problem. The first step to reduce the chance of CMN is to identify patients at risk through the use of screening questionnaires and renal function measurement. Patients at risk requiring injection of contrast medium (CM) because of important clinical indications should receive a small dose of either non-ionic iso-osmolar dimeric or non-ionic low osmolar monomeric CM and hydration. Intravenous infusion (1 ml/kg body weight/h) of 0.9% saline starting 4 h before CM injection and continuing for at least 12 h afterwards is effective in reducing the incidence of CMN. Prophylactic haemodialysis does not lower the risk of this complication. The value of pharmacological manipulation with renal vasodilators (calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam (selective dopamine-1 receptor agonist), prostaglandin E(1), non-selective adenosine receptors antagonist (theophylline), non-selective endothelin receptor antagonist or the antioxidant acetylcysteine has not been fully proven. However, haemofiltration for several hours before and after contrast medium injection offers good protection against CMN in patients with advanced renal disease.     

Potassium additive algorithm for use in continuous renal replacement therapy

The performance of continuous renal replacement therapy (CRRT) brings about alterations in the serum potassium levels in patient. Potassium is an electrolyte essential for the regulation of nerve conduction and muscle contraction, particularly important in the case of cardiac muscle. This article describes the physiological mechanisms that affect potassium distribution throughout the body and also describes the effects of hypokalaemia or hyperkalaemia on the heart. This article justifies the need for serum potassium control during CRRT, which recognizes and reconciles the differing areas of responsibility of the medical and nursing staff. This article critically reviews the steps taken to develop and implement into clinical practice and evaluate a potassium additive algorithm. It also discusses the implications of this initiative.     

Outcome of critically ill patients treated with intermittent high-volume haemofiltration: a prospective cohort analysis

Objective: To evaluate intervention and outcome in critically ill patients treated with high-volume haemofiltration (HV-HF). Design: Prospective cohort analysis. Setting: 18-bed closed format general intensive care unit (ICU) of a teaching hospital. Patients: 30-month cohort of ICU patients treated with HV-HF. Interventions: Intermittent high-volume venovenous haemofiltration. Endpoints: Observed and predicted mortality in prospectively stratified prognostic groups. Measurements and results: Clinical and filtration data, Acute Physiology and Chronic Health Evaluation (APACHE) II, Simplified Acute Physiology Score (SAPS) II and the Madrid Acute Renal Failure (ARF) score and predicted mortality. A total of 306 patients were haemofiltrated (140 medical, 166 surgical), 52 % were oliguric. Mean APACHE II score was 31 (SD 8) and mean SAPS II score 60 (SD 16). Mean ultrafiltrate rate was 63 ml/min (SD 20). A median total of 160 litres (90 % range 49 to 453) were filtrated per patient, material costs were 565 ECU (90 % range 199 to 1514). ICU mortality was 33 %, hospital mortality 40 % [95 % confidence interval (CI) 34 to 45], predicted mortality by the ARF score 67 % (CI 66 to 69). Non-cardiac surgery mortality was 47 % (CI 39 to 54), 73 % (CI 70 to 76) predicted by APACHE II and 67 % (CI 64 to 70) by SAPS II. Observed mortality was significantly lower than predicted in all prognostic groups. The standardised mortality ratio (SMR) was no higher than the SMR in the overall ICU population. Conclusions: Mortality in HV-HF patients was lower than that predicted by illness severity scores, as was the case in all patients in our ICU. Treatment with HV-HF appears to be safe and feasible. The efficacy of HV-HF should be tested in randomised, controlled trials of suitable power. Received: 4 December 1998 Final revision received: 20 April 1999 Accepted: 17 May 1999     

{beta}2-Microglobulin Kinetics During Haemofiltration

To study the kinetics of ß₂-microglobulin during haemofiltration,seven patients with end-stage renal failure were treated withthe AN 69 (acrylonitrile), Duo-Flux (cellulose acetate) andF 60 (polysulphone) haemofilter. Low ß₂-microglobulinsieving coefficients and a highly negative filter mass balanceerror were observed during the initial phase of treatment withAN 69 but not with Duo-Flux or F 60, indicating a high degreeof ß₂-microglobulin adsorption by AN 69. Total removalof ß₂-microglobulin was calculated by addition ofthe total amount adsorbed by the membrane and the total amountrecovered in the collected ultrafiltrate. With AN 69 and F 60,total removal of ß₂-microglobulin amounted to 393±135(SD) and 316±35mg per treatment, while total removalwith Duo-Flux was 242±79 mg per treatment. Thus, highlypermeable membranes such as AN 69 or F 60 used in a haemofiltrationmode may nearly balance the presumed generation of ß₂-microglobulinin uraemic patients. During treatment, an increase of the calculatedß₂-microglobulin distribution volume occurred withall three membranes, probably representing extra-to-intracellularwater shifts. The water shifts occurring during haemofiltrationreduce the value of precision of ß₂-microglobulinkinetics and limit the value of the plasma level decrease asan index of ß₂-microglobulin removal.     

Continuous venovenous haemofiltration in the acute treatment of inborn errors of metabolism

The accumulation of toxic metabolites in children with inborn errors of metabolism may cause acute metabolic crises and result in long-term neurological dysfunction or death. Peritoneal dialysis often provides insufficient clearance to protect against these complications, while intermittent haemodialysis cannot prevent reaccumulation of metabolites between dialysis sessions. We describe the use of continuous venovenous haemofiltration (CVVH) or haemodiafiltration (CVVHD) in three infants with maple syrup urine disease (MSUD) and one child with carbamyl phosphate synthetase (CPS) deficiency. All children with MSUD had a satisfactory reduction in branchedchain amino acids within 24 h of onset of haemofiltration, and are now neurologically normal. The child with CPS deficiency had an ammonia level of <100 mol/l within 24 h of onset of therapy, but died 3 days later from unrelated cardiovascular complications. Complications of the therapy included the clotting of one haemofilter and the replacement of two vascular access catheters per patient on average per therapy. Two patients required blood transfusion. We report the successful use of CVVH and CVVHD in the acute management of metabolic crises associated with inborn errors of metabolism, and believe that these may be the optimal techniques for the acute clearance of toxic metabolites.     

Erfahrungen mit großlumigen Verweilkathetern in der V. jugularis interna als Zugang für akute Hämodialysen

Zusammenfassung Seit 2 Jahrzehnten wird die perkutane Punktionstechnik nach Seldinger zur Einlage von großlumigen Kathetern zur Haemodialysebehandlung angewandt. Bisher wurden die Femoral- und Subclaviagefäße benutzt. Wir berichten über eigene Erfahrungen mit der Katheterisierung der V. jugularis interna mittels großlumiger Katheter (Shaldon-Katheter), die wir bei 194 Patienten mit insgesamt 237 Punktionen gewinnen konnten. Erforderlich wurde die perkutane Punktion der V. jugularis zur Durchführung akuter Haemodialysen, Hämofiltrationen, Hämoperfusionen oder bei Dauerdialyse-Patienten zur Überbrückung, bis andere Anschlußmöglichkeiten zur Verfügung standen. Ebenfalls wurde diese Methode auch als Gefäßzugang zur Plasmafiltration (Plasmapherese) verwendet.Wesentliche Komplikationen sind nicht aufgetreten. Ihre Häufigkeit ist aufgrund von Literaturangaben und eigener Erfahrungen gegenüber den anderen Zugangswegen geringer. Die Katheterisierung der V. cava superior über V. jugularis interna erscheint somit als geeignetes Verfahren, um schnell und ohne großen Aufwand eine Anschlußmöglichkeit zur Haemodialyse, Haemofiltration, Haemoperfusion oder Plasmafiltration zu schaffen.     

Continuous Renal Replacement Therapies

Continuous Renal Replacement Therapy (CRRT) is frequently used in patients admitted to intensive care units with multiple organ failure and acute renal failure. These patients are prone to developing hypotension making it very difficult to use conventional haemodialysis for their treatment. When compared to conventional haemodialysis CRRT has obvious clinical advantages. These advantages are mostly due to slow volume and uraemic toxin removal leading to better haemodynamic tolerability for such patients. In our unit during the year 2000, 58 patients were submitted to CRRT: 14 of the patients underwent treatment with continuous veno‐venous haemofiltration and 44 were submitted to continuous veno‐venous haemodiafiltration. The mean patient age was 61.7 years (range: 20–87), 36 male and 22 females. Twenty patients (43.1%) had sepsis, 18 (31%) were post open‐heart surgery, 7 (12%) had multiple organ failure, 4 (6.9%) were polytraumatised, 3 (5.2%) were post neurosurgery and 1 (1.8%) was a liver transplant patient. Despite the grave prognosis of these patients, 22 (37.8%) survived and 36 (62.2%) died. Of the patients that survived, 10 (17.2%) recovered renal function and 12 (20.6%) remained on a regular haemodialysis programme. The authors conclude that CRRT seems to be an alternative to conventional haemodialysis for the treatment of those patients with acute renal failure.