Jean Cardinal

Myoglobin clearance and removal during continuous venovenous hemofiltration.

Abstract Myoglobin has a relatively high molecular weight of 17,000 Da and is poorly cleared by dialysis (diffusion). However, elimination of myoglobin might be enhanced by an epuration modality based on convection for solute clearances. We present a single case of myoglobin-induced renal failure (peak creatine kinase level: 313,500 IU/l) treated by continuous venovenous hemofiltration (CVVH). Our purpose was to evaluate the efficiency of such a modality using an ultrafiltration rate of 2 to 3 l/h for myoglobin removal and clearance. The hemofilter was a 0.9 m2 polyacrylonitrile (AN69) membrane Multiflow-100 (Hospal-Gambro, St-Leonard, Canada) and the blood flow rate was maintained at 150 ml/min by an AK-10 pump (Hospal-Gambro, St-Leonard, Canada). The ultrafiltration bag was placed 60 cm below the hemofilter and was free of pump control or suction device. Serum myoglobin concentration was 92,000 μg/l at CVVH initiation and dropped to 28,600 μg/l after 18 h of the continuous modality. The mean sieving coefficient for myoglobin was 0.6 during the first 9 h of therapy and this decreased to 0.4 during the following 7 h. Mean clearance of myoglobin was 22 ml/min, decreasing to 14 ml/min during corresponding periods, while the mean ultrafiltration rates were relatively stable at 2,153 ± 148 ml/h and 2,074 ± 85 ml/h, respectively. In contrast to myoglobin, the sieving coefficeint for urea, creatinine, and phosphorus remained stable at 1.0 during the first 16 h of CVVH. More than 700 mg of myoglobin were removed by CVVH during the entire treatment.¶In conclusion, considerable amounts of myoglobin can be removed by an extracorporeal modality allowing important convective fluxes and middle molecule clearances, such as CVVH at a rate of 2 to 3 l/h using an AN69 hemofilter. If myoglobin clearance had been maintained at 22 ml/min, 32 l of serum would have been cleared per day. However, the sieving coefficient of myoglobin decreased over time, probably as a consequence of protein coating and/or blood clotting of the hemofilter. Whereas myoglobin can be removed by CVVH, it remains unknown at this point if such a modality, applied early, can alter or shorten the course of myoglobinuric acute renal failure.

Ammonium acid urate crystal formation in adult North American stone-formers

Although ammonium acid urate (AAU) stones are endemic in Asia, pure AAU calculi have almost disappeared from industrialized countries and clinical pathophysiologic relevance of sporadic stones containing AAU crystals is currently unknown. We reviewed 1,396 crystallographic stone analyses performed in our institution over a 10-year period. Prevalence of stones containing AAU crystals and predominantly AAU stones were 3.1% and 0.2%, respectively. In more than two thirds of cases, AAU crystals represented less than 10% of stone crystal composition. No pure AAU stone was found. According to crystalline predominance, 42%, 35%, and 12% of these calculi were uric acid, infectious, and calcium oxalate stones, respectively. AAU crystals were detected as discrete intercrystalline or peripheral deposits in 74.4% of stones. In only one calculus was AAU crystals detected in the nucleus. The hospital charts of 37 patients who presented with 43 calculi containing AAU crystals were also reviewed. The mean age was 53.1 +/- 16.6 years. Fifty-seven percent of calculi were upper urinary tract stones and 43% were bladder stones. Upper urinary tract calculi were more frequently uric acid stones, followed by infectious and calcium oxalate stones. Lower urinary tract calculi were more frequently infectious stones, followed by uric acid stones. Upper urinary tract stones were passed spontaneously in 13 patients and removed surgically in nine patients. Nine of these subjects were idiopathic recurrent stone formers who had passed other calculi with no trace of AAU crystal. Fifty-seven percent of lower urinary tract stones were associated with documented bladder dysfunction. In conclusion, although AAU-containing urolithiases are occasionally seen in our population, predominantly or primarily AAU stones are exceptional. AAU crystal formation usually appears as a minor and secondary phenomenon of no primary pathophysiologic relevance in stone formation.

Kt/Vin Continuous Dialysis Techniques

If hemodialyzers are being reused, the federal regulations which incorporate the AAMI Recommended Practice for Reuse of Hemodialyzers should be followed closely. If hemodialyzers are being reused, a facilitybased CQI program should monitor delivered dialysis (KtlV urea or URR) in dialyzers with many reuses and those which are new or have been used infrequently. Urea clearance may decline with increasing reprocessing and reuse of hemodialyzers. In 34 units in New Jersey, Puerto Rico, and the U.S . Virgin Islands which reprocess dialyzers, mean delivered KtIV fell on average by 5% between the 4th and 14th use. More importantly, severe declines (20% or more) in KtIV were often observed. Since patient noncompliance accounts for most of the problem of missed or shortened treatments, focused counseling and renewed patient education efforts should be undertaken to stress the importance of achieving the desired amount of delivered dialysis and the severe consequences of inadequate dialysis. Deficiencies in delivered dialysis due to missed or shortened treatments are quantitatively signijkant. Over 7% of patients studied in New Jersey, Puerto Rico, and the U.S. Virgin Islands missed 10% or more of their prescribed therapy in a month. 14. Since nutritional status of dialysis patients is an important determinant of morbidity and mortality, attention to protein ( 1 g/kg/day) and caloric (30-35 kcal/kg/day) intake is appropriate. Actual body weight should be used in the assessment except with clinically relevant wasting or obesity where use of actual body weight will underestimate (in the instance of wasting) or overestimate (in the instance of obesity) nutritional needs. Nutritional monitoring by normalized protein catabolic rate (nPCR) and/or serum albumin andlor dietary records may be of value in recognizing malnutrition. In our network study, interdialytic weight gain (ID WG) was found to correlate with nPCR. Patients with 2-day IDWG of I to <2 kg were twice as likely as patients with IDWG of 3 to <4 kg to have a NPCR < I glkglday. Thus, whether the source of high ID WG is non-nutritive fluid excess or the fluid content offood needs to be considered to evaluate the level of IDWG.

Peritonitis in Continuous Ambulatory Peritoneal Dialysis: Impact of a Compulsory Switch From a Standard to a Y-Connector System in a Single North American Center

One hundred one continuous ambulatory peritoneal dialysis (CAPD) patients from a single North American center were analyzed in a retrospective and cross-over study for peritonitis rates using a standard system (Travenol System II) or a Y-shaped disconnect-disinfectant system (Travenol O-set). Twenty-one of 34 patients using the standard set (group I) had 53 episodes of peritonitis in 508 patient-months or one episode per 9.6 patient-months. Nine of 17 patients switching from the standard to the disconnect-disinfectant system (group II) experienced 22 episodes of peritonitis in 275 patient-months or one episode per 12.5 patient-months on the standard set, while six patients had 10 episodes of peritonitis in 275 patient-months or one episode per 27.5 patient-months on the disconnect-disinfectant system (P less than 0.04). Twenty-eight of 67 new CAPD patients starting on the disconnect-disinfectant system (group III) had 37 episodes of peritonitis in 1,086 patient-months or one episode per 29.4 patient-months (P less than 0.01 v group I). Exit-site infections (ESI) occurred in 35.3% of patients using the standard set versus 34.3% of those using the O-set. The presence of an ESI was not associated with a higher risk of peritonitis, but modified the bacteriological profile of subsequent peritonitis episodes in patients using the O-set, favoring the organisms isolated from the exit site. Decreases in peritonitis rates with the O-set were due to a reduction of peritonitis episodes secondary to most bacterial agents and not only to skin organisms. Diabetics using intraperitoneal insulin had similar peritonitis and ESI rates as nondiabetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular potassium activity in mammalian proximal tubule: Effect of perturbations in transepithelial sodium transport

SummaryIntracellular potassium activity (aKi) was measured in control conditions in mid-cortical rabbit proximal convoluted tubule using two methods: (i) by determination of the K+ equilibrium potential (EK) using Ba2+-induced variations in the basolateral membrane potential (VBL) during transepithelial current injections and (ii) with double-barrel K-selective microelectrodes. Using the first method, the meanVBL was −48.5±3.2 mV (n=16) and the meanEK was −78.4±4.1 mV corresponding to aaKi of 68.7mm. With K-selective microelectrodes,VBL was −36.6±1.1 mV (n=19),EK was −64.0±1.1 mV andaKi averaged 40.6±1.7mm. While these lastEK andVBL values are significantly lower than the corresponding values obtained with the first method (P<0.001 andP<0.01, respectively), the electrochemical driving force for K transport across the basolateral membrane (μK =VBL −EK) is not significantly different for both techniques (30.1±3.3 mV for the first technique and 27.6±1.8 mV for ion-selective electrodes). This suggests an adequate functioning of the selective barrel but an underestimation ofVBL by the reference barrel of the double-barrel microelectrode. Such double-barrel microelectrodes were used to measure temporal changes inaKi andμK in different experimental conditions where Na reabsorption rate (JNa) was reduced.aKi was shown to increase by 12.2±2.7 (n=5) and 14.1±4.4mm (n=5), respectively, whenJNa was reduced by omitting in the luminal perfusate: (i) 5.5mm glucose and 6mm alanine and (ii) glucose, alanine, other Na-cotransported solutes and 110mm Na. In terms of the electrochemical driving force for K exit across the basolateral membrane,μK, a decrease of 5.4±2.0 mV (P<0.05,n=5) was measured when glucose and alanine were omitted in the luminal perfusate whileμK remained unchanged whenJNa was more severely reduced (mean change =−1.7±2.1 mV, NS,n=5). In the latter case, this means that the electrochemical driving force for K efflux across the basolateral membrane has not changed while both the active influx through the Na−K pump and the passive efflux in steady state are certainly reduced. If the main pathway for K transport is through the basolateral K conductance, this implies that this conductance must have decreased in the same proportion as that of the reduction in the Na−K pump activity.

Continuous Renal Replacement Therapy after Cardiac Surgery

Background/Aims: To evaluate the outcome of patients who require continuous renal replacement therapy (CRRT) following cardiac surgery. Methods: All patients who received CRRT after cardiac surgery over more than 4 years at the Surgical Intensive Care Unit of the Montreal Heart Institute were reviewed. Among 5,564 consecutive patients, 85 underwent CRRT postoperatively. Results: The mean delay between surgery and CRRT initiation was 5 days, and the duration of CRRT was 9 days, without a difference between survivors and non-survivors. Delivered clearances with CRRT were estimated at 25–28 ml/min (≈40 liters/day), 29–32 ml/min (≈46 liters/day) and 17 ml/min (≈ 25 liters/day) for continuous veno-venous hemofiltration, continuous veno-venous hemodiafiltration and continuous veno-venous hemodialysis, respectively. In-hospital mortality was 43.5%. No difference in mortality was observed between patients with normal renal function at baseline and those with pre-operative renal dysfunction. Mortality was 33.3% after a coronary artery bypass graft (CABG), 57.1% after CABG and valve surgery, 60% after valve surgery, and 72.7% for redo-CABG or redo-valve surgery. 79% of survivors and 86% of non-survivors had received a cardiopulmonary bypass (p = NS). The Simplified Acute Physiology Score II upon intensive care unit (ICU) admission and the requirement of an intra-aortic balloon pump were higher in non-survivors (p < 0.05). The mean length of ICU and hospital stay was 27.4 and 34.2 days for survivors and 17.9 and 22.3 days for non-survivors, respectively (p < 0.05). Conclusions: Renal impairment is relatively common after cardiac surgery. The mortality of patients who required CRRT after cardiac surgery was 43.5% and was particularly influenced by the type of surgery.

Effect of meleate on membrane physical state of brush border and basolateral membranes of the dog kidney

The effects of maleate on the physical state of isolated brush border and basolateral membranes from dog kidney cortex have been studied by fluorescence polarization and ESR methods. Anisotropy of 1,6-diphenyl-1.3.5.-hexatriene and hyperfine splitting (2T parallel) of 5-doxylstearic acid in brush border and basolateral membranes were not significantly modified by the addition of 10(-2) M maleate after 60-90 min treatment. These findings further support the view that maleic acid nephropathy is not due to a direct effect of maleate on tubular membranes per se.