Relative contribution of residual renal function and peritoneal clearance to adequacy of dialysis: a reanalysis of the CANUSA study

Studies of the adequacy of peritoneal dialysis and recommendations have assumed that renal and peritoneal clearances are comparable and therefore additive. The CANUSA data were reanalyzed in an effort to address this assumption. Among the 680 patients in the original CANUSA study, 601 had all of the variables of interest for this report. Adequacy of dialysis was estimated from GFR (mean of renal urea and creatinine clearance) and from peritoneal creatinine clearance. The Cox proportional-hazards model was used to evaluate the time-dependent association of these independent variables with patient survival. For each 5 L/wk per 1.73 m(2) increment in GFR, there was a 12% decrease in the relative risk (RR) of death (RR, 0.88; 95% confidence interval [CI], 0.83 to 0.94) but no association with peritoneal creatinine clearance (RR, 1.00; 95% CI, 0.90 to 1.10). Estimates of fluid removal (24-h urine volume, net peritoneal ultrafiltration, and total fluid removal) then were added to the Cox model. For a 250-ml increment in urine volume, there was a 36% decrease in the RR of death (RR, 0.64; 95% CI, 0.51 to 0.80). The association of patient survival with GFR disappeared (RR, 0.99; 95% CI, 0.94 to 1.04). However, neither net peritoneal ultrafiltration nor total fluid removal was associated with patient survival. Although these results may be explained partly, statistically, by less variability in peritoneal clearance than in GFR, the latter seems to be physiologically more important than the former. The assumption of equivalence of peritoneal and renal clearances is not supported by these data. Recommendations for adequate peritoneal dialysis need to be reevaluated in light of these observations.

Canadian Hemodialysis Morbidity Study

The objective of this study was to determine the probabilities of specific morbid events or death among patients with end-stage renal disease (ESRD) treated by hemodialysis. A prospective cohort study was performed between March 1988 and September 1989 in 18 hemodialysis centers in 13 Canadian cities, representing about one third of the hemodialysis population in Canada. The inception cohort consisted of 496 patients entering hemodialysis who had survived 1 month. The few new hemodialysis patients who received erythropoietin (EPO) in the last 3 months of the study were excluded. Survival curves were compared using the Cox proportional hazards regression model. Older age and history of cardiovascular disease were independently associated with a greater probability of death. Age and history of cardiovascular disease were also associated with a greater probability of nonfatal circulatory events (myocardial infarction, angina requiring hospitalization, or stroke), while a serum albumin level less than or equal to 30 g/L (3.0 g dL) was associated with an increased probability of pulmonary edema. The probability of surviving 12 months without receiving a blood transfusion was 47.2% for males and 27.5% for females. The incidence of non-A, non-B hepatitis, as estimated by unexplained elevations in serum aspartate aminotransferase (AST) values, was not different between patients receiving and not receiving blood transfusions. The probability of hospitalization for any cause was greater for patients with grafts for vascular access than for those with fistulae, for those with a history of cardiovascular disease, for those with a serum albumin level less than or equal to 30 g/L, and for those with renal disease due to diabetes or vascular disease. Hospitalization due to circulatory disease was more likely among those with a history of cardiovascular disease and among those with a lower serum albumin level. Hospitalization for infectious disease was more likely among those with a lower serum albumin level and less likely among those with a fistula for vascular access. Among all patients receiving hemodialysis treatment for more than 6 months, there were 14.8 hospital days per year.(ABSTRACT TRUNCATED AT 400 WORDS)

Increased peritoneal membrane transport is associated with decreased patient and technique survival for continuous peritoneal dialysis patients. The Canada-USA (CANUSA) Peritoneal Dialysis Study Group

The objective of this study was to evaluate the association of peritoneal membrane transport with technique and patient survival. In the Canada-USA prospective cohort study of adequacy of continuous ambulatory peritoneal dialysis (CAPD), a peritoneal equilibrium test (PET) was performed approximately 1 mo after initiation of dialysis; patients were defined as high (H), high average (HA), low average (LA), and low (L) transporters. The Cox proportional hazards method evaluated the association of technique and patient survival with independent variables (demographic and clinical variables, nutrition, adequacy, and transport status). Among 606 patients evaluated by PET, there were 41 L, 192 LA, 280 HA, and 93 H. The 2-yr technique survival probabilities were 94, 76, 72, and 68% for L, LA, HA, and H, respectively (P = 0.04). The 2-yr patient survival probabilities were 91, 80, 72, and 71% for L, LA, HA, and H, respectively (P = 0.11). The 2-yr probabilities of both patient and technique survival were 86, 61, 52, and 48% for L, LA, HA, and H, respectively (P = 0.006). The relative risk of either technique failure or death, compared to L, was 2.54 for LA, 3.39 for HA, and 4.00 for H. The mean drain volumes (liters) in the PET were 2.53, 2.45, 2.33, and 2.16 for L, LA, HA, and H, respectively (P < 0.001). After 1 mo CAPD treatment, the mean 24-h drain volumes (liters) were 9.38, 8.93, 8.59, and 8.22 for L, LA, HA, and H, respectively (P < 0.001); the mean 24-h peritoneal albumin losses (g) were 3.1, 3.9, 4.3, and 5.6 for L, LA, HA, and H, respectively (P < 0.001). The mean serum albumin values (g/L) were 37.8, 36.2, 33.8, and 32.8 for L, LA, HA, and H, respectively (P < 0.001). Among CAPD patients, higher peritoneal transport is associated with increased risk of either technique failure or death. The decreased drain volume, increased albumin loss, and decreased serum albumin concentration suggest volume overload and malnutrition as mechanisms. Use of nocturnal cycling peritoneal dialysis should be considered in H and HA transporters.

The diagnosis and prognosis of autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease is usually caused by a mutant gene at the PKD1 locus on the short arm of chromosome 16, but in about 4 percent of families with the disorder it is caused by unknown mutations elsewhere in the genome. The natural course of the disease in both genetic forms is not well characterized.

METHODS

We studied 17 families with autosomal dominant polycystic kidney disease to compare presymptomatic diagnosis by ultrasonography with diagnosis by genetic-linkage studies and to relate clinical variation of the disease to whether the PKD1 mutation was implicated.

RESULTS

In 10 families the disorder was found to cosegregate with polymorphic DNA markers flanking the PKD1 locus, in 2 families it did not, and in 5 families linkage could not be determined. In the 10 families with the PKD1 mutation, 46 percent of the members less than 30 years old who had a 50 percent risk of inheriting a mutation had renal cysts, as compared with 11 percent of the members of the two families without linkage (P less than 0.001). In the PKD1 families, all 67 diagnoses made by ultrasonography were confirmed by determination of the genotype as inferred from linkage. Forty of 48 members (83 percent) less than 30 years old who inherited the PKD1 mutation had renal cysts. All 27 members 30 years old or older who inherited the mutation had renal cysts, suggesting that the probability of a false negative diagnosis did not exceed 0.13 in this age group (P less than 0.05). The mean (+/- SE) age at the onset of end-stage renal disease among members of the PKD1 families was 56.7 +/- 1.9 years, as compared with 69.4 +/- 1.7 years among members with cysts in the families without linkage (P = 0.0025). Hypertension and renal impairment were less frequent and occurred later in the families without the PKD1 mutation.

CONCLUSIONS

At present, in most persons with a 50 percent risk of autosomal dominant polycystic kidney disease, imaging techniques are the only mode of reaching a diagnosis before symptoms appear. In such persons a negative ultrasonographic study during early adult life indicates that the likelihood of inheriting a PKD1 mutation is small. In the few who inherit a non-PKD1 mutation for polycystic kidney disease, renal failure is likely to occur relatively late in life.

Comparison of mortality risk for dialysis patients and cadaveric first renal transplant recipients in Ontario, Canada

In population-based studies, renal transplantation has been shown to improve survival compared to dialysis patients awaiting transplantation in the United States. However, dialysis mortality in the United States is higher than in Canada. Whether transplantation offers a survival advantage in regions where dialysis survival is superior to that in the United States is uncertain. This study examines a cohort of 1156 patients who started end-stage renal disease (ESRD) therapy and were wait-listed for cadaveric renal transplantation in the province of Ontario, Canada between January 1, 1990 and December 31, 1994. Patients were followed from wait-listing for renal transplant (n = 1156), to cadaveric first renal transplant (n = 722), to death, or to study end (December 31, 1995). The annual crude mortality rates for wait-listed dialysis patients and transplanted patients were 5.0 and 3.4%, respectively. In Cox proportional hazards models, mortality in wait-listed patients was associated with increased age and diabetes, but not time from onset of ESRD to wait-listing. Factors associated with death following transplantation include older age, diabetes, and longer time spent on the waiting list before transplantation. In a time-dependent Cox regression model, the relative risk of death after transplantation compared to dialysis varied in a time-dependent manner. Covariates associated with increased risk included older age, diabetes, and time from onset of ESRD to wait-listing. The average relative risk (RR) of dying was 2.91 (95% confidence interval [CI], 1.34 to 6.32) in the first 30 d after transplantation, but was significantly lower 1 yr after transplantation (RR 0.25; 95% CI, 0.14 to 0.42), indicating a beneficial long-term effect when compared to wait-listed dialysis patients. This long-term benefit was most evident in subgroups of patients with diabetes (RR 0.38; 95% CI, 0.17 to 0.87) and glomerulonephritis (RR 0.13; 95% CI, 0.04 to 0.39) as the cause of ESRD. The survival advantage associated with renal transplantation is evident in this cohort of patients with a lower wait-listed dialysis mortality than that reported previously in the United States. The magnitude of the treatment effect is consistent across studies.

Effect of B-vitamin therapy on progression of diabetic nephropathy: a randomized controlled trial

CONTEXT

Hyperhomocysteinemia is frequently observed in patients with diabetic nephropathy. B-vitamin therapy (folic acid, vitamin B(6), and vitamin B(12)) has been shown to lower the plasma concentration of homocysteine.

OBJECTIVE

To determine whether B-vitamin therapy can slow progression of diabetic nephropathy and prevent vascular complications.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, randomized, double-blind, placebo-controlled trial (Diabetic Intervention with Vitamins to Improve Nephropathy [DIVINe]) at 5 university medical centers in Canada conducted between May 2001 and July 2007 of 238 participants who had type 1 or 2 diabetes and a clinical diagnosis of diabetic nephropathy.

INTERVENTION

Single tablet of B vitamins containing folic acid (2.5 mg/d), vitamin B(6) (25 mg/d), and vitamin B(12) (1 mg/d), or matching placebo.

MAIN OUTCOME MEASURES

Change in radionuclide glomerular filtration rate (GFR) between baseline and 36 months. Secondary outcomes were dialysis and a composite of myocardial infarction, stroke, revascularization, and all-cause mortality. Plasma total homocysteine was also measured.

RESULTS

The mean (SD) follow-up during the trial was 31.9 (14.4) months. At 36 months, radionuclide GFR decreased by a mean (SE) of 16.5 (1.7) mL/min/1.73 m(2) in the B-vitamin group compared with 10.7 (1.7) mL/min/1.73 m(2) in the placebo group (mean difference, -5.8; 95% confidence interval [CI], -10.6 to -1.1; P = .02). There was no difference in requirement of dialysis (hazard ratio [HR], 1.1; 95% CI, 0.4-2.6; P = .88). The composite outcome occurred more often in the B-vitamin group (HR, 2.0; 95% CI, 1.0-4.0; P = .04). Plasma total homocysteine decreased by a mean (SE) of 2.2 (0.4) micromol/L at 36 months in the B-vitamin group compared with a mean (SE) increase of 2.6 (0.4) micromol/L in the placebo group (mean difference, -4.8; 95% CI, -6.1 to -3.7; P < .001, in favor of B vitamins).

CONCLUSION

Among patients with diabetic nephropathy, high doses of B vitamins compared with placebo resulted in a greater decrease in GFR and an increase in vascular events.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN41332305.

Plasma exchange when myeloma presents as acute renal failure: a randomized, controlled trial

BACKGROUND

Two small, randomized trials provide conflicting evidence about the benefits of plasma exchange for patients with acute renal failure at the onset of multiple myeloma.

OBJECTIVE

To assess the effect of 5 to 7 plasma exchanges on a composite outcome in patients with acute renal failure at the onset of multiple myeloma.

DESIGN

Randomized, open, controlled trial, stratified by chemotherapy and dialysis dependence, conducted from 1998 to 2004.

SETTING

Hospital plasma exchange units in 14 Canadian medical centers.

PARTICIPANTS

104 patients between 18 and 81 years of age with acute renal failure at the onset of myeloma.

INTERVENTION

Study participants were randomly assigned to conventional therapy plus 5 to 7 plasma exchanges of 50 mL per kg of body weight of 5% human serum albumin for 10 days or conventional therapy alone. Ninety-seven participants completed the 6-month follow-up.

MEASUREMENTS

The primary outcome was a composite measure of death, dialysis dependence, or glomerular filtration rate less than 0.29 mL x s(-2) x m(-2) (<30 mL/min per 1.73 m2).

RESULTS

At enrollment, the plasma exchange and control groups were similar for dialysis dependence, chemotherapy, sex, age, hypercalcemia, serum albumin level, 24-hour urine protein level, serum creatinine level, and Durie-Salmon staging. The primary composite end point occurred in 33 of 57 (57.9%) patients in the plasma exchange group and in 27 of 39 (69.2%) patients in the control group (difference between groups, 11.3% [95% CI, -8.3% to 29.1%]; P = 0.36). One third of patients in each group died.

LIMITATIONS

The study was small, used a composite outcome, and did not use renal biopsy as an inclusion criterion. Recruiting physicians were blinded to treatment allocation but not to treatment thereafter.

CONCLUSIONS

In patients with acute renal failure at the onset of multiple myeloma, there is no conclusive evidence that 5 to 7 plasma exchanges substantially reduce a composite outcome of death, dialysis dependence, or glomerular filtration rate less than 0.29 mL.s(-2).m(-2) (<30 mL/min per 1.73 m2) at 6 months.

The quality of life in renal transplantation--a prospective study

Methodologically sound measures of quality of life are required to judge accurately the impact of successful renal transplantation on patient well-being. The time trade-off (TTO) method is a reproducible and valid measure which we used to prospectively assess changes in the quality of life of 27 patients on maintenance dialysis who subsequently underwent renal transplantation. TTO scores approaching 0 signify a very poor quality of life, while scores approaching 1 represent perfect health. Of 98 dialysis patients who completed baseline TTO interviews, 31 consecutive patients subsequently received 28 cadaveric and 3 living related kidney transplants. Four of 31 patients did not complete a second TTO assessment, because of death in 2 patients and graft loss in 2 others. The remaining 27 patients completed a second TTO interview an average of 30.9 months following transplantation (range 1.5-52, 95% confidence interval [CI] 24.4-37.5) and formed the study cohort. At the time of study the mean serum creatinine for the cohort was 173 mumol/L (range 90-290, 95% CI 152-195 mumol/L). The employment rate rose 27% following transplantation (P = 0.10); but when males alone were analyzed, a significant increase of 38% (P = 0.048) was noted. During the dialysis period, the mean baseline TTO score was 0.41 (95% CI 0.33-0.49), confirming the observations of others. Following transplantation, the mean TTO score rose to 0.74 (95% CI 0.67-0.81), a difference that is statistically significant (P < 0.001). The mean increase in TTO score observed as a result of successful transplantation was 0.33 (95% CI 0.26-0.40). This magnitude of improvement was found in 20 of 27 patients (74%), whose TTO scores lay within or above the 95% CI (0.26-0.40) for the mean change in score of 0.33. One patient's score fell, while the remaining 6 patients had improvements in their TTO score which fell below the lower 95% CI value (0.26) for the mean change in score. We conclude that the 95% CI of 0.26-0.40 identifies a range in which clinically important improvements in quality of life will be found for the majority of patients receiving successful kidney transplants.

Regular Monitoring of Access Flow Compared with Monitoring of Venous Pressure Fails to Improve Graft Survival

ABSTRACT. Regular vascular access blood flow (Qa) surveillance is recommended to detect graft stenosis; however, there is little evidence that monitoring and correcting with angioplasty improves graft survival. This blinded, randomized, controlled trial of 112 patients studied time to graft thrombosis and graft loss, comparing monthly Qa plus standard surveillance (dynamic venous pressure and physical examination) (treatment group) to standard surveillance alone (control group). Only the treatment group was referred for angiogram if Qa <650 ml/min or a 20% decrease in Qa from baseline. Percutaneous angioplasty was performed for stenosis >50%. The rate of graft thrombosis per patient-year at risk was 0.41 and 0.51 in the control and treatment groups, respectively. Fifty-one interventions (0.93/patient-years at risk) were performed in the treatment groupversus31 interventions (0.61/patient-years at risk) in the control group. There was no difference in time to graft loss (P= 0.890). In a multivariate analysis, aspirin (ASA) therapy at baseline was associated with an 84% reduction in risk of graft thrombosis (odds ratio [OR], 0.14;P= 0.002). Higher baseline Qa (OR, 0.84;P= 0.05) and longer interval since graft insertion (OR, 0.97;P= 0.07) were associated with a decrease in graft thrombosis. Results reveal that graft surveillance that uses Qa increases the detection of stenosis, compared with standard surveillance; however, intervention with angioplasty does not improve the time to graft thrombosis or time to graft loss. E-mail: louise.moist@lhsc.on.ca

Risk of bacteremia from temporary hemodialysis catheters by site of insertion and duration of use: a prospective study

BACKGROUND

Uncuffed, nontunneled hemodialysis catheters remain the preferred means to gain immediate access to the circulation for hemodialysis. Bacteremia is the primary complication that limits their use. The risk of bacteremia by site of insertion and duration of use has not been well studied.

METHODS

Two hundred eighteen consecutive patients who required a temporary hemodialysis catheter were prospectively followed.

RESULTS

Catheters were placed at 318 new insertion sites and remained in use for a total of 6235 days. The incidence of bacteremia was 5.4% after three weeks of placement in internal jugular vein and 10.7% after one week in femoral vein [relative risk for bacteremia 3.1 (95% CI, 1.8 to 5.2)]. The incidence of bacteremia was 1.9% one day after the onset of an exit site infection but increased to 13.4% by the second day if the catheter was not removed. Guidewire exchange for malfunction and patient factors did not significantly affect the risk of bacteremia.

CONCLUSIONS

Internal jugular catheters may be left in place for up to three weeks without a high risk of bacteremia, but femoral catheters in bed-bound patients should be removed after one week. Catheter exchanges over a guidewire for catheter malfunction do not increase bacteremia rates. Temporary catheters should be removed immediately if an exit site infection occurs.

The natural history of asymptomatic urolithiasis

An inception cohort of 107 patients was reviewed to establish the natural history of asymptomatic urolithiasis. With an over-all mean followup of 31.6 months, 73 patients (68.2%) remained asymptomatic and were censored at the time of the last clinical visit. A symptomatic event developed in 34 patients (31.8%). Spontaneous passage occurred in 16 patients (15.0%), endoureteral removal was done in 6 (5.6%), percutaneous nephrostolithotomy was done in 3 (2.8%) and 9 (8.4%) were referred for therapeutic lithotripsy. Cumulative 5-year probability of a symptomatic event developing was 48.5%. A linear association was identified between the development of a symptomatic event and the number of previous stones as well as the number of asymptomatic stones at identification. A significant burden of illness is associated with an expectant strategy as an approach to asymptomatic urolithiasis. Of the patients who had a symptomatic event 47% had spontaneous stone passage, while 26.5% required urological intervention and 26.5% were referred for therapeutic lithotripsy. Prophylactic extracorporeal shock wave lithotripsy, although often advocated, has associated risks and is not always a benign procedure. A randomized controlled trial is required to evaluate properly the role of prophylactic lithotripsy versus an expectant strategy.

Age at clinical onset and at ultrasonographic detection of adult polycystic kidney disease: data for genetic counselling

Few reports are available on the age-related risk of relatives of affected persons to manifest adult polycystic kidney disease (APKD). For 371 persons in 17 kindreds, at risk for APKD by virtue of having an affected first degree relative, we calculated the estimated probability of clinical diagnosis of APKD to be 0.011 by age 20, 0.041 by age 30, 0.115 by age 40, 0.299 by age 50, and 0.404 by age 60 years (expected = 0.50). Ultrasonographic examination of 172 asymptomatic persons at risk showed definite APKD in 60. The probability of ultrasonographic detection of asymptomatic APKD is estimated as 0.222, 0.657, and 0.855 at age 5, 15, and 25 years, respectively. The probability of having APKD following normal ultrasonogram results (conservatively assuming 90% specificity) is estimated as 0.46, 0.28, and 0.14 for persons at 50% risk in their first, second, or third decade. The marginal benefit of ultrasound as a diagnostic test for APKD for persons in the second or third decade is estimated as 0.37 and 0.41, respectively for a "positive" test and 0.22 and 0.37 for a "negative" test.

A controlled trial of cyclosporine in patients with progressive membranous nephropathy. Canadian Glomerulonephritis Study Group

A controlled trial of cyclosporine in patients diagnosed with progressive membranous nephropathy (MGN) was carried out to determine whether cyclosporine (D) would be more effective than placebo (P) in reducing the rate of deterioration in renal function. Patients (N = 64) with MGN were placed on a restricted protein diet (< or = 0.9 g/kg) and followed closely for 12 months (Part 1). Patients at high risk of progression based on an absolute loss in creatinine clearance (CCr) of > or = 8 ml/min and persistent nephrotic range proteinuria (Pr) were selected and randomly assigned to either (D) (N = 9) or (P) (N = 8) for 12 months (Part 2). No differences in the two groups were noted at entry. After 12 months, the improvement in CCr slope in ml/min/month was significantly greater in the D patients (D + 2.1 vs. P + 0.5, mean difference 1.6; 95% CI 0.3 to 3.0, P < 0.02). This improvement was maintained in six of eight D (75%) over a mean follow-up period of 21 months. Daily Pr also improved with D (by month 3, D - 4.5 g/day vs. P + 0.7 g/day, P = 0.02) and was sustained in six of eight (75%) D patients. When Pr was expressed as a function of their concurrent CCr, the D versus P patients' time to halving was faster (P = 0.02) and absolute number higher (4/9 D vs 0/8 P). In the D group a trend towards worse hypertension and an increase in the number of transient rises in serum creatinine were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Recommended Clinical Practices for Maximizing Peritoneal Dialysis Clearances

Data from the Canada-U.S.A. (CANUSA) Study have recently confirmed a long-suspected linkage between total clearance and patient survival in peritoneal dialysis (PD). Recognizing that what we have historically accepted as adequate PD simply is not, the Ad Hoc Committee on Peritoneal Dialysis Adequacy met in January, 1996. This committee of invited experts was convened by Baxter Healthcare Corporation to prepare a consensus statement that provides clinical recommendations for achieving clearance guidelines for peritoneal dialysis. Through an analysis of 806 PD patients, the group concluded that adequate clearance delivered with PD can be achieved in almost all patients if the prescription is individualized according to the patient's body surface area, amount of residual renal function, and peritoneal membrane transport characteristics. Use of 2.5 L to 3.0 L fill volumes, the addition of an extra exchange, and giving automated peritoneal dialysis patients a “wet” day are all options to consider when increasing weekly creatinine clearance and KTN. Rather than specify a single clearance or KTN target, the recommended clinical practice is to provide the most dialysis that can be delivered to the individual patient, within the constraints of social and clinical circumstances, quality of life, life-style, and cost. The challenge to PD practitioners is to make prescription management an integral part of everyday patient management. This includes assessment of peritoneal membrane permeability, measurement of dialysis and residual renal clearance, and adjustment of the dialysis prescription when indicated.

Early diagnosis of acute myocardial infarction based on assay for subforms of creatine kinase-MB

Thrombolytic therapy for patients with acute myocardial infarction (AMI) has produced the need for an accurate early diagnostic marker. We previously developed and assessed an assay for the creatine kinase (CK)-MB subforms; assay time is 25 minutes. Plasma MB2 (tissue subform) activity, MB1 (plasma-modified subform) activity, and MB2/MB1 ratio in 56 healthy individuals were 0.61 +/- 0.33 units/l, 0.63 +/- 0.33 units/l, and 0.94 +/- 0.39, respectively. Only one individual had both an MB2 activity greater than 1.0 units/l and an MB2/MB1 ratio of more than 1.5. Similar results were obtained in 50 hospitalized patients without cardiac disease; two of these patients had both an MB2 activity and an MB2/MB1 ratio greater than the cutoff values. Among 49 patients with AMI, MB2 activity and the MB2/MB1 ratio began to increase 2 hours after AMI; the ratio reached a plateau of 3.1 by 4-6 hours. The first available plasma sample was abnormal by the subform assay in 67% of patients and by a conventional MB assay in 27% of patients. Assay sensitivities in samples collected at 2-4, 4-6, and 6-8 hours after AMI were 59%, 92%, and 100% for the subform assay and 23%, 50%, and 71% for the conventional assay (p less than 0.03 versus subform assay at each time interval). False-negative results were obtained by the subform and conventional assays in 15 and 45 samples at a mean of 2.3 and 5.8 hours, respectively. Subform assay provides rapid and reliable diagnosis of AMI within 4-6 hours after the onset of symptoms, which is 6 hours before conventional CK-MB assays are accurate.

Quality of life of patients with ulcerative colitis preoperatively and postoperatively

Two instruments, the time trade-off technique and direct questioning of objectives, were used to assign the worth (utility) of the perceived quality of life of patients who had ulcerative colitis requiring surgery. Utilities ranged from 0 to 1 with 0 signifying death and 1 signifying full health. Two groups of patients were studied. Group 1 consisted of 20 patients (14 male and 6 female; mean age, 34.0 +/- 10.3 years) who were studied preoperatively and 1 year postoperatively. The mean preoperative utility was 0.58 +/- 0.34 using the time trade-off technique and 0.38 +/- 0.27 using the direct questioning of objectives. Mean utilities were significantly higher postoperatively, 0.98 +/- 0.07 using the time trade-off technique and 0.88 +/- 0.19 using the direct questioning of objectives (P less than 0.05). Group 2 included 93 patients who had had surgery at least 1 year previously. Twenty-eight had conventional ileostomies, 28 had Kock pouches, and 37 had ileal reservoirs. Mean utilities for these three subgroups ranged from 0.87 +/- 0.18 to 0.97 +/- 0.6. No significant differences were detected among the three subgroups. This study suggests that quality of life is improved after surgery for ulcerative colitis and is high irrespective of the surgical procedure.

An evidence-based approach to earlier initiation of dialysis

The objective was to review evidence addressing the optimal time to initiate dialysis treatment. The database was derived from an evidence-based review of the medical literature and from the Canada-United States peritoneal dialysis study. The publications were divided into (1) those addressing the clinical impact of early versus late referral to a dialysis program; (2) those evaluating the association between residual renal function at initiation of dialysis and the concurrent nutritional status; (3) those evaluating the association between residual renal function at initiation of dialysis and subsequent clinical outcomes, including patient survival. There were five studies evaluating early versus late referral, three cohort design and two case-control design. Late referrals had worse outcomes than early referrals. The former had more serious comorbidity and many had been noncompliant with follow-up. The latter were more likely to have hereditary renal disease. Renal function was slightly worse at initiation among those referred late. Three studies addressed the association between renal function at initiation of dialysis and concurrent nutritional status. Two showed decreased protein intake with diminished glomerular filtration rate (GFR). Poor nutritional status is associated with decreased patient survival among both incident and prevalent dialysis patients. The third study reported excellent patient survival among patients with late initiation of dialysis. These patients had received a supplemented low-protein diet and were not malnourished at initiation of dialysis. Three groups have studied the association between GFR at initiation of dialysis and clinical outcomes. Decreased GFR at initiation of dialysis is associated with a increased probability of hospitalization and death. None of these studies has used the rigorous randomized clinical trial design, and they are therefore subject to bias. Referral time bias, comorbidity, patient compliance, and starting time bias are potential confounders. A randomized clinical trial is required to resolve this important issue. However, there is sufficient evidence to justify initiation of dialysis at a Ccr of 9 to 14 mL/min if there is any clinical or laboratory evidence of malnutrition.

Effect of atenolol on birth weight

To investigate the possible harmful effects of early antihypertensive drug therapy with atenolol versus other therapies on pregnancy outcome, we reviewed the records of 398 women referred to our antenatal hypertension clinic between 1980 and 1995. Babies born to women taking atenolol were significantly lighter than babies born to women taking other beta blockers, other antihypertensive drugs, or no therapy, suggesting that atenolol might be detrimental in early pregnancy.

Prognosis of adult onset polycystic kidney disease re-evaluated

To appraise the prognosis of adult onset polycystic kidney disease (APKD), an inception cohort containing 140 subjects from 17 kindreds was assembled. Multiple renal cysts, demonstrable by ultrasonography, or clinical APKD, or both were present in 100 subjects. APKD was predicted in 32 subjects unavailable for ultrasonography and could not be excluded in eight deceased subjects. All had been at risk for endstage renal disease (ESRD) since birth. The probability of either developing ESRD, requiring dialysis or transplantation, or dying was estimated using a time-to-event analysis. The earliest age at which ESRD occurred was 36 years. For those with APKD, the probability of being alive and not having ESRD was 77% by age 50, 57% by age 58, and 52% by age 73 years. Excluding those predicted to have APKD changes these probabilities to 75, 53, and 47%, respectively. The serum creatinine values were less than 1.5 mg/dl for most subjects who had not developed ESRD. The prognosis for subjects with APKD is much better than most reports suggest and can be estimated from the time-to-event data presented.

Neurotrophin modulation of NMDA receptors in cultured murine and isolated rat neurons

Neurotrophin modulation of NMDA receptors in cultured murine and isolated rat neurons. J. Neurophysiol. 78: 2363-2371, 1997. Patch-clamp and calcium imaging techniques were used to assess the acute effects of the neurotrophins, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and nerve growth factor (NGF), on the responses of cultured and acutely isolated hippocampal and cultured striatal neurons to the glutamate receptor agonist N-methyl--aspartic acid (NMDA). The effects of BDNF on NMDA-activated currents were examined in greater detail. Currents evoked by NMDA, and the accompanying changes in intracellular calcium, were enhanced by low concentrations of the neurotrophins (1-20 ng/ml). The potentiation by the neurotrophins was rapid in onset and offset (<1 s). The neurotrophins also reduced desensitization of these currents in most cells. The enhancement of NMDA-activated currents by BDNF was observed using both perforated and whole cell patch recording techniques and could be demonstrated in outside-out patches. Furthermore, its effects were not attenuated by pretreatment with the protein kinase inhibitors genistein or 1-(5-isoquinolynesulfony)2-methylpiperazine (H7). Therefore, the actions of BDNF do not appear to be mediated by phosphorylation. Similar enhancements were observed with NT-3 and NT-4 and with NGF despite the fact that hippocampal neurons lack TrkA receptors. All together this evidence suggests that the enhancement of NMDA-evoked currents is unlikely to be mediated through the activation of growth factor receptors. Modulation of NMDA responses by BDNF was dependent on the concentration of extracellular glycine. The most pronounced potentiation by BDNF was observed at low concentrations, whereas no potentiation was observed in saturating concentrations of glycine, suggesting that BDNF may have increased the affinity of the NMDA receptor for glycine. However, the competitive glycine-site antagonist 7-chloro-kynurenic acid blocked the enhancement by BDNF without shifting the dose-inhibition relationship for this antagonist, and Mg2+ consistently depressed the potentiation of NMDA-evoked currents by BDNF, indicating that BDNF does not alter glycine affinity. BDNF also reversibly increased the probability of opening of NMDA channels recorded from outside-out patches taken from cultured hippocampal neurons. Other unrelated peptides including dynorphin and somatostatin also caused a glycine-dependent enhancement of NMDA currents and depressed the currents in saturating concentrations of glycine. In contrast, a shortened analogue dynorphin (6-17), which lacks N-terminus glycine residues, and another peptide met-enkephalin were without effects on NMDA currents recorded in low concentrations of glycine. Our results suggest that neurotrophins and other peptides can serve as glycine-like ligands for the NMDA receptor.

A prospective randomized trial of plasma exchange as additive therapy in idiopathic crescentic glomerulonephritis. The Canadian Apheresis Study Group

Sixty-three patients with crescentic glomerulonephritis (cellular crescents in greater than 50% of glomeruli) were considered for a prospective randomized trial comparing intravenous methylprednisolone, prednisone, and azathioprine with and without plasma exchange. Of 32 patients who fulfilled the inclusion criteria for this study, 16 were randomly assigned to receive drug therapy (control) and 16 to receive plasma exchange as well. The randomization was stratified for initial need of dialysis, and the presence of oliguria and sclerosis. Renal pathology was similar in the two groups of patients. There was no significant difference in the number of patients initially on dialysis who were able to discontinue it during the study (2/7 control v 3/4 plasma exchange), whereas no control but two plasma exchange-treated patients started dialysis during the study. Serum creatinine at randomization was similar in the two groups: 769 +/- 486 mumol/L (8.7 +/- 5.5 mg/dL) in the control group versus 643 +/- 275 mumol/L (7.3 +/- 3.1 mg/dL) in the plasma exchange group. There was no significant difference between the two groups in mean serum creatinine, change in serum creatinine, change in reciprocal, or change in logarithm of serum creatinine at 1, 3, 6, or 12 months following randomization. Power calculation, assuming a 20% difference would be clinically relevant, was 0.94 at 12 months. There was significant morbidity in both groups; there were two deaths within 1 year of randomization, both of pulmonary infection and both in the plasma exchange group. We conclude that plasma exchange offers no additional therapeutic benefit to patients with idiopathic rapidly progressive glomerulonephritis (RPGN) who are not dialysis-dependent at presentation.

Hemodialysis for methanol intoxication

We describe nine patients with methyl alcohol poisoning who were treated with hemodialysis. The time from ingestion to dialysis varied from 4 to 100 hours. Predialysis blood methanol levels ranged from 3 to 570 mg/dl. All patients were acidotic and had an increased anion gap. Two patients died, seven recovered, but three had permanent visual impairment. There was little correlation between the blood methanol level or anion gap and visual outcome. The interval from ingestion to treatment appears to be more important than the initial biochemical status. We recommend prompt hemodialysis if the blood methanol level is above 50 mg/dl, when an amount of methanol exceeding the minimal lethal dose (30 ml) is known to have been ingested, when there is evidence of acidosis or when an abnormality has developed in vision, funduscopic examination or mental state. Concurrent therapy with alkali and ethanol is vital.