Association of Longitudinal B-Type Natriuretic Peptide Monitoring With Kidney Failure in Patients With CKD: A Cohort Study

RATIONALE & OBJECTIVE

Both hypervolemia and hypovolemia are associated with chronic kidney disease (CKD) progression. Although longitudinal monitoring of B-type natriuretic peptide (BNP) may aid physicians' decision making about the optimization of volume status, its clinical benefit remains uncertain in CKD. This study assessed the association between BNP monitoring and the risk of incident kidney replacement therapy (KRT).

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

A total of 2,998 outpatients with stages 3-5 of nondialyzed CKD referred to the department of nephrology at an academic hospital.

EXPOSURE

BNP monitoring.

OUTCOME

KRT, acute kidney injury (AKI), and heart failure hospitalization.

ANALYTICAL APPROACH

Marginal structural models, which create a balanced pseudo population at each time point, were applied to account for potential time-dependent confounders. Inverse probability weighted pooled logistic regression models were employed to estimate hazard ratios.

RESULTS

At baseline, the median age and estimated glomerular filtration rate were 66 years and 38.1mL/min/1.73m2, respectively. During the follow-up period (median, 5.9 [IQR, 2.8-9.9] years), 449 patients required KRT, 765 had AKI, and 236 were hospitalized for heart failure. After adjustment for time-updated clinical characteristics and physician-specific practice styles, BNP monitoring was associated with lower risks of KRT (HR, 0.44 [95% CI, 0.21-0.92]), AKI (HR, 0.36 [95% CI, 0.18-0.72]), and heart failure hospitalization (HR, 0.37 [95% CI, 0.14-0.95]). The association between BNP monitoring and KRT was attenuated after additional adjustment for AKI or heart failure hospitalization as a time-varying covariate.

LIMITATIONS

Residual confounding by measured and unmeasured variables or indications for BNP measurements.

CONCLUSIONS

BNP monitoring was associated with a lower risk of KRT among patients with CKD that did not require dialysis. This association is potentially mediated through a reduced risk of AKI or heart failure hospitalization.

PLAIN-LANGUAGE SUMMARY

Both volume overload and volume depletion are deleterious to kidney function. B-type natriuretic peptide (BNP) is a biomarker that reflects volume status not only in heart failure but also in nondialysis chronic kidney disease (CKD). Although longitudinal BNP monitoring may aid physicians' decision making about the optimization of volume status, its clinical benefit remains uncertain in CKD. In this cohort study analyzing 2,998 patients with nondialyzed CKD, BNP monitoring was associated with a lower risk of kidney replacement therapy, acute kidney injury, and heart failure hospitalization over the follow-up period. The association with kidney replacement therapy may be mediated through a reduced risk of acute kidney injury or heart failure hospitalization. BNP monitoring may aid physicians in optimal fluid management, potentially conferring better kidney outcomes.

A Randomized Controlled Trial of Whole-Body Vibration on Gait Ability and Balance among Older Hemodialysis Patients

BACKGROUND

Gait abnormality is a serious problem among hemodialysis patients. Whole-body vibration is a simple exercise that induces sustained muscular contractions through mechanical vibrations. This training improved gait ability in older adults. We aimed to investigate the effect of whole-body vibration on balance and gait ability in older hemodialysis patients.

METHODS

We conducted a 12-week, open-label, multicenter, randomized controlled trial of 98 hemodialysis patients, who were aged ≥65 years, from three dialysis centers in Japan. Those who had difficulty walking alone or dementia were excluded. Patients were randomly allocated to the whole-body vibration group or control group. The training was performed for 3 minutes thrice a week on dialysis days. The primary outcome was the Timed Up and Go test. The secondary outcomes were the single-leg stand test and 30-second chair stand test.

RESULTS

The mean (SD) age of the participants was 76 (7) years. The mean (SD) Timed Up and Go test was 12.0 (6.6) and 11.8 (7.0) seconds in the whole-body vibration and control groups, respectively. During the 12-week study period, 6 (12%) of 49 patients in the whole-body vibration group and 3 (6%) of 49 patients in the control group dropped out. In the whole-body vibration group, 42 (86% of the randomly allocated patients) completed the training according to the protocol. The mean (SD) changes in the Timed Up and Go test were -1.1 (4.0) and -1.4 (4.4) seconds in the whole-body vibration and control groups, respectively (change, 0.3 seconds in the whole-body vibration group; 95% confidence interval, -1.4 to 2.0; P=0.71). The changes in the single-leg stand test and 30-second chair stand test did not differ significantly between groups. There were no musculoskeletal adverse events directly related to this training.

CONCLUSIONS

Whole-body vibration did not improve balance and gait ability.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Effect of Whole Body Vibration on Walking Performance in Elderly Hemodialysis Patients NCT04774731.

A heterozygous LAMA5 variant may contribute to slowly progressive, vinculin-enhanced familial FSGS and pulmonary defects

The LAMA5 gene encodes laminin α5, an indispensable component of glomerular basement membrane and other types of basement membrane. A homozygous pathological variant in LAMA5 is known to cause a systemic developmental syndrome including glomerulopathy. However, the roles of heterozygous LAMA5 gene variants in human renal and systemic diseases have remained unclear. We performed whole-exome sequencing analyses of a family with slowly progressive nephropathy associated with hereditary focal segmental glomerulosclerosis, and we identified what we believe to be a novel probable pathogenic variant of LAMA5, NP_005551.3:p.Val3687Met. In vitro analyses revealed cell type-dependent changes in secretion of variant laminin α5 laminin globular 4-5 (LG4-5) domain. Heterozygous and homozygous knockin mice with a corresponding variant of human LAMA5, p.Val3687Met, developed focal segmental glomerulosclerosis-like pathology with reduced laminin α5 and increased glomerular vinculin levels, which suggested that impaired cell adhesion may underlie this glomerulopathy. We also identified pulmonary defects such as bronchial deformity and alveolar dilation. Reexaminations of the family revealed phenotypes compatible with reduced laminin α5 and increased vinculin levels in affected tissues. Thus, the heterozygous p.Val3687Met variant may cause a new syndromic nephropathy with focal segmental glomerulosclerosis through possibly defective secretion of laminin α5. Enhanced vinculin may be a useful disease marker.

Intradialytic hypotension and objectively measured physical activity among patients on hemodialysis

BACKGROUND

Intradialytic hypotension is related to patient-reported outcomes such as post-dialysis fatigue, but its impact on physical activity has not been fully studied. We aimed to examine the relationship between intradialytic blood pressure (BP) and objectively measured physical activity.

METHODS

In this cross-sectional study, 192 hemodialysis patients underwent 4 weeks of physical activity measurement using triaxial accelerometers to measure step counts and moderate-to-vigorous physical activity (MVPA). Intradialytic BP parameters (pre-dialysis BP, post-dialysis BP, nadir BP, and fall in BP) were measured during all dialysis sessions. Mixed-effects linear regression models were used to analyze associations between intradialytic BP parameters and physical activity (1) after dialysis sessions on dialysis days and (2) on the following non-dialysis days.

RESULTS

The mean age of the patients was 71 years, and 47% had diabetes mellitus. Valid physical activity data were obtained in a total of 1938 dialysis days and 2629 non dialysis days. Lower nadir diastolic BP was significantly associated with lower step counts and shorter moderate-to-vigorous physical activity not only on dialysis days but also on the following non-dialysis days. Nadir diastolic BP showed a higher discrimination capacity for physical inactivity, defined as a step count < 4000 on non-dialysis days, than the other BP parameters. The optimal cutoff point of nadir diastolic BP for discriminating physical inactivity was 68 mmHg; its sensitivity and specificity were 66% and 67%, respectively.

CONCLUSIONS

Lower nadir diastolic BP was strongly associated with lower physical activity on both dialysis and non-dialysis days. Nadir diastolic BP may be a predictor for physical inactivity.

Mineralocorticoid Receptor Antagonist Use and Hard Renal Outcomes in Real-World Patients With Chronic Kidney Disease

BACKGROUND

Real-world evidence about mineralocorticoid receptor antagonist (MRA) use has been limited in chronic kidney disease, particularly regarding its association with hard renal outcomes.

METHODS

In this retrospective cohort study, adult chronic kidney disease outpatients referred to the department of nephrology at an academic hospital between January 2005 and December 2018 were analyzed. The main inclusion criteria were estimated glomerular filtration rate ≥10 and <60 mL/min per 1.73 m² and follow-up ≥90 days. The exposure of interest was MRA use, defined as the administration of spironolactone, eplerenone, or potassium canrenoate. The primary outcome was renal replacement therapy initiation, defined as the initiation of chronic hemodialysis, peritoneal dialysis, or kidney transplantation. A marginal structural model using inverse probability of weighting was applied to account for potential time-varying confounders.

RESULTS

Among a total of 3195 patients, the median age and estimated glomerular filtration rate at baseline were 66 years and 38.4 mL/min per 1.73 m², respectively. During follow-up (median, 5.9 years), 770 patients received MRAs, 211 died, and 478 started renal replacement therapy. In an inverse probability of weighting-weighted pooled logistic regression model, MRA use was significantly associated with a 28%-lower rate of renal replacement therapy initiation (hazard ratio, 0.72 [95% CI, 0.53-0.98]). The association between MRA use and renal replacement therapy initiation was dose-dependent (P for trend <0.01) and consistent across patient subgroups. The incidence of hyperkalemia (>5.5 mEq/L) was somewhat higher in MRA users but not significant (hazard ratio, 1.14 [95% CI, 0.88-1.48]).

CONCLUSIONS

MRA users showed a better renal prognosis across various chronic kidney disease subgroups in a real-world chronic kidney disease population.

Diagnosing metabolic acidosis in chronic kidney disease: importance of blood pH and serum anion gap

Metabolic acidosis is one of the most common complications of chronic kidney disease (CKD). It is associated with the progression of CKD, and many other functional impairments. Until recently, only serum bicarbonate levels have been used to evaluate acid-base changes in patients with reduced kidney function. However, recent emerging evidence suggests that nephrologists should reevaluate the clinical approach for diagnosing metabolic acidosis in patients with CKD based on two perspectives; pH and anion gap. Biochemistry and physiology textbooks clearly indicate that blood pH is the most important acid-base parameter for cellular function. Therefore, it is important to determine if the prognostic impact of hypobicarbonatemia varies according to pH level. A recent cohort study of CKD patients showed that venous pH modified the association between a low bicarbonate level and the progression of CKD. Furthermore, acidosis with a high anion gap has recently been recognized as an important prognostic factor, because veverimer, a nonabsorbable hydrochloride-binding polymer, has been shown to improve kidney function and decrease the anion gap. Acidosis with high anion gap frequently develops in later stages of CKD. Therefore, the anion gap is a time-varying factor and renal function (estimated glomerular filtration rate) is a time-dependent confounder for the anion gap and renal outcomes. Recent analyses using marginal structural models showed that acidosis with a high anion gap was associated with a high risk of CKD. Based on these observations, reconsideration of the clinical approach to diagnosing and treating metabolic acidosis in CKD may be warranted.

Time-updated anion gap and cardiovascular events in advanced CKD: a cohort study

Background

Studies examining associations between metabolic acidosis and cardiovascular events in chronic kidney disease (CKD) have shown conflicting results and have not differentiated between normal anion gap (hyperchloremic) acidosis and high anion gap acidosis. We aimed to examine the impact of normal and high anion gap acidosis, separately, on the risk of cardiovascular events among patients with CKD.

Methods

This retrospective cohort study included 1168 patients with an estimated glomerular filtration rate (eGFR) of 10–60 mL/min/1.73 m² and available data on anion gap. We analyzed the association of time-updated high anion gap (anion gap ≥9.2) with the rate of cardiovascular events using marginal structural models (MSMs) to account for time-dependent confounding. We also analyzed the association between time-updated normal anion gap acidosis (anion-gap-adjusted bicarbonate level ≤22.8 mEq/L) and cardiovascular events.

Results

The mean baseline eGFR of the cohort was 28 mL/min/1.73 m². The prevalence rates of high anion gap in CKD stages G3a, G3b, G4 and G5 were 20%, 16%, 27% and 46%, respectively. During a median follow-up period of 2.9 years, 132 patients developed cardiovascular events (3.3/100 patient-years). In MSMs, high anion gap was associated with a higher rate of cardiovascular events [hazard ratio (HR) 1.87; 95% confidence interval (95% CI) 1.13‒3.09; P = 0.02] and the composite of cardiovascular events or all-cause death (HR 3.28; 95% CI 2.19‒4.91; P < 0.001). Normal anion gap acidosis was not associated with cardiovascular events (HR 0.74; 95% CI, 0.47‒1.17; P = 0.2).

Conclusions

Among patients with advanced CKD, high anion gap was associated with an increased risk of cardiovascular events.

Association of Time-Updated Anion Gap With Risk of Kidney Failure in Advanced CKD: A Cohort Study

RATIONALE AND OBJECTIVE

High anion gap acidosis frequently develops in patients with advanced chronic kidney disease (CKD) and might be involved in kidney injury. Its impact on kidney outcomes, however, has not been well studied. We sought to examine the association between time-updated anion gap and the risk of kidney failure with replacement therapy (KFRT) among patients with advanced CKD.

STUDY DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

1,168 patients with CKD stages G3b-G5 who had available data on anion gap.

EXPOSURE

High time-updated anion gap defined as values ≥9.2 (top 25th percentile).

OUTCOMES

KFRT and death.

ANALYTICAL APPROACH

Marginal structural models (MSM) were fit to characterize the association between anion gap and study outcomes while accounting for potential time-dependent confounding.

RESULTS

The mean baseline eGFR of the study participants was 28 mL/min/1.73m². Over a median follow-up of 3.1 years, 317 patients progressed to KFRT (7.5/100 patient-years) and 146 died (3.5/100 patient-years). In the MSM, a high anion gap was associated with a higher rate of KFRT (hazard ratio [HR], 3.04; 95% confidence interval [CI], 1.94-4.75; P<0.001). This association was stronger in patients with baseline eGFR of <30 mL/min/1.73m² (P for interaction=0.05). High anion gap was also associated with a higher mortality rate (HR, 5.56; 95% CI, 2.95-10.5; P<0.001). Sensitivity analyses with different definitions of high anion gap showed similar results.

LIMITATIONS

Observational study design; selection bias due clinical indications for measuring anion gap.

CONCLUSION

Among patients with advanced CKD, high anion gap was associated with an increased risk of progression to KFRT and death.

Mean corpuscular hemoglobin concentration: an anemia parameter predicting cardiovascular disease in incident dialysis patients

BACKGROUND

Hemoglobin levels usually decline before dialysis initiation. The influence of overhydration on anemia progression and iron sequestration is poorly documented. Furthermore, clinical implications of anemia at dialysis initiation remain to be elucidated.

METHODS

This multicenter retrospective cohort study enrolled incident dialysis patients. The patients were stratified by tertiles of overhydration rate (OH-R) defined by (BW - DW)/DW*100 (BW: body weight just before dialysis initiation, DW: dry weight). Time courses (6 months before, to 1 month after, dialysis initiation) of hemoglobin, C-reactive protein (CRP), and iron sequestration index (ISI) were examined using mixed effects models. We used Cox models to identify anemia parameters predicting subsequent cardiovascular disease (CVD).

RESULTS

Among the 905 enrolled patients, hemoglobin levels gradually decreased before dialysis initiation and rapidly increased thereafter. An inverse V-shaped time course was observed for CRP and ISI with an increase during dialysis initiation. Patients with a higher OH-R showed lower hemoglobin levels along with higher CRP and ISI levels before dialysis initiation. Mean corpuscular hemoglobin concentration (MCHC) was more stable before dialysis initiation than were mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). Low MCHC (< 32 g/dL) was independently associated with the incidence of nonatherosclerotic CVD. Patients with low MCHC tended to have increased left ventricular wall thickness and left atrial diameter.

CONCLUSIONS

Progression of anemia before dialysis among overhydrated patients may mainly occur through hemodilution and iron sequestration partly induced by inflammation. Low MCHC reflects left atrial overload and left ventricular hypertrophy and hence may predict nonatherosclerotic CVD.

Cyclosporine A Treatment of Proteinuria in a New Case of MAFB-Associated Glomerulopathy without Extrarenal Involvement: A Case Report

The MAFB gene encodes an important basic leucine zipper transcription factor that functions in glomerular podocytes, macrophages, and osteoclasts. Recently, MAFB was identified as the gene that was responsible for causing nephropathy with focal segmental glomerulosclerosis (FSGS) with multicentric carpotarsal osteolysis (MCTO) or Duane retraction syndrome (DRS). Here, we describe a patient with nephropathy associated with FSGS who exhibited a novel stop-gain variant in the MAFB gene (NM_005461:c.590C>A (p.Ser197Ter)). The patient's father exhibited proteinuria with FSGS with possible DRS, whereas the patient exhibited nephropathy with FSGS and nearly normal eye movement and hearing function, as well as intact bone structure in the extremities. Conventional oral steroids or immunosuppressive drugs have not demonstrated effectiveness for patients with nephropathy who exhibit pathogenic variants in MAFB, except for a patient with nephropathy with FSGS and MCTO who experienced attenuated proteinuria within the subnephrotic range in response to cyclosporine A (CyA) treatment for at least 4 years. Thus, we attempted administration of CyA in our patient. Unexpectedly, the patient demonstrated good and rapid responses to CyA, including a partial reduction in proteinuria from approximately 2.0 g/g Cr to proteinuria within the subnephrotic range (0.27 g/g Cr) after 13 months of observation. Our findings suggest that CyA may be a suitable treatment option for patients with nephropathy with FSGS who exhibit pathogenic MAFB variants.

Electrocardiogram findings at the initiation of hemodialysis and types of subsequent cardiovascular events

The prognostic value of electrocardiograms (ECGs) has been reported in predialysis patients but not in incident hemodialysis patients with overhydration and electrolyte disturbances, both of which potentially affect ECG results. We performed a retrospective multicenter cohort study involving incident hemodialysis patients and examined whether ECG parameters immediately before hemodialysis initiation can predict subsequent cardiovascular disease (CVD) using Cox proportional hazards models. We explored potential effect modifications by several electrolytes on the predictive power of ECG abnormalities. Among the 618 enrolled patients, 16%, 10%, 46%, and 22% showed a PR interval ≥ 200 ms, QRS interval ≥120 ms, QTc interval ≥ 450/460 ms (male/female), and left ventricular hypertrophy (LVH) by voltage criteria, respectively. Over a median 3-year follow-up, 19% and 16% of the patients developed atherosclerotic and nonatherosclerotic CVD, respectively. The Cox regression model results revealed that the sum of the number of abnormalities in PR, QRS, and QT intervals was a significant risk factor for nonatherosclerotic CVD (hazard ratios (HRs) [95% confidence interval (CI)]: 1.58 [1.24-2.01] per number of abnormalities). The predictive value of LVH for atherosclerotic CVD was attenuated over time. At up to 36 months, although the proportional hazards assumption was met, LVH was significantly associated with atherosclerotic CVD (HR [95% CI]: 1.89 [1.15-3.11]). The adjusted HR was particularly high (HR [95% CI]: 4.02 [1.68-9.60]) among patients who were in the lowest tertile of serum magnesium levels (P for interaction = 0.04). PR, QRS, and QT prolongation additively predicted nonatherosclerotic CVD, while LVH predicted atherosclerotic CVD in the short term.

Modulation of the Association of Hypobicarbonatemia and Incident Kidney Failure With Replacement Therapy by Venous pH: A Cohort Study

RATIONALE & OBJECTIVE

Studies showing an association between lower bicarbonate levels and worse kidney disease prognosis have not accounted for the influence of pH. It remains unknown whether this association is consistent across a wide range of blood pH values. This study sought to assess how pH modifies the relationship between hypobicarbonatemia and incident kidney failure requiring kidney replacement therapy (KFRT).

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

1,058 Japanese patients with estimated glomerular filtration rates<60mL/min/1.73m².

EXPOSURE

Baseline venous bicarbonate levels and venous pH.

OUTCOME

KFRT defined as initiation of kidney replacement therapy (hemodialysis, peritoneal dialysis, and kidney transplantation).

ANALYTICAL APPROACH

Cox proportional hazards model assessing the interaction between baseline bicarbonate levels and venous pH on incident KFRT.

RESULTS

In the lowest bicarbonate quartile (≤21.5 mEq/L), 59% of patients had acidemia (pH<7.32), whereas 38% had venous pH within the normal range and 3% had alkalemia (pH>7.42). During a median follow-up of 3.0 years, 374 patients developed KFRT. Venous pH modified the association between bicarbonate level and rate of KFRT (P for interaction=0.04). After adjustment for potential confounders, including capacity for respiratory compensation, the lowest (vs the highest) bicarbonate quartile was associated with a 2.29-fold (95% CI, 1.10-4.77; P=0.03) higher rate of KFRT among patients with acidemia (pH<7.32). In contrast, among patients without acidemia (pH≥7.32), no significant association was found between bicarbonate level and KFRT. In an exploratory analysis, patients with higher respiratory compensation capacity had a lower rate of KFRT (HR per 0.1 increase in respiratory compensation capacity, 0.90; 95% CI, 0.87-0.94; P<0.001).

LIMITATIONS

Observational study design; blood gas measurements were performed in a select patient population.

CONCLUSIONS

Venous pH modified the association of hypobicarbonatemia with progression of chronic kidney disease to KFRT. Measurement of venous pH may be valuable for identifying patients with chronic kidney disease and hypobicarbonatemia and may inform treatment.

Lithocholic acid increases intestinal phosphate and calcium absorption in a vitamin D receptor dependent but transcellular pathway independent manner

Phosphate/calcium homeostasis is crucial for health maintenance. Lithocholic acid, a bile acid produced by intestinal bacteria, is an agonist of vitamin D receptor. However, its effects on phosphate/calcium homeostasis remain unclear. Here, we demonstrated that lithocholic acid increases intestinal phosphate/calcium absorption in an enterocyte vitamin D receptor-dependent manner. Lithocholic acid was found to increase serum phosphate/calcium levels and thus to exacerbate vascular calcification in animals with chronic kidney disease. Lithocholic acid did not affect levels of intestinal sodium-dependent phosphate transport protein 2b, Pi transporter-1, -2, or transient receptor potential vanilloid subfamily member 6. Everted gut sac analyses demonstrated that lithocholic acid increased phosphate/calcium absorption in a transcellular pathway-independent manner. Lithocholic acid suppressed intestinal mucosal claudin 3 and occludin in wild-type mice, but not in vitamin D receptor knockout mice. Everted gut sacs of claudin 3 knockout mice showed an increased permeability for phosphate, but not calcium. In patients with chronic kidney disease, serum 1,25(OH)₂ vitamin D levels are decreased, probably as an intrinsic adjustment to reduce phosphate/calcium burden. In contrast, serum and fecal lithocholic acid levels and fecal levels of bile acid 7α-dehydratase, a rate-limiting enzyme involved in lithocholic acid production, were not downregulated. The effects of lithocholic acid were eliminated by bile acid adsorptive resin in mice. Thus, lithocholic acid and claudin 3 may represent novel therapeutic targets for reducing phosphate burden.

New selectivity index calculated using protein fraction as a substitute for the conventional selectivity index

BACKGROUND

Selectivity index (SI) of proteinuria, calculated using the clearance ratio of immunoglobulin G to transferrin, predicts the response to glucocorticoids in patients with nephrotic syndrome. However, there is disagreement regarding the suitability of SI. Therefore, alternate indices should be considered. This study investigated whether or not selectivity index protein fraction (SIPF) was inferior to SI for the prediction of the response to glucocorticoids.

METHODS

Forty-nine patients with nephrotic syndrome were evaluated. On the basis of molecular weight and protein fraction, as an inexpensive substitute for SI, the clearance ratio of the albumin to γ fractions measured in serum and urine protein fractions was defined as SIPF. The quality of SIPF was examined. Moreover, the best cutoff value of SIPF was determined; and SIPF distribution, according to histopathological diagnosis by renal biopsy, was examined.

RESULTS

SIPF was strongly correlated with SI (r = 0.79, P < 0.001). The area under the receiver operating characteristic (ROC) curve of SIPF and SI was not significantly different (P = 0.18). The best cutoff value of SIPF was 0.45. In the group with SIPF > 0.45, only two patients with minimal change disease (MCD) achieved complete remission. In the group with SIPF ≤ 0.45, all patients with MCD achieved complete remission, although eight patients with other histopathological diagnoses did not achieve complete remission.

CONCLUSIONS

Analysis of protein fractions as a substitute for SI may be useful for predicting response to glucocorticoids in patients with nephrotic syndrome.

Anti-mitochondria antibody-related tubulointerstitial nephritis accompanied by severe hypokalemic paralysis

A 47-year-old man presented with severe hypokalemic paralysis and respiratory failure. A large amount of potassium was administered along with providing intensive care, and his condition improved. Hypokalemia was attributed to increased urinary potassium excretion. A kidney biopsy was performed to make a definitive histological diagnosis. It revealed acute tubulointerstitial nephritis (TIN). After the diagnosis, prednisolone was administered, and the TIN gradually improved. From the clinical course and laboratory findings, the TIN was presumed to be an autoimmune disorder. Further specific autoantibody tests were positive for anti-mitochondrial antibody (AMA), which has been gaining increasing attention in regard to TIN. In addition, all previous cases of TIN associated with AMA have affected females. The detailed pathogenetic mechanisms are as yet unclear and require further investigation.

Normal perfusion pressure hyperperfusion in cerebral arteriovenous malformation surgery: model study on the hemodynamics and mechanisms

A simulation study was undertaken using a compartmental flow model of a large high-flow cerebral arteriovenous malformation to investigate the hemodynamic changes during obliteration procedures. Under certain autoregulatory conditions, marked hyperperfusion (92 ml/100 g/min) could be induced in association with increased wall stress of the arterioles. Narrowing of the autoregulatory pressure range and its shift to a low pressure level are suspected to be among the possible causes of normal perfusion pressure breakthrough phenomenon.

Return to home early days after acute aortic dissection surgery

AIM

The length of hospital stay after acute aortic dissection surgery tends to be prolonged. The aim of this study is to assess the feasibility of our protocol for early discharge after acute aortic dissection surgery.

METHODS

This study enrolled 17 consecutive acute aortic dissection patients who returned to their own home within 2 weeks of surgery. In seven patients total aortic arch replacement was performed and in 7 partial arch replacement. The main aim of the first 24 h after surgery was to achieve early extubation. Patients were encouraged to return to their own home 4 days and later after surgery. The prerequisite criteria for discharge were the following: independent mobility, stable hemodynamics, apyrexia, adequate oral intake, normal bowel function, healthy surgical wound and the patient's agreement for discharge.

RESULTS

The mean age of these patients was 59. The postoperative ventilation time, length of intensive care unit stay and postoperative hospital stay were 11 h, 37 h and 6.9 days, respectively. Two (12%), 13 (76%) and 14 (82%) patients returned to their own home by postoperative day 4, 7 and 10, respectively. Three patients were readmitted to a peripheral hospital in the 4 week postoperative period. The reason for all readmissions was lack of family support. Two other patients underwent pericardiocentesis for pericardial effusion at an other hospital as outpatients. There was no complication caused by early discharge.

CONCLUSIONS

Early discharge after aortic dissection surgery is safe and recommended to patients who have normal bowel function and adequate family support.

Effects of ebselen on cerebral ischemia and reperfusion evaluated by microdialysis

Since ebselen is known to have glutathione peroxidase-like activity and inhibitory effects on lipoxygenase and cyclo-oxygenase, we investigated its protective effects against cerebral ischemia in the rat using microdialysis. Ebselen was given through a gastric tube 30 min before occlusion in the experimental groups. Ischemia was induced using 4-vessel occlusion either transiently (20-min occlusion of the arteries followed by reperfusion), or over a prolonged period (120-min occlusion). Extracellular lactate, pyruvate and purine catabolites were sampled using microdialysis and measured by high performance liquid chromatography. During ischemia, the level of lactate, adenosine, inosine and hypoxanthine in the control group increased markedly. The lactate: pyruvate ratio increased during ischemia and decreased after reperfusion. Although the level of lactate and adenosine decreased immediately after reperfusion, those of inosine and hypoxanthine showed delayed decrease. Ebselen reduced the maximum values of lactate and purine catabolites significantly and markedly in transient ischemia. Although it reduced the values significantly in prolonged ischemia, the decrements were less marked than those in transient ischemia. Based on these results we consider ebselen to protect against ischemic metabolic changes and to accelerate the recovery during reperfusion.

[Hemodynamic simulation study of cerebral arteriovenous malformations: changes of wall stress and early detection of NPPB]

Obliteration procedures for large high-flow arteriovenous malformations (AVM) were simulated using a compartmental flow model to investigate the role of altered autoregulatory conditions in the development of hyperperfusion and normal perfusion pressure breakthrough (NPPB). Since the arterioles are primarily responsible for autoregulatory function, the role of these structural changes on the development of hyperperfusion was also studied by evaluating the wall thickness (T), internal radius (Ri) and tangential wall stress (sigma). As the AVM flow was decreased during the obliteration procedures, the perfusion pressure (delta P) of the brain tissue surrounding the AVM increased. When the autoregulatory condition was impaired [AR (-)] and the lower limit of the autoregulatory pressure range (LAR) was shifted from 60 mmHg (LAR60) to 40 mm Hg (LAR40), the flow volume in the surrounding brain (Fb) increased markedly, from 67 ml/100g/min to 92 ml/100g/min, with the progress of the obliteration procedures. In these conditions, T/Ri was supposed to be constant and sigma value increased uniformly. In the presence of the autoregulatory mechanism [AR (+)], T/Ri increased against increasing delta P, which resulted in smaller sigma value than that under AR (-) conditions. When the contracted vascular wall yielded on the process of increasing wall stress, delta P and feeder pressure (Pf) decreased to some degree. Concomitantly increase of the sigma value and marked hyperperfusion developed in the brain. The yield of the contracted vascular wall would result in the decrease of a pressure gradient across the arteriole and the reciprocal increase of pressure load on the walls of the capillary and venula, which might lead to NPPB. Since the decrease of delta P or Pf during the progress of the obliterating procedures is considered specific to the appearance of hyperperfusion or NPPB, monitoring these parameters would be useful for its early detection. If the upper limit of the autoregulatory pressure range was assumed to decrease and become the yield point in the brain surrounding high flow AVMs, hyperfusion or NPPB could be considered to develop in the conditions with the autoregulatory pressure range being narrowed and/or shifted to the lower pressure level. Induced systemic hypotension was found to be effective in reducing the magnitude of Fb, delta P, and Pf when induction was appropriately performed in stepwise fashion. T/Ri and sigma were kept in narrow ranges compared to those before induction of hypotension.

Hemodynamic simulation study of cerebral arteriovenous malformations. Part 2. Effects of impaired autoregulation and induced hypotension

The hemodynamic changes occurring during obliteration procedures for arteriovenous malformations (AVM) have not been fully elucidated. Therefore, we undertook a simulation study using a compartmental flow model to investigate the role of altered autoregulatory conditions in the development of hyperperfusion during obliteration of large high-flow AVM. Induced hypotension was also simulated to evaluate its usefulness in reducing the incidence and severity of the event. As the AVM flow was decreased during the obliteration procedures, feeder pressure increased and drainer pressure decreased, with a concomitant increase in the perfusion pressure in the brain tissue surrounding the AVM. Cerebral blood flow (CBF) remained constant at 50 ml 100 g-1 min-1 in the presence of autoregulation and increased to 67 ml 100 g-1 min-1 in its absence. When the lower limit of the autoregulatory pressure range (LAR) was shifted from 60 to 50 or 40 mm Hg, the flow volume increased markedly from 67 to 77 ml 100 g-1 min-1 or to 92 ml 100 g-1 min-1 after complete obliteration. Decrease in LAR would be a cause of the hyperperfusion. Induced systemic hypotension was found to be effective in reducing the magnitude of these hemodynamic changes, when induction was appropriately performed in a stepwise fashion. A simulation study is useful in clarifying the various hemodynamic changes that develop during the treatment of AVM.

Dissociated changes of frontal and parietal somatosensory evoked potentials in sleep

We studied the changes of frontal and parietal somatosensory evoked potentials (SEPs) in the awake state versus different stages of sleep in 10 normal adult subjects. Frontal and parietal SEP components were affected differentially as sleep stages progressed. In general, the amplitudes of frontal components, notably P22, were increased in sleep, whereas the amplitudes of parietal components were decreased in sleep. A sensitive waveform change from the awake state to sleep was present in the frontal response, where a subtle notched negativity, termed "N40," was present only in the awake state and quickly dissipated in all stages of sleep, including stage 1. The amplitude changes from the awake state to stage 3/4 sleep were neither linear nor parallel among SEP components. The most discordant changes occurred in stage 3/4. The amplitudes for the frontal N18-P22-N30 complex and parietal N20-P26-N32 complex increased from stage 2 to stage 3/4, while those for frontal N30-fP40 and parietal N32-pP40 decreased. In contrast to these divergent amplitude changes, the latencies of all components except P14 and frontal N18 showed progressive prolongation from the awake state to slow-wave sleep. The SEP waveforms and latencies in REM sleep approximated those in the awake state, although amplitudes for frontal peaks still remained slightly higher and amplitudes for parietal peaks slightly lower. We postulate that interactions of excitatory and inhibitory phenomena are responsible for the component-dependent and sleep-stage-dependent amplitude enhancement or depression in sleep.

High-rate sequential sampling of auditory brain-stem and somatosensory evoked responses in hypoxia

We developed a high-rate sequential recording technique that allowed simultaneous measurements of both auditory brain-stem response (ABR) and somatosensory evoked potential (SEP) every 10 sec. Using this method, a transient increase in amplitude of all the ABR and SEP components in response to hypoxia in dogs could be detected. The increase in amplitude preceded the prolongation of latency. Our study showed that there were successive changes of evoked potentials in response to hypoxia. A transient increase in amplitude is the first to occur, followed by a latency prolongation and an amplitude decrease for both ABRs and SEPs.

[EC-IC bypass surgery using saphenous vein graft: technical improvement in our experience]

We managed ten cases of EC-IC bypass using a vein graft; six cases with multiple cerebral arterial occlusion and four cases with aneurysm necessitating therapeutic occlusion of the parent artery (Table). Patency of the graft was confirmed in seven cases on long-term follow-up ranging from 7 months to 5 years. Of the ten cases, two died within 7 days after surgery from causes unrelated to the bypass and one was lost in follow-up surgery. Hemorrhagic infarction was observed in two cases, one of which underwent removal of the hematoma. In five cases with cerebral occlusive disease, there were no additional ischemic events and two cases with giant aneurysms showed improvement of visual acuity and extraocular movement. We improved on several surgical techniques for vein graft. We used small hemoclips to occlude branches of the saphenous vein instead of ligating them, which shortens the harvesting time of the saphenous vein. Vessel cannula with a small-sized elegant tip and one-directional valve (DLP, INC., USA) was also used to inflate or deflate vein grafts with saline. It was easily attached to the graft and minimized air entrapment in the lumen. Small clips for microvascular anastomosis (Mizuho INC., Japan) were used to temporarily occlude branches or perforators from the recipient artery. One of the branches of the graft was dissected long enough, through which intraluminal air or thrombus was washed out at the final stage of the surgery. These procedures are useful for shortening occlusion time of the recipient artery and decreasing the risk of embolism.

Simulation study on therapeutic vertebral artery occlusion for VA-PICA giant aneurysm

We investigated haemodynamic effects of therapeutic vertebral artery (VA) occlusion on giant aneurysms at the bifurcation of the VA-posterior inferior cerebellar artery (PICA). An hydraulic model of the human vertebro-basilar artery was manufactured from glass and silicone tubes. Glass-spheres 2.5 cm in diameter were placed at the bifurcation as model aneurysms with respective distances of 8.5, 7.5, 6.5 and 5.5 mm between the VA union and aneurysmal neck. A 40% glycerol solution was perfused in this system and the half-life of the dye injected into aneurysms was regarded as an index of intra-aneurysmal stagnation. Flow conditions in aneurysms depended on the presence or absence of the effect of contralateral VA flow as well as the PICA flow. The half-life increased significantly after VA occlusion proximal to the PICA when the aneurysmal neck was more than 7.5 mm away from the VA union and PICA flow volume was less than 12 ml min-1. The half-life in aneurysms located within 6.5 mm from the union changed little after VA occlusion regardless of the PICA flow volumes. The haemodynamic simulation study would be helpful in speculating on the efficacy of this treatment.