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Biomedical subjects

M A Baltzan

Publications and source records attributed to M A Baltzan.

At least 19 recordsLinked to original sources
PubMed2000

Accuracy of oximetry with thermistor (OxiFlow) for diagnosis of obstructive sleep apnea and hypopnea.

OBJECTIVES: To evaluate the diagnostic accuracy for obstructive sleep apnea and hypopnea (OSAH) of the OxiFlow (OF) device which combines oximetry with recording of thermistor airflow. DESIGN & SETTING: Patients scheduled for overnight diagnostic polysomnography (PSG) were studied with OF either simultaneously during laboratory PSG (L-OF, n=86), at home on a separate night (H-OF, n=66), or both (n=55). PATIENTS: 97 patients with suspected OSAH, of whom 40 had OSAH defined as an apnea-hypopnea index (AHI) of more than 15 events per hour of sleep on PSG. INTERVENTIONS: NA. MEASUREMENTS & RESULTS: The automated respiratory disturbance index (RDI) generated by the OF software considerably underestimated the AHI by PSG for both L-OF and H-OF. Altering the parameters for hypopnea identification by the software did not improve this. Visual inspection of the computerized OF tracings added considerable diagnostic information, but a manual count of RDI during visual review overestimated AHI. For the identification of cases vs. non-cases of OSAH, receiver operating characteristic area-under-the-curve statistics ranged from 0.77-0.90 for L-OF and from 0.71-0.77 for H-OF. Combining automated analysis with subsequent visual inspection of OF tracings yielded an overall sensitivity of 86% and specificity of 74% for the diagnosis of OSAH during H-OF recordings. Analysis of potential technician time saved indicated a benefit from the use of OF. CONCLUSIONS: OF has diagnostic utility for the identification of OSAH. However, because of hardware and software limitations, it is unclear whether this device is superior to oximetry alone.

Adult↗
PubMed1997

Alloantigen-blocking antibodies in sera from highly sensitized uremic patients: antibody class and relationship with lymphocytotoxins.

BACKGROUND: Previously, we identified an antimitogenic IgG antibody separated from sera of patients with known kidney transplant chronic rejection. This antibody inhibits individual patients' own unprimed T helper cell responses to alloantigens as well as a third-party mixed lymphocyte response, but does not inhibit autologous unprimed T helper cell proliferation to adherent anti-CD3 antibody. We suggest that the mechanism of inhibitory action is allogeneic-dependent. METHODS: We used a series of similar experimental designs to test the presence of this antibody in uremic, sensitized patients and have studied its relationship to sensitization as defined by the presence of lymphocytotoxins in four uremic groups: highly sensitized with or without previous graft loss, moderately sensitized with or without graft loss, nonsensitized without previous graft loss, and nonsensitized with graft loss. RESULTS: (1) Sensitization is associated with the presence of a potent antibody that blocks primary mixed lymphocyte response. Primed cells are less susceptible to its antimitogenic action. (2) The blocking antibody activity is present only in sensitized patients who have IgG lymphocytotoxic activity against the same HLA class I antigens. (3) The blocking activity is unequal in the following order: IgG 3 > IgG 1 > IgG 2. (4) Although IgG 1 and 2 fractions contain lymphocytotoxic activity against HLA class I antigens, the IgG 3 fraction does not. CONCLUSIONS: The differential effect of IgG antibodies on naive and memory T cells may explain why humeral responses to alloantigens can be maintained in the presence of blocking antibodies.

Antibody Formation↗
PubMed1997

Protein malnutrition and decreased protein turnover in chronic renal allograft failure.

OBJECT: To define the longitudinal relationship of declining renal function to protein consumption and turnover in the failing renal allograft model of chronic renal failure. METHOD: The study group is our first eight consecutive cadaveric renal graft recipients who after attaining a normal creatinine clearance, then developed chronic renal failure. We analysed their urea and creatinine clearances (Cur, Ccr), serum urea (SU), urinary urea and creatinine (Ur, Ucr), serum albumin (SA), urinary protein (Upr), body weight (BW), and steroid dose. Steady state Uur is also dietary protein intake (DPI) and protein catabolic rate (PCR). Ucr measures body protein mass. Ucr/Uur measures the ratio of body protein mass to urea excretion. Mean follow-up 4.7 years, range 1.5-8.7 years. RESULTS: Mean changes: (1) Body weight (BW) rose from 56 to 65 and then fell to 61 kgms. (2) Cur fell 65 to 5 and Ccr 92 to 12 ml/min/70 kg. (3) Uur fell from 369 to 107 and Ucr from 16.8 to 9.5 mmols/day/70 kg. (4) Uur/Ucr indexed at 1:1 fell to 0.49. (5) SU rose from 8.8 to 34.9 mmol/1; SA fell from 36.1 to 31.0 gms/1; Upr rose from 1.4 to 2.3 gms/day. (6) Prednisone rose from 26 to 66 and then fell to 33 mgms/day. Correlations: (1) Cur and Uur(r = 0.99, p < 0.001). (2) Ccr and Uur (r = 0.99, p < 0.001). (3) Cur and Uur/Ucr (r = 0.88, p < 0.01) with a decelerating breakpoint at Cur 18 and Ccr 32 ml/min/70 kg (p < 0.01). (4) SU and Uur negatively (r = 0.90, p < 0.01. (5) Cur and SA albumin (r = 0.82, p < 0.05). (6) Cur and prednisone, Upr and SA do not correlate. CONCLUSIONS: In this model of chronic renal failure: (1) Renal function controls protein intake. (2) Body protein mass is relatively well preserved despite the decreased protein intake implying a decrease in the protein turnover rate and a consequent increase in body protein average age. (3) Protein malnutrition, protein ageing, and decreased protein turnover are likely pathophysiological reactions to chronic renal failure and may be part of the pathogenesis of chronic uremia.

Adult↗
PubMed1997

Variations in living donor graft rates by dialysis clinic: effect on outcome and cost of chronic renal failure therapy.

OBJECT: Examination of nephrology practice variations in living donor renal grafts to determine their influence on organ supply, quality, and cost of chronic renal failure therapy. MATERIALS: Saskatchewan chronic dialysis, cadaveric, and living donor renal grafts in 1983-1994 inclusive. RESULTS: Saskatchewan has three dialysis (I, II, III) and one transplant clinic. In the period the renal graft incidences/million population by these dialysis clinics by organ source were; Cadaveric: 23.1, 23.2, 21.1 (p = ns). Living: 5.4, 21.7, 8.3 (I or III vs II p < 0.000, I vs III p < 0.061). Total: 28.7, 44.7, 29.4. Living donor series A is 79 grafts in patients under age 60 with primary renal disease. Series B is 20 grafts in patients with secondary renal disease or over age 59. Series A ten-year actuarial patient survival is 92% and B 44%. Series A ten-year actuarial graft survival (including regrafts) is 77% and B 39%. Rehabilitation rate in patients with functioning grafts is 88.5%. Province-wide extension of the Clinic II living-donor graft rate in 1983-1994 would have produced 160 more renal grafts or 59% of those receiving chronic dialysis in 1994. The annual maintenance for a graft with the initial grafting cost taken over five years was $10,825 and the dialysis cost $40,100. CONCLUSIONS: (1) nephrology practice variations caused a 2.5-4.0-fold difference in living donor renal graft rates, indicating patient education by the attending nephrologist influences the living donor transplantation rate, (2) with such education the combined living donor and the cadaveric organ supply virtually meets graft demand, (3) living donor renal grafts yield a better quantity and quality of life and better cost control than dialysis with their annual cost being one-quarter that for dialysis.

Actuarial Analysis↗
PubMed1996

HLA-identity--long-term renal graft survival, acute vascular, chronic vascular, and acute interstitial rejection.

The object is analysis of the impact of acute and chronic rejection on long-term function in HLA-identical renal transplants performed from 1967 to 1995 by the Saskatchewan Renal Transplant Unit. Forty-eight grafts in 46 patients were studied, of which 39 were first and nine second grafts. Forty-two were for primary and six for secondary renal disease. Thirty-five received azathioprine/prednisone prophylaxis, and 13 received cyclosporine/prednisone with/without azathioprine. Ten-year all graft actuarial survival was 84%, 10-year actuarial graft survival in patients with primary renal disease 90%, and with subsequent graft after first HLA graft failed 97.5%, for age-matched population 98.5% (P=NS). Overall death rate was 8.7% (4/46); in secondary renal disease patients 50% (3/6); in primary renal disease patients 2.5% (1/40, P=0.004). All (9/9) HLA-identical second grafts functioned. Acute rejection with azathioprine/prednisone prophylaxis occurred in 55% (9/17) of grafts treated with <6 pre-graft blood transfusions, with the same prophylaxis but >5 units in 12% (2/16, P=0.015), and with cyclosporine prophylaxis in 13% (2/15, P=0.021). Pulse steroids alone reversed all acute rejection. Grafts failed in 6.2% (3/48), all in primary renal disease patients and one from technical one noncompliance, and one chronic rejection. Graft cost/patient/year amortized over 9 years is $3,855 and comparable dialysis cost would be $35,650; cost for all patients on dialysis for 9 years would be $11,293,320 while comparable graft cost was 1,221,418, a savings of 89.2%. Our conclusions are that HLA-identity associates with the following: (1) a 10-year actuarial survival in primary renal disease that equals that of the age-matched population, (2) uniform success in repeat grafts, (3) virtual absence of chronic rejection despite a high incidence of acute rejection in azathioprine/prednisone grafts that (4) always reversed on pulse steroids, and (5) a cost reduction for grafting of 93.2% compared with dialysis therapy.

Acute Disease↗
PubMed1996

Improved urea clearance raises the BUN in continuous peritoneal dialysis.

Cross-sectional studies in steady state dialysed chronic end-stage renal failure patients show urea clearance (Kt/V) and total urea excretion (protein catabolic rate) correlate positively. However, urea clearance is total urea excretion divided by BUN. Thus urea clearance and BUN relate reciprocally, and so their mathematical product (total urea excretion) is independent of clearance. As such clearance cannot also be a positive correlate of total excretion as demanded by the cross-sectional studies. Furthermore the clearance formula dictates that the positive urea clearance and total urea excretion correlation found in the cross-sectional studies can only occur if the increased urea clearance fails to reciprocally lower the BUN. Thus the relations of urea clearance, urea excretion, and BUN requires further definition. To so define we examine dialysis urea excretion, dialysis urea clearance, BUN, and serum albumin in 13 stabilized chronic uremics with minimal native renal function who are treated by continuous ambulatory peritoneal dialysis (CAPD). Urea clearance and BUN correlate positively (r = 0.62, p < 0.05) and both also correlate positively with dialytic urea excretion and (urea clearance r = 0.912, p < 0.001, BUN r = 0.88, p < 0.001). In addition dialytic urea excretion and serum albumin indexed to body size correlate positively (p < 0.05). Thus in the steady state urea clearance associates with both an increase in BUN and urea output. However the law of conservation of mass makes urea output is a function of protein intake. Thus increased clearance cannot directly increase such output, and so increased clearance must first increase intake but in doing so it increases the retention of the byproducts of enhanced intake, BUN and other protein metabolites, so leading to a paradox, the more removed, the more remains. These observations taken together suggest that in chronic uremia treated by continuous dialysis, elevation of the BUN may be a marker for an adequate restoration of protein metabolism if inadequate dialysis is excluded.

Adult↗