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Biomedical subjects

F A Gotch

Publications and source records attributed to F A Gotch.

At least 37 records · Page 2Linked to original sources
PubMed1996

Computerized urea kinetic modeling to prescribe and monitor delivered Kt/V (pKt/V, dKt/V) in peritoneal dialysis. Fresenius Randomized Dialysis Prescriptions and Clinical Outcome Study (RDP/CO).

A computerized urea kinetic model of peritoneal urea transport (PACK-PD) has been developed and used to calculate prescription parameters which would result in the prescribed weekly peritoneal urea clearance (pKpt/V) required to achieve levels of weekly summed renal + peritoneal urea clearance (pKprt/ V) targeted at 1.75 and 2.16. Baseline kinetic data were obtained and analyzed with PACK-PD on 88 patients, and the program then used these data to calculate the required pKpt/V and subsequently the delivered Kpt/V (dKpt/V) from the dialysate collections. A total of 108 prescriptions were written and compared to dKpt/V measured over one to 24 months in the 88 patients. Both continuous ambulatory peritoneal dialysis and automated peritoneal dialysis (APD) were studied (APD consisted of PD+ with one or two diurnal and two to four nocturnal cycler exchanges). The correlation of dKpt/V to pKpt/V showed r = 0.93 with 95% confidence limits (CL) on agreement of +/-20% over a range of pKpt/V 0.52-2.55. The 95% CL on (dKpt/V-pKpt/V) were +/-0.30. We concluded: (1) that the prescription can be modeled as reliably in peritoneal dialysis as in hemodialysis (HD) where dKt/V and pKt/V agree to +/-25%, (2) that any individual weekly dKpt/V may vary as much as 0.3-0.4 from pKpt/V, and (3) that frequent measurement of dKpt/V and adjustment of pKpt/V as needed are required (as in HD) to control mean dKpt/V to within +/-10% of mean pKpt/V.

Capillary Permeability↗
PubMed1993

Adequacy of peritoneal dialysis.

The combined annual mortality and drop out rate for peritoneal dialysis (PD) patients is relatively uniform worldwide at approximately 35%. The level of PD therapy prescribed in clinical practice is largely empirical and typically consists of four 2-L exchanges daily. It might be speculated that the 35% annual attrition rate in PD may in part reflect under dialysis in some patients due to empirical rather than quantitative and individualized prescription of PD therapy. Urea kinetic modeling has been successfully used to quantitatively prescribe hemodialysis (HD) therapy and, in principle, it should be able to serve the same purpose in PD. Comparison of HD and PD is complicated, because peritoneal urea clearance is virtually continuous, while in HD clearance is provided only about 5% of the time and urea accumulates over 95% of each treatment cycle. The blood urea nitrogen (BUN) in PD (BUNpd) is essentially constant and reflects the steady state, while in HD a sawtooth BUN profile results that reflects the short intermittent dialyses. The HD BUN profile can be characterized by either the predialysis level (BUNo) or the time-averaged concentration (TAC) over each treatment cycle. TAC is substantially lower than BUNo due to the sharp obligatory decrease in BUN during each short high-clearance dialysis. The rate of clearance required in HD is approximately 30 times higher than in PD, and the total clearance (KT) required in HD is 50% higher than in PD to achieve BUNpd = BUNo (at identical normalized protein catabolic rate [NPCR]), which reflects the decreasing urea flux rate during HD due to the decreasing BUN.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Urea Nitrogen↗
PubMed1992

A pharmacodynamic model of erythropoietin therapy for uremic anemia.

Fifty-seven patients receiving chronic high-flux hemodialysis began receiving recombinant alpha-human erythropoietin (rHuEPO). The mean initial rHuEPO dose used in 54 evaluable patients was 9963 +/- 4364 U/week; the final dose was 8972 +/- 4058 U/week. Treatment over a mean period of 154 +/- 40 days (84 to 224 days) resulted in an average increase in hematocrit from 24.7% +/- 3.7% to 32.5% +/- 4.4%. We present a model for these data that describes changes in hematocrit during rHuEPO therapy and that allows simultaneous estimation of red blood cell lifespan and rHuEPO-induced increases in red blood cell production rate. Analysis of the hematocrit values of the patients with the model, by use of NONMEM, a computer program for analysis of population data, reveals a nonlinear dose-response relationship with large interindividual variability (coefficient of variation) of about 50%. The estimated mean red blood cell lifespan is 64 days, with interindividual variability of about 30% (coefficient of variation). The intraindividual random variability in hematocrit about its prediction is +/- 5% of the prediction. For clinical dose adjustment, we present a method that uses only simple calculations.

Anemia↗
PubMed1990

A kinetic survey of US hemodialysis prescriptions.

Recent reports indicate increasing mortality correlated to reduced treatment time (t) in hemodialysis (HD) patients. HD prescriptions for 101 patients visiting our unit were subjected to kinetic analysis to assess the amount of dialysis prescribed (Kt/V) and its relationship to t. The analysis showed (1) 98% of the prescriptions were empirical; (2) Kt/V was strongly correlated to protein intake (normalized protein catabolic rate [NPCR], g/kg/d), r = 0.50, N = 101; (3) Kt/V was strongly correlated to t, y = 0.50 + 0.54x, r = 0.54, and fell below 1 when t less than or equal to 3.5 hours; (4) a prescription flux deficit appeared and increased exponentially as t fell below 3.7 hours. These results suggest that in clinical practice, t is individualized as a function of predialysis BUN and is reduced when BUN is low due to low NPCR because of a perceived need for less dialysis. Because of this practice, reduced t is often associated with inadequate dialysis, and kinetic modeling of the interrelationship between blood urea nitrogen (BUN), NPCR, and Kt/V is required to assure adequate dialysis with reduced t.

Blood Urea Nitrogen↗
PubMed1985

A mechanistic analysis of the National Cooperative Dialysis Study (NCDS).

The purpose of the NCDS was to determine the probability of clinical failure (PF) as a function of the level of dialysis and protein catabolic rate (pcr, g/kg/day). The level of dialysis prescribed in the NCDS was mechanistically defined as Kt/V (product of dialyzer urea clearance and treatment time divided by body urea volume), which exponentially determines decrease in BUN during dialysis and is also a mathematical analogue of pcr, BUN. Mechanistic analysis (MA) showed that PF was a discontinuous function of Kt/V as it was prescribed in the NCDS and that a dependence of PF on pcr could not be assessed because of the study design. The MA results were compared to those reported with statistical analysis (SA) that used BUN and pcr. The SA predicts PF is strongly dependent on pcr with nutrition-dependent high PF for pcr less than or equal to 0.8 and low PF with high pcr and intensive dialysis. The MA suggests SA results may not be valid because a continuous outcome function is assumed and, due to study design, Kt/V was a dependent variable of pcr and these two variables cannot be clearly separated by analysis of BUN and pcr alone.

Blood Urea Nitrogen↗
PubMed1984

Serum sodium concentration and body fluid distribution during interdialysis: importance of sodium to fluid intake ratio in hemodialysis patients.

Changes in the serum Na+ concentration and transcellular body fluid distribution during the interdialytic period were simulated as functions of body weight gain assuming that the effective extracellular osmolality consists only of sodium. Our model shows that these changes are mainly determined by the relative ratio between sodium intake and weight gain in this period. If the sodium intake-to-net fluid intake ratio is equal to the postdialytic serum [Na+], neither changes in serum [Na+] nor transcellular fluid shifts occur. When sodium intake is relatively greater than the net water intake, serum [Na+] is increased and transcellular fluid shifts will occur out of the cells. On the other hand, when the net water intake is relatively greater than the sodium intake, serum [Na+] is decreased and fluid is distributed to both the intracellular and extracellular compartments. The combined application of our models for both the intradialytic interval described previously and the interdialytic interval described here is very useful in quantitatively analyzing the overall sodium and water metabolism in dialyzed patients.

Body Fluids↗
PubMed1982

Hydrogen ion balance in dialysis therapy.

A model to describe hydrogen ion balance (H+B) in acetate and bicarbonate dialysis therapy was developed based on measurement of metabolic addition of hydrogen ion (H+) to the body between and during dialyses and measurement of net buffer repletion during dialysis. Metabolic H+ generation was shown to be equal to 0.77 times the protein catabolic rate plus the total net removal of lactate and beta-hydroxybutyrate ions during dialysis. Buffer repletion was calculated from total net flux of acetate and bicarbonate during dialysis. The model was used for eight paired studies of H+B on one week each of acetate and bicarbonate dialysis and showed that cumulative H+B with acetate was -7 +/- 28 (M +/- SEM) mmol/week compared to -175 +/- 45 mmol/week with bicarbonate (P less than 0.001). It is concluded that there is an initial, strongly negative H+B when patients on acetate dialysis are converted to bicarbonate. The possible physiologic significance of this is discussed.

Acetates↗