Biomedical subjects

George Kaysen

Publications and source records attributed to George Kaysen.

5 recordsLinked to original sources

PubMed2004

Age-related decline in serum parathyroid hormone in maintenance hemodialysis patients is independent of inflammation and dietary nutrient intake.

BACKGROUND: There is a direct relationship between age and serum parathyroid hormone (iPTH) in the normal population, but several studies suggest this relationship is reversed in maintenance hemodialysis (MHD) patients. The pathophysiologic basis of this age-related decline in serum iPTH levels remains unclear, although others have proposed that it is related to low dietary phosphorus intakes. METHODS: We conducted a prospective, cross-sectional evaluation of the relationship between age and serum iPTH levels and factors affecting this relationship. All participating subjects were asked to complete a 3-day food diary. The charts were reviewed to obtain routinely measured laboratory values over the preceding 3 months, and serum was collected to measure markers of systemic inflammation. RESULTS: Ninety-two MHD patients (47 men; age, 51.3+/-14.9 [standard deviation] years; median dialysis vintage, 25.8 months) were studied. Age was inversely correlated with both serum phosphorus and iPTH; these relationships remained significant even when the data were adjusted for diabetic status, dialysis vintage, and dietary nutrient intake. However, there were no associations of age, serum phosphorus, or iPTH with dietary intakes of protein, calories, phosphorus, or calcium either on univariate or multivariate analyses. Markers of systemic inflammation (serum C-reactive protein, and alpha1 acid glycoprotein) did not correlate with age, serum phosphorus, and iPTH or dietary nutrient intake. On the other hand, serum albumin, which may reflect long-term effects of inflammation, did correlate inversely with age and positively with serum phosphorus. CONCLUSIONS: Our cross-sectional study confirms that there are age-related lower levels of both serum phosphorus and iPTH in MHD patients. The mechanisms regarding the inverse relationship between serum phosphorus and age are unclear, but may not be caused by low phosphorus intake or systemic inflammation. In elderly MHD patients, the reduced responsiveness of parathyroid glands may be related to age-dependent accumulation of uremic toxins.

Adult↗

PubMed2003

Measurement of intraperitoneal volume by segmental bioimpedance analysis during peritoneal dialysis.

BACKGROUND: Currently, ultrafiltration during peritoneal dialysis is determined from direct measurement of weight differences between the initial filling and final draining volumes. A new technique based on segmental bioimpedance analysis (SBIA) has been developed to accurately measure intraperitoneal volume continuously during peritoneal dialysis. METHODS: Twenty-two peritoneal dialysis patients were studied in a supine position during peritoneal dialysis consisting of 4 tidal exchanges (TPD). For bioimpedance measurements, 4 electrodes were placed, 1 on each hand and foot, to inject an alternating current. Sensing electrodes were placed on the lower ribs and the buttocks on both sides of the body. Calibration of the SBIA method was performed by first filling a known volume of dialysate to establish the relationship between change in resistance and a known fluid volume in the peritoneal cavity. The increase of fluid volume in the peritoneal cavity during dwell time was considered to be equal to net ultrafiltration volume occurring during this period. These measurements were compared with those obtained by the difference in weight between the total filling and draining volumes. RESULTS: The change in intraperitoneal volumes measured by differences in weight (0.39 +/- 0.29 L) did not differ significantly from those established from SBIA (0.41 +/- 0.31 L). Bland-Altman analysis yielded limits of agreement of 0.12 L. CONCLUSION: The SBIA technique provides a continuous noninvasive approach to the measurement of changes in intraperitoneal fluid volume.

Adult↗

PubMed2003

A kinetic model of inorganic phosphorus mass balance in hemodialysis therapy.

BACKGROUND: There is growing evidence that inorganic phosphorus (iP) accumulation in tissues (dTiP/dt) is a risk factor for cardiac death in hemodialysis therapy (HD). The factors controlling iP mass balance in HD are dietary intake (GiP), removal by binders (JbiP) and removal by dialysis (JdiP). If iP accumulation is to be minimized, it will be necessary to regularly monitor and optimize GiP, JbiP and JdiP in individual patients. We have developed a kinetic model (iPKM) designed to monitor these three parameters of iP mass balance in individual patients and report here preliminary evaluation of the model in 23 HD patients. METHODS: GiP was calculated from PCR measured with urea kinetics; JdiP was calculated from the product of dialyzer plasma water clearance (K(pwiP)) and time average plasma iP concentration (TACiP) and treatment time (t); a new iP concentration parameter (nTAC(iP), the TACiP normalized to predialysis CoiP) was devised and shown to be a highly predictable function of the form nTAC(iP) = 1 - alpha(1 - exp[-betaK(pwiP). t/ViP]), where the coefficients alpha and beta are calculated for each patient from 2 measure values for nTAC(iP), K(pwiP).t/ViP early and late in dialysis; we measured 8-10 serial values for nTAC(iP), K(pwiP). t/ViP over a single dialysis in 23 patients; the expression derived for iP mass balance is DeltaTiP = 12(PCR) - [K(pwiP)(t) (N/7)][CoiP(1 - alpha(1 - exp[-beta(Kt/ViP)]))] - k(b).Nb. RESULTS: Calculated nTAC(iP) = 1.01(measured nTAC(iP)), r = 0.98, n = 213; calculated JdiP = 0.66(measured total dialysate iP) + 358, n = 23, r = 0.88, p < 0.001. Evaluation of 10 daily HD patients (DD) and 13 3 times weekly patients with the model predicted the number of binders required very well and showed that the much higher binder requirement observed in these DD patients was due to much higher NPCR (1.3 vs. 0.96). CONCLUSION: These results are very encouraging that it may be possible to monitor the individual effects of diet, dialysis and binders in HD and thus optimize these parameters of iP mass balance and reduce phosphate accumulation in tissues.

Death↗

PubMed2002

Heat accumulation with relative blood volume decrease.

BACKGROUND: Both hypovolemia and heat accumulation act as powerful perturbations of blood pressure control. In hemodialysis, hypovolemia and heat accumulation often develop simultaneously, and the question arises of whether and to what extent these perturbations are linked. METHODS: Heat accumulation was measured by the amount of thermal energy (E) removed from a patient during prescribed ultrafiltration under isothermic hemodialysis conditions, ie, constant patient temperature. Measurement and control of temperatures and thermal energies were performed using the blood temperature monitor. Relative blood volume (RBV) was measured using the blood volume monitor. RESULTS: Thirty-eight treatments were analyzed in 12 patients (3 women). During treatments lasting 189 +/- 28 minutes, 5.1% +/- 1.3% of postdialysis body weight were removed from patients by ultrafiltration at a mean rate of 1.1 +/- 0.3 L/h. Blood volumes decreased to 85% +/- 7% of initial values, and 229 +/- 106 kJ of E were removed from patients at a cooling rate (J) of 20 +/- 8 W, corresponding to 28% +/- 11% of estimated energy expenditure (H%). E, J, and H% significantly increased as RBV decreased (P < 0.05). Linear regression analysis between J and RBV showed that approximately 1 W had to be removed from the patient for each percentage of change in blood volume (J = -102.38 + 0.97* RBV; r2 = 0.63). CONCLUSION: Results show that the probability for the effect of heat stress during hemodialysis increases with ultrafiltration-induced blood volume changes. Temperature control is an important aspect of hemodialysis treatment.

Adaptation, Physiological↗

PubMedDate not supplied

Effective diffusion volume flow rates (Qe) for urea, creatinine, and inorganic phosphorous (Qeu, Qecr, QeiP) during hemodialysis.

In vivo solute clearances can be estimated from dialyzer blood (Qb) and dialysate (Qd) flow rates and a solute- and dialyzer-specific overall permeability membrane area product (KoA). However, these calculations require knowledge of the flow rate of the effective solute distribution volume in the flowing bloodstream (Qe) in order to calculate in vivo clearances and KoAs. We have determined Qe for urea, creatinine, and inorganic phosphorus from changes in concentrations across the blood compartment and mass balance between the blood and dialysate streams. We made four serial measurements over one dialysis in 23 patients and found that Qeu equals the total blood water flow rate, Qecr equals the plasma water flow rate plus 61% of red cell water flow rate, and QeiP is limited to the plasma water flow rate. Equations are derived to calculate Qe for each of these solutes from Qb and hematocrit and in vivo KoAs for each solute were calculated.

Creatine↗