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- Title
Estimation of weight loss during coil dialysis.
- Authors
Nolph, Karl D.; Groshong, Ted D.; Maher, John F.; Nolph, K D; Groshong, T D; Maher, J F
- Abstract
Estimation of weight loss during coil dialysis. The ultrafiltration rate (UF, mI/min) during hemodialysis should be a function of the mean net hydrostatic and effective osmotic transmembrane pressure gradients between blood and dialysate. At constant perfusate temperature and protein concentration, UF collected directly from coils perfused in vitro without dialysate has been shown to be a linear function of mean coil pressure (MCP: inlet plus outlet pressure/2). Other variables such as hematocrit and blood flow rate do not affect this relationship. The deviation from this relationship due to dialysate hydrostatic pressure and blood-dialysate effective osmotic gradients during clinical dialysis has not been assessed. To determine if such deviation is minimal and if weight loss during clinical dialysis could be predicted from MCP, net weight (wt) loss (fasting dialysis wt loss minus basal overnight measured wt loss; g/min) was compared to UF collected directly from the same coil at identical MCP in 100 clinical dialysis studies using six coil types (EX-03, EX-01, UF-145, UF-100 cupraphane, UF-100 cellophane, UF-60 pediatric). For each coil type, the characteristic in vitro linear relationship of UF to MCP, the coil resistance under standard conditions as a relative index of expected MCP range, and the effects of dialysate flow on coil resistance were determined. The studies show that under comparable conditions, different coil types function at different MCP as a function of coil resistance and manifest a characteristic linear relationship of directly measured UF to MCP. For non-encased coils observed net wt loss and predicted net wt loss from directly measured UF were essentially identical. For encased EX coils, net wt loss was less than predicted. This most likely reflects effects of relatively higher dialysate hydrostatic pressure in EX coils. Accordingly, only the resistance of EX coils was increased by dialysate flow, and differences between predicted and observed weight losses were eliminated with negative pressure dialysate flow. Arterial-dialysate osmolality ranged from -3 to + 56 mOsm/kg H2O and had no apparent effect on wt loss. Correction for relatively constant differences of predicted and observed wt loss in EX coils permits accurate prediction of wt loss from MCP for all coils studies.
- Subjects
WEIGHT loss; ESTIMATION theory; DIALYSIS (Chemistry); ULTRAFILTRATION; TESLA coils; HYDROSTATICS; COMPARATIVE studies
- Publication
Kidney International, 1972, Vol 1, Issue 3, p182
- ISSN
0085-2538
- Publication type
journal article
- DOI
10.1038/ki.1972.25