Extracellular Fluid Volume Calculation via Uric Acid Kinetics
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Solution Overview
Problem
Current methods for determining dry weight in hemodialysis patients are inaccurate and labor-intensive, relying on clinical symptoms and unreliable indicators like edema and atrial natriuretic peptide concentration, which can be incorrect, especially in patients with cardiac issues, leading to inappropriate extracellular fluid volume assessment.
Innovation Solution
A method and device for calculating extracellular fluid volume using pre- and post-hemodialysis plasma uric acid concentrations and removal volumes, allowing for precise assessment of extracellular fluid volume without requiring additional procedures or facilities, focusing on measurable differences in uric acid quantities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If clinical symptoms and edema assessment are used to determine dry weight, then the assessment process is simple, but the measurement precision is low and results are unreliable
Solution Approach 1:
The patent replaces the mechanical/clinical assessment system (physical examination, edema detection, symptom evaluation) with a biochemical measurement system based on uric acid concentration analysis. This substitution enables objective, quantifiable measurement of extracellular fluid volume through laboratory testing, thereby improving measurement precision while maintaining operational feasibility through routine blood sampling.
Solution Approach 2:
The patent introduces uric acid concentration as an intermediary substance to indirectly measure extracellular fluid volume. By measuring uric acid levels before and after hemodialysis and calculating the removal amount, the system derives extracellular fluid volume without directly measuring it, thus achieving high precision through a measurable intermediate parameter.
2Measurement precision
If atrial natriuretic peptide concentration or cardiothoracic ratio is used for assessment, then the measurement precision may improve, but the device complexity and cost increase
Solution Approach 1:
The patent employs a cost-effective approach by using routine uric acid blood tests, which are inexpensive and routinely performed in hemodialysis centers, replacing expensive and complex assessments such as atrial natriuretic peptide measurements and chest X-ray imaging. This achieves comparable or superior precision at lower cost and with simpler infrastructure.
3Ease of operation
If edema assessment is used, then the ease of operation is maintained, but the reliability deteriorates in patients with cardiac failure and valvular disease
Solution Approach 1:
The patent extracts the assessment from dependence on cardiac function indicators (edema, heart size, natriuretic peptides) that are unreliable in cardiac patients. By using uric acid kinetics instead, the method isolates the measurement from cardiac pathology interference, thereby maintaining ease of operation while improving reliability across all patient populations including those with heart failure.
4Ease of operation
If trial and error method based on clinical symptoms is used to determine dry weight, then the ease of operation is maintained, but the time required for repeated reassessments increases as body composition changes
Solution Approach 1:
The patent implements a feedback mechanism where extracellular fluid volume is objectively measured through uric acid kinetics, providing quantitative data that guides dry weight determination. This replaces the iterative trial-and-error process with a more direct assessment, reducing the frequency and time of reassessments needed when body composition changes, while maintaining operational simplicity.
Data Source
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AI summary
An extracellular fluid volume calculator may include: a first acquirement unit configured to acquire a pre-hemodialysis plasma uric acid concentration, a post-hemodialysis plasma uric acid concentration, a removal amount of uric acid by hemodialysis, and a removal volume of water during hemodialysis; and a first processor configured to calculate an extracellular fluid volume based on a difference between a pre-hemodialysis amount of uric acid and a post-hemodialysis amount of uric acid, the difference being determined based on the pre-hemodialysis plasma uric acid concentration, the post-hemodialysis plasma uric acid concentration, the removal amount of uric acid, and the removal volume of water acquired by the first acquirement unit.