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Determination of anaesthetic agent concentration by refractometry
J M Allison1, R S Gregory, K P Birch
1Division of Mechanical and Optical Metrology, National Physical Laboratory, Teddington, Middlesex.
British Journal of Anaesthesia
|January 1, 1995
Summary
Reference refractivity values for anesthetic agents like halothane and sevoflurane were established. A refractometry method allows for accurate measurement of anesthetic agent concentration, with potential for routine clinical use.
Area of Science:
- Anesthesiology
- Analytical Chemistry
- Metrology
Background:
- Accurate measurement of anesthetic agent concentration is crucial for patient safety and effective anesthesia delivery.
- Current methods may have limitations in precision or accessibility for routine monitoring.
- Refractometry offers a potential optical method for quantifying volatile anesthetic agents.
Purpose of the Study:
- To derive reference refractivity values for common anesthetic agents traceable to national standards.
- To develop a simple method and equation for determining anesthetic agent concentration using refractometry.
- To assess and quantify the instrumental sources of uncertainty in this measurement approach.
Main Methods:
- Derivation of reference refractivity values for halothane, isoflurane, enflurane, sevoflurane, and desflurane.
- Development of a mathematical equation linking refractivity measurements to agent concentration.
- Quantification of uncertainties from instrumental factors affecting refractometric measurements.
Main Results:
- Established traceable reference refractivity values for five key anesthetic agents.
- Validated a simple refractometric method for calculating anesthetic agent concentration.
- Identified and quantified major sources of instrumental uncertainty.
Conclusions:
- The developed refractometric method enables accurate measurement of anesthetic agent concentration.
- Routine monitoring of anesthetic agent concentration at a +/- 1% uncertainty level is achievable.
- This approach provides a reliable tool for anesthesia monitoring and quality control.
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