Clinically relevant concentration determination of inhaled anesthetics (halothane, isoflurane, sevoflurane, and desflurane) by 19F NMR.

Biophysical studies of protein-anesthetic interactions using nuclear magnetic resonance (NMR) spectroscopy are often conducted by the addition of micro amounts of neat inhaled anesthetic which yields much higher than clinically relevant (0.2-0.5 mM) anesthetic concentrations. We report a 19F NMR technique to measure clinically relevant inhaled anesthetic concentrations from saturated aqueous solutions of these anesthetics (halothane, isoflurane, sevoflurane, and desflurane). We use a setup with a 3-mm NMR tube (containing trifluoroacetic acid as standard), coaxially inserted in a 5-mm NMR tube containing anesthetic solution under investigation. All experiments are conducted in a 5-mm NMR probe. We also have provided standard curves for four inhaled anesthetics using NMR technique. The standard curve for each of these anesthetics is helpful in determining the prerequisite amount of aqueous anesthetic solution required to prepare clinically relevant concentrations for protein-anesthetic interaction studies.