Density Change of Local Anesthetics and a Mixed Solution Can Be Estimated by Refractometry / 대한마취과학회지

BACKGROUND: Baricity of the local anesthetics is a major determinant of the distribution of local anesthetics in CSF. The purpose of this study was to assess the value of refractometry in measuring the specific gravity of CSF, local anesthetics and adding solutions, and then comparing these to the density of CSF and local anesthetics. METHODS: CSF samples were obtained from 30 patients during spinal anesthesia. 0.5% hyperbaric tetracaines were diluted with CSF to create a 1:1 to 1:10 density and specific gravity measurements were made at room temperature, using a refractometer. 2% lidocaine was diluted with distilled water, normal saline, 5% and 10% dextrose water to create 2%, 1%, 0.67%, 0.5% and 0% mixtures measured respectively. RESULTS: Specific gravity of CSF was 1.0066 +/- 0.0006 and SG of 0.5% tetracaine was 1.0285 +/- 0.0028. The effect of specific gravity on the concentrations of tetracaine was determined by linear regression with r = 0.9803, y = 1.0060 + 0.0440 X x. Dilutions of 2% lidocaine with adding solutions were distilled water, y = 1.0008 + 0.0078 X x ; normal saline, y = 1.0056 + 0.0053 X x ; 5% dextrose, y = 1.0208 - 0.0022 X x ; and 10% dextrose, y = 1.0436 - 0.0135 X x. CONCLUSIONS: The relationship between concentration and specific gravity of local anesthetics is linear. We conclude that refractometry is a reliable method to predict density of local anesthetics.

Efficacy of an Epidural Test Dose with Intravenous Isoproterenol in Enflurane-Anesthetized Adults / 대한마취과학회지

BACKGROUND: The efficacy of an epidural test dose for detecting inadvertent intravascular injection during general anesthesia with volatile anesthetics has not been clearly determined. The object of this study is to evaluate the efficacy of a simulated intravenous isoproterenol test dose in adult patients anesthetized with O2-N2O-enflurane. METHODS: Forty-five healthy adult patients were anesthetized with 1 vol% enflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1, 2 and 3 microgram groups (n = 15 each) received 3 ml of 2% lidocaine with 1, 2 and 3 microgram isoproterenol IV respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. RESULTS: Mean maximal heart rate increases were 15 8, 21 8, and 27 10 bpm (mean SD) in the isoproterenol 1, 2 and 3 microgram groups, respectively. Isoproterenol 3 microgram produced 100% sensitivity in the modified (> or = 10 bpm increase) HR criteria and 67% sensitivity in the conventional (> or = 20 bpm increase) HR criteria. CONCLUSIONS: To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The epidural test dose containing 3 microgram isoproterenol might be a reliable marker for intravascular injection based on the modified HR criterion.

Efficacy of an Epidural Test Dose with Intravenous Isoproterenol in Enflurane-Anesthetized Adults / 대한마취과학회지

BACKGROUND: The efficacy of an epidural test dose for detecting inadvertent intravascular injection during general anesthesia with volatile anesthetics has not been clearly determined. The object of this study is to evaluate the efficacy of a simulated intravenous isoproterenol test dose in adult patients anesthetized with O2-N2O-enflurane. METHODS: Forty-five healthy adult patients were anesthetized with 1 vol% enflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1, 2 and 3 microgram groups (n = 15 each) received 3 ml of 2% lidocaine with 1, 2 and 3 microgram isoproterenol IV respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. RESULTS: Mean maximal heart rate increases were 15 8, 21 8, and 27 10 bpm (mean SD) in the isoproterenol 1, 2 and 3 microgram groups, respectively. Isoproterenol 3 microgram produced 100% sensitivity in the modified (> or = 10 bpm increase) HR criteria and 67% sensitivity in the conventional (> or = 20 bpm increase) HR criteria. CONCLUSIONS: To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The epidural test dose containing 3 microgram isoproterenol might be a reliable marker for intravascular injection based on the modified HR criterion.