BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the effect of age on the pharmacokinetics of lidocaine after epidural administration. METHODS: Two percent lidocaine with epinephrine (5 microg/mL) was administered in two different age groups: an adult group (age 42 +/- 6 years, n = 10) and an elderly group (age 77 +/- 4 years, n = 10). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15, 30, 45, 60, 90, 120, 150, and 180 minutes of administration using high-performance liquid chromatography with ultraviolet detection. RESULTS: No significant differences in plasma concentrations of lidocaine and its metabolites were observed between the two groups during the 3 hours of study. However, the elderly group showed significantly longer mean residence times (MRTs) and lower plasma clearance of lidocaine during the period compared with the adult group (P < .05). Plasma concentration ratios of MEGX/lidocaine were significantly lower in the elderly group after 2 hours of lidocaine administration (P < .05). CONCLUSIONS: The increase in plasma lidocaine concentration after epidural anesthesia in elderly patients was not as high as anticipated. However, the elderly patients showed longer MRTs, lower clearance, and lower ratios of MEGX/lidocaine than did the adult (middle-age) patients.

Adult↗

PubMedDate not supplied

Plasma concentrations of lidocaine and its principal metabolites during continuous epidural infusion of lidocaine with or without epinephrine.

BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the effect of epinephrine on the absorption of lidocaine and the accumulation of active metabolites of lidocaine during continuous epidural anesthesia. METHODS: Lidocaine was administered as an initial bolus of 5 mg/kg of 2% lidocaine solution followed by continuous infusion at 2.5 mg/kg/h. Patients in group I (n = 10) received lidocaine alone and patients in group II (n = 10) received lidocaine + epinephrine (5 pg/mL). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15 minutes, 30 minutes, and 1, 2, and 3 hours of infusion using high-performance liquid chromatography with ultraviolet detection. RESULTS: Plasma lidocaine concentrations were higher in group I for the first 30 minutes; however, after 1 hour the levels were the same. Plasma MEGX and GX increased continuously in both groups. MEGX levels the were significantly higher in group I, but there was no significant difference in the sum of lidocaine + MEGX after 2 hours. There was no significant difference in GX levels between the two groups. CONCLUSIONS: With respect to continuous epidural administration, addition of epinephrine to lidocaine solutions is ineffective after 2 hours for reducing the potential for systemic toxicity, because the sum of the plasma concentrations of lidocaine and its principal active metabolite, MEGX, are unaffected.

Absorption↗

PubMedDate not supplied

Local pulsatile intramyocardial pressure (IMP) as a vector force: simultaneous measurements of IMP and tissue oxygen availability.

A directional nonuniformity of the intramyocardial pressure (IMP) was observed in anesthetized open-chest dogs using a piezoelectric pressure sensor implanted in the left ventricular myocardium. The nonuniformity seemed to be attributable to the variation in myocardial fiber orientation. The IMP, which developed in a direction parallel to the base-apex line, was measured in the deep portion of the myocardium, simultaneously with local O2 availability. In some cases, IMP decreased quickly as soon as a decrement in O2 availability had proceeded only slightly as a result of ligation of the anterior descending artery (LAD). In other cases, the once decreased IMP recovered gradually even when O2 availability remained lowered by continuation of the ligation. These observations indicated that IMP had no direct dependency on O2 availability in the case of acute LAD.

Animals↗