1: Can J Anaesth.  2003 Jun-Jul;50(6):593-8.  

In children, the addition of epinephrine modifies the pharmacokinetics of
ropivacaine injected caudally.

Van Obbergh LJ, Roelants FA, Veyckemans F, Verbeeck RK.

Department of Anesthesiology, Universite catholique de Louvain, Brussels,
Belgium. vanobbergh@anes.ucl.ac.be

PURPOSE: To describe the modification of the ropivacaine (R) pharmacokinetics
produced by the addition of epinephrine (E). METHODS: After Institutional Review
Board approval, 18 ASA I boys received a caudal block (1 mL x kg(-1)) with
either plain 0.2% R (Group E-) or with 0.2% R containing E (5 microg x mL(-1);
Group E+). Venous blood samples were taken at zero, 15, 30, 60, 90, 120, 180,
240, 420, 720, 1440 min after caudal injection. Total R concentration in plasma
was determined by high pressure liquid chromatography. Maximal concentration
(C(max)) and time to peak concentration (T(max)) were obtained from the data,
terminal half-life (T(1/2z)), clearance (Cl) and volume of distribution (Vd)
were estimated by a non-compartmental approach. Subsequently, in order to
determine the absorption rate (Ka) and to reduce to number of blood samples, 25
other children, receiving plain R and another group of 25 receiving the E
solution were studied using a population approach (NONMEM). A one compartment
model with first order absorption was used. The effect of weight, age and E on
Cl, Vd and Ka was estimated. RESULTS: C(max) was significantly lower in Group E+
(0.93 mg x L(-1) +/- 0.29 vs 0.61 mg x L(-1) +/- 0.28, P = 0.05) and T(max)
occurred later (124 min +/- 53 vs 47 min +/- 16, P = 0.003). Weight was a
significant covariate for Cl and Vd while E significantly slowed R Ka [Group I
Ka 0.025 min(-1) [coefficient of variation (CV) 21%] vs 0.078 min(-1) (CV 25%)
in Group II]. CONCLUSION: The addition of E significantly modifies the
pharmacokinetics of R injected caudally.

PMID: 12826553 [PubMed - indexed for MEDLINE]