The number of injections does not influence local anesthetic absorption after paravertebral blockade.
OBJECTIVE
The aims of this study are to determine if the injection of a single large dose of local anesthetics into the paravertebral space increases the risks of inducing toxicity compared with multiple small injections and to describe ropivacaine plasma concentrations resulting from paravertebral blockade.


METHODS
Paravertebral blockade was performed using a solution of 10 mL ropivacaine 0.75%, 10 mL lidocaine CO2 2% plus 0.1 mL epinephrine 1:1000 either by a single injection at T3 or T4 (Group S, n = 6) or by five injections of 4 mL each at T2 to T6 (Group M, n = 8). Blood samples were taken at zero, five, ten, 15, 20, 30, 45, 60 and 90 min and at two, three, four, five, six and eight hours. Ropivacaine and lidocaine plasma concentrations were measured by high performance liquid chromatography.


RESULTS
Maximal plasma concentrations were comparable for lidocaine: 2.6 +/- 1.3 (S) vs 2.6 +/- 0.8 microg x mL(-1) (M) and for ropivacaine: 1.3 +/- 0.2 (S) vs 1.3 +/- 0.1 microg x mL(-1) (M). Area under the plasma concentration-time curve was higher in Group M for lidocaine: 577.6 +/- 146.1 vs 401.7 +/- 53.2 mg x min(-1) x mL(-1) (P = 0.04) but similar for ropivacaine: 381.1 +/- 95.4 (M) vs 363.1 +/- 85.3 mg x min(-1) x L(-1) (S).


CONCLUSIONS
The injection of a single large bolus of local anesthetics into the paravertebral space does not increase its absorption. Maximal ropivacaine plasma concentrations resulting from paravertebral blockade are similar to those reported with equivalent doses of bupivacaine.
Lemay
Erik
E
Department of Anesthesiology, Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada.
Guay
Joanne
J
Côté
Christiane
C
Boivin
Marie Claude
MC
Varin
France
F
D000042:Absorption; D000328:Adult; D000368:Aged; D000577:Amides / Q000008:administration & dosage; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006801:Humans; D007267:Injections; D008012:Lidocaine / Q000008:administration & dosage; D008875:Middle Aged; D009407:Nerve Block; D000077212:Ropivacaine
D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D008012:Lidocaine