The aim of our study was to evaluate the pharmacokinetics and pharmacodynamics of
ropivacaine in ilioinguinal-iliohypogastric blocks (IIB). After ethics committee approval and informed consent, 80 male adults scheduled for
inguinal hernia repair were enrolled and randomized into four groups. After induction of
general anesthesia, an IIB was performed double blinded in Groups 1, 2, and 3 with 0.25 mL/kg
ropivacaine 2 mg/mL, 5 mg/mL, or 7.5 mg/mL and with saline in the Control group. Plasma concentration of
ropivacaine was determined in venous blood using reversed-phase high-performance liquid chromatography. IIB with
ropivacaine resulted in peak plasma concentrations of 0.3+/-0.15 microg/mL (Group 1) (mean +/- SD), 0.75+/-0.45 microg/mL (Group 2), or 1.57+/-0.82 microg/mL (Group 3). These concentrations occurred after 30 (15-60) min, median (range), 30 (10-60) min, and 45 (15-60) min, in the respective groups. Three of 19 patients in Group 1, 6 of 18 in Group 2, and 5 of 20 in Group 3 did not need any additional
analgesics within 24 h postoperatively, but all 20 control patients did. Time to the first demand for
analgesia was significantly shorter in the Control group (median 0.3 h [range 0-2.8]) compared with 1.5 h (0.5-24 h), 2 h (0.5-24 h), and 2 h (1.0-24 h) in Groups 1, 2, and 3, respectively. Three patients in Group 3 had a postoperative motor block of the femoral nerve. In conclusion, a
ropivacaine dose of 0.25 mL/kg of 5 mg/mL seems adequate for IIB accompanying
general anesthesia for
postoperative pain relief. However, the pharmacokinetic results obtained suggest that even larger doses (0.25 mL/kg of 7.5 mg/mL
ropivacaine) for IIB do not result in plasma concentrations in a toxic range.
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