• Marion Weintraud, Märit Lundblad, Stephan C Kettner, Harald Willschke, Stephan Kapral, Per-Arne Lönnqvist, Karl Koppatz, Klaus Turnheim, Adrian Bsenberg, and Peter Marhofer.
• Department of Anesthesia, Intensive Care Medicine and Pain Therapy, Medical University of Vienna, Vienna, Austria.
• Anesth. Analg. 2009 May 1;108(5):1488-92.

BackgroundIlioinguinal-iliohypogastric nerve blockade (INB) is associated with high plasma concentrations of local anesthetics (LAs) in children. Ultrasonographic guidance enables exact anatomical administration of LA, which may alter plasma levels. Accordingly, we compared plasma levels of ropivacaine after ultrasonographic versus landmark-based INB.MethodsAfter induction of general anesthesia, 66 children (8-84 mo) scheduled for inguinal hernia repair received INB with 0.25 mL/kg of ropivacaine 0.5% (1.25 mg/kg) either by a landmark-based (n = 31) or by an ultrasound-guided technique (n = 35). Ropivacaine plasma levels were measured before (0) and 5, 10, 20, and 30 min after the LA injection, using high-performance liquid chromatography. Maximum plasma concentrations (C(max)), time to C(max) (t(max)), the absorption rate constant (k(a)), the speed of rise of the plasma concentration at Time 0 (dC(0)/dt), and area under the curve value (AUC) were determined.ResultsThe ultrasound-guided technique resulted in higher C(max) (sd), k(a), dC(0)/dt, and AUC values and shorter t(max) compared with the landmark-based technique (C(max): 1.78 [0.62] vs 1.23 [0.70] microg/mL, P < 0.01; k(a): 14.4 [10.7] vs 11.7 [11.4] h(-1), P < 0.05; dC(0)/dt: 0.26 [0.12] vs 0.15 [0.03] microg/mL . min, P < 0.01; AUC: 42.4 [15.9] vs 27.2 [18.1] microg . 30 min/mL, P < 0.001; t(max): 20.4 [8.6] vs 25.3 [7.6] min, P < 0.05).ConclusionsThe pharmacokinetic data indicate faster absorption and higher maximal plasma concentration of LA when ultrasound was used as a guidance technique for INB compared with the landmark-based technique. Thus, a reduction of the volume of LA should be considered when using an ultrasound-guided technique for INB.

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