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PEDIATRIC ANESTHESIOLOGY

Ultrasound Versus Landmark-Based Technique for Ilioinguinal-Iliohypogastric Nerve Blockade in Children: The Implications on Plasma Levels of Ropivacaine

Marion Weintraud, MD^*, Märit Lundblad, MD, Stephan C. Kettner, MD^*, Harald Willschke, MD^*, Stephan Kapral, MD^*, Per-Arne Lönnqvist, MD, Karl Koppatz, Klaus Turnheim, MD, Adrian Bsenberg, MD, and Peter Marhofer, MD^*

From the *Department of Anesthesia and Intensive Care Medicine, Medical University of Vienna, Vienna, Austria; Department of Anesthesia and Intensive Care, Karolinska Hospital/Astrid Lindgren Hospital, Stockholm, Sweden; Department of Pharmacology, Medical University of Vienna, Vienna, Austria; and Department of Anesthesia, University Cape Town, Red Cross Children Hospital, Cape Town, South Africa.

Address correspondence and reprint requests to Peter Marhofer, MD, Department of Anesthesia, Intensive Care Medicine and Pain Therapy, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna. Address e-mail to peter.marhofer{at}meduniwien.ac.at.

Abstract

BACKGROUND: Ilioinguinal-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.

METHODS: After 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 (dC₀/dt), and area under the curve value (AUC) were determined.

RESULTS: The ultrasound-guided technique resulted in higher C_max (sd), k_a, dC₀/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] µg/mL, P < 0.01; k_a: 14.4 [10.7] vs 11.7 [11.4] h^–1, P < 0.05; dC₀/dt: 0.26 [0.12] vs 0.15 [0.03] µg/mL · min, P < 0.01; AUC: 42.4 [15.9] vs 27.2 [18.1] µg · 30 min/mL, P < 0.001; t_max: 20.4 [8.6] vs 25.3 [7.6] min, P < 0.05).

CONCLUSIONS: The 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.