The Ropivacaine Concentration Required for Ultrasound-Guided Ilioinguinal/Iliohypogastric Nerve Block in Pediatric Patients.
To the best of our knowledge, the ropivacaine concentration required for ultrasound-guided ilioinguinal and iliohypogastric nerve block (INB) has not been reported. We designed this study to examine the 50% effective concentration (EC50) of ropivacaine for ultrasound-guided INB in children anesthetized with 2% sevoflurane.



We studied 30 consecutive children (age range, 6 months to 11 years) ASA physical status I to II undergoing unilateral open inguinal hernia repair. General anesthesia was induced by sevoflurane and maintained with 2% end-tidal concentration of sevoflurane in air and oxygen (FIO2 = 0.4). Ultrasound-guided INB was performed using a 3 mL ropivacaine solution. The first child received 0.3% ropivacaine, and subsequent concentrations were determined by the response of the previous patient to initial skin incision using Dixon up-and-down method. The testing interval was set at 0.1%, and the lowest concentration was 0.05% (0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%). The EC50 for INB of ropivacaine was analyzed using probit test.



The concentration at which all patients showed complete block was 0.50%, according to the up-and-down method. The EC50 was 0.21% (95% confidence interval, 0.03-0.34).



The EC50 of ropivacaine for ultrasound-guided INB was 0.21% (95% confidence interval, 0.03-0.34), in pediatric patients anesthetized with 2% sevoflurane.
From the Faculty of Medicine, Division of Clinical Medicine, Department of Anesthesiology, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Kumiko
K
Yamada
Shinichi
S
Inomata
Makoto
M
Tanaka
D000367:Age Factors; D000577:Amides / Q000008:administration & dosage* / Q000009:adverse effects; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D006552:Hernia, Inguinal / Q000175:diagnosis / Q000601:surgery*; D059685:Herniorrhaphy; D006801:Humans; D007267:Injections; D007564:Japan; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D011446:Prospective Studies; D000077212:Ropivacaine; D012684:Sensory Thresholds / Q000187:drug effects*; D000077149:Sevoflurane; D018084:Ultrasonography, Interventional
D000577:Amides; D018685:Anesthetics, Inhalation; D000779:Anesthetics, Local; D008738:Methyl Ethers; D000077149:Sevoflurane; D000077212:Ropivacaine