Adrian Bösenberg1, Jackson Thomas2, T. Lopez2, Gunilla Huledal3, Lennart Jeppsson3, L. E. Larsson3
1Departments of Anaesthesia, University of Natal, Durban, and
2Red Cross Children's Hospital, Cape Town, South Africa
3Clinical R&D, AstraZeneca Södertälje, Sweden
Tóm tắt
Background: For documenting the properties of ropivacaine used for regional anaesthesia in children, the relationship between dose and resulting systemic exposure is essential. The aim of this pharmacokinetic part of a randomised, multicentre, double‐blind study was to determine the free and total plasma levels of ropivacaine in children aged between 4 and 12 years following a single‐shot caudal dose of 1, 2 or 3 mg/kg of ropivacaine for postoperative pain management.Method: Following induction of a standardised general anaesthetic (halothane; nitrous oxide: oxygen 60:40), a caudal block using 1 ml/kg ropivacaine in concentrations of 1, 2 or 3 mg/ml was performed in 43 ASA I children (body weight 12–25 kg) scheduled for elective inguinal surgery. Blood samples were collected prior to and 15, 30, 45, 60 and 240 min after placement of the caudal block for determination of total and free ropivacaine plasma concentrations.Results: The peak plasma concentration of total ropivacaine, reached within 15–241 min after the block, increased in proportion to dose, with mean values at 0.27, 0.64 and 0.90 mg/l following 1, 2 and 3 mg/kg respectively. The peak plasma level of free ropivacaine also increased in a dose‐proportional manner, with mean levels at 0.014, 0.030 and 0.042 mg/l. The highest individual peak plasma level of free ropivacaine was 0.070 mg/l, well below the threshold levels of CNS toxicity described in adults. No clinical signs of systemic toxicity were observed.Conclusion: Following single‐shot caudal doses of 1–3 mg/kg in children up to 25 kg and aged between 4 and 12 years, plasma levels of free ropivacaine increase in proportion to dose and all were shown to be within safe limits.
