Pharmacokinetics and clinical efficacy of long-term epidural ropivacaine infusion in children.

The clinical efficacy and pharmacokinetics of long-term epidural ropivacaine infusion were investigated in 18 postoperative children aged between 0.3 and 7.3 yr. A lumbar or thoracic epidural catheter was inserted after the anaesthetic induction. Sixty minutes following a bolus dose of ropivacaine 1 mg kg-1, 0.2% ropivacaine was infused at a fixed rate of 0.4 mg kg-1 h-1 for a mean of 61.3 h (range 36-96 h). Clinical evaluation comprised hourly recording of pain, sedation, motor block, nausea/vomiting, pruritus-scores, SpO2, pulse and respiratory rates, and recording of non-invasive arterial pressure every 4 h. Total and free plasma concentrations were measured by high-performance liquid chromatography at 0, 1, 6, 12, 24, 36, 48, 72 and 96 h. Analgesia was of high quality and side effects were minor. No clinical signs of local anaesthetic toxicity were seen. Total (100-3189 micrograms litre-1) and free (10-56 micrograms litre-1) ropivacaine concentrations were within the range reported to be 'safe' in previous studies in adults. Mean (95% CI) volume of distribution was 3.1 litre kg-1 (2.1-4.2 litre kg-1), total clearance was 8.5 ml kg-1 min-1 (5.8-11.1 ml kg-1 min-1), free clearance was 220 ml kg-1 min-1 (170-270 ml kg-1 min-1) and elimination half-life was 4.9 h (3.0-6.7 h).