Plasma concentrations of levobupivacaine associated with two different intermittent wound infusion regimens following surgical ductus ligation in preterm infants.

BACKGROUND

Administration of local anesthetics by a surgically placed wound catheter has recently been shown to reduce the need for postoperative morphine administration in extremely preterm infants undergoing ductus ligation. The primary aim of this randomized safety study was to define the plasma levels of levobupivacaine (LB) following two different intermittent infusion regimens.

METHODS

Eighteen preterm infants 23-27 gestational weeks, median birthweight 721 g scheduled for ductus ligation were included in the study. All patients were anesthetized according to a standardized protocol based on high-dose fentanyl (25-50 μg·kg(-1) ). Before skin closure, a subcutaneous catheter was inserted into the wound. The patients were randomized to receive one of the two intermittent infusion regimens: Group BII: Initial bolus plus early start of the intermittent infusion or Group DII: No bolus plus delayed start (8 h) of the intermittent infusion. Blood samples for determination of LB plasma concentrations were obtained on six occasions during the 24-h postoperative observation period, as well as hourly postoperative pain assessments using the Echelle Douleur Inconfort Noveau (EDIN) pain scale.

RESULTS

Plasma concentrations of LB ranged from 0.094 to 1.682 μg·ml(-1) and 0 to 0.549 μg·ml(-1) in group BII and DII, respectively. Both regimens were associated with low postoperative EDIN pain scores (24 h median of 0 and 1 in group BII and DII, respectively). No signs of systemic local anesthetic toxicity were noted.

CONCLUSIONS

The two studied intermittent infusion regimens were associated with plasma levels below potentially toxic levels and were both associated with adequate postoperative pain scores.