Abstract
The aim of the study was to evaluate pharmacokinetics of fentanyl administered as continuous epidural infusion with 0.2% ropivacaine for postoperative pain relief in infants and toddlers, and older children undergoing major abdominal and urological procedures. Thirteen infants and toddlers (median age 14 [range 3-36]months, 11 [5-17]kg, Group I) and 11 children (68 [45-131]months, 21 [16-52] kg, Group II) participated in the study. Epidural catheter was placed under general anesthesia in the L1-L2, L2-L3, or L3-L4 epidural space and threaded up to 4cm into the epidural space. Bolus dose of 0.2% ropivacaine, 0.5ml·kg(-1) and fentanyl, 2μg·kg(-1) was given, then followed by continuous infusion of 0.2% ropivacaine, 0.15ml·kg(-1) ·h(-1) with fentanyl 1.12μg·kg(-1) ·h(-1) . In the postoperative period, fentanyl dose was reduced to 0.375μg·kg(-1) ·h(-1) . With this dosing regimen, fentanyl concentration in plasma was within the range of analgesic concentrations, and did not exceed 1.0ng·ml(-1) . After discontinuation of epidural infusion, pharmacokinetics of fentanyl was complicated by a slight increase in plasma concentration during the elimination phase. Both elimination half-life of fentanyl (t1/2, MRT ) and mean residence time (MRT) were much longer than those observed after single IV bolus dose, and longer in Group I than in Group II (t1/2 MRT 15.9 [3.6-31.5]h vs 8.0 [7.1-13.3]h, P<0.05, MRTstop-last 22.9 [5.1-45.5]h vs 11.5 [10.2-19.1]h, P<0.05). Therefore, monitoring of vital signs seems warranted for several hours after the termination of the epidural infusion because risk of respiratory depression may persist, especially in the younger age group.
Published Version
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