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Plasma concentrations and pharmacokinetics of bupivacaine with and without adrenaline following caudal anaesthesia in infants
Author(s) -
Hansen T. G.,
Morton N. S.,
Cullen P. M.,
Watson D. G.
Publication year - 2001
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1034/j.1399-6576.2001.450107.x
Subject(s) - bupivacaine , medicine , anesthesia , pharmacokinetics
Background: The aim of this study was to determine whether the use of adrenaline 1/400 000 added to 0.25% bupivacaine significantly delays the systemic absorption of the drug from the caudal epidural space in young infants. Methods: Fifteen infants less than 5 months of age undergoing minor lower abdominal procedures under a standardised general anaesthetic were randomised to receive a caudal block with either 0.25% plain bupivacaine 2.5 mg/kg (n=7) or bupivacaine 0.25% with 1/400 000 adrenaline (n=8). Blood samples were drawn at 30, 60, 90, 180, 240 and 360 min according to the infant’s weight and analysed for total and free bupivacaine concentrations using a gas chromatography‐mass spectrometry (GC‐MS) technique. Results: The total C MAX and T MAX were comparable in both groups. The total bupivacaine concentration at t=360 min was significantly higher in the “adrenaline” group compared to the “plain” group, i.e. a median (range) 742 ng/ml (372–1423 ng/ml) vs. 400.5 ng/ml (114–446 ng/ml), P =0.0080. The median “apparent” terminal half‐life (t½) was significantly longer in the “adrenaline” group (363 min; range 238–537 min) compared to the “plain” group (n=6) (165 min; range 104–264 min), P =0.0087. The free bupivacaine concentrations (n=3 in both groups) ranged between 13 ng/ml and 52 ng/ml, corresponding to a percentage of free bupivacaine between 1.3% and 6.7%. Conclusion: The addition of 1/400.000 adrenaline prolongs the systemic absorption of caudally administered bupivacaine in infants less than 5 months of age.