Serum bupivacaine concentrations following wound infiltration in children undergoing inguinal herniotomy

Abstract

SummarySerum hupivacaine concentrations were measured in 12 children who underwent elective herniotomy and who received analgesia in the form of wound infiltration. Mean ( S D ) peak concentration was 0.36 (0.14) pgLglml and time to peak concentration was 14.6 (7.2) Local anaesthetic techniques are used widely to provide postoperative analgesia in children who undergo day-case herniotomy. Wound infiltration with bupivacaine has been shown to provide analgesia comparable to that associated with caudal block' or ilioinguinal block.2 Bupivacaine may produce toxic effects at plasma concentrations greater than 4 ~g / m l~.~ although the rate of increase of plasma concentration is an important f a~t o r .~.~ Both caudal and ilioinguinal blocks have been shown to result in concentrations well below 4 pg/mI.' Bupivacaine concentrations have been measured following subcutaneous injection: but this does not mimic the conditions of wound infiltration and this information is not available for this age group.The purpose of this study was to measure serum bupivacaine concentrations after wound infiltration for postoperative analgesia in children who underwent day-case herniotomy . MethodThe study was approved by the District ethics committee and informed consent was obtained from one or both parents. Twelve children aged between 2 and 10 years admitted for elective unilateral herniotomy as day-cases were studied. No premedication was given and general anaesthesia was induced by inhalation of halothane or by the intravenous route (following application of EMLA cream). Maintenance of anaesthesia was by spontaneous ventilation of 67% nitrous oxide in oxygen and halothane delivered by a T-piece or Bain coaxial system.A 20-gauge cannula was inserted into a vein on the dorsum of the hand either for intravenous induction or after inhalational induction, and was used for blood sampling. A baseline (2 ml) sample was taken prior to surgery. Before skin closure, the wound edges were infiltrated with 1.25 mg/kg of bupivacaine without adrenaline as either the 0.25% solution in children under 16 kg or as the 0.5% solution in those of greater weight. Further venous blood samples were taken at 5, 10, 15, 20, 30, 45 and 60 minutes after the completion of wound infiltration. The patency of the cannula was maintained with heparinised saline and the deadspace was aspirated on each occasion. Samples were placed in plain tubes and centrifuged to yield approximately 1 ml of serum which was stored at -70°C.Bupivacaine concentrations were measured by high pressure liquid chromatography using dichloromethane for the extraction and p-chlorodisopyramide as internal standard. Interassay coefficient of variation was 5.1% and intra-assay coefficient of variation was less than 10%. ResultsThe ages and weights of patients are shown in Table 1. A complete set of results was not obtained for all patients because of sampling difficulties. The serum bupivacaine concentrations in one patient were somewhat higher than the others. Consequently, the median an...

Plasma concentrations of bupivacaine after wound infiltration of an 0.5% solution after inguinal herniorrhaphy: a preliminary study

“…However, they took venous blood samples for only 60 minutes after bupivacaine infiltration. Our results show that the time to reach maximum plasma concentration may extend to 2 h. Hence, the previous study [11] may have significantly underestimated peak plasma bupivacaine concentrations.…”

“…Venous plasma bupivacaine concentrations have been reported after a single wound infiltration of bupivacaine for postoperative pain management after hernia repair in children [11]. Despite smaller doses of bupivacaine (1.25 mg. kg-1, ie.…”

Current management of pediatric postoperative pain

“…Since low doses of drug are used, blood concentrations are low and the risk of systemic toxicity and other adverse effects is also low [71]. However, to ensure a continuum of effective pain relief, other treatments should be initiated before the end of anticipated block performance [72].…”

The pharmacokinetics and safety of an intraoperative bupivacaine-collagen implant (XaraColl®) for postoperative analgesia in women following total abdominal hysterectomy

“…This compares with only 3.1 (1.4) hours reported for bolus intra-articular infiltration26 and 2.7 hours in adults following injection for nerve block 21. It is therefore reasonable to assume that some drug is still being slowly absorbed even as the plasma concentration decays following the second peak.…”

“…For example, in a pharmacokinetic study at a 100 mg dose, the t max in 12 men undergoing inguinal herniorrhaphy ranged from only 0.25 to 2 hours 25. In a similar herniotomy study in 12 children at a dose of 1.25 mg/kg, the mean (standard deviation) t max was only 14.6 (7.2) minutes and in another study in 11 patients undergoing knee arthroscopy,26 the mean (standard deviation) t max was 43.4 (23.1) minutes following 100 mg administered intra-articularly 27. However, despite the rapid systemic uptake, the mean C max remained well below the toxicity threshold at these relatively low bolus doses.…”