title: Plasma ropivacaine concentrations during bilateral transversus abdominis plane infusions.
abstract: BACKGROUND
  The transversus abdominis plane (TAP) block is a regional anaesthetic technique that blocks abdominal wall somatic afferent nerves. We conducted a prospective observational study to evaluate the venous plasma concentrations of ropivacaine during a continuous TAP infusion.
  
  
  METHODS
  Twenty patients who were planned to undergo intra-abdominal cavity surgery requiring a mid-line laparotomy incision were enrolled. Patients were excluded if they had a history of chronic pain, opioid tolerance, renal or hepatic impairment, or contraindication to study medications. Subjects received a standardized general anaesthetic, and at the completion of surgery, ultrasound-guided subcostal or posterior TAP blocks and catheters. A TAP infusion of 2 mg ml(-1) ropivacaine was administered for 72 h after operation. Data collection during the 72 h included morphine requirements, pain scores, and plasma ropivacaine levels.
  
  
  RESULTS
  TAP blocks and catheters were successfully inserted in all recruited subjects. The fourth subject experienced neurological symptoms attributed to local anaesthetic toxicity, but did not have high plasma ropivacaine concentrations. However, the protocol was amended for the subsequent 16 subjects, to a weight-based dosing regimen. The range of total plasma ropivacaine concentrations was 0.98-3.41 mg litre(-1) for posterior infusions and 0.96-3.48 mg litre(-1) for subcostal infusions. Four subjects had total ropivacaine levels >3.4 mg litre(-1). The range of unbound plasma ropivacaine concentrations was 0.022-0.135 mg litre(-1) for posterior infusions and 0.031-0.120 mg litre(-1) for subcostal infusions.
  
  
  CONCLUSIONS
  Given the potential for high plasma concentrations from a bilateral TAP infusion technique, attention should be paid to individualized dosing strategies.
authors.affiliation: Department of Anaesthesia and Pain Medicine, Western Health, 148 Gordon St Footscray, VIC 3011, Australia. elizabeth.hessian@wh.org.au
authors.forename: E C
authors.initials: EC
authors.lastname: Hessian
authors.forename: B E
authors.initials: BE
authors.lastname: Evans
authors.forename: J A
authors.initials: JA
authors.lastname: Woods
authors.forename: D J
authors.initials: DJ
authors.lastname: Taylor
authors.forename: E
authors.initials: E
authors.lastname: Kinkel
authors.forename: A R
authors.initials: AR
authors.lastname: Bjorksten
mesh_terms: D034861:Abdominal Wall / Q000000981:diagnostic imaging / Q000294:innervation* / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000577:Amides / Q000097:blood*; D000768:Anesthesia, General; D000779:Anesthetics, Local / Q000097:blood*; D002404:Catheterization; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000188:drug therapy*; D011446:Prospective Studies; D000077212:Ropivacaine; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine
keywords: anaesthetics local, ropivacaine; analgesia postoperative; analgesic techniques, infusion; surgery, abdominal; toxicity, local anaesthetics