The analgesic efficacy of preoperative high dose (40 mg x kg(-1)) oral acetaminophen after bilateral myringotomy and tube insertion in children.
BACKGROUND
The purpose of this study was to measure the plasma levels and analgesic effectiveness of a dose of 40 mg x kg(-1) of preoperative oral acetaminophen.


METHODS
Thirty children aged 55 (17-72) months undergoing bilateral myringotomy and tube insertion (BMT) received acetaminophen 40 mg x kg(-1) p.o. preoperatively. Plasma levels were measured, at 29 (10-51) min and at 60 min in the postanaesthesia care unit (PACU). Children's Hospital of Eastern Ontario Pain Scale (CHEOPS), for all subjects and the Poker Chip Tool (PCT) a self-report scale for subjects aged > 4 years, were used. After discharge, 24-h analgesic efficacy was evaluated using an observer Visual Analogue Scale (VAS) score and further acetaminophen use was recorded.


RESULTS
Plasma concentrations were 259 (60-391) micromol x l(-1) and 250 (135-450) micromol x l(-1), respectively. All 60 min plasma concentrations were > or = 70 micromol x l(-1) (ED50 for adenotonsillectomy) and less than 800 micromol x l(-1) (associated with toxicity). Twenty-six subjects (87%) had adequate analgesia (CHEOPS < or = 8). The PCT was only understood in the PACU by 13 of the 21 children > 4 years (62%). The median worst 24-h observer VAS was 0.5 (0-5.5) (27 subjects). No further analgesic was required after discharge in 16/28 (57%). A higher plasma level was associated with fewer doses of acetaminophen after discharge (r = -0.36, P=0.05).


CONCLUSIONS
No relationship was evident between age, the 60 min plasma acetaminophen level and the CHEOPS carried out at the same time. Acetaminophen 40 mg x g(-1) p.o. results in 60 min plasma levels of 250 (135-450) micromol x l(-1). The in-hospital analgesic efficacy was 87% (CHEOPS < 9, no further analgesics) and the 24-h efficacy was 57% (need for further acetaminophen).
Bolton
Phillip
P
Department of Anaesthesia, University of British Columbia and British Columbia's Children's Hospital, Vancouver, British Columbia, Canada.
Bridge
Hilary S
HS
Montgomery
Carolyne J
CJ
Merrick
Pamela M
PM
D000082:Acetaminophen / Q000008:administration & dosage* / Q000097:blood; D000284:Administration, Oral; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage* / Q000097:blood; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008876:Middle Ear Ventilation; D010147:Pain Measurement; D011300:Preoperative Care
D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen