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The analgesic efficacy of preoperative high dose (40 mg/kg) oral acetaminophen after bilateral myringotomy and tube insertion in children.

Bolton P, Bridge HS, Montgomery CJ, Merrick PM. Paediatric Anaesthesia 12:29-35, 2002.

Review: This prospective descriptive study evaluated the efficacy of oral acetaminophen 40 mg/kg in 30, ASA 1 or 2, patients, aged 1-6 years. Acetaminophen was administered orally 30 minutes preoperatively. Patients were not premedicated and underwent inhalation induction and maintenance of anesthesia with nitrous oxide, oxygen and sevoflurane. Venous samples were obtained from an indwelling IV cannula approximately 30 and 60 minutes following administration of acetaminophen. Analgesia was assessed in PACU using the CHEOPS score or Poker Chip Tool. After discharge home, parents assessed pain using a visual analog scale. In PACU, breakthrough pain was treated with oral codeine. Plasma acetaminophen concentrations were 256 (60-391) umol/l and 250 (135-450) umol/l, respectively. Twenty-six (87%) of patients had adequate analgesia in PACU, and 16 (57%) of patients did not require additional analgesia following discharge.

Comment: Acetaminophen is a useful analgesic for mild to moderate pain and is an effective adjunct for moderate to severe pain. Acetaminophen alone, however, has not proven to have a consistently high degree of efficacy in patients, undergoing myringotomy and tube insertion. Rectal administration, even at high doses (40 mg/kg), is associated with variable absorption and longer time to achieve therapeutic plasma levels. Routine administration of more potent analgesics, e.g., codeine, morphine or fentanyl, produces consistently effective analgesia but contributes to postoperative nausea and vomiting. This study demonstrates that oral administration of high dose acetaminophen produces therapeutic plasma levels within 30-60 minutes. Nevertheless, 13% of patients still received oral codeine for breakthrough pain while in PACU. The authors note that reliable assessment of pain is difficult in this age group. Some of these patients may have been distressed for reasons other than pain due to myringotomy and tube insertion. The authors caution that if high dose acetaminophen is used, parents must receive explicit instructions regarding administration of additional doses so that hepatic toxicity is avoided. The authors recommend limiting the total daily dose of acetaminophen to < 90 mg/kg/day for a maximum of five days.

Reviewed by: John T. Algren, MD
Vanderbilt Children's Hospital
Nashville, TN
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