Korean J Anesthesiol.  2001 Dec;41(6):767-774. 10.4097/kjae.2001.41.6.767.

The Value of Systemic Ketamine for Preemptive Analgesia in a Rat Model for ostoperative Pain

• Lee HJ
• Choi JH
• Moon SH

• KMID: 2091645
• DOI: http://doi.org/10.4097/kjae.2001.41.6.767

Abstract

BACKGROUND: Pretreatment of systemic ketamine reduced pain behaviors in some animal models with persistent pain. However, a clinically relevant preemptive analgeisic effect of systemic ketamine is controversial. The purpose of this study was to examine the preemptive effect of systemic ketamine in rats undergoing a plantar incision.
METHODS
Ketamine (10, 30, or 100 mg/kg) or a saline vehicle was administered subcutaneously 30 minutes before an incision was made. Withdrawal thresholds to calibrated von Frey filaments adjacent to the wound were measured before incision and from 2 hours to postoperative 6 days after incision. To evaluate the effectiveness of an extension of antinociceptive treatment into the initial postoperative period, 30 mg/kg ketamine or a saline vehicle 30 minutes before an incision was made was administered subcutaneously followed by injection of 5 more of the same drug or vehicle every 1 hour. The development of pain behavior was also evaluated before incision and from 30 minutes after last drug injection to postoperative 6 days.
RESULTS
In saline vehicle-treated rats, mechanical hyperalgesia was persistent through day 1 after surgery and then gradually returned to the preincisional value. Thirty mg/kg ketamine increased the withdrawal threshold at 2 hours. One hundred mg/kg ketamine caused a motor block at 2 hours and increased the withdrawal threshold at 2.5 and 3 hours. A repeated injection of 30 mg/kg ketamine caused a motor block during the first 2 hours, and reduced hyperalgesia at 3 and 4 hours after the last drug injection. However, there were no significant differences in withdrawal thresholds among the groups at all subsequent times.
CONCLUSIONS
Antinociceptive treatment of systemic ketamine covers the period of surgery and the initial postoperative period by reducing early pain behavior, but had no impact on subsequent measures of hyperalgesia. Therefore, a preemptive effect of systemic ketamine in postoperative pain seems unlikely.

Keyword

Analgesics: ketamine; subcutaneous; Animals: rats; Pain: incisional; preemptive analgesia; postoperative

MeSH Terms

Analgesia*
Animals
Hyperalgesia
Ketamine*
Models, Animal*
Pain, Postoperative
Postoperative Period
Rats*
Wounds and Injuries
Ketamine