Escalating Ketamine Doses and Pre-emption

group receiving one injection (25 mg) of ketamine (K1) intramuscularly (IM) at 3-4 hours before surgery or placebo (saline 0.9%, NS)

ketamine at 11-12 hours (10 mg) and 3-4 hours (25 mg) before surgery (K2), with a corresponding NS group

ketamine injected IM 17-18, 11-12, and 3-4 hours before surgery (5, 10 and 25 mg, respectively) (K3), and the second group received NS