Background: Post-tonsillectomy pain is often severe and usually prevents patients from routine eating and drinking. A new option for reducing postoperative pain is "preemptive analgesia", the pre-, intra- or post-operative administration of analgesic agents. Ketamine, an N-methyl D-aspartate receptor antagonist, has recently received attention for this aim. Herein, we study the effect of submucosal injection of ketamine in the tonsillar bed for the reduction of post-tonsillectomy pain.

Methods: In this double-blind clinical trial, three groups of patients underwent infiltration of 0.5mg/kg ketamine, 1mg/kg ketamine or normal saline in their tonsillar bed. Age, sex and weight of patients, duration of surgery, systolic and diastolic blood pressure (before and after surgery), volume of blood loss, reoccurrence of bleeding, time to initiation of oral intake, nausea, vomiting, pain score and dysphasia were recorded in information sheet. Data analysis was performed by one-way ANOVA and chi squared tests, with significance at a P value of <0.5.

Results: There is no significant difference between the three groups with regard to age, sex, weight, duration of surgery, blood pressure (before surgery), volume of blood loss, nausea and vomiting. However, for the ketamine groups, pain score, dysphasia, need for opioid administration and time to initiation of oral intake is significantly lower (P<0.00). Reoccurrence of bleeding was observed in one patient in the lower-dose ketamine group, which is not statistically significant. The effectiveness of the two doses of ketamine is similar, with no statistical difference between the two groups (P=0.84).

Conclusions: This study demonstrated that a submucosal injection of ketamine into the tonsillar bed preoperatively is a safe option for reducing post-tonsillectomy pain, dysphasia, need for opioid and time to initiation of oral intake, without increasing the risk of excessive bleeding, reoccurrence of bleeding, nausea and vomiting.