A Pre-Anesthesia Dose of Esketamine Decreases Post-Thyroidectomy Pain Outcomes

An esketamine dose of 0.4 mg kg-1 administered prior to thyroidectomy reduces pain sensitivity after the surgical procedure.

A pre-anesthesia injection of esketamine significantly reduces pain sensitivity without increasing adverse events among patients undergoing thyroidectomy, according to study findings published in Pain and Therapy.

For the double-blind, randomized controlled trial, researchers enrolled patients (N=117) undergoing thyroidectomy. Patients were randomly assigned 1:1:1:1 to receive 0.2 mg/kg (n=28), 0.4 mg/kg (n=29), or 0.6 mg/kg (n=30) esketamine or placebo (n=30) delivered by intravenous injection 5 minutes prior to anesthesia induction with remifentanil. The primary outcomes of the study were group differences in mechanical pain thresholds at baseline, 30 minutes, and 6, 24, and 48 hours after surgery.

The study groups comprised patients with a mean [SD] age of 43[10] years, 17.8% to 27.6% were men, they had mean BMIs of 23.6 to 24.9 kg/m2, and 19 to 21 of each group had American Society of Anesthesiologists (ASA) scores of I.

[F]uture research needs to be extended to other populations.

Overall, the group averages for surgery duration were 72.0 to 81.2 minutes, the duration of anesthesia were 84.9 to 95.1 minutes, they stayed in the post-anesthesia care unit for 28.3 to 32.9 minutes (P =.037), they received remifentanil doses of 1.7 to 1.8 mg, and propofol doses of 123.9 to 133.6 mg.

Fewer of the intermediate- and high-dose esketamine groups experienced hyperalgesia on the forearm or around the skin incision at 30 minutes or 6 hours after surgery compared with control individuals.

Numeric rating scale (NRS) scores for pain were significantly lower at 30 minutes among the high-dose esketamine recipients (median, 0) compared with all other groups (median, 2; P =.002) and at 6 hours among high-dose esketamine recipients (median, 0) compared with control individuals or low-dose esketamine recipients (median, 0; P =.006).
No group differences in the need for rescue analgesia (6.7%-20.0%) or receipt of atropine (0.0%-3.4%) or ephedrine (16.7%-26.7%) were observed.

No significant group differences in delirium hallucinations (0.0%-13.3%) or nausea and vomiting (6.9%-13.3%) were observed; however, significantly more high-dose esketamine recipients had hypersecretion of glands compared with control individuals (30.0% vs 6.7%; P =.042), respectively.

These findings may not be generalizable for other nonmechanical pain outcomes.

This study supported the use for esketamine administered 5 minutes prior to anesthesia among patients undergoing thyroidectomy, leading the study authors to conclude, “Intravenous injection of esketamine 0.4 mg kg-1 before anesthesia induction is a suitable dose to reduce pain sensitivity in patients undergoing thyroidectomy without increasing adverse reactions. However, future research needs to be extended to other populations.”


Ren Y-l, Yuan J-j, Xing F, Zhu L-n, Zhang W. Effects of different doses of esketamine on pain sensitivity of patients undergoing thyroidectomy: a randomized controlled trial. Pain Ther. Published online March 18, 2023. doi:10.1007/s40122-023-00488-z