Introduction: Propofol, a commonly used intravenous anesthetic induction agent, frequently produces pain on injection, with an incidence ranging from 28% to 91%. This study aimed to compare the effect of low-dose ketamine and a pressure vibration mechanical device with placebo in reducing pain during propofol injection in patients undergoing elective surgery.
Methods: In this randomized, double-blind, placebo-controlled trial, 300 adults were allocated to pressure vibration (Group V), low-dose ketamine (Group K), or saline placebo (Group P); 275 patients completed the study and were analyzed (92, 91, and 92 patients, respectively). Group P received 5 mL 0.9% saline, Group K ketamine 50 µg/kg diluted in 5 mL saline, and Group V saline with an activated pressure vibration device applied proximal to the intravenous cannula, each administered over 1 min. Propofol 2 mg/kg was infused, with the first 25% delivered at 600 mL/hour, and pain assessed using the McCrirrick and Hunter verbal rating score. The primary outcome was pain on propofol injection. Continuous variables were analyzed using one-way analysis of variance or Kruskal-Wallis tests, categorical variables with χ² tests, with Bonferroni correction applied for multiple primary outcome comparisons.
Results: Among 275 analyzed patients, the incidence of no pain was highest in the pressure vibration device group 51.1%; 95% CI 42.4% to 59.8% compared with placebo 30.4%; 95% CI 21.0% to 39.8% and ketamine 33.0%; 95% CI 23.3% to 42.6%; (p=0.001). Severe pain was more frequent in the placebo group (18.5%; 95% CI 10.5% to 26.4%) than in the ketamine (5.5%; 95% CI 0.8% to 10.2%) and vibration groups (4.3%; 95% CI 0.2% to 8.5%; (p=0.001). Recall of injection pain at 1 week was significantly higher with placebo compared with ketamine and vibration device (55.4%, 37.4%, and 26.1%, respectively; p<0.001). Hemodynamic variables and adverse events were comparable across groups.
Conclusion: The pressure vibration mechanical device significantly reduced the incidence and severity of propofol injection pain compared with placebo and was at least as effective as low-dose ketamine. Pain recall at 1 week was higher with placebo. This device provides an effective, reusable, non-pharmacological alternative without drug-related adverse effects.
Trial registration number: CTRI/2022/12/048300.
Keywords: Acute Pain; Pain Management; Pain Perception; Pharmacology.
© American Society of Regional Anesthesia & Pain Medicine 2026. Re-use permitted under CC BY-NC. No commercial re-use. Published by BMJ Group.