To the Editor:

We have read an article written by Kwon et al. with great interest [1]. It is a welcome investigation which evaluated the effect of the intraoperative dexmedetomidine (DEX) on the incidence and severity of catheter-related bladder discomfort (CRBD) after nonurologic surgery. We agree with their conclusion that DEX may have benefits in preventing CRBD after lumbar microdiscectomy. However, we have a question regarding the blind method.

In this article, the author stated that DEX was infused at a loading dose of 1 µg/kg over 10 min, followed by a continuous infusion of 0.3–0.5 µg/ kg/h, the dose of which is adjusted by the operator based on blood pressure, heart rate, and BIS values in group D (experimental group), while an identical volume of 0.9% saline was infused in the same manner in the group C (control group). According to the author’s description, the operator was aware of both groups for each individual. In other words, the operator was not blinded, which may cause the possibility of observation bias. We suggest that the study drugs (DEX 200 µg/2 mL and normal saline 2 mL) should be diluted into the same syringe with normal saline to 50 mL, and infused at a loading rate of 0.25 mL/kg over 10 min, followed by a continuous infusion of 0.075–0.125 mL/kg/h according to the study of Su et al [2], but not at the dose of DEX (µg/kg/h), so that the operator is blinded to the group allocation.