Effect of communication on pain during intravenous cannulation: a randomized controlled trial

Background: Clinicians frequently warn patients of discomfort before potentially painful procedures, despite the lack of evidence that such communications are helpful. We aimed to compare two communications (one with, and the other without, a warning of a 'sting') immediately before i.v. cannulation in order to measure differences in perceived pain by patients during the procedure. Methods: Randomly assigned patients awaiting elective surgery received a communication immediately before i.v. cannulation consisting of either 'I am going to apply the tourniquet and insert the needle in a few moments. It's a sharp scratch and it may sting a little' (Group S) or 'I am going to apply the tourniquet on the arm. As I do this many people find the arm becomes heavy, numb and tingly. This allows the drip to be placed more comfortably' (Group NS). Cannulation pain was measured by a 0-10 verbal numerical rating score (VNRS) and five-point Likert scale. Results: Of 101 participants, 49 were allocated to Group S and 52 to Group NS. Median VNRS pain scores with inter-quartile ranges (IQR) were 1 and 2, respectively, for both groups. Median Likert scores were 3 in Group S and 2 in Group NS with an IQR of 1 for both groups (P = 0.13). Six participants vocalized pain in Group S and none in Group NS (P = 0.01). Three participants withdrew their arm spontaneously in Group S and none in Group NS (P = 0.11). Conclusions: Warning patients of a 'sting' before i.v. cannulation may not be helpful.