Influence of Temperature and pH Changes on Propofol Injection Pain.

Objective: Propofol has been widely used for anaesthesiology, although about 60%-70% of patients experience pain on injection. The aim of our study was to compare two storage patterns of propofol, namely room temperature versus refrigeration, in terms of their effect on incidence and severity of pain caused by its injection. Methods: Two hundred patients referred to gastrointestinal or urologic surgery with general anaesthesiology were included in a prospective randomized, double-blind study. After routine monitoring, 5 mL of propofol at room temperature and 5 mL of propofol kept in the fridge was administered within 10 seconds to patients in Group 1 and Group 2, respectively. An investigator assessed pain intensity. Propofol temperature-pH were measured by another researcher. Results: The overall incidence of pain on injection of propofol was 73.7% in Group 1, and 83.2% in Group 2. There was no significant difference between groups regarding the incidence of pain. There was a significant difference between groups in terms of pain severity based on a 6-point verbal rating scale. While the median VRS value for Group 1 was 2, it was 3 in Group 2. Conclusion: Cold application has a local anesthetic effect of its own. In the present study it was observed that cold application of propofol caused pain more frequently, although it was statistically not significant; moreover, it was found that it statistically significantly increased the severity of pain. These findings indicate that propofol should be kept at room temperature instead of in the refrigerator in order to reduce injection pain. [ABSTRACT FROM AUTHOR]