Pain on injection of propofol: propofol LCT vs propofol MCT/LCT with or without lidocaine pretreatment.

BACKGROUND: Pain on injection was a disadvantage of propofol long-chain triglyceride (LCT) and reduces patient satisfaction. Based on a systematic review, the recommended method to attenuate this pain was a previous administration of lidocaine under tourniquet for 30-120 seconds before injection of propofol (pretreatment of lidocaine). Recently, propofol medium-chain triglyceride/long-chain triglyceride (MCT/LCT) emulsion was proposed for its ability to decrease pain on injection. The authors conducted a double-blind randomized controlled trial to compare the incidence and severity of pain on injection between the new propofol MCT/LCT and the propofol LCT with and without lidocaine pretreatment.

MATERIAL AND METHOD: 360 adult patients with ASA physical status I-III who underwent general anesthesia were assigned into 4 groups by computer-generated randomization; Group I - pretreatment of lidocaine 1% and propofol LCT Group I - pretreatment oflidocaine 1% and propofol MCT/LCT Group III - pretreatment of saline and propofol MCT/LCT and Group IV- pretreatment of saline and propofol LCT mixed with lidocaine 1%. All groups received pretreatment under tourniquet for 60 seconds. Evaluators who were blinded to the injected drugs recorded pain intensity (none, mild, moderate and severe) after the first 30% of total induction dose ofpropofol was injected at a rate of 1 ml/s by questioning patients. Data was analyzed by using Kruskal-Wallis testfor ordinal data. Post hoc analysis was performed by using the Mann-Whitney U-test with Bonferroni's correction on pairwise comparisons and was considered significant with p value of less than 0.05.

RESULTS: Patients in an individual group had insignificant differences in their demographic data. The incidences of pain in Group I, II, III and IV were 61.1%, 46.7%, 62.2% and 55.6% respectively with an average incidence of 56% (p = 0.006). There were 15.6%, 5.6%, 23.3% and 24.4% of patients in Group I, II, III and IV who rated pain intensity as severe. Pain on injection of propofol MCT/LCT with lidocaine pretreatment was less than propofol MCT/LCT alone (p = 0.001).

CONCLUSION: The incidence of pain on injection of propofol MCT/LCT was not different from that caused by propofol LCT with pretreatment of lidocaine and the intensity of pain on propofol MCT/LCT injection decreased significantly when using lidocaine pretreatment. Therefore, the authors could conclude that an injection of new propofol MCT/LCT solution was an alternative in reducing pain sensation to propofol LCT with pretreatment of lidocaine. Additionally, pain of propofol MCT/LCT injection could be alleviated by pretreatment of lidocaine with a 60 seconds tourniquet time before the injection ofpropofol.