Comparison of Propofol with Lidocaine Pretreatment Versus Propofol Formulated with Long- and Medium-Chain Triglycerides or Confounding Effect of Tourniquet

Abstract

In Response: We would like to thank Drs. Eghtesadi-Araghi and Marashi for their interest in our randomized clinical trial. They have raised some concerns regarding tourniquet use and the potential for an interaction between ischemia/reperfusion injury and the pain triggered by the injection of propofol. First, the tourniquet used on the forearm of our patients in this trial was not a “surgical tourniquet” whereby two cuffs are inflated to a pressure of 300 mm Hg to prevent arterial flow to provide a bloodless surgical field during microsurgery, to minimize blood loss during orthopedic surgery, or to perform distal limb anesthesia with prilocaine. As is our routine practice when using standard propofol with pretreatment with lidocaine and as has been described by others (1), we used a rubber tourniquet that was held in place on the forearm for <1 min. It is most unlikely that any ischemia would result from such a procedure with low compression applied for a short time. Therefore, we do not consider that neutrophil-mediated endothelial cytotoxicity and activation or generation of free radicals and kinines provide an explanation for the increased pain observed after injection of the long- and medium-chain triglyceride propofol. Furthermore, both formulations of propofol were administered with a rubber tourniquet, so if the tourniquet were to have a confounding effect, this would have been seen in both groups. Although the solvent might be key in producing the pain (2), it is most unlikely that the different lipid contents in the two propofol formulations react in such a different way to a 30-s tourniquet application as to result in an exaggerated free radicals and cytokines release with the long- and medium-chain triglyceride formulation. Finally, a recent randomized trial comparing long- and medium-chain triglycerides with standard propofol mixed with lidocaine without using a tourniquet also described a trend towards more pain in patients receiving the long- and medium-chain triglyceride formulation (3). E. Schaub, MD C. Kern, MD Ruth Landau, MD Service d’ Anesthesiologie Hopitaux Universitaires de Geneve Geneva, Switzerland [email protected]