Sustained intravascular exposure to propofol does not prolong pain at the site of injection

Background Pain at the site of intravenous injection of propofol is a common clinical finding. This double-blind, randomized cross-over study was designed to evaluate whether venous occlusion applied during injection of a low dose of propofol reduces the intensity of pain at the site of injection compared with no occlusion. Methods Bilateral 0.5-ml injections of an emulsion containing 10 mg/ml of propofol were given over 30 s in 75 adult surgical patients. Each patient was given one injection with and one without 60-s occlusion of the cannulated vein with a 10-min interval, and asked to score the maximal pain intensity on a visual analogue scale (VAS). Results The maximal pain intensity [median (25th percentile; 75th percentile), range] at the site of injection was 0.5 (0; 3.5), 0-8.0 VAS units with venous occlusion and 0.5 (0; 1.4), 0-6.0 VAS units without occlusion (P = 0.042). Pain was first reported within 20 s regardless of the study regimen and was not prolonged by local venous occlusion. Conclusions Venous occlusion augments pain intensity at the site of propofol injection without prolonging pain, implying that propofol-induced pain is determined more by the blood concentration than by the duration of intravascular exposure. The low intensity of pain induced by low-dose propofol and the fading of pain despite sustained exposure suggest that initial low-dose administration of propofol should be evaluated for the attenuation of local pain induced by higher intravenous doses of propofol.