Women report more pain on injection of a precurarization dose of rocuronium: a randomized, prospective, placebo-controlled trial

BACKGROUND: The purpose of this study was to investigate whether gender influences the perception of pain on injection of rocuronium. METHODS: In this prospective, placebo-controlled trial 120 patients were randomized into four groups to receive rocuronium 0.03 mg kg(-1) (40 female and 40 male patients) or saline (20 female and 20 male patients). The incidence and severity of the injection pain after administration of the study drug was compared between female and male patients using a numerical rating scale (0-10). Signs of local irritation, i.e. erythema and thrombophlebitis, were assessed up to 48 h after surgery. RESULTS: In 26 (32.5%) of the 80 patients receiving rocuronium, pain on injection was observed. This occurred significantly more frequently in the female compared with male patients: 18 (45%) vs. eight (20%), respectively (P = 0.032). The severity was more pronounced in the women than in the men (P = 0.020). The incidence of the rocuronium-associated pain was significantly increased compared with the Saline groups (P < 0.001). After surgery no patient complained of any residual pain and no local signs were observed in any patient during the study period. CONCLUSIONS: Women experienced more pain on injection of rocuronium than men, moreover this is an additional evidence for gender-related differences in pain perception. When rocuronium is used as a precurarization agent, an analgesic pretreatment (e.g. opioids) should be considered, especially for female patients.