Summary Eight modes of administration of propofol were assessed in order to minimise the pain of injection. An intravenous bolus injection in the antecubital fossa was the only approach that caused no pain. When administered intravenously in the dorsum of the hand the pain score and the number of patients who experienced pain was reduced significantly by mixing the agent with lignocaine when compared with a bolus injection. Slowing the speed of injection caused the greatest discomfort. An indirect biochemical mechanism for the pain is proposed.

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This study was designed to determine the effects of a rapid bolus dose of atracurium 0.6 mg kg-1 on arterial pressure, heart rate and plasma histamine concentration (n = 9), and to compare these values with those obtained by (a) giving the same dose of atracurium slowly (over 75 s) (n = 9), or (b) pre-treating with H1- and H2- antagonists (n = 9). The rapid (5-s) bolus dose of atracurium i.v. resulted in a significant increase in plasma histamine concentration (P less than 0.05) and was associated with a decrease in mean arterial pressure and an increase in heart rate. Administering the same dose of atracurium slowly (over 75 s) prevented the increase in plasma histamine concentration, and abolished the subsequent haemodynamic response. Pretreatment with cimetidine 4 mg kg-1 i.v. and chlorpheniramine 0.1 mg kg-1 i.v. abolished the haemodynamic response despite a moderate increase in histamine concentration (0.1 greater than P greater than 0.05).

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