Pain during injection of vecuronium

A I"/, solution of thiopentone to induce anaesthesia in the elderly. rather than the 2.5% solution normally used, is in my opinion desirable. Davenport suggests 0.75% in saline.] The elderly necd a stnallcr dose of intravenous induction agenl, given much more slowly than in younger The induction dose of thiopentone drops at the rate of I m g k g for cvcry d ~ c a d c . ~ primarily because the initial distribution volume increases the time from injection to inc1uction.j I t has bccn rccomincndcd that a small bolus should be given. and its effect watched for an appropriate lime, say 30-60 scconds. Thc rangc rcconnncndcd for the elderly is 1.26-3.45 mg/kg and the average time to loss of consciousness is 48 seconds ( S D 2.4). Dilution of thiopentone to 1 % increases the safety of this technique. Onc can thcn titratc thc cffcct of a dose bctter than with the normal low volume. An anaesthetist with little experience of the elderly would be much less likely to give an ovcrdosc; i t is also casicr to remember a concentration of 10 mg/kg and the use of a 5 or 10 ml syringe makes overdosage easier to avoid. 2.5% thiopentone has an osinolality (480-500 mosm/kg) higher than lo/, in saline (370 mosmikg) or 1 % in water (188-195 mosmikg): this should reduce local reactions if there is extravasation which is far more likcly with clderly, fragile veins. A 1 %, solution in watcr could howeveicausc hacmolysis.