Failure of prefilled thiopental to induce anaesthesia


In response to the letters by Marr et al. [1] and Quinn and Furness [2], we would like to report a failure of prefilled thiopental to induce anaesthesia for a category-1 caesarean section (CS).

In our hospital, we previously experienced incorrect administration of thiopental instead of co-amoxiclav during a CS under spinal anaesthesia. As a result of this, and several similar cases within Northern Ireland, we have changed to prefilled thiopental syringes prepared by our trust's pharmacy, in an attempt to reduce the incidence of this type of anaesthetic drug error.

Syringes containing 500 mg thiopental in 20 ml sterile water are kept refrigerated at 7° C. The manufacturer has performed in-house stability testing to show that after six months the concentration of thiopental does not alter, and recommend reducing the shelf-life to three months in order to reduce contamination errors. Our hospital has further reduced this to one month. In our case, the thiopental syringe was within six days of its expiry date. After 500 mg thiopental had been given to the patient, she remained awake. Propofol was then used immediately to induce anaesthesia before neuromuscular blockade.

After this case our department decided to move away from the traditional induction agent of thiopental and to use propofol for CS. Thiopental continues to remain the preferred induction agent according to 93% of UK consultant obstetric anaesthetists [3]. However, in that survey 58% of respondents stated that they would support a change to propofol, an increase of 32% from the proportion at the Obstetric Anaesthetists’ Association Controversies Meeting in 2003. In addition, trainees still use thiopental in obstetrics but propofol in non-obstetric rapid sequence inductions [4].

The initial drug error resulted in an unnecessary general anaesthetic and therefore we changed our practice aiming to reduce this from recurring. Our implemented change led to a new unforeseen problem.

For most anaesthetists, propofol is a more familiar drug. We feel that it is safer practice to use an agent with which one is most familiar, in an emergency situation. The potential for confusing syringes of induction agent and antibiotic will finally be eliminated with propofol.