Pre‐filled drugs for the obstetric theatre

We read with interest the two letters (Cupitt & Dunkley. Anaesthesia 2000; 55: 721. Calow. Anaesthesia 2000; 55: 1213–14) regarding the preparation of anaesthetic and emergency drugs in the obstetric theatre. Anaesthetists undoubtedly play a crucial role in obstetric practice. Emergency is more of a certainty in obstetrics than other specialties. Time is critical in such situations because it involves not only saving the baby but, sometimes, also the mother. As per the Royal College of Obstetricians and Gynaecologists guidelines, ideal ‘decision to delivery time’ should be less than 30 min [1]. Sometimes this is practically difficult to achieve. So, measures to reduce the delay in delivering the baby are always welcome. One of them is keeping the anaesthetic and resuscitative drugs, reconstituted or diluted, ready in the obstetric theatre. This practice is well known not only in UK, but also in other countries [2, 3]. Normally, the drugs are kept in the fridge and, if not used, discarded after elapse of an arbitrary time [3]. The anxieties of the authors of both letters regarding this practice are genuine and well founded. Their concerns were lack of sterility, complexity with the risk of preparation error, possibility of tampering by a third party and poor standards of labelling and storage. As anaesthetists with an interest in obstetric anaesthesia, we too wanted to look into this practice in our unit. Before embarking on an audit, we wrote to the manufacturers of the commonly used anaesthetic and emergency drugs in the obstetric theatre: Alliance Pharmaceuticals (syntocinon), Antigen Pharmaceuticals (atropine and succinylcholine), Glaxo Wellcome (atracurium), Martindale (ephedrine) and Rhone Poulenc Rorer (thiopental) and asked their opinion on this practice. Not surprisingly, none of the manufacturers recommend the practice, but did not suggest alternatives. The evidence in the literature regarding the sterility and microbial contamination of the stored anaesthetic drugs is conflicting. Of all the drugs, thiopental has some antiseptic-like properties (a high alkaline pH). Driver et al. found no evidence of bacterial or fungal contamination of the commonly used anaesthetic and resuscitative drugs – thiopental, succinylcholine, ephedrine, atropine, lidocaine and oxytocin – when they are stored for 8 days [2]. They even advise storing the drugs for a longer period than the manufacturers' recommendation. However, in another study, Magee et al. found bacterial contamination in eight out of 40 syringes [4]. The major difference between these studies was that Driver et al. took more rigorous and meticulous control over filtering and culturing of the samples than Magee et al. Another problem of storing drawn-up drugs for long periods is loss of potency and stability. A study by Haws et al. showed that thiopental is chemically stable for more than 7 days after preparation [5]. Schmutz et al. found that batches of succinylcholine chloride injection prepared by the hospital pharmacy were stable for up to 5 months when kept in the fridge [6]. We were unable to find any published data on the stability of ephedrine after dilution. The manufacturer (Martindale) also could not supply any relevant studies regarding this. When stored for long periods, adsorption of the drug to the plastic syringes could potentially decrease the availability of the parent drug. Pramer et al. found that atracurium besylate could be stored in the syringes undiluted for up to 7 days [7]. After this period, drug concentration falls below the acceptable 90% level; Lewis et al. showed that the concentration of atropine falls profoundly when stored in glass or plastic syringes [8]; but in unpublished data, Driver et al. found that atropine can be safely stored for up to 8 days without loss of potency. Stability data on syntocinon could not be found in the literature. Another major concern is complexity of preparation and risk of preparation or administration error. Usually, the person who uses or discards the previous batch draws up the next batch of drugs. Preparing drugs in the middle of the night after three consecutive Caesarean sections is not ideal. Tiredness can easily lead to error. The more the number of drugs drawn up, the greater the risk of preparation or administration error. There has been a critical incident in one of the units nearby (unpublished) where the anaesthetist gave succinylcholine instead of syntocinon after delivery of the baby. In that unit, two syringes of succinylcholine along with one syringe of thiopental, atracurium, syntocinon, atropine and ephedrine are drawn up as routine. Cost is a definite concern in the present climate. In our audit, we found that 63% of unused drugs were discarded. Thiopental, succinylcholine, atropine and ephedrine were the most frequently drawn-up drugs in our unit. The commonest reason for discarding drawn-up drugs was the time interval (more than 24 h). This wastage costs £1270 in a year. After the audit and careful literature review, we feel that we need only thiopental and succinylcholine to start an emergency Caesarean section. Both these drugs could be prepared by the pharmacy in a sealed syringe and kept for a week. The unused drugs can be returned to the pharmacy after 5 days and sent to other theatres to be used for routine surgery. This may reduce the potential risk of a preparation error, third-party tampering and the cost. An atropine minijet, ampoules of muscle relaxant, ephedrine and syntocinon could be left in the tray to save time. Aurum Pharmaceuticals Limited produces prefilled syringes of ephedrine (3 mg.ml−1) with a shelf life of 2 years, if stored below 25 °C. As this is expensive, this should be used only in the ‘genuine crash section’, which are few and far between. Departments should make local policies to increase the safety of this practice. A reasonable balance should be struck between risk and benefit. An improvement in our practice should be made without patient safety.