The following Clinical Perspective is contributed by Dr Tom Peck, Consultant Anaesthetist, Hampshire Hospitals NHS Foundation Trust
The language of the TCI pump at induction is not the language of most anaesthetists and often not the language of patients towards the extremes of age, weight, co-morbidities and anxiety.
Despite the advantages of TCI / TIVA, its widespread adoption has not yet been fully realised. One of the reasons for this is the universal requirement of TCI pumps for a (plasma or effect site) target concentration of propofol at induction. However for most anaesthetists and particularly those learning TCI / TIVA this is not the language with which they are most familiar. We have become fixated on the pharmacokinetics and lost sight of the pharmacodynamics. The language of dose, is of course their native language, and because a ‘translation’ is not immediately to hand (dose not being shown on the induction screen) anaesthetists resort to work arounds, e.g. seeing how far the plunger of the syringe has moved. A “pocket guide” – showing a real time administered dose – would be helpful, but of course changing the input language would be better still. Having the option to specify an actual dose (that could be added to), and then proceed seamlessly into a TCI mode (taking into account the initial dose) would represent the best of both worlds. Given that the main differences between the commercially available algorithms are seen during induction, it can now be argued that there is need for only one ! The anaesthetic world is a paradox of choice and protocol, we have choices over drugs, equipment and technique yet we know that limiting these choices improves safety – who would choose to have different anaesthetic machines across a suite of operating theatres or choose different techniques for a list of the same procedures? Selecting Schnider instead of Marsh by mistake results in a smaller peri-induction dose for the same target concentration, a difference that increases with increasing BMI. Let’s regain control of induction across the board by having an option to speak in the common language of dose, and then move to all the benefits of TCI for maintenance.