Antibiotic administration in ITU: Are we throwing away that which we hold so dear?

Timely antibiotics decrease mortality in patients who are critically unwell with bacterial infections. ¹ Adequate dosing, so that antibiotic concentration exceeds the minimum inhibitory concentration for the treated pathogen, is likely equally important.

An observation in our unit made us concerned that we may not be administering the intended doses of antibiotics to our patients due to an oversight that results in unintentionally discarding antibiotics. On informal discussion with colleagues at a regional meeting, we realised that our mistake is being replicated in other units. Therefore, we felt it was important to raise the issue more widely.

It has become common practice in intensive care units to administer antibiotics using a mini bag of 50 to 100 ml of carrier fluid and a separate, disposable giving set. This allows delivery devices with pre-programmed ‘guardrails’ to be used and facilitates audit of drug delivery. Once the mini bag is empty, the bag and giving set are discarded. The giving set is not flushed through and hence the carrier fluid with antibiotics in the giving set, equivalent to the priming volume, is thrown away.

The residual volume of fluid held within a giving set is obviously variable depending on the length of tubing and the filling of the air trap, but it is in the region of 17 ml for a gravity administration system (CareFusion 41173E-0006, CareFusion, UK) and 22 ml for a pump administration set (Alaris® GW primary infusion set, CareFusion, UK). This would result in a potentially significant proportion of a 50 ml antibiotic solution not being administered, potentially resulting in underdosing and treatment failure.

We have therefore changed practice to flush through our antibiotic giving sets to ensure delivery of intended doses of antibiotics using a burette system. We plan to change to delivering antibiotics using syringe drivers and narrow bore IV extensions with smaller priming volumes (1.4 ml; G40020B Extension set, CareFusion, UK).

As we had overlooked this potentially harmful practice locally, we felt it was possible that others might be doing the same and felt that raising the issue was therefore important.