Quality control and stability of ketamine, remifentanil, and sufentanil syringes in a pediatric operating theatre.
This paper looks at whether or not syringes of ketamine and remifentanil (and sufentanil) are chemically stable once diluted and if degradation leads to concentration error. It also looks at drug concentration errors due to serially diluted syringes. They have a system whereby pharmacy or nurses prepare a “stock” (master) syringe of more concentrated drug in the morning, which is then decanted +/- further diluted by the anaesthetists as needed. This is an unfamiliar system for anaesthetists in Australia.
Overall, they found degradation related concentration errors (+/-10% acceptability range) in the “stock” (single initial dilution syringe) of 10% and compounding related concentration errors in serially diluted syringes higher at 20%.
KETAMINE: This study generally agrees with previous evidence that ketamine is very stable when diluted (stable for >1yr at 1mg/ml in ambient temp out of light). Degradation errors were found to be slightly higher over the course of a day, but data suggested adequate stability for one day (8am – 5pm) at ambient temperature.
REMIFENTANIL: This study also agrees with previous evidence (although a less studied drug than ketamine) that remifentanil is susceptible to chemical hydrolysis and the degradation error is greatest at dilute concentrations:
- 4mcg/ml was too unstable to be used
- 5mcg/ml is no longer stable after 1hr
- 10, 20 and 50mcg/ml are stable for a day (although 10 slightly less so than 50)
Take home message
Serially diluting syringes increases the risk of concentration error, probably due to a number of both procedural and human factors (syringe size, person diluting, distraction).
Remifentanil degrades quickly and should be diluted just before use, especially if used in low concentrations. Ketamine is stable at any concentration for as long as you are likely to need it.
Reviewed by: Rachael Chapman