J SORARU1, N BOUDVILLE1
1Sir Charles Gairdner Hospital, Perth ,Western Australia
Aim: To determine the frequency of elevated gentamicin levels in patients receiving gentamicin/citrate catheter locks for infection prophylaxis of tunnelled catheters, and to determine if the benefit of testing gentamicin levels warrants ongoing monitoring.
Background: Tunnelled catheters are commonly used for haemodialysis, with catheter survival limited by catheter related infections. Data shows gentamicin/citrate catheter locks reduce catheter related infection compared to standard heparin locks, with gentamicin/citrate locks protocol at Sir Charles Gairdner Hospital. The concern is possible chronic aminoglycoside exposure and ototoxicity, and patients in our centre undergo routine gentamicin level testing to screen for elevated levels. This is balanced with the financial burden of frequent testing.
Methods: Measurements for 724 gentamicin levels in 149 patients undergoing haemodialysis via tunnelled catheter between 1st January 2013 and 21st September 2015 were correlated with patient records. Ten levels from nine patients who received intravenous or intraperitoneal gentamicin within the prior three weeks were excluded. Gentamicin levels between 2-8mg/L were considered undesirable, with levels >8mg/L considered to be toxic.
Results: Of the samples, 97.7% had levels less than 2mg/L, with 1.7% having levels between 2-8mg/L. Only 0.6% of the samples were considered to be in the toxic range. There were four levels greater than 8mg/L, with three of these levels having repeat measurements on the same day <0.3mg/L, suggesting sampling error. Excluding the three data points, the total number of samples >8mg/L is 0.1%.
Conclusions: After the exclusion of serum gentamicin levels taken in the context of therapeutic gentamicin use and sampling error, the number of samples with levels in the toxic range is very small. Given the cost-benefit of testing gentamicin levels, cessation of screening is warranted.