Assessing the accuracy of intracameral antibiotic preparation for use in cataract surgery.

PURPOSE: To evaluate 2 local dilution protocols to assess the accuracy and variability of intracameral antibiotic dosage in cataract surgery.

SETTING

Tennent Institute of Ophthalmology, Glasgow, United Kingdom.

METHODS

Ten ophthalmic operating room nurses from 2 local hospitals participated. Oven-dried analytical grade potassium chloride (KCl) was used as a surrogate for cefuroxime. Solutions intended for intracameral use (1.0 mg in 0.1 mL) were prepared according to the 2 protocols. Twenty samples were obtained for each protocol. Ten analytical chemists also performed both dilutions. Concentrations of KCl in each 0.1 mL sample were analyzed by flame photometry.

RESULTS

Thirty samples were obtained for each protocol. The median dose after dilution was 1.17 mg (range 0.62 to 1.77 mg) for protocol 1 and 2.05 mg (range 0.52 to 7.25 mg) for protocol 2. The median was significantly higher for protocol 2 (P < .001). There was also greater variability with protocol 2.

CONCLUSIONS

This study shows that the mathematical accuracy of a dilution protocol does not ensure dosage accuracy in the clinical scenario. Inadequate mixing in a 1.0 mL syringe was probably responsible for the inaccuracy of protocol 2, indicating that small-volume syringes should not be used for mixing. However, protocol 1 had an acceptable range of variability. Replication of this study could evaluate other protocols and address concerns regarding the accuracy of intracameral antibiotic preparations.