Tobramycin administration and blood sampling through a dual-lumen peripheral intravenous catheter

The objective of this study was to determine if a peripheral dual-lumen catheter could be used for accurate tobramycin blood concentration measurement when drug administration and blood sampling were undertaken through separate lumens of the catheter. Eleven adult volunteers received tobramycin 1.5 mg/kg iv infused over 30 minutes through the distal lumen of the dual-lumen catheter every eight hours for two doses. Multiple blood samples were obtained concurrently from the proximal lumen of the catheter and a single-lumen catheter in the contralateral arm after each dose. Blood samples were also obtained through the distal lumen before and 30 minutes after the end of the infusion. Accurate blood samples were obtainable through the dual-lumen catheter in only 5 of 11 subjects due to either infiltration or difficulties in catheter placement. In the subjects from whom accurate blood samples were obtained, approximately 20 minutes postinfusion was the amount of time required before measured tobramycin serum concentrations were similar between the arm in which the drug was infused (site of the dual-lumen catheter) and the contralateral arm. At standard times for obtainment of trough (just prior to the infusion) and peak (30 minutes after the end of a 30-minute infusion) tobramycin serum concentrations from the proximal lumen of the dual-lumen catheter were numerically similar to those obtained from the contralateral arm. This preliminary study indicates that the dual-lumen catheter provides accurate aminoglycoside concentrations when patent relative to blood withdrawal and if peak blood samples are obtained at least 30 minutes postinfusion through the recommended lumen. However, further study in a larger number of subjects is required before routine use of this device can be recommended.