Vancomycin therapeutic monitoring in the intensive care setting: Optimizing treatment and reducing adverse events

Background: Vancomycin is an antibiotic used to treat severe infections caused by resistant gram positive organisms. It can be failure in treating these infections because of bacterial resistance and also its low tissue concentration.  Higher concentrations of this antibiotic could provide a better response and reduce the emergence of resistance. At the same time, may be related to adverse events such as nephrotoxicity and ototoxicity. Vancomycin Therapeutic Monitoring (VTM) done properly can promote the efficacy and a safe prescription of this drug.

Objective: Compare the use of the VTM previously to the implementation of a controlled protocol (1^st period), with 2 other distinct periods. At the 2^nd period we used a VTM protocol with a 5-15 ug/dL vancomycin serum level target, and at the 3^rd period a 10-20 ug/dL vancomycin serum level target.

Methods: We compared among the three analyzed periods: Days of vancomycin used, grams of vancomycin used, number of blood collection for vancomycins per patient, number of collected blood failures per patient, adequated blood collections (i.e. performed until 2 hours before the next dose) and adequated therapeutic targets, according to the analyzed period. We also studied patients with toxic levels (> 30 ug/dL) and with under dosing (< 5 ug/dL). Cases of osteomyelitis and endocarditis were not included in this study and the 3^rd period adjustment was conducted through a serum level greater than 10 ug/dL by some evidence to avoid bacterial resistance with these vancomycin levels.

Results: The results can be viewed in table 1.

Table 1: Comparison of the three study periods.

Indicators	1st period (n=47) Previously to VTM protocol                   (5-15ug/dL)	2nd period (n=55) VTM protocol          (5-15ug/dL)	3rd period (n=55) VTM protocol        (10-20ug/dL)
Consumption of vancomycin
Days used per patient	10.3	7.8	8.1
Grams used per patient	11.2	6.8	9.2
Serum levels of vancomycin
Nº of blood collections per patient	5.0	7.0	7.1
Nº of collected blood failures per patient	4.7	0.6	0.05
Adequated blood collections (performed until 2 hours before the next dose)	22%	84%	87%
Adequated therapeutic targets	67.4%	72.5%	68.5%
Adverse events
Patients with toxic levels (>30 ug/dL)	14.9%	3.6%	12.7%
Patients with under dosing (<5 ug/dL)	21.3%	7.3%	9.1%

Conclusions: The elaboration of a VTM protocol, training staff and engagement of laboratory to speed up the liberation of results may decrease the number of collection´s failure, increase the number of adequated blood collections and reduce the number of patients receiving suboptimal dose. Toxic doses of vancomycin were higher in the 3^rd period compared to the 2^nd, it could be related to a desired high target level.