Some patients benefit from vancomycin blood level monitoring. The need to synchronize the blood test with drug administration adds steps to an already-complex medication process, requires interdepartmental coordination (nursing, pharmacy and phlebotomy) and multiplies the likelihood of problems compared to routine antibiotic administration. Indeed, review of CHPSO’s event reports database shows recurring errors with vancomycin monitoring.
Vancomycin accounted for one-fourth of the medication timing errors reported to CHPSO. Over half the facilities reviewed had these errors and we have found about 300 events so far. The reported events generally fall into one of the following categories:
trough drawn while vancomycin was infusing,
trough drawn 30 minutes after administration of vancomycin,
trough drawn prior to next dose after a missed dose,
administration delay due to delay in obtaining trough results, and
administration delay due to delay in blood draw.
The first three are monitoring errors, while the last two are administration timeliness errors.
Though not reflected in these numbers, trough levels drawn too early commonly occur. A retrospective study showed this error in 40 percent of all trough level tests (Morrison). We believe that this particular error is less likely to be identified contemporaneously than the above five, explaining the dearth of incident reports we received for early trough level draws.
One of the most powerful ways to make a complex process more reliable is to simplify it. In the case of vancomycin administration, a good start is to eliminate monitoring over-use. Following the consensus recommendations for therapeutic monitoring of vancomycin in adult patients (Rybak) may reduce monitoring and, consequently, errors.
According to the consensus recommendations, monitoring is indicated in patients:
receiving aggressive dosing (i.e., to achieve sustained trough levels of 15-20 mg/L),
at high risk of nephrotoxicity,
with unstable renal function, or
receiving more than 3-5 days of treatment.
The consensus recommendations also state that frequent monitoring (more than one trough before the fourth dose) for short course or lower intensity dosing is not recommended. All patients on prolonged courses of vancomycin (exceeding three to five days) should have at least one steady-state trough concentration obtained no earlier than at steady state (just before the fourth dose) and then repeated as deemed clinically appropriate.
Other steps should be taken to improve the coordination of lab draw and medication administration processes. This may also be a good time to evaluate the phlebotomy process throughout the hospital. Redesigning the phlebotomy process system-wide may provide benefit not only for vancomycin testing but for other tests as well, as collection timing issues are one of the most common preanalytic-phase laboratory testing errors (Wagar).
As with any complex systems issue, weak interventions such as education or reminders are unlikely to provide much benefit. Several attempts using a weak intervention dramatically increased nursing knowledge without any gains in trough timing accuracy (Coleman, Melanson).
Rybak M, Lomaestro B, Rotschafer JC, et al. Therapeutic monitoring of vancomycin in adult patients: a consensus review of the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, and the Society of Infectious Diseases Pharmacists. Am. J. Health. Syst. Pharm. 2009;66(1):82-98. http://www.ajhp.org/content/66/1/82.full.pdf+html