Vancomycin remains one of our workhorse antimicrobials for treating infections caused by methicillin-resistant S. aureus
(MRSA). As the incidence of MRSA infections continues to rise AND we are starting to see increasing minimum inhibitory concentrations (MIC) with vancomycin, it is paramount that we optimize its use, starting in the Emergency Department (ED).
The American Society of Health System Pharmacists (ASHP) teamed up with the Infectious Diseases Society of America (IDSA) in 2009 to publish a consensus statement on Vancomycin Therapeutic Monitoring. 1 To prevent the development of bacterial resistance, they recommend using higher doses (15-20 mg/kg) to achieve proper serum trough concentrations.
For patients who begin their care in the ED, it is our responsibility to calculate and order the correct vancomycin dose. Yet all too commonly, a default fixed dose of 1 gm is prescribed instead.
“This flat dosing regimen might result in a delay in achieving therapeutic concentrations and thereby impact eventual outcomes.” 2
Proper Vancomycin Dosing
- 15-20 mg/kg every 8-12 hours in patients with normal renal function 1
- In seriously ill patients (eg, sepsis, meningitis, infective endocarditis) with suspected MRSA infection, a loading dose of 25-30 mg/kg may be considered 3
- Actual body weight should be used
- IDSA recommends a max dose of 2 gm 3
- In adults, we round to the nearest 250 mg increment
|126 kg, MRSA cellulitis → 126 kg * 20 mg/kg = 2,520 mg → Give 2 gm (max dose)|
|70 kg, septic shock → 70 kg * 25 mg/kg = 1,750 mg|
How are we doing?
Short answer: Not great!
Two ED studies were published in 2013 that addressed this very topic.
- A retrospective cohort of 240 random vancomycin doses in the ED found the mean vancomycin dose was 14.6 mg/kg. On the surface, this doesn’t look too bad when comparing it to the recommended 15-20 mg/kg standard. However, only 20% of patients actually received the correct weight-based dose. When broken down by patient weight, the only patients that received the correct dose were those where a 1 gm dose was correct! 2
- A second retrospective cohort study of 4,441 vancomycin doses in the ED found only 22% were correct based on weight using the 15-20 mg/kg standard. Over 70% of patients were underdosed! Not surprisingly, patients underdosed were more often found to have subtherapeutic trough levels as an inpatient. 4
Interestingly, the second study found longer hospital length of stay and higher mortality in patients who received more than 20 mg/kg of vancomycin in the ED. The etiology of this association is unclear, however this may have been due to the phenomenon of sicker patients already being more likely to die. It should be noted that vancomycin guidelines are intended for patients with known or highly suspected MRSA infections. While it is known that patients with methicillin-sensitive staph aureus (MSSA) infections actually do worse when receiving vancomycin compared to beta-lactams, it is challenging to differentiate early in a patient’s ED course with the laboratory testing currently available.
Further, what we do in the ED matters! Most doses of vancomycin in this study were continued unchanged by the inpatient team.
“The fact that most vancomycin dosing was continued unchanged after admission to the hospital, despite being administered outside of recommended range in the majority of patients, again highlights the fact that ED treatment is highly influential on subsequent inpatient care.” 4
How can we do better? [Section updated 11/3/14]
- In the age of Computerized Provider Order Entry (CPOE), we must take advantage of the clinical decision support these tools offer. Instead of having order sentences for 1 gm, replace it with weight-based order sentences. One group found a significant reduction in 1 gm doses ordered after employing this strategy. 5
- A new randomized trial compared ED patients receiving 15 mg/kg initial doses vs. 30 mg/kg. 6 There was a significantly greater proportion of patients reaching target trough levels of 15 mg/L at 12 hours among the patients who received a 30 mg/kg loading dose as compared with a traditional 15 mg/kg dose (34% vs 3%, P < 0.01). This study did not use a max dose of 2 gm. They included patients up to 120 kg who received 3.6 gm loading doses! There was no difference in incidence of nephrotoxicity between the groups.
Take Home Points
- Forget that you ever learned 1 gm of vancomycin is the default dose.
- When vancomycin is indicated in an ED patient, utilize a weight-based dosing strategy of at least 15-20 mg/kg actual body weight to a max of 2 gm (though reference 6 did not use a max dose).
- What we do in the ED matters for long-term outcomes because many doses are continued unchanged by the inpatient team.
- Utilize CPOE tools to guide providers to order vancomycin based on weight.
Original: January 1, 2014
Updated: November 3, 2014