Gesundheit19 November, 2021

# To Bayesian or not to Bayesian? The roadmap from trough to AUC dosing

Shifting from trough-based dosing to AUC-based dosing for vancomycin has numerous clinical and operational benefits.

## What is the difference between first-order equations and Bayesian dosing?

### First-order equations

First-order equations also called the trapezoidal method, involve a series of calculations performed manually and require input into a calculator or homegrown Excel spreadsheet. This method requires two levels to be obtained during the dosing interval. Typically, the first level is a post-infusion peak, and the second level is a trough level. These levels have to be obtained at a steady state. In first-order equations, one challenge commonly faced, is that it can take a while before you can actually get the level for some patients. This delay can result in a delay in appropriate therapy. The other caveat is that the process is extremely static - it represents a patient's pharmacokinetic (PK) profile at that point in time. For example, in the case of a patient with changing renal function, you have to redraw post-infusion, peak, and trough, and redo the calculation.

### Bayesian dosing

In Bayesian dosing, you have the ability to calculate an AUC more dynamically. You can even estimate the AUC 24 for future doses. You can also calculate a dosing regimen with a single level. In the ASHP guidelines, they refer to obtaining a peak and trough, but the reality is that the levels can be drawn at any time. Bayesian dosing is therefore time agnostic. You also don't have to wait for a steady state, you can obtain levels within the first 24 to 48 hours, which helps to prevent delays and appropriate therapy.

The table below summarizes these differences:

## The roadmap from trough to AUC dosing

With learnings from hundreds of institutions that have converted to Vancomycin AUC dosing with DoseMeRx, we've distilled the key steps into 3 categories - People, Process, and Technology - to put you on a path toward successful implementation.

### People – leverage stakeholders to build engagement

1. Engage key stakeholders: The first step in implementing any clinical pharmacy program is engaging key stakeholders as the champions that will help drive your success. Having support from a pharmacy, key physician personnel, and hospital administration will ensure you have access to the budgetary resources you need. The individuals responsible for antimicrobial stewardship at your institution will most likely be leading this conversation.
2. Engage laboratory & nursing: Two groups that will be great partners throughout the conversion are the laboratory (i.e. phlebotomy) and nursing. The workflow of these two groups is directly and positively impacted when using Bayesian dosing. This is because the overall number of labs that are drawn will be reduced and there will be less reliance on obtaining trough levels at specific times.
3. Identify super users: When implementing new Bayesian dosing software, it’s important to designate "super users.” A super user is someone that will receive advanced training and can provide clinical leadership on an ongoing basis. This group can mentor new users and serve as clinical expert resources for difficult cases or where additional knowledge would be beneficial.
4. Messaging for the team: Everyone involved in this process should be given an elevator speech to help explain why you're implementing a new mechanism for dosing Vancomycin - even something as simple as "we're converting to AUC-guided dosing based on recommendations from best practice guidelines that were released in 2020" or “it will allow us to get to a therapeutic dose faster.”
5. Be patient: This process will require overcoming an ingrained mindset. Think about how long you've been in the habit of obtaining levels at certain times and dosing to a trough. Implementation will require retraining, and it may even counter some of what you've been teaching people for so many years. Be patient during this process and you'll be successful!

### Process – streamline your path forward

1. Keep protocols and policies as simple as possible
As you begin the process of implementation start with a clear, streamlined protocol and policy that avoids too many exceptions. When an institution is too granular with a list of infections that may be included or excluded from AUC dosing it can be difficult to follow implementation. Most institutions start with a target AUC goal of 400 to 600 for all infections being treated with vancomycin (with the exception of patients that have certain CNS infections, continuous or peritoneal dialysis, surgical prophylaxis, and a few others.)
1. Create a list of FAQs
Once you have your protocol and dosing method methodology selected, create a supplemental FAQ document that can be updated in real-time and accessible to all staff members; this will be especially valuable during training. Many hospitals also start vancomycin dosing rounds, which give pharmacy staff the opportunity to learn and review from the “super users” you’ve established. Typically, learning increases exponentially when staff are able to review and discuss actions taken with real patients.
1. Develop a transition of care plan
Next, coordinate a transition of care plan for patients discharged with IV therapy. Often times patients will go to a hospital-based outpatient infusion antimicrobial therapy (OPAT) program, and continue AUC-based dosing. It is also good to work with your common local home infusion providers as well to come up with a plan for how you're going to discharge patients out of the hospital and into home infusion and keep them on the AUC-based dosing protocol.

2. Update vancomycin lab limits
An essential part of the implementation process is to not forget your lab! You need to work with your lab to adjust critical values for vancomycin as you move from trough to AUC dosing. For example, with trough-based dosing, there is usually a critical lab value or threshold that triggers a phone call by the lab. The typical response is that the dose is withheld and then the pharmacy or the physician is contacted for next steps. However, with Bayesian dosing, and the ability to get a lab at any time, these critical values may become obsolete or need to be readjusted from the values that were used when only trough-based dosing was used.
1. Create targeted education for nurses and non-ID providers
Educational materials that describe the clinical background for the change to AUC conversion along with the benefits of improved patient care should be shared with these groups. In addition, include practical tips such as explaining why levels can be obtained at any time (vs. having to wait until steady state) and how blood draws for vancomycin levels no longer have to be wasted if they are not drawn at the correct time. The new laboratory protocol and the elimination or changing of critical values (as discussed above) should also be included as part of their education.

Once you've got everything in place, set a “go-live” date, and make sure that this is communicated to all involved.

### Technology – in healthcare, convenience is key

#### Selecting a Bayesian dosing tool

The most valuable resource in healthcare today is time – selecting technology that is simple, convenient, and requires minimal time to onboard will increase your likelihood of success.

Make sure the software is accessible at the point of care. Having it embedded in another program that is used throughout the day offers a higher level of convenience, such as how DoseMeRx can be accessed through Sentri7. DoseMeRx also gives you the ability to retrieve previous course information, which is beneficial from a historical perspective and when treating patients that come in frequently.

#### Evaluate data security and PHI considerations

Of course, whenever using an application that includes patient information, you need safeguards in place for the protection of that data. DoseMeRx has received HITRUST certification to provide you with the safest and secure Bayesian dosing platform

Shifting from trough-based dosing to AUC-based dosing for vancomycin has numerous clinical and operational benefits. The incorporation of Bayesian software into your vancomycin monitoring program will result in improved dosing accuracy (to achieve those AUC targets), decrease laboratory resources, and improve nursing satisfaction. DoseMeRx, integrated into solutions such as Sentri7 results in a more streamlined workflow for the pharmacists and gives them more time to focus on other critical patient care activities.

#### Discover key benefits of integrating a Bayesian dosing calculator into your clinical surveillance technology.

This article was authored by Dr. Kristi Kuper, Pharm.D., BCPS Director of Clinical Pharmacy, DoseMeRx. Dr. Kuper is a Board Certified Pharmacotherapy Specialist who has spent the last 20 years in a variety of clinical pharmacy leadership roles working with more than 500 hospitals. She has contributed to over 40 publications and has experience co-leading national research projects on under-researched areas in antibiotic stewardship.

With the combined power of Sentri7 and DoseMeRx, access personalized vancomycin dosing to enhance patient safety and streamline pharmacy workflow. With a single click, pharmacists can review patient-specific parenteral vancomycin dose recommendations calculated automatically using key clinical data such as patient weight, laboratory values, creatinine levels and drug administration times.