SAN DIEGO (FRONTLINE MEDICAL NEWS) – A simple intervention of initial warfarin dose capping in hospitalized patients aged 85 years and older led to significant reductions in supratherapeutic INRs without a significant change in length of stay, a single-center study showed.

“We’re excited to see if these results are reproducible,” Jonathan Falsetta, PharmD, said at the biennial summit of the Thrombosis & Hemostasis Societies of North America. “We do feel that it may represent an important step forward in warfarin safety in a vulnerable patient population.”

In a previous pilot study, Dr. Falsetta and his associates retrospectively reviewed supratherapeutic INRs in 21 patients at Northwell Health’s Plainview Hospital , a 204-bed teaching hospital in Long Island, N.Y., between January and September of 2015. These were defined as an INR of 5 or greater, not present on admission. Of the 21 patients, 12 were younger than 85 years old. Their initial dose of warfarin was 4 mg, and the peak INR ranged from 5.15 to 9.29. The remaining nine patients were at least 85 years-old. Their average initial dose was 5 mg, and their peak INR range was 5.17 to 12.2.

“From this we gathered that we had an issue with dosing,” said Dr. Falsetta, who is assistant director of pharmacy clinical educational services at Plainview Hospital. “These patients were spiking dangerously high INRs, and we needed to do something about it.”

A review of current medical literature revealed a lack of well-validated recommendations regarding warfarin initiation in older patients, so Dr. Falsetta and his associates set out to create their own dose-capping recommendation. This involved limiting the initial dose of warfarin to 2.5 mg or less for hospitalized patients aged 85 years and older.

“We wanted this to be applicable to patients regardless if they were warfarin naïve or if they had been on warfarin prior to admission,” he said.

Before the roll out, clinical pharmacists and pharmacy residents conducted provider education on the initial dose capping protocol. Providers could order initial doses that exceeded 2.5 mg with valid clinical reasoning. Outcomes of interest were dosing protocol compliance and post-intervention analysis of INRs in this patient population. The pre-intervention period spanned from Nov. 1, 2014 through Oct. 31, 2015, while the post-intervention period spanned from Nov. 1, 2015 through Oct. 31, 2017. Dr. Falsetta reported data from 768 patients.

Between the pre-intervention and post-intervention periods, compliance with dose capping rose from 38.5% to 64.2% (P less than .001), the supratherapeutic INR rate dropped from 20.9% to 13.3% (P= .004), and the length of hospital stay in hours rose from a mean of 145.8 to a mean of 155.8, which was not statistically significant (P= .13).

Following the post-intervention period, the number of peak INRs in the 1 to 2 range rose by 15% and the number of peak INRs in the 2 to 3 range rose by 6%. At the same time, the number of peak INRs in the 3 to 4 range fell by 6%, the number of peak INRs in the 4 to 5 range fell by 36%, and the number of peak INRs in the 5 and greater range fell by 53%. These INR percentages represent relative increases and/or decreases.

“This was a relatively simple intervention that resulted in significant reductions in supratherapeutic INRs,” Dr. Falsetta said.

The researchers also observed that there was less IV vitamin K use after the dose capping intervention. “We can’t say for sure that this was tied to the intervention, but it was interesting, and it is something for us to take a look at, as well as roll this out in future iterations,” he said. “We are on the cusp of rolling this out at some of the tertiary sites within our health care system, and some of the community sites as well.”

He acknowledged certain limitations of the study, including its single-center design, relatively small sample size, and lack of clinical endpoints. “I’d like to be able to tie this to something like reduced bleeding events,” Dr. Falsetta said. “I think that’s something we need to explore in the future.”

Dr. Falsetta reported having no financial disclosures.

SOURCE: Falsetta J et al. THSNA 2018 .


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