Anna D. Garrett, PharmD, BCPS, CPP
Published Online: Friday, June 1, 2007

Nearly 75% of warfarin-treated patients who present to the emergency room (ER) for any complaint have an international normalized ratio (INR) that falls outside the therapeutic range. This finding was the result of a study of 782 patients who were seen in the ER of 2 academic medical centers over a 14-month period. Seventy-two percent of the patients had an INR measured outside of the recommended range of 2 to 3; 43% of the INRs were too low, and 29% were too high.

An INR of greater than 5 was noted in 11% of patients, 40% of whom were experiencing gross bleeding. Twelve patients had an intracranial hemorrhage, including 5 with an INR above 3. Conversely, stroke or thromboembolism was seen in 51 patients who had specifically been receiving warfarin to prevent such events. Roughly half of these patients had an INR below 2.

The researchers were unable to identify any clinical factors that reliably predicted a nontherapeutic INR. The authors concluded that, given the dangers of out-of-range INRs, warfarin-treated patients who present to the ER should have their INR tested and addressed as indicated.

Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.

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