Patients taking warfarin, a blood thinner widely prescribed to prevent blood clots from forming, who suffer minor head injury and have a negative CT scan should have another CT scan after 24 hours, according to the results of an Italian study published online Jan. 13 in Annals of Emergency Medicine.

"This protocol will identify most occurrences of delayed bleeding in these patients," said Vincenzo Menditto, MD, of the Ospedali Riuniti di Ancona in Ancona, Italy, in a statement. "This is particularly true of patients who are 65 years old or older. Patients on warfarin whose INR [international normalized ratio] level is higher than 3.0 are at even higher risk."

In 2002, the European Federation of Neurological Societies began recommending that all patients on anticoagulants who suffered a minor head injury be given an initial CT scan, admitted for a 24-hour observation period and then given a second CT scan. However, the authors noted some controversy over whether this guideline should apply to all anticoagulated patients, just elderly patients or those with more significant trauma.

To test these guidelines, the researchers enrolled 87 emergency department patients with minor head injury who were taking warfarin. Twenty-four hours after having a negative CT scan, five of the patients showed hemorrhage lesions on a repeat CT scan. Three of those patients were admitted to the hospital and one underwent craniotomy for a subdural hematoma.

In total, 16 percent of patients presented with hemorrhagic lesions on their first CT scan, with another 6 percent presenting lesions 24 hours later, according to the study results.

An additional two patients who were discharged from the hospital after two negative CT scans were subsequently admitted to the hospital with symptomatic subdural hematomas. Four of the patients with delayed bleeding had an initial INR level of greater than 3.0.

“Despite our 24-hour observation period, we observed that two patients later developed intracranial hemorrhage,” wrote the authors. “Although most such [hemorrhages occur] early, other authors have also reported delayed subdural hematomas. Extending the observation time to identify these occasional cases would require substantial additional resources and cost, and the 24-hour observation plus second CT scan protocol recommended by the European guidelines appears to be a sound compromise.”

The researchers did suggest that rather than extending the 24-hour observation period to catch more delayed hemorrhages, further observation may be warranted only in the subset of patients with an INR level greater than 3.0.

"Our study confirms the recommendation of the European Federation of Neurological Societies," wrote Menditto. "It recommends that all minor head injury patients on blood thinners should have an initial CT scan followed by admission for observation followed by a second CT scan before discharge. This is important for the growing portion of the population that is 65 or older and on blood thinners."