Warfarin related intracranial haemorrhage: a case-controlled study of anticoagulation monitoring prior to spontaneous subdural or intracerebral haemorrhage.

We present a retrospective, case-controlled study of the degree of over-warfarinisation and the frequency of International Normalized Ratio (INR) monitoring in patients with spontaneous intracranial haemorrhage (ICH) compared with a control group without ICH. A higher proportion of patients with ICH were taking warfarin than patients in the control group (33/221 [15%] versus 16/201 [8%], p<0.05). There was no significant difference between the ICH group and the controls in the mean INR of warfarinised patients on presentation, the mean INR when last measured prior to presentation, or in the number of days since the INR was last tested. There was no correlation between the time since the INR was last measured and the INR on presentation. Only 2 (6%) of patients were excessively anticoagulated at the time of ICH. Thus, in this study, warfarin use was associated with an increased risk of ICH despite appropriate community INR monitoring and therapeutic anticoagulation.