Patient Safety Tip of the Week

August 21, 2018

Delayed CT Scan in the Anticoagulated Patient



An 81 year old SNF patient with a left hemiparesis secondary to an old stroke, muscle weakness, difficulty swallowing, difficulty walking, and impaired cognition was briefly left unattended on a commode and fell (CDPH 2018). Blood was noted coming from skin adjacent to her left eye. She was sent to a local hospital emergency department, where a CT scan of the head was said to show only changes related to the prior stroke and no acute findings. A laceration adjacent to the left eye was sutured and she was returned to the SNF. The report does not provide a full medication list but does note the patient was on Eliquis (the novel oral anticoagulant apixaban). The report also does not provide measures of her renal function or other lab data. Two days later she was noted to have a mental status that was altered compared to her baseline and she was sent back to the hospital, where a CT scan showed a 1.2 cm left-sided subdural hematoma with mass effect that had developed since the prior CT scan. It was decided to provide only comfort care and she died 5 days later.


This case illustrates an issue that has led to considerable debate - what to do with the anticoagulated patient who suffers minor head trauma and has an initial negative CT scan. The multiple good clinical decision support tools we have for deciding about CT scans in patients with minor head trauma (see our March 2017 What's New in the Patient Safety World column “Update on CT Scanning after Minor Head Trauma”) do not apply to patients on anticoagulants.


In our July 17, 2007 Patient Safety Tip of the Week “Falls in Patients on Coumadin or Heparin or Other Anticoagulants” we highlighted the problem of delayed hemorrhage after falls in patients on anticoagulants. Specifically, we discussed the patient who falls and has minor head trauma, has a negative CT scan of the head, and then later develops a subdural hematoma (or other intracranial hemorrhage). The example we gave was an elderly patient with a cardiac condition on full-dose heparinization while an inpatient who had an unwitnessed fall in the hospital one evening. He did not lose consciousness and was alert and fully oriented when the medical resident examined him after the fall. He had a mild ecchymosis on his right forehead but no focal neurological signs and no evidence of trauma elsewhere on the body. Because the patient was fully anticoagulated, the resident ordered an emergency head CT scan, which was normal. No changes were made in his heparin regimen. The following morning the patient was more somnolent than usual and a repeat CT scan showed a sizeable subdural hematoma that required surgical evacuation.


Several of our subsequent columns presented literature reviews showing that the occurrence of delayed subdural hematoma requiring intervention is very rare in anticoagulated patients having an initial negative CT scan. They note that doing delayed scans is costly, both in terms of the cost of a second scan and the cost of keeping the patient under observation for a longer period of time.


Since our last update in 2014 (see our July 8, 2014 Patient Safety Tip of the Week “Update: Minor Head Trauma in the Anticoagulated Patient”) there have been several more articles on the issue.


A study (McCammack 2015) showed that use of a routine six-hour follow-up head CT in patients on anticoagulant/antiplatelet treatment after mild TBI is of extremely low yield, with delayed ICH occurring in only one of 134 patients (0.7% incidence) in the study population. Furthermore, the one case of delayed ICH required no intervention and resulted in no sustained deviation from the patient’s baseline.


Another study evaluated the utility of 2 sequential CT scans at a 48-hour interval (CT1 and CT2) in patients with mild head trauma (Glasgow Coma Scale 13–15) taking oral anticoagulants (Campiglio 2017). Of 344 patients, 337 (97.9%) had a negative CT1. CT2 was performed on 284 of the 337 patients with a negative CT1 and was positive in 4 patients (1.4%), but none of the patients developed concomitant neurologic worsening or required neurosurgery. The authors conclude that systematic routine use of a second CT scan in mild head trauma in patients taking anticoagulants is expensive and clinically unnecessary.


A systematic review and meta-analysis (Chauny 2016) reviewed studies estimating the risk of delayed intracranial hemorrhage 24 h after head trauma in patients anticoagulated with vitamin K antagonist and normal initial CT scan. Seven publications were identified encompassing 1,594 patients who had a repeat CT scan after a normal first head scan. For these patients, the pooled estimate of the incidence of intracranial hemorrhage on the second CT scan 24 h later was 0.60% (95% CI 0–1.2%) and the risk of neurosurgical intervention or death was only 0.13%. They concluded that, in most situations, a repeat CT scan in the emergency department 24 h later is not necessary if the first CT scan is normal. But the authors note that special care may be required for patients with serious mechanism of injury, patients showing signs of neurologic deterioration, and patients presenting with excessive anticoagulation or receiving antiplatelet co-medication.


A retrospective multicenter study from the Netherlands (Verschoof 2018) looked at patients with mild traumatic brain injury (mTBI) on anticoagulants who had an INR ≥ 1.7 and reportedly normal cranial CT obtained within 24 h after trauma. Of 905 patients, four deteriorated neurological within 24 hours and 5 others deteriorated on days 2, 18, 22, 36 and 52, respectively. In six patients, including all four that developed symptoms within 24 h, intracranial hemorrhage (ICH) was found upon reevaluation of initial imaging. So no patient actually developed delayed ICH within 24 hours. They also did a meta-analysis of 9 studies with data from 2885 patients. The estimated pooled proportion of symptomatic delayed ICH or delayed diagnosis of ICH within 24 h was 0.2%. They concluded that delayed diagnosis of ICH within 24 h is very rare in patients on anticoagulants with minor head trauma after reportedly normal initial CT and that routine hospitalization of these patients seems unwarranted when the initial cranial CT is scrupulously evaluated.


And a just published prospective observational study also suggests that routine observation and serial cranial computed tomography may not be necessary in these patients (Cheonoweth 2018). The authors looked at patients 55 years and older who had blunt head trauma and were seen emergently at 11 hospitals in northern California. Median age was 75 years and 40% of the total 859 patients enrolled in the study were taking anticoagulant and antiplatelet medications. Only 3 patients (and only one on warfarin alone) suffered delayed traumatic intracranial hemorrhage. Thus, the overall rate of delayed intracranial hemorrhage in patients on warfarin alone was 1.3%. The findings of this study suggest that routine observation and serial cranial computed tomography may not be necessary in these patients. It was also notable that 2 of the 3 delayed hemorrhages occurred 3 and 5 days after the head trauma. Those guidelines that recommend a repeat CT scan usually recommend it within 24 hours of the trauma, so even these delayed hemorrhages would have been missed. The study also only analyzed patients who had been transported to ER’s via EMS, so these likely even overestimated the risk of delayed intracranial hemorrhage in patients with minor head trauma.


In a study in a different population, patients with head trauma who had intracranial hemorrhage on an initial CT scan, Bellal et al. (Bellal  2018) found a threefold increase in the rate of worsening repeat head CT in patients on warfarin or antiplatelet agents compared to those not on such agents (26 vs 9%).


A prospective study of patients on anticoagulants or antiplatelet medications who had a ground-level fall with head trauma found the incidence of traumatic intracranial hemorrhage (tICH) was low in both groups (Ganetsky 2017). Interestingly, there was no statistical difference in rate of tICH between antiplatelet and anticoagulants, which is unanticipated and counterintuitive as most literature and teaching suggests a higher rate with anticoagulants. The authors suggest a larger data set is needed to determine if small differences between the groups exist.


So, the bulk of evidence strongly suggests that delayed development of intracranial hemorrhage after minor head trauma in patients on anticoagulants when initial CT scan is negative is indeed rare. And those guidelines that would suggest observation of the patient for 24 hours and then repeat CT scan would probably lead to many unnecessary hospital stays and CT scans and excessive costs.


But, once again, we emphasize the need for good instructions for the patient and, more importantly, for the caregivers when such patients are to be discharged. The major initial symptoms and signs of subdural hematomas are usually related to changes in the level of consciousness or cognition rather than “focal” neurological signs. These signs can be subtle. That’s why we previously warned in our July 17, 2007 Patient Safety Tip of the Week “Falls in Patients on Coumadin or Heparin or Other Anticoagulants” that the “neuro checks” must be carried out as ordered (whether the patient is under hospital observation or being observed by family or others at home). We’ve often seen in that past that there is a tendency for “neuro checks” to be overlooked when the patient is asleep – which is exactly when neuro checks are most important! And telephone follow-up the next day may be an effective strategy.


So, your decision not to utilize 24-hour observation and repeat CT scan in anticoagulated patients with a normal initial CT scan might be backed up by statistics, but you need to ensure they will be sent to a setting where any change in level of arousal or cognitive function would be promptly recognized. The patient with a supratherapeutic INR or concomitant antiplatelet therapy or no reliable caregiver who can observe them at home would be one you might consider for 24 hour hospital observation and repeat CT scan in 24 hours. Of course, now that so many patients are on NOAC’s (novel oral anticoagulants) rather than vitamin K antagonists like warfarin, we don’t have good lab measures of their degree of anticoagulation to guide us.


However, as in our June 5, 2012 Patient Safety Tip of the Week “Minor Head Trauma in the Anticoagulated Patient” the optimal timing of CT scans remains unknown. We’d like to see a study that looks at the timing of initial CT scans that show intracranial bleeding in anticoagulated patients relative to the time of their head trauma. We suspect that the optimal approach may lay somewhere in between the above options. That might show that the initial CT scan might be delayed in an anticoagulated patient with minor head trauma who is alert without focal neurological signs or altered level of arousal or altered cognition. For example, you might opt to keep the patient on observation for 6-8 hours and then perform the initial CT scan.


We wish we had the final answer for you now. But we don’t. The literature would certainly suggest that, on the whole, we would waste a lot of resources if we put all such patients on 24-hour observation and did 2 CT scans (the initial one and then a repeat at 24 hours). But then you come across cases like the one in today’s column and the one in our July 17, 2007 Patient Safety Tip of the Week “Falls in Patients on Coumadin or Heparin or Other Anticoagulants” and it makes you think twice.




Some of our previous columns on CT scans in minor head trauma:


April 16, 2007 “Falls With Injury

July 17, 2007  Falls in Patients on Coumadin or Heparin or Other Anticoagulants

March 2010     CATCH: New Clinical Decision Rule for CT in Pediatric Head Trauma

November 23, 2010 “Focus on Cumulative Radiation Exposure

June 5, 2012    Minor Head Trauma in the Anticoagulated Patient”.

July 8, 2014    Update: Minor Head Trauma in the Anticoagulated Patient

January 2017   Still Too Many CT Scans for Pediatric Appendicitis

March 2017     Update on CT Scanning after Minor Head Trauma

September 2017 “Clinical Decision Rule Success



Some of our previous columns on head trauma in the anticoagulated patient:


April 16, 2007 “Falls With Injury

July 17, 2007  Falls in Patients on Coumadin or Heparin or Other Anticoagulants

June 5, 2012    Minor Head Trauma in the Anticoagulated Patient”.

July 8, 2014    Update: Minor Head Trauma in the Anticoagulated Patient







CDPH (California Department of Public Health). Intake # CA00551075, CA00550513. CPDH 2018; January 19, 2018



McCammack KC, Sadler CA, Guo Y, et al. Routine Repeat Head CT may not be Indicated in Patients on Anticoagulant/Antiplatelet Therapy Following Mild Traumatic Brain Injury. Western Journal of Emergency Medicine 2015; 16(1): 43-49



Campiglio L, Bianchi F, Cattalini C, et al. Mild brain injury and anticoagulants. Less is enough. Neurology Clinical Practice 2017; 7(4) August 01, 2017



Chauny J-M, Marquis M, Bernard F, et al. Risk of Delayed Intracranial Hemorrhage in Anticoagulated Patients with Mild Traumatic Brain Injury: Systematic Review and Meta-Analysis. J Emerg Med 2016; 51(5): 519-528



Verschoof MA, Zuurbier CCM, de Beer F, et al. Evaluation of the yield of 24-h close observation in patients with mild traumatic brain injury on anticoagulation therapy: a retrospective multicenter study and meta-analysis. Journal of Neurology 2018; 265(2): 315-321



Chenoweth JA, Gaona SD, Faul M, et al. for the Sacramento County Prehospital Research Consortium. Incidence of Delayed Intracranial Hemorrhage in Older Patients After Blunt Head Trauma. JAMA Surg 2018; 153(6): 570-575 Published online February 14, 2018



Bellal J, Sadoun M, Aziz H, et al. Repeat Head Computed Tomography in Anticoagulated Traumatic Brain Injury Patients: Still Warranted. The American Surgeon 2018; 80(1): 43-47 January 2014



Ganetsky M, Lopez G, Coreanu T, et al. Risk of Intracranial Hemorrhage in Ground-level Fall With Antiplatelet or Anticoagulant Agents. Academic Emergency Medicine 2017; 24(10): 1258-1266






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