Article, Emergency Medicine

Air bag and oral anticoagulation: a deadly combination in a low-velocity car accident?

Case Report

Air bag and Oral anticoagulation: a deadly combination in a low-velocity car accident?

Abstract

Air bags significantly reduce the risk of severe injury or death during a car accident. Nevertheless, air bags are also known to produce injuries.

This case report documents a fatal combination: air bag and oral anticoagulation in low-speed car collisions. The deploying air bag injured a 65-year-old front-seat passenger who was taking maintenance anticoagulation because of chronic atrial fibrillation. The blunt trauma resulted in a fatal cerebral hemorrhage.

Severe head injuries caused by deploying air bags could be prevented by maintaining adequate distance to the device. Air bags are known to reduce the risk of severe injury or death in car accidents. Nevertheless, several reports can be found that present injuries caused by air bags. This case report documents a fatal combination: air bag and oral

anticoagulation in low-speed car collisions.

A 65-year-old woman was evaluated in the medical university hospital for an air bag-related closed head trauma. With her seat belt on, she was riding in the front seat of a car that was stuck by another car traveling at approximately 30 km/ h (~19 miles/h) into the driver’s side. The front air bag

deployed, causing a blunt trauma to her head. There was no

loss of consciousness, and the patient ambulated to the medical center. On initial examination, no external injuries were noted with the exception of epistaxis. She had no complaints of headache, nausea, or amnesia to the event; and her neurologic examination was normal. Her medical history was pertinent only in that she was on maintenance warfarin anticoagulation for the past 2 years because of chronic atrial fibrillation.

Because a screening Head Computed Tomographic scan showed a discrete subarachnoid hemorrhage, she was admitted for observation (Fig. 1). Oral anticoagulation being in the therapeutic range on the day of accident was paused (international normalized ratio, 3.26; range, 2.0-3.5); vitamin K (Konakion, RocheGmbH, Vienna, Austria) and human prothrombin complex (Octaplex, Octapharma Pharmaceu- tika GmbH, Vienna, Austria) were administered. Over the succeeding 24 hours, the patient remained alert and

Neurologically intact; however, she then became somnolent and developed a right-sided hemiparesis. A CT scan now showed a new subdural hemorrhage and a centerline shift of 4 mm (Fig. 2). An immediate craniotomy was performed. At this point, coagulation was almost normal (international normalized ratio, 1.20). After surgery, she was left at the intensive care unit. The CT scan of the next day showed an increase of subdural hemorrhage, a pronounced cerebral edema, and a centerline shift of 2.5 cm (Fig. 3). The hematoma was once again surgically evacuated. The neurologic condition of the patient did not improve, and the EEG showed no signs of cerebral activity 2 days later.

Previous studies report that air bags usually reduce the risk of severe injury or death in car accidents. Cummings et al analyzed the changes in traffic crash mortality rates due to alcohol and the lack of seat belts, air bags, motorcycle helmets, or Bicycle helmets in the United States between 1982 and 2001. They examined 858741 deaths in traffic and hypothesized that 4305 lives (4%) were saved because of air bags [1]. Olson et al looked into 128208 automobile occupants involved in fatal crashes on US roadways during

Fig. 1 Primary CT scan, showing a discreet subarachnoid hemorrhage.

0735-6757/$ – see front matter (C) 2008

111.e4 W. Pichler et al.

1990 to 2002 and assumed that first-generation air bags were

Fig. 2 Second CT scan, demonstrating a recent subdural hemorrhage and a centerline shift of 4 mm.

associated with a 10% decrease in the risk of deaths for an average front-seat occupant; second-generation air bags were associated with an 11% decrease [2]. The National Highway Traffic Safety Administration estimates that air bags reduce the risk of driver deaths by about 11% [3].

Some articles, however, report of severe injuries attributed to the use of air bags. A couple of case reports document upper limb fractures as a result of air bag deployment [4-8]. Lau et al studied air bag deployment loads on anesthetized swine leaning against the system during inflation and observed heart injuries, cardiac contusion associated with arrhythmias, rib fractures, vascular injuries, splenic lesions, and liver lacera- tions [9]. ocular injuries including periorbital fractures, corneal abrasion, chemical keratitis, chemical burns, retinal tears, lens subluxation, hyphemia, and contusion are as well reported in literature [10-16]. Children are highly in danger in particular when inappropriately used. Mehlman et al report a case of a 3-year-11-month-old girl as a restrained front-seat passenger involved in a low-speed head-on collision. The passenger-side air bag deployed on impact, resulting in a minimally displaced lateral humerus condyle fracture, a severe injury of the left brachial plexus, a right infraorbital blowout fracture, a right Retinal hemorrhage, a small tentorial subarachnoidal hemor- rhage, superficial abrasions, and burns around the head and neck [17]. Quinones-Hinojosa et al identified 263 cases of injury associated with air bag deployment between 1993 and 2002, of which 159 were fatal. fatal injuries included skull and cervical spine fractures, subdural hemorrhages, diffuse axonal injuries, cord transections, and decapitations [18]. Inadequate distance to the air bag may increase the risk of getting harmed. Cunningham et al report a case of a 47-year-old woman dying of severe head injury caused by her sitting too far forward when the air bag was deployed [19].

Fig. 3 Final CT scan, displaying an increase of subdural hemor- rhage, a pronounced cerebral edema, and a centerline shift of 2.5 cm.

The reported case documents a fatal combination. Head injury caused by the deployed air bag in a low-speed collision and oral anticoagulation led to the death of this front-seat passenger. Patients discharged on oral anticoagulation should be aware of this risk. The main concern is for front-seat passengers in low-velocity impacts causing no or little harm in the absence of an air bag. Maintaining adequate distance to the air bag may reduce the hazard of severe head injuries. Manual deactivation of the system in urban traffic may also be advantageous and should be discussed as a possibility for patients with oral anticoagulation.

Air bags are known to considerably reduce the risk of severe injury or death; nevertheless, these devices are also noted for producing injuries. The main concern of this report is for patients discharged on oral anticoagulation. Keeping appropriate distance to the air bag may reduce the hazard of severe head injuries for these people.

Wolfgang Pichler MD Franz Josef Seibert MD Wilfried Hartwagner MD Wolfgang Grechenig MD Department of Traumatology Medical University of Graz A-8036 Graz, Austria

E-mail address: [email protected]

Gerhard Kopeinigg MD Department of Radiology Medical University of Graz A-8036 Graz, Austria

doi:10.1016/j.ajem.2007.06.025

Case Report 111.e5

References

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