Crash and Burn: The Approach to the MVC Patient

Certain pathology gets a lot of attention in medical school.  Stroke? Sure!  Tests love asking about which vessel is blocked based on clues from the physical exam.  And rightly so; a fund of medical knowledge is certainly valuable when it comes to identifying pathology such as this.  However, when faced with a problem like blunt trauma, i.e. the “MVC”, one may find that there are also many practical and logistical factors that require bedside experience, ranging from marshaling of resources to reconciling patient presentation with reported mechanism of injury.

“He seems to be sleeping comfortably.  Dim the lights and give him a blanket.”

With street smarts in mind, we took the opportunity to talk with Dr. Liz Powell regarding her approach to the blunt trauma patient that is triaged to a middle acuity level area.  Some highlights from our discussion over the next two podcast sessions include:

• Take the opportunity to accompany the EMS providers into the room when they arrive.  It’s a great chance to gather first-hand information and impressions.  It can also be very efficient if they are able to stick around and help you with some of the steps below.
• While taking your initial history, immediately get the patient off of the backboard.  
• As part of your primary survey, fully expose the patient.  Quickly look on and in everything for injuries.
• Always obtain history regarding anticoagulant use.  If a patient is taking them it can significantly impact your diagnostic imaging decisions (head CT).
• Aside from identified injuries, keep patient’s age and functional status in mind when it comes to decisions for discharge.  

One of the major points of discussion that comes up when assessing a trauma patient in the emergency department is that of imaging studies.  Often, CT scans are utilized to assist in diagnostics of suspected severe injury in patients that have been in a motor vehicle collision.  This can be useful in confirming your clinical suspicion of severe injury, but what should be done if the scans turn up a heap of nothing and you still have clinical concerns?

By painful trial and error one such scenario that can be encountered in the emergency department is that of occult bowel injury after blunt trauma.  Have you ever had a patient with a tender abdomen after a car crash but with nothing remarkable on CT scan return to your emergency department or declare themselves after admission with a hollow viscus injury?  One study1 based in New Zealand looked back at their laparoscopic abdominal surgery findings in patients with blunt trauma who also had a preoperative abdominal CT scan performed to look at the scan’s ability to predict hollow viscus injury.  A consultant radiologist who was blinded to the operative findings was asked to read the images, the interpretations of which were compared to what the surgeons saw on the operating room.  The results found was that the interpretation of the CT scan for hollow viscus injury had a 55% sensitivity and a 92% specificity.  When present, the more common signs for hollow viscus injury were found to be free intraperitoneal or retroperitoneal air, oral contrast extravasation, mesenteric defects or patchy bowel enhancement.  There can certainly be some variability in sensitivity based on interpreter experience and skill, however, a 55% coin toss certainly does sound less than optimistic.

Call It...

Because of the elusive nature of these injuries there have been several studies examining the sensitivity and predictive value of the physical exam for occult bowel injury, particularly in the pediatric population where the opportunity to avoid the radiation of CT scans is sought.  One particular exam finding of interest is that of the “seat belt sign” or abdominal/chest wall bruising in the pattern of seat belt contact.  One such project2 was performed as a sub analysis of a large prospective multi center observational study wherein patients 18 years of age or younger with a documented seat belt sign after motor vehicle collision were analyzed.  The presence of a seat belt sign on initial examination was found to have a significant correlation of risk for intra-abdominal hollow viscus injury with a higher proportion of injury requiring intervention than those patients without the sign.  By the numbers, 14.4% of patients with a seat belt sign were found to have intra-abdominal injury, with 6.8% of seat belt sign patients requiring acute surgical intervention, compared to a comparative 6.7 and 2.4% respective occurrence of these events for all comers after MVC.  The presence of a seat belt sign on initial physical exam was found to carry a relative risk of 4.5 for acute surgical intervention.  Another interesting finding was that of a small portion of patients that underwent acute surgical intervention (2%) had no abdominal pain or tenderness on exam, with only a seat belt sign as a clue to intra-abdominal trauma.  

While these studies and this review are certainly not comprehensive, they do highlight two important points regarding blunt abdominal trauma.  First, hollow viscus injury can be notoriously difficult to diagnose via CT scan, and second, that a seat belt sign can be an important adjunct in your physical exam for risk stratification in blunt abdominal trauma.  In short, if a patient of yours is found to have blunt abdominal trauma and a tender abdomen, it may be advisable to keep the patient for observation in the setting of a negative abdominal CT scan, especially if there is a seat belt sign present on exam.

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References

1. Bhagvan, Savitha, et al. "Predicting hollow viscus injury in blunt abdominal trauma with computed tomography." World journal of surgery 37.1 (2013): 123-126.

2. Borgialli, Dominic A., et al. "Association Between the Seat Belt Sign and Intra‐abdominal Injuries in Children With Blunt Torso Trauma in Motor Vehicle Collisions." Academic emergency medicine 21.11 (2014): 1240-1248.