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Trauma 20 Years Ago: CT Imaging of the Aorta

CT scan is now the standard screening test for injury to the thoracic aorta. But 20 years ago, we were still gnashing our teeth about how to detect this injury.

An interesting paper was published in the Journal of Trauma 20 years ago this month on this topic. Over a 2 year period, the Medical College of Wisconsin at Milwaukee looked at all patients who underwent imaging for aortic injury. At the time the gold standard was aortogram. They looked at patients who underwent this study and CT, which was not very common at the time.

They had 50 patients who underwent aortography alone and 17 who underwent both tests. Of the 17, 5 had the injury, but only three were seen on CT. There were also two false positives. Sensitivity was 83%, specificity was 23%, with 53% accuracy. The authors concluded that any patients with strong clinical suspicion of aortic injury should proceed directly to aortogram.

Why the difference today? Scan technology and resolution has increased immensely. Also, the timing of IV contrast administration has been refined so that even subtle intimal injuries can be detected. CT scan is now so good that we have progressed from the CV surgeon requiring an aortogram before they would even consider going to the OR, to the vascular surgeon / interventional radiologist proceeding directly to the interventional suite for endograft insertion.

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Is Too Much Crystalloid a Bad Thing?

All trauma centers have massive transfusion protocols, and they typically spell out the approximate ratios of blood to plasma to platelets. But they do not address the use (or overuse) of crystalloid during these large volume resuscitations.

A multicenter, prospective study was carried out looking at the outcomes after resuscitation from hemorrhagic shock using massive transfusion (at least 10u PRBC in 24 hrs). The patients were severely injured (average ISS 34), and overall mortality and incidence of multi-organ failure was 21% and 65%, respectively. The median amount of crystalloid given was 17 liters, and median red cell transfusion was 14 units in 24 hours.

The authors found that if the crystalloid to PRBC ratio exceeded 1.5:1, morbidity increased significantly. The incidence of multiple organ failure doubled, ARDS tripled, and abdominal compartment quintupled! The authors suggested further research, and did not provide specific strategies for decreasing early crystalloid.

Bottom line: As expected, giving so much crystalloid that we turn people into the Sta-Puft Marshmallow Man is not good. While waiting for additional research, it is probably prudent to try to rapidly achieve definitive control of bleeding and apply gentle use of pressors to decrease the total crystalloid given during resuscitation.

Reference: The crystalloid / packed red blood cell ratio following massive transfusion: when less is more. Presented at the 24th Annual Scientific Assembly of the Eastern Association for the Surgery of Trauma, January 2011.

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Rapid Noninvasive Rewarming Using a Hubbard Tank

Hypothermic patients need to be rewarmed using the most appropriate method. Patients with mild hypothermia (32-35 degrees centigrade) generally only require removal of wet clothing and surface warming. Moderate hypothermia (28-32 degrees C) to severe hypothermia (<28 degrees C) is very serious and requires more aggressive central rewarming techniques.

Basic central rewarming techniques, such as warm inspired gases, warm IV fluids, and gastric or peritoneal lavage can raise the temperature about 3 degrees per hour. 

Rapid central rewarming techniques, like thoracic lavage (6 degrees/hr), AV bypass devices (1-4 degrees/hr), and cardiopulmonary bypass (18 degrees/hr) are typically used on patients with severe hypothermia.

A technique that we use at Regions Hospital involves the use of the Burn Center’s Hubbard Tank. Patients are carefully immersed, torso first, then one extremity at a time to avoid rebound hypothermia. It is possible to increase core temperature using this method faster than bypass (>20 degrees centigrade/hr)! Typical time in the tank is an hour or less for any degree of hypothermia.

Patients can be immersed with EKG monitors and IV lines in place. Temperature monitoring should be performed using a thermistor tipped urinary catheter. Many hospitals don’t have a full Hubbard tank, but do have smaller therapy baths that work nearly as well.

Tips:

  1. A physician must stay with the patient while immersed in case arrhythmias develop.
  2. Position the urinary catheter and collecting bag in such a way that urine in the tubing does not backwash into the bladder. This will falsely and rapidly increase the temperature reading. 
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Cervical Spinal Cord Injury: Who Needs A Tracheostomy?

The sad truth is that patients with cervical spine injury may need a tracheostomy. In very high lesions (C1-2) the need may be permanent. Lower injuries (C3-5) frequently need a trach for a limited period of time while they develop enough reserve to compensate for the lost of chest wall muscle power.

It’s not always easy to tell which patient is likely to need intubation upon arrival in the ED. I’ve seen occasional patients fail while getting their CT scans, which is poor planning. Is there a way to predict who might fail, thus benefiting from early intubation and an early plan for tracheostomy?

The trauma group at LAC + USC Medical Center undertook a National Trauma Databank review to try to answer this question. They identified 5256 patients with cervical spinal cord injuries without a severe traumatic brain injury that would otherwise require intubation. About 21% received tracheostomies, and the common predictors were:

  • Intubation at the scene by EMS (they’ve done the job of deciding for us!)
  • Intubation in the ED
  • Complete cord injury at any level
  • Facial fractures
  • Chest trauma
  • Injury Severity Score >=16

Patients who received a tracheostomy generally spent more days on the vent, in the ICU and in the hospital than those who did not. However, their mortality was lower.

It’s generally recognized that patients with complete injuries from C1-C5 routinely require tracheostomy. The surprising thing about this study was that complete injuries at C6 or C7 did as well.

Bottom line: If you have a patient with a spinal cord injury who meets any of the criteria above, stand ready to intubate. I tell my trainees that, if at any time they see something that makes them think about intubating, they should have already done it. Likewise, the surgical ICU team should have a low threshold to performing an early tracheostomy on these patients.

Reference: Incidence of clinical predictors for tracheostomy after cervical spinal cord injury: a National Trauma Databank review. J Trauma 70(1): 111-115, 2011.

Picture: crossbow bolt through the mouth and cervical spinal cord.

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EAST Evidence Based Review: Distracted Driving

EAST is branching out from one of its core areas, creating trauma practice guidelines. They are now beginning to address other problems using the same techniques for developing their practice guidelines. Instead of generating guidelines for clinical care, they are creating action statements based on the best available literature.

This Distracted Driving review was one of a group of new EBRs was presented last week at the EAST Annual Scientific Assembly. The panel reviewed information from government agencies and studies based on crash databases and simulations. The number of cellphone subscribers has surpassed 250 million, and the number of deaths from distracted driving has followed a similar curve. 

Distracted driving is implicated in 20% of injury crashes and 16% of fatal crashes. Drivers under age 20 has the highest proportion of distracted drivers. 

EAST made three Level II recommendations, which means that they are reasonably justifiable by available scientific evidence and strongly supported by expert opinion. They are:

  • Drivers should minimize all distractions while on the road
  • Cell phone use and texting should not be performed while driving
  • Younger inexperienced drivers should not use cell phones during their probation period (if such a period is mandated by their state)

Future areas of interest will include studying the impact of legislation regarding cell phones and texting, development of crash avoidance systems, and evolving cell phone technologies.

Reference: Evidence Based Review on Distracted Driving, presented at the 2011 EAST Annual Scientific Assembly. Note: this information is preliminary and may be changed prior to publication.

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