Monthly Archives: February 2011

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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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Solid Organ Injury: How Soon Can We Begin Chemical DVT Prophylaxis?

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Nonoperative management of solid organ injury is the norm, and has reduced the operative rate significantly. At the same time, the recognition that development of deep venous thrombosis (DVT) in trauma patients is commonplace creates uncertainty? Is it safe to give chemical prophylaxis with low molecular weight heparin (LMWH)? How soon after injury?

The trauma group at USC+LAC recently published the findings of a retrospective review of 312 patients undergoing nonoperative management for their liver, spleen or kidney injuries. They looked at chemical prophylaxis administration and its relationship to failure of nonop management of solid organ injury.

As expected, as the grade of the solid organ injury increased, so did the failure rate of nonoperative management. Administration of low molecular weight heparin, such as enoxaparin, did not increase failure rate in this study. All but one failure occurred in patients who had not yet received the injections. Likewise, two DVT and two pulmonary embolisms occurred, but only in patients who had not yet received prophylaxis. 

Bottom line: This small study offers some assurance that early prophylaxis is okay, and a few prospective studies do exist. UCSF / San Francisco General is comfortable beginning chemical prophylaxis 36 hours postop, regardless of solid organ injury. Look for more guidance on this issue in the coming year or so. Until then, consider starting LMWH prophylaxis early to avoid complications from DVT or PE.

Reference: Thromboembolic prophylaxis with low-molecular-weight heparin in patients with blunt solid abdominal organ injuries undergoing nonoperative management: current practice and outcomes. J Trauma 70(1): 141-147, 2011.

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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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Q & A

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I always welcome any questions, comments or requests you may have! However, if you comment anonymously, I have no way or responding to you directly. Every once in a while, I’ll take a moment to answer any comments / questions I’ve received.

Regarding this post on performing retrograde urethrogram from 7 months ago, shadowboxer said:

“tried this. total flail. the ky makes the catheter tip syringe slide out of the foley. The contrast becomes too dilute. The material is too thick and when enough pressure to push it through the foley is placed, the foley, since it is now so slippery with the ky, flies out and gooey contrast sprayed all over the flouro tower. what a mess!!”

Bottom line: I reread my post, and I must have had a senior moment. I do not recommend using the foley catheter! The slip tip syringe goes straight into the meatus, and you then clamp the tip of the penis firmly with your fingers. Here’s how it should read, with the corrected section in bold:

The technique is simple. The following items are needed:

  • A urine specimen cup
  • A tube of KY jelly (not the little unit dose packs)
  • A bottle of renografin or ultravist contrast
  • A 50-60 cc Toomey syringe (slip-tip)
  • A fluoroscopy suite

Pour 25cc of contrast and 25cc of KY jelly in the specimen cup, cap it and shake well. Draw the contrast jelly up into the syringe. Place the tip of the syringe directly into the urethral meatus, make a circle with your thumb and index finger, and use that to clamp the end of the penis around the slip-tip. Pull the penis toward yourself to keep your hand away from the center of the xray field. Slowly inject all the contrast, watching the contrast column on the fluoro screen. Once there is easy flow into the bladder, you can stop the study. If you see extravasation into the soft tissues, stop the study and call Urology.

The key to this technique is the 50:50 KY/contrast mix, which is thin enough to flow but thick enough to keep from spraying all over. Also, the finger clamp technique is important, because the contrast will ooze out if you don’t do it tightly. However, if you’ve pulled the penis over to the side, any leakage will not contaminate the xray field.

I’ve personally used this technique about 50 times and have never had a problem.

Sorry, shadowboxer, hope you’ll try again with my revised / corrected technique. If you do, please let me know.