Pulmonary Embolism and DVT in Trauma

We have long assumed that pulmonary emboli start as clots in the deep veins of the legs (or pelvis), then break off and float into the branches of the pulmonary artery in the lungs. A huge industry has developed around how best to deal with or prevent this problem, including mechanical devices (sequential compression devices), chemical prophylaxis (heparin products), and physical devices (IVC filters).

The really interesting thing is that less than half of patients who are diagnosed with a pulmonary embolism have identifiable clots in their leg veins. In one study, 26 of 200 patients developed DVT and 4 had a PE. However, none of the DVT patients developed an embolism, and none of the embolism patients had a DVT! How can this kind of disparity be explained?

Researchers at the Massachusetts General Hospital retrospectively looked at the correlation between DVT and PE in trauma patients over a 3 year period. DVT was screened for on a weekly basis by duplex venous ultrsonagraphy. PE was diagnoses exclusively using CT scan of the chest, but also included the pelvic and leg veins to look for a source. A total of 247 patients underwent the CT study for PE and were included in the study.

Forty six patients had PE (39% central, 61% peripheral pulmonary arterial branches) and 18 had DVT (16 seen on the PE CT and 2 found by duplex). Of the 46 patients with PE, only 15% had DVT. All patient groups were similar with respect to injuries, injury severity, sex, anticoagulation and lengths of stay. Interestingly, 71% of PE patients with DVT had a central PE, but only 33% of patients without DVT had a central PE.

The authors propose 4 possible explanations for their findings:

  1. The diagnostics tools for detecting DVT are not very good. FALSE: CT evaluation is probably the “gold standard”, since venography has long since been abandoned
  2. Many clots originate in the upper extremities. FALSE: most centers do not detect many DVTs in the arms
  3. Leg clots do not break off to throw a PE, they dislodge cleanly and completely. FALSE: cadaver studies have not show this to be true
  4. Some clots may form on their own in the pulmonary artery due to endothelial inflammation or other unknown mechanisms. POSSIBLE

An invited critique scrutinizes the study’s use of diagnostics and the lack of hard evidence of clot formation in the lungs.

The bottom line: this is a very intriguing study that questions our assumptions about deep venous thrombosis and pulmonary embolism. More work will be done on this question, and I think the result will be a radical change in our use of anticoagulation and IVC filters over the next 3-5 years.

Velmahos, Spaniolas, Tabbara et al. Arch Surg. 2009; 144(10):928-932.

What You Need To Know About Falls From a Height

 Falls from a height can be either accidental or intentional (suicide attempt). There are several prognostic factors for survival that have been identified:

  • Height
  • Age
  • Type of surface
  • Body part that touches the ground first

Two other factors are important, but do not have a significant effect on mortality:

  • Circumstances of the fall (suicide, accident, escape)
  • Initial impact with an object before impacting the ground

Height. Overall, about half of victims die at the scene, and a total of 70% die before they reach the hospital. The median height leading to death is about 49 feet, or about 4 to 5 storeys. 100% of victims die after falling 85 feet, or about 8 storeys.

Age. Mortality increases with age due to pre-existing medical conditions and decreased physiologic reserve.

Type of surface. The type of surface struck (i.e. grass, water, construction debris) can also have an effect on secondary injuries and survival. Mortality after striking a hard surface is nearly double that of hitting a soft one (39% vs 22%)

Body part touching the ground first. The highest mortality is seen when the victim lands in a prone position (57%). Striking head first has the next highest mortality at 44%. The best striking position is feet first, with a mortality of 6%.

Circumstances of the fall. Suicide attempts have the highest death rate at 46%. This may be attributable to pre-planning, and the increased likelihood that the fall may lead to additional trauma mechanisms (struck by car after jumping from land bridge, drowning after jumping from bridge over water). Accidental falls have a lower 17% mortality.

Initial impact before final impact. Striking wires or scaffolding before the final impact is protective, decreasing the death rate from 37% to 15%.

It is important for the trauma professional to obtain as much information from bystanders or EMS as possible about the fall details. This will ultimately enable to trauma physician to pursue appropriate diagnostic techniques to pinpoint specific injuries associated with various types of falls.

Reference:

Crit Care Med 33(6): 1239-1242, 2005.

What Percent Pneumothorax Is It?

What percent pneumothorax?

Frequently, radiologists and trauma professionals are coerced into describing the size of a pneumothorax seen on chest xray in percentage terms. They may something like “the patient has a 30% pneumothorax.”

The truth is that one cannot estimate a 3D volume based on a 2D study like a conventional chest xray. Everyone has seen the patient who has no or a minimal pneumothorax on a supine chest xray, only to discover one of significant size with CT scan.

Very few centers have the software that can determine the percentage of chest volume taken up with air. There are only two percentages that can be determined by viewing a regular chest xray: 0% and 100%. Obviously, 0% means no visible pneumothorax, and 100% means complete collapse. Even 100% doesn’t really look like 100% because the completely collapsed lung takes up some space. See the xray at the top for a 100% pneumothorax.

If you line up 10 trauma professionals and show them a chest xray with a pneumothorax, you will get 10 different estimates of their size. And there aren’t any guidelines as to what size demands chest tube insertion and what size can be watched.

The solution is to be as quantitative as possible. Describe the pneumothorax in terms of the maximum distance the edge of the lung is from the inside of the chest wall, and which intercostal space the pneumothorax extends to. So instead of saying “the patient has a 25% pneumo,” say “the pneumothorax is 1 cm wide and extends from the apex to the fifth intercostal space on an upright film.”

How To Rapidly Reverse Coumadin in Head-Injured Patients

A growing number of adults, usually elderly, are taking Coumadin (warfarin) to manage chronic medical conditions or deep venous thrombosis. While warfarin is a very useful drug for these problems, it is notoriously difficult to maintain tight control of INR. If an individual on warfarin is involved in a fall or vehicular crash, bleeding complications can become life-threatening. A recent Journal of Trauma article shows that mortality more than doubles in elderly patient who are admitted awake after just falling from standing.

The key is to rapidly reverse an elevated INR. Vitamin K can be used to increase biological activity of several clotting factors, but this occurs over several hours. Plasma is also used, but there are several considerations. Many hospitals have only frozen plasma, and there may be a delay of 30 to 45 minutes to thaw it. Multiple units may need to be transfused in order to normalize higher INRs, which may cause volume overload in elderly patients with cardiovascular disease.

More recently, activated Factor VII (NovoSeven) has been used to aid rapid reversal of the INR. NovoSeven is FDA approved for only the following uses:

  • Bleeding or surgery in hemophiliacs
  • Bleeding or surgery in congenital Factor VII deficiency

Use of NovoSeven for rapid reversal of warfarin is an off-label use, and physicians must weigh the risks and benefits prior to use. It is also very costly, about $7000 per vial. To download a printable copy of our protocol, click here.


PROTOCOL – PATIENTS ON WARFARIN WITH HEAD INJURY AND ABNORMAL CT SCAN

Check INR. Goal INR is 1.2-1.4

If > 1.4

  • Give Vitamin K 10 mg IV
  • Transfuse thawed plasma 15ml/kg (4-6 units)
  • Consider NovoSeven Weight <= 100kg – give 2mg IV

Repeat INR at 2hrs, 4hrs, 12hrs and 24 hrs after NovoSeven administration.

If INR increases to > 1.4, repeat plasma transfusion as needed.


Related post:

Reference: J Trauma. 2009 Jun;66(6):1518-22; discussion 1523-4.

NOTE: This guideline is based on protocols in use at the Regions Hospital Level I Adult and Pediatric Trauma Centers. As with any potent drugs or procedures, undesired side-effects may occur. The individual physician prescribing these medications or procedures is solely responsible for the safety of his or her individual patient.

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