All posts by TheTraumaPro

Pneumocephalus And Air Transport

Everybody remembers Boyle’s law, right?

Volume of a gas = k / Pressure     (where K is a constant)

Which means that, as pressure goes down, the volume of a gas increases. This is important for patients who have a pneumothorax and get on an airplane. As the plane ascends the pneumothorax gets bigger and they may have serious problems. Click here to see guidelines on flying after pneumothorax.

Well, what happens if you have air bubbles in your head (pneumocephalus)? Some patients with serious head injury may have this condition but need to be transported by air to definitive care. Most recently, this has been a consideration in military medical evacuation flights out of Afghanistan.

A paper from the US Army and Air Force studied 21 soldiers (small series) who were evacuated by air with known pneumocephalus. The volume of air was estimated by CT prior to transport, and ranged from less than 1ml to 43ml. None of the patients suffered neurologic deterioration during flight, and 3 who had external ventricular drainage (EVD) showed no significant change in intracranial pressure.

Bottom line: Only two cases of tension pneumocephalus have ever been described. Neither occurred in trauma patients. While expanding pneumothorax may be a problem during commercial flight, there is still little data on tension pneumocephalus. It works for the military because the soldiers are in a flying ICU and can be treated immediately if a problem develops. Not so in commercial aircraft, so beware! But remember, medical helicopters don’t fly high enough to create tension problems in any part of the body, so they are not an issue.

Related posts:

Reference: Aeromedical evacuation of patients with pneumocephalus: outcomes in 21 cases. Aviation Space Env Med 79(1):30-35, 2008.

Cricothyroidotomy Using The Scalpel-Bougie Technique

Here’s a video from our colleagues in Australia that shows a slick way of performing a surgical cricothyroidotomy. The number of required instruments is the bare minimum: a scalpel and a bougie. I have not tried this technique, but it looks like it would be very handy when dealing with obese patients with a deep neck. It would also be useful to prehospital providers who are credentialed for crichs and are faced with a difficult airway.

If any of you have used this technique, please leave a comment for us!

Damage Control Dressing: The ABThera (Video)

In the late 1980’s, when we started the work that would be published in the first damage control paper from Penn, we used the vacuum pack dressing. This was first described in a paper from the University of Tennessee at Chattanooga in 1995. Prior to that, the so-called Bogota bag was the usual technique. This consisted of slicing opening up a sterile IV bag (either the standard 1 liter or the urology 3 liter bag for big jobs) and sewing it into the wound. This worked, but it freaked out the nurses, who could see the intestines through the print on the clear plastic bag.

The vacuum pack was patient friendly, with a layer of plastic on the bottom, some absorbent towels in the middle with a drain in place to remove fluid and apply suction, and an adherent plastic layer on top to keep the bed clean. As you can imagine, this was a little complicated to apply correctly. One misstep and things stuck to the bowel or leaked out onto the bed.

In the past few years, a commercial product was developed that incorporated all these principles and was easy to apply. This is the KCI ABThera (note: I have no financial interest in KCI or this product; I just wish I had invented it). The only downside is that there is a small learning curve when first using this product.

The video above shows a demonstration of the application on an abdominal mannikin. It is not as slick as the company videos, but I think it’s more practical, with some good tips.

References:

  • Damage control: an approach for improved survival in exsanguinating penetrating abdominal injury. J Trauma 35(3):375-382, 1993.
  • Temporary closure of open abdominal wounds. Am Surg 61(1):30-35, 1995.

Q&A: Prothrombin Complex Concentrate

An anonymous user recently asked about decision-making with regard to anticoagulation reversal. Specifically, they were interested in using prothrombin complex concentrate (PCC) vs activated Factor VII (FVIIa). I’ve done a little homework on this question, and am going to include some information on the use of fresh frozen plasma (FFP), too.

Unfortunately, there’s not a lot of good data out there comparing the three. Enthusiasm for using FVIIa is waning because it is extremely expensive and the risk/benefit ratio is becoming clearer with time (more risk and less benefit than originally thought). PCC is attractive because it provides most of the same coagulation factors as FFP, but with far less volume. However, it is very expensive, too.

What to do? One of the best papers out there comes from the UK, where they looked at the cost effectiveness of PCC vs FFP in warfarin reversal. They reviewed a year’s worth of National Health Service patients from the standpoint of what it costs to gain a year of life after hemorrhage. They found that the cost was £1000-£2000 per life-year, and £3000 per quality adjusted life-year. This was more cost effective than using FFP. Unfortunately, I do not have access to the full text to review the details.

PCC has only been compared to FFP in the treatment of hemophilia, so it’s not possible to draw any conclusions. The course of therapy for perioperative management of hemophiliacs is lengthy (meaning hideously expensive), and there was a cost-savings seen ($400,000)! Since we use only short duration therapy in trauma patients, the savings will be far less.

Bottom line: PCC is probably as effective as FFP, with less risk of volume overload. It is probably more cost effective as well. As the population of people that are placed on warfarin ages and becomes more susceptible to volume overload from plasma infusions, I think that PCC is going to become the reversal agent of choice. Use of Factor VIIa will continue to wane. However, someone needs to do some really good studies so we don’t get suckered.

Related posts:

Reference: Modeling the cost-effectiveness of prothrombin complex concentrate compared with fresh frozen plasma in emergency warfarin reversal in the United Kingdom. Clinical Therapeutics 32(14):2478-2493, 2010.