Category Archives: Macgyvering

Is there anything magnesium can’t do?

I’ve often extolled the virtues of magnesium to my residents as well as on twitter. It’s a sign of a well seasoned emergency physician to take any medical problem, and say “a little magnesium couldn’t hurt.”

In this instance, a group of physicians in Bhutan had a patient with classic signs of tetanus and an absence of tetanus vaccination. He was given typical antitetanus serum, antibiotics, benzodiazepines, and opiate analgesics. The spasms continued through high doses of benzos (80mg in 24 hours), and on day 14 they decided to start magnesium sulfate for spasms. After 3 days of treatment, it became the only medication the patient was taking. He ended up getting it for 20 days, and did reasonably well as far as one can tell reading the case report.

But what made them try it? Only 2 other people at that hospital had ever been treated for tetanus with magnesium, and both of them died. This is compounded with that hospital’s lack of  laboratory testing for serum magnesium level. Still, they did it, and by only following vital signs, sedation level, and deep tendon reflexes.

What may be surprising to many is that prior to this case report, a double blinded RCT of magnesium for the treatment of tetanus was performed on 195 patients. Thus, the authors weren’t completely off their rocker for attempting this treatment, novel as it may be to most.

Of course, the mechanism behind why this works is unclear. And there isn’t a clear indication as to why this is any better a treatment than typical neuromuscular blockade and sedation. Certainly, the toxicity of magnesium at high levels is well-known, I only consider this as one of those last-ditch efforts when standard treatment isn’t available or isn’t working. Even then, I would still prefer having lab testing to help guide treatment.

Survival of a Patient With Tetanus in Bhutan Using a Magnesium Infusion Managed Only by Clinical Signs
http://www.ncbi.nlm.nih.gov/pubmed/24792133

Ranger IVs decrease flow

When you’re out in the field, IV access is precious. So you do everything you can to prevent losing a good line. In concept, Ranger IVs are perfect. They are a ruggedized field IV system in which an IV is started, and then converted to saline lock. This is secured to the patient using a clear dressing (tegaderm or the like).  A second line of the same gauge  is then placed through the hub of the saline lock. This system then allows for a quick release valve of sorts. In essence, if the tubing gets snagged and pulls out, the saline lock remains, and only the second line is removed. Then all you have to do is put the second line (or a new one) back into the saline lock instead of starting a new IV.

This is the same logic I use when I teach my residents to not tape the chest tube to the collecting system. If someone trips over the tubing, it simply disconnects, and you just reattach it. If they’re attached, then you pull out the chest tube, requiring another invasive procedure.

Now, the tactical combat casualty care (TCCC) guidelines recommend giving those patients with hemorrhage and signs of shock a 500mL bolus as quickly as possible using the 18 gauge needles they carry. 18s are easier to start than 14s or 16s, and in the interest of carrying as little as possible they are what is used by the military. Since they’re already starting out with a rate limiting step by using a smaller IV, the authors wanted to know if the Ranger IV setup further limited the rate of the infusion.

Well of course it did. Anybody that works in critical care knows that putting one of those luer lock adapters on your resuscitation line will do two things. Get you yelled at by someone, and slow down the rate of your rapid infusion. But is it a significant amount, both clinically and statistically?

They used two setups, one with a hard needle (variant 1), and one with a catheter (variant 2), and a control of a normal catheter. The hard needle was the slowest, taking 14:50 for a 500mL bolus of LR, compared to 9:33 for the control, and 12:20 for variant 2. When hextend was used, the difference was even more pronounced. The control took 24:39, and variant 2 took 39:46. Variant 1 took more than twice as long as the control, at 49:32.

If pressure infusion bags were used, the bolus times were markedly decreased. LR times were 2:56, 4:23, and 3:49 (control, V1, V2), and hextend took 5:26, 9:08, and 7:35 respectively.

These results were stastically significant, and the point can be made that they’re clinically significant, at least as far as gravity fed lines are concerned. Certainly, three take home points can be made from this.

  1. If you’re going to use a ruggedized IV, use the catheter instead of a hard needle. It’s certainly safer, and it flows faster as well.
  2. The ruggedized IV shouldn’t be used for bolus with gravity alone.
  3. Even a normal 18 gauge delivers 6% hetastarch slowly, so those truly in shock and receiving high viscosity fluids need a pressure bag setup.

Evaluation of Fluid Bolus Administration Rates Using Ruggedized Field Intravenous Systems
http://www.wemjournal.org/article/S1080-6032(13)00379-7/abstract

Space blankets are worthless

Well, that’s not entirely true. They just aren’t good at being blankets. They fell out of favor quickly in hospital use, but survivalists still advocate for their use in wilderness settings. There’s at least one ultramarathon that makes participants carry one at all times. Why do they do this?

Space blankets came into vogue during the 60s and 70s, as a response to the “space race”. Anything that had to do with interstellar travel was popular, and out of that technology boom came the thin plastic coated with metal on one side.

They work quite well in space, since they’re small, weigh very little, and reflect radiated heat. Well, they work well on equipment, and only for keeping it cool. Heat from the sun is effectively reflected by the blankets. The problem is, humans don’t radiate much. Most heat loss is by convection, and the space blanket does little for this outside of being a wind break.

An even funnier consideration is referenced in the paper as well. The blankets only reflect heat on the size that has been metallized. Since this is usually only one side, and often clear plastic is used, you have a 50/50 shot of putting it on backwards if you’re not careful, and not reflecting any heat back to you. All of the negatives of looking silly without any of the benefits.

Now that the usefulness of the metal has been show to be invalid, let’s talk to the other putative benefits of space blankets. They can be made into shelters, rain catchers, water-repellent devices such as ponchos and boot liners, and all sorts of first aid items, from wraps to slings to wound dressings. Truth be told, a space blanket would probably work in that situation. A trash bag of any decent thickness would work just as well, and cost a whole lot less. You could get them in fancy colors if you wanted to use them as a signal in snow, and they come in multiple sizes.

Sure, the reflective side of the blanket could serve as a signal, but you’ve already got a mirror on you. (You DO have a signal mirror, don’t you?) If you’ve got one in your pack, don’t throw it out just yet though. You could always use it in a pinch, as long as it hasn’t become stuck to itself by prolonged storage. You might want to check before the next hike though.

So if your friend finishes a road race and is worried about getting cool too fast, give them a jacket. And if you’re in an emergency department and the patient is cold, give them a warm blanket.

Hypothermia and the use of space blankets: a literature review.
http://www.ncbi.nlm.nih.gov/pubmed/9325662

Surgical airways in the field?

Surgical airways have fallen out of favor in the hospital setting due to the advent of RSI and supraglottic airway devices, and now represent less than 3% of attempted intubations. In the prehospital setting, they can represent up to nearly 15% of attempts, however. It’s been said that the only absolute contraindication to cricothyrotomy is securing the airway by some other means. Even with the A in ABC taking a backseat recently, there are certainly circumstances that require definitive airways. Accomplishing this task while in an austere environment adds more difficulty to the equation.

So how skilled are providers at performing surgical airways in the pre-hospital environment? And what differences are there to devices and techniques in the austere setting, versus in a hospital? The authors of this article set out to find those answers. The impetus appeared to be a case report published in the same issue of Wilderness & Environmental Medicine by one of the authors of the review article.

The better part of the article is where it discusses the improvised techniques for the austere environment. Lots of items have been used in place of standard items, including: 3 mL syringe barrels (modified by cutting), nasal specula, straws from sports bottles, and ETT, as well as devices made specifically for surgical airways.  There may be anecdotes about using pen barrels, but nobody has bothered to publish a case report on an actual patient yet. Don’t fret though, if you want to be the first, somebody else has done the legwork on which ones to use, namely: 

The 2 pens ultimately deemed acceptable were the Baron retractable ballpoint pen and the Bic Soft Feel Jumbo.

Importantly, they point out that using the spike from an IV drip chamber will only work if you’ve got a jet ventilator. The inner diameter simply doesn’t allow proper ventilation.  I’m guessing if you thought to carry one of those into the wilderness, you’ve probably got better equipment to do a proper surgical airway. Likewise, needle crics may allow you to oxygenate, but you will not be able to ventilate, so at best they would be temporizing. Continuing the theme of improvising, the authors also describe using a bent 14 gauge needle as a makeshift hook, but sadly not how to make one.

Moving on to how successful the techniques are, in a review of 13 aeromedical papers on crics, the authors reported a 97% success rate on 296 patients, but they don’t break down physician vs flight nurse vs paramedic. A second review of ground EMS papers shows a lower rate of success at 89% for 405 patients, and this too includes all comers. A meta-analysis performed by other authors and referenced here showed no difference between flight and ground, but did show needle crics were much less successful at 66%, compared to the 90% for standard surgical airways.

Like many review articles, they have plenty of dry explanations of background, landmarks, indications, and contraindications. They review the incidence using prehospital and military literature, which is where the aforementioned statistics come from. They also mention that only one case report in the wilderness setting, also previously mentioned. There is then a table describing 12 current techniques for surgical airways. Taking up an entire page, it is a good primer, but not detailed enough to be your only source.

The authors recommend that providers pick a technique, and train in it often. Practicing less frequently than every 6 months leads to decreased skill maintenance, and perhaps training is needed as often as every month. Fidelity is important, as live-tissue models, and fresh cadaver specimens are much more realistic than mannequins. These recommendations are valid, as you don’t want to be trying something for the first time, when all you’ve got is what’s in your pack.

Optimizing emergent surgical cricothyrotomy for use in austere environments.
http://www.ncbi.nlm.nih.gov/pubmed/23062323