Monthly Archives: January 2014

How to survive a shark attack?

The easy answer is to stay out of the water. That takes all the fun out of life though, so there has to be a better answer. Sadly, once a shark has decided to attack, your chances of survival drastically decrease. Nature’s evolutionary killing machine is very good at its job, and even if you’re just injured, it’s usually not pretty. And the number of unprovoked attacks in Australia has increased significantly in the last 20 years, with 2000-2009 having nearly 3 times as many attacks as the decade from 1980-1989. Don’t think that your next beach trip will be a scene right out of JAWS though, as there are still only ~12 attacks per year in ‘Straya, and ~1 death per year. So how do you go about avoiding an attack? Based on this paper, there are differences in geography, season, and human behavior that might make a difference. Anything that can trend this number back down will make watersports safer. 

Certainly, the sharks historically known as dangerous are the ones to worry about. The white, bull, and tiger shark are the only species identified to cause fatalities in the last 20 years. All of those were from sharks longer than 2m as well. but don’t let the smaller ones fool you. The smallest shark involved in an incident was merely 0.4m long. Juvenile whites can be mistaken for whaler species, and a smaller bite doesn’t always mean a safer one. Wobbegong sharks have also been recorded as causing injuries. However, the white shark is still the most dangerous, comprising less than 1/3 of the attacks, but more than 2/3 of the fatalities.

The simple geographic answer is “don’t swim where the sharks are.” Well, that’s tough to do in Australia, where sharks have been seen swimming down the street after floods. The figure below shows the location of the 592 recorded unprovoked incidents over the 218 year span they’ve been keeping records. However, it there are safe spots. Many beaches in well populated areas have shark-control programs. I won’t get into the ethics behind culling, but the shark nets seem to be effective, and certainly are a simple method to cut attacks. However, as demonstrated in the article, people are moving and recreating in areas without shark-control in increasing numbers, and the number of attacks has gone up as the population grows into those areas. Also, the increase in watersports in brackish water has increased the number of attacks that are related to bull sharks. 

sharks

It is also often stated that being in the water at dawn and dusk increases your risk of attack. Well, based on the data in this paper, it can’t be proven or disproven. The overwhelming majority of cases occur from 7am to 8pm, but they don’t break down times down to seasons, so you can’t determine attacks based on sunrise and sunset.

Is there a seasonal variation then? Most attacks occur in the summer, but that’s when most people are in the water, so that’s not helpful. Sharks do show migratory patterns following their prey, and warmer water months still have more attacks. There has been an increase in cold water attacks though, as people are starting to don wetsuits to spend more time in the water. 49% of attacks in the last twenty years have been on people wearing a wetsuit. This is an interesting statistic, because the rates of attacks while diving have stayed stable, but the rates for attacks while surfing nearly doubled from preceding period. 

One important behavior that has been shown to increase the likelihood of an attack is being near their natural prey. Schools of fish slightly increase risks, but being near seals dramatically increases being attacked. So if you’ve got the option, don’t surf, swim, or dive near seal colonies. 

Victims were only aware of a shark in the vicinity about 20% of the time, so keeping an eye out may be of some use. Don’t expect much of a warning, either, as sharks “bumped” or swam very close to a victim before an attack only 14% of the time.

Unfortunately, there isn’t one simple answer on how to survive a shark attack.  Less than 10% of the incidents report fighting back. Gouging the eyes, hitting the gills, or shoving things in the mouth may help though, as it made the shark stop or leave about 2/3 of the time. I can’t imagine that nobody fought back in the other cases, so this is another area where the data isn’t definitive.

Still, as explained in the paper, you are more than 80 times more likely to drown than to die from a shark attack. The risks are still extremely low, but taking a few safety measures can make them even lower.

Changing patterns of shark attacks in Australian waters
http://www.publish.csiro.au/?paper=MF10181

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