Monthly Archives: January 2015

Fever in the returning traveler

The patient who returns from vacation with a fever is often a diagnostic dilemma. Unfortunately, up to 1 in 5 travelers to the developing world will get one within a few weeks of their trip. So how do you come up with a logical, evidence based diagnostic workup for a fever of unknown origin?
Thankfully, these authors reviewed the literature and came up with an easy to follow algorithm to work up a patient. It includes:

  • Taking a detailed history
    • Dates of travel
    • Exposures (Food, water, sex, animals, sick people, INSECTS)
    • Prophylaxis, either pretravel or during
    • Illnesses during the trip, and medications
    • Exposures after travel, as not all fevers come from the travel itself
  • Performing a thorough physical exam
    • Abdomen for hepatosplenomegaly
    • Eyes for conjunctivitis
    • Lymph nodes
    • Skin for rose spots, maculopapular rashes, petechiae, or purpura
    • Neurologic for AMS
  • Specific initial lab tests
    • CBC with manual diff
    • Chemistries and LFTs
    • Pancultures: stool, urine, blood
    • Urinalysis
    • Thin and thick blood smears
  • Knowlege of geographic distribution of diseases
    • Dengue and malaria are widespread
    • Plasmodium vivax in the New World, P. falciparum in Africa, and non-P. falciparum in Asia
    • Rickettsia, schistosomiasis, and filariasis in Africa
    • Enteric fevers (typhoid and paratyphoid) are common in South Central Asia
  • Knowlege of incubation period for diseases

table

Sadly, most of the evidence is consensus level or worse, so expect a lot of atypical presentations and results. It does make sense to not just fly off the handle and start ordering West Nile titers on everyone, but instead having a straightforward process to do it. They show this with three case vignettes that are great for adapting into some of your own simulation cases.

One last comment I have is that this paper is open access. That way, everyone can learn that a tourniquet test for dengue involves pumping a blood pressure cuff up to halfway between the patients systolic and diastolic pressure. It’s positive if they’ve got more than 20 petechiae/inch [square inch? -JH].

Fever in Returning Travelers: A Case-Based Approach
http://www.aafp.org/afp/2013/1015/p524.html

Drowning

Today’s paper is from the lovely EM residencies affiliated with Harvard. They wrote up a case report of a patient that was injured while boating, resulting in drowning.

First, let’s get one thing clear. There is no clinical entity known as near-drowning. While it is included in the title and referenced multiple times in the case report, this is the wrong terminology. As written in a followup letter to the editor, “In 2002, the World Congress on Drowning developed the following Utstein style definition for drowning: the process of experiencing respiratory impairment due to submersion or immersion in a liquid.” We need to have a standardized verbiage for these events so we can have better data collection and communication.

With that out-of-the-way, let’s get to the evidence in drowning, as this case report is surprisingly chock-full of tidbits of information.

First, if there is any possibility that there was an aspiration, the patient must be observed for 6 hours. Also consider the fact that 20% of nonfatal drownings have concomitant neurologic damage. Cardiac dysrhythmias should be evaluated for, as they can be both the cause of and an effect of drowning. If at any time their pulse ox, respirations, cardiac rhythm, or mental status changes, they must be reassessed with radiography and/or ABG.

It takes a surprisingly small volume of water to compromise surfactant. In fact, it just takes aspirating 1-3 mL/kg of body weight, which can be an exceedingly small amount in a child.  However, it takes significantly more liquid (11 mL/kg) to cause blood volume changes. If you’re thinking about electrolyte abnormalities, realized that 22 mL/kg is required for this, which implies it is unlikely to occur in an adult.

With drownings, you have good odds that alcohol or another intoxicant was involved.  Between 30 and 50% of them are attributed to alcohol, and if your blood alcohol level is >150mg/dL, your odds ratio of death is 37.4 over sober controls.

Don’t give empiric antibiotics unless they drowned in a septic tank or some other grossly contaminated body of water. However, if they show signs or symptoms of infection later, antibiotics are recommended.

Finally, and this is the major point of this case report, be very cognizant of respiratory decline. Patients can have either acute lung injury or adult respiratory distress syndrome after dying, and these conditions have high mortality. Apart from positive pressure ventilation, not much seems to help. Intubate patients as needed. Certainly you want to follow ARDSnet data and use lung protective tidal volumes (6mL/kg), and keep their oxygen saturation between 88-95% (or PaO2 between 55-80 on ABG). Unfortunately, the data isn’t great for using non-invasive positive pressure ventilation, but certainly it is unlikely to cause harm as long as it doesn’t delay intubation if needed. You can also consider fluid restriction as long as the patient has adequate perfusion, but realize this didn’t change the 60 day mortality.

Near Drowning and Adult Respiratory Distress Syndrome
http://www.ncbi.nlm.nih.gov/pubmed/24642043

Does that airbag really help?

Sorry for the long hiatus over the holidays. I wish I could say I was doing something fun and exotic, but instead I simply became the curriculum director at my current residency, which changed my workload quite a bit. That being said, back to the wilderness topics.

Since it’s winter, we are going to keep talking about avalanches. Since indications for resuscitation have been discussed before, now we will turn towards prevention. Two main ideas, first, avoid triggering an avalanche, and second, if you find yourself caught in one, try not to get buried. It makes sense, as the data from older studies is pretty clear that people who are buried die at a markedly higher rate than those who are not (52% vs 4%). What’s more, for those that are buried, the quicker they are found decreases their mortality, thus people buried less deep would likely have a higher survival rate.

Source: Hansi Heckmair/ABS

Enter airbags, which were invented to prevent this “critical burial” that causes increased mortality (critical meaning impairment of airways). They do this by basically making you much larger and more buoyant by inflating a large balloon that is strapped to your back. At least, that’s the theory. There wasn’t a lot of strong research devoted to them before implementation, and as they weren’t created by Roche, postmarketing research was lacking as well. Tie observer bias into this (people weren’t reporting near misses that didn’t involve airbags) and you are left with almost nothing of value to base recommendations on.

These authors wanted to fix that, so they did this study to determine the effectiveness of airbags based on preventing critical burial and mortality, as well as documenting frequency and causes of deployment failures. To do this, they looked at prior avalanche accident records from multiple countries, culling only worthwhile data that would show a difference between airbag users and nonusers. Thus, single victim events, small avalanches, or victims who weren’t seriously involved were removed in an attempt to reduce bias.

And once they crunched the numbers, they found out that airbags really do help. If you combine airbag failures with airbag inflations, the absolute risk reduction for critical burial is 29% (56%-27%), and the absolute mortality reduction is 17% (34%-17%). If you combine airbag failures with those not wearing airbags to begin with (why?), then risk reductions for critical burial and mortality are 35% and 23%, respectively. When you combine these values to adjusted mortality, you get a risk reduction of 11%, or a NNT of 9 for mortality with airbag use. Not too shabby.

Deployment failures occurred an alarming 20% of the time. Of these failures, 72% were attributed to operator error (not deploying them appropriately or incorrect maintenance). Slightly concerning, 12% of the failures involved destruction of the airbag during the avalanche. Of course, the absolute failure rate due to destruction or device failure is right at 5%.

So yes, if you’re going anywhere that there’s a risk of avalanches, you should wear an airbag. Also you should carry a beacon. And, like most other life saving measures, be they medical or technical, you’re only as good as what you do. Thus, read the instructions and know how to use it before you go out-of-bounds. However, this study did have a higher mortality of airbag users from prior studies (11% vs 3%), so don’t expect an airbag to make you immortal. Certainly, don’t do stupid things simply because you think you have a safety net (although it’s been shown that this doesn’t really occur). Of note, the usual problems with poor data due to non-standardized reporting as well as a low total number of victims apply to interpretation of this data.

The effectiveness of avalanche airbags
http://www.ncbi.nlm.nih.gov/pubmed/24909367