Monthly Archives: November 2013

What to do for bug bites?

Face it. Except for the very lucky, few of us are able to escape biting insects. After getting bit, the range of reactions is immense; from no reaction to anaphylaxis. Thankfully, most simply have mild pruritis and urticaria. But how are we supposed to treat these?

This review article from the UK lays out the evidence behind all the common treatments for bug bites. Here is a summary:

  • Oral antihistamines are recommended, but data is lacking. A review consisting mostly of multiple studies from one group in Finland showed them to be effective.
  • Use non-sedating antihistamines during the daytime, and sedating ones as night.
  • Topical antihistamines don’t work well, can cause sensitization, and aren’t recommended for longer than 3 days.
  • Topical corticosteroids are poorly studied but may be effective.
  • Topical corticosteroids shouldn’t be used on broken skin or on the face.
  • Oral corticosteroids are used for severe urticaria, but no studies have been found to support this.
  • Use the lowest dose for the shortest time possible for oral corticosteroids.
  • OTC analgesics can be used for pain, but topical anesthetics can cause sensitization.
  • Calamine isn’t the slightest bit effective, so don’t use it.
  • Counter-irritants (such as dilute ammonium) may be effective based on one double blind RCT.
  • Topical antiseptics after bites are probably overkill.
  • Generalized symptoms or redness/swelling over 10cm should be referred to an allergist.
  • Secondary infections should be treated with antibiotics.
  • Treat anaphylaxis appropriately.

Nothing earth shattering here, but maybe this will prevent unnecessary topical treatments which are often ineffective and possibly harmful. I do wish more people would recommend loratidine or cetirizine for this instead of diphenhydramine. The sedating effects as well as the duration of effect would tend to recommend the newer, now OTC agents, but I still see most everyone giving patients prescriptions for Benadryl®.

Management of simple insect bites: Where’s the evidence?
http://dtb.bmj.com/content/50/4/45.full

Do air pockets help avalanche survival?

The theoretical is obvious. If you have an air pocket you can breathe into after an avalanche, you should survive longer than if you don’t. This study intended to ascertain if this was true, as their hypothesis was that air pocket subjects would develop hypoxia, hypercarbia, and hypothermia, while those breathing outside air would simply develop hypothermia. Now, they did their study on piglets, as it is hard to get IRB approval for studies where the endpoint is asystole.

While the premise is good, unfortunately conditions outside the control of the researchers severely limited their study.

Eight piglets per group plus five pilot animals were planned; because of massive sensational media coverage, protests by animal activists and threats of violence and death towards the study team the study had to be terminated prematurely and only eight animal experiments were conducted

So they went ahead and used the 8, with 3 breathing from a 1L air pocket, 2 breathing from a 2L air pocket, and 3 breathing ambient air. All of them were anesthetized, intubated, and packed in snow during the measurement phase of the study.

A bigger problem with the study is what they did with their data. After collecting core temperature, cardiac output, paO2, paCO2, pH, and potassium (?), they then combined the 1L and 2L air pocket groups into one due to small sample size. They do include their data tables if you want to look at it yourself. It is full of interesting findings, such as measurable cardiac output on 6 of the 8 pigs during “asystole”. You’ll probably need to look at the raw data anyway, as the results figure online and in the pdf is impossible to read. You cannot tell which line is supposed to be which by looking at them.

The results were along the lines of what they were expecting. Yes, piglets with air pockets do worse than piglets with ambient air. And perhaps surprisingly, piglets with an air pocket develop hypoxia and loss of cardiac output relatively quickly (~10 min). The authors thankfully describe all the limitations of the study, and the difficulty in generalizing this to humans (surface ratio differences, general anesthetics present, higher metabolic rates, etc). While good proof of concept and need for further study, I’m not exactly sure what got this published in Resuscitation.

Factors affecting survival from avalanche burial–a randomised prospective porcine pilot study
http://www.ncbi.nlm.nih.gov/pubmed/22771873