Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

187

Section V: Environmental Medicine

can minimize these problems and prolong the duration of effectiveness. Neither permethrin nor picaridin has the same affinity for synthetics and can be used safely around nylon sleeping bags and tent screens. Permethrin is typically used only on clothing and equipment, not directly on the skin. Although there are numerous other products and claims on the market, there really are no other agents effective enough to recommend in the prevention of disease. Lemon eucalyptus is another popular insect repellant, but it does not enjoy the same effectiveness against mosquitos and sand flies as the other four. The various herbs and odors like citronella and garlic are signifi- cantly less effective. Risk Versus Benefit If a toxin is known to be particularly dangerous, early evacuation to medical care can be lifesaving. Examples include acetaminophen in toxic doses and several common mushroom species. In the remote setting where evacuation will be delayed or impossible, it is well worth reminding expedi- tion members of the extreme consequence of a medication or culinary mistake. In years past, the induction of vomiting was considered an emergency treatment for drug overdose and ingested toxins. We now recognize that vomiting is a high-risk activity in any envi- ronment and the benefit is questionable, even where evacuation is not an option. Preservation of the airway takes priority. Some authorities are recommending the appli- cation of a pressure bandage for North American snake envenomation on extremities. The idea is to reduce the systemic spread of the toxin through lymphatic drainage without obstructing arterial or venous blood flow. In the field, the correct pres- sure is difficult to achieve and maintain, increas- ing the risk of local tissue damage from ischemia and sequestration of the toxin. Because fewer than 1 in 1,000 people die of pit viper envenomation in North America, and all but zero from coral snakes, the benefit of restricting systemic dilu- tion does not outweigh the risk of increased local tissue destruction in the extremity. In other parts

of the world where snake venom is more potent or contains a greater percentage of neurotoxin, a pressure bandage is more clearly worth the associ- ated risks.

Pigmy Rattlesnake When discussing arthropod disease vectors, many people express concern about the possible toxic side effects of DEET as an insect repellent. It should be reassuring that DEET has been exten- sively studied and found to be remarkably safe and effective in concentrations to the low 30% range. Some formulations use vehicles that are more resilient to the environment and allow for release over time, thus less likely to be absorbed and requiring fewer applications. The minimal risk in its use is well outweighed by the benefit of avoiding devastating diseases like filariasis, malaria, Lyme, babesiosis, West Nile, and dozens of others.

General Principles

Toxins and Envenomations

28

High Risk Problem : • Persistent shock, respiratory distress, altered mental status

• Known dangerous exposure • High risk wounds or burns

• Cannot maintain body core temperature • Cannot maintain hydration and calories • The patient is getting worse

©2018WMA

The same endorsement is warranted for Picaridin, which has been used extensively and safely throughout the world for the past three decades and is as effective as DEET in similar