Page 53 - Journal of Special Operations Medicine - Summer 2016

the appliance and the instrument. Rohrer and Bulard weight of a typical autoclave. Their disadvantage is that
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were able to overcome this problem by insulating their they must be properly mixed in the correct concentra-
metal instruments with a radar absorbent material. Al- tion, and most have a limited storage and use time.
though radar absorbent material is likely to be difficult
to obtain, a cursory search of the Internet showed that The two most common forms of chemical disinfection
microwave absorbable material could be obtained in are 2% glutaraldehyde and 6% hydrogen peroxide.
bulk 9-inch sheets for around US$180. In light of this Either agent can achieve high level disinfection after
evidence, commercial microwave ovens present a novel 30 minutes of immersion in a chemical bath with the
and field expedient alternative to traditional sterilization proper concentrations as mentioned earlier.
methods; however, this has not been approved by the
US Food and Drug Administration, and further study 1. Glutaraldehyde is commercially available in a 2%
is needed to establish a protocol for metal instruments. aqueous solution, but it comes in a kit that requires the
addition of a buffer in powder or liquid form to become
activated. Immersion for 30 minutes is enough to pro-
Disinfection
vide high-level disinfection, but it can also provide ster-
Recall that by definition, there are two types of disinfec- ilization if left for a total soak time of 10 hours. Ideally
tants: high level and low level. High-level disinfection after immersion instruments should be rinsed with ster-
kills all microorganisms except spores; low-level disin- ile water to remove any excess solution.
fection can kill most bacteria, some viruses, and some
fungi, but also has no effect on spores. Glutaraldehyde is a lucrative option since it can provide
both high-level disinfection and sterilization, but it does
High-Level Disinfection by Boiling have some significant drawbacks. First, once activated,
Sterilization is the preferred method for any cutting, the solution should not be kept for more than 2 weeks.
piercing, or invasive instrument. But if sterilization is not Second, it tends to be expensive. And third, the solution
available or not practical, then high-level disinfection by gives off a toxic vapor that prevents it from being used
boiling is a reasonable alternative. This is achieved by in enclosed spaces, and skin contact should be avoided.
1
placing instruments in boiling water for a minimum of
20 minutes, and it is an effective and reliable method 2. Hydrogen peroxide exerts its disinfectant potential
for inactivating microbes, including HIV and hepatitis B though its oxidizing ability. This agent is often readily
virus. At 1 atmosphere (1 ATM) of pressure (sea level), available over-the-counter; however, a 6% concentra-
water boils a constant temperature of 100°C (212°F). tion is required for disinfection. In the United States,
However, as you increase in altitude, you thereby de- hydrogen peroxide can be found in just about any drug
crease the atmospheric pressure, and water will boil at store, but the concentration is rarely found above 3%.
a lower temperature. We could not find any data that The common form stocked in the standard MES set is
suggest that this does or does not affect the reliability of 3% as well. To ensure the 6% recommended solution,
boiling disinfection. Given the current high-altitude op- it can be purchased in a concentrated 30% form, and
erations in Afghanistan, the affects of altitude on boiling mixed with a combination of 1 part hydrogen peroxide
point depression should be taken into consideration if to 4 parts boiled water. Once again, the recommended
choosing to rely on boiling disinfection. soak time is 30 minutes. Due to its strong oxidizing abil-
ity, it should not be used on copper, aluminum, zinc, or
High-Level Chemical Disinfection brass.
If sterilization is not available and boiling disinfection
is not available, then high-level chemical disinfection In addition to the WHO’s recommendations of Glutar-
can be considered for instruments as a method of last aldehyde and Hydrogen peroxide, the United Nations
resort. It should be noted, however, that it is not recom- High Commissioner for Refugees also recommends the
mended for hollow needles or syringes. This method use to the following alternative agents :
1
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should only be used if the concentration of the chemi-
cal bath can be ensured, and all instruments must be 3. Chloramine: Usually found in powder or tablet form,
thoroughly cleaned of gross organic material prior to chloramine can be used for water purification, as a sur-
emersion in the chemical bath. A thorough cleaning is face wound antiseptic, and as a disinfectant for surgical
required to ensure adequate chemical penetration, and instruments and medical surfaces. It can also be found
instruments should be towel dried of excess water be- commercially in the form of aquarium cleaner or wa-
fore emersion to prevent unintentional dilution of the ter purification tablets. It is typically found in 250mg,
chemical bath. Chemical disinfection has a weight ad- 500mg, or 1g tablets. As other dis infectants, it must
vantage over steam sterilization, in that 1L of liquid dis- first be made into a solution, preferably with boiled
infectant weights approximately 2.2lb, versus the 43lb water, and only in the recommended concentrations.

Field Sterilization in the Austere Environment 39