Page 51 - Journal of Special Operations Medicine - Summer 2016

Disinfectant versus antiseptic: A disinfectant is an agent Steam Sterilization
intended to be used on surfaces and equipment, but not Steam sterilization, known as autoclaving, is the recom-
skin, as they can cause damage to living tissue. Antisep- mended method for sterilization of medical equipment
tics are agents that are intended to be applied to skin that is both heat and moisture tolerant. This form of
1,2
and tissue but are inappropriate for cleaning equipment sterilization uses moist heat in the form of steam under
and surfaces. pressure. It differs from a simple open container boil-
ing technique since the addition of pressure allows the
autoclave to achieve temperatures beyond the boiling
Requirements
point of water. These high temperatures allow the auto-
Not all medical equipment needs to be sterilized, but it is clave to kill microorganisms in a relatively short period
important to identify whether cleaning, disinfection, or of time. It is a dependable form of field sterilization;
sterilization of the item is required based on that item’s however, its effectiveness is limited by steam, pressure,
intended use. In ideal situations, items that come in temperature, and time. 8
8
contact with unbroken skin (stethoscopes, blood pres-
sure cuffs) should be cleaned with low-level disinfection. An autoclave must be able to achieve and maintain a
Items that touch but do not penetrate mucus membranes temperature of 121°C (250°F) or 132°C (270°F) to have
(endotracheal tubes, laryngoscopes) should be sterilized affective antimicrobial activity.
but can be cleaned with high-level disinfection if steril-
ization is not feasible. Medical instruments that pierce There is disparity over the proper exposure time re-
human tissue (scalpels, forceps, cricothyroid hooks) quired to affectively sterilize equipment. The CDC
must be sterilized between each patient contact. 1,7,8 Bear and the Special Operations Forces Medical Handbook
in mind that this is the recommendation for fixed hos- recommend 30 minutes at 121°C in a gravity displace-
pitals in a garrison setting. The operational setting is ment autoclave or 4 minutes at 132°C in a prevacuum
dictated by the tactical and logistical limitations, while sterilizer. 8,13 However, according to the WHO, a mini-
simultaneously conforming to some semblance of a pol- mum duration of 15 minutes at a temperature of 121°C
icy for safe instrument reuse. (250°F) seems to be an appropriate cleaning time. If a
formal autoclave is not available, any commercial pres-
Simply put, cleaning and sterilization/disinfection of in- sure cooker can suffice. 8
struments represent a process that makes them safe for
medical personnel to handle and safe to reuse on a pa- The autoclave can potentiate logistical constraints since
tient. Figure 1 shows a suggested instrument processing it requires a large amount of water to operate. Any
6
cycle. source of potable water can be used, but nondistilled
water can cause ionized salts like calcium, magnesium,
and iron to precipitate and deposit on lower points of the
Sterilizers autoclave. For this reason, most autoclave manufactur-
ers recommend the use of distilled water for operation.
Sterilization In the garrison hospital or clinic setting, this is usually
Several methods are available to achieve instrument not a problem. In the field environment, however, large
sterilization; however, most are not accessible in the op- quantities of distilled water are not available. For this
erational environment. Therefore, we will focus on the reason, the US Army Medical Materiel Agency National
two forms that are likely to be available in the deployed Maintenance Program recommends that local potable
setting: steam sterilization and dry heat sterilization. water may be used for daily operations; however, the
unit should be cleaned periodically with a diluted vin-
Figure 1 Sample decontamination process. egar and water solution (1 quart vinegar:4 gallons of
water) to remove any ion salt buildup. If your kit in-
16
cludes an electrical autoclave, then the electrical heating
element should be cleaned in a similar fashion, as ion
salts can deposit there as well.

Another logistical constraint of the sterilizer is its
weight. Depending on its size, a standard unit can weigh
between 11 and 43lb. Obviously, smaller units weight
less, but this comes as a tradeoff for its reduced instru-
ment capacity. Nevertheless, the steam sterilizer’s size
and weight make it ill-suited for a portable devise and is
best used at the Role 1 facility or higher.

Field Sterilization in the Austere Environment 37