Page 93 - Journal of Special Operations Medicine - Summer 2016

more susceptible. Susceptibility is not existent until the of this work was pioneered by Dowd and Dobie in the
age of 2 years, peaks at about 12 years of age, then typi- 1960s and an element of cognitive behavioral therapy
cally declines with advancing age. Women tend to be was incorporated. Unfortunately, these desensitization
more susceptible than men, and pregnant women are treatments are not as effective in a maritime environ-
particularly susceptible. People who suffer from mi- ment. This is felt to be due to the largely unpredictable
graines are more susceptible, as are those with disease or motion that can be experienced in this setting.
illness that alters vestibular or visual sensory cues that
may make the person more sensitive to head motion and Nonpharmacological Treatment
visual stimulation. It has been reported that a person’s Various nonpharmacological options have been ex-
expectations and prior experiences may affect risk of plored for the treatment and prevention of motion sick-
motion sickness; in some cases, people can develop an ness. Ginger is a popular alternative medicine used for
almost anticipatory sense of motion sickness. motion sickness. One Naval study found that 1–2g of
ginger had some benefit in preventing motion sickness. 5
Environmental factors play a major role in motion
sickness. The type of motion can be a factor, with low- Acupressure has been purported to be useful in prevent-
frequency lateral and vertical motion being particularly ing motion sickness. According to the theory, pressure at
stimulating. Body position also plays a role: lying down the P6 point on the flexor surface of the wrist can reduce
1
decreases susceptibility and onset of motion sickness. symptoms. Some research seems to demonstrate a ben-
Many people feel food is a protection against motion efit, whereas other data do not. The role of acupressure
6
sickness, but the research regarding this is conflicted. in an operational setting is likely limited.

Incidence Medication
The incidence of motion sickness depends entirely on A variety of medications have been used to treat and
the intensity, duration, and type of motion that people prevent motion sickness. The majority of these drugs
are exposed to. Very few people are not susceptible. For are hypothesized to reduce the conflicting sensory in-
instance, in a study of 466 Royal Navy personnel, 4% formation by suppressing activity with the labyrinthine
were occasionally sick in calm seas, whereas in rough system. Despite the common nature of motion sickness,
sea states, 6% were always sick, 16% were often sick, the research and trials tend to involve small numbers of
and 44% were occasionally sick. 3 patients. There are also very few head-to-head trials of
medications.
Prophylactic Treatment
Drugs classified as antihistamines probably are effective
Because of the common nature of motion sickness, a va- because of their anticholinergic effects. Several medica-
riety of treatments have been historically used to treat it. tions in this category have been used, but the two most
It is clear that medication is more effective preventively common are dimenhydrinate and meclizine. The side
rather than waiting for symptoms to occur. effects of these drugs are related to their anticholiner-
gic effects, which include sedation, blurred vision, and
Labyrinthine Cues dry mouth; in higher doses, they can cause urinary re-
One proven treatment is to try to reduce the conflict be- tention and confusion. Dimenhydrinate is available as
tween the visual system and the labyrinth organs. This a liquid, tablet, or injectable formulation. It is readily
can be accomplished by viewing the horizon. In many available over the counter. Meclizine is also commonly
military operational settings, this may not be possible. used; typical oral dosing is 25–50mg every 8 hours. Op-
Additionally, lying flat has been shown to reduce the erationally, these drugs are limited primarily by the side
incidence and severity of symptoms. The physiology of effect of drowsiness. Unfortunately, studies evaluating
4
this effect may be due to the reduction in head move- the nonsedating antihistamines fail to show a benefit in
ment while lying supine. preventing motion sickness. 7

Adaptation is the most potent prophylactic option. Anticholinergics
2,3
Protective adaption is best accomplished by gradual Scopolamine is perhaps the most commonly used drug
and incremental exposure to provocative motion. Once for the treatment of motion sickness. It has been shown
adaption is achieved, it can be maintained by regular to prevent motion sickness. 1,2,8 In one trial, it was found
and repeated exposure to the stimulus. This technique to be superior to promethazine, meclizine, and loraz-
2
has been used frequently in the training of pilots and epam. The drug is limited by its short half-life, how-
9
aircrew. Those prone to motion sickness are frequently ever; it peaks within an hour of ingestion but lasts only
subjected to progressive desensitization training. Much about 4 hours. It is for this reason that a transdermal

Motion Sickness 79