Page 92 - Journal of Special Operations Medicine - Summer 2016

An Ongoing Series

Sea State Green

Joshua Banting; Tony Meriano, MD

CONCEPTS AND OBJECTIVES
The series objective is to review various clinical con- and the vestibular system’s sense of movement. It is
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ditions/presentations, including the latest evidence on characterized by pallor, nausea, and vomiting. It can be
management, and to dispel common myths. In the pro- brought about by exposure to real, or apparent, or un-
cess, core knowledge and management principles are en- familiar motion to which the individual is not adapted.
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hanced. A clinical case will be presented. Cases will be It can occur in a variety of environments: air, sea, space,
drawn from real life but phrased in a context that is ap- motor vehicles, and even virtual reality. There are sig-
plicable to the Special Operations Forces (SOF) or tac- nificant differences in individual susceptibility to mo-
tical emergency medical support (TEMS) environment. tion sickness but, given enough stimulus, most people
Details will be presented in such a way that the reader will experience some degree of symptoms. The spec-
can follow along and identify how they would manage trum of symptoms can vary based on the individual and
the case clinically depending on their experience and the degree of motion. These symptoms can range from
environment situation. Commentary will be provided simple nausea, sweating, and occasional vomiting, to
by currently serving military medical technicians. The almost complete incapacitation. The symptoms usually
medics and author will draw on their SOF experience improve over 72 hours but can recur. In fact, some indi-
to communicate relevant clinical concepts pertinent to viduals will experience a level of motion sickness after
different operational environments including SOF and they return to land.
TEMS. Commentary and input from active special op-
erations medical technicians will be part of the feature.
Pathophysiology
Keywords: motion sickness; medication, antimotion sickness The prevailing theory explaining motion sickness is the
neural mismatch theory. It hypothesizes that motion
sickness arises when there is a conflict in signals the
brain is receiving regarding motion. The brain receives
Scenario
a variety of sensory signals to determine the position of
Your commander approaches you with the following the body and head in space. These include visual cues,
directions. The team is planning for a maritime assault somatosensory cues, and vestibular input from the in-
that will involve an opposed ship boarding in possibly ner ear. In the inner ear, the labyrinth encodes angular
severe sea states. Your team will loiter in rigid-hulled motion, which is sensed by the semicircular canals and
inflatable boats and make an opposed boarding of a ves- linear acceleration, and gravitational force (sensed by
sel of interest while it is under way. He wants to make the otolith organs). Disparity in these sensory inputs
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sure he does not lose any of his guys to seasickness and can cause conflict that can lead to motion sickness.
that whatever preventive drugs you use do not affect For example, if a person is inside a boat that is being
their ability to conduct the assault. You take stock of tossed around by waves, the conflict between limited vi-
the situation. You realize that the clinical question at sual cues and the input from the vestibular system leads
hand is: what is the most effective antimotion sickness to motion sickness. Experimental support for this hy-
medication with the least effect on clinical performance? pothesis is demonstrated in test animals that have their
labyrinth system disrupted, they do not develop motion
sickness. 1
Motion Sickness
Motion sickness is a syndrome that occurs when there Motion sickness can be induced in almost all people if
is a disagreement between visually perceived motion the stimulus is sufficient; however, certain people are

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