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Motion
sickness is a symptom complex that usually includes nausea, often
accompanied by vague abdominal discomfort, vomiting, dizziness,
and related symptoms; it is caused by repetitive angular and linear
acceleration and deceleration. Behavioral change and drug therapy
can help prevent or control symptoms.
Individual susceptibility to motion sickness varies greatly. However, motion sickness is more common in women, and incidence ranges from < 1% on airplanes to nearly 100% on ships in rough seas and upon becoming weightless during space travel.
Excessive stimulation of the vestibular apparatus by motion is the primary cause. Afferent pathways from the labyrinth to the vomiting center in the medulla are undefined, but motion sickness occurs only when the 8th cranial nerve and cerebellar vestibular tracts are intact. Movement via any form of transportation can produce excessive vestibular stimulation, including ship, motor vehicle, train, plane, spacecraft, and playground or amusement park ride. Motion sickness can also occur when there is conflicting vestibular, visual, and proprioceptive input; when the pattern of motion differs from that previously experienced; and when motion is expected yet not experienced (eg, when viewing motion on a television or movie screen). Visual stimuli (eg, a moving horizon), poor ventilation (with fumes, smoke, or carbon monoxide), and emotional factors (eg, fear, anxiety) may act with motion to precipitate an episode.
In the space adaptation syndrome (motion sickness during space travel), weightlessness (zero gravity) is an etiologic factor. This syndrome reduces the efficiency of astronauts during the first few days of space flight, but adaptation occurs over several days.
Symptoms,
Signs, and Diagnosis
Nausea and vague abdominal discomfort are characteristic. Vomiting may also occur. These symptoms may be preceded by yawning, hyperventilation, salivation, pallor, profuse cold sweating, and somnolence. Other symptoms include aerophagia, dizziness, headache, fatigue, weakness, and inability to concentrate. Pain, shortness of breath, and visual and speech disturbances are absent. With prolonged exposure to motion, the patient may adapt. However, symptoms may recur if motion increases or after a short respite.
Prolonged motion sickness with vomiting may rarely lead to dehydration with hypotension, inanition, and depression. Motion sickness can be serious in patients with other illnesses.
The diagnosis is clinical and usually straightforward. Occasionally, cerebrovascular events, such as stroke or transient ischemic event, may mimic motion sickness.
Treatment
and Prevention
Several interventions are available, and all are more effective when used for prevention than when used after symptoms develop. People prone to motion sickness should take prophylactic drugs before symptoms start. Scopolamine is available as a prescription transdermal patch or in oral form. The patch is a good choice for longer trips because after being applied behind the ear at least 4 h before travel (optimally 8 to 12 h), it is effective for up to 72 h as it releases about 1 mg. The oral form of scopolamine is given as 0.4 mg to 0.8 mg 1 h before travel and then q 8 h as needed. Adverse effects, which include drowsiness, blurred vision, dry mouth, and bradycardia, occur less commonly with patches. Inadvertent contamination of the eye with patch residue may cause a fixed and widely dilated pupil. Additional adverse effects of scopolamine in the elderly can include confusion, hallucinations, and urinary retention. Scopolamine is contraindicated in people who are at risk of angle-closure glaucoma. Scopolamine can be used by children > 12 yr in the same dosages as for adults. Use in children < 12 yr is probably safe but is not recommended.
Alternatively, beginning 1 h before departure, susceptible people may be given nonprescription dimenhydrinate , diphenhydramine , or meclizine 25 to 50 mg po qid ( dimenhydrinate for children 2 to 6 yr, 12.5 to 25 mg q 6 to 8 h, maximum 75 mg/day; for children 6 to 12 yr, 25 to 50 mg q 6 to 8 h, maximum 150 mg/day); promethazine 25 to 50 mg po bid (for children < 12 yr, 0.5 mg/kg bid); or cyclizine 50 mg po qid (for children 6 to 12 yr, 25 mg tid) to minimize vagal-mediated GI symptoms. However, all of these drugs are anticholinergic and can cause adverse effects, especially in the elderly.
If vomiting occurs, an antiemetic can be given rectally or parenterally to be effective. If vomiting is prolonged, IV fluids and electrolytes may be required for replacement and maintenance.
Some nondrug therapies are unproven but may be helpful. These include use of wristbands that apply acupressure and wristbands that apply electrical stimulation. Both can be safely used by people of all ages. Ginger (1 to 2 g) may help prevent motion sickness.
Susceptible people should minimize exposure by positioning themselves where motion is the least (eg, in the middle of a ship close to water level, over the wings in an airplane). If traveling in a motor vehicle, driving or riding in the front passenger seat is best. Whatever the form of transportation, rear-facing seats should be avoided. A supine or semirecumbent position with the head supported is best. Adequate ventilation helps prevent symptoms. Reading should be avoided. Keeping the axis of vision at a 45° angle above the horizon and whenever possible focusing on stationary objects help reduce susceptibility. Alcoholic beverages and overeating before or during travel increase the likelihood of motion sickness. Small amounts of fluids and bland food should be consumed frequently during extended travel; some people find that dry crackers and carbonated beverages, especially ginger ale, are best. If air travel time is short, food and fluids should be avoided. In the space adaptation syndrome, movement, which aggravates the symptoms, should be avoided.
Last full review/revision November 2005
Content last modified November 2005
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