Acute mountain sickness (AMS) is a syndrome that arises in non-acclimatized individuals who ascend to high altitudes. It is a form of acute altitude illness that occurs due to a decrease in the atmospheric partial pressure of oxygen as the altitude increases, inducing hypoxia. This condition typically occurs at an altitude of >2500 meters; however, it can occur at lower elevations in high-risk individuals.
The syndrome can present as a mild self-limiting disease with the presentation of non-specific symptoms such as dizziness, headaches, sleep disturbance, nausea, and vomiting. However, it may also progress to life-threatening complications such as high-altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Hence, early identification of individuals with the presentation of AMS symptoms can help prevent severe complications. The Lake Louise Questionnaire (LLQ) and the Acute Mountain Sickness-Cerebral score(AMS-C), are two assessment tools for identifying acute mountain sickness.
The AMS-C score derives from the Environmental Symptom Questionnaire (ESQ), which was formulated in 1979 to assess symptoms induced upon exposure to extreme environmental conditions. ESQ-III, the third and final revision, consisted of 67 questions, of which 11 are categorized to AMS-C. The questions are scored on a scale of 0 to 5, with 0 reported as “not at all” and 5 reported as “extreme.” Each response score is then multiplied to the factorial weight of its symptom, and a score of 0.70 or greater classifies as AMS-C. Due to ESQ-II, I being an intricate assessment tool, it is less frequently used.
The Lake Louise Questionnaire was introduced in 1991 and was last modified in 2018. It is now the most commonly used scoring system used to assess AMS. It defines AMS as the presence of headaches in addition to three other symptoms, including gastrointestinal symptoms, fatigue/weakness, and dizziness/lightheadedness. Each symptom is appointed a point on a scale from 0 to 3 with 0 being no effect and 3 being severe. A total score of 3 or greater, with the presence of headaches, in a setting of rapid ascent to high altitude, is diagnosed as acute mountain sickness. The Lake Louise Questionnaire, although an effective assessment tool, has its limitation. It is a scoring system to standardize and diagnose AMS for use by investigators or research purposes, and it is not meant for clinical practice.
Currently, no biomedical tests are available to diagnose acute mountain sickness; therefore, the disease is diagnosed based on the presentation of clinical features. The scoring scales serve to identify and assess the presence and intensity of clinical features in an AMS individual. Individuals with a mild presentation of AMS receive treatment with supportive care with rest, hydration, and analgesic medications. Treatment for more severe cases of AMS includes oxygen and drugs such as acetazolamide or dexamethasone and descent in altitude.
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