A neurogenic basis for acute altitude illness

Area of Science:

• Altitude Medicine
• Physiology
• Pathophysiology

Background:

• Acute altitude illnesses encompass acute mountain sickness (AMS), high-altitude cerebral edema, and high-altitude pulmonary edema (HAPE).
• AMS involves symptoms like headache, nausea, and lethargy, while cerebral and pulmonary edema are potentially life-threatening.
• Understanding the pathophysiology is crucial for effective prevention and treatment strategies.

Purpose of the Study:

• To summarize recent evidence on the pathophysiology of acute altitude illnesses.
• To explore the relationship between hypoxic cerebral vasodilation, intracranial pressure, and sympathetic responses.
• To discuss the proposed mechanisms linking these events to HAPE and renal salt/water retention.

Main Methods:

• Review and synthesis of recent scientific evidence and hypotheses.
• Analysis of the role of cerebral edema, intracranial pressure, and sympathetic activity.
• Discussion of hormonal influences (aldosterone, vasopressin, ANP) and therapeutic interventions.

Main Results:

• Acute mountain sickness (AMS) is linked to cerebral edema caused by hypoxic cerebral vasodilation and increased capillary hydrostatic pressure.
• This cerebral edema reduces brain compliance without altering global brain metabolism.
• Elevated sympathetic activity, potentially neurogenically mediated in the lung and kidney, is postulated to cause HAPE and salt/water retention.

Conclusions:

• Hypoxic cerebral vasodilation and subsequent cerebral edema are primary events in AMS.
• Peripheral sympathetic activation, modulated by hormones, plays a key role in developing HAPE and renal effects.
• The proposed hypothesis provides a framework for understanding altitude illness and evaluating therapeutic options.