Traveling to the highest regions of the Big Island carries with it a set of hazards that only apply to this part of the island. In addition to severe mountain weather, hikers traveling above 6000-8000' above sea level must consider Acute Mountain Sickness. 

Acute Mountain Sickness (AMS): Acute Mountain Sickness is serious and can be potentially fatal. AMS has nothing to do with fitness level, age, or diet. It’s only a function of your subjective ability to deal with changing altitude. Starting at a higher elevation is very helpful, but most visitors to Hawai’i stay along the coasts. If you live in a mountain setting in America, you might consider climbing Mauna Loa or Mauna Kea on one of your first days on the island. Despite many old wives’ tales, the only cure for AMS is to descend in altitude. No other action relieves the symptoms of AMS.

Symptoms of mild AMS include: mild to severe headache; nausea; vomiting; lack of appetite; lack of energy; altered balance and coordination; dizziness. Symptoms of extreme AMS include: loss of mental awareness; extreme shortness of breath even at rest; swelling of the hands and face; loss of consciousness.

Even more serious are two conditions of AMS known as High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE). HAPE symptoms include: headache; nausea; anxiety; inability to catch breath even at rest; gurgling sound in the lungs; very rapid respiration rate; dry cough becoming wetter; incoherence and possibly hallucinations; blue coloration in lips and fingertips. HACE symptoms include: headache that does not respond to aspirin; nausea and vomiting; loss of balance; altered mental state; decreased mental ability; confusion; hallucinations; inability to talk; coma-like state.

As stated above, the only cure for AMS is to descend. I always experience a bit of lightheadedness and slight nausea when climbing to high altitudes, and mild symptoms of AMS are normal when climbing high mountains and are just part of the experience. However, more severe symptoms of AMS could be fatal. In general, fluid in your lungs or severe mental issues might be HAPE or HACE, which are very severe conditions. AMS is fickle and affects people differently. Divers should take special caution to avoid these higher areas at least until 24 hours after a dive, as they would a plane flight.

Ascending gradually and with controlled stops is the key skill here. The greater danger is actually when driving because you can rapidly ascend altitude more rapidly than on foot. Case-in-point: the Mauna Loa trailhead is a bit over 11,000 feet. Rapidly ascending from sea level to this altitude is nearly sure to trigger symptoms of AMS. A good idea would be to drive leisurely to where the Mauna Loa observatory road begins at about 6500’ and stop for a while. Then, continue to about 8,000 feet and stop again. Then, drive to the trailhead at 11,000 feet and spend a considerable amount of time just waiting there.

If you experience severe AMS symptoms or even persistent mild AMS symptoms, descend immediately and save the mountain for another day. If symptoms persist once you’ve descended to sea level, obtain medical attention immediately. This is a matter of life and death.