ICE008: ABG Puzzler

These blood gases are grossly abnormal. They demonstrate:

•  moderate to severe alkalaemia
•  profound hypoxaemia
•  severe respiratory alkalosis
•  marked metabolic acidosis

To fully interpret them, it’s helpful to know that the samples were obtained when the barometric pressure was 272mmHg and the PiO₂ 47mmHg, making the expected alveolar O₂ only 30mmHg. So they have an increased A-a gradient.

They are the averaged results from 4 climbers who had just summited Mount Everest – the ABGs were taken without supplemental oxygen at an altitude of 8400m. All had normal psychomotor function at the time. Typically such gases would be judged as inconsistent with life and would mandate aggressive and immediate resuscitation. However these climbers just need to descend. At 7000m their O₂ content (but not SaO₂) is normal.

That it is possible to survive & function with such gases shows the degree to which we can acclimatise to altitude. Sudden exposure to such altitude would cause loss of consciousness in unacclimatised individuals. This research will inform ICU care for patients with severe hypoxaemia.

Reference:

• Grocott MP et al. Arterial blood gases and oxygen content in climbers on Mount Everest. N Engl J Med. 2009 Jan 8;360(2):140-9.