Clinical Care in Extreme Environments: At High and Low Pressure and in Space

Physiology and pathophysiology at high altitude: considerations for the anesthesiologist

“…Diuresis with furosemide and mannitol may be helpful, but these agents are currently not recommended [54,58]. Acetazolamide and, controversially, dexamethasone or ginkgo biloba, may be attempted as prophylaxis against AMS, and aspirin and ibuprofen may decrease the associated headache [14,54,62,63].…”

“…It has been demonstrated that nitrous oxide causes less analgesia and is a less potent anesthetic at HA, because its concentration remains fi xed and its partial pressure decreases as barometric pressure drops [79][80]83]. Therefore, it has been advised to avoid nitrous oxide at HA [62]. Conversely, halothane has been successfully used in a hyperbaric chamber at an equivalent altitude of 5490 m [62].…”

“…Therefore, it has been advised to avoid nitrous oxide at HA [62]. Conversely, halothane has been successfully used in a hyperbaric chamber at an equivalent altitude of 5490 m [62]. Moreover, the partial pressure of anesthetic vapors is dependent on temperature, not barometric pressure, and in an extremely cold environment more anesthetic vapor might be required [73,82].…”

“…Both O 2 and nitrous oxide fl ow meters tend to under-read the actual fl ow rate. It may therefore be hazardous to mix a low fl ow of O 2 with a higher fl ow of nitrous oxide [62,81]. An O 2 analyzer calibrated at HA is advisable under these circumstances.…”

Safety of hyperbaric oxygen therapy in mechanically ventilated patients

“…Finally, neuromuscular blocker use is possible in association with sufficient sedation with the same advantages and disadvantages associated with its use in the ICU [15]. There are neither proven pharmacokinetic nor pharmacodynamic effects due to high pressure until 608 kPa (50 msw depth) for anaesthesia drugs [16].…”