A shocking blood gas!

A healthy young man comes to the ED after having been chased by the police. They say he ran for his life at least 1km after which they found him lying down, presumably unconscious. With all systems intact and stable vitals he's presumed to be faking (pseudocoma).

A quick glance in the ED reveals nothing new to refuse this theory - the patient has closed eyes and is totally resistant to pain stimulation but has all reflexes intact (eg. gag, cornea-) and with eyes forced open he's looking straight forwards (to contrast with eg. roving eye movements if true coma). ECG comes in normal.

The police officers are informed that patient can return to police station as soon as blood results have been seen. And here they come...

With a hefty metabolic acidosis and lactate of 12,9 there's a minute of silence and doctors start thinking if there's a red herring in the room...

Could the patient be intoxicated after all?

Alcohols maybe?

He doesn't smell - but do all alcohols smell?

That's an anion gap of 18 - is it all explained by lactate?




With a presumed intoxicated patient fluids are ordered and patient is prepared for admission. Just that 45mins later the policemen come to let know that the patient is now awake and feeling well and ready to leave the ED with the officers. So a new blood gas (venous of course, who's sticking arteries these days anyways!) is drawn and voila;

All results normal... So the lactate acidosis turns out to be caused by strenuous physical exercise. Now howzaaat!



Learning points

• Lactate can be very high after exercise! I remember a study where alpine ski-ers had 6-7 after coming down a slope and I've heard experienced clinicians state it may temporarily reach 20 after seizure). But you can even get disturbing pH levels from it!
• Ethylene-glycol and methanol are odorless!

And my question to the audience: can I somehow calculate presumed anion gap from lactate levels, so that I can exclude other agents?