Because when the feedback loops on his 140lb musculature are blocked and he will keep going to the point of permanent damage... and when his ability to feel pain is decreased... and there's a very real concern for hyperthermia, rhabdomyolysis with an extended struggle, dysrhythmia, then maybe ketamine becomes the better option.

That being said, ketamine should be an EMS decision to minimize risk to patient and others, not "at LE direction".