Tachycardia in this context is a sign of either insufficient cardiac output or somebody who has some sort of untoward adernergic stimulation while a tachypnoea is a sign of end-cellular metabolic dysfunction (anaerobic respiration) is beginning to develop lactic acidosis however I think these are often missed or not picked up on.

I would also have to say temperature is probably a very helpful physiologic parameter as it is often a sign of low cardiac output.

From the Ambulance perspective, several US jurisdictions have introduced pre-hospital lactate measuring however I am not sure it’s totally necessary and the money is probably better spent on introducing ceftriaxone or benzylpenicillin.