Stat can be an abbreviation for statistic, photostatic, statute, thermostat, or the Latin word statim.
Statim is an adverb and means that a specified action or request should be done right away and before anything else is done first.
This term is often used in medical fields. Hardly ever is the actual word used, however. It is almost always used in the abbreviated form of stat. Some people feel the need to capitalize this abbreviation, possibly because the definition makes it seem emphasized, but this is not necessary. Italicization is also not necessary since the Latin term has been so thoroughly adopted into the English language for so long.
Now is also an adverb and also means right away or immediately. However, in medical language it is distinctly different than stat. Usually a now order is something that is dependent on someone else before one can fill it, like receiving a medication from the pharmacy. These orders can wait for that other action to be done before the order is filled.
Whereas a stat order cannot wait for anything and is seen as much more urgent.
The exact definitions of these orders may vary slightly depending on the institution or hospital that uses them.
Outside of the medical fields, stat and now are more interchangeable. Though stat would still carry an added sense of urgency, as if something were as important as in a medical setting.
Examples
The integrated solution enables notifications of stat orders and other critical information from Cerner to be sent directly to care team members on their Vocera devices, significantly reducing delays in communication. [PR Newswire]