This is a hard question to answer. The short answer is always "Well, yes....", but the longer answer is usually, "...but you probably don't want to do that."
The explanation why "you probably don't want to do that" takes some time, but interestingly, Hollywood can sometimes provide some good teaching examples. (Even if they are fictional, they are still useful to demonstrate the real answer.)
One of the most influential movies for me, growing up in the early 80s, was the movie Wargames, directed by John Badham and starring Matthew Broderick and Ally Sheedy. Interestingly, it provides some useful teaching examples for healthcare informatics. Allow me to demonstrate :
Pay close attention to this opening clip which parallels what nurses experience every day. Two men, in a nuclear missile silo, show up for work and get an electronic order to launch a missile. The codes authenticate, they have clear procedures and protocols to follow. And yet, before launching missiles that could kill millions of people, one of the men smartly asks the question, "Does this seem right?".
(Note, because he doesn't trust the electronic order he's received, he smartly picks up the phone and tries to get a human being to clarify for him - AKA he tries to page the doctor to make sure the order is real.)
I think most nurses watching this clip can relate to these two men.
I suppose some of it is human nature, to trust a human being more than a machine. We are tribal, and so it seems intuitive to want to speak to a human being, before carrying out an order received from a machine. A written order, despite all of its flaws, carries a certain amount of intuitive trust - The physician's pen hit the paper, the ink is dried in place, this is the handwriting of the doctor I usually work with - It provides much more confidence for a nurse.
An electronic order does not deliver the same trust. We worry that the machine may have interpreted the instruction wrong. Or perhaps the programmer didn't think of this particular scenario. We're trained from childhood on how to figure out machines that don't work. We know they sometimes make mistakes.
So getting back to the question about "automatically canceling orders", and "why you probably don't want to do that".
After this opening scene of the movie, the very next scene shows technicians ripping the chairs out of the missile silo, while a team of strategists deep inside the NORAD missile command say, "We had to take the men out because we learned we couldn't trust them to push the button... So now we've wired the WOPR computer directly to the button."
This then sets up the plot for the rest of the movie - The WOPR computer is wired directly to the button, and when David Lightman (Matthew Broderick's character) hacks into the WOPR to make it malfunction, they are stuck - There is no human being between the computer and the missile launch.
What does this teach us about the importance of human beings carrying out your order protocols, rather than the computer "just doing it automatically?"
Because computers are unforgiving. If you ask them to do something, they will do it. 100% of the time. No questions asked.
The problem with a computer discontinuing an order, then, is this : What happens if you ever have a patient, who for some bizarre and unplanned reason, shouldn't have the order automatically discontinued? What if this one patient, in a million, actually needs the order to continue longer?
1. If you have a computer automatically discontinue the order - That one patient will suffer the problems of being "the one-in-a-million" exception.
2. If you have a nurse following a protocol to discontinue the order - Then you actually have a chance that the nurse will ignore the protocol, knowing "it's the right thing to do". (Yes, good nurses know when to ignore orders and protocols if they could harm the patient.)
What does this clip help demonstrate?
1. Electronic Order Entry comes with an inherent fear, and rightfully so - This is why nurses page us to clarify orders, and when they do, we as doctors should be glad nurses are asking questions - I never want a nurse who is an automaton.
2. For patient safety and good care, communication between nurses and physicians should be ample, easy, and painless. Nurses should never feel forced to press a button without understanding the impact and reasons why they are being asked to do it. If the situation doesn't make sense to them - You want them to call!
3. Nurses are the last safety gap before the delivery of care / button gets pressed. (See the men in the movie clip above!) We should respect their professional judgement - It's there for very good reasons.
4. You generally don't want to take the nurses out of the silos. Imagine the risks of EMR software actually delivering the medications! :)
5. For safety reasons... you generally don't want the computer to automatically cancel the order. Why?
a. Because a computer canceling it 100% of the time may not be safe for 100% of the patients.
b. Because you can never create a protocol that is 100% safe for 100% of patients.
c. Because for safety, in that unplanned circumstance - you want a nurse to know when to say "no".