Nitroglycerin error

Dosage rate errors are not uncommon with Nitroglycerin due to the dose being very similar to the rate in ml/hr.  The dose and rate ideally should be obviously different measurements, or the same.  A slightly different concentration of what is typically available gives you a mcg/min rate that is the same as the ml/hr rate, which would solve this problem.

Luckily, the initial rate you incorrectly entered was not a potentially harmful dose, and is actually less that what we typically start chest pain patients at.  So long as their blood pressure held (and they aren't a right sided MI), then there was little likelihood of harm, of course that doesn't mean an error should be taken less seriously.

The one thing I would suggest is that sometimes when people recognize this error they change their current rate to mcg/min; you are at 20ml/hr then you see you've been using the ml/hr instead of the mcg/min and then you change the dose to 20mcg/min.  If the current rate has met the titration goals then leave the rate where it is, and chart what the dose is in mcg/min at that ml/hr rate.  

It sounds unlikely that you caused the MI, the patient came in with a likely MI which is why you started them on a Nitroglycerin drip.  For NSTEMIs it's not unusual practice to maintain them on a NTG drip so long as their CP can resolve on the drip, and heparin or other antiplatelet is often added as well.