My aunt was given a double dose of an antihypertensive despite being literally ready to discharge after a CHF exacerbation. Became brady, coded, sent to CVICU, developed intrabronchial hemorrhage in the setting of a traumatic intubation and antiplatelets, was in the ICU for almost 2 months, and honestly was never the same. Never got to the same level of functioning she had prior, never lived alone again, and passed away a couple years later.
While on nights, had an elderly psychotic patient code in the psych unit. Looked through the documentation and over the 5 previous days, there had been 4 different attendings covering the patient and each one increased titration of clozapine. The resident was an intern on one of their first rotations and had never titrated clozapine, so didn't know what was appropriate. Looking back it was a mistake. The patient had a ton of risk factors and reasons for sudden cardiovascular or cerebrovascular event (never found out which it was), but I doubt the clozapine helped.
Also while on night call, patient received a beta blocker in the ED prior to transfer to the floor. 4 hours earlier admission orders with the beta blocker starting tonight were put in by day senior and automatically "signed and held", and ultimately they were released after the patient took an unusually long time to come up to the floor and be officially "admitted". They ended up getting a double dose, became brady and coded, went to the MICU (coded 3 more times with CPR and ROSC), spoke with family, and they were able to make it to the hospital before the end. This was early intern year and I've tried to always triple check admission orders when they get up to the floor since. It also wouldn't really happen again, because now we "admit" patients while they're in the ED and manage them even before they come up, but its still good practice. This patient also had a lot of risk factors, and honestly the comment my senior made after getting handoff with her cardiac history and current state was "so basically she could drop dead at any moment" to which I responded, "yeah, but hopefully not tonight".
I accidentally ordered a CT on a patient without contrast, making it almost useless from a clinical standpoint for what we were hoping to get out of it. Looked back and the patient had been getting almost weekly CTs almost every time a new staff came on for like months, and I put them through another one that basically gave no clinical info.
I signed a refill request too quickly intern year and ended up sending a patient 5 times their usual dose of a medication. Realized pretty quickly (within in hour), but not before patient went to pick up the script and was like, "what the hell?" (fortunately they knew their medication and doses). Called the pharmacy and patient frantically and the patient thought it was pretty funny. I almost had a heart attack though.
Those are the bad ones I remember, but there were definitely more. As for near misses, I don't know how many times I've put in orders on the wrong patient only to realize and correct it right after I sign the order.