Stephen Ennis had 72 previous convictions, including convictions for violent disorder, possession of drugs for sale or supply, possession of knives, burglary and begging
The Court of Appeal heard the doctor had moved to Ireland to realise his dream of becoming an emergency medicine consultant but has since given up his hopes after the attack left him "shattered".
The warning was given to Stephen Ennis by Mr Justice John Edwards, after the court quashed a one-year sentence handed down to the father-of-two.
The assault took place during the first wave of the pandemic in a busy hospital's emergency department, where Ennis was admitted after he had a seizure outside a garda station.
At the time of sentencing, Ennis had 72 previous convictions, including convictions for violent disorder, possession of drugs for sale or supply, possession of knives, burglary and begging.
Delivering yesterday's judgment, Ms Justice Isobel Kennedy said the court found that not only was the original sentence unduly lenient it had been "appreciably so".
Ms Justice Kennedy, who was also sitting with Court President Mr Justice George Birmingham, told Ennis he would be resentenced in three months' time after the court considered background reports.
The court's decision, Mr Justice Edwards added, would be "very much influenced" by the content of probation reports which would focus on Ennis' claim that he was no longer using drugs.
"We are making no promises. The ball is now in your court," Mr Justice Edwards advised him.
Ennis (32), of Cashel Road, Crumlin, Dublin, was jailed for one year after he pleaded guilty to assaulting a person providing medical care in St James' Hospital, James Street, Dublin 8, on March 7, 2020.
The Director of Public Prosecutions (DPP) later appealed the sentence handed down by Judge Martin Nolan at Dublin Circuit Criminal Court on October 2020 on the grounds that it was unduly lenient.
Fiona McGowan BL, for the DPP, told the Court of Appeal yesterday that the sentencing judge had given insufficient weight to the harm Ennis's actions had caused to the injured party.
The doctor, Ms McGowan said, was a foreign national who had been studying for his exams to become an emergency medicine consultant around the time he was attacked by Ennis.
Ms McGowan said that, as a result of the incident, the medic now realises how vulnerable frontline healthcare workers are and was now focused on a career in general practice. "It was a very tough decision for him to take," she added.
Keith Spencer BL, for Ennis, said his client was suffering from a "deep-rooted addiction" at the time.
"He has done wrong and he accepts that," Mr Spencer said. "It would be a retrograde step to send him back to prison."
Before adjourning sentence until May 12, Mr Justice Edwards, presiding, with Mr Justice Birmingham sitting remotely, noted that recent legislation meant attacks on medical frontline responders could attract a 40pc premium in sentencing.