A prominent Sydney plastic surgeon has been found guilty of professional misconduct and unsatisfactory conduct following the deaths of two of his patients and a relationship with another.

Ear nose and throat surgeon Dr William Mooney took an “astonishingly short” time to operate on patient A, while another procedure was performed “far too quickly” on patient B, before both died, the New South Wales Civil and Administrative Tribunal was told.

Both patients’ names have been suppressed.

His unsatisfactory professional conduct was deemed of a sufficiently serious nature to justify “suspension or cancellation of the practitioner’s registration”, the tribunal concluded.

In 2018 patient A sought help for snoring from Mooney, and his operation began at 3.05pm on 15 February 2018.

A scrub nurse observed Mooney saying the patient’s tonsils were adhered “like cement” and that he had trouble cutting into the right tonsil, and after some bleeding finished the procedure by 3.38pm.

Mooney did not observe the solution that a gauze was soaked in before he inserted it into the nose, something that was strongly criticised in expert evidence by Dr Cameron Altmann.

He described it as “basic intern- or first-year-doctor-level management”.

Altmann also said it was an “astonishingly short” time for such an operation, which he said would normally take about 90 minutes, without complications. Altmann said little time could have been spent on controlling the arterial bleeding.

Mooney did not review patient A over the next two days, but checked up via phone before he was released on 17 February.

When patient A vomited blood from his nose and mouth, he tried calling emergency contact numbers given by Mooney but nobody answered. He was later rushed to hospital.

His family was then informed an artery had been hit during the surgery. Following massive haemorrhaging and multiple organ failure, the patient died on 3 March.

Patient B was 41 when he sought further sinus treatment from Mooney in November 2017.

Despite it being a complex procedure “on a patient who had undergone multiple surgeries, including one six weeks earlier and inflammatory disease”, the doctor left after 25 minutes, the Health Care Complaints Commission said.

“His anatomy would have been very variable due to inflammation, scar tissue and the surgical interventions.”

Mooney said in a statement that he should have exercised greater caution.

“Regrettably, I proceeded to use sharp and dangerous instrumentation at the base of the skull in a high-risk position,” he said.

Patient B died in hospital on 13 December 2017.

Mooney was also found to have lied about a relationship he had with a patient after records showed the pair exchanged 3,425 text messages and 807 phone calls between October 2013 and January 2016.

He said most of the calls had been made late at night, he had probably been drinking and “trying to find some shard of happiness”, and also denied prescribing weight loss medication Duromine to the woman, who had formerly suffered an eating disorder.

But the tribunal found he was not truthful nor had he complied with hair drug screening after avoiding tests due to “illness” and giving himself a “buzzcut”, among other measures.