A verdict of "medical misadventure" has been recorded in the death of a woman with an "unusually healthy" heart after she suffered a cardiac arrest while undergoing a routine procedure at a dental clinic in Dublin two and-a-half years ago.
An inquest into the death of Margaret O'Doherty, 72, five days after becoming ill during surgery for seven dental implants at the Dublin Specialist Dentistry in Sandyford heard evidence the most likely cause of her sudden cardiac arrest was the effect of a sedative drug, Midazolam, used during the surgery.
The two-day hearing at Dublin District Coroner’s Court was informed that Ms O’Doherty and her family had alerted two dental surgeons during several consultations in advance of the procedure that she was "extremely sensitive" to sedative medication.
However, the claim was disputed by oral surgeon, Seamus Rogers, and prosthodontist, Maurice Fitzgerald, who said they were unaware before the surgery that she had any issue with sedatives.
Following her verdict, the coroner, Clare Keane, said she would recommend to the Dental Council of Ireland to urgently review its existing guidelines on conscious sedation which date back to 2005 and to ensure the existing guidelines were "robustly adhered to".
Dr Keane said she would particularly ask the Dental Council to publish standards for treatments that involved more than one dose of a sedative.
The coroner also acknowledged that she had no doubt that everyone involved in Ms O’Doherty’s care had the "best intention".
A pathologist who carried out a post-mortem examination on the deceased's body, Tom Crotty, said Ms O’Doherty had an "unusually healthy" heart for a woman of her age and found no evidence that she had any cardiac disease that could have caused her death.
Dr Crotty said the post-mortem results showed she died from a lack of oxygen to the brain due to the cardiac arrest.
Questioned by the coroner, Clare Keane, Dr Crotty said he believed what happened to the patient was "most likely" linked to her sedation with a drug known to cause slow and ineffective breathing as well as cardiac arrest in rare cases.
While the pathologist acknowledged that Ms O’Doherty had a narrowing in a small area of a coronary artery, Dr Crotty said it was "unlikely that was enough to explain her sudden death".
Ms O’Doherty, a mother of three from Merrion, Gorey, Co Wexford died in St Vincent’s University Hospital in Dublin on 23 August 2020 - five days after undergoing surgery at the Dublin Specialist Dentistry.
Members of her family explained she had asked about seeking a more conservative form of treatment for injuries to her teeth suffered in a fall in the driveway of her home in February 2020.
However, they were told the proposed procedure was the best option and her daughter, Clodagh O’Doherty, said her mother had also been reassured as Dr Fitzgerald told her his own mother, who was of a similar age, had undergone the same surgery.
The deceased’s husband, Michael O’Doherty, a GP who runs the Gorey Medical Centre, told the inquest he was "amazed" to learn there was nothing in the clinic’s notes about his wife’s issue with sedatives as they had "laboured" the point during consultations with Mr Rogers and Dr Fitzgerald.
Sensitivity to medicine
Dr O’Doherty said his wife had suffered a previous fall in 2019 after taking a dose of Night Nurse and would not even take a Panadol because of her sensitivity to such medicine.
Counsel for the O’Doherty family, Sara Antoniotto SC, said they believed she had been given too much Midazolam during the procedure and she had suffered all the complications associated with the drug.
However, Mr Rogers claimed he had only heard about Ms O’Doherty’s issue with sedatives for the first time on the day before the inquest.
"I would not have given sedatives to someone who told me they were sensitive to them," said Mr Rogers.
'Large red flag'
Dr Fitzgerald also claimed he had no recollection of the couple raising the issue and said a concern about sedatives would have "raised a large red flag" if mentioned.
Counsel for Mr Rogers, Nathan Reilly BL, claimed the complexity of the case warranted a narrative verdict.
In other evidence today, a consultant in emergency medicine at SVUH, Derek Barton, said the patient was a healthy woman who had suffered a severe hypoxic (lack of oxygen) brain injury which he felt was linked to her being given Midazolam which was known could cause respiratory depression and cardiac arrest.
A consultant in intensive care medicine at SVUH, Donal Ryan, said Midazolam could lead to the obstruction of a patient’s airway but it was not an issue by the time Ms O’Doherty arrived at the hospital.
However, he said it was "the most likely cause" to explain her cardiac arrest.
A consultant anaesthetist who was called as an expert witness, Tom Schnittger, said dental practitioners should carry out a health assessment before any procedure to check that a patient did not have any cardiac or respiratory problems.
Dr Schnittger said it was important that they should also be aware that top-ups of Midazolam should only be given after the previous dose had reached its maximum effect, while the drug could also have a bigger impact on patients aged over 60.
He said there was often quite a wide variation in how patients reacted to Midazolam while smaller quantities could be given to those aged over 60.
The inquest heard the time taken for the elimination of the drug from the body of those aged over 60 could be up to four times as much as in younger adults which normally takes between 1.5 and 2.5 hours.
Mr Rogers told the inquest that he gave Ms O’Doherty an original 3.5ml dose of Midazolam followed by a 1.5ml top-up two and a half hours later.
Dr Schnittger also said the administration of the drug intravenously should only ever be carried out by two people as it was "not suitable" to be done by just one person.
He said existing standards recommended that practitioners should have appropriate training in sedation and resuscitation, while he understood the recommended inspection of dental surgeries to ensure staff had adequate training and equipment for emergency situations was not currently being conducted.
Family welcome verdict
Welcoming the verdict of medical adventure, solicitor for the O’Doherty family, Rachael Liston said her clients questioned if it was appropriate that such difficult and lengthy surgery should be carried out in a community setting.
Ms Liston said the Dental Council also needed to ensure that there was adequate monitoring of the breathing and vital signs of patients under conscious sedation.
Dr O’Doherty, who was accompanied by his three children, Clodagh, Niamh and Cian - who are also doctors - remarked: "Losing my wife has been an extremely devastating event for my family and I. It was tragic and we believe avoidable."
He said they wanted lessons to be learned from what had happened "to ensure that this never happens to any other family."
"Deaths like this should be investigated," he added.
Dr O’Doherty also praised staff at SVUH for their care of his wife which he said was "compassionate, considerate and professional, and made this dreadful experience more bearable".
