Woman's death after dental surgery a medical misadventure: Coroner

After suffering severe pain in her mouth for a few days, Ms Toh Yi Lin visited the National Dental Centre Singapore (NDCS), where it was found that the pain may be due to an impacted wisdom tooth.

Her other three wisdom teeth were found to be also impacted, so Ms Toh, 24, elected to have all four removed under general anaesthesia. But she died shortly after the operation.

Coroner Kamala Ponnampalam ruled on Sept 30 that Ms Toh's death in 2019 was an unfortunate medical misadventure.

The cause of her death was certified to be consistent with malignant hyperthermia, a severe, life-threatening reaction to certain anaesthetic agents.

According to court documents, Ms Toh had a history of a high fat levels in the blood that was managed with medication.

Ms Toh, who had no known drug allergy, had undergone two uneventful operations in 2011 and 2013 under general anaesthesia.

On May 8, 2019, she was admitted to NDCS for her dental surgery, and her general condition and vital signs were assessed to be fine.

Anaesthetist Diana Chan Xin Hui, a consultant at SingHealth, went through an assessment with Ms Toh who, after consenting to undergo general anaesthesia, was taken to the operating theatre.

After her vital signs were again assessed to be normal, she was anaesthetised by Dr Chan.

An NDCS senior consultant performed the surgery, which was uneventful for the first 90 minutes. But before it was over, Ms Toh's carbon dioxide concentration level rose mildly.

This became more severe after surgery, and her oxygen saturation level also fell. Ms Toh was immediately given oxygen ventilation, which temporarily improved her condition.

But she did not wake up. She had a fever of 42 deg C, and ice packs were applied and paracetamol given intravenously. She was taken to Singapore General Hospital, and despite attempts to resuscitate her, she died at about 1.30pm.

During the coroner's inquiry, Ms Toh's family raised questions about pre-surgical investigations and screening for the risk of malignant hyperthermia.

Dr Jody Hong, an NDCS dental officer who had reviewed Ms Toh before the operation, said she told Ms Toh and her mother that Ms Toh could choose local or general anaesthesia during surgery.

After discussing with her mother, Ms Toh decided on general anaesthesia.

Dr Chan said she had determined that the risk of malignant hyperthermia for Ms Toh was low, given that she did not develop any side effects during her previous operations and her family did not have a history of severe reaction to anaesthetic agents.

Dr Chan added that malignant hyperthermia is a very rare inherited condition that occurs in one in 50,000 in Western populations and is even rarer in Asians.

But the death rate is high due to the severity of the reaction to anaesthetic agents, she said.

An independent medical expert found the response to the complications arising at the end of the surgery adequate. He said that usually, if a patient or his family members had a previous adverse reaction that suggested malignant hyperthermia, specialised tests would be recommended.

But due to the rarity of the disease and the high cost of tests, they would not be offered if the patient or any immediate family member had no history of adverse reactions to anaesthesia.

The expert, who noted that Ms Toh was asked about her and her immediate family members' past reactions to anaesthesia, said Dr Chan had fulfilled the appropriate screening procedure.