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Overdose of anaesthesia given to elderly woman not linked to her death: Coroner’s inquiry

SINGAPORE — A nurse at the Singapore General Hospital (SGH) accidentally administered 10 times the required dosage of anaesthesia to an elderly woman after she mistook the machine’s dose selection for the rate selection.

Overdose of anaesthesia given to elderly woman not linked to her death: Coroner’s inquiry
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SINGAPORE — A nurse at the Singapore General Hospital (SGH) accidentally administered 10 times the required dosage of anaesthesia to an elderly woman after she mistook the machine’s dose selection for the rate selection.

However, this "gross error" did not directly contribute to, or hasten, the death of 86-year-old Chow Fong Heng, who died on June 2 in 2016, Coroner Marvin Bay said on Wednesday (Dec 19).

The coroner's finding is that Madam Chow died of natural causes.

A forensic pathologist recorded that she died of multi-organ failure and septicaemia (or blood poisoning).

Madam Chow’s medical history showed that she had end-stage renal disease and suffered from other illnesses, including hypertension and hyperlipidaemia, which is a high level of cholesterol in the blood.

She was receiving her regular dialysis treatment on May 24, 2016, when nurses at the Fresenius Medical Care clinic noticed her scratching her arm — which had an arteriovenous fistula — and were concerned that there could be an infection.

An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein that can be congenital or surgically created for the purposes of dialysis.

Mdm Chow was admitted to SGH on the same day, where she was diagnosed with a superficial infection.

WHAT HAPPENED AFTER HER ADMISSION 

May 27, 2016: Mdm Chow was found to have low blood pressure during dialysis. Her blood pressure was restored.

May 28: At around 12pm that day, her heartbeat was noted to be faster than normal. She was transferred from the general ward to the renal intermediate care centre at SGH. Mdm Chow was also given antibiotics.

May 29: The antibiotic dose was raised and a chest x-ray showed signs of lung infection. Her heartbeat remained higher than usual.

May 30: A cardiology review showed her heart had an abnormal rhythm, with her heartbeat remaining higher than usual. A decision was made to administer intravenous doses of lignocaine, a form of anaesthesia.

May 31: The overdose of lignocaine was discovered. The infusion was to be given over 24 hours, but was instead infused over 2.4 hours. Mdm Chow did not show any signs of lignocaine overdose.

June 1: Mdm Chow’s condition deteriorated, with unstable blood pressure and an excessive amount of acid in her body fluids and tissues.

June 2: Her condition continued to deteriorate and she died at 3.28pm.

THE OVERDOSE

It was revealed during the coroner’s inquiry that the machine administering the anaesthesia was set to run at 41.7 millilitres an hour, instead of 4.17ml an hour. This caused nearly 81ml of lignocaine to be administered within a span of two hours, far higher than the earlier dose of 50ml over 12 hours given the evening before on May 30.

The nurse who administered the overdose testified during the inquiry that she “had mistaken” the dose selection for the rate selection in the machine.

If dose selection is used, the nurse would need to key in 41.7 milligrammes an hour. If rate selection is used, that figure would be 4.17ml an hour.

The nurse, who was not named, “inadvertently keyed in” 41.7ml in the rate selection, which was 10 times the required dosage.

Coroner Bay noted that she was “unfamiliar with the (system) as she had limited exposure to its usage”. This was an “area of concern”, he said.

“She had of course made the gross error in calculations with regard to the amount of lignocaine administered, apparently confusing the application of units of milligramme and millilitre, and mistaken the dose selection for the rate selection,” he added.

The coroner pointed out that while there was no direct link between the overdose to Mdm Chow’s death, “there should be no doubt that misadministration of sedative drugs can have extremely dire consequences”.

He said it was “heartening” to note that SGH had acknowledged its shortcomings in the training and assessment of its nurses’ competency.

“SGH has informed the inquiry of steps taken to remind and reinforce the importance of strict compliance of requirements imposed in counterchecking where medications and sedatives are administered, and also in ensuring that nurses have the requisite competency and knowledge when tasked to administer medication to patients,” Coroner Bay said.

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