01 April 2020

Putting patients to sleep using various forms of anaesthesia has been used in medicine for over a century. However, there’s still a lot we don’t know about its effects. Up to 20 percents of patients may experience heart damage similar to that seen in heart attacks.

The nurse Johan Spjut together with professor Michelle Chew taking care of a patient with severe burn injuries.   Emma Busk Winquist
Michelle Chew has a joint position as anaesthetist-intensivist and professor at LiU. She works at the Intensive Care Unit of the National Burns Care Centre at Linköping University Hospital and her patients are often hovering between life and death. She passes through the corridors at a confident, rapid pace. Talks unceasingly, and often shares a joke with her colleagues. But her voice takes a different tone when talking about the patients.Michelle Chew, professor i anestesiologi, BKV. Fotat på BRIVA, Universitetssjukhuset i Linköping. Photo credit Emma Busk Winquist 

“They are very unstable. They arrive here with extensive burns and may remain for several months. Their lives may never be the same again. But we don’t give up so easily. We know the body has an amazing ability to heal itself”, she says.

Frail patients

The patients come from all over Sweden, the Nordic countries and Germany. They are so frail that they cannot be moved around the department, and undergo surgery in the same room that they stay in while at the hospital. Many procedures – some small, some large. A burns victim must have the bandages changed often, which is very painful. Anaesthesia and analgesia are crucial to ensure the correct care.

“It’s not unusual for them to be put under anaesthesia many times”, says Michelle Chew.

Michelle Chew, professor i anestesiologi, BKV. Fotat på BRIVA, Universitetssjukhuset i Linköping. Utrustning i operationssal. Photo credit Emma Busk WinquistAnd they are conducting research here. For example, in parallel with the clinical work, scientists are developing methods to replace skin damaged by burns. Michelle Chew is studying the optimal methods to anaesthetise a patient, how anaesthesia affects the heart, and how patients recover after surgery. Putting patients to sleep using various forms of anaesthesia has been used in medicine for over a century. Every year, around 700,000 surgical procedures are carried out in the Swedish healthcare system, of which around 15,000 take place at Linköping University Hospital. 

Yet there remains much that we need to learn about how anaesthesia affects the body.

“We know that anaesthesia affects all organs in all people, and that anyone may experience adverse effects. And that includes apparently healthy people who attend for planned procedures. But the risks are much greater for those with many medical problems before the operation.” 

Damage to the heart, for example, is similar to the damage caused by a heart attack. A measurable leakage of a protein called troponin is common in patients who undergo heart attacks. Up to every fifth patient, 10-20%, experience troponin leakage from the heart when undergoing surgery under anaesthesia. But the patient usually leaves hospital without noticing it.

“The risk of being affected by heart attack, stroke or serious disturbances in heart rhythm is approximately three times higher after troponin leakage. Patients seldom feel any symptoms from the leakage, and it’s not something that we measure routinely after the operation.”

Her face takes on a troubled expression:
“Why do patients suffer troponin leakage? We have several studies in progress. We are studying the incidence and outcomes in a Swedish population, and looking at various risk factors. Who is affected? Is it linked to anything in the procedure?”

Blood pressure

They are investigating whether the protein leakage can be linked to previous disease, a fall in blood pressure when under anaesthesia, the duration of the surgery, or other factors.

“This is a purely observational study. It’s difficult to treat symptoms if you don’t understand how they arise.”
The information for the various studies comes from, among other sources, statistics from the Swedish Perioperative Registry (SPOR) and from the Regional Biobank Centre. Methods of anaesthesia have been improved through the years. It was only around 10 years ago that doctors put patients into deep sleep for complicated surgery.

“But today we know that deep sleep is dangerous, and one of the reasons for this is the fall in blood pressure. There is also a correlation with postoperative cognitive problems. Today, we concentrate instead on using the right amount of anaesthetic. Research can help us develop more accurate methods and better dose calculations, monitoring, and follow up.”
Michelle Chew, professor i anestesiologi, här tillsammans med professor Folke Sjöberg, BKV. Fotat på BRIVA, Universitetssjukhuset i Linköping. Photo credit Emma Busk Winquist
With as many as five ongoing multicentre studies, Michelle Chew is convinced that the research will change the healthcare system.

“We are on the verge of discoveries that will make a difference. Several small discoveries that together can change routine medical care.”

"Go to Sweden"

Michelle Chew was born in Malaysia and has lived much of her life in Australia. She has been guest professor at Sydney University and Queensland University. She lives with her family in Malmö and commutes to Linköping, where she not only works in research, but also in clinical practice. Michelle also supervises medical students and doctoral students. When she was a research student in Århus in 2000, her mentor advised her: Go to Sweden to work. The system there is famous for integrating research and clinical practice.

“I thought I would be here for maybe two or three years. But I remained. The research environment at Linköping is just outstanding!”

(Translated by George Farrants)

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