Why it is safer to undergo cardiac surgery in the afternoon than in the morning


Patients who undergo cardiac surgery in the afternoon have less risk of potentially lethal complications than those who are operated on in the morning, new research says.

This, the scientists say, is due to the biological clock, or circadian rhythm.

The biological clock is the reason why we feel sleepy at night but it also takes care of important changes in the way our organism works.

The study, published in the medical journal The Lancet , shows that in the afternoon the heart is stronger and better able to face surgery than in the morning.

And he says that this is not because surgeons are more tired in the morning.

There are operations that require doctors to stop the heart, such as heart valve replacements. And in these the organ is subjected to stress because the flow of oxygen to the heart tissue is reduced.

Doctors and researchers investigated complications after surgery, including heart attack, heart failure, or death.

They found:

  • 54 of 298 morning patients had adverse events
  • 28 of 298 evening patients had adverse events
  • Evening patients had about half the risk of complications
  • With every 11 patients that are operated in the afternoon, a major event can be avoided

One of those involved in the investigation, Professor Bart Staels of the Pasteur Institute in Lille, told the BBC: “We do not want to scare people into having surgery, it’s to save lives.”

But Professor Staels adds: “If we can identify patients who are at high risk, they will definitely benefit if they are scheduled in the afternoon and that would be reasonable.”

It has been shown that obesity and type 2 diabetes increase the risk of complications after surgery.

Heart strength

It is known that the health of the heart fluctuates in the course of the day.

The risk of a stroke or stroke is highest in the early morning hours, while the heart and lungs function at peak capacity in the afternoon.

Dr. John O’Neill, of the Molecular Biology Laboratory of the Medical Research Council of the United Kingdom, says: “Scientifically it is not hugely surprising, because like any other cell in the body, the heart cells have circadian rhythms that make up their activity. ”

“Our cardiovascular system has its highest performance during the middle or end of the afternoon, which explains why professional athletes often record their best performance during that period.”

Other possible explanations for these findings include the fact that surgeons are tired in the morning or that their own biological clocks affect their surgical capabilities, particularly if they are not “morning people”.

The role of surgeons

But Professor Staels says the researchers went to great lengths to show that the difference in survival rates is not linked to surgeons.

The French team also experimented on samples of cardiac tissue from patients and showed that they beat more quickly in the afternoon.

And a DNA analysis in the samples found 287 genes whose activity showed a circadian rhythm – of growth and of decrease – during the day.

They then studied mice and used experimental drugs to alter the activity of one of those genes and apparently reduced the risk of death.

Professor Staels says: ” We believe that we have identified a potential way to get around the disturbing observation that morning operations lead to more complications .”

However, that will require more studies to confirm it.

Researchers are also studying whether circadian rhythms have an impact on the survival of other types of surgery.

Dr. Mike Knapton, of the British Heart Foundation, says: “Thousands of people are now undergoing open heart surgery in the UK If this finding can be replicated in other hospitals this could help surgeons plan their list of operations for cardiac surgeries that are not urgent. ”

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