Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I had surgery when woke up I felt like I only had 20% energy & felt extremely tired. Is this a common sensation? Why do people feel so tired after surgery?

share|improve this question
I think you were feeling the aftermath of the narcosis. – Chris Jan 1 '14 at 10:54
Of course this is common. You can account anesthesia to be responsible for this. Also if you were asked not to eat anything for some prescribed time before and after the surgery, as is usually done, the body is already in need for some energy and at the same time it is also trying to come back to the conscious state. It has to make good efforts. Surgery is a type of stress condition for the body! – Shefali Jan 2 '14 at 7:34

Answers in comments are correct. The tail effect of hypnotic drugs combined to opiates given for pain relief will make you feel really tired just after surgery.

But if you are referring to a more long-term effect, such as feeling tired for several days after surgery, then several factors combine:

  • psychological stress
  • physical deconditioning: inpatients usually do not move much. And even a few days of immobility will have a huge impact on your physical abilities. That is why in modern medicine, every effort is made to make the patient move as quickly as possible. Intensive physical therapy, readaptation therapy, and fast-track pathways are a result of this effort.
  • physical stress: undergoing surgery is a physical effort. Your body needs to accommodate for large shifts in volemia, positive pressure ventilation, reaction to pain (which still takes place during anesthesia), etc. The physical abilities of the patient are evaluated by the anesthesiologist for that reason, using MET effort units (often measured in number of flights of stairs you can climb without stopping). People with angina pectoris or diagnosed atherosclerosis can also be submitted to an ergometric test (cycling) or stress echocardiography/scintigraphy to evaluate if their heart can tolerate the physical stress of surgery.
share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.