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Why do patients wake up during surgery?

It’s a rare but terrifying experience – you’re under general anesthesia for surgery, fully expecting to be totally unconscious, but suddenly you find yourself awake, aware, and possibly in pain. Why does this happen in some cases, and how can it be prevented?

What is anesthesia awareness?

Anesthesia awareness, also called intraoperative awareness or accidental awareness during general anesthesia (AAGA), refers to becoming conscious during a procedure performed under general anesthesia – when you’re supposed to be fully unconscious. Some estimates suggest it could happen in about 1 or 2 out of every 1,000 surgeries involving general anesthesia.

You may be conscious or semi-conscious during the operation, feeling pain, pressure, tugging, or hearing what’s going on around you. You may even be able to see or recall specific details about surgical instruments, conversations between medical staff, or procedures happening to your body. But usually you are unable to move or indicate to doctors that you are awake.

What are the risks of anesthesia awareness?

Experiencing unintended intraoperative awareness can be very distressing or traumatizing. Psychological effects may include:

  • Anxiety
  • Flashbacks to the traumatic event
  • Nightmares or insomnia
  • Difficulty concentrating
  • Irritability or emotional distress
  • Loss of trust in doctors

Rarely, some people have experienced post-traumatic stress disorder (PTSD) after an episode of anesthesia awareness. The psychological impact seems to be worse when the patient felt pain during the event.

Why does anesthesia awareness happen?

Modern general anesthetics are very effective at producing unconsciousness. But achieving the right dose can be complicated by:

  • Human error – the anesthesiologist misjudges how much anesthesia is needed, administers too little, or makes a dosing/delivery mistake.
  • Equipment failure – there is an issue with the anesthesia delivery machine or monitors.
  • Patient factors – something about the patient’s health or anatomy makes them more resistant to anesthetic drugs.

Certain surgeries tend to have higher rates of anesthesia awareness. For example:

  • Emergency cesarean sections
  • Trauma surgery
  • Cardiac surgery
  • Open heart procedures requiring an intentionally lighter anesthesia called cardiovascular anesthesia

There are also particular risk factors that make someone more prone to experiencing intraoperative awareness during general anesthesia:

Risk Factor Description
Drug abuse history Those with a history of long-term drug or alcohol abuse may have a higher tolerance and require more anesthesia medication.
Chronic pain Patients taking chronic pain medications long-term often develop some tolerance and resistance to anesthetics.
Cardiovascular disease Those with serious heart or circulation conditions are at higher risk because lower doses of anesthesia may be used to reduce cardiac strain.
Trauma patients Severely injured individuals tend to be less responsive to anesthesia drugs due to shock, blood loss, and other factors.
Obesity Calculations of anesthetic dose are based on body weight, but the dose may not fully reach effectiveness in obese patients.
Sleep apnea Those with sleep apnea already have respiratory depression issues, making anesthesia dosing challenging.

How is anesthesia awareness detected?

During surgery under general anesthesia, there are clinical signs the anesthesiology team monitors that can indicate whether the patient is properly unconscious:

  • Heart rate/blood pressure – Increase can signal pain or distress.
  • Movement – The patient moves purposefully or withdraws from surgical stimulation.
  • Tearing – Lacrimation or tear production can occur even in an unconscious patient, but excessive tearing may be a sign of awakening.
  • Perspiration – Unexplained sweating may indicate a sympathetic nervous system response to awareness.
  • Dilated pupils – Pupil dilation can signify pain.

The anesthesiologist will also check the patient’s level of consciousness after surgery before emergence. But anesthesia awareness often goes unnoticed at the time and is only reported by the patient after the fact.

What are the methods for preventing anesthesia awareness?

While there is no way to completely eliminate the risk, the anesthesiology team takes steps to prevent awareness, including:

  • Careful preoperative evaluation of the patient’s health status and risk factors.
  • Tailoring the anesthesia plan and doses appropriately.
  • Ensuring proper functioning of anesthesia equipment pre-operatively.
  • Continuous monitoring of anesthetic depth with techniques like:
    • EEG monitors that measure brain wave activity
    • Technology analyzing patterns in heart rate variability
    • Blood pressure and lacrimation monitors
  • Frequent re-evaluation of anesthetic depth and vitals.
  • Adjusting drug doses as needed during surgery.
  • Postoperative questioning about any memories of intraoperative events.

How is awareness treated perioperatively?

If signs of potential awareness emerge during the procedure, the anesthesiologist will act quickly to increase the anesthetic depth with additional drugs intravenously. They reassure the patient and re-establish a state of general anesthesia.

What should you do if you experience anesthesia awareness?

If you have memories indicating possible anesthesia awareness during your surgery:

  • Report it to your doctor/anesthesiologist so they can document the event and assess you for psychological impacts.
  • Get emotional support and trauma-focused counseling as needed to process the experience and anxiety.
  • Discuss any concerns you may now have about future surgeries and the options available to prevent awareness recurrence.


  • Anesthesia awareness with recall occurs in about 1-2 out of 1,000 patients under general anesthesia when they unexpectedly regain consciousness.
  • Psychological trauma like anxiety and PTSD can result from experiencing pain, paralysis, or distress during accidental intraoperative awareness.
  • Risk factors include trauma surgery, heart conditions, drug/alcohol history, obesity, and more.
  • Vital sign monitoring and anesthesia depth technologies help avoid awareness, but no methods are foolproof.
  • Report any memories of awareness to your doctors and get emotional support to cope with this frightening experience.


While extremely rare, episodes of anesthesia awareness with recall do occasionally happen, especially in higher-risk surgeries and patients. Advances in anesthesia drugs, monitoring, and depth management technology have made intraoperative awakening less likely. Still, it can occur due to human errors, equipment issues, or patient factors. If you experience this, psychological support is advised to help overcome trauma related to the memories. Be sure to inform your anesthesiologist so they can take steps to prevent it from happening again during any future procedures requiring general anesthesia.