Is it normal to get the shakes after anesthesia? Unpacking postanesthetic shivering

October 9, 2025 •

4 min read

Postanesthetic shivering (PAS) is a common phenomenon, with studies reporting it affects between 20% and 70% of patients recovering from general anesthesia. While it can feel alarming and intense, getting the shakes after anesthesia is a normal physiological response as the body regains its thermal equilibrium.

Quick Summary

Postanesthetic shivering is a widespread side effect of anesthesia, caused primarily by hypothermia but also influenced by pain, stress, and residual anesthetic effects. It is a temporary condition that healthcare teams manage effectively with both warming measures and medication.

Key Points

Common and Normal: Postanesthetic shivering is a common physiological response, affecting a significant number of patients and is typically temporary.
Hypothermia is the main driver: Anesthesia impairs the body's temperature control, and the resulting drop in core temperature triggers the shivering reflex to generate heat.
Multiple contributing factors: Beyond hypothermia, other factors like pain, surgical stress, and the type of anesthesia used can trigger shivering.
Risks are higher for at-risk patients: While harmless for most, shivering increases oxygen consumption and cardiovascular workload, which can be dangerous for individuals with heart or lung issues.
Effective management strategies exist: Treatment involves both non-pharmacological methods like warming blankets and fluids, and various pharmacological options like meperidine and clonidine.
Communication with caregivers is key: Alerting your care team if you feel cold or experience shivering allows for prompt intervention to ensure your comfort and safety during recovery.

Understanding Postanesthetic Shivering (PAS)

Postanesthetic shivering is the involuntary, rhythmic contraction of skeletal muscles experienced by many patients as they recover from anesthesia. It is often misinterpreted by patients as a sign of something serious, but it is typically a transient and managed part of the recovery process. This shivering can range from mild facial twitching to gross muscular activity involving the entire body and typically lasts 20 to 30 minutes.

The physiological reasons behind shivering

Anesthetics, particularly general anesthetics, disrupt the body's normal thermoregulation—the complex system that maintains core body temperature. Here’s a breakdown of the key factors that contribute to this response:

Anesthetic-induced hypothermia: During anesthesia, your body's temperature set point is lowered. As the anesthetic wears off, this set point returns to normal, but your core body temperature is still low from being in a cool operating room. This discrepancy triggers a natural reflex: shivering, which generates heat through muscle contractions to warm the body back up.
Heat redistribution: Anesthetic agents cause vasodilation, or the widening of blood vessels. This allows warm blood to move from the core of the body to the periphery (limbs). This process results in a rapid initial drop in core temperature and contributes to the feeling of being cold.
Pain and stress: The surgical procedure itself and the stress of awakening from anesthesia can contribute to shivering. Pain signals traveling through the spinal cord can also activate temperature regulation pathways, sometimes independently of body temperature.
Neuroaxial anesthesia: Shivering is also common after regional anesthetics like spinal or epidural blocks, with some studies reporting a higher incidence than general anesthesia. The block inhibits thermoregulatory signals below the level of the block, leading to redistribution hypothermia. The cooling effect of fluids injected into the nervous system may also play a role.

Potential complications of postanesthetic shivering

While typically harmless, vigorous shivering can place significant metabolic stress on the body. This is particularly concerning for patients with underlying cardiopulmonary conditions, as shivering can increase oxygen consumption by 300% to 400%. Other potential adverse effects include:

Increased oxygen demand: The body’s need for oxygen dramatically increases to fuel the muscle contractions, potentially leading to hypoxemia (low oxygen levels).
Cardiovascular strain: Shivering increases heart rate and blood pressure, which can be dangerous for patients with compromised heart function.
Increased patient discomfort and pain: Shivering can cause significant distress, especially for patients with surgical incisions, potentially exacerbating wound pain.
Interference with monitoring: The physical movements from shivering can disrupt standard medical monitoring equipment, such as electrocardiograms and blood pressure cuffs, leading to inaccurate readings.
Surgical site complications: In rare cases, severe shivering could potentially stress surgical repairs.

Management and Prevention of Postanesthetic Shivering

Healthcare professionals prioritize preventing and treating shivering to ensure patient comfort and safety. A combination of non-pharmacological and pharmacological methods is typically used.

Non-pharmacological interventions

These strategies focus on restoring and maintaining the patient’s body temperature through physical means:

Active surface warming: Forced-air warming blankets are one of the most effective methods to combat hypothermia. They circulate warm air over the patient's body to increase temperature.
Warmed intravenous fluids: The administration of warmed IV fluids can help prevent a further drop in core body temperature, especially during lengthy procedures or in cases of significant fluid loss.
Warming blankets: Simple cotton blankets are often applied immediately after surgery to provide passive insulation and comfort.
Adjusting the environment: While less impactful than active warming, maintaining a comfortable operating and recovery room temperature can contribute to preventing shivering.

Pharmacological treatments

For more persistent or severe cases, or as a preventative measure, various medications can be administered to reduce the shivering threshold and manage symptoms. Meperidine has historically been considered highly effective, but other options are now widely used due to varying side-effect profiles.

Comparison of common anti-shivering medications


Medication	Mechanism	Efficacy for Shivering	Common Side Effects
Meperidine (Pethidine)	Kappa-opioid and alpha-2 receptor agonist.	Highly effective, rapid onset.	Nausea, vomiting, respiratory depression, sedation. Not recommended with MAOIs.
Tramadol	Weak mu-opioid agonist; inhibits reuptake of serotonin and norepinephrine.	Effective, especially for moderate shivering.	Nausea, vomiting, dizziness.
Clonidine	Alpha-2 adrenergic agonist.	Effective for prevention and treatment.	Sedation, bradycardia, hypotension.
Ondansetron	Serotonin (5-HT3) receptor antagonist.	Effective in some cases, with a good safety profile.	Headache, dizziness, constipation.
Ketamine	N-methyl-D-aspartate (NMDA) receptor antagonist.	Effective for treating shivering, often used in low doses.	Hallucinations, dysphoria, increased heart rate.
Magnesium Sulfate	Calcium antagonist and NMDA receptor antagonist.	Effective for spinal anesthesia shivering.	Mild muscle relaxant, can cause hypotension.

Conclusion: Your recovery experience

Experiencing shivering after anesthesia is a very common and normal part of the body's recovery process. It is a sign that your body's temperature regulation system is returning to normal function and working to warm you. While the sensation can be startling and uncomfortable, your medical team is well-equipped to both prevent and treat it using a variety of effective techniques.

Open communication with your healthcare providers is key. If you are concerned about shivering after a procedure, or if you feel unusually cold at any point during your hospital stay, inform a nurse immediately. Being proactive allows your care team to intervene quickly with warming measures or medication, ensuring a smoother and more comfortable recovery. For more information on anesthesia side effects and patient safety, you can consult resources like the American Society of Anesthesiologists website.

Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for questions about your personal medical condition.

Frequently Asked Questions

Postanesthetic shivering is typically short-lived, with most episodes resolving within 20 to 30 minutes after waking up. In some cases, it may last for a few hours, but it is usually temporary.

No, shivering is not typically a sign of a serious problem. It is a common and normal reaction to the effects of anesthesia. However, for patients with heart or lung conditions, vigorous shivering is monitored closely to prevent complications from increased oxygen demand.

The primary cause is anesthetic-induced hypothermia, where the body's temperature drops during surgery. As the anesthesia wears off, the body's natural temperature regulation system kicks in, causing muscle contractions (shivering) to generate heat.

Yes, shivering can occur after both general anesthesia and regional anesthetics, like spinal or epidural blocks. Regional anesthesia can cause heat redistribution by dilating blood vessels, leading to shivering.

Healthcare teams use a combination of methods, including non-pharmacological measures like forced-air warming blankets and warmed IV fluids, and pharmacological treatments such as meperidine or clonidine, to manage shivering.

Several factors can increase the risk, such as prolonged surgery, a cool operating room environment, emergency procedures, and lower BMI.

Inform your nurse or healthcare provider immediately if you feel cold or are shivering. They can provide warm blankets, check your temperature, and administer medication if necessary to ensure your comfort and safety.