Overview
Some anesthesia gases trigger a fast rise in body heat.
Dantrolene treats it.
Symptoms
Common signs:
- High fever during surgery
- Muscle rigidity
Less common
- Muscle stiffness
Look up a symptom: Fever
When to get medical care
Causes
Gene change.
Does it spread or run in families?
- It isn't contagious. You can't catch it from someone else.
- It can run in families. Tell your doctor if a parent, brother, or sister has it.
Who is more likely to get it
- Family history
Diagnosis
This is diagnosed in the emergency room or hospital.
The exam
A physical exam.
Tests
Tests, if needed:
- Genetic test:
Treatment
Emergency care is needed. While waiting for help:
Self-care
- Treated in the operating room
Prevention
To lower your risk or prevent problems:
- Tell your team about family reactions
Which doctor treats this
- Emergency doctors treat it first, in the ER.
- They may send you to an anesthesiologist, before any future surgery.
Living with it
Support groups and helplines
- Genetic and Rare Diseases Information Center (GARD): Free NIH information on rare diseases, including where to find experts and patient groups.
- National Organization for Rare Disorders (NORD): Patient groups, help finding care, and aid programs for rare diseases.
Back to school, work, or sports
- Recovery time varies. Ask your care team when you can drive, lift, work, and exercise.
Children, pregnancy, and older adults
- Families: Relatives should tell anesthesia teams before surgery.
Pregnancy and breastfeeding
- If you're pregnant or planning to be, tell your prenatal provider about this condition.
- Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
- Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
- Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.
For caregivers
- Go to visits when you can and take notes.
- Keep a list of medicines, allergies, and doctors in one place.
- Learn the warning signs that need fast care.
- Learn CPR. Many hospitals and the Red Cross offer classes.
- Take breaks and ask for help. Caregivers need care too.
Outlook
Fast treatment saves lives.
Getting ready for your visit
Bring a list of your symptoms and medicines.
What to bring
- A list of your medicines and supplements
- Notes on when symptoms started and what makes them better or worse
Questions to ask
- What follow-up care do I need?
- How can I prevent this from happening again?
Research studies
Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.
Search ClinicalTrials.gov for studies on Malignant hyperthermia (reaction to anesthesia)
Sources
Last updated 2026-11-12.