Nursing care
Malignant Hyperthermia nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Malignant hyperthermia is a hypermetabolic crisis triggered by volatile anaesthetics or succinylcholine, and the earliest sign is a rising end-tidal CO2, not fever. Stop the trigger agent immediately, call for help, and get dantrolene drawn up and running while cooling measures and monitoring continue.
The clinical picture
Malignant hyperthermia is a rare but life-threatening pharmacogenetic reaction, usually to volatile inhaled anaesthetics such as sevoflurane or to the depolarising muscle relaxant succinylcholine. A genetic mutation, most often in the RYR1 gene, causes uncontrolled calcium release in skeletal muscle. The result is sustained muscle contraction, a hypermetabolic state, and a cascade of acidosis, hyperkalaemia and heat production that can overwhelm the body within minutes.
The classic teaching image is a spiking temperature, but temperature is a late finding. Masseter muscle rigidity after succinylcholine, tachycardia out of proportion to anaesthetic depth, and mottled or cyanotic skin can all appear before the core temperature climbs. A patient can be in crisis on the table with a normal temperature reading, which is exactly why relying on the thermometer first is the wrong sequence.
Assessment: what to look for and in what order
Rising end-tidal CO2 on capnography is the earliest and most reliable sign, often the first clue before anything else changes. It reflects the surge in metabolic carbon dioxide production and typically climbs faster than any anaesthetist would expect from ventilation settings alone. Any unexplained, sustained rise in ETCO2 during a case involving a trigger agent should prompt immediate suspicion of MH, not a wait-and-see approach.
After ETCO2, check for unexplained tachycardia and tachypnoea, then masseter or generalised muscle rigidity. Skin colour and temperature come next: mottling, cyanosis, and a temperature that may be normal early but can rise as fast as 1 to 2 degrees Celsius every five minutes once established. Arterial blood gas will show a mixed respiratory and metabolic acidosis, and serum potassium and creatine kinase both rise sharply as muscle breaks down. Myoglobinuria, seen as dark or tea-coloured urine, signals rhabdomyolysis and impending renal injury.
Immediate interventions
Stop the trigger agent immediately and switch to a clean anaesthesia circuit or ventilator if one is available. Someone activates the MH hotline or the unit's MH protocol and calls for the malignant hyperthermia cart while dantrolene is drawn up. Dantrolene sodium is the only definitive treatment; it works by inhibiting calcium release from the sarcoplasmic reticulum, and the initial dose is 2.5 mg/kg IV, repeated every 5 to 10 minutes until symptoms resolve, with total doses sometimes exceeding 10 mg/kg. It does not wait for the call to finish; drawing it up and calling for help happen in parallel, not in sequence.
Hyperventilate with 100% oxygen at high flow to blow off the excess CO2 and correct hypoxaemia. Begin active cooling with cold IV saline, ice packs to the groin, axillae and neck, and cooled irrigation of open body cavities if the patient is mid-surgery, but stop cooling once the temperature falls below 38°C to avoid overshoot into hypothermia. Treat hyperkalaemia with insulin and dextrose, calcium chloride and sodium bicarbonate as ordered, and treat arrhythmias with standard agents while avoiding calcium channel blockers, which interact dangerously with dantrolene.
Ongoing nursing management
Once the acute crisis is controlled, the patient moves to an ICU setting for at least 24 hours, because MH can recur even after apparent resolution. Continuous cardiac and temperature monitoring continues, along with hourly urine output to watch for the dark, concentrated urine of myoglobinuria. Maintaining a brisk urine output with IV fluids protects the kidneys from the myoglobin load, and repeat CK and renal function tests track the extent of muscle injury.
Dantrolene continues at 1 mg/kg every 4 to 6 hours, or by continuous infusion, for at least 24 hours to prevent recrudescence. Watch for muscle weakness and respiratory depression from the dantrolene itself, since it can impair the patient's ability to protect their airway or breathe adequately. Serial arterial blood gases and electrolytes guide ongoing correction of acidosis and hyperkalaemia, and coagulation studies are checked, since disseminated intravascular coagulation is a recognised late complication.
Patient and family education
Before discharge, the patient and family need to understand that MH susceptibility is inherited in an autosomal dominant pattern, so first-degree relatives carry meaningful risk even without a prior anaesthetic exposure. Referral to a malignant hyperthermia testing centre for muscle biopsy contracture testing or genetic testing lets relatives find out their status before they ever need anaesthesia themselves.
Every MH-susceptible patient should be fitted with a medical alert bracelet and should tell every future anaesthesia provider, dentist included, about the diagnosis before any procedure requiring sedation or general anaesthesia. Safe alternative agents exist, including propofol, nitrous oxide, and non-depolarising muscle relaxants, and a trigger-free anaesthetic plan can be arranged in advance. Reassure the family that with prompt recognition and dantrolene, mortality has fallen from over 70% decades ago to well under 5% today.
How this appears on the NCLEX
NCLEX items on malignant hyperthermia test whether you recognise the earliest sign and the correct first action, not just the definition. Expect a scenario describing a patient under general anaesthesia with a climbing end-tidal CO2 and tachycardia, asking what the nurse should suspect or do first; the correct answer points to MH and stopping the trigger agent, not waiting for a temperature change.
Priority-setting questions often ask you to sequence interventions: stop the anaesthetic, call for help and dantrolene, hyperventilate with 100% oxygen, then cool. Pharmacology items test dantrolene's mechanism, dosing pattern, and the need for continued dosing after the crisis resolves. You may also see questions on genetic counselling and the autosomal dominant inheritance pattern, and on distractor answers involving antipyretics, which have no role here because the fever is not infection-driven.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our med-surg practice questions are the closest set to what this page covers.
One question from the med-surg set
A client with chronic obstructive pulmonary disease has an oxygen saturation of 88% on 2 L/min via nasal cannula and is alert with no distress. What should the nurse do first?
Rationale
In COPD a saturation of 88–92% is the therapeutic target, not an emergency, and this client is alert with no distress. The first action is the independent nursing intervention that is least invasive and most likely to help: sit them up and reassess. Turning the oxygen up to 6 L/min risks blunting the hypoxic drive, and calling rapid response or drawing an ABG escalates ahead of an assessment you have not finished.
Answer: B
Common questions
What is the first sign of malignant hyperthermia?
A rising end-tidal CO2 on capnography is typically the earliest and most reliable sign, appearing before the temperature climbs. It reflects the sudden surge in metabolic CO2 production from uncontrolled muscle contraction and often precedes tachycardia, rigidity, and the temperature spike people associate with MH.
What is the antidote for malignant hyperthermia?
Dantrolene sodium is the definitive treatment. It works by blocking calcium release from the sarcoplasmic reticulum in skeletal muscle, given as an initial IV dose of 2.5 mg/kg, repeated every 5 to 10 minutes until symptoms resolve.
Which anaesthetic drugs trigger malignant hyperthermia?
Volatile inhaled anaesthetics, including sevoflurane, isoflurane and desflurane, and the depolarising muscle relaxant succinylcholine are the recognised triggers. Propofol, nitrous oxide and non-depolarising muscle relaxants are considered safe alternatives for susceptible patients.
How long does a patient need monitoring after a malignant hyperthermia episode?
At least 24 hours in an ICU setting, because recrudescence can occur even after the initial crisis appears resolved. Continuous cardiac and temperature monitoring, hourly urine output, and repeat dantrolene dosing continue throughout that window.
Is malignant hyperthermia genetic?
Yes, it is most commonly linked to a mutation in the RYR1 gene and inherited in an autosomal dominant pattern. First-degree relatives of an affected patient should be referred for contracture testing or genetic testing before their own anaesthesia exposure.
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