Malignant Hyperthermia 🔥

malignant hyperthermia

A rare life-threatening inherited skeletal muscle disorder that is triggered by certain anesthetic agents

MH is most commonly seen during

Shortly after surgery involving general anesthesia

what is the inheritance of MH?

Autosomal dominant

cause of MH

Mutation of the ryanodine receptor which leads to uncontrolled calcium release in skeletal muscle

what medication is given to help with the mortality of MH?

Dantrolene

Dantrolene works by

muscle relaxant that works by inhibiting calcium release from the sarcoplasmic reciculum in muscle cells, efficiently counteracting, the hyper metabolic state associated with MH

patient at high risk for MH

1. Family history

2. Unexplained death during anesthesia by a family member

3. Strong, bulky muscular

4. History of muscle cramps or muscle weakness

5. Prior unexplained high fever during surgery

inhalation and aesthetics that might trigger MH

1. Halothane

2. Enflurane

3. Isoflurane

most common trigger at anesthetic

Succinylchonine

non-anesthetic triggers for MH

1. Emotional stress

2. Heat stroke

3. Strenuous exercise

4. Trauma

5. Neuroleptic malignant syndrome

6. Certain medications

what non-anesthetic certain medications can cause MH

1. Epinephrine

2. Atropine

3. theophylline/aminophylline

4. Cardiac glycosides (digitalis)

triggering agents cause excessive

Calcium release from the sarcoppasmic reticulum

excessive calcium release can lead to

Sustained muscle contraction, resulting in hyper, metabolic state and rapid consumption of oxygen

rapid consumption of oxygen and ATP with increased CO2 production and heat generation

caused by excessive calcium release

The excessive calcium release can lead to

1. Metabolic and respiratory acidosis

2. Hyperkalemia

3. CNS damage

4. Cardiac arrest arrhythmia

5. rhabdomyolysis

clinical manifestations

Early signs are the MOST IMPORTANT

1. Tachycardia

2. Rising entitled CO2 (hypercapnia)- earliest respiratory sign

3. Muscle rigidity (especially in jaw)

4. Tachypnea

Progressive/late signs

Rapidly increasing body temperature

Ventricular arrhythmia

Hypotension

Decreased cardiac output

Oliguria

Cardiac arrest

NCLEX KEY POINT

Fever is a

LATE SIGN

Do not wait for hypothermia to suspect MH

immediate medical management goals

1. Stop hypermetabolism

2. Reverse acidosis

3. Correct electrolyte imbalance

4. Prevent organ failure

5. Lower body temp

Dantrolene sodium (dantrium)

1. Relaxes, skeletal muscle

2. Reduces calcium release

3. Significantly lowers mortality

additional interventions to treat MH

1. discontinue triggering anesthetics immediately

2. 100% oxygen

3. Active cooling measure

4. Treat dysrhythmias

5. IV fluid

6. Monitor labs

what labs would you monitor with MH?

ABG’s

Electrolytes

creatinine

Urine myoglobin

which fluids would you administer with a patient with malignant hypothermia?

1. Cooling fluid fluids

2. Bicarbonate to reduce metabolic acidosis

3. Insulin and glucose treat hyperkalemia

how long can an image occur after anesthetic are given?

10 to 20 minutes after induction and up to 24 hours postop

after administration of succinylcholine, a patient starts with a high fever and muscle rigidity. What medication do you prepare to give?

IV. Dantrolene.

Order of interventions

1. notified provider first

2. Prepared to administer Dantrolene

3. Cooling measures and oxygen

High risk screen for MH

1. Prior reaction to general anesthesia

2. Blood relative with significant reaction to general anesthesia

3. Alcoholics

A 28-year-old male undergoing general anesthesia with succinylcholine suddenly develops muscle rigidity and a rapid rise in temperature. Which of the following is the priority nursing action?

A. Administer dantrolene sodium
B. Apply a cooling blanket
C. Obtain arterial blood gases
D. Discontinue anesthesia

✅ Correct answer: D. Discontinue anesthesia
Rationale: The first step is to stop the triggering agents (volatile anesthetics and succinylcholine). Dantrolene is then administered immediately afterward.

Which medication is used as the specific antidote for malignant hyperthermia?

A. Dantrolene sodium
B. Diazepam
C. Methocarbamol
D. Midazolam

✅ Correct answer: A. Dantrolene sodium
Rationale: Dantrolene directly acts on skeletal muscle to reduce calcium release, reversing the hypermetabolic state.

The nurse recognizes which laboratory finding as consistent with malignant hyperthermia?

A. Hypocapnia and alkalosis
B. Hypercapnia and metabolic acidosis
C. Hypokalemia and alkalosis
D. Hypocalcemia and metabolic alkalosis

✅ Correct answer: B. Hypercapnia and metabolic acidosis
Rationale: The rapid increase in CO₂ and lactic acid production leads to respiratory and metabolic acidosis.

Which of the following patients is at highest risk for malignant hyperthermia?

A. Patient with cystic fibrosis
B. Patient with Duchenne’s muscular dystrophy
C. Patient with a history of thyroid storm
D. Patient with a history of hypothermia

✅ Correct answer: B. Duchenne’s muscular dystrophy
Rationale: MH has a genetic predisposition and is more likely in patients with myopathies or a family history of MH.

A nurse notes that a postoperative patient who received general anesthesia exhibits a temperature of 104°F, muscle rigidity, and tachycardia. What is the nurse’s initial nursing intervention?

A. Notify the surgeon immediately
B. Assess urine output
C. Initiate cooling measures
D. Stop volatile anesthetics

✅ Correct answer: D. Stop volatile anesthetics
Rationale: Removing the trigger (anesthetic gas or succinylcholine) is the first step. Cooling and dantrolene follow immediately.

During a malignant hyperthermia crisis, which IV fluid is most appropriate to administer?

A. D5W
B. Lactated Ringer’s
C. Normal saline
D. Albumin

✅ Correct answer: C. Normal saline
Rationale: Normal saline is used to maintain perfusion and flush myoglobin from kidneys; LR is avoided because it contains calcium which may exacerbate the crisis.

A nurse is preparing the operating room for a patient with a known history of malignant hyperthermia. Which preoperative intervention is appropriate?

A. Use of a vapor-free anesthesia machine
B. Administration of succinylcholine for muscle relaxation
C. Avoidance of propofol
D. Pre-warming blankets

✅ Correct answer: A. Use of a vapor-free anesthesia machine
Rationale: An MH-susceptible patient must be anesthetized with non-triggering agents and a machine free of volatile anesthetics.

Which of the following assessment findings would the nurse expect first in a patient developing malignant hyperthermia?

A. Elevated temperature
B. Muscle rigidity
C. Tachycardia and rising end-tidal CO₂
D. Hypotension

✅ Correct answer: C. Tachycardia and rising end-tidal CO₂
Rationale: Early signs are unexplained tachycardia and elevated end-tidal CO₂ (ETCO₂); hyperthermia develops later.

The nurse knows that an important post-crisis action after malignant hyperthermia resolution is:

A. Discharge once temperature normalizes
B. Avoid documented report to family
C. Inform the patient and family of genetic testing recommendations
D. Administer more general anesthesia as needed

✅ Correct answer: C. Inform the patient and family of genetic testing recommendations
Rationale: MH is autosomal dominant; genetic counseling/testing should be offered to relatives.

A patient recovering from malignant hyperthermia is being closely monitored. Which finding requires immediate nursing intervention?

A. Urine output 20 mL/hr and dark-colored urine
B. Heart rate 90 bpm
C. Temperature 98.7°F
D. Mild muscle soreness

✅ Correct answer: A. Urine output 20 mL/hr and dark-colored urine
Rationale: Dark urine suggests myoglobinuria, which can cause renal failure; increased IV fluids and renal protection are needed.