Malignant Hyperthermia

(MH)

Objectives

• Define disease/disease process• Identify common triggers• Identify signs and symptoms• Recognize types of treatment

Background

• Allergic Drug Reaction: – A drug allergy occurs when your immune system

reacts to a medication.– You can have an allergic reaction to a drug even if

it caused no reaction in the past.– Some reactions can be severe or life-threatening.

Drug Allergy. (2009). Mayo Clinic. Retrieved from http://www.mayoclinic.com/health/drug-allergy/DS01148

Background• Hypothalamus is the primary

thermoregulatory center for the body– It maintains normal body temperature through

internal regulation of heat production or heat loss.– It regulates temperature in the range of

approximately 97.5°F to 99.4° F.

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

Background

• Vasoconstriction and vasodilatation control blood flow; thus the amount of heat loss to the environment is influenced by vasomotor activity.

• In response to heat gain, sweating and vasodilatation occur, muscles relax, and the person seeks coolness.

• In response to heat loss, shivering and vasoconstriction occur, the muscles tense and the extremities are drawn closer to the body, and the person seeks warmth.

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

What is Fever?• Normal body temperature ranges from person

to person.– Average Body Temperature is 98.6° F– The body’s core temperature lowers with aging.– Fever is called low-grade when the temperature is

above the baseline temperature.

Normal Body Temperature : Rethinking the normal human body temperature. (2006). Harvard Health Publications. Retrieved from http://www.health.harvard.edu/press_releases/normal_body_temperature

What is Fever?• The Society of Critical Care Medicine practice

parameters define fever in the intensive care unit (ICU) as a temperature of 101°F or higher.

McAllen, K. and Schwartz, D. (2010). Adverse drug reactions resulting in hyperthermia in the intensive care unit. Critical Care Medicine, 38 (6), S244-S252.

Malignant Hyperthermia Defined• Malignant Hyperthermia (MH) is a rare,

hereditary condition of the skeletal muscle that occurs on exposure to a triggering agent or agents.– It is often initially misdiagnosed as fever

associated with infection.

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

MH Action

• MH involves instability of the muscle cell membrane, which causes a sudden increase in myoplasmic calcium and skeletal muscle contracture.

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

Rate of Occurrence

• The exact incidence rate of MH is unknown.• It is estimated that MH occurs in 1:5,000 to

1:10,000 children.• It is estimated that MH occurs in 1:50 –

1:100,000 adults.• MH episodes may occur after initial exposure to

the agent, on average, patients require three exposures before an episode of MH is triggered.

McAllen, K. and Schwartz, D. (2010). Adverse drug reactions resulting in hyperthermia in the intensive care unit. Critical Care Medicine, 38 (6), S244-S252.

Who is at Risk?

• Certain populations, such as children and adolescents, appear to be more susceptible.

• MH is rare in infants, and the incidence decreases after age 50.

• Males are more likely to develop MH than females (although mortality is higher among women).

• MH has a familial link, and there appears to be a link between MH and neuromuscular disorders.

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Triggering Agents

• The triggering agents most commonly associated with MH are anesthetic agents, primarily:– Inhalation Anesthetics– Succinylcholine

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

Triggering Agents

Triggering Agents• Sevoflurane• Desflurane• Isoflurane• Halothane• Enflurane• Methoxyflurane• Succinylcholine

Non-Triggering Agents• Local Anesthetics• Narcotics• Ketamine• Nitrous Oxide• Propofol• Etomidate• Benzodiazepines• Non-depolarizing Muscle

Relaxants

Malignant Hyperthermia Association of the United States. (2011).

Signs and Symptoms

• MH is characterized by many signs and symptoms, all of which may not be present in all patients. Though the condition is rare, it is important to recognize the signs and symptoms and to respond quickly.

• The time it takes for onset of symptoms following the end of anesthesia is thought to be between 0 and 40 minutes. Sometimes symptoms will not occur until hours after exposure.

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Early Signs and Symptoms

• Unexplained tachycardia or arrhythmias (usually ventricular tachycardia and premature ventricular contractions)

• Hypercapnia• Masseter muscle (jaw) rigidity following the

administration of succinylcholine (Quelicin) • Generalized flushing and skin that is warm to the touch • Hyperkalemia and acidosis • Generalized muscle rigidity

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Late Signs and Symptoms

• Temperature elevation (can increase rapidly) • Hypoxemia • Cyanosis and skin mottling • Coagulopathy (disseminated intravascular

coagulation) • Rhabdomyolysis (breakdown of muscle tissue)• Myoglobinuria • Kidney failureMalignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Diagnostic Tests

• The Caffeine Halothane Contracture Test (CHCT), a test performed on freshly biopsied muscle, is the “gold standard” for diagnosis.– performed at one of the U.S. testing centers complying with a

standard protocol for the caffeine-halothane contracture test– Nearest location is at Uniformed Services University of the Health

Sciences: Bethesda, MD

• Genetic Testing (Ryanodine Receptor [RYR1] gene sequencing)

Malignant Hyperthermia Association of the United States. (2011).

Management

• Remove triggering agent(s)• Notify physician or anesthesiologist• Administer 100% Oxygen• Give muscle relaxant (e.g., dantrolene)• Apply a cooling device

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

Oxygen• The patient should

immediately be administered 100% oxygen, because Oxygen is rapidly depleted during an acute episode of MH due to increased systemic Oxygen consumption.

• Ventilation should be instituted at a rate of 2-3 times the predicted minute ventilation.

McAllen, K. and Schwartz, D. (2010). Adverse drug reactions resulting in hyperthermia in the intensive care unit. Critical Care Medicine, 38 (6), S244-S252.

Dantrolene• Dantrolene is the only proven drug

to treat MH.• It blocks the release of calcium

from the sarcoplasmic reticulum without affecting calcium uptake.

• It has reduced the mortality associated with MH from 70% to less than 10%.

Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.

Dantrolene• The initial dose of dantrolene at 2.5 mg/kg is

recommended• Repeat dose as needed until symptoms of

hyperthermia and tachycardia resolve.• Doses of 10 mg/kg are usually sufficient.• A diagnosis of MH should be reconsidered if the

patient has not responded after 20 mg/kg has been administered.

**The Malignant Hyperthermia Association of the United States (MHAUS) recommends that each hospital stock 36 vials of Dantrolene.

McAllen, K. and Schwartz, D. (2010). Adverse drug reactions resulting in hyperthermia in the intensive care unit. Critical Care Medicine, 38 (6), S244-S252.

Cooling Measures

• Cooling measures used for a patient with core temperature greater than 102.2° F (39° C) include:– Applying a cooling blanket– Irrigating the stomach through the nasogastric tube– Applying ice to the body surface, especially the neck,

axilla, and groin areas– Rapidly infusing cold 0.9% normal saline I.V. at 1,000 ml/10

minutes for up to 30 minutes

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Nursing Considerations• Don't give calcium channel blockers when

treating arrhythmias. They may cause hyperkalemia or cardiac arrest when used in conjunction with dantrolene.

• The patient will need to be observed in ICU for a minimum of 24 hours (recurrence of MH has been

reported within 48 hours after initial treatment).• Expect to monitor electrolyte levels, ABG values,

CK, myoglobin, and coagulation studies.

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

Nursing Considerations• Provide information to the patient and his

family regarding MH and further precautions.• Emphasize to the patient the importance of

informing any medical personnel treating him that he has a history of MH to prevent further MH episodes.

Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams & Wilkins.

MHAUS Hotline

• The Malignant Hyperthermia Association of the United States (MHAUS) provides education and support to patients and health care providers dealing with MH and has a hotline available if help is needed during a crisis.

In USA and Canada: 1 (800) 644-9737

Malignant Hyperthermia Association of the United States. (2011).

Summary

• MH is a hereditary condition of the skeletal muscle occurring upon exposure to a triggering agent or agents.

• The triggering agents most commonly associated with MH are anesthetic agents.

• The Caffeine Halothane Contracture Test is the gold standard for diagnosis.

• Remove triggering agent when suspected.• Dantrolene is the drug-of-choice for treatment.

References• Drug Allergy. (2009). Mayo Clinic. Retrieved from

http://www.mayoclinic.com/health/drug-allergy/DS01148• Kelly, E. (2005). External Warming/Cooling Devices. AACN Procedure

Manual for Critical Care: Fifth Edition. Elsevier: St. Louis.• McAllen, K. and Schwartz, D. (2010). Adverse drug reactions resulting in

hyperthermia in the intensive care unit. Critical Care Medicine, 38 (6), S244-S252.

• Malignant Hyperthermia Association of the United States. (2011). • Malignant hyperthermia patient care, PACU. (2010). Lippincott Williams

& Wilkins.• Normal Body Temperature : Rethinking the normal human body

temperature. (2006). Harvard Health Publications. Retrieved from http://www.health.harvard.edu/press_releases/normal_body_temperature