Malignant Hyperthermia

Malignant Hyperthermia

• What is it?–Malignant hyperthermia (MH) was the name given to a type of severe reaction under general anesthesia that was first described in 1960

Malignant Hyperthermia

–The ‘malignant’ part of the name MH has proved useful in emphasizing the potentially fatal nature of the reaction

Malignant Hyperthermia

–Monitoring during anesthesia at that time was based on clinical observation and physical signs, without the luxury of today’s advanced equipment. The apparent features of the reactions were, therefore, dominated by a progressive pyrexia that usually led to death

Malignant Hyperthermia

–It is a true EMERGENCY in the Operating Room.

Malignant Hyperthermia

• What is the incidence of developing MH during surgical operations?–Over 80 genetic defects have been

associated with MH.– It is inherited with an autosomal

dominant pattern.–The incidence is 1: 15000 in

pediatric patients& 1: –Usually occurs between the ages

of 2 and 42.

Malignant Hyperthermia

• Triggers:–Drugs

• Sevoflurane• Desflurane• Isoflurane• Halothane• Enflurane

• Methoxyflurane

• Succinylcholine

What are the Clinical Manifestations of MH? Original Concepts:

–All patients have muscle rigidity –High fever, acidosis –High death rate

Current Concepts:–Muscle rigidity may or may not be

present –Temperature is a late sign –End tidal CO2 is an early sign

Malignant Hyperthermia

• Signs of Malignant Hyperthermia– Specific

• Muscle Rigidity • Increased CO2 Production • Rhabdomyolysis • Marked Temperature Elevation

– Non Specific • Tachycardia • Tachypnea • Acidosis (Resp/Metabolic) • Hyperkalemia

Malignant Hyperthermia

• What causes an episode of MH?–MH susceptible persons have a gene mutation that results in the presence of abnormal proteins in muscle cells.

–When these persons are exposed to certain anesthetic agents there is an abnormal release of calcium inside the muscle cell.

Malignant Hyperthermia

Causes Cont’d:–This calcium release results in sustained muscle contraction and an abnormal increase in energy utilization and heat production.

Malignant Hyperthermia

Causes Cont’d:–This contraction will cause the muscle to run out of energy and eventually die releasing a large amount of potassium into the blood- stream.

–This release of potassium will lead to heart rhythm abnormalities as well as lethal rhythms such as V-fib and V- tach.

Malignant Hyperthermia

• Causes Cont’d:–At the onset of muscle cell death,

the pigment myoglobin is also released and is potentially toxic to the kidneys.

– If left untreated the patient will experience cardiac arrest, kidney failure, blood coagulation problems, internal hemorrhage, brain injury, and possibly death.

Malignant Hyperthermia

• How is it treated?– Early identification is essential to a

positive outcome.• Procedure is stopped immediately (or

ASAP).• All anesthetics are discontinued

immediately and anesthesia provider delivers 100% oxygen and flushes the CO2 circuit with 100% oxygen.

• Anesthesia provider hyperventilates the patient with 100% O2.

• The circulating nurse will initiate the MH protocol and call for additional OR support.

Malignant Hyperthermia

• Treatment Cont’d:–Circulator will continue to assist

anesthesia and draw blood, insert IV lines etc and assign a dantrolene nurse.

–The Dantrolene nurse will retrieve or assign someone to retrieve the MH cart. This nurse will be responsible for the mixing and administration of the dantrolene.

Malignant Hyperthermia

Treatment Cont’d:–A third nurse will be assigned as

the medication nurse and will bring the crash cart into the OR room. This nurse will function along side the anesthesia person to assist with correction of metabolic disturbances. (insulin, glucose, calcium, antiarhythmic agents, and diurectics)

Malignant Hyperthermia

Treatment Cont’d:–A fourth nurse will be responsible

for cooling the patient. This nurse will place ice packs, hypothermia blankets and cooled fluids. Remember LR is NOT given. Cooling is stopped when the core temp reaches 100 degrees F.

–Once these procedures have been completed, the patient will be transported to ICU.

Dantrolene for MH crisis

• Recommended dosing is 2.5mg/kg• Typical packaging : 20 mg/60 ml =

1 mg/3ml • 70 kg patient:

2.5 mg/kg = 175 mg or 525 ml (9 vials)

Give as soon as diagnosed.Dantrolene is the only specific

treatment for MH

Prevention of Malignant Hyperthermia

• Preoperative personal/family history of anesthetic problems, neuromuscular disorders

• Temperature/end tidal CO2 monitoring during general anesthesia

• Recognition of masseter rigidity

Prevention of Malignant Hyperthermia

• Investigation of unexplained tachycardia, hypercarbia, hyperthermia

• Availability of Dantrolene • Avoiding MH triggers in MH

susceptibles • Using Succinylcholine in indication

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