Malignant Hyperthermia

Resident: Roberts
Date: 4/8/10
Article title: Malignant Hyperthermia
Author: Fortunato-Phillips, Nancymarie
Journal: Critical Care Nursing Clinics of North America
Volume: 12, Number: 2,
Year 2000, June

Discussions
What is Malignant Hyperthermia?
MH is a sudden pharmacogenic hypermetabolic crisis involving uncontrolled calcium release from skeletal muscle that causes potentially fatal consequences. It is triggered by administration of a depolarizing muscle relaxant such as succinylcholine, or a volatile inhalation anesthetic such as halothane, sevoflurane or desflurane. It has been shown to occur as an autosomal dominant train in families, thus each child of a person who is susceptible to MH has a 50% chance of inheriting the gene for this predisposition.

Pathophysiology of MH
A triggering agent causes uncontrolled release of calcium from the sarcoplasmic reticulum causing sustained muscle contraction and hypermetabolism. During this state, large amounts of oxygen and energy are being consumed resulting in an increase in carbon dioxide in the blood and the patient begins to take rapid deep breaths if he is not under the influence of neuromuscular blockade. The prolonged hypermetabolic state of muscular contraction causes rhabdomyolysis resulting in a release of free myoglobin that begins to build up as sludge in major organs, particularly the renal tubules which leads to renal failure. In addition serum potassium increases causing myocardial irritation resulting in sinus tachycardia and dysrythmias.

Signs and symptoms
The earliest sign of a potential crisis in process could be trismus noted during intubation, followed by increased end tidal carbon dioxide, ventricular dysrythmias and tachypnea.

Treatment
All inhalational anesthetics and depolarizing muscle relaxants are stopped and the patient is placed on 100% oxygen. The surgical site should be closed as quickly as possible. The body should be lavaged with cool saline. The drug, dantrolene sodium ,should be administered at a bolus rate of 2.5mg/kg – 10mg/kg until stabilization occurs. The patient should be placed in critical care and DS should be administered at 1mg/kg for the next 48 to 74 hours to prevent a relapse of MH.

Assessment

Good article!