Malignant Hyperthermia

Malignant Hyperthermia

Definition : a metabolic disease of the muscle, a hypermetabolic state caused by exposure of susceptible individuals to known trigger agents.

Malignant Hyperthermia

Sustained, significant hypermetabolismInherited componentAbnormal handling of intracellular

calcium levels“Triggered” by pharmacologic agents ,

possibly by heat/exercise

Trigger Agents for MH

MH Trigger AgentsPotent Volatile Anesthetics (eg.

halothane, sevoflurane, desflurane)Succinylcholine

Not MH TriggersIntravenous agentsOpioidsNon-depolarizing agentsKetaminePropofolAnxiolytics

Spectrum of Presentations of Malignant HyperthermiaThe classic caseMasseter muscle rigidityAssociated with muscle disordersMH without anesthesia

Signs of Malignant Hyperthermia

SpecificMuscle RigidityIncreased CO2 ProductionRhabdomyolysisMarked Temperature Elevation

Non SpecificTachycardiaTachypneaAcidosis (Resp/Metabolic)Hyperkalemia

Summary of Clinical Signs

Muscle Rigidity and MH

Jaw muscle rigidity may occur after succinylcholine

More common in children Presages MH in 20-30% Generalized rigidity not always present When present, regularly associated with MH

susceptibility With muscle breakdown and creatine kinase

above 20,00IU, the likelihood of MH is very high.

Masseter Muscle Rigidity

Stop Inhalation Agent

No further succinylcholine

Continue with

nontrigger agents Awaken

follow ET C02 patient

Observe in ICU for 24 hours

CK/electrolytes,Myoglobin

Dantrolene as needed

Recommend for biopsy

Disorders Associated with MH Susceptibility

Central Core DiseaseEvans MyopathyHypokalemic Periodic Paralysis?sodium channel myotonias

Mimics of Malignant Hyperthermia

Fever (without rigidity)– Thyrotoxicosis– Sepsis– Pheochromocytoma– Iatrogenic overheating– Anticholinergic syndrome– Faulty equipment– Tourniquet (children)

Fever and muscle symptoms– NMS– Hypoxic encephalopathy– Ionic contrast agents

in CSF– Cocaine, amphetamine, ecstasy

What Tests Are UsedTo Diagnose MH?

Current Concepts: Halothane, caffeine contracture test is the

only gold standardCurrent Investigations: Molecular genetics Nuclear magnetic resonance for assessing ATP and

creatine phosphate with/without exercise in vivo Calcium flux measurement in cultured muscle cells Local increase in pC02 following IM caffeine EMG changes in MH patients

What is the Incidence of MH?

Original Concepts:– Rare. One in 50,000 anesthetics

Current Concepts:– Clinically based information:

One in 20,000 to 50,000 anesthetics depending on drugs, population

– Molecular Genetics based information: MH trait in 1 in 2,000-3,000 patients. Low penetrance

Immediate Therapyof Malignant Hyperthermia Have a plan! Discontinue inhalation agents, Succ Hyperventilate with 100% 02

Bicarbonate 1-2 mg/kg as needed Get additional help Dantrolene 2.5mg/kg Push. Repeat PRN Cool patient: gastric lavage, surface, wound Treat arrhythmias-do not use calcium channel

blockers Arterial or venous blood gases Electrolytes, coagulation studies

Treatment of Malignant Hyperthermia - Acute

Dantrolene-1 The only specific treatment for MH Administer as soon as diagnosis made 20mg/bottle-dissolve with 60ml sterile water Shake vigorously or warm bottles to dissolve Give 2.5mg/kg STAT Repeat as needed to control signs of MH

Treatment of Malignant Hyperthermia

Dantrolene-2After crisis controlled, give dantrolene

1mg/kg every 4-6 hours for 24 hoursContinue dantrolene for 36 hoursRecrudescence rate is 25%

Management of Malignant Hyperthermia

Biochemical MarkersBlood gasses – esp pCO2, pH, CKMyoglobinuriaPT, PTT, INR, fibrin split productsLiver enzymes, BUN

Morbidity and Mortality

RHABDOMYOLYSIS

RENAL FAILURE

DIC if temp >41.50 C

Hyperkalemia

Acidosis

Prevention of Malignant Hyperthermia

Preop personal/family history of anesthetic problems, neuromuscular disorders

Temperature/endtidal CO2 monitoring during general anesthesia

Recognition of masseter rigidity Investigation of unexplained tachycardia,

hypercarbia, hyperthermia Availability of Dantrolene Avoiding MH triggers in MH susceptibles Using Succinylcholine in indication

Principles of Management of

MH SusceptibleDantrolene not necessary

preoperatively (dantrolene available)Avoid succinylcholineAvoid potent inhalation agentsDischarge after about 2 hours in the

recovery room if all signs are stable

Preparation for MH Susceptible

Shut/disable vaporizersFlow 02 @ 10L/min for 20 minutes

(through machine and ventilator)Change carbon dioxide absorbentUse non-trigger agents or local

anesthesiaMonitor temperatureHave dantrolene available

Suggested Regimen for MH Patient

Anxiolytic (ketamine permissible)Propofol/opioid inductionNon-depolarizing relaxantNitrous/narcotic/propofolReversal of muscle relaxantObserve 4 hours

Drug Safety in MH

MH Trigger AgentsPotent Volatile Anesthetics (eg.

halothane, sevoflurane, desflurane)Succinylcholine

Not MH TriggersIntravenous agentsOpioidsNon-depolarizing agentsKetaminePropofolAnxiolytics

Credits

http://www.mhaus.org/index.cfm/fuseaction/Content.Display/PagePK/ProfessionalInfoCenter.cfm, Website of MHAUS, Malignant Hyperthermia Association of the United States, Professional Information Center.