!   7 year old female

!   Ankle fracture repair after MVA

!   Full term normal vaginal delivery

!   Unremarkable past medical history

!   Pre Op

!   VS

!   BP 110/52; P 95; R 16; SpO2 95% on room air; T 36.8*C

!   Oral midazolam

!   Induction

!   Halothane/N2O/O2

!   Peripheral IV placed

!   Easy tracheal intubation

!   Maintenance

!   Halothane/O2 (FiO2: 80%)

!   Spontaneous respirations

!   VS

!   BP 105/45; P 72; R 12; SpO2 98%; T 36.5*C

!   45 minutes into case

!   BP 105/45; P 105; R 12; SpO2 98%; T 36.4*C

!   55 minutes into case

!   BP 120/65; p 130; R 20; SpO2 95%; T 36.5*C

!   60 minutes into case

!   BP 145/90; P 140; R 36; SpO2 96%; T 37*C

!   Rigidity

!   65 minutes into case

!   BP 148/95; P 142; R 45; SpO2 90%; T 38*C

!   Peaked T waves on ECG; mottled skin, sweating

!   70 minutes into case

!   BP 150/105; P 148; R 45; SpO2 85%; T 39*C

!   Frequent runs of ventricular tachycardia

!   73 minutes into case

!   CV arrest

Malignant Hyperthermia

Scott Provost, MD Department of Anesthesia

University of Utah

!   Hypermetabolic state

!   Prerequisites

!   Genetically susceptible

!   Triggering agent

Malignant Hyperthermia

Malignant Hyperthermia

!   Characterized by:

!   ↑ ETCO2 (most sensitive sign)

!   ↑PaCO2

!   Tachycardia (earliest sign)

!   Rigidity (most specific sign)

!   Characterized by

!   Masseter muscle spasm

!   Alterations in blood pressure

!   Arrhythmias

!   Myoglobinuria

!   Mottled skin

!   Characterized by

!   ↑ Temperature

!   May ↑ 1*C / 5 minute

!   May be > 43*C

!   LATE sign

Pathophysiology

!   Normal Muscle Relaxation

!   ATP binds myosin, releasing actin

!   Release of Ca+ from troponin

!   Re-uptake of Ca+ into sarcoplasmic reticulum

!   Malignant Hyperthermia

!   Ryanodine receptor Ryr1 defect

!   Chromosome 19

!   Secondary messengers in release and modulation of Ca+

!   Unopposed Release of Ca+

!   Marked increased/sustained ATP activity

!   Increase in aerobic/anaerobic metabolic activity

!   Increased O2 consumption/ CO2 production

!   Severe lactic acidosis

!   Hyperthermia

!   Unopposed Ca+ Release

!   Muscle membrane breakdown

!   Intracellular potassium release

!   Hyperkalemia

!   Myoglobinemia/Myoglobinuria

!   Sequelae

!   Severe metabolic / respiratory acidosis

!   Renal failure

!   Cardiac arrhythmias

!   Ventricular fibrillation

!   Sudden death

Triggers

!   Succinylcholine

!   Halogenated Volatile Anesthetics

!   Halothane

!   Isoflurane

!   Sevoflurane

!   Desflurane

50% of patients with MH ���have had���

previous uneventful anesthetic with a triggering agent

Risk Factors

!   Family History

!   Duchenne’s Muscular Dystrophy

!   Other muscular disorders

!   Central Core Disease

!   Osteogensis Imperfecta

!   ? heat, stress, infection, trauma, pain

!   Ophthalmic surgery

!   Strabismus, ptosis correction

!   Orthopedic surgery

!   Joint dislocation repair

Onset & Detection

!   Most cases present in OR

!   May present in 1st few hours of PACU or later

!   MH is a constellation of symptoms

!   Most symptoms are non specific

!   Earliest sign may be MMR

Treatment

!   Stop triggering agent immediately

!   Notify surgeon

!   Anesthetic with non-triggering agent

!   100% O2 at high flows

Fulminant MH

!   Dantrolene 2.5mg/kg in sterile H2O IV

!   Up to 10 mg/kg or more

!   Treat hyperkalemia

!   HCO3 1-2mEq/kg IV

!   Follow ABG/Labs for further treatment

!   Hyperventilate patient

!   Cooling measures

!   Ice packs to groin & axilla

!   Cold IV solutions

!   Cold gastric/bladder/peritoneal lavage

!   Discontinue when T = 38*C

!   Dysrhythmias

!   Usually correct with resolution of acidosis, hyperkalemia

!   May require inotropes/ antiarrhythmics

!   No calcium channel blockers

!   Invasive monitoring if available

!   Change anesthetic tubing/ soda lime

!   Mannitol/ Furosemide

!   Monitor labs

!   UOP (1-2 cc/hr)

!   Serum K+/ABG’s/ETCO2/CK

!   Late Sequalae

!   Disseminated Intravascular Coagulopathy

!   Myoglobinuria/ Renal failure

!   Electrolye abnormalities

!   Muscle weakness/ pain

!   Continue dantrolene 1mg/kg q 6h x 24h

!   Suspected / confirmed MH require at least 24 hours of ICU observation

!   Recrudescence of syndrome may occur 24-36 hours after initial onset

!   up to 25% of patients

!   Jaw muscle rigidity after succinylcholine administration

!   Associated with limb flaccidity

!   1/4 patients susceptible to MH

Masseter Muscle Rigidity (MMR)

!   Masseter Muscle Rigidity

!   Discontinue anesthetic & delay surgery if possible

!   If surgery must continue

!   Non-triggering agent, proper monitors

!   Observation at least 12-24 hours

!   Myoglobinuria, signs of MH

!   Follow labs q 6, 12, 24 hours

!   Chemistry, BUN, Creatinine, CK

!   Inform family about MH potential

!   “Jaws of Steel”

!   Stop anesthesia immediately

!   Initiate MH treatment

!   Mild Trismus

!   Continue with proper monitoring

Masseter Muscle Rigidity

Anesthesia for the MH patient

!   Non-depolarizing NMB

!   N2O

!   Total IV Anesthesia (TIVA)

!   Propofol/ Thiopental/Benzodiazapines/ opiates

!   Regional Anesthesia

Safe Anesthetics

!   Flush anesthetic circuit

!   10L O2 flows x 10-20 minutes

!   Change soda lime

!   Change anesthetic tubing

!   Tape over vaporizers

!   Close monitoring

!   ECG/BP/HR/Temp/ETCO2/ABG

!   Dantrolene prophylaxis not indicated

!   Post Op observation x 4 hours

MH Testing/ Diagnosing

Halothane-Caffeine Contracture Test

!   Gold standard test

!   Vastus lateralis biopsy

!   Difficult logistics & expensive

Genetic Testing

!   Available, however not all cases are identified by specific genetic loci

!   Safest Course:

!   If malignant hyperthermia is suspected by personal or family history, avoid triggering agents

Neuroleptic Malignant Syndrome

NMS

!   Associated with use of neuroleptic drugs

!   Shares many features of MH

!   Hypermetabolic state

!   hyperthermia, ANS instability, muscle rigidity, rhabdomyolysis

!   Develops over 24-72 hrs

NMS

!   Pathophysiology

!   Treatment

!   Bromocriptine, +/- dantrolene, supportive

!   Anesthetic implications

!   Some patients may be at risk for MH

!   Dept of Anesthesia and CCM, Hiroshima, Japan 1997

!   William E Hurford. Clinical Anesthesia Proceedures of the Massachusetts General Hospital 6th Edition. Lippincott Williams & Wilkins 2002