Malignant Hyperthermia Flashcards
MH is transmitted by
Autosomal Dominance
Where is the genetic defect located chromosomally
Long arm of chromosome 19
Where is the defect associated with MH
Ryanodine receptors
Ry1 (skeletal) only
True/False
Triggering of MH may not occur with a SINGLE anesthetic exposure
True- may trigger after several exposures
True/False
MH is a malignancy
False
True/False
MH causes hyperthermia
False
What is MH
A fulminant HYPERMETABOLIC state of skeletal muscle induced by VOLATILE inhalational anesthetics, succinylcholine, and perhaps by stress/excercise
** What is the MOA of MH
Release of substantial amounts of calcium into sarcoplasm caused by defective Ryd1 receptors, with reversal of usual gradients into the SR, mitochondria, and/or sarcolemma into extracellular fluid.
As a result, calcium pump requires excessive amounts of ATP leading to heat, acid, and C02 production which alters the energy supply and demand and causes cell breakdown, release of intracellular contents, and ischemia
How does Dantrolene stop MH
by stopping the loss of calcium from SR, but not interfering with calcium uptake. This allows the calcium pumps to catch-up with calcium demands
Name the triggering agents for MH
All halogenated agents including: Methoxyflurane, Cyclopropane, ether, and the rest
Succinylcholine
Decamethonium
List the Main clinical presentations of MH
SNS stimulation secondary to hypermetabolism TACHYCARDIA MASSETER MUSCLE RIGIDITY and generalized muscle rigidity HYPERCAPNIA INCREASED TEMP (1-2 degrees/5 min) hyperKalemia hyperCacemia myoglobinuria CPK > 20K Lactidemia r/t hypermetabolism Ventricular dysrhythmias
MMR occurs more commonly in
children
young adults
Most MMR occurs after which inhalation/muscle blockers
Halothane, Sevoflurane following succs administration
Will repeat doses of succs or NDMR relieve MMR
NO
What will the peripheral nerve stimulator reveal with MMR
flaccid paralysis
List the differential diagnosis for MMR
Myotonic syndrome TMJ dysfunction Underdosing with succs Not allow succs to work Increased resting tone after succ with fever or elevated epi levels
MH
List management strategies with MMR
DC anesthesia and postpone case if possible
continue anesthesia with non-triggering agent
give dantrolene, only if generalized rigidity/hypermetabolism noted
admit for 12-24 hours after episode
serial CKs, at 6,12,24 hours
* contracture test- only definitive diagnosis
Identify other dx’s associated with MH
King-denborough syndrome Duchenne muscular dystrophy Becker dystrophy Myopathies Myotonias Periodic paralysis Osteogenesis imperfecta
List syndromes with clinical resemblances to MH
Pheochromocytoma Thyrotoxicosis Sepis Hypoxic encephalopathy Mitochondrial myopathies NMS Serotonin Syndrome
Differences between pheochromocytoma and MH
Highest BP/ Tachy with pheo
No rigidity with pheo
CO2 less with pheo
Differences between Thyrotoxicosis and MH
Second highest BP ever seen/Tachy
CO2 less with thyrotox
Hypoxic encephalopathy and MH
Patient doesnt wake up, posturing, stiff neck with HE
NMS and MH
In NMS, symptoms occur in severly ill patients treated with antipyschotics, or dopamine antagonists with symptoms resembling MH such as: muscle rigidity, and hyperpyrexia
NMS:
- Severe muscle rigidity
- Slow onset (1-3 days)
Treatment of NMS include
temperature, acid-base, fluid status
Benzo, Bromocriptine (dopamine agonist), Dantrolene
Serotonin Syndrome
Occurs within hours vs. MH which occurs within minutes, Hypercapnia within minutes
Differential Diagnosis r/t ETCO2 > 5mmHg above steady state
**Increased CO2 production is most sensitive and specific for MH
r/o fever, light anesthesia
Decreased ventilation- r/o spont. breathing, ventilator issues, breathing circuit, pulmonary issues, extrathoracic issues
Monitoring error-r/o technical problems
Differential Diagnosis r/t Tachycardia and Fever
Too much covers or ambient temp
equipment problems
Increased heat production-r/o infection,pheo, etc
CNS-r/o hypothalamus injury, serotonin, prostaglandin
Drug reactions-r/o NMS, MAOI, cocaine, TCA,ketamine, etc.
List treatment measures for MH
STOP triggering agent-start propofol infusion Hyperventilate with 100% oxygen Administer Dantrolene Initiate cooling measures Correct dysrhythmias Correct hyperKalemia Secure monitoring lines Maintain urine output Follow postop Call MHAUS
Dantrolene administration
IV STAT- 2.5 mg/kg with repeated doses until MH reversed. Dose can be as high as 10mg/kg, but should be less than 30 mg/kg
Metabolic acidosis correction
Correct metabolic acidosis with Sodium Bicarbonate per ABGs (1-2 mEq/kg)
Cooling measures
IV iced SALINE SOLUTION with 15 cc/kg/10 minutes for 30 minutes
Surface cooling with ice, hypothermia blanket
Lavage: stomach, bladder, rectum, peritoneal, thoracic cavities with NS
*Stop cooling when temp < or equal to 38 C
Dysrhythmias correction
Correct hyperKalemia and acidosis
Don’t give CCB- will cause hyperKalemia or cardiac arrest in presence of dantrolene
HyperKalemia correction
Hyperventilation Bicarbonate Glucose/Insulin- 10 Units with D50 50 mL Check glucose levels hourly Frequent ABGs
Monitoring lines
CORE temp
Foley catheter
art-line
Urine output
at least 2cc/kg/hr
give mannitol 1.25 gm/kg IV and Lasix 1 mg/kg up to 4 doses
Post incident monitoring and therapy
until episodes subsides
put in ICU at least 24 hours
PO dantrolene 1 mg/kg q 4-6 hours or 0.25 mg/kg/hr IV
*titrate to muscle rigidity, tachycardia, and acidosis
For MH susceptible patients
Choose regional anesthetic prep anesthesia machine-remove vaporizers, change CO2 absorbent, 02 flow in circuit for 20 min at 10LPM Get preop CBC/CPK Cooling Blankets on OR table art-line/CVP
*Preop admin of dantrolene not recommended
Dantrolene is classified as a
skeletal muscle relaxant
Dantrolene works by
inhibiting the release of calcium from SR
Dantrolene is caustic to
tissues- prevent extravasation
Caution patients of —–, —-, —- after dantrolene administration
decreased muscle strength (ambulation), light headness, and swallowing difficulties
What two drugs displace Dantrolene from plasma proteins, and thus increases risk for toxicity
Warfarin
Clofibrate
What drug increases plasma binding of Dantrolene, and thus decreases bioavailability
Tolbutamide
List the AE of dantrolene
Pulmonary edema r/t mannitol
Thrombophlebitis r/t extravasation
Urticaria/Erythema
Hepatitis, seizure, pleural effusion, pericarditis with long term exposure
How is dantrolend prepared
dilute each vial with 60 cc Sterile water without BACTERIOSTATIC agent
gently shake until clear
Each vial contains 20 mg Dantrolene, 3 g Mannitol, and Sodium hydroxide
pH is 9.5
Once mixed, must be used within 6 hours
what is a contracture test
A muscle biopsy is carried out at an approved research center, under local anesthesia. The fresh biopsy is bathed in solutions containing caffeine or halothane and observed for contraction; under good conditions
what is the sensitivity for the contracture test
100%- identifies those with dx
what is the specificity for the contracture test
78%- identifies who doesn’t have dx
List the four basis for litigation r/t MH
failure to obtain a thorough personal hx
failure to monitor temperature
failure to have adequae supplies of dantrolene
failure to investigate increase in temp, skeletal muscle tone when assoc. with incr. HR and dysrhythmias
What should you ask every patient preop r/t MH
“Have you or any family members ever had problems with anesthesia such as fever, or death”
