Malignant hyperthermia - Warszawski Uniwersytet Medyczny

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Malignant hyperthermia
- A rare complication of anaesthesia
What is it?
“It is a biochemical chain reaction response triggered by commonly used
general anesthetics and the paralyzing agent succinylcholine, within the
skeletal muscles of susceptible individuals” –MHAUS.org
Has autosomal dominant inheritance
Incidence of 1-5 : 100,000, < 5% mortality rate
Triggered by anesthetic drugs such as all inhalation agents (except NO)
and succinylcholine (depolarising muscle relaxant)
Uncontrolled increase in intracellular Ca2 because of anomaly of
ryanodine receptor which regulates Ca channels in sarcoplasmic reticulum
of skeletal muscle
Clinical picture
It's onset can be immediate or hours after agent is administered
There will be increase in:
- Oxygen consumption
- ETco2 on capnograph
- Tachycardia/dysrythmia
- Tachypnia/cyanosis
- Diaphoresis
- Hypertension
- Temperature
Muscular symptoms
- Trismus (occurs in 1% of children given SCh
together with halothane)
- Tender and swollen muscles due to
rhabdomyolysis
- Trunk or total body rigidity
Pathophysiology
Alteration in the Ca induced ca release via the ryanodine receptor channel (RYR1) or!
impairment in the ability of the sarcoplasmic reticulum to sequester calcium via the ca
transporter
After trigger agent is administered, there is a sudden and prolonged release of ca which
causes
- Massive muscle contraction
- Lactic acid production
- Increased body temperature
Dantrolene stops the calcium released by binding to the ryanodine receptor and blocking the
opening of the channel therefore stopping the release of calcium. It has little effect on heart
and smooth muscles as the ryanodine receptors differ in these tissues (RYR2).
Triggering vs safe
anaesthetics
Triggering agents
Non-triggering agents
Volatile gaseous inhalation anesthetics:
Propofol
Ketamine
Nitrous oxide
All local anesthetics
All narcotics
Non depolarizing muscle relaxants:
Isoflurane
Sevoflurane
Desoflurane
Haloflurane
Enflurane
Methoxyflurane
•Vecuronium
•Succinylcholine
•Rocuronium
Suxamethonium
decamethonium
•pancuronium
Complications
Coma
DIC
Rhabdomyolysis
Myoglobinuric renal failure/hepatic dysfunction
Electrolyte abnormalities (hyperkalemia) and secondary arrhythmias
ARDS
Pulmonary edema
Can be fatal if untreated
Prevention
Check family history
Avoid trigger medication, use regional anaesthesia if possible
and use clean equipment
Central body temperature and ETco2 monitoring
Used to use dantrolene as prophylaxis but not commonly
used anymore
Management
Based on MHAUS guidelines from 2008
1.
Notify surgeon, discontinue agents, hyperventilate with 100% Oxygen at >10l/min, halt
procedure if possible
2.
Dantrolene 2.5mg/kg IV every 5 min (1mg/kg/dose, max dose = 10 mg/kg)
- Repeat until control is obtained
3.
Bicarbonate 1-2 mEq/kg if blood gas values are not available for metabolic acidosis
4.
Cool patient with core temp >39C
- Lavage open body cavities, stomach, bladder, rectum, apply ice to surface, imfuse cold
saline IV
- Stop cooling if temp reaches 38C
1.
Treat acidosis and hyperkalemia
- Don't use Ca2 channel blockers as they may cause hyperkalemia and cardiac arrest with
dantrolene
2.
Hyperkalemia
- Hyperventilation, bicarbonate, glucose/insulin, calcium
- Bicarbonate 1-2 mEq/kg IV, Calcium chloride 10 mg/kg or calcium gluconate 10-50 mg/kg
for life threatening hyperkalemia and check glucose levels hourly
3.
Observe ETco2, electrolytes, blood gases, creatine kinase, core temp, urine output/color,
coagulation studies
- If CK and/or K rises more than transiently or urine output falls to less than 0.5 ml/kg/h
induce diuresis to >1 ml/kg/h urine to avoid myoglobinuric renal failure
4.
Maintain anaesthesia with benzodiazepines, opioids and propofol
5.
Transfer to ICU
Quick recap of
management
1.
Call for help (let surgeon know)
2.
Turn off potential triggering agents
3.
Administer dantrolene 2.5 mg/kg every five minutes
4.
Cool patient to 38C
5.
Monitor and correct blood gases, electrolytes and glucose
Sources:
Wikipedia.com
Toronto notes 2012
Uni-ulm.de (Malignant hyperthermia, Muscle &
Nerve, January 2000)

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