Transcript Malignant Hyperthermia

Malignant Hyperthermia
Malignant Hyperthermia
• What is it?
–Malignant hyperthermia (MH) was
the name given to a type of severe
reaction under general anesthesia
that was first described in 1960
Malignant Hyperthermia
–The ‘malignant’ part of the name
MH has proved useful in
emphasizing the potentially fatal
nature of the reaction
Malignant Hyperthermia
– Monitoring during anesthesia at that
time was based on clinical observation
and physical signs, without the luxury
of today’s advanced equipment. The
apparent features of the reactions were,
therefore, dominated by a progressive
pyrexia that usually led to death
Malignant Hyperthermia
–It is a true EMERGENCY in the
Operating Room.
Malignant Hyperthermia
• What is the incidence of developing MH during
surgical operations?
– Over 80 genetic defects have been associated
with MH.
– It is inherited with an autosomal dominant
pattern.
– The incidence is 1: 15000 in pediatric
patients& 1:
– Usually occurs between the ages of 2 and 42.
Malignant Hyperthermia
• Triggers:
–Drugs
• Sevoflurane
• Desflurane
• Isoflurane
• Halothane
• Enflurane
• Methoxyflurane
• Succinylcholine
What are the Clinical
Manifestations of MH?
Original Concepts:
– All patients have muscle rigidity
– High fever, acidosis
– High death rate
Current Concepts:
– Muscle rigidity may or may not be present
– Temperature is a late sign
– End tidal CO2 is an early sign
Malignant Hyperthermia
• Signs of Malignant Hyperthermia
– Specific
• Muscle Rigidity
• Increased CO2 Production
• Rhabdomyolysis
• Marked Temperature Elevation
– Non Specific
• Tachycardia
• Tachypnea
• Acidosis (Resp/Metabolic)
• Hyperkalemia
Malignant Hyperthermia
• What causes an episode of MH?
– MH susceptible persons have a gene
mutation that results in the presence of
abnormal proteins in muscle cells.
– When these persons are exposed to
certain anesthetic agents there is an
abnormal release of calcium inside the
muscle cell.
Malignant Hyperthermia
Causes Cont’d:
– This calcium release results in sustained
muscle contraction and an abnormal
increase in energy utilization and heat
production.
Malignant Hyperthermia
Causes Cont’d:
– This contraction will cause the muscle to
run out of energy and eventually die
releasing a large amount of potassium
into the blood- stream.
– This release of potassium will lead to
heart rhythm abnormalities as well as
lethal rhythms such as V-fib and V- tach.
Malignant Hyperthermia
• Causes Cont’d:
– At the onset of muscle cell death, the
pigment myoglobin is also released and is
potentially toxic to the kidneys.
– If left untreated the patient will experience
cardiac arrest, kidney failure, blood
coagulation problems, internal hemorrhage,
brain injury, and possibly death.
Emergency Treatment for An
Acute MH Event
• Notify surgeon to halt the procedure ASAP:
• Discontinue volatile agents and succinylcholine
– If surgery must be continued maintain general
anesthesia with IV non-triggering anesthetics (e.g.,
IV sedatives, narcotics, amnestics and nondepolarizing neuromuscular blockers as needed)
Emergency Treatment for An
Acute MH Event
• Hyperventilate with 100% oxygen to flush
volatile anesthetics and lower ETCO2
• Give IV dantrolene 2.5 mg/kg rapidly through
large-bore IV, if possible
– Dantrolene is the only specific treatment for MH
– Repeat as frequently as needed until the patient
responds with a decrease in ETCO2, decreased
muscle rigidity, and/or lowered heart rate
– Large doses (>10mg/kg) may be required for
patients with persistent contractures or rigidity
Emergency Treatment for An
Acute MH Event
• Obtain blood gas (venous or arterial) to
determine degree of metabolic acidosis
• Consider administration of sodium bicarbonate,
1-2 mEq/kg dose
• Cool the patient if core temperature is >39°C or
less if rapidly rising
• Stop cooling when the temperature has
decreased to <38°C
Emergency Treatment for An
Acute MH Event
• If hyperkalemia (K > 5.9 or less with ECG
changes) is present, treat with:
– Calcium chloride 10 mg/kg or calcium gluconate 30
mg/kg for life-threatening hyperkalemia
– Sodium bicarbonate 1-2 mEq/kg IV
Emergency Treatment for An
Acute MH Event
– Glucose/insulin: For pediatric patients: 0.1 units
regular insulin/kg IV and 0.5 grams/kg dextrose (%
in formulation not important)
– For adult patients: 10 units regular insulin IV and 50
ml 50% glucose& Check glucose levels hourly
– Furosemide 0.5-1 mg/kg once
Emergency Treatment for An
Acute MH Event
• Institute appropriate monitoring including:
– core temperature, urine output with bladder catheter,
and consider arterial and/or central venous
monitoring
• Follow:
– HR, core temperature, ETCO2, minute ventilation,
blood gases, K+, CK, urine myoglobin and
coagulation studies
Emergency Treatment for An
Acute MH Event
• When stable, transfer to ICU for at least 24
hours
• Key indicators of stability include:
– ETCO2 is declining or normal
– Heart rate is stable or decreasing with no signs of
ominous dysrhythmias
– Hyperthermia is resolving
– If present, generalized muscular rigidity has resolved
Prevention of Malignant
Hyperthermia
• Preoperative personal/family history of
anesthetic problems, neuromuscular disorders
• Temperature/end tidal CO2 monitoring during
general anesthesia
• Recognition of masseter rigidity
Prevention of Malignant
Hyperthermia
• Investigation of unexplained tachycardia,
hypercarbia, hyperthermia
• Availability of Dantrolene
• Avoiding MH triggers in MH susceptibles
• Using Succinylcholine in indication
A 28-year-old man presents for shoulder surgery. The
patient had a documented episode of malignant
hyperthermia in a previous surgery under general
anesthesia
• Which of the following neuromuscular blockers is
contraindicated in this patient?
A.
B.
C.
D.
Vecuronium
Rocuronium
Pancuronium
Succinylcholine
• All BUT ONE of the following are true regarding malignant
hyperthermia (MH). Indicate the exception:
A. Newer volatile anesthetics such as desflurane are not believed to trigger
MH
B. Nitrous oxide is safe
C. Dantrolene is the only therapeutic drug treatment
D. Mortality is as high as 10% even with prompt treatment
• Which of the following is the first sign of a malignant hyperthemic
reaction?
A.
B.
C.
D.
Hyperthermia
Hypercarbia
Tachycardia
Ventricular arrhythmias
• Treatment of a malignant hyperthermia crisis includes ALL BUT
ONE of the following. Indicate the exception:
A.
B.
C.
D.
Turning off the volatile anesthetic
Active cooling measures
Dantrolene
Beta blockers
Thank You