1. Malignant Hyperthermia

2. 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

3. Malignant Hyperthermia
The ‘malignant’ part of the name MH has proved useful in emphasizing the potentially fatal nature of the reaction

4. 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

5. Malignant Hyperthermia
It is a true EMERGENCY in the Operating Room.

6. 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: in pediatric patients& 1:
Usually occurs between the ages of 2 and 42.

7. Malignant Hyperthermia
Triggers:
Drugs
Sevoflurane
Methoxyflurane
Desflurane
Succinylcholine
Isoflurane
Halothane
Enflurane

8. 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

9. Malignant Hyperthermia
Signs of Malignant Hyperthermia
Specific
Muscle Rigidity
Increased CO2 Production
Rhabdomyolysis
Marked Temperature Elevation
Non Specific
Tachycardia
Tachypnea
Acidosis (Resp/Metabolic)
Hyperkalemia
Some signs of MH may be more specific to the diagnosis than others. Specific signs are muscle rigidity , increased carbon dioxide production, rhabdomyolysis and marked temperature elevation. Less specific signs include tachycardia , tachypnea, acidosis and hyperkalemia. In most cases patients developing MH will demonstrate metabolic acidosis.

10. 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.

11. Malignant Hyperthermia
Causes Cont’d:
This calcium release results in sustained muscle contraction and an abnormal increase in energy utilization and heat production.

12. 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.

13. 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.

14. 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 non-depolarizing neuromuscular blockers as needed)

15. 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

16. 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

17. 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

18. 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 mg/kg once

19. 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

20. 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

21. 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

22. Prevention of Malignant Hyperthermia
Investigation of unexplained tachycardia, hypercarbia, hyperthermia
Availability of Dantrolene
Avoiding MH triggers in MH susceptibles
Using Succinylcholine in indication

23. A 28-year-old man presents for shoulder surgery
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?
Vecuronium
Rocuronium
Pancuronium
Succinylcholine

24. All BUT ONE of the following are true regarding malignant hyperthermia (MH). Indicate the exception:
Newer volatile anesthetics such as desflurane are not believed to trigger MH
Nitrous oxide is safe
Dantrolene is the only therapeutic drug treatment
Mortality is as high as 10% even with prompt treatment
Which of the following is the first sign of a malignant hyperthemic reaction?
Hyperthermia
Hypercarbia
Tachycardia
Ventricular arrhythmias

25. Treatment of a malignant hyperthermia crisis includes ALL BUT ONE of the following. Indicate the exception:
Turning off the volatile anesthetic
Active cooling measures
Dantrolene
Beta blockers

26. Thank You