Mod 10b: pharmacogenetic disorders

Question 1

What is malignant hyperthermia and what triggers it

Answer 1

Inherited disorder of calcium receptor on sarcoplasmic reticulum which leads to hypermetabolic state-> runaway cellular metabolism

Triggered by: all volatiles, suxamethonium especially

Question 2

How does MH present?

Answer 2

Early:
- hypercapnia, increased O2 extraction, tachypnea

Later:
- Cyanosis, muscle rigidity, hyperthermia(LATE SIGN)

Question 3

What are the consequences of MH?

Answer 3

Renal and hepatic failure, coagulopathy, cerebral oedema, death

Question 4

How do you manage MH?

Answer 4

Discontinue trigger
Call for help
Hyperventilate 100% O2
Dantrolene: 2.5mg/kg initial bolus
Cool patient and supportive management

In ICU:
- Dantrolene infusion, dialysis, supportive care

Question 5

What is scoline apnoea and how does it present?

Answer 5

Abnormal/absent pseudocholinesterase enzyme

Presents as prolonged paralysis after one dose

Question 6

How do you manage scoline apnoea?

Answer 6

ventilate
sedate
Fresh frozen plasma
Medical alert bracelet

Question 7

What is porphyria, and how does it present?

Answer 7

Defect in synthesis of haem:
- porhyrin accumulation

Presents as:
- abdo pain + vomiting
- motor and sensory neuropathy
- Autonomic dysfunction
- Seizures, coma and death

Question 8

What precipitates porhyrias

Answer 8

Barbituates(thiopentone)

Pain, infection, starvation

Question 9

What drugs are safe to use in porphyrias

Answer 9

propofol for induction
NO2
Isuflurane
Most volatiles
Suxamethonium
Atracurium
Morphine

Question 10

What is halothane hepatitis?

Answer 10

Immune mediated Type 2 hypersensitivity reaction and spectrum includes fulminant hepatic failure