Porphyria

Question 1

What is porphyria

Answer 1

Autosomal inherited group of disorders that are the result of various defects in haem synthesis.

Classification:

1. Inducible forms
   - Acute intermittent porphyria
2. Non-inducible forms

Question 2

How does acute intermittent porphyria manifest clinically

Answer 2

Neurological

1. Anxiety
2. Confusion
3. Autonomic instability (HPT/tachycardia)

GIT

1. Emesis
2. Severe abdominal pain

Question 3

What can precipitate acute attacks of acute intermittent porphyria

Answer 3

Stress / fasting / dehydration / sepsis

Medications (many used in the perioperative period)

Question 4

Which commonly used perioperative agents are safe in acute intermittent porphyria and which are unsafe

Answer 4

SAFE

1. Midazolam
2. Cefazolin / Gentamicin / Co-amoxiclav
3. Lidocaine
4. Opioids (fentanyl and morphine)
5. Propofol
6. Succinylcholine
7. Volatiles
8. Non-depolarising muscle relaxants
9. Paracetamol
10. Dexamethasone
11. Neostigmine
12. Glycopyrrolate
13. Ondansetron / Granisetron
14. Bupivacaine

UNSAFE

1. Thiopental
2. Etomidate
3. Ketamine
4. NSAIDS (diclofenac)
5. Alcohol

Question 5

What is acute intermittent porphyria

Answer 5

Inherited metabolic disorder caused by deficiency of porphobilinogen deaminase (enzyme found in the synthetic pathway of haem). Acute attack is likely fatal. Precipitants: stress, dehydration, infection, fasting, drugs.