Porphyria

OVERVIEW

  • Porphyria = group of disorders where patients have a inability to synthesis Hb resulting in an accumulation of precursors oxidised to porphyrins
  • hepatic and erythropoietic varieties
  • 3 hepatic forms that effect are affected by anaesthesia

(1) AIP – acute intermittent porphyria (Sweden)
(2) VP – variegated porphyria (Afrikaners)
(3) HCP – hereditary coproporphyria (rare – dermal hypersensitivity)

HISTORY

  • Female
  • 30-40 yrs
  • FHx
  • May never have had symptoms
  • Many precipitants — drugs, stress, infection, alcohol, menstruation, pregnancy, starvation, dehydration
  • Abdo pain
  • Vomiting
  • Motor and sensory neuropathy
  • Autonomic dysfunction
  • Cranial nerve palsies
  • Confusion
  • Coma
  • Seizures
  • Fever

EXAMINATION

  • as directed by history

INVESTIGATIONS

  • urinary porphyrins & porphyrin precursors (ALA and PBG)
  • serum porphyrins
  • faecal porphyrins
  • erythrocyte porphyrins
  • DNA testing

MANAGEMENT

Prevention

  • avoidance of precipitants
  • premedication to decrease stress
  • minimize preoperative fasting (IVF)

Anaesthetic precipitants

  • Definite – barbiturates, phenytoin, sulphonamides, ropivacaine
  • Possible – etomidate, lignocaine, chlordiazepoxide, diazepam, halothane, corticosteroids, ketamine, atracurium

Safe drugs

  • Antacids – Na+ citrate
  • Induction – propofol
  • Inhalational agents – N2O, halothane, isoflurane (use with caution)
  • NMBD – sux, pancuronium and vecuronium
  • Reversal – atropine, glycopyrulate, neostigmine
  • Analgesia – opioids
  • LA – bupivacaine
  • Sedatives – midazolam, temazepam, lorazepam
  • Antiemetics – droperidol
  • Cardiovascular drugs – adrenaline, phenylephrine, salbutamol, Mg2+, beta-blockers, phentolamine

MANAGEMENT OF PORPHYRIC CRISIS

Goals:

(1) stop precipitating agent
(2) reverse factors that increase haem production (ALA synthase activity)

Resuscitate

  • Call for help
  • Stop administering precipitent
  • A – may need to be intubated if unresponsive or has uncontrolled agitation/pain
  • B – ventilation may be indicated for progressive weakness -> respiratory failure
  • C – often hypertensive and tachycardic -> beta-blockers (also decreases action of ALA), autonomic instability, invasive monitoring
  • D – midazolam, MgSO4 or propofol for seizure control

Acid-base and Electrolyte abnormalities

  • Hyponatraemia – fluid restriction, hypertonic saline with slow correction
  • Give glucose (20g/hr)

Antidote

  • Haem arginate 3mg/kg IV OD for 4/7
  • Plasmapheresis
  • Opioids for analgesia

Underlying Cause

Avoid precipitants


CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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