Poisoning in MRCP(IV)- Methanol/ ethylene glycol
As I told you many months ago, there are many causes of metabolic acidosis you have to remember if you plan to sit for your MRCP.
When I was a medical student, my lecturer told me that when a young patient comes to hospital with shortness of breath ( air hunger) and you do an ABG showing metabolic acidosis, you must always consider 3 important diagnosis- 1) Diabetic ketoacidosis , 2) salicylates oberdose ,3 ) Ethanol/ ethylene glycol poisoning.
OK, although methanol is a component of shellacs, varnishes, paint removers and copy machine fluid, it is not uncommon to find it in some alcohol drinks produced illegally. For ethylene glycol, it is used commonly as coolant and preservative and also found in polishes and detergens.
A few important facts to remember for your MRCP Part 1 and 2,
1) Methanol can cause retina injury leading to blindness ( eye manifestations can happen as early as 15-20 hours post ingestion)
2) Ethylene glycol poisoning usually has 3 distinct clinical phases- first stage- CNS effects ( first 12 hours), second stage- cardiopulmonary effects ( CCF, ARDS etc) and third stage- renal effects- ARF.
3) Acute management include gastric lavage and correct the metabolic acidosis. Remember also that haemodialysis can be employed to fasten removal of the toxic metabolites.
4) Folinic acid can be used to protect against ocular toxicity of methanol whereas thiamine are administered to drive metabolism of ethlylene glycol to non-toxic metabolism.
Let me illustrate to you a MRCP question,
A 23-year gentleman is admitted to the A+E due to nausea and vomitting. On examination, he is dehydrated with GCS=14/15. Blood pressure on arrival= 90/60. Blood investigations sent in A+E reviews the following,
Salicylates level= normal
Na=134
K=5.1
BU=10
Creatinine= 100
ABG ( on 2L oxygen supplement)
PH=7.20
HCO3=12
PaO2=100 mmHg
PaCo2=21 mmHg
What further test you would like to order?
A) Random blood sugar B) CXR C) CT brain D) AXR E) Blood lithium level
So, do you know the answer??
