A two year old boy is suspected of ingesting iron tablets.
a) List three clinical signs of iron poisoning.
b) List two investigations which would support the diagnosis of iron poisoning.
c) Which blood gas (a or b or c) would be most consistent with iron poisoning? Justify your choice of answer.
a |
b |
c |
|
pH |
7.1 |
7.55 |
7.45 |
pCO2 |
34 mmHg (4.5 kPa) |
30 mmHg (4.5 kPa) |
34 mmHg (4.5 kPa) |
pO2 |
75 mmHg (10 kPa) |
90 mmHg (12 kPa) |
70 mmHg (9.3 kPa) |
BE |
-18 mmol/L |
+4 (mmol/L) |
-0.1 mmo/L |
d) List three treatments specific for iron poisoning and their mechanisms of action.
e) List one serious long term complication of iron poisoning.
a) List three clinical signs of iron poisoning.
Clinical sign |
Cause |
Nausea / vomiting/ haematemesis |
Acute gastritis, ischaemia |
Diarrhoea |
|
Abdominal pain |
|
Melaena |
|
Tachypnoea |
Metabolic acidosis |
Coma/ seizures |
|
Shock/ hypotension |
Myocardial depression |
Oliguria |
Capillary leak |
Jaundice / coagulopathy |
Hepatic necrosis |
b) List two investigations which would support the diagnosis of iron poisoning.
Iron Level > 300 microgm/dL, or 63 micromol/L |
|
Abdominal XR: |
Shows iron tablets |
Blood gas |
Metabolic acidosis |
Hyperglycaemia |
|
Coagulopathy |
Interference with coagulation cascade/ |
Deranged liver enzymes |
From hepatic necrosis |
Raised white cell count |
c) Which blood gas (a or b or c) would be most consistent with iron poisoning? Justify your choice of answer.
a |
b |
c |
|
pH |
7.1 |
7.55 |
7.45 |
pCO2 |
34 mmHg (4.5 kPa) |
30 mmHg (4.5 kPa) |
34 mmHg (4.5 kPa) |
pO2 |
75 mmHg (10 kPa) |
90 mmHg (12 kPa) |
70 mmHg (9.3 kPa) |
BE |
-18 mmol/L |
+4 (mmol/L) |
-0.1 mmo/L |
Answer: Metabolic acidosis due to uncoupling of oxidative phosphorylation.
d) List three treatments specific for iron poisoning and their mechanisms of action.
Desferrioxamine |
(Binds intravenous iron to form water soluble |
Whole bowel irrigation |
(Polyethylene glycol: works with minimal |
Exchange transfusion with plasmapheresis. |
|
Surgical/ endoscopic removal of tablets |
(If seen on AXR). |
Treat coagulopathy |
|
Treat hyperglycaemia |
|
Aggressive volume resuscitation (as |
|
Dialysis |
But limited efficacy |
Gastric Lavage with HCO3 |
(Controversial) |
Note: Charcoal is ineffective.
e) List one serious long term complication of iron poisoning.
1. Bowel obstruction (esp gastric outlet)
2. GI strictures
As this question closely resembles Question 8 from the second paper of 2013, I will not elaborate excessively.
a)
Feature | Causes |
Tachypnoea |
|
Shock, circulatory collapse |
|
Hypoglycaemia |
|
Coma |
|
High anion gap metabolic acidosis |
|
Hyperlactatemia |
|
Renal failure |
|
Gastric ulceration |
|
Haemorrhage, melaena |
|
b)
c)
d)
Decontamination
Enhanced elimination
Specific antidote
Supportive care
e)
Toxicity manifests in four stages, where the late Stage IV represents gastrointestinal scarring (4-6 weeks since ingestion) - gastric scarring and pyloric stricture are the specific features.
The Royal Childrens Hospital has a good set of guidelines for irone overdose.
Abhilash, Kundavaram PP, J. Jonathan Arul, and Divya Bala. "Fatal overdose of iron tablets in adults." Indian journal of critical care medicine: peer-reviewed, official publication of Indian Society of Critical Care Medicine 17.5 (2013): 311.
REISSMANN, KURT R., and THOMAS J. COLEMAN. "Acute Intestinal Iron Intoxication II. Metabolic, Respiratory and Circulatory Effects of Absorbed Iron Salts." Blood 10.1 (1955): 46-51.
REISSMANN, KURT R., et al. "Acute Intestinal Iron Intoxication I. Iron Absorption, Serum Iron and Autopsy Findings." Blood 10.1 (1955): 35-45.