1. 0-6hrs - direct corrosion GIT-diarrhea, vomiting, fluid losses, 2. 6-12hrs absorption of iron and less symptoms, 3. 12-48hrs - RAGMA, vasodilation, 3rd space losses, hepatorenal failure 4. 2-5days Acute hepatic failure, coagulopathy, hypoglycaemia - death, 5. 2-6 weeks - cirrhosis, GI strictures
How else (and more sensibly) can it be through of?
direct GI corrosive effects and systemic effects
What is the dose expected to cause systemic effects?
Elemental iron 60mg/kg. 20-60mg/kg is likely to cause just GI symptoms
What tests should you do in suspected iron toxicity?
BSL, para, ECG, ABG - May have mixed metabolic RAGMA - Fe, NAGMA (diarrhoea) and alK as vomiting), lactate (B2 cause), AXR (to quantify amount), Serum iron level at 4-6hours -peak absorption - 500mcg/dL suggests systemic tox, falling venous bicarb can be used as a substitute if no iron levels available
4-6hr serum iron level that predicts systemic fox
500mcg/dL or 90micromol/L
What is the treatment for Fe toxicity?
Fluids and electrolyte replacement, desferroxamine iv until stable and serum levels reduced to 350mcg/dL
What are the indications for desferroxamine?
>60mg/kg elemental iron, peak iron serum level >500mcg/dL, signs or symptoms of systemic fox - metabolic acidosis, altered mental state, shock and chronic iron overload
What are endpoints to cease rx?
patient stability and serum iron <350mcg/dL. Avoid infusions >24hrs because or risk ARDS
How should desferoxamine be given?
full cardiac monitoring, 500mg in 100mls saline, 15mg/kg/hr increased to 40 if severe and reduced if hypotensive. usually takes
Complications of desferroxamine
hypotension esp at high dose, Toxic retinopathy, Hypersenstivity reaction, ARDS >24hrs, yersinia infections and other secondary infections
Local anaesthetics, nitrates, nitrites, dapsone, sulfa and rifampicin. Recreational amyl nitrate - inhaled (poppers), sometimes mixed with cocaine or MDMA
What level of metHb is normal?
physiologic levels of MetHb usually around 1-2%, mild 15-30%, mod 30-50%, severe life threatening 50-70%
population at risk?
What effect does methhaemoglobinaemia have on Oxy/diss curve?
Shift to left - unable to release O2. methhaemoglobiaema unable to carry O2
Symptoms and signs of methaemaglobinameia?
grey blue skin, chocolate brown blood - DOES NOT CHANGE ON EXPOSURE TO AIR, pulse ox 85% (falsely high) due to similar wavelengths of oxyhaem and methaem, SaO2 on blood gas also falsely high a this is measuring partial pressure dissolved O2 in blood as well as that carried (or in this case not carried) by blood. This difference is known as being an increased oxygen saturation gap
What is needed to accurately measure SpO2?
co-oximetry - can differentiate between, oxy-, deoxy-, carboxyl- and meathhaemaglobin
What is the treatment for methaemoglobinaemia?
Methylene blue if metHb > 30%. Dose 1-2mg/kg iv over 5mins. Some thoughts on using NAC (no proven effect) Hyperbaric O2, exchange transfusion
>200mg/kg over 24h; OR >150mg/kg or 6g per 24h over 48hrs if asymptomatic; OR >100mg/kg or 4g per 24h if symptoms of liver toxicity
what is a massive overdose
>50g or 1mg/kg (whichever is less) OR serum para more than double nomogram; OR hepatotoxicity; or iv para errors
activated charcoal immediate release para
50 g activated charcoal should be administered to a cooperative, awake adult within 2 hours of ingestion of a toxic dose of immediate-release paracetamol AND up to 4hrs for massive OD.
modified release para
within 4 hours of modified-release paracetamol ingestion; >4h for massive OD
early discharge for healthy kids under 6
charcoal never indicated. Level 2h post ingestion < 150 mg/L, NAC not required, early d/c. Level 2h > 150 mg/L, repeat at 4h, start NAC if > 150 mg/L.
Rx within 2h single ingestion
activated charcoal, and measure serum para at 4h
Rx within 2-8 of single ingestion
consider charcoal, measure serum para within 4-8h and plot on nomogram, if over line start NAC, if under line no more treatment
Rx >8h post single ingestion
start NAC, mesaure serum para and ALT, if para below nomogram and ALT <50 then cease NAC, otherwise continue infusion
Rx staggered ingestion
timing of presentation is from the first dose, ie if first dose >8h start NAC
repeated supratherapeutic ingestions
treat with NAC if ALT >50 and serum para > 20. Repeat blds at 8h after first set and stop NAC if ALT<50 or not rising and para level <10 otherwise continue.
Reactions to NAC
rash, wheeze, mild hypotension occur in 10%–50% of patients during the first two infusions. Rx supportive, slow or pause infusion, antihistamines, bronchodilators prn. Recommence when symptoms settle.
Dose of NAC
total 300mg/kg over 21hrs. Continued at rate of last bag until safe to stop ie 100mg/kg over 16hrs.
towards end of infusion para level should be <10, and ALT < 50 and decreasing, INR <2
Kings college criteria (predicts fulminant hepatic failure needing liver Tx)
INR >3.0 at 48 hours or >4.5 at any time; oliguria or creatinine >200 μmol/L; persistent acidosis (pH < 7.3) or arterial lactate >3 mmol/L; systolic hypotension BP < 80 mmHg, despite resuscitation; hypoglycaemia; severe thrombocytopenia; encephalopathy of any degree, or GCS <15 not associated with co-ingestion of sedatives.