What differentiates beta blocker and calcium channel blocker overdoses?
What drug overdoses/toxic exposures will likely present with significant bradycardia?
Beta blockers
CCB’s
Digoxin
Amiodarone
Clonidine
Organophosphates
GHB
What are the features of Acute digoxin toxicity?
Ingestion >10mg or 30mcg/kg have severe toxicity
- Get CVS (brady/tachy arrhythmias, arrest), GI (abdo pain, upset) and CNS (confusion, coma) effects
- Hyperkalaemia is a sign of serious toxicity, still treated with
-Serum levels not accurate within 6hrs of ingestion
- Acute serum levels >15nmols/L associated with severe toxicity
Specific Arrhythmias
- Bidirectional VT
- AFluttter with high grade AV block
- AFib with high grade block/regularised AF
- Slow AF + junctional tachycardia (less specific)
- Down sloping ST segment (reverse tick, salvador dali sign)
A top differential for tox ingestion with K+ > than expected for acidosis
Who is at risk of chronic digoxin toxicity?
What are the features of chronic digoxin toxicity?
Same indications for digibind as acute with same dosing, except lower serum digoxin level + symptoms needed (>2nmol/L)
How does arrest management change in acute digoxin toxicity?
How does salicylate toxicity usually present?
GI
- abdo pain, N/V, haemorrhagic gastritis
CNS
- delerium, agitiations, tinnitus, seizures, coma
Metabolic
-primary resp alkalosis followed by metabolic acidosis
- Hypoglycaemia (relative or absolute), often need to aim for higher BSL as brain levels lower
- Hyperthermia
100-300mg/kg = GI, tinnitus
300-500mg/kg = HAGMA, multi organ failure
>500mg/kg = cerebral oedema, death
What are the typical salicylates in Australia?
Aspirin
Methyl salicylate (1:1.5)
Choline salicylate (1:0.75)
1ml oil of wintergreen = 1400mg Aspirin
What are the effects of TCA overdose at different doses?
5-10mg/kg (mild)
- tachy, confused, agitated
10-20mg (moderate)
- significant anticholinergic features, delerium and reduced GCS
> 20mg (severe)
- Seizures, coma, hypotension, arrhytmias, death
Acidosis worsens TCA overdose due to alpha receptor antagonism (worsens hypotension) and greater Na+ channel blockade (worsens arrhytmias/ECG)
What are the ECG changes in TCA overdose?
R wave in AVR >3mm or >0.7 amplitude of S wave (most specific)
Sinus tach
QRS and QT prolongation
QRS >110msec increased risk of seizures
QRS >160msec increased risk of VT/VF
What is the treatment and end points for TCA/Na+ blocker overdose?
Sodium bicarbonate
1-2mls/kg bolus with Q5min repeat
Indicated for seizures, arrhythmias, QRS >120msec and peri-intubation to prevent/treat CVS collapse
End point is reversal of above and aiming pH 7.50-7.55
Other treatments
Lidocaine 100mg IV for resistant arrhythmias despite pH 7.55
3% saline for resistant cardiac toxicity
What are the risk factors for severe toxicity from BB/CCB overdose?
Big dose
Extremes of age
Pre-existing CVS disease
Co-ingestion with -ve inotropes
What is the toxic dose of Ibuprofen?
> 300mg/kg
Causes multiorgan failure
What is different about Mefenamic acid compared to other NSAID’s in overdose?
Causes seizures
Charcoal contraindicated prior to intubation and NG placement due to imminent risk of seizures
What are the clinical effects seen with Theophylline poisoning?
What are the indications for Charcoal in Aspirin OD?
How does Methotrexate poisoning present and how is it treated?
How does Baclofen overdose typically present?
How is Baclofen overdose treated?
How does cocaine toxicity usually present?
Sympathomimetic and Na+ channel blocker activity (particularly fast Na+ channels)
CNS- paranoid delerium, rigidity, myoclonic jerks, seizures
Cerebral oedema, SAH
CVS- Tachycardia, HTN, prolonged QT and QRS, malignant arrhytmias
Vasospastic AMI, APO, dissection
Other- Rhabdo, hyperthermia, tachypnoea, resp complications
What is the treatment for Cocaine OD?
AVOID B-blockers
- Unopposed Alpha
Hypertension
- Benzos, GTN/SNP
- Consider Phentolamine 1mg IV with repeat if refractory
VT
- Sodibic 50-100mmol + hyperventilation aiming pH 7.50-55
- If refractory give IV Lignocaine
Chest pain
- Aspirin, GTN, Calcium channel blockers
- May need angiography
Seizures
- Benzos and SodiBic
Hyperthermia
- Benzos, cool fluids, may need aggressive cooling techniques
How does Valproate overdose present and what is the risk stratification based on?
Simplified
<200mg/kg- Mild sedation
200-1000mg/kg- dose dependent CNS depression
>1000mg/kg- Coma, multiorgan failure, cerebral oedema
What are the metabolic effects of large valproate overdoses?
HAGMA with lactataemia
Hypoglycaemia
Hyperammonaemia
Hypernatraemia
Hypocalcaemia
Which Beta Blockers and Calcium Channel Blockers are the most toxic?
BB’s
- Sotalol (K+ blocker)
- Propranolol (Na+ blocker)
CCB’s
- Verapamil (SR forumlations readily form a Bezoar, indication for WBI)
- Diltiazem (Potent vasodilator with some -ve inotrope effects)
- Other CCBs cause vasodilation but not significant -ve inotropy, so often get compensatory tachycardia