Download Beta-blocker OD fact sheet

Beta-blocker OD
Epidemiology
Toxic dose
Toxic
Mechanism
In paeds
Pharmacology
30-40% asymptomatic, 20% develop severe toxicity
Toxicity doesn’t correlate well with ingested dose; sotalol and propanolol are dangerous, others
are usually OK
High risk: propanolol, sotalol, underlying heart disease, co-ingestion of other cardiac meds, old
Any dose of propanolol or sotalol bad; 1-2 tablets of others OK
Beta 1 = inotrope, chronotrope
Beta 2 = vasoD, bronchoD, glycogenolysis
Selectivity is lost in OD.
Na channel blockade in propanolol (mod in metoprolol, labetalol, pindolol, timolol, carvedilol,
oxyprenolol)  (prolonged QRS, VF, VT, seizures)
K channel blockade in sotalol (prolonged QTc, VT, VF, may delayed onset of Sx)
Half Life
Peak Level
Symptoms
Alpha blockade in labetalol (worsened hypotension)
Partial agonist in pindolol, labetalol (initially incr BP and HR)
Highly lipid soluble in propanolol (mod in metoprolol, oxyprenolol, pindolol)  (worsened CNS
Sx)
Longer: atenolol
1-3hrs
Onset in 1-4hrs (>6hrs if SR); symptoms should become apparent in 80% in 2hrs, 100% in 4hrs
CV: decr BP, decr HR, conduction delays ( VT, VF, asystole)
RS: pul oedema, bronchoS (if CCF, asthma)
hypoG, hyperK
Met:
CNS: altered LOC, seizures (usually brief); esp in propanolol
Investigations
ECG: brady, AV block, wide QRS (esp propanolol; magnitude of QRS widening is predictor of
ventricular arrhythmia), long QTc (esp sotalol), VT, TdP, RBBB. PR prolongation is early sign.
Changes should become apparent in 80% in 2hrs, 100% in 4hrs
Bloods: monitor electrolytes and glucose
Treatment
Propanolol: trt like TCA OD
Bradycardia and hypotension:
IVF: fluid challenge for decr BP
NAD / dopamine / isoprenaline: if ongoing decr BP / brady
Atropine: 10-30mcg/kg
NaHCO3: if conduction abnormality, VT/VF, hypotension despite IVF, wide QRS
Give 1-2mmol/kg over 1-2mins
CaCl / CaGlu: if refractory to other trt
If TdP (eg. Sotalol): MgSO4, lignocaine, overdrive pacing
Decontamination Charcoal: give if <2hrs or after all SR’s
MDAC: if significant sotalol OD
WBI: consider if SR prep
Elimination
Dialysis / Charcoal haemoperfusion: can help in atenolol OD
Antidote
Dextrose / insulin: if propanolol OD with CV compromise; endpoint: until CV toxicity resolved;
aim to maintain normoG, may need KCl; peak effect seen at 1hr; 1iu/kg IV actrapid + 50ml 50%
dextrose  0.5-1iu/kg/hr insulin + 10% dex @ 200ml/hr
Glucagon: incr cAMP; 5-10mg IV bolus (100-150mcg/kg)  2-5mg/hr (10-50mcg/kg/hr) in 5%
dex (only start INF if bolus worked)
Pros: onset 1-2mins, peak 5-7mins, DOA 10-15mins
Cons: no advantage over inotropes; can get tachyphylaxis; has negative inotrope action; difficult
to source enough stocks
Intralipid: consider if life-threatening OD of propanolol; 1 – 1.5ml/kg of 20% IV over 1min  rpt
Q3-5minly 1-2x  0.25-0.5ml/kg/min until CV stable, then can stop.
SE: allergy, pul HTN and acute lung inj
Monitoring
Disposition
Observe 4-6hrs
Admit ICU: if any signs of toxicity