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Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor
The beta blocker toxicity depends on the protein binding, lipid solubility, Na channel blockade , partial agonist, receptor selectivity of the drug.
Primary organ affected in beta blocker toxicity is CVS and hallmark is bradycardia with hypotension.
Lipid soluble , drugs like propranolol can cross BBB and produce mental status depression, seizures, coma.
Cardioselective drugs have less side effect, whereas non selective drugs can cause bronchospasm.
Drugs like labetalol which has both α & β blocking effect can lead to exaggerated hypotension.
Drugs with partial agonist activity leads to hypotension and tachycardia initially.
Beta blockers with Na channel blockade leads to wide complex bradycardia.
Sotalol is unique drug with ability to block K+ channel , this leads to prolongation of QT interval and leads to VT, VF ,VPC, Torsades depointes.
Clinical Feature
Cardiac
Hypotension
Bradycardia
Conduction delays & blocks
Ventricular dysarrythmia
Asystole
Decreased contractility
CNS
Depressed mental status
Coma
Psychosis
Seizures
Pulmonary
Bronchospasm
Commonly Used Beta Blockers & Their Profile | |||||
Drug | Adrenergic receptor Antagonism | Partial Agonism | Lipophilic | Protein Binding | Sodium Channel Blockade |
Atenolol | Beta 1 | - | Weak | 6 -16 | - |
Bisoprolol | Beta 1 | - | Moderate | 30 -40 | - |
Carvediolol | Alpha 1, Beta 1&2 | - | High | >95 | +/- |
Labetalol | Alpha 1, Beta 1&2 | +/- | Weak | 50 | +/- |
Metoprolol | Beta 1 | - | Moderate | 12 | +/- |
Propranolol | Beta 1,2 | - | High | >90 | +/- |
Sotalol | Beta 1,2 | - | Weak | Minimal | - |
Diagnosis
ECG
RFT, ABG, B. Glucose
SpO2
BP Monitoring
Management
GI Deontamination
Activated charcoal may be of benefit if it is given within 1-2 hrs.
Whole bowel irrigation may be beneficial.
Glucagon
First line agent in acute beat blocker toxicity .
Glucagon produced in pancreatic alpha cells from proglucagon.
It is thought to activate myocardial adenyl cyclase independent of the beta receptor.
Effect is seen within 1-2 min , reach a peak in 5-7 min & have a duration of action of 10-15 min.
Bolus dose of glucagon is 0.05- .15mg/kg
Continous infusion: 1-10mg/h
Adrenergic Receptor Agonist
Adrenaline, Noradrenaline, Dopamine, Isoproterenol are used routinely.
Noradrenaline is most effective due to its ability to increase heart rate and Blood pressure.
Hyperinsulinemia Euglycemia therapy
Insulin facilitates myocardial utilization of glucose the desired substance during stress.
Dose : 1U/kg IV bolus followed by 0.5-1.0 U/kg /h
0.5 gm/kg boluse glucose , followed by infusion.
Blood glucose to be monitored every 20 to 30min until euglycemia is achieved later every hrly.
Adverse effect : Hypoglycemia, hypokalemia
Normally the heart uses free fatty acids as its primary energy source but during stress it switches to using carbohydrate to maintain metabolism
Calcium
They improve depression of myocardium via positive inotropic action.
Adverse effect : Hypercalcemia, conduction blocks, worsening bradycardia
Recommended dose : 0.6ml/kg given over 5-10min followed by continuous infusion 0.6-1.5ml/kg/h.
Sodium Bicarbonate
To treat severe metabolic acidosis & wide QRS dysarrythmia secondary to Na + channel blockade.
Rapid bolus 2-3 mEql/kg.
Phosphodiesterase inhibitor
It can be used as an alternate to glucagon .
They prevent break down of cyclical adenosine monophosphate thereby maintaing intracellular calcium.
Milrinone dose : 0.5mcg/kg/min
Sotalol toxicity
Magnesium sulphate & Lidocaine are used to treat sotalol toxicity.
End Point of Treatment
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Updated on 2/2/2015
Reference : Tintinalli
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emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor