MOA/Pharmacokinetics
What receptors do beta blockers work on? (specific)
B1- heart (heart rate, contractility, AV conducttion)
B2- bronchial and peripheral SM/uterus
B3- adipose (lipolysis/thermogenesis)
General signs/symptoms of overdose?
bradycardia, hypotension, AMS, delirium, lethargy, resp depression, bronchospasm, hypothermia, hypoglycemia (esp propranolol)
- most evident before 2 hours but before 6 hours
What labs/tests should be done?
EKG - BC, QRS/QTc prolongation
POCT gluc - hypoglycemia
CXR - acute decomp HF?
BMP- Hyperkalemia
Lactate - elevated in bradycardia > worse outcomes
Digoxin level
When is calcium useful for BB overdose?
undifferentiated bradycardia - might have taken CCB as coingestant
CaCl 1g
CaGluconate 3g q 10min; 9g
Antagonism of B receptors on heart causes what effect?
blunting of the chronotropic and ionotropic response (B1)
EKG manifestations of overdose?
sinus bradycardia, sinus pauses, or sinus arrest
prolonged PR interval or high-grade AV block
Prolonged QRS and QT intervals may occur and severe poisonings may result in asystole
Quick, patient not protecting airway and is bradycardic!
Intubate
Atropine & IVF prior
MOA of insulin in BB toxicity?
increases intropy and contractility
1u/kg bolus followed by 1u/kg/hr with 0.5 g/kg/hr dextrose
monitor gluc every 15-30 min
cardiac function still depressed > inc up to 10u/kg/hr
patients taking nonselective β-adrenergic antagonists typically have increased plasma concentrations of
triglycerides
- altered lipid metabolism, release of FFA inhibited
Manifestations in BB agents with K channel blockade?
Acebutolol and Sotalol
QT with significant lengthening
Risk of Ventricular dysrhythmias highest between 4-20 hours
Recent large ingestion/significant toxic effects we should proceed with ___!
OG lavage - if pills could still be in stomach
- may cause vagal response (can pre-treat w atropine)
- AC with minor effects and water soluble BB
- sustained release > whole bowel irrigation
how long does it take for response to insulin?
15-60 mins
may need to start catecholamine infusion before insulin effects apparent
*monitor K*
β2-Adrenergic antagonists impair the ability to recover from ____ and may mask the sympathetic discharge that serves to warn of ______
hypoglycemia
Manifestations in membrane-stabilizing agents?
Coma, seizures, hypotension, bradycardia, impaired AV conduction, wide QRS, Ventricular tachydysrhythmias
carvedilol, propranolol
Dosing of Atropine in BB overdose?
Increase HR
0.5-1mg every 3-5 min
Max 3mg
treatment consideration if BB lipophilic (propranolol)?
lipid emulsion therapy
1.5mL/kg of 20% bolus over 2-3 min q3-5 min
0.25 mL/kg/min infusion for 30-60 mins
until recovery or max 10ml/kg
Most lipophilic BB?
Most hydrophilic BB?
Lipophilic - propranolol (25% bioavailable) > hepatic elimination
Hydrophilic - atenolol (near 100% bioavailable) > renal
highly lipid soluble - cross membranes and concentrate in adipose tissue/CNS penetration
highly water soluble - distribute in TBW/less CNS toxicity
Isolated β-adrenergic antagonist overdose is most likely to cause symptoms in persons with congestive heart failure, sick sinus syndrome, or impaired AV conduction who rely on _______ to maintain heart rate or cardiac output
sympathetic stimulation
MOA of glucagon in BB overdose?
Increase AC activation > increase HR, inotropy, AVN conduction
3-5 mg IV over 1-2 min, every 5 min (max 10mg)
+ response --> start @response dose per hour
no response -->start @10mg/hr regardless
Which BB indication for ECMO?
NASA
nadalol, acebutolol, sotalol, atenolol
(water soluble renally excreted B antagonists)