Isoproterenol

Aka: Isoproterenol

1. Pathophysiology
   1. Synthetic Sympathomimetic amine
   2. Pure Beta adrenergic agonist
      1. Potent Chronotropic effects
         1. Increases Heart Rate
         2. Potentiates AV conduction
      2. Potent Inotropic effects
         1. Increases cardiac contractility
         2. Markedly increases Cardiac Output
      3. Causes Peripheral vasodilatation
         1. Decreases Diastolic pressure
      4. Causes Bronchodilation
   3. Markedly increases myocardial oxygen demand
      1. May provoke Myocardial Ischemia
      2. May decrease coronary perfusion
2. Pharmacokinetics
   1. Very short half-life (<1.5 minutes)
3. Indications
   1. Other inotropic agents preferred over Isoproterenol
      1. Dobutamine
      2. Amrinone
   2. Hemodynamically significant Bradycardia (pulse present)
      1. Specific Uses
         1. Heart Block
         2. Bradycardia in denervated transplanted heart
      2. Unresponsive to other measures
         1. Atropine
         2. Epinephrine
         3. Transcutaneous pacing or transvenous pacing
         4. Dopamine
4. Contraindication
   1. Ischemic Heart Disease
5. Pediatric Infusion (Same as Epinephrine preparation)
   1. Preparation
      1. Draw up "x" mg of Isoproterenol
      2. Where "x" = 0.6 x Weight in Kilograms
      3. Add enough D5W or NS for 100 ml total
      4. At this dilution:
         1. Infusion rate of 1 ml/h provides 0.1 ug/kg/min
   2. Start Dose: 10 ml/hour (10 ug/kg/min)
   3. Titrate to clinical response, adjusting every 5 min
6. Adult Infusion
   1. Preparation
      1. Dissolve 1 mg Isoproterenol in 250 ml D5W
      2. Final Concentration: 4 ug/ml
   2. Start Dose: 2 ug/min
   3. Titrate: 2-10 ug/min to clinical response
      1. Heart Rate over 60 beats per minute
7. Precautions
   1. Decreases Diastolic Blood Pressure
      1. No alpha adrenergic effect
      2. Increases Heart Rate (less diastolic filling time)
   2. May precipitate Myocardial Ischemia
      1. Increases myocardial oxygen demand
      2. Decreases coronary perfusion
   3. Induces Arrhythmias
      1. Ventricular Tachycardia
      2. Ventricular Fibrillation
   4. Exacerbates tachyarrhythmias due to Digitalis Toxicity
   5. Precipitates Hypokalemia