Dose:  0.05 to 0.5 mcg/kg/minute IV as a continuous infusion

Comments:  Isoproterenol is used to increase cardiac output in cases of cardiogenic shock associated with asphyxia; it is also used to treat PPHN, bradycardia due to A-B blocks, and myocardial dysfunction. With IV infusions, cardiac output is increased by both increasing the heart rate and by increasing the strength of the contractions. Peripheral resistance is decreased (afterload reduction) as a result of vasodilatation. There tends to be a decrease in blood flow to critical tissues (kidney, myocardium, and brain) with the changes in blood pressure because vasodilatation increases blood flow to the skeletal muscles and mesenteric vascular bed. It appears to be of no value in cardiac resuscitation.  Its use in newborns appears to be limited to situations of low cardiac output due to bradycardia, particularly with the A-V blocks that follow cardiac surgery.  See further comments on isoproterenol.  

Toxicity:  Cardiac arrhythmias and myocardial necrosis are the most serious potential side effects. As noted above, use may also cause hypotension, especially if the intravascular volume is low. Isoproterenol aggravates myocardial ischemia because of the increased oxygen demand caused by tachycardia. Rapidly fatal cardiovascular deterioration has also been reported following the use of isoproterenol (Roberts. Drug Therapy in Infants. Philadelphia: W. B. Saunders, 1984:172).

Preparation: Isoproterenol (Isuprel) is available in a 1 ml ampule with a 1:5,000 concentration (0.2 mg/ml) that is stored in the refrigerator. It will be sent up to the NICU in a 50 mcg/ml concentration. Do not use if a color or precipitate is present.  Using the 50 mcg/ml concentration, a programable pump can be used to set up an isoproterenol drip. The following check sheet using the 50 mcg/ml concentration of isoproterenol can be used as a double check.

Another isoproterenol preparation is available in a premixed syringe with a 1:50,000 concentration (0.02mg/ml or 20 mcg/ml). This is currently not used at SJMMC. If used, the solution should be transferred to a syringe so the continuous infusion can be administered using a syringe pump. To administer a 0.1 mg/kg/min infusion, the rate in "ml/hour" is determined by muliplying the infant's weight (Kg) by 0.3. 

To double check the concentration of isoproterenol in a nonstandardized concentration:
formulas used to double check the concentration of isoproterenol.

Compatibility: Compatible with TPN and lipids, but not filter. Also compatible with D2.5, D5W, D5LR, LR, and NS as well as amiodarone, amrinone, atracurium, calcium salts, dobutamine,  famotidine, heparin, hydrocortisone, insulin, labetalol, magnesium sulfate,  multivitamins, pancuronium, potassium chloride, propofol, ranitidine, and vecuronium. It is incompatible with aminophylline, furosemide, lidocaine, phenobarbital, and sodium bicarbonate. In solutions with pH > 6.0, significant decomposition of the drug occurs.