Cardiac vasodilators (paediatric)

Intraoperative

Patients less than 1 year of age who are going to be cooled to less than 28°C may benefit from vasodilatation prior to cooling to allow for even cooling and some afterload reduction post pump.

Previously this was achieved with phenoxybenzamine or phentolamine but as these drugs are no longer available there is limited choice on what to use.

Gyceryl Trinitrate (GTN),  Sodium Nitroprusside (SNP) or Nicardipine can be used.

Glyceryl Trinitrate (GTN)

• Can be given by infusion

• Usual dose is 0-5mcg/kg/min

• Effect can be variable and is not as potent a dilator as SNP

• Tachyphylaxis develops within 24 hours.

Sodium Nitroprusside (SNP)

• Can also be given by infusion in the same dose range as GTN

• It has a rapid onset of action and can cause a precipitous drop in blood pressure

• Start at a low dose (0.5mcg/kg/min) and avoid giving as a bolus

• Toxic metabolites of SNP can accumulate with high doses (>5mcg/kg/min) or prolonged infusions (>24hrs) especially in patients with renal impairment

Nicardipine

• can be used by infusion in a similar dose range (0.5-5mcg/kg/min).

Postoperative

Postoperative hypertension needs treating to prevent excessive bleeding and to limit cardiac afterload. Treatment involves ensuring adequate analgesia and sedation, eliminating seizures as a cause, ensuring the patient is not hypervolemic, and treating the hypertension with an infusion of either glyceryl trinitrate or sodium nitroprusside.

Milrinone is an effective inodilator which may decrease the blood pressure but it should NOT be used to treat hypertension postoperatively.

Patients requiring ongoing treatment for hypertension can be transitioned to captopril when stable.

To prevent post-op bleeding control of systolic BP is important.