Dopamine 

Overview:

Dopamine is a neurotransmitter, which is a type of chemical messenger that transmits signals in the brain and other areas of the nervous system. It plays a crucial role in various physiological functions, including movement, motivation, and the regulation of mood. In the context of medical use, dopamine can also refer to a medication that acts as a synthetic form of the neurotransmitter. 

As a medication, dopamine is often administered intravenously to address specific medical conditions, especially those related to the cardiovascular system. In this medical context, dopamine functions as an inotropic agent, meaning it affects the force of muscle contractions, particularly in the heart. It can also have vasopressor effects, influencing blood vessel constriction or dilation. 

In neonatal and pediatric care, dopamine is sometimes used to support blood pressure and cardiac function in critically ill infants with hypotension. The medication is carefully administered based on the individual patient's needs and responses. 

1. Indications: 

Hypotension (Low Blood Pressure): Dopamine is commonly used to treat hypotension in neonates, especially in cases of shock or circulatory collapse, to help improve blood pressure and perfusion to vital organs.

• Cardiogenic Shock: In neonates with heart failure or poor cardiac output, dopamine helps increase cardiac contractility and output, improving tissue perfusion.

• Neonatal Sepsis: Sepsis can cause low blood pressure and poor perfusion, and dopamine is often used as part of the treatment to stabilize circulation and improve systemic blood flow.

• Congenital Heart Defects: For infants with ductal-dependent heart conditions (like hypoplastic left heart syndrome or transposition of the great arteries), dopamine can help support blood pressure and circulation until surgical intervention or other treatments are available.

• Acute Kidney Injury (AKI): Dopamine is sometimes used to improve renal perfusion in neonates with acute kidney injury, as it may promote urine output, though its use for this purpose is now more limited due to newer evidence.

• Management of Hypoperfusion: In neonates with poor tissue perfusion or shock (from causes like asphyxia, hypovolemia, or blood loss), dopamine helps increase perfusion and oxygen delivery to organs.

• PDA (Patent Ductus Arteriosus): In some cases, dopamine may be used to help maintain blood pressure and improve systemic circulation in neonates with a persistent PDA (although more often prostaglandins are used to treat PDA).

2. Contraindications: 

• Hypersensitivity to sympathomimetic amines and sulfites. 

• Uncorrected tachyarrhythmias. 

3. Precautions: 

• Hypovolemia: Correct before commencing dopamine. 

• Hyperthyroidism. 

• Caution if administration concurrent with phenytoin. 

4. Clinical Pharmacology: 

• Dopamine is a sympathomimetic catecholamine with alpha adrenergic, beta adrenergic, and dopaminergic agonism. 

• Mechanism of action in neonates is controversial due to developmental differences. 

• Metabolized rapidly, effective intravenously via continuous infusion. 

• Dose-dependent effects: 

• Low dose (2-5 micrograms/kg/minute): Little effect on heart rate or cardiac output, increased blood flow, and urine output. 

• Intermediate doses (5-15 micrograms/kg/minute): Increased cardiac contractility and output, elevated normal blood flow and heart rate. 

• High dose (15 micrograms/kg/minute): Alpha adrenergic effects dominate, increased vascular resistance, decreased blood flow, and cardiac output. 

5. Possible Adverse Effects: 

• Venous irritation, soft tissue injury at the injection site. 

• Vomiting, tachycardia, vasoconstriction, hypotension. 

• Infusions > 20 micrograms/kg/minute associated with increased dysrhythmia risk. 

• Less common: bradycardia, hypertension. 

6. Special Considerations: 

• Dosage range determined by desired clinical effect, start at the lower end, titrate based on response. 

• Volume loading considered before dopamine infusion. 

• Use with caution in persistent pulmonary hypertension of the newborn. 

• Tissue sloughing treatment: Inject 1 mg/ml phentolamine into the affected area. 

• Prolonged and intensified effects with beta blockers. 

• General anesthetic increases arrhythmia or hypertension risk. 

• Phenytoin may lower blood pressure. 

• Acidosis decreases dopamine effectiveness. 

• Administration via the umbilical arterial catheter (UAC) not recommended. 

Why is it important for an RT to understand dopamine?

It is important for respiratory therapists (RTs) to understand dopamine use in neonates because dopamine is a key medication used to support cardiovascular stability in critically ill newborns, particularly those with hypotension, shock, or heart failure. Dopamine acts by increasing blood pressure, improving perfusion, and enhancing cardiac output through its dose-dependent effects on dopaminergic, beta-1, and alpha-1 receptors. RTs should be aware of how dopamine can impact respiratory function, as it can lead to tachycardia and altered oxygen demand, which may affect ventilation settings and oxygenation strategies. Additionally, dopamine administration can influence the renal and gastrointestinal systems, which may require adjustments in fluid and electrolyte management. By understanding the effects and potential complications of dopamine therapy, RTs can better assess the neonate’s overall condition, anticipate changes in respiratory needs, and collaborate with the healthcare team to optimize care for the infant.