Nitroglycerin (Nitrostat)

Anesthesia Implications

Classification: Organic Nitrate (Vasodilator)
Therapeutic Effects: Vasodilation, Venodilation, Antianginal, Hypotensive, Uterine relaxant
Time to Onset: IV: 1 – 2 minutes
Time to Peak: 1-5 minutes
Duration: IV: 3-5 minutes

Contraindications

Hypotension, uncorrected hypovolemia, increased intracranial pressure, constrictive pericarditis or pericardial tamponade, severe anemia

Primary Considerations

Vasodilator – Nitroglycerin causes vasodilation of BOTH venous and arterial (at high doses) components of the vasculature.

Augments diastolic function – Promotes diastolic relaxation / ventricular filling

Evaluate the Patient – Before administering Nitroglycerin, evaluate the patient’s blood pressure, volume status, and baseline cardiac function, as it can significantly reduce systemic vascular resistance and preload.

Hypotension Risk – Since Nitroglycerin is a potent vasodilator, monitor blood pressure closely, especially in patients with hypovolemia or hypotension.

Cerebrovascular Effects – Dilates cerebral vessels, increases cerebral blood flow (CBF), and increases intracranial pressure (ICP).

Improved pulmonary gas exchange – when compared to nitroprusside, nitroglycerin does a better job improving pulmonary gas exchange.

Methemoglobinemia – At high doses, Nitroglycerin can induce methemoglobinemia; Watch for symptoms and have methylene blue available for treatment if needed.

Use non-PVC infusion tubing (typically blue in color ) – Nitroglycerin is absorbed by PVC tubing, which can affect the dosing and effectiveness.

Close Monitoring – Plan for frequent blood pressure monitoring and readiness to adjust anesthesia depth or additional vasopressors as needed to maintain hemodynamic stability.

OB – Preeclamptic patients should have volume expansion prior to administering NTG. Nitroglycerin readily crosses the placenta and causes fetoplacental vasodilation while protecting uretoplacental perfusion. With NTG, there’s no cyanide Poisoning as seen with nitroprusside. For this reason it may be preferred in the parturient to avoid fetal cyanide poisoning.

IV push dose

Typical Preparation: 50mg in a 500 ml bag of NS (100mcg/ml)

Controlled Hypotension / Antianginal / Pulmonary Edema / CHF:
Slow IV bolus- 25-100 µg (0.5-2.0 µg/kg).

Uterine Relaxation:
Slow IV Bolus- 50-100 µg (1-2 µg/kg). Dilute 1 mg of parenteral concentrate with 20 mL D5W or normal saline (50 µg/mL).

IV infusion dose

Typical Preparation: 50mg in a 500 ml bag of NS (100mcg/ml). Make sure to use nonabsorbent tubing (typically blue in color)

Controlled Hypotension / Antianginal / Pulmonary Edema / CHF:
IV infusion- 5-200 µg/min (0.1-4.0 µg/kg/min)

Reversal

No reversal agent

Method of Action

Nitroglycerin releases nitric oxide, which activates guanylate cyclase, increasing cyclic GMP in vascular smooth muscle cells. This leads to dephosphorylation of myosin light chains, causing smooth muscle relaxation and vasodilation.

Metabolism

Hepatic

Elimination

Renal