Nitroglycerin (Nitrostat)

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 - Potent vasodilator. Monitor blood pressure closely, especially in hypovolemic patients. Be prepared to administer vasopressors and adjust anesthetic depth. Also dilates arterioles at higher doses (reduces afterload)

Preload reduction - Primarily dilates venous capacitance vessels, reducing right heart filling pressure and myocardial oxygen demand.

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

Reflex tachycardia - Vasodilation may trigger compensatory tachycardia, increasing myocardial oxygen demand and potentially worsening ischemia.

Increased cerebral blood flow - May raise ICP due to cerebrovascular dilation; exercise caution in neurosurgical patients or those with pre-existing intracranial hypertension.

Methemoglobinemia - Can occur at high doses; reduces oxygen-carrying capacity. Monitor for signs (cyanosis unresponsive to O₂, chocolate-brown blood) and have methylene blue available for treatment (1–2 mg/kg IV over 5 minutes)

Infusion Equipment - Use mandatory non-PVC infusion systems, as Nitroglycerin is absorbed by PVC tubing, which can affect the dosing and effectiveness.

Headache - Common due to meningeal vasodilation; most pronounced with sublingual and transdermal routes in awake patients.

Uterine relaxation - IV bolus 50–100 µg (1–2 µg/kg) provides rapid, titratable uterine relaxation for retained placenta, fetal manipulation, or uterine inversion. Effect is brief, allowing uterotonic agents to be administered shortly after.

Hypotension in the parturient - Obstetric patients are especially sensitive to vasodilation; have ephedrine or phenylephrine immediately available.

Drug Interactions - Phosphodiesterase inhibitors (e.g., sildenafil) taken in conjunction with nitroglycerin can cause profound, potentially life-threatening hypotension due to synergistic vasodilation. Any other antihypertensive medications will have additive effects with nitroglycerin. IV nitroglycerin infusions may reduce heparin anticoagulant effect; monitor aPTT and adjust heparin dosing accordingly.

Absolute - Hypotension (SBP < 90 mmHg), uncorrected hypovolemia, concurrent PDE-5 inhibitor use (sildenafil, tadalafil, vardenafil), increased intracranial pressure, constrictive pericarditis, pericardial tamponade, severe anemia

Relative - Hypertrophic obstructive cardiomyopathy (HOCM), recent use of erectile dysfunction medications, significant bradycardia or tachycardia

Use Caution - Elderly patients, patients on antihypertensives, aortic/mitral stenosis, hepatic or renal impairment, high-dose infusions (methemoglobinemia risk)

Dilute 1 mg in 20 mL D5W or NS to make 50 µg/mL

Slow IV bolus- 25-100 µg (0.5-2.0 µg/kg).

Controlled Hypotension / Antianginal / Pulmonary Edema / CHF - 5–200 µg/min (0.1–4.0 µg/kg/min); titrate to effect

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.

Hepatic

Renal

None

Transdermal Ointment - 0.5–2.0 inches q8 hours

Storage - Nitroglycerin is light-sensitive and volatile; store in original amber glass container. IV preparations should be protected from light.