Inhaled Nitric Oxide
INOmax
Selective pulmonary vasodilator (inhaled gas)
Inhaled NO diffuses to pulmonary vascular smooth muscle → ↑ cGMP → SELECTIVE pulmonary vasodilation only in VENTILATED lung units (improves V/Q matching). Inactivated by hemoglobin before reaching systemic circulation → no systemic hypotension.
Indications
- •Persistent pulmonary hypertension of the newborn (PPHN)
- •Acute pulmonary hypertension / RV failure (cardiac surgery, transplant)
- •Refractory hypoxemia / ARDS (rescue)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Inhaled | Start 20 ppm; wean slowly (rebound pulmonary HTN on abrupt stop) | — |
Pharmacokinetics
Onset minutes; effect only while inhaled (seconds half-life once bound to Hb).
Hemodynamic effects
Lowers PVR without lowering SVR (selective) → unloads the RV.
Respiratory effects
Improves oxygenation via V/Q improvement in ARDS (transiently).
Side effects
- !METHEMOGLOBINEMIA (monitor metHb)
- !Rebound pulmonary HTN on abrupt withdrawal — wean slowly
- !NO₂ formation (toxic — monitor)
- !Platelet inhibition
Contraindications
- ×Left-heart failure / high LAP (can precipitate pulmonary edema)
- ×Abrupt discontinuation
Clinical pearls
- ★SELECTIVE pulmonary vasodilator — lowers PVR without systemic hypotension (Hb inactivates it before systemic circulation).
- ★NEVER stop abruptly — rebound pulmonary hypertension/RV failure; wean. Monitor methemoglobin + NO₂.
Other drugs in Others
- Dantrolene
Blocks RYR1 (ryanodine receptor) → ↓ Ca²⁺ release from sarcoplasmic reticulum → muscle relaxation. The only drug for malignant hyperthermia.
- Lipid Emulsion 20%
Theory: 'Lipid sink' sequesters lipophilic drugs (especially LAs), shifts to better Ca²⁺ handling, fatty acid metabolic support.
- Hydroxocobalamin
Vitamin B12a precursor; cyanide binds to cobalt center of hydroxocobalamin → forms cyanocobalamin (B12) → renal excretion. Also scavenges nitric oxide → vasoconstriction.
- Octreotide
Long-acting somatostatin analogue → suppresses splanchnic blood flow, GI/pancreatic secretions, GH, glucagon, insulin, and serotonin/vasoactive-peptide release.
- Alvimopan
Blocks GI mu-opioid receptors WITHOUT crossing the blood-brain barrier → reverses opioid-induced gut slowing while preserving central analgesia. Accelerates return of bowel function.
- Phentolamine
Competitive, reversible α1 + α2 blockade → vasodilation. Short-acting.
- Digoxin Immune Fab
Ovine Fab fragments bind free digoxin → the complex is renally excreted → rapidly reverses digoxin/digitoxin toxicity.
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert
