CRIT BIT CORNER

Intro to Inhaled Nitric Oxide and Veletri

Inhaled nitric oxide (iNO) and inhaled Veletri (epoprostenol) are selective pulmonary vasodilators. Delivered through the airway, they relax blood vessels inside ventilated lung units, improving oxygenation and lowering pulmonary artery pressures without causing systemic hypotension—a huge advantage when the right ventricle (RV) is struggling and the blood pressure is fragile [1–4]. We use them as rescue/bridge therapies in hypoxemia (e.g., ARDS) and pulmonary hypertension or RV failure while definitive treatments—proning, diuresis, anticoagulation/reperfusion, valve management—are pursued [2–4].

Clinical Effects & Hemodynamic Benefits

Oxygenation

PaO₂/FiO₂ often improves within minutes as perfusion is redirected to ventilated lung; FiO₂ and/or PEEP requirements may fall after stabilization [2–4].

Pulmonary Hypertension/RV Afterload

Both agents lower PVR and pulmonary artery pressure, easing RV wall stress and improving forward flow; the interventricular septum may “round up” as RV pressure falls [2–4].

Systemic Blood Pressure

Typically maintained because the vasodilator effect is lung-limited; this is particularly helpful in shock states where systemic vasodilation would be dangerous [1–4].

CAUTION: If left-sided failure (or pulmonary veno-occlusive disease) dominates, selective pulmonary vasodilation may worsen pulmonary edema by increasing flow into a congested left atrium; start carefully and reassess early [2,4].

Contraindications & Precautions

Dominant Left-Sided Heart Failure Or Suspected Pulmonary Veno-Occlusive Disease

Risk of pulmonary edema after vasodilation; treat congestion first and titrate cautiously [2,4].

iNO-Specific

• Risk of rebound pulmonary hypertension if stopped abruptly
• Methemoglobinemia (dose/duration related)
• Nitrogen dioxide (NO₂) formation at higher concentrations—monitor and titrate thoughtfully [1,3].

Veletri-Specific

• Platelet inhibition is milder with inhalation than IV but still relevant in bleeding-risk contexts.
• Avoid abrupt interruption to prevent rebound [2,4].

Both Agents

Use caution when severe LV dysfunction is suspected; re-evaluate the primary physiology if oxygenation worsens after initiation [2,4].

Dosing, Delivery & Monitoring

Inhaled Nitric Oxide (iNO)

Start: commonly 10-20 ppm via ventilator circuit; delivery via HFNC or other interfaces is possible with specialized setups (dilution may require higher device settings) [2–3]. Assess response quickly: check SpO₂/ABG, ventilator/FiO₂ needs, and RV surrogates (JVP/CVP, echo) within minutes; a clinically meaningful response is often a ≥10–20% improvement in PaO₂/FiO₂ or clear RV unloading [2–4]. Wean slowly: reduce in small steps with pauses; if SpO₂ falls or Pulmonary Artery Pressure (PAP) surges, return to the last effective dose and stabilize—this prevents rebound [1,3]. Safety monitoring: daily methemoglobin and NO₂ for ongoing therapy or higher dosing; follow renal function with prolonged courses [1,3].

Inhaled Veletri

Typical ICU initiation: 50 ng/kg/min (a common “max start”) using a vibrating-mesh nebulizer placed near the Y-piece of the inspiratory limb, then titrate down as oxygenation and RV metrics improve [2,4]. Interfaces: invasive ventilation, NIV, or HFNC; extremely high HFNC flows can reduce deposition (consider mid-range flows when feasible) [2]. Wean thoughtfully: stepwise reductions (e.g., 50 → 40 → 30 ng/kg/min) with reassessment every 15–30 minutes; avoid abrupt cessation to prevent rebound [2,4]. Safety monitoring: SpO₂/ABG, BP, bleeding context, and continuous device checks (power, tubing, condensation management, alarms) [2,4].

Key Takeaways

Mechanisms: iNO = NO–cGMP; iEPO = PGI₂–cAMP. Both vasodilate ventilated lung, improve V/Q, and reduce PVR/RV afterload without systemic hypotension [1–4]. Use cases: ARDS with refractory hypoxemia; acute/decompensated PH or RV failure; postcardiac surgery RV dysfunction; PE with RV strain—as bridges while definitive therapy proceeds [2–4]. Dosing anchors: iNO ~20 ppm start with careful monitoring for methemoglobin/NO₂ and slow wean; inhaled Veletri 50 ng/kg/min start with stepwise down-titration and no abrupt stops [1–4]. Safety: watch for rebound PH, methemoglobinemia (iNO), bleeding context (iEPO), and device issues. If pulmonary edema worsens, reconsider LV physiology and diuresis [1–4]. Execution matters: Optimize lung recruitment, protect pH/PaCO₂ (both affect PVR), treat the cause, and document response windows and weaning steps clearly [2–4].