Introduction
Sympathetic crashing acute pulmonary edema (SCAPE) is a subset of hypertensive heart failure which develops
rapidly due to an abrupt increase in catecholamine release, subsequently leading to increased pulmonary capillary
permeability and flooding of alveolar space. Preload and afterload reduction is key and is managed with non-invasive
ventilation (NIV) and pharmacologic agents such as nitroglycerin. However, nitroglycerin has dose-dependent
afterload reduction that requires doses >50-150 mcg/min.
Clinical Detail
| Attribute | Nitroglycerin (NTG) |
|---|---|
| Dose | Chest pain: 5–400 mcg/min (starting at 5 mcg/min) Pulmonary edema/afterload reduction: 50–400 mcg/min Titrate to symptom improvement and tolerated blood pressure |
| Administration | IV infusion: 50–400 mcg/min until symptom resolution IV bolus: 400–2000 mcg in syringe over 2–5 min (check hospital policy) 400 mcg Sublingual tablet: 2–4 tablets (equivalent to 160–320 mcg/min of IV nitroglycerin) Ointment: slow onset 30–60 min |
| PK/PD | Onset: IV 1–5 min; sublingual 1–3 min Peak: IV/sublingual 3–15 min Duration: IV 5–10 min, sublingual 10–60 min Elimination: 22% renal |
| Adverse Effect | Headache Hypotension Syncope Rebound hypertension Tolerance with prolonged use ~24 hours |
| Warnings and Drug Interactions | PDE inhibitors Aortic stenosis, preload-dependent cardiomyopathy, hypertrophic obstructive cardiomyopathy, hypotension at any time |
| Compatibility | Incompatible with levofloxacin, SMX-TMP, daptomycin, and phenytoin |
Mechanism of Action
Nitroglycerin, an organic nitrate, is a vasodilating agent that relieves tension on vascular smooth muscle and dilates peripheral veins and arteries (at higher doses).
Evidence
| Author, Year | Design / Sample Size | Intervention & Comparison | Outcome |
|---|---|---|---|
| Patrick, 2020 | Observational n=48 | IV NTG 1 mg bolus by EMS | High dose NTG associated with: Decreased SBP by 31 mmHg from baseline Decreased HR by 10 beats per minute Increased O2 saturation from 86% to 98% 1/48 (2%) had symptomatic hypotension |
| Hsieh, 2018 | Case report n=3 | Sublingual NTG 0.6 mg/tab x 3 doses IV NTG bolus 1 mg every 2 min* IV NTG infusion 40 mcg/min* *If prior therapy failed | High dose NTG associated with: Normalize respiratory status No intubation + no ICU admission |
| Paone, 2018 | Case report n=1 | IV NTG infusion 400 mcg/min titrated by 50 mcg/min | High dose NTG bolus associated with: Symptomatic resolution @ 6 minutes |
| Wilson, 2016 | Observational n=395 | IV NTG bolus 500–2000 mcg Q3–5 min vs IV NTG infusion 20–35 mcg/min vs IV NTG bolus + infusion | High dose NTG bolus associated with: Decreased ICU admission Shorter LOS No differences in adverse outcomes (intubation) |
| Levy, 2007 | Observational n=29 | IV NTG Bolus 2 mg IV Q3 min | High dose NTG bolus associated with: Reduced intubation, need for bi-level positive pressure ventilation, and ICU admission |
| Sharon, 2000 | RCT n=40 | IV bolus isosorbide 4 mg Q4 min vs Isosorbide infusion starting @ 10 mcg/min + BiPAP | High dose isosorbide bolus associated with: Decrease intubations, MI, mortality, and improved PaO2 |
| Cotter, 1998 | RCT n=104 | IV isosorbide dinitrate 3 mg Q5 min + furosemide 50 mg vs IV isosorbide infusion 16 mcg/min titrate Q15min + furosemide 80 mg Q15 min | High dose isosorbide bolus associated with: Reduction in mechanical ventilation and MI Improvement in PaO2 and RR Less adverse effects |
Conclusions
- SCAPE is a catecholamine-driven subset of hypertensive heart failure where preload and afterload reduction is the priority, managed with non-invasive ventilation plus nitroglycerin.
- Afterload reduction with nitroglycerin is dose-dependent and requires doses above the conventional 50–150 mcg/min range; for pulmonary edema, infusions of 50–400 mcg/min (or bolus dosing of 400–2000 mcg) are titrated to symptom improvement and tolerated blood pressure.
- Observational data, case reports, and randomized trials of high-dose nitroglycerin or isosorbide bolus strategies reported improved oxygenation and reductions in intubation, ICU admission, and length of stay, with a low rate of symptomatic hypotension.
- Nitroglycerin must be avoided or used cautiously with PDE inhibitors, aortic stenosis, preload-dependent or hypertrophic obstructive cardiomyopathy, and any hypotension; headache, hypotension, and tolerance with prolonged use are the main adverse effects.
References
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