Emergency Medical Symposium

Clinical Pearl 70 : Push Dose Nitroglycerin (PDN)

65 year old male with severe respiratory distress.

Initial impression presents an obese 65 year old male with gross respiratory distress, tripod, audible rales and with one word sentences, pale, diaphoretic and anxious. High flow nasal cannula underneath a CPAP mask with 10 cmH2O of PEEP is placed. Initial vital signs of RR 36 ppm, HR 118, irregular, BP 210/108, SpO2 93 % on 100% oxygen.

Primary survey is as above, GCS 15, no focal neurological deficits, unremarkable skin inspection, no s/s of trauma. SAMPLE history significant for increasing DOE with orthopnea and PND x 2 weeks, worse today. NKDA, Metformin, coreg, ASA, Lipitor, Glipizide, amlodipine, lasix and plavix. CAD s/p PCI with stents, AFib, DM2, hypercholesterolemia, HTN

12 lead ECG narrow-complex Afib with RVR @ 120 bpm, lateral T-wave inversion. Repeat VS unchanged. 

So what’s our next step…CPAP, IV Access, and maybe Lasix in select cases.  Nitroglycerin for preload reduction… Tabs, spray or paste is not going to work; leaves nitroglycerin infusion. NTG Infusions have been effective, depending on how aggressive the dosing schedule, nitro can rapidly reduce the blood pressure and after load.

KEY FACTS:

•    Standard NTG Infusion concentration is 200 mcg/mL; 50mg of Nitroglycerin in 250 mL of D5W either pre-mixed in a glass infusion vial or mixed at the beside.

•    Nitro infusions can be given using the 3/10 rule. Every 3 mL/hr is equal to 10 mcg/min of NTG infusion. For example: 50 mcg/min is 15 mL/hr infusion (3 x 5=15), 200 mcg/min is 60 ml/hr (3 x 20=60), 400 mcg/min is 120 mL/hr infusion (3 X 40=120).

•    Every 2 mL of Nitro Infusion is 400 mcg, equal to one SL tablet or spray pump.

•    If 1 tablet or 2mL bolus is given every 5 minutes, this equals 80 mcg/min.

•    Sublingual administration is very similar to IV infusion in bioavailability and time of onset.

•    Leave the pump in the cabinet and give 1 mL to 2 mL of the standard NTG Solution every minute, 200-400 mcg/min, titrated to effect.

•    Using a 10 fold dilution of the concentrated vial can be used as a Push Dose Nitro Solution. 5 mg (1 mL of the concentrated NTG Vial) mixed with 9 mL of Saline is 500 mcg/mL. Give 1 mL or 500 mcg every 60-90 seconds to lower the blood pressure.

Nitroglycerin lowers preload via venous vasodilation at low doses and lowers after load via arterial vasodilation at high doses, this makes our vascular container larger lowering the systemic pressure. Aggressive, high dose NTG paired with the recruitment of the alveoli using CPAP & PEEP make up the mainstay of pre-hospital treatment of APE and decompensated heart failure. Bolus doses as high as 2 mg (2000 mcg) of nitroglycerin have been given safely and effectively in previous studies.

In emergent resuscitations we need to focus on bolus dose medications in the acute phase versus starting and titrating critical care infusions while a patient is in extremis. The goal is to achieve clinical end points of treatment faster with bolus dosing at the bedside and then begin maintenance infusions once resuscitation goals are met and the hemodynamics are stable.

Stay tuned for a protocol

References:

Hsiao, R, et al. “Contemporary Treatment of Acute Heart Failure”. Progress in Cardiovascular Diseases. 2016;58:367-378.

Scott, MC & Winters, ME. “Congestive Heart Failure”. Emerg Med Clin N Am. 2015;33:553–562.

Mattu, A & Lawner B. “Prehospital Management of Congestive Heart Failure” Heart Failure Clin. 2009;5:19–24.

Weingart, S. “Sympathetic Crashing Acute Pulmonary Edema” EMCrit Podcast #1, 2009. http://emcrit.org/podcasts/scape

Levy, P; et al. “Treatment of Severe Decompensated Heart Failure With High-Dose Intravenous Nitroglycerin: A Feasibility and Outcome Analysis”. Ann Emerg Med. 2007;50:144-152.

Zalenski, RJ; et al. “The Feasibility of Treating Severe Acute Congestive Heart Failure With Bolus Intravenous Nitroglycerin”Ann Emerg Med. 2004;44.