Companion Document Cardiac Ischemia - Prior Nitro History as "previously prescribed nitro"

Question#: 581

Question:

In the companion document about cardiac ischemia, prior nitro history is defined as previously prescribed nitro. Does the patient have to had taken the prescribed nitro before?

I’ve come across a patient who’s been prescribed nitro, but never taken a spray or been given a spray at hospital/clinic or any other medical facility. Can we still treat that patient with nitro?

Answer:

The ALS PCS states that a condition is prior history of nitroglycerin USE. When the Companion Document describes prior history as authorised or prescribed by a medical doctor, this does not remove the requirement of previous use but adds to the requirement that the prior use was medically advised. Thus, the patient must have actually used nitrates at least once under the under guidance of a physician. Should you have a nitrate naïve patient with a recent prescription for nitrates you may patch for a BHP consultation.

Therefore, a "prior history of nitroglycerine use" is defined as previously authorized or prescribed to the patient for use by a certified Medical Doctor and at least one prior use.

The reasons for the caution are:
* Hypotension is one of the primary side-effects of nitrate use and the incidence of hypotension is more likely in patients with ventricular ischemia.
* Hypotension increases mortality in patients having an acute myocardial infarction.
* While nitrates do reduce cardiac workload and ischemic pain they do not provide a survival benefit in cardiac ischemia.

References
* Reeder, G., 2021. Nitrates in the management of acute coronary syndrome. UpToDate, accessed 02 March 2022.
* Reyentovich, A.,2020. Prognosis and treatment of cardiogenic shock complicating acute myocardial infarction. UpToDate, accessed 02 March 2022.