The other night one of
our hospitals sponsored a CME on cardiac emergencies. A local
cardiologist spoke to a group of EMTs from New York and New Jersey about the
in-hospital management of the STEMI (ST elevation myocardial infarction)
patients at this hospital. In the course of the discussion the use of
nitroglycerin was discussed. In less than a minute it became clear that
confusion exists on the pre-hospital BLS use of nitroglycerin in NYS by EMTs.
Hopefully this post will clear up some of the confusion.
Let’s review:
The NYS BLS Protocol
(Adult Cardiac Related Problem) allows NYS EMTs to assist a patient with the
use of THEIR previously prescribed nitroglycerin
in certain situations.
This means that we are
assisting a patient with taking their own prescribed nitroglycerin. NYS EMTs
and NYS BLS EMS units do not carry nitroglycerin. If the patient does not
possess their own prescribed nitroglycerin at the time of their cardiac event
we would therefore be unable to assist them in taking nitroglycerin. In other
words, you cannot use anyone else's nitroglycerin on your patients.
The situations where it
may appropriate for NYS EMT's to consider the use of nitroglycerin include
Angina Pectoris and Acute Myocardial Infarction.
So to assist a patient
with nitroglycerin the following criteria should exist:
1. The patient
should be experiencing signs and symptoms of symptomatic Angina Pectoris or
Acute Myocardial Infarction. This may include but is not limited too.
Chest, back and/or abdominal pain and/or discomfort from myocardial
ischemia. (Lack of O2 to the myocardium), difficulty in breathing, nausea / GI
complaints, diaphoresis (cool, pale, clammy skin), Always beware of atypical
presentations in some patients, especially the elderly, diabetics, and women.
Some patients may only present with fatigue, weakness, mild shortness of
breath, and pain to the jaw / arm.
2. The patient
must consent to treatment.
3. The patient's
systolic blood pressure must be higher than 120 mmHg.
4. The patient
must not have taken Sildenafil citrate (Viagra, Levitra, or Cialis) or similar
medications within 72 hours. These medications are primarily used to
treat erectile dysfunction in males; but may used to treat pulmonary
hypertension in both males and female patients.
5. Use nitroglycerin with caution in suspected nitroglycerin. An inferior wall myocardial infarction occurs when the inferior myocardial tissue supplied by the right coronary artery (RCA), is injured due to thrombosis of that vessel. When an inferior myocardial infarction extends to posterior regions as well, an associated posterior wall myocardial infarction may occur. Inferior wall myocardial infarction involves the lower (inferior) wall of the heart which sits above the diaphragm / stomach. Because of proximity to the abdomen many patients experiencing an inferior wall MI have more abdominal versus cardiac complaints. The reason why nitroglycerin should be used with caution is that approximately 40 % of inferior wall MIs have what is called right ventricular extension. Right ventricular extension means that the myocardial damage has extended from the inferior wall to include the right ventricle also. The right ventricle is pre-load dependent. Pre-load is the amount of de-oxygenated blood that is returning to the heart via the inferior and superior vena cava. Nitroglycerin causes vaso-dilation, which pools blood in the venous system. This pooling reduces the amount of blood available to return to the heart (pre-load). If we reduce pre-load we reduce cardiac output which leads to decreased blood pressure. Reduction to pre-load and blood pressure may reduce blood flow to the coronary arteries which may lead to larger damage in the myocardium. To summarize, if we give nitroglycerin to a patient who is experiencing an inferior wall MI we may drop perfusion to the heart muscle which may cause a larger amount of heart damage.
The next question should
be: How do we suspect an inferior wall MI on a BLS level? If you
have a suspected AMI patient who has more GI / Abdominal complaints then chest
complaints think inferior wall. There may also be an associated
bradycardia with inferior wall MI. Most AMI patients have an increase in
their heart rate to the chest pain and anxiety about their medical condition.
Some inferior wall MI patients will have bradycardia (HR 50 to 60) from
ischemia to the AV node or increased vagal tone. Suspected AMI patients with
abdominal symptoms / Complaints and bradycardia should receive nitroglycerin
with extreme caution even if their
blood pressure is above 120mmHg. If in doubt about what to do, start
transport, and contact medical control while enroute to your PCI (angioplasty)
center. What’s amazing is that the NYS protocol does not even address
this, nor do most BLS instructors even mention this.
Some facts about
inferior wall MIs:
- Inferior MIs account for 40-50% of all myocardial
infarctions.
- Up to 40% of patients with an inferior STEMI will have
a concomitant right ventricular infarction. These patients
may develop severe hypotension in response to nitrates and generally have
a worse prognosis.
- Up to 20% of patients with inferior STEMI will develop
significant bradycardia due to second- or third-degree AV block. These patients
have an increased in-hospital mortality (>20%).
- Inferior STEMI may also be associated with posterior infarction, which confers a worse
prognosis due to increased area of myocardium at risk.
6. If symptoms
persist you may administer up to 3 doses of nitroglycerin, 5 minutes apart, as
long as the B/P remains above 120 mm/Hg systolic. Just remember the more
nitroglycerin a patient receives the more likely it is for them to drop their
blood pressure.
7. Never give
nitroglycerin to a standing patient, wait to get them on the stretcher.
8. Sublingual nitroglycerin
is carried in spray or tablet (pill) form. Tablet form does not have a
great shelf life. One spray or one tablet is the same dose (0.4mg or 1/150th of
a grain). If a patient took their nitroglycerin prior to your arrival and
does not have relief from their symptoms check that they took it right way and
that it is not expired. Potency may also be an issue.
9. Potent (good)
nitroglycerin usually will cause a mild tingling / burning sensation under the
tongue if it is in the tablet form. Nitroglycerin spray or tablet usually causes
a mild headache.
10. Beside
nitroglycerin the treatment for the AMI patient should include:
a.
Early notification and transport to a PCI (angioplasty) center.
b.
Position of comfort. (To help relieve anxiety)
c.
O2 therapy. Even though it may not be clinically correct, NYS protocol
calls for high concentration O2. See my early post: EMS Myth -There's no
such thing as too much oxygen. What we should be saying: - Can Oxygen Hurt??? For
more info.
d. Aspirin.
See my early post on Pharmacology for more info.
Hope this help. If you have any questions or comments please
reply to this post.
Frank
