Nitroglycerin

In this lesson, we'll go over the medication nitroglycerin and all of its effects, including indications, precautions and contraindications, and adult dosages. At the end of the lesson, we'll continue our look at respiratory problems, specifically respiratory failure.

Nitroglycerin is a nitrate that causes smooth muscle relaxation, which produces systemic venous pooling of blood through the action of vasodilation. This, in effect, decreases venous blood flow return to the heart and also reduces preload as well as venous after load.

Nitroglycerin Indications

Now let's take a look at nitroglycerin indications.

Nitroglycerin is indicated to relieve chest discomfort that is suspected to be the result of acute myocardial infarction, otherwise known as AMI.

Nitroglycerin can also be effective in relieving cardiogenic pulmonary edema that is related to left side heart failure.

Nitroglycerin Precautions and Contraindications

Now let's go over the precautions and contraindications for nitroglycerin.

There are multiple situations when the use of nitroglycerin may not be indicated or may even be contraindicated and harmful to the outcome of the patient.

Here are some examples of those contraindicated situations:

• The patient is suffering from low systolic blood pressure of less than 90mm HG
• The patient has a right-sided ventricular infarction
• The patient is using medications like tadalafil, better known as Cialis or Adcirca
• The patient has severe bradycardia of fewer than 50 beats per minute
• The patient has a tachycardia greater than 100 beats per minute in the absence of heart failure

Different from tadalafil, but in the same class of complications with nitroglycerin, when a patient may be taking a phosphodiesterase type 5 (a class of medication that includes Sildenafil) within the past 24 hours, this could cause severe hypotensive side effects if the patient is using that medication and also taking nitroglycerin.

Adult Dosage of Nitroglycerin

Now let's look at the adult dosage of nitroglycerin.

There are three methods of administering nitroglycerin:

1. Nitroglycerin can be administered sublingually (under the tongue) in a dose of 0.4 mg, which is typically one tablet. This dose can be repeated in 5-minute intervals to a maximum dose of 3 tablets.
2. Nitroglycerin can also be administered via a sublingual spray in metered doses. One spray of nitroglycerin will usually be the equivalent of a 0.4 mg tablet. This, too, can be repeated in 5-minute intervals to a maximum dose of 3 sprays.
3. And finally, nitroglycerin can also be administered via IV and may be increased to 10 mcg per minute every 3 to 5 minutes until you've reached the desired effect.

A Word About Respiratory Failure

In the last lesson on morphine sulfate, we took a look at respiratory distress. In this Word, we'll look at respiratory failure.

Respiratory failure is a clinical state of inadequate oxygenation, ventilation, or both. Respiratory failure is often the end stage of respiratory distress.

If there is abnormal central nervous system control of breathing or muscle weakness, the patient may show little or no respiratory effort despite being in respiratory failure. In these types of situations, you will have to identify the patient's respiratory failure based on clinical findings.

It's important to confirm the diagnosis with objective measurements, such as pulse oximetry or blood gas analysis.

You should suspect the probability of respiratory failure if you notice some or all of the following signs:

• Marked tachypnea
• Bradypnea, apnea (late)
• Increased, decreased, or no respiratory effort
• Poor to absent distal air movement
• Tachycardia (early)
• Bradycardia (late)
• Cyanosis
• Stupor or coma (late)

Respiratory failure can result from upper or lower airway obstruction, lung tissue disease, and disordered control of breathing, such as apnea or shallow, slow respiration. When respiratory effort is not adequate, respiratory failure can occur without the usual signs of respiratory distress.

Respiratory failure is a clinical state that requires intervention to prevent its deterioration into cardiac arrest. Respiratory failure can occur with a rise in arterial carbon dioxide levels (hypercapnia), a drop in blood oxygenation (hypoxemia), or both.