Glyceryl Trinitrate (GTN) Spray

Question 1

GTN Indications

Answer 1

1. Myocardial ischaemia
2. Cardiogenic pulmonary oedema
3. STEMI, Control of hypertension (usually in conjunction with Labetalol) prior to fibrinolytic treatment for STEMI, or during inter-hospital transfer for STEMI.
4. Control of hypertension associated with autonomic dysreflexia

Question 2

GTN Contraindications

Answer 2

1. Known severe allergy
2. Systolic BP less than 110 mmHg
3. Heart rate less than 40/minute
4. Heart rate more than 150/minute
5. Ventricular tachycardia

Question 3

GTN Cautions

Answer 3

1. STEMI, particularly STEMI involving the right ventricle, if there are signs of low cardiac output
2. The patient is frail
3. Signs of shock
4. Dysrhythmia
5. Has taken a phosphodiesterase inhibitor in the last 24 hours
6. Known aortic or mitral stenosis

Question 4

GTN Dose for Myocardial Ischaemia

Answer 4

0.4 mg every five minutes. Consider increasing interval to ten minutes if caution is present

Question 5

GTN Dose for STEMI

Answer 5

O.4 mg with caution. Withhold if signs of poor perfusion are present

Question 6

GTN Dose for cardiogenic pulmonary oedema

Answer 6

0.8 mg every five minutes. Consider increasing the dosing interval to ten minutes if a caution is present. Increase the dose and frequency is patient is not improving

Question 7

GTN Dose for Control of Hypertension

Answer 7

0.4 mg every five minutes

Question 8

GTN Route and Administration (when caution is present)

Answer 8

• IS, sprayed under tongue
• If administered in presence of a caution;
  > patient should be sublime
  > IV assess should have been obtained whenever possible
  > the dosing interval should be increased to ten minutes
  > Be ready to administer 0.9% sodium chloride IV if there is a significant fall in cardiac output or blood pressure

Question 9

GTN Common Adverse Effects

Answer 9

1. Hypotension
2. Headache, flushing and feeling light-headed
3. Tachycardia

Question 10

GTN Mechanism of Action

Answer 10

• MOA is not clear, but it results in the formation of nitric oxide which is a vasodilator causing;
  > A reduction in venous return (preload) to the heart and Arterial dilation which reduces peripheral resistance (after load) to the heart hence reducing the myocardial oxygen demand