GTN Spray

Question 1

GTN - Mechanism of action

Answer 1

GTN is a vasodilator.
It acts on vascular smooth muscle to cause venous and arterial vasodialation, with main effect on veins.

GTN causes a reduction in venous return (preload) to the heart by reducing ventricular filling and cardiac output, which reduces myocardial oxygen demand.
It also causes arterial dilation which reduces peripheral resistance (afterload). This reduces the force the left ventricle must overcome to eject blood to the arteries, which reduces myocardial oxygen demand.

Question 2

GTN - Indications

Answer 2

[3H+MC]
Myocardial Ischaemia.
Cardiogenic pulmonary oedema.
Hypertension associated with autonomic dysreflexia.
Hypertension prior to fibrinolytic treatment for STEMI.
Hypertension during inter-hospital transfer for STEMI.

Question 3

GTN - Contraindications

Answer 3

[415AV+]
Known severe allergy.
Systolic BP less than 100 mmHg.
Heart rate less than 40/minute.
Heart rate greater than 150/minute
Ventricular tachycardia.

Question 4

GTN - Cautions

Answer 4

[SPADES]
STEMI, particularly right ventricle STEMI. If low cardiac output then withhold GTN.
Poor perfusion.
Aortic or mitral stenosis.
Dysrhythmia.
Erectile dysfunction drug has been taken in the last 24 hours.
Small, frail, or physiologically unstable patient.

Question 5

GTN - Dosage

Answer 5

Myocardial Ischaemia: 0.4mg every 3-5 minutes, increase to 10 minutes if caution is indicated.
Cardiogenic pulmonary oedema: 0.8mg every 3-5 minutes, increase to 10 minutes if caution is indicated.
Hypertension control: 0.4-0.8mg every 3-5 minutes.

Question 6

GTN - Common side effects

Answer 6

[HH-FTL]
Hypotension.
Flushing.
Headache.
Tachycardia.
Light-headedness.

Question 7

GTN - Onset of effect

Answer 7

1-2 minutes

Question 8

GTN - Duration of effect

Answer 8

15 - 30 minutes.

Question 9

GTN - Preparation

Answer 9

metered dose bottle delivering 0.4mg doses.

Question 10

GTN - Repeats

Answer 10

Every 3-5 mins, increasing to 10 mins if caution required