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14 Cards in this Set
- Front
- Back
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GTN MOA |
Vasodilator. Acts on smooth muscle to cause venous and arterial vasodilation, with predominant effects on veins. MOA not clear, but it appears GTN results in the formation of nitric oxide which is a vasodilator. GTN causes - reduction in venous return (preload) to the heart. This reduces ventricular filling and cardiac output, which reduces myocardial 02 demand. - arterial dilation which reduces peripheral resistance (afterload). Reduces the force the LV must overcome to eject blood into the arteries which reduces myocardial 02 demand. - dilation of coronary arteries, increases coronary blood supply (not usually clinically significant). |
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GTN INDICATIONS |
1. Myocardial ischaemia. 2. CPO. 3. HTN with autonomic dysreflexia. 4. HTN prior to fibrinolytic treatment of STEMI. 5. HTN during inter-hospital transfer for STEMI. |
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GTN CONTRAINDICATIONS |
1. Know severe Ax. 2. Systolic BP less than 100mmHg. 3. Heart rate less than 40/min. 4. Heart rare greater than 150/min. 5. VT. |
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GTN CAUTIONS |
1. STEMI, particularly involving right side (V1 + V4R). GTN can cause a significant fall in cardiac output due to poor RV contractility in combination with reduced preload from the GTN.
2. The pt is small, frail or physiologically unstable.
3. Poor perfusion. As it is a sign of reduced cardiac output, which may fall further with GTN administration.
4. Dysrhythmia. Reduced cardiac output which may fall further.
5. A drug for erectile dysfunction taken within 24hrs.
6. Known aortic or mitral stenosis. The narrowed valve may already cause low cardiac output. A fall in preload will cause a further fall in cardiac output. |
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GTN in PREGNANCY |
Safety not demonstrated. Likelihood of a pregnant or breastfeeding pt to req GTN is very low, but should be given if indicated. |
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GTN DOSAGE |
Myocardial Ischaemia - 0.4mg every 3-5 Mins. Increased to every 10 mins if caution is req.
HTN and AD - 0.4-0.8mg every 3-5 mins.
CPO - 0.8mg every 3-5 Mins. Dosing interval to 10 mins if caution req. Increase dose and frequency if pt not improving, providing systolic BP is above 100 mmHg. |
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GTN ADMINISTRATION |
Spray under tongue or in mouth. GTN administered under caution: - lie flat - IV access - dosing interval to 10 mins - ready to administered 0.9% NaCl |
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GTN ADVERSE EFFECTS |
1. Hypotension. 2. Flushing. 3. Headache. 4. Tachycardia. 5. Feeling light-headed. |
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GTN ONSET |
1-2 mins |
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GTN DURATION |
15-30 mins |
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GTN PREPARATION |
Metered spray 0.4mg |
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GTN PHARMACOKINETICS |
Rapidly absorbed from the oral mucosa and reaches the vascular system without passing through the liver. Predominantly metabolised in the liver. No significant effects to liver on acute administration. |
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GTN INTERACTIONS |
Effects may increase if taking an anti-hypertensive.
Severe and/or prolong hypotension if taking erectile dysfunction medication. Range of names, particularly sildenafil, are used in the tx of pulmonary HTN also. Normally long-acting vasodilator, GTN can cause further vasodilation. |
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GTN additional INFO |
Used with caution in STEMI as risks may outweigh benefits. - can cause a significant fall in cardiac output. - role in tx symptomatic myocardial ischaemia, but not usually significant role in tx STEMI. Particular caution in RV STEMI... Significant reduction in RV contractility. Because its impaired it provides little contribution to cardiac output and blood may be passively flowing down pressure gradient from IVC/SVC/Left atrium. This results in LHS of heart being dependent on venous pressures. GTN can result in significant fall in venous pressures (and preload) which causes significant fall in cardiac output. |
