An appropriate dosage for this situation assumed acute angina pectoris would be one initial metered dose of 400 micrograms in order to relieve the chest pain experienced by the patient. If chest pain has not been relieved after 5 minutes from this then a second metered dose should be administered but not more than these two doses are recommended (Tam, 2006).
The patient's vital signs and history (particularly medications)?
There is a consideration to be made regarding tolerance due to the patient's previous use of GTN. Since tolerance to GTN has been demonstrated in clinical trials, in experience of occupational exposure and in isolated laboratory tissue experiments, intermittent therapy, such as demonstrated in the form of a sublingual spray, will reduce the likelihood of tolerance development (Bond, 2002).
2. Explain in point form:
The mechanism of action of GTN.
GTN is a powerful but short-acting nitrovasodilator.
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-mtALDH (mitochondrial aldehyde dehydrogenase) catalyses NO (nitric Oxide) from GDN (glyceryl dinitrate) after denitration of GTN.
NO is an activator (by heme-dependent mechanisms) of CG (guanylyl cyclase).
Resultant of this reaction is the forming of cGMP (cyclic guanosine monophosphate) from cGTP (cyclic guanosine triphosphate).
cGMP protein kinase then causes the activation of myosin light chain phosphatase.
(Marsh & Marsh, 2000)
The physiological rationale for administering GTN (i.e. what is the intended physiological outcome of administering GTN).
The veins and arteries dilate with the introduction of NO.
The dilation of the blood vessels provide less resistance and subsequently allows blood to be pumped more freely around the body, relieving the symptoms of the angina attack (which is caused by too little oxygen reaching the heart, usually during exercise or exertion and settles with rest).
The rationale for the sublingual route of administration of GTN.
The sublingual route of administration allowes glyceryl trinitrate to be more rapidly absorbed by the mouth's mucosa.
This action also by-passes the liver to reach the vascula system.
This allows more rapid relief from the pain the patient is experiencing.
This sublingual approach of administration can also be used prophylactically before emotional stress, exposure to cold temperatures or physical exertion.
InterpretÂ the ECG shown in Figure 1 and provide your provisional diagnosis. What are your immediate transport considerations for Leonard?
Whilst it seems Leonard's heart rate has remained consistent (the ECG in figure 1 demonstrates a heart rate of approx. 80 beats per minute) the 12-lead ECG shows that the rate of depolarisation in Leonard's sinus rhythm is not within normal range (Houghton, 1997). The PR interval is very short (40ms, compared to an expected range of 120-200ms). The QRS duration is over 80ms although within normal range and the QT interval is 120ms. This could imply that that repolarisation of the myocardium is not occurring (Hampden, 1992).
Immediate transport considerations would be held at this point so as not to exert any more stress on Leonard. It would be preferred to wait until 5 minutes after the initial dose of GTN and if Leonard's pain has decreased then move him immediately to the hospital. If the pain had not improved then proceed with a second dose of GTN and then move to the hospital (Chockalingam, et al., 2000).
Explain in point form:
The mechanism of action of aspirin relevant to this setting.
Predominantly involves the inhibition of platelet activation and aggravation.
Derives a potential antiplatelet effect by blocking the generation of thromboxane A2, caused by irreversibly inactivating the COX-1 isoenzyme.
The activation of the clotting cascade can play a critical role throughout the onset of acute occlusive vascular events.
Platelets, due to their lack of nuclei, are a perfect target for antithrombotic therapies and aspirin shows immediate and long-term effects on platelets.
The physiological rationale for administering aspirin in this setting (i.e. what is the intended physiological outcome of administering aspirin to a person with Leonard's clinical picture).
In this instance, an improvement of endothelial dysfunction (with the introduction of aspirin, chewed to ensure rapid therapeutic blood levels) may:
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Block the formation of COX-dependent vasoconstrictors (which contribute to endothelial dysfunction in atherosclerosis).
Reduce thrombosis and inhibit the progression of atherosclerosis.
Improve vasodilation and could reduce the inflammatory response in the event of coronary artery disease.
(Lewis, et al., 1983)
Your considerations regarding the suitability/safety of giving Leonard aspirin and the reason(s) for these considerations.
Aspirin may cause bronchospasm in sufferers of asthma.
It may increase the effects of other hypoglycaemic and anticoagulant drugs.
Should Leonard display symptoms of overdose then his legs should be raised from a supine position.
(Yusuf, et al., 2001)
Explain in point form:
The mechanism of action of clopidogrel.
Clopidogrel inhibits ADP-induced platelet aggregation.
Also inhibits collagen and thrombin-induced aggregation.
(Schomig, et al., 1996)
Absorption of clopidogrel by the intestine is followed by convertion by hepatic cytochrome P450 isoenzymes to an active thiol metabolite.
The active metabolite binds to the P2Y12 receptor.
The binding of ADP to the P2Y12 receptor is permanently inhibited.
(Storey, et al., 2001)
The physiological rationale for administering clopidogrel.
Clopidogrel is a thienopyridine which acts as a non-competitive ADP receptor antagonist.
It has antithrombotic effects similar to aspirin.
(Jernberg, et al., 2006)
Clopidogrel is more expensive than aspirin but more effective in improving cardiovascular complications in high risk patients.
(Lev, et al., 2007)
When combined with aspirin, clopidogrel provides addictive reduction in the risk of ischemic events in patients with non-st-elevation ACS.
(Sabatine, et al., 2005)
The implications of administering clopidogrel prior to coronary angiography.
The danger of administering clopidogrel before angiography is that internal bleeding may occur whilst the patient may require coronary artery bypass graft (Angiolillo, 2005).
The clinical situation where it would be inappropriate to administer clopidogrel to Leonard.
If Leonard were allergic to clopidogrel.
If Leonard was experiencing any bleeding (interally, in the form of ulcers, due to stomach problems, etc. or externally).
If Leonard had an underlying kidney or liver disease (or any other condition that may cause bleeding).
(Budaj A, et al., 2002)