The conglomeration of RBCs and platelets held together by the fibrin forms the clot. After the injury to the damaged artery heals, the clot is no longer needed. The body will then destroy the clot by breaking down the fibrin fiber network that binds the blood products together. This action is performed by a chemical called tissue plasminogen activator (TPA), which is secreted by the endothelial cells within normal blood vessels. To be strictly correct, the TPA itself does not break down the clot but instead initiates a cascade in which plasminogen is activated and becomes plasmin, with then acts on the fibrin breaking fibrin down into fibrin degradation products. The fibrin fibers are cleaved, and the clot is destroyed. All thrombolytic agents facilitate the conversion of plasminogen to plasmin and are therefore known as plasminogen activators
Indications for thrombolysis are ST-elevation in two or more contiguous leads on ECG or new left bundle branch block or ST segment depression greater than or equal to 2 mm in V1V2 plus angina lasting 30 minutes to 12 hours that is unrelieved by nitroglycerin.
But there are contraindications for the use of thrombolytic therapy. Absolute contraindications to thrombolytic therapy include:
previous hemorrhagic stroke at any time other strokes or cerebrovascular incidents within one year
Known intracranial neoplasm
Active internal bleeding
Suspected Aortic dissection
Relative contraindications to thrombolyic therapy include:
Severe uncontrolled hypertension on presentation (blood pressure greater than 180/110 mm/Hg)
History of prior cerebrovascular accident or known intercerebral pathology not covered in contraindications
Current use of anticoagulants in therapeutic doses (International Normalized Ration 2-3)
Known bleeding diathesis
Recent trauma (within 2-4 weeks, including head trauma)
Noncompressible venous punctures
Recent internal bleeding
For streptokinase - prior exposure (especially within 2 years) or prior allergic reaction.
Active peptic ulcer
History of chronic hypertension. (American College of Cardiology, 2000)
The major plasminogen activators are:
Streptokinase comes from streptococcus bacterium and carries with it the risk for anaphylaxis. As an indirect plasminogen activator, it must first combine with either plasmin or plasminogen to then deactivate plasminogen. It is the only thrombolytic approved by the FDA for use in peripheral arterial occlusive disease.
Urokinase is derived from cultures of the human kidney cells obtained from newborns that died of natural causes. It is a direct plasminogen activator and has no risk of anaphylaxis. In July, 1999 the FDA indefinitely suspended the distribution of Urokinase because of the theoretical risk of the transmission of human viruses through the kidney cells.
Activase is from recombinant DNA technology and chemically looks identical to the wild type of t-PA which is secreted by the endothelium of normal blood vessels. Today, Activase is the drug of choice as far as thrombolytic therapy for AMI. Retavase is also made from recombinant DNA technology, but differs from wild t-PA on the molecular level.
Evidence shows that nurses well versed in the indications/contraindications of thrombolysis actually reduce the amount of time to treatment. Regarding the matter of nurses administering thrombolysis in order to make access to gold standard treatment matter of fact in the most rapid possible manner, health care professionals must all obtain consent when they examine, care for or treat competent adult patients. There are three overriding professional responsibilities when obtaining consent
The nurse must, when acting in the best interests of the patient, obtain clear consent before any treatment is given.
The nurse must ensure the process of establishing consent is rigorous and demonstrates a clear level of professional responsibility and All discussions and decisions regarding the consent must be documented thoroughly
All patients are considered to be competent unless they demonstrate otherwise but it is important to know that when treatment is deemed necessary to save life and the patient cannot make a decision because they are unconscious the law provides for the provision of care without consent. In all other cases, nurses must ask themselves if the patient can understand the decisions being recommended and make a proper decision with the information which has been provided. It must also be understood that a patient who refuses treatment or makes an unexpected decision when full information has been given is not necessarily incompetent, but an unexpected decision may show the need for further explanation by the professional. Competency is not always easy to determine and the wise professional keeps in mind that informed consent is an ongoing process. Consent must be obtained in a sensitive and understandable way and the patient must be given enough time to make the decision and ask any questions he or she likes.
It should never be assumed that the patient has enough knowledge, even when the most basic of treatment is applied.
If a professional has any doubt that the patient is consenting to treatment, the patient must be questioned if their feelings and decisions are still the same. It is best if the person who is actually doing the treatment obtains consent, and this is why nurses and paraprofessionals must be aware of informed consent laws and guidelines. If a patient feels that the information he or she received was insufficient, it is possible they may take legal action in the form of negligence allegation. It may be necessary for another to obtain consent for treatment ordered under the name of a specialist who is advising on a treatment by the phone, for example.
The ethical guidelines surrounding informed consent must be considered separately, as simply making an "ethical" decision will be different to each person's definition. Ethics surrounding medical care may be governed by theistic or atheistic guidelines, depending of the professional's reference. The basic principles which override any personal ethical guidelines are that care must include a respect for autonomy, nonmalfisance, beneficence and justice. Threshold ethical elements include competence to make an informed decision, as previously stated but also the patient's sense of voluntarily adhering to the prescribed course of treatment. Consent serves both a clinical and legal purpose. Ethically, the standard of disclosure to the patient must be based on what the patient would reasonably need to know in order to make a decision rather than that which the professional feels he or she wants to disclose. This standard is often used in legal proceedings in testing whether informed consent was properly done (Cohen, Kessell, 1987).
Barriers to the effective obtaining of informed consent do not always come because the patient is incompetent, speaks a foreign language, or has some other complicating disability. A study by the University of Washington showed that the role of communication in informed consent was especially important. It is not enough that the patient know the rationale for proposed therapy. It was shown that quite often there is incongruence in the shared understanding of benefit of therapy, possible risk and proposed alternatives (Wu and Perlman, 1988). Increasingly, a number of districts in the United States use the criteria of what a "reasonable man" would want as a basis for medical informed consent. Key ideas that appear to shape patients participation in medical therapy include fear of the condition, a trust in current medical technologies and a patient's desire to take responsibility for their own health. As such these issues must be addressed for a complete and comprehensive informed consent to be given, even in time-limited circumstances such as these.
It has been scientifically and clinically proven that patients experiencing acute myocardial infarction benefit from the early administration of thrombolytic therapy.
Clinical guidelines and protocols exist to allow rapid diagnosis of AMI. The challenge exists, however, that multidisciplinary providers ensure that patients are given true informed consent for all procedures, from administration of medication to invasive procedures. The setting can be chaotic, but it is imperative although not impossible, that effective communication exist between patients and providers. It is possible that with well trained pre- and in hospital staffing, these treatment guidelines can be met. All levels and disciplines of care must be adequately educated, not only on proper clinical procedure but in the administration of effective and reasonable communication on the benefits, adverse effects, indications and outcomes of life-sustaining therapies, and patients must be active participants in the provision of quality health care.
American College of Cardiology Guidelines: The management of patients with Acute Myocardial Infarction: A report of the American College of Cardiology and the American Heart Association Task Force on Practice Guidelines, 2000, Bethesda, MD
Birkhead, J. (1999) Trends in the Provision of thrombolytic treatment between 1993 and 1997, Heart, 82:438-442
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Brownwald, H. ed. Harrison's Textbook of Internal Medicine, 15th edition 2003
Capwell, S, McMurray, J, (2000). Chest pain: please admit British Medical Journal, 320:951-952
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