McKenna's Pharmacology for Nursing, 2e

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P A R T 8  Drugs acting on the cardiovascular system

Drug therapy across the lifespan

BOX 48.1

Drugs affecting blood coagulation CHILDREN

It is prudent to advise any person using one of these drugs in the home setting to carry or wear a MedicAlert notification in case of emergency. The person also needs to understand the importance of regular, periodic blood tests to evaluate the effects of the drug. PREGNANCY AND BREASTFEEDING Because of the many risks associated with increased bleeding or increased blood clotting during pregnancy, these drugs should not be used during pregnancy unless the benefit to the mother clearly outweighs the potential risk to the fetus and to the mother at delivery. Risks of altered blood clotting in the neonate make these drugs generally inadvisable for use during breastfeeding. OLDER ADULTS Older adults may have many underlying medical conditions that require the need for drugs that alter blood clotting (e.g. coronary artery disease, cerebrovascular accident, peripheral vascular disease, transient ischaemic attacks). Statistically, older adults also take more medications, making them more likely to encounter drug–drug interactions associated with these drugs.The older adult is also more likely to have impaired liver and kidney function, conditions that can alter the metabolism and excretion of these drugs. The older adult should be carefully evaluated for liver and kidney function, use of other medications, and ability to follow through with regular blood testing and medical evaluation before therapy begins.Therapy should be started at the lowest possible level and adjusted accordingly after the person’s response has been noted. Careful attention needs to be given to the person’s total drug regimen. Starting, stopping or changing the dose of another drug may alter the body’s metabolism of the drug that is being used to affect coagulation, leading to increased risk of bleeding or ineffective anticoagulation.

Little research is available on the use of anticoagulants in children. If they are used, the child needs to be monitored very carefully to avoid excessive bleeding related to drug interactions or alterations in gastrointestinal or liver function. People who interact with the child need to understand the importance of preventing injuries and providing safety precautions.They should be aware of what to do if the child is injured and begins to bleed. If heparin is used, the dose should be carefully calculated based on weight and age and checked by another person before being administered. Warfarin is used with children who are to undergo cardiac surgery. Again, the dose must be determined based on weight and age, and the child should be monitored closely. The safety of low-molecular-weight heparins has not been established in children. At this time, there are no indications for the use of antiplatelet or thrombolytic drugs with children. ADULTS Adults receiving these drugs need to be instructed in ways to prevent injury—such as using an electric razor instead of a straight razor, using a soft-bristled toothbrush to protect the gums, and avoiding contact sports—and instructed in what to do if bleeding does occur (apply constant, firm pressure and contact a healthcare provider). They should receive a written list of signs of bleeding to watch for and to report to their healthcare provider. Because so many drugs and alternative therapies are known to interact with these agents, it is very important that these people be urged to report the use of this drug to any other healthcare provider and to consult with one before using any over-the-counter drugs or alternative therapies.

Blood vessel injury

Blood vessel constricts

Loss of blood into tissues

Intrinsic pathway to clot formation

Extrinsic pathway to clot formation

↑ Extravascular pressure

Platelet adhesion to wall of injured vessel and platelet aggregation

Blood clot

↓ Blood flow at site of injury

Compression of injured blood vessel

Platelet plug

FIGURE 48.1  Process of blood coagulation.

↓ Blood loss at site of injury