2 Clinical Judgement: Foundations of Pharmacology and Pathophysiology

I: Chapter Overview of Clinical Judgement Connection

Clinical judgment is the accumulation of knowledge and skill over time that contributes to the nurse’s ability to analyze and synthesize the patient’s presentation. Objective and subjective data guide the nurse’s clinical decision-making and provide evidence-based nursing interventions to help improve patient outcomes. This chapter will also introduce the clinical judgment management model (CJMM), the nursing process, and how it relates to safety and quality with medication administration, pharmacokinetics, and pharmacodynamics.

II. Pharmacokinetics

Pharmacokinetics is drug movement through the body to achieve its required action. This phase involves four essential processes: absorption, distribution, metabolism, and excretion.

1. Absorption: Medications come in various forms. The first stage of pharmacokinetics is known as absorption. Absorption occurs after drugs enter the body and travel from the administration site into circulation. Medications can enter the body through various routes of administration. Standard routes to administer medications include the following examples:

2. Distribution: The second step of pharmacokinetics involves drug distribution. Distribution is the process by which medication is dispersed throughout the body via the bloodstream. Once a drug enters systemic circulation by absorption or direct administration, it must be distributed into interstitial and intracellular fluids to reach the target cells. A drug’s distribution throughout the body depends on common factors such as blood flow, plasma protein binding, lipid solubility, blood-brain, and placental barriers. Other factors include capillary permeability, differences between blood/tissue, and volume of distribution.

Distribution of medication can also cause unintended adverse effects or side effects. Drugs are designed to primarily cause one effect, meaning they bind more strongly to one specific receptor site and predictably cause or block an action.  However, side effects can occur when the drug binds to other sites in addition to the target tissue, causing secondary side effects.  These side effects can range from tolerable to unacceptable, resulting in the medication’s discontinuation. For example, a person might take the pain reliever ibuprofen (Advil) to treat a sore leg muscle, and the pain may be subsequently relieved, but there may also be stomach irritation as a side effect that may cause the person to stop taking Ibuprofen.

3. Metabolism: The third step is drug metabolism (biotransformation). In this phase, drugs are chemically altered by the body into a form that allows them to be excreted from the body. The breakdown of a drug molecule usually involves two steps, primarily in the body’s chemical processing plant: the liver. Everything that enters the bloodstream—whether swallowed, injected, inhaled, absorbed through the skin, or produced by the body itself—is carried to this largest internal organ.

4. Excretion: The final process in pharmacokinetics is excretion. The body has absorbed, distributed, and metabolized the medication molecules and will eliminate it from the body. The kidney often filters the remaining parent drugs and metabolites in the bloodstream, where a portion undergoes reabsorption back into the bloodstream, and the remainder is excreted in the urine. The liver also excretes byproducts and waste into the bile. Another potential route of excretion is the lungs.

Kidneys

The most common route of excretion is the kidney.  As the kidneys filter blood, most drug byproducts and waste are excreted in the urine. The excretion rate can be estimated by considering several factors:  age, weight, biological sex, and kidney function.  Kidney function is measured by lab values such as serum creatinine, glomerular filtration rate (GFR), and creatinine clearance.  If a patient’s kidney function is decreased, then their ability to excrete medication is affected, and drug dosages must be altered for safe administration.

Liver

As the liver filters blood, some drugs and their metabolites are transported by the hepatocytes (liver cells) to bile. Bile moves through the bile ducts to the gallbladder and then onto the small intestine. During this process, some drugs may be partially absorbed by the intestine back into the bloodstream.  Other drugs are biotransformed (metabolized) by intestinal bacteria and reabsorbed. Unabsorbed drugs and byproducts/metabolites are excreted via the feces. If a patient is experiencing decreased liver function, their ability to excrete medication is affected, and drug dosages must be reduced. Lab studies used to estimate liver function are called liver function tests and include measurement of the Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) enzymes that the body releases in response to damage or disease.

III. Pharmacodynamics

In the pharmacodynamic phases, chemical reactions occur that produce the drugs’ effect on the body and the mechanism of action. When considering how the cells of the body respond to medications, it is important to remember that the majority of drugs bind to specific receptors on the surface or interior of cells. However, many other cellular components and non-specific sites can serve as receptor sites where drugs can bind to create a response. Drug responses can be desirable and undesirable. For example, if a patient is administered diphenhydramine (Benadryl) for itching related to contact dermatitis (triggered by an allergic reaction), the desired effect will be that the itching stops, but the undesired effect will be drowsiness and/or sedation that will result from depression of the central nervous system (CNS).

IV. Pathophysiology and Medication Administration

Pathophysiology and pharmacology are interrelated and play a key role in nursing practice. While pathophysiology explains a disease process’s functional and chemical properties, pharmacology connects drugs’ effects on the body. The knowledge that you will gain from pathophysiology and pharmacology will enable you to understand how your patient’s treatment works, their disease process, side effects,  and how to safely and effectively monitor and manage their condition. Knowledge of pathophysiology and pharmacology is also needed for you to educate your patient about their condition and treatment in a simple way that they can understand. You will also be in a position to discuss your patient effectively with members of a multi-professional team. It is important to understand that knowing the normal function of body systems (respiratory, cardiovascular, gastrointestinal, central nervous system, endocrine, etc.) can greatly help you promptly identify and understand when an organ system fails or is functioning abnormally.

A disease process can affect a patient’s clinical presentation. Patients can present in a healthcare facility with a variety of clinical signs and symptoms, and in order for you to get a full picture of a disease or condition, you must understand which body system is affected, the clinical manifestations that your patient will present with and how a particular drug will work to fix the dysfunction. Part of your role as a nurse will be to deliver person-centered care that is holistic and individualized. Applying pathophysiology and pharmacology will assist you with your clinical decision-making, strengthen your assessment of your patients, and help you use a safe and effective systematic process that is evidence-based to properly plan your care and interventions and to accurately evaluate your patient care outcomes. In this book, you will learn conceptually about particular organ systems, disease processes, and the classifications of medications that are used for management.

V. Improving Medication Safety for Nurses

• Establish safe work environments for medication preparation, administration, and documentation. Reduce distractions and provide appropriate lighting, for instance.
• Maintain a culture of rigorous commitment to principles of safety in medication administration (for instance, the five rights of medication safety and cross-checks with colleagues, where appropriate).
• Remove barriers and facilitate the involvement of patient surrogates in checking the administration and monitoring the medication effects.
• Foster a commitment to patients’ rights as co-consumers of their care.
• Develop aids for patients or their surrogates to support self-management of medications.
• Enhance communication skills and team training to be prepared and confident in questioning medication orders and evaluating patient responses to drugs.
• Actively advocate for the development, testing, and safe implementation of electronic health records.
• Work to improve systems that address “near misses” in the work environment.
• Realize they are part of a system and do their part to evaluate the efficacy of new safety systems and technology.
• Contribute to the development and implementation of error reporting systems and support a culture that values accurate medication error reporting.

Key Steps for Ensuring Medication Safety:

Medication administration is an essential task nurses perform while providing patient care. However, safe medication administration is more than just a nursing task; it is a process involving several members of the health care team, as well as legal, ethical, social, and cultural issues. The primary focus of effective medication administration by all health professionals is patient safety. Although many measures have been put into place over the past few decades to promote improved patient safety, medication errors, and adverse effects continue to be a common event.

VI. Legal and Ethical Regulations

There are many federal and state laws, as well as national guidelines, that have been established to protect public health and safety. This section will explain how the Food and Drug Administration (FDA), Drug Enforcement Administration (DEA), Joint Commission, Centers for Medicare and Medicaid Services (CMS), a State’s Nurse Practice Act, State Boards of Nursing, and state legislatures protect the consumer from medication harm. To protect the public the U.S. Food and Drug Administration (FDA) is responsible for protecting public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, and medical devices and by protecting our nation’s food supply, cosmetics, and products that emit radiation.^[1] The FDA protects public health regarding medications by enforcing an official drug approval process based on evidence-based research, issuing Black Box Warnings for medications with severe adverse reactions, and regulating over-the-counter (OTC) medications.

American consumers benefit from having access to the safest and most advanced pharmaceutical system in the world. The leading consumer watchdog in this system is the FDA’s Center for Drug Evaluation and Research (CDER).

The center’s best-known job is evaluating new drugs before they can be sold. CDER’s evaluation not only prevents quackery but also provides doctors and patients with the information they need to use medicines wisely. The center ensures that drugs, both brand-name and generic, work correctly and that their health benefits outweigh their known risks.

Drug companies conduct extensive research and work to develop and test a drug. The company then sends CDER the evidence from these tests to prove the drug is safe and effective for its intended use. Before the drug is approved as safe for use in the United States, a team of CDER physicians, statisticians, chemists, pharmacologists, and other scientists reviews the company’s data and proposed labeling. If this independent and unbiased review establishes a drug’s health benefits outweigh its known risks, the drug is approved for sale. Before a drug can be tested in people, the drug company or sponsor performs laboratory and animal tests to discover how the drug works and whether it’s likely to be safe and work well in humans. Next, a series of clinical trials involving volunteers is conducted to determine whether the drug is safe to treat a disease and whether it provides a real health benefit.

FDA approval of a drug means that CDER has reviewed data on its effects, and the drug is determined to provide benefits that outweigh its known and potential risks for the intended population. Although many of the FDA’s risk-benefit assessments and decisions are straightforward, sometimes the benefits and risks are uncertain and complex to interpret or predict. The agency and the drug maker may reach different conclusions after analyzing the same data, or there may be differences of opinion among members of the FDA’s review team. As a science-led organization, the FDA uses scientific and technological information to make decisions through a deliberative process.