What causes dilutional hyponatremia?
Excessive sweating.
Excessive water intake.
Vomiting.
Diarrhea
The Correct Answer is B
Choice B rationale
Dilutional hyponatremia occurs when there is a relative excess of total body water compared to the amount of sodium, leading to a serum sodium level below the normal range of 135 to 145 mEq/L. Excessive water intake, whether through oral ingestion or the administration of hypotonic intravenous fluids, expands the extracellular fluid volume and dilutes the sodium concentration. This is a primary mechanism where the sodium itself may not be lost, but its concentration drops significantly.
Choice A rationale
Excessive sweating, or diaphoresis, results in the loss of both water and electrolytes, including sodium. While sweat is hypotonic, meaning more water is lost than salt, the primary result of extreme sweating without replacement is usually dehydration and potentially hypernatremia. If a person drinks massive amounts of pure water to replace the sweat without replacing the lost salt, they could develop hyponatremia, but the sweating itself is not a dilutional process of adding water.
Choice C rationale
Vomiting causes the direct loss of sodium-rich gastric secretions from the body. This is considered a depletional hyponatremia because the sodium is physically removed from the system. While the body may retain water in an attempt to maintain blood volume through the release of antidiuretic hormone, the initial and primary cause of the low sodium is the actual loss of the electrolyte, rather than the simple dilution of existing sodium by an intake of excess water.
Choice D rationale
Diarrhea, similar to vomiting, involves the physical excretion of sodium and other electrolytes from the lower gastrointestinal tract. This leads to a depletional state where the total body sodium is reduced. While it can lead to hyponatremia if the fluid loss is replaced only with free water, the mechanism of diarrhea itself is the loss of solute. Dilutional hyponatremia specifically refers to the scenario where an increase in water volume is the driving force behind the low concentration.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
Heart failure is generally a consequence or a result of coronary artery disease rather than its cause. When coronary arteries are narrowed or blocked, the heart muscle does not receive enough oxygen, leading to damage and weakened pumping ability over time. While heart failure involves complex physiological changes, the primary drivers of the arterial damage seen in CAD are metabolic and hemodynamic factors like lipid levels and high blood pressure, not the failure of the pump.
Choice B rationale
A pulmonary embolus is a blockage in one of the pulmonary arteries in the lungs, usually caused by blood clots that travel from the legs. This is a critical condition affecting the pulmonary circulation and right side of the heart. While it causes acute strain on the heart, it does not cause the chronic atherosclerotic changes and plaque buildup within the coronary arteries that define coronary artery disease. These are two distinct vascular pathologies with different origins.
Choice C rationale
Anemia is a condition where the blood lacks enough healthy red blood cells or hemoglobin to carry adequate oxygen to the body's tissues. While anemia can exacerbate the symptoms of coronary artery disease by further reducing oxygen delivery to a struggling heart, it does not cause the structural narrowing or plaque formation in the arteries. CAD is an inflammatory and lipid-driven process, whereas anemia is a hematological issue concerning the oxygen-carrying capacity of the blood.
Choice D rationale
Hypertension is a major, direct cause and risk factor for coronary artery disease. High blood pressure creates chronic mechanical stress and shear force against the arterial walls, leading to endothelial injury. This damage allows cholesterol and other lipids to enter the vessel wall, initiating the formation of atherosclerotic plaques. Over time, these plaques narrow the arteries, restricting blood flow to the myocardium. Managing blood pressure is a primary strategy in preventing the development and progression of CAD.
Correct Answer is C
Explanation
Choice A rationale
Stroke volume is the volume of blood pumped from the left ventricle per beat. It is calculated as the difference between end-diastolic volume and end-systolic volume. While it is a critical measure of cardiac function, it represents the output of the heart rather than the resistance the heart must work against. Stroke volume is influenced by contractility, preload, and afterload, but it is not the term for the resistance itself encountered during the ejection phase of the cardiac cycle.
Choice B rationale
Cardiac reserve refers to the difference between the rate at which the heart pumps blood at any given time and its maximum capacity for pumping blood. it is a measure of the heart's ability to increase its output during physical exertion or stress. It indicates the health and functional flexibility of the cardiovascular system. It does not describe the specific physical resistance or pressure that the ventricles must overcome to move blood into the aorta or pulmonary artery.
Choice C rationale
Afterload is the technical term for the resistance or pressure that the ventricles must pump against to eject blood during systole. It is primarily determined by systemic vascular resistance and the pressure within the large arteries. Scientifically, if the afterload increases, such as in hypertension or aortic stenosis, the heart must work harder to open the semilunar valves and push blood out, which can eventually lead to ventricular hypertrophy and heart failure due to the chronic workload.
Choice D rationale
Preload is the initial stretching of the cardiac myocytes prior to contraction. It is related to ventricular filling and is determined by the end-diastolic volume. According to the Frank-Starling law, an increase in preload leads to a stronger contraction, up to a certain point. Preload represents the volume of blood entering the heart and the resulting "stretch" on the muscle fibers, whereas afterload represents the "squeeze" or force needed to push that blood out.
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