What manifestation(s) occur when a person has diabetes insipidus? Select all that apply.
Increased thirst.
Decreased heart rate.
Decreased blood pressure.
Increased glucose level.
Decreased urine output.
Correct Answer : A,C
Choice A rationale
Diabetes insipidus is characterized by a deficiency in antidiuretic hormone or a lack of renal response to it. This leads to the excretion of large volumes of dilute urine, often exceeding 3 liters per day. The resulting intracellular and extracellular dehydration triggers the osmoreceptors in the hypothalamus, creating an intense sensation of polydipsia or increased thirst as the body attempts to replace the massive fluid losses.
Choice B rationale
A decreased heart rate is not expected in this condition. Instead, as the patient loses significant amounts of fluid through polyuria, the intravascular volume drops, leading to hypovolemia. The body compensates for this decreased stroke volume by activating the sympathetic nervous system, which typically results in tachycardia, or an increased heart rate, to maintain cardiac output. A decreased heart rate would suggest a different underlying pathology or a late-stage shock.
Choice C rationale
Decreased blood pressure is a direct consequence of the massive fluid loss seen in diabetes insipidus. Significant diuresis reduces the total circulating blood volume, leading to orthostatic or systemic hypotension. Normal systolic blood pressure is typically 90 to 120 mmHg. When the volume is depleted, the venous return to the heart diminishes, resulting in lower cardiac output and a subsequent drop in the pressure exerted against the arterial walls.
Choice D rationale
Increased glucose levels are characteristic of diabetes mellitus, not diabetes insipidus. Diabetes insipidus involves a primary imbalance of water and electrolytes, specifically related to antidiuretic hormone function at the renal tubules. While both conditions cause polyuria, the urine in diabetes insipidus is dilute and lacks glucose. Normal fasting blood glucose ranges from 70 to 99 mg/dL; this range is generally unaffected by the mechanism of diabetes insipidus.
Choice E rationale
Decreased urine output is the opposite of what occurs in diabetes insipidus. The hallmark of this disorder is polyuria, where the kidneys fail to reabsorb water, resulting in the production of very dilute urine with a low specific gravity, usually less than 1.005. In a healthy state, antidiuretic hormone acts on the collecting ducts to concentrate urine. Without this action, water is wasted, leading to excessively high urine output.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
Restlessness is an early neurological sign of hypoglycemia, which occurs when blood glucose levels drop below approximately 70 mg/dL. As the brain is deprived of its primary fuel source, the body triggers a sympathetic "fight or flight" response. This release of epinephrine leads to irritability, nervousness, and restlessness. Identifying these behavioral changes is crucial for early intervention before the patient's condition progresses to more severe symptoms like confusion, seizures, or a loss of consciousness.
Choice B rationale
Bradycardia is not typically associated with hypoglycemia. Instead, the body usually exhibits tachycardia, or a rapid heart rate, as part of the adrenergic response to low blood sugar. When blood glucose falls, the adrenal glands release epinephrine, which increases the heart rate and force of contraction. A slow heart rate would be an unusual finding and might suggest a different underlying pathology or the use of medications like beta-blockers that mask the symptoms of hypoglycemia.
Choice C rationale
Polyuria, or excessive urination, is a classic symptom of hyperglycemia, not hypoglycemia. In diabetes, when blood glucose is excessively high, the kidneys cannot reabsorb all the filtered sugar, leading to osmotic diuresis where water follows glucose into the urine. In hypoglycemia, the body is trying to conserve energy and fuel, and there is no excess sugar to cause this diuretic effect. Polyuria is part of the "three Ps" of high blood sugar alongside polydipsia and polyphagia.
Choice D rationale
Fruity-smelling breath is a hallmark sign of diabetic ketoacidosis, a complication associated with severe hyperglycemia and insulin deficiency. This scent is caused by the presence of acetone, a byproduct of ketone body production as the body breaks down fat for energy. Hypoglycemia involves a lack of sugar rather than the overproduction of ketones from high sugar levels. Therefore, a fruity odor on the breath would indicate that the patient's blood sugar is dangerously high, not low.
Correct Answer is C
Explanation
Choice A rationale
Increased usable oxygen in the environment, such as that provided by supplemental oxygen therapy or a hyperbaric chamber, generally improves the pressure gradient between the alveoli and the pulmonary capillaries. This enhancement actually facilitates better gas exchange by increasing the amount of oxygen available for diffusion into the blood. Therefore, more oxygen in the environment is a treatment for impaired gas exchange rather than a cause of the impairment itself under normal conditions.
Choice B rationale
Hemoglobin is the primary protein responsible for the transport of oxygen from the lungs to the peripheral tissues. An increased amount of functional hemoglobin, provided the cardiovascular system is intact, typically enhances the oxygen-carrying capacity of the blood. This improves the overall efficiency of gas delivery to cells. Impaired gas exchange is more likely to occur when hemoglobin levels are low, such as in severe anemia, where the blood cannot carry enough oxygen.
Choice C rationale
An increased concentration of carbon dioxide in the ambient environment reduces the partial pressure gradient necessary for carbon dioxide to diffuse out of the blood and into the alveoli. This can lead to hypercapnia and respiratory acidosis. Furthermore, if the environment is saturated with carbon dioxide, it often displaces available oxygen, leading to hypoxia. High levels of environmental carbon dioxide actively interfere with the body's ability to maintain normal blood gas homeostasis.
Choice D rationale
The total surface area available for gas exchange is determined by the number of healthy, functioning alveoli. An increased number of alveoli, or maintaining the integrity of existing ones, ensures a larger area for the diffusion of gases across the alveolar-capillary membrane. Conditions that decrease the number of functioning alveoli, such as emphysema or pulmonary fibrosis, are what lead to impaired gas exchange. Having more alveoli would naturally support better respiratory function and efficiency.
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