What causes increased systolic blood pressure in a person with increased intracranial pressure?
Increased pressure on cranial nerve III.
Stretching of the dura and blood vessels.
Vasoconstriction from cerebral ischemia.
Excess swelling of the person's optic disc.
The Correct Answer is C
Choice A rationale
Increased pressure on cranial nerve III, the oculomotor nerve, typically results in pupillary changes rather than a direct increase in systolic blood pressure. When this nerve is compressed, usually by a herniating temporal lobe, the pupil on the affected side becomes dilated and non-reactive to light. While this is a critical sign of increasing intracranial pressure, it is a localized neurological sign and not the primary driver of the systemic vasomotor changes seen in Cushing's triad.
Choice B rationale
Stretching of the dura and blood vessels is a common cause of the headache associated with increased intracranial pressure. The dura mater is highly sensitive to pain and displacement. While this stretching triggers nociceptors and causes significant discomfort, it does not directly cause the systemic physiological response of increasing the systolic blood pressure. The hypertensive response is a compensatory mechanism designed to maintain blood flow to the brain, rather than a simple pain reflex from dural irritation.
Choice C rationale
Vasoconstriction from cerebral ischemia is the catalyst for increased systolic blood pressure, part of the Cushing reflex. When intracranial pressure rises, it compresses cerebral blood vessels, reducing blood flow and causing ischemia. The brain's vasomotor center responds by triggering the sympathetic nervous system to increase systemic blood pressure. This is an attempt to overcome the high intracranial pressure and maintain cerebral perfusion. This results in a widened pulse pressure where the systolic pressure rises significantly.
Choice D rationale
Excess swelling of the person's optic disc is known as papilledema. This occurs because the high pressure within the cranium is transmitted through the subarachnoid space to the optic nerve sheath. While papilledema is a definitive physical finding of chronic or significant intracranial pressure, it is a visual and anatomical consequence. It does not cause the systemic cardiovascular change of hypertension. The rise in blood pressure is a hemodynamic compensation for poor cerebral oxygenation, not a result of disc swelling.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
Fibromyalgia is a chronic disorder characterized by widespread musculoskeletal pain, fatigue, and localized tenderness. It is scientifically understood as a disorder of pain processing, where the central nervous system becomes hypersensitive to stimuli. This results in the over-stimulation of pain, pressure, and temperature receptors, a phenomenon known as central sensitization. Patients experience significant discomfort because the brain amplifies normal sensory signals, making non-painful stimuli feel painful or uncomfortable across the body.
Choice B rationale
Photophobia refers specifically to an abnormal sensitivity or intolerance to light. It is often a symptom of other conditions, such as migraines, meningitis, or corneal inflammation, rather than a primary condition involving generalized over-stimulation of pressure and temperature receptors. While it causes discomfort, it is limited to the visual system and does not involve the widespread tactile or thermal receptor over-stimulation that defines the generalized pain and discomfort associated with systemic sensory processing disorders like fibromyalgia.
Choice C rationale
Phonophobia is defined as a persistent and abnormal fear of or sensitivity to sound. Similar to photophobia, it is frequently a secondary symptom of neurological conditions like migraines or certain types of seizures. It involves the auditory system's response to acoustic stimuli rather than the generalized over-stimulation of somatic receptors for pain, pressure, and temperature. Consequently, it does not explain a condition of significant physical discomfort arising from the broader range of sensory receptors mentioned.
Choice D rationale
Retinitis is an inflammation of the retina that can lead to permanent vision loss if left untreated. It is an ocular inflammatory process caused by infections, such as cytomegalovirus, or autoimmune diseases. While it affects the sensory function of the eyes and can lead to blindness, it does not involve the systemic over-stimulation of pain, pressure, or temperature receptors. Its pathophysiology is localized to the eye tissue and does not cause generalized physical discomfort through peripheral receptor hypersensitivity.
Correct Answer is B
Explanation
Choice A rationale
Metabolic alkalosis occurs when the pH is above 7.45 and the bicarbonate level is above 26 mEq/L. This condition is typically caused by a loss of hydrogen ions or an excess of bicarbonate. In this clinical scenario, the pH is 7.30 and the bicarbonate is 24 mEq/L, which is within the normal range of 22 to 28 mEq/L. Therefore, the imbalance cannot be classified as metabolic alkalosis based on these laboratory values.
Choice B rationale
Respiratory acidosis is characterized by a pH below 7.35 and a PaCO2 above 45 mmHg. The normal range for pH is 7.35 to 7.45, and for PaCO2 is 35 to 45 mmHg. In this case, the pH of 7.30 indicates acidemia, and the elevated PaCO2 of 50 mmHg identifies the respiratory system as the cause. The normal bicarbonate level suggests that renal compensation has not yet occurred, confirming an acute respiratory acid-base imbalance.
Choice C rationale
Respiratory alkalosis involves a pH greater than 7.45 and a PaCO2 less than 35 mmHg. This state is generally caused by hyperventilation, which leads to the excessive elimination of carbon dioxide from the lungs. Since the patient in this scenario has a low pH of 7.30 and a high carbon dioxide level of 50 mmHg, the laboratory data is the direct opposite of what is required for a diagnosis of respiratory alkalosis.
Choice D rationale
Metabolic acidosis is defined by a pH below 7.35 and a bicarbonate level below 22 mEq/L. While the pH of 7.30 in this scenario indicates acidosis, the bicarbonate level of 24 mEq/L is perfectly within the standard reference range of 22 to 28 mEq/L. Because the primary abnormality is found in the PaCO2 level rather than the bicarbonate level, the source of the acid-base disturbance is respiratory and not metabolic in origin.
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