CCRN exam prep — 2,093 practice questions, every answer explained

B is correct.Normal central venous pressure ranges from 2 to 6 mm Hg (or 3 to 8 cm H2O). A central venous pressure of 14 mm Hg represents marked elevation, which indicates right ventricular failure or severe intravascular volume overload, as backpressure accumulates in the right atrium and systemic venous circulation. In the setting of hypotension, tachycardia, and oliguria following cardiac surgery, an elevated central venous pressure strongly points toward right ventricular failure, right ventricular infarction, or cardiac tamponade restricting right-sided filling. Systemic arterial vasodilation secondary to early septic shock produces low or decreased central venous pressure due to venous pooling, reduced venous return, and relative hypovolemia. Severe absolute hypovolemia caused by uncorrected surgical hemorrhage produces a significantly low central venous pressure below 2 mm Hg due to inadequate circulating intravascular volume. Isolated left ventricular hypoperfusion with normal right chambers would present with normal central venous pressure alongside elevated pulmonary artery occlusion pressure. Recognizing hemodynamic trends enables the critical care nurse to guide targeted fluid and inotropic therapies.

C is correct.Clinical decision-making capacity is decision-specific and time-specific; having a psychiatric diagnosis, such as major depressive disorder, does not automatically eliminate a patient's legal or ethical right to refuse medical therapies. If a patient is alert, comprehends the clinical situation, grasps the risks and consequences of treatment refusal (including fatal outcomes), and can communicate a reasoned choice, they possess decision-making capacity. Claiming that a psychiatric diagnosis automatically invalidates medical consent capacity is a widespread clinical misconception; mental illness impairs capacity only when active psychiatric symptoms distort reality and impair understanding of the immediate clinical decision. Stating that surrogate decision makers must approve all care refusals is incorrect because surrogate decision-makers are consulted only when a patient lacks clinical capacity or has been formally adjudicated incompetent. The assertion that involuntary psychiatric admission immediately strips legal patient autonomy is erroneous because civil commitment does not strip individuals of their constitutional right to refuse medical interventions unless specific legal criteria for emergency involuntary treatment or guardianship are met.

C is correct.Guidelines from the American Academy of Neurology mandate that all potential confounding conditions, including severe electrolyte, acid-base, and endocrine derangements, must be corrected before undertaking a clinical brain-death evaluation. Severe hyponatremia (sodium 116 mEq/L), hypokalemia (potassium 2.8 mEq/L), and severe acidemia (pH 7.10) can profoundly suppress neurologic function, depress central brainstem reflexes, and induce reversible coma that mimics neurologic death. Proceeding with apnea testing while infusing sodium bicarbonate is unsafe and invalid; apnea testing requires baseline biochemical and metabolic stability because severe acidosis and electrolyte imbalances provoke lethal cardiac arrhythmias during hypercapnic challenge. Requesting urgent four-vessel cerebral angiography or performing immediate radionuclide cerebral perfusion imaging without biochemical correction is premature; ancillary studies are indicated when clinical examination cannot be completed or is inconclusive, but they do not eliminate the prerequisite of correcting severe metabolic derangements. The medical team must normalize sodium, potassium, and acid-base status to ensure that observed neurologic unresponsiveness is truly irreversible cessation of brain function.

D is correct.The clinical scenario describes malignant hyperthermia (MH), a rare, life-threatening pharmacogenetic hypermetabolic crisis triggered by volatile inhalational anesthetics (such as sevoflurane, desflurane, or isoflurane) or the depolarizing neuromuscular blocker succinylcholine. Defective ryanodine receptors (RYR1) in skeletal muscle sarcoplasmic reticulum cause uncontrolled calcium release, leading to sustained muscle contractions, hypermetabolism, hypercarbia, metabolic acidosis, rhabdomyolysis, and hyperthermia. Intravenous dantrolene sodium is the specific, life-saving pharmacologic antidote for MH. Dantrolene directly inhibits ryanodine receptor calcium channels, preventing calcium release from the sarcoplasmic reticulum into the myoplasm and halting the hypermetabolic cascade. Intravenous sodium nitroprusside is a potent vasodilator used for hypertensive crises; it does not address the underlying uncontrolled intracellular calcium release. Intravenous vecuronium bromide is a non-depolarizing paralytic that acts at the motor endplate, which cannot overcome intrinsic calcium cycling within the sarcoplasm. Dexmedetomidine is an alpha-2 adrenergic agonist used for sedation and analgesia without antidote properties for MH. Triggering agents must be immediately discontinued alongside rapid dantrolene administration and active cooling.

D is correct.The primary pathophysiologic hallmark of pulmonary emphysema is the irreversible destruction of alveolar septa and elastic recoil. Exposure to cigarette smoke attracts inflammatory cells that release proteolytic enzymes, predominantly neutrophil elastase, which overwhelm endogenous antiproteases like alpha-1 antitrypsin. This enzymatic degradation permanently destroys elastin fibers within alveolar septa, leading to enlarged airspaces, loss of pulmonary elastic recoil, and dynamic expiratory airway collapse that traps air and severely elevates residual volume. In contrast, hypertrophy of bronchial submucosal glands with mucus hypersecretion describes chronic bronchitis, which primarily causes luminal narrowing rather than parenchymal destruction. Extensive smooth muscle hypertrophy surrounding the conducting terminal bronchioles represents structural airway remodeling characteristic of chronic, severe asthma. Acute inflammatory exudate filling alveoli and peripheral terminal airways describes acute bacterial or viral pneumonia, which causes consolidation and intrapulmonary shunting rather than permanent loss of elastic recoil. Understanding this destructive pathophysiology is essential for the critical care nurse managing hyperinflation, prolonged expiration, and auto-PEEP during mechanical ventilation.