The nurse is caring for a patient admitted with severe sepsis.
Vital signs assessed by the nurse include blood pressure 80/50 mm Hg, heart rate 120 beats/min, respirations 28/min and oral temperature of 102 degrees F. Assuming physician orders, which intervention should the nurse carry out first?

Choice A rationale

Sinus tachycardia is characterized by a normal cardiac conduction pathway originating in the sinoatrial node but at a rate exceeding 100 beats per minute. While stress or pain can cause tachycardia, premature ventricular contractions are ectopic beats originating from the ventricles, bypassing the normal atrial conduction system. There is no direct electrophysiological mechanism where ventricular ectopy converts the heart back into a rapid but otherwise normal sinus rhythm originating from the atria.

Choice B rationale

Rapid atrial flutter is a supraventricular tachycardia caused by a macro-reentrant circuit within the atria, typically producing a characteristic sawtooth pattern on an EKG. Premature ventricular contractions occur below the Bundle of His and do not typically trigger atrial re-entrant circuits. While both involve irritability of the cardiac tissue, the pathology of atrial flutter is localized to the upper chambers, whereas frequent ventricular ectopy primarily predisposes the heart to more lethal ventricular-based arrhythmias.

Choice C rationale

Atrioventricular junctional rhythm occurs when the AV node takes over as the primary pacemaker of the heart, usually at a rate of 40 to 60 beats per minute. This typically happens if the sinoatrial node fails or is suppressed. Frequent premature ventricular contractions signify increased ventricular excitability rather than a failure of the upper pacemakers. Therefore, the progression of frequent ventricular ectopy is usually toward faster, more chaotic ventricular rhythms rather than a slower junctional escape rhythm.

Choice D rationale

Ventricular tachycardia is defined as three or more consecutive premature ventricular contractions at a rate greater than 100 beats per minute. Frequent ventricular ectopy indicates significant myocardial irritability. When a premature contraction falls during the vulnerable period of the T-wave, known as the R-on-T phenomenon, it can trigger a sustained run of ventricular tachycardia. This rhythm is life-threatening because it severely reduces cardiac output due to decreased diastolic filling time and loss of atrial kick.

Choice A rationale

Axonal shearing typically occurs during rapid acceleration or deceleration injuries, such as traumatic brain injury, rather than as a primary consequence of generalized cerebral edema. While displacement can occur, shearing involves the stretching of nerve fibers due to rotational forces. In the context of increased intracranial pressure from edema, the mechanical compression of the brain against the rigid skull is a more immediate cause of damage than the tearing of axons themselves.

Choice B rationale

Increased intracranial pressure from cerebral edema leads to the compression of thin-walled cerebral blood vessels. This mechanical obstruction reduces cerebral blood flow, causing tissue hypoxia and eventual ischemia. As pressure rises, the cerebral perfusion pressure decreases, preventing oxygenated blood from reaching neuronal tissues. This lack of oxygen and nutrients leads to cellular dysfunction, metabolic failure, and irreversible brain damage if the pressure is not relieved to restore adequate circulation to the brain.

Choice C rationale

Decreased cerebral perfusion can indeed result from systemic hypotension or significant blood loss, but the question specifically asks for damage secondary to cerebral edema. Edema increases internal pressure within the skull, which opposes arterial blood flow regardless of systemic blood pressure. While hypotension would exacerbate the situation, the primary mechanism of injury in edema is the localized intracranial resistance to flow, not necessarily a drop in the systemic blood volume or pressure.

Choice D rationale

Myelin degeneration is a characteristic of chronic demyelinating diseases or secondary processes following long-term nerve injury, rather than an acute mechanism of brain damage from edema-induced pressure. While inflammatory enzymes are released during tissue necrosis, they are a byproduct of the ischemic process rather than the primary driver of the initial brain damage. The mechanical and vascular compromises are the urgent factors in the setting of rapidly increasing intracranial pressure.