An adult patient with third-degree AV block is admitted to the cardiac care unit and placed on continuous cardiac monitoring.
What rhythm characteristic will the ECG most likely show?
PP interval and RR interval are irregular.
Fewer QRS complexes than P waves.
PP interval is equal to RR interval.
PR interval is constant.
The Correct Answer is B
Choice A rationale
In a third-degree AV block, the atria and ventricles operate independently, but their individual rhythms are typically regular. The SA node continues to fire, leading to a regular PP interval, while a secondary pacemaker in the AV junction or ventricles triggers the QRS complexes, leading to a regular RR interval. The lack of conduction between them does not inherently make the intervals irregular; it simply means there is no physiological relationship or synchrony between the two.
Choice B rationale
Third-degree heart block, or complete heart block, is characterized by a total failure of conduction between the atria and ventricles. The atrial rate, governed by the SA node, is normally 60 to 100 beats per minute. The ventricular escape rhythm is much slower, typically 20 to 40 beats per minute if originating in the ventricles. Because the atrial rate is faster than the independent ventricular rate, the ECG will show more P waves than QRS complexes.
Choice C rationale
The PP interval represents the atrial rate, and the RR interval represents the ventricular rate. In complete heart block, the atria usually beat at a normal physiological rate, whereas the ventricles beat at a much slower escape rate. Therefore, the PP interval will be significantly shorter than the RR interval. If these intervals were equal and a relationship existed, it would suggest a coordinated rhythm rather than the complete dissociation seen in a third-degree atrioventricular block.
Choice D rationale
A constant PR interval requires a consistent relationship where each QRS complex is triggered by a preceding P wave after a specific delay. In third-degree AV block, there is no relationship between P waves and QRS complexes. The P waves appear to march through the QRS complexes and T waves at their own pace. Because the atrial and ventricular activities are dissociated, the distance between any given P wave and the following QRS complex varies randomly.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A rationale
This sequence incorrectly places obtaining vital signs (step 4) before securing airway and oxygenation. In trauma management, the primary survey must follow the ABC (Airway, Breathing, Circulation) sequence. Assessing vitals and inserting a Foley catheter are part of the secondary survey or the end of the primary survey. Failing to stabilize the airway and breathing before taking a full set of vitals could lead to patient deterioration in an emergency rollover scenario.
Choice B rationale
This sequence starts with vital signs, which violates the fundamental principles of trauma resuscitation. In a rollover accident, the nurse must first address life-threatening airway and breathing issues. Moving directly to removing clothing (step 5) before ensuring the patient is breathing or has a clear airway is inappropriate. The priorities must focus on immediate physiological stabilization before moving to assessment tasks that do not directly treat hypoxia or airway obstruction in the trauma patient.
Choice C rationale
This sequence correctly follows the trauma primary survey (ABCDE).
Step 1 assesses breathing, followed by step 7 to open the airway if needed.
Step 2 provides oxygen for breathing support.
Step 6 addresses circulation by starting IVs for fluid resuscitation.
Step 5 involves exposure to check for hidden injuries.
Step 4 obtains vitals once life-threats are managed, and step 3 (Foley) is a later intervention. This represents the most scientific and systematic approach to trauma care.
Choice D rationale
Starting the intervention by removing clothing (step 5) and taking vital signs (step 4) ignores the immediate life-saving needs of airway and breathing management. A patient in a rollover accident may have a compromised airway or tension pneumothorax. Delaying airway opening (step 7) and oxygen administration (step 2) while focusing on vitals and exposure increases the risk of hypoxic brain injury and cardiac arrest, making this sequence unsafe and clinically unsound.
Correct Answer is A
Explanation
Choice A rationale
Severe sepsis triggers systemic vasodilation and increased capillary permeability, leading to absolute and relative hypovolemia. Restoring circulating blood volume is the highest priority to maintain organ perfusion and prevent irreversible cellular damage. Isotonic fluids, such as 0.9 percent normal saline or lactated Ringer solution, provide immediate intravascular expansion. Stabilizing the blood pressure, currently 80/50 mm Hg, takes precedence over all other interventions in the initial hour of sepsis management to ensure oxygen delivery to vital tissues.
Choice B rationale
Acetaminophen is indicated for the patient's temperature of 102 degrees F to reduce metabolic demand and improve comfort. However, hyperthermia is a physiological response to infection and is not immediately life-threatening compared to profound hypotension and shock. Administering a suppository does not address the underlying hemodynamic instability or the systemic inflammatory response. While necessary for supportive care, it is a lower priority than fluid resuscitation and starting antimicrobial therapy in the emergency setting.
Choice C rationale
Obtaining blood cultures from two different sites is a critical step in identifying the causative pathogen and guiding targeted antibiotic therapy. This should ideally be performed before the administration of antibiotics to increase the yield of the cultures. However, in the presence of severe hypotension, hemodynamic stabilization through fluid administration is the most urgent action. While cultures are essential for long-term management, the immediate survival of the patient depends on correcting the distributive shock state.
Choice D rationale
Broad-spectrum antibiotics are vital for treating the underlying infection in sepsis and should be administered as soon as possible, ideally within one hour of recognition. Delayed administration is associated with increased mortality. Nevertheless, if the patient is severely hypotensive, the physiological priority is to fill the vascular bed first. Fluids and antibiotics are often started near-simultaneously, but the nurse must ensure the bolus is initiated to provide the pressure needed to circulate the medications effectively.
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