Lecture Notes Review: Dysrhythmias, Shock, Gas Exchange, Respiratory Failure, and Mechanical Ventilation

A comprehensive set of Q&A flashcards covering dysrhythmias, shock physiology, gas exchange, respiratory failure, ARDS, and mechanical ventilation concepts from the lecture notes.

What are the normal intrinsic rates for the cardiac conduction system components (SA node, AV node, Bundle of His/Purkinje system) and their typical ranges?

SA node: 60-100 beats per minute; AV node: 40-60 beats per minute; Bundle of His/Purkinje system: 20-40 beats per minute.

What characterizes a Premature Ventricular Contraction (PVC) on ECG and what common underlying issues might contribute to it?

A PVC is a wide, early ventricular beat that often interrupts a normal rhythm; it can be caused by electrolyte disturbances (e.g., potassium, magnesium) and/or acidotic states; frequent PVCs require assessment and management of the underlying cause.

What is Pulseless Electrical Activity (PEA) and how should it be managed?

PEA shows a organized electrical activity on monitor but no palpable pulse; manage with CPR, identify reversible causes, and do not shock (not a shockable rhythm).

How is ventricular tachycardia (VT) managed when a patient has a pulse versus when there is no pulse?

With a pulse: assess stability; may cardiovert if unstable. Without a pulse: begin CPR and defibrillate if VT is shockable, followed by ACLS medications and reversible cause treatment.

What is a complete (third-degree) AV block and its typical management strategy?

There is complete dissociation between P waves and QRS complexes; no conduction from atria to ventricles; requires pacing (temporary or permanent) to maintain rate and perfusion.

What do bigeminy and trigeminy mean in the context of PVCs?

Bigeminy: PVCs occur every other beat; Trigeminy: PVCs occur every third beat.

Differentiate defibrillation from cardioversion in rhythm management.

Defibrillation is unsynchronized shock used for pulseless VT/VF; cardioversion is synchronized shock used for rhythms with a pulse (and often stabilized patients).

What is the role of pacing in bradyarrhythmias or complete AV block?

Temporary transvenous or external pacing may be used to maintain rate and perfusion when intrinsic conduction is disrupted.

What is oncotic pressure and how does it relate to edema and ascites?

Oncotic pressure is the attractive force exerted by plasma proteins (especially albumin) drawing water into vessels; low oncotic pressure promotes edema and ascites.

How do you calculate mean arterial pressure (MAP) using the bedside formula?

MAP ≈ (2 × diastolic BP + systolic BP) / 3.

Describe the nonprogressive (compensatory) stage of shock.

Early stage where compensatory mechanisms maintain perfusion; tissues are still salvageable and BP may be maintained with early interventions.

Describe the progressive stage of shock.

Hypotension develops, perfusion to organs declines, rising HR, decreased urine output, altered mental status, cool/clammy skin; requires vasopressors and aggressive support.

What does mixed venous oxygen saturation (SvO2) indicate and what is its typical range?

SvO2 reflects the balance between oxygen delivery and consumption; normal range is about 60-80% (measured via the pulmonary artery catheter in cardiac patients).

Which organ is particularly at risk for ischemia during shock, and what does this imply for monitoring?

The gut (and other organs) can suffer ischemia due to hypoperfusion; monitor mental status, urine output, and GI signs as part of perfusion assessment.

What is a V/Q mismatch and how is it addressed?

Ventilation-perfusion mismatch occurs when ventilation (V) and perfusion (Q) do not align, impairing gas exchange; fix underlying cause to improve matching.

Explain the right shift of the oxyhemoglobin dissociation curve and its clinical significance.

Right shift occurs with acidosis, fever, and high CO2; hemoglobin releases O2 more readily to tissues (decreased affinity).

Explain the left shift of the oxyhemoglobin dissociation curve and its clinical significance.

Left shift occurs with alkalosis, hypothermia, and low CO2; hemoglobin holds onto O2 more tightly, reducing delivery to tissues.

Why might COPD patients have CO2 retention and what impact does this have on oxygenation?

Ventilation is impaired leading to hypercapnia and respiratory acidosis; this can worsen oxygenation and drive compensatory mechanisms.

What is the primary purpose of supplemental oxygen therapy in gas exchange disturbances?

To increase alveolar PO2 and thereby improve oxygen delivery to tissues, correcting hypoxemia when indicated.

What ABG pattern defines respiratory acidosis?

Low pH with elevated PaCO2 (possible low PaO2 as well) indicating hypoventilation and CO2 retention.

What characterizes Acute Respiratory Distress Syndrome (ARDS) and its management?

ARDS involves diffuse alveolar damage with increased permeability, bilateral infiltrates, reduced lung compliance, and severe hypoxemia; managed with lung-protective ventilation (low tidal volumes), PEEP, prone positioning, and conservative fluids.

What are typical indications for endotracheal intubation and mechanical ventilation?

Severe or failing gas exchange, respiratory failure not amenable to noninvasive support, altered mental status, fatigue, and inability to protect the airway.

What are key steps to verify endotracheal tube placement and patency after intubation?

Confirm with chest x-ray, auscultate for equal breath sounds, ensure proper tube depth, inflate cuff appropriately, and suction as needed while monitoring for changes.

What are common ventilator alarms and what do they indicate?

High-pressure alarms suggest obstruction or secretions; low-pressure alarms suggest disconnection, cuff leak, or tube dislodgement.

What is CPAP and when is it commonly used?

Continuous positive airway pressure delivered noninvasively; patient must be able to initiate breaths; used to improve oxygenation in appropriate respiratory failure.

What is BiPAP and how does it differ from CPAP?

BiPAP provides two pressure levels (IPAP/EPAP) to assist inspiration and expiration; patient may initiate breaths; useful in COPD and certain respiratory failures.

What is PEEP and what are its benefits and risks in mechanical ventilation?

Positive end-expiratory pressure helps recruit and keep alveoli open, improving oxygenation; may decrease venous return and cause barotrauma if excessive.

What are common considerations and risks of prolonged invasive ventilation?

Risks include ventilator-associated pneumonia, mucosal injury, skin breakdown, sedation-related issues, and respiratory muscle deconditioning.

What is the difference between invasive and noninvasive mechanical ventilation?

Invasive ventilation uses an artificial airway (endotracheal/tracheostomy tube); noninvasive ventilation uses masks (CPAP/BiPAP) without an artificial airway.

What are the normal intrinsic rates for the cardiac conduction system components (SA node, AV node, Bundle of His/Purkinje system) and their typical ranges?

SA node: 60-100 beats per minute; AV node: 40-60 beats per minute; Bundle of His/Purkinje system: 20-40 beats per minute.

What characterizes a Premature Ventricular Contraction (PVC) on ECG and what common underlying issues might contribute to it?

A PVC is a wide, early ventricular beat that often interrupts a normal rhythm; it can be caused by electrolyte disturbances (e.g., potassium, magnesium) and/or acidotic states; frequent PVCs require assessment and management of the underlying cause.

What is Pulseless Electrical Activity (PEA) and how should it be managed?

PEA shows a organized electrical activity on monitor but no palpable pulse; manage with CPR, identify reversible causes, and do not shock (not a shockable rhythm).

How is ventricular tachycardia (VT) managed when a patient has a pulse versus when there is no pulse?

With a pulse: assess stability; may cardiovert if unstable. Without a pulse: begin CPR and defibrillate if VT is shockable, followed by ACLS medications and reversible cause treatment.

What is torsades de pointes and how is it treated?

A polymorphic VT associated with prolonged QT; treat with magnesium sulfate and defibrillate if pulseless.

What is a complete (third-degree) AV block and its typical management strategy?

There is complete dissociation between P waves and QRS complexes; no conduction from atria to ventricles; requires pacing (temporary or permanent) to maintain rate and perfusion.

What do bigeminy and trigeminy mean in the context of PVCs?

Bigeminy: PVCs occur every other beat; Trigeminy: PVCs occur every third beat.

Differentiate defibrillation from cardioversion in rhythm management.

Defibrillation is unsynchronized shock used for pulseless VT/VF; cardioversion is synchronized shock used for rhythms with a pulse (and often stabilized patients).

What is the role of pacing in bradyarrhythmias or complete AV block?

Temporary transvenous or external pacing may be used to maintain rate and perfusion when intrinsic conduction is disrupted.

What is oncotic pressure and how does it relate to edema and ascites?

Oncotic pressure is the attractive force exerted by plasma proteins (especially albumin) drawing water into vessels; low oncotic pressure promotes edema and ascites.

How do you calculate mean arterial pressure (MAP) using the bedside formula?

MAP \approx (2 \times diastolic BP + systolic BP) / 3.

Describe the nonprogressive (compensatory) stage of shock.

Early stage where compensatory mechanisms maintain perfusion; tissues are still salvageable and BP may be maintained with early interventions.

Describe the progressive stage of shock.

Hypotension develops, perfusion to organs declines, rising HR, decreased urine output, altered mental status, cool/clammy skin; requires vasopressors and aggressive support.

What is the irreversible stage of shock?

The final stage where organ damage is so severe that recovery is unlikely, even with aggressive intervention, leading to multi-organ failure and death.

What is hypovolemic shock and its primary management?

Caused by significant fluid loss (e.g., hemorrhage, severe dehydration); primary management involves rapid fluid resuscitation (crystalloids, blood products) to restore circulating volume.

What is cardiogenic shock and its primary management?

Results from the heart's inability to pump enough blood to meet the body's demands, often due to myocardial infarction; management focuses on improving cardiac output (e.g., inotropes, vasopressors, mechanical circulatory support) and treating the underlying cardiac issue.

What is septic shock and its primary management?

A life-threatening organ dysfunction caused by a dysregulated host response to infection, leading to refractory hypotension; management includes early identification, rapid administration of broad-spectrum antibiotics, fluid resuscitation, and vasopressors.

What does mixed venous oxygen saturation (SvO2) indicate and what is its typical range?

SvO2 reflects the balance between oxygen delivery and consumption; normal range is about 60-80% (measured via the pulmonary artery catheter in cardiac patients).

Which organ is particularly at risk for ischemia during shock, and what does this imply for monitoring?

The gut (and other organs) can suffer ischemia due to hypoperfusion; monitor mental status, urine output, and GI signs as part of perfusion assessment.

What is a V/Q mismatch and how is it addressed?

Ventilation-perfusion mismatch occurs when ventilation (V) and perfusion (Q) do not align, impairing gas exchange; fix underlying cause to improve matching.

Explain the right shift of the oxyhemoglobin dissociation curve and its clinical significance.

Right shift occurs with acidosis, fever, and high CO2; hemoglobin releases O2 more readily to tissues (decreased affinity).

Explain the left shift of the oxyhemoglobin dissociation curve and its clinical significance.

Left shift occurs with alkalosis, hypothermia, and low CO2; hemoglobin holds onto O2 more tightly, reducing delivery to tissues.

Why might COPD patients have CO2 retention and what impact does this have on oxygenation?

Ventilation is impaired leading to hypercapnia and respiratory acidosis; this can worsen oxygenation and drive compensatory mechanisms.

What is the primary purpose of supplemental oxygen therapy in gas exchange disturbances?

To increase alveolar PO2 and thereby improve oxygen delivery to tissues, correcting hypoxemia when indicated.

What ABG pattern defines respiratory acidosis?

Low pH with elevated PaCO2 (possible low PaO2 as well) indicating hypoventilation and CO2 retention.

What characterizes Acute Respiratory Distress Syndrome (ARDS) and its management?

ARDS involves diffuse alveolar damage with increased permeability, bilateral infiltrates, reduced lung compliance, and severe hypoxemia; managed with lung-protective ventilation (low tidal volumes), PEEP, prone positioning, and conservative fluids.

What are typical indications for endotracheal intubation and mechanical ventilation?

Severe or failing gas exchange, respiratory failure not amenable to noninvasive support, altered mental status, fatigue, and inability to protect the airway.

What are key steps to verify endotracheal tube placement and patency after intubation?

Confirm with chest x-ray, auscultate for equal breath sounds, ensure proper tube depth, inflate cuff appropriately, and suction as needed while monitoring for changes.

What are common ventilator alarms and what do they indicate?

High-pressure alarms suggest obstruction or secretions; low-pressure alarms suggest disconnection, cuff leak, or tube dislodgement.

What is CPAP and when is it commonly used?

Continuous positive airway pressure delivered noninvasively; patient must be able to initiate breaths; used to improve oxygenation in appropriate respiratory failure.

What is BiPAP and how does it differ from CPAP?

BiPAP provides two pressure levels (IPAP/EPAP) to assist inspiration and expiration; patient may initiate breaths; useful in COPD and certain respiratory failures.

What is PEEP and what are its benefits and risks in mechanical ventilation?

Positive end-expiratory pressure helps recruit and keep alveoli open, improving oxygenation; may decrease venous return and cause barotrauma if excessive.

What are common considerations and risks of prolonged invasive ventilation?

Risks include ventilator-associated pneumonia, mucosal injury, skin breakdown, sedation-related issues, and respiratory muscle deconditioning.

What is the difference between invasive and noninvasive mechanical ventilation?

Invasive ventilation uses an artificial airway (endotracheal/tracheostomy tube);