Cardiopulmonary Bypass Principles — MCQs
Which protein is defective in dilated cardiomyopathy?
Heparin interferes with which of the following results of ABG
A postoperative patient with pH 7.25, MAP (mean arterial pressure) 60 mm Hg is treated with?
Which of the following is the LEAST significant risk factor for postoperative pulmonary complications?
Which of the following is not a risk factor for postoperative pulmonary complication?
Which of the following is not true about cardiopulmonary resuscitation (CPR)?
All are indications for one-lung ventilation except which of the following?
Which is not an obvious advantage of high-flow nasal cannula (HFNC):
The position of the patient as shown below is favored for which of the following conditions?
Which of the following is NOT a treatment for supraventricular tachycardia with hypotension in a patient under general anesthesia?
Cardiopulmonary Bypass Principles Indian Medical PG Practice Questions and MCQs
Question 1: Which protein is defective in dilated cardiomyopathy?
- A. Tropomyosin
- B. Myosin
- C. Troponin
- D. Dystrophin (Correct Answer)
Explanation: ***Dystrophin*** - **Dystrophin** is a crucial protein in the **muscle cell membrane** that anchors the cytoskeleton to the extracellular matrix. - Defects in dystrophin lead to sarcolemmal fragility, causing muscle damage and can result in **dilated cardiomyopathy**, especially in conditions like **Duchenne muscular dystrophy** [1]. *Myosin* - **Myosin** is a fundamental **motor protein** involved in muscle contraction, forming the thick filaments. - While mutations in myosin can cause various cardiac conditions, like hypertrophic cardiomyopathy, direct primary defects in myosin are not typically identified as the cause of dilated cardiomyopathy [2]. *Troponin* - **Troponin** is a protein complex that regulates muscle contraction by controlling the interaction between actin and myosin, particularly in response to calcium. - Although troponins are vital for cardiac function and are released during myocardial injury, their primary defect is not typically implicated in the etiology of dilated cardiomyopathy [2]. *Tropomyosin* - **Tropomyosin** is a protein that winds around actin filaments and, along with troponin, regulates the binding of myosin to actin. - While essential for muscle contraction, direct defects in tropomyosin are not a common genetic cause of dilated cardiomyopathy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1244-1245. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, p. 574.
Question 2: Heparin interferes with which of the following results of ABG
- A. pH
- B. PO2
- C. PCO2
- D. All of the options (Correct Answer)
Explanation: ***Correct: All of the options*** Heparin interferes with **all three major parameters** of arterial blood gas (ABG) analysis when used in excess amounts: **pH - Acidic effect:** - Heparin is an acidic solution (pH approximately 5-7) - Excess heparin in the sample causes **falsely low pH** readings - The acidic nature of heparin directly lowers the pH of the blood sample **PO2 - Dilutional and metabolic effects:** - Heparin dilutes the blood sample, affecting oxygen concentration - Can cause **falsely decreased PO2** if excess liquid heparin is used [1] - Cellular metabolism in delayed samples can consume oxygen, further reducing PO2 - Effect is more pronounced if analysis is not performed promptly **PCO2 - Dilutional effect:** - Excess heparin causes **dilution** of the blood sample - Results in **falsely decreased PCO2** readings [1] - The dilutional effect is the primary mechanism affecting PCO2 measurement **Clinical Pearl:** To minimize interference, use the minimum amount of heparin necessary (just enough to coat the syringe), avoid liquid heparin when possible, and analyze samples promptly after collection.
Question 3: A postoperative patient with pH 7.25, MAP (mean arterial pressure) 60 mm Hg is treated with?
- A. Only normal saline
- B. fluid restriction
- C. Fluid therapy with CVP monitoring (Correct Answer)
- D. I.V. sodium bicarbonate
Explanation: ***Fluid therapy with CVP monitoring*** - The patient's **MAP of 60 mmHg** indicates **hypotension** and potential **hypovolemic shock**, while pH 7.25 suggests **acidosis**, which could be metabolic due to poor perfusion. Initial treatment should focus on **restoring circulating volume** to improve blood pressure and organ perfusion. - **Central venous pressure (CVP) monitoring** is crucial to guide fluid resuscitation. It helps assess the patient's fluid status and ensures that enough fluid is given to improve cardiac output without causing fluid overload, especially in a severely ill patient. *Only normal saline* - While normal saline is used for fluid resuscitation, simply stating "only normal saline" is insufficient because it doesn't address the **critical need for monitoring** to guide treatment. - The amount and rate of fluid administration need to be carefully controlled based on the patient's response and hemodynamic parameters. *Fluid restriction* - **Fluid restriction** would be contraindicated in this patient because the **low MAP** suggests **hypovolemia or cardiogenic shock**, requiring fluid repletion, not restriction. - Restricting fluids could further worsen hypotension and organ hypoperfusion, leading to increased acidosis and organ damage. *I.V. sodium bicarbonate* - Administering **I.V. sodium bicarbonate** to correct acidosis without addressing the underlying cause of hypotension and poor perfusion is generally not recommended. - The acidosis (pH 7.25) is likely due to **poor tissue oxygenation and lactic acid production** from inadequate blood flow; correcting this with fluids will resolve the acidosis.
Question 4: Which of the following is the LEAST significant risk factor for postoperative pulmonary complications?
- A. Age >70
- B. Patient with 7 pack years of smoking
- C. Upper abdominal surgery
- D. BMI>30 (Correct Answer)
Explanation: ***BMI>30*** - While **obesity (BMI >30)** is associated with some surgical risks, it is generally considered a less significant independent risk factor for postoperative pulmonary complications compared to other factors like age, smoking, and surgical site. - The impact of obesity on pulmonary function is complex and varies depending on the type of surgery and presence of comorbid conditions like **sleep apnea**. *Age >70* - **Advanced age (>70)** is a significant independent risk factor due to decreased physiological reserve, reduced pulmonary function (e.g., decreased lung elasticity, impaired cough reflex), and increased prevalence of comorbidities. - Older patients are more susceptible to **atelectasis**, **pneumonia**, and **respiratory failure** postoperatively. *Patient with 7 pack years of smoking* - Even a relatively low cumulative smoking history of **7 pack-years** can impair mucociliary clearance, increase bronchial secretions, and cause airway inflammation, significantly increasing the risk of pulmonary complications. - Smoking compromises lung function and increases the risk of **bronchospasm** and infection. *Upper abdominal surgery* - **Upper abdominal surgery** is a significant risk factor because incisions close to the diaphragm interfere with diaphragmatic movement, leading to reduced lung volumes, impaired cough, and increased risk of **atelectasis** and **pneumonia**. - Pain from the incision further restricts deep breaths and coughing, contributing to pulmonary complications.
Question 5: Which of the following is not a risk factor for postoperative pulmonary complication?
- A. Normal BMI (18.5-24.9) (Correct Answer)
- B. Age 25-40 years
- C. Upper abdominal surgery
- D. Patient with 20 pack years of smoking
Explanation: ***Patient with 20 pack years of smoking*** - This is a significant risk factor for postoperative pulmonary complications, as **chronic smoking** impairs lung function and mucociliary clearance. - Patients with a history of **20 pack-years or more** are at a substantially increased risk of developing atelectasis, pneumonia, and respiratory failure after surgery. *Normal BMI (18.5-24.9)* - A **normal BMI** is not considered a risk factor for postoperative pulmonary complications; instead, it is associated with a lower risk compared to obesity or underweight states. - Patients with a normal BMI generally have **better respiratory mechanics** and lung volumes, reducing their susceptibility to pulmonary issues. *Age 25-40 years* - This age range is generally associated with a **lower risk** of postoperative pulmonary complications compared to very young or elderly patients. - Younger adults typically have **better physiological reserves** and healthier lungs, contributing to a reduced incidence of respiratory problems post-surgery. *Upper abdominal surgery* - **Upper abdominal surgery** is a significant risk factor for postoperative pulmonary complications due to its proximity to the diaphragm. - It often leads to **diaphragmatic dysfunction**, reduced lung volumes, and increased pain, all of which predispose patients to atelectasis and pneumonia.
Question 6: Which of the following is not true about cardiopulmonary resuscitation (CPR)?
- A. The most common cause of sudden death is ischemic heart disease
- B. Closed chest massage is as effective as open chest massage (Correct Answer)
- C. Standard chest massage generally provides less than 15% of normal coronary and cerebral blood flow
- D. Early defibrillation improves survival rates in ventricular fibrillation
Explanation: ***Closed chest massage is as effective as open chest massage*** - This statement is **not true** because **open-chest cardiac massage**, while more invasive, can provide significantly higher blood flow (coronary and cerebral) compared to closed-chest compressions. - Open-chest massage allows for direct compression of the heart, leading to better hemodynamics, especially in specific situations like **cardiac tamponade** or trauma. *The most common cause of sudden death is ischemic heart disease* - **Ischemic heart disease**, particularly conditions like myocardial infarction and severe coronary artery disease, is indeed the **leading cause of sudden cardiac death** in adults. - This is due to the high prevalence of atherosclerosis and its propensity to cause life-threatening arrhythmias such as **ventricular fibrillation**. *Standard chest massage generally provides less than 15% of normal coronary and cerebral blood flow* - Standard **closed-chest compressions** are known to generate only a fraction of normal cardiac output, typically **10-30% of normal cerebral blood flow** and **5-15% of normal coronary blood flow**. - This limited blood flow underscores the importance of high-quality, continuous compressions and prompt definitive treatment to improve outcomes. *Early defibrillation improves survival rates in ventricular fibrillation* - **Ventricular fibrillation (VF)** is a common cause of cardiac arrest, and **early defibrillation** (delivery of an electrical shock) is the most effective treatment to terminate VF and restore a perfusing rhythm. - The probability of successful defibrillation and survival **decreases significantly** with every minute that passes without defibrillation.
Question 7: All are indications for one-lung ventilation except which of the following?
- A. Massive hemorrhage in one lung
- B. Bronchopleural fistula
- C. Video-assisted thoracoscopic surgery
- D. General anesthesia without lung isolation (Correct Answer)
Explanation: ***General anesthesia without lung isolation*** - One-lung ventilation (OLV) is specifically performed to achieve **lung isolation**, which is the opposite of general anesthesia without lung isolation. - The goal of OLV is to collapse one lung to facilitate surgical access or prevent contamination, making general anesthesia without isolation a contraindication. *Bronchopleural fistula* - OLV is indicated in cases of **bronchopleural fistula** to prevent leakage of air from the affected lung into the intact lung. - This helps to maintain adequate ventilation and oxygenation in the healthy lung while the fistula can be managed or repaired. *Massive hemorrhage in one lung* - **Massive hemorrhage** in one lung is a critical indication for OLV to prevent the spread of blood to the contralateral healthy lung. - Isolating the bleeding lung protects the airway and facilitates surgical control of the hemorrhage. *Video-assisted thoracoscopic surgery* - **Video-assisted thoracoscopic surgery (VATS)** procedures frequently require OLV to collapse the operative lung. - This provides a clear surgical field and sufficient working space for the surgeon to perform the procedure without lung movement obstructing the view.
Question 8: Which is not an obvious advantage of high-flow nasal cannula (HFNC):
- A. Bypassing nasopharyngeal dead space
- B. Hot and Humidification of air (Correct Answer)
- C. PEEP
- D. Decreases need for intubation
Explanation: *Hot and Humidification of air* - This is an **obvious advantage** of HFNC, as it delivers warmed and humidified oxygen directly, improving patient comfort and mucociliary clearance. - The constant flow ensures the upper airway mucosa remains hydrated, preventing dryness and irritation that can occur with conventional oxygen therapy. ***Bypassing nasopharyngeal dead space*** - While HFNC does replace the gas in the **nasopharynx** with fresh gas, reducing dead space, this benefit is related to the high flow rate and is considered an **obvious advantage** in improving ventilatory efficiency. - The continuous washout of CO2 from the upper airway directly contributes to improved gas exchange. *PEEP* - HFNC can generate a modest level of **positive end-expiratory pressure (PEEP)**, which is an intentional and recognized effect due to the high flow rates. - This PEEP helps to recruit collapsed alveoli and improve oxygenation, making it an **obvious advantage** in respiratory support. *Decreases need for intubation* - The ability of HFNC to improve oxygenation, reduce work of breathing, and minimize airways inflammation is a well-established and **obvious advantage** that often prevents the need for invasive mechanical ventilation. - Clinical studies consistently demonstrate that HFNC can reduce intubation rates in patients with acute respiratory failure.
Question 9: The position of the patient as shown below is favored for which of the following conditions?
- A. CHF
- B. Air embolism
- C. Neurosurgery
- D. Raised ICP (Correct Answer)
Explanation: ***Raised ICT*** - The image depicts the patient in a **reverse Trendelenburg position** (head elevated). This position is often used to reduce **intracranial pressure (ICP)** by promoting venous drainage from the brain. - Elevating the head above the trunk aids in gravity-assisted drainage of cerebral venous blood and cerebrospinal fluid, thereby lowering ICP and preventing complications like brain herniation. *CHF* - Patients with **congestive heart failure (CHF)** often prefer a **Fowler's position** (sitting upright) to ease breathing and reduce pulmonary congestion, not the reverse Trendelenburg as shown. - Lying flat or with feet elevated in CHF can worsen dyspnea and increase cardiac workload due to increased venous return. *Air embolism* - For suspected **air embolism**, the patient is typically placed in the **Trendelenburg position** (head down, feet up) with a left lateral tilt to trap air in the right ventricle and prevent it from entering the pulmonary circulation. - This position helps prevent air from crossing into the left side of the heart thereby reducing the risk of systemic arterial air embolization. *Neurosurgery* - While neurosurgery often involves specific patient positioning, the depicted position isn't uniquely favored for neurosurgery in general. Positioning depends on the surgical site. - The **reverse Trendelenburg** is specifically used when reducing ICP is a primary goal during or after neurosurgical procedures, but not all neurosurgeries.
Question 10: Which of the following is NOT a treatment for supraventricular tachycardia with hypotension in a patient under general anesthesia?
- A. Carotid sinus massage
- B. Adenosine 3-12 mg IV
- C. Direct current cardioversion
- D. Verapamil 5 mg IV (Correct Answer)
Explanation: ### Explanation The management of intraoperative supraventricular tachycardia (SVT) depends primarily on the patient's **hemodynamic stability**. **1. Why Verapamil is the Correct Answer (The "NOT" treatment):** In a patient with SVT and **hypotension** (hemodynamic instability), calcium channel blockers like Verapamil are **contraindicated**. Verapamil has potent negative inotropic and vasodilator properties. Administering it to a hypotensive patient can cause a further drop in systemic vascular resistance and myocardial contractility, potentially leading to cardiovascular collapse or cardiac arrest. **2. Analysis of Other Options:** * **Direct Current (DC) Cardioversion (Option C):** This is the **treatment of choice** for any tachyarrhythmia causing hemodynamic instability (hypotension, altered mentation, or pulmonary edema) under general anesthesia. Synchronized cardioversion (starting at 50-100J) provides immediate rhythm correction. * **Adenosine (Option B):** If the patient is unstable but IV access is immediately available, Adenosine (6mg, then 12mg) can be attempted as it has an ultra-short half-life and may terminate the reentry circuit without prolonged hemodynamic depression. * **Carotid Sinus Massage (Option A):** This is a non-invasive vagal maneuver that can be attempted quickly to increase vagal tone and slow AV node conduction while preparing for cardioversion. **Clinical Pearls for NEET-PG:** * **Unstable Tachycardia:** Always choose **Synchronized DC Cardioversion**. * **Stable SVT:** First-line is Vagal maneuvers, followed by Adenosine (Drug of Choice). * **Verapamil Warning:** Never give Verapamil in wide-complex tachycardias of unknown origin or in patients with WPW syndrome + Atrial Fibrillation, as it can lead to ventricular fibrillation. * **Amiodarone:** Preferred for stable ventricular tachycardia or refractory SVT.
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