Inotropes and Vasopressors — MCQs
Effects of beta blockers on the heart are all of the following except:
Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?
Shock is clinically best assessed by:
Drug of choice in cardiogenic shock is
A 70-year-old man develops pneumonia and septicemia, and subsequently experiences renal failure with a blood pressure of 70/50 mmHg. Which drug should be used to maintain blood pressure?
All are effects of the parasympathetic system on the heart except?
Beta2-agonists cause all except:
Most common cause of maternal mortality in spinal anesthesia is ?
Historically, which anesthetic agent was considered most effective for uterine relaxation during surgical procedures?
Which volatile anesthetic agent is MOST commonly recognized for its clinically significant tocolytic effects in obstetric anesthesia?
Inotropes and Vasopressors Indian Medical PG Practice Questions and MCQs
Question 1: Effects of beta blockers on the heart are all of the following except:
- A. Decreases duration of systole (Correct Answer)
- B. Decrease in heart rate
- C. May decrease cardiac output initially.
- D. May precipitate heart failure in acute settings.
Explanation: ***Decreases duration of systole*** - Beta-blockers primarily prolong the **duration of systole** by extending the **ejection time** and slowing ventricular relaxation. - They also increase the **diastolic filling time** by reducing heart rate, impacting overall cardiac cycle duration. *Decrease in heart rate* - Beta-blockers block **beta-1 adrenergic receptors** in the heart, leading to a decrease in **sympathetic stimulation** and thus a reduced heart rate. - This effect is beneficial in conditions like **tachycardia** and **angina**, as it reduces myocardial oxygen demand. *May decrease cardiac output initially.* - By reducing heart rate and contractility, beta-blockers can initially decrease **cardiac output**, especially in patients with pre-existing **ventricular dysfunction**. - This effect is often transient, as chronic use can lead to beneficial remodeling and improved efficiency in some conditions. *May precipitate heart failure in acute settings.* - In patients with acutely decompensated heart failure or severe left ventricular dysfunction, beta-blockers can acutely worsen cardiac function due to their **negative inotropic effects**. - Therefore, beta-blockers are typically initiated cautiously at low doses in stable heart failure patients and are contraindicated in acute decompensation.
Question 2: Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?
- A. Norepinephrine (Correct Answer)
- B. Dopamine
- C. Acetylcholine
- D. Epinephrine
Explanation: ***Norepinephrine*** - **Norepinephrine** is the primary neurotransmitter released by **postganglionic sympathetic neurons** directly onto the heart to increase heart rate and contractility in response to a drop in blood pressure. - It acts on **beta-1 adrenergic receptors** in the sinoatrial (SA) node, atria, and ventricles, leading to increased chronotropy (heart rate) and inotropy (contractility). *Dopamine* - While **dopamine** can have cardiovascular effects, particularly at high doses, it is not the primary neurotransmitter released by the sympathetic nervous system for direct heart rate regulation. - Dopamine is a precursor to norepinephrine and epinephrine, but its main physiological roles involve **renal blood flow regulation** and central nervous system functions. *Acetylcholine* - **Acetylcholine** is the primary neurotransmitter of the **parasympathetic nervous system**, which generally acts to **decrease heart rate** (bradycardia) through muscarinic receptors. - It is also released by **preganglionic sympathetic fibers**, but these do not directly innervate the heart to produce the desired effect of increasing heart rate. *Epinephrine* - **Epinephrine** (adrenaline) is primarily a **hormone** released from the **adrenal medulla** into the bloodstream, not directly from postganglionic sympathetic nerve terminals to the heart. - Although it has strong effects on beta-1 receptors in the heart, its release is more generalized and slower than the direct neuronal release of norepinephrine.
Question 3: Shock is clinically best assessed by:
- A. CVP
- B. BP
- C. Hydration
- D. Mental status (Correct Answer)
Explanation: **Mental status** - The **brain** is highly sensitive to tissue perfusion, and changes in mental status (e.g., confusion, disorientation) are often among the **earliest and most reliable clinical indicators of inadequate organ perfusion** in shock [1]. - Assessing mental status is a quick, non-invasive method to gauge the adequacy of **cerebral blood flow**, directly reflecting the body's response to hypoperfusion [1]. *CVP* - **Central Venous Pressure (CVP)** primarily reflects the right ventricular preload and overall fluid status but does not directly measure tissue perfusion throughout the body [1]. - While CVP can guide fluid resuscitation, it is not a direct measure of systemic tissue oxygenation and can be affected by numerous factors unrelated to shock severity [1]. *BP* - **Blood pressure (BP)** is a relatively late and insensitive indicator of shock, as compensatory mechanisms can maintain BP within normal limits even when significant hypoperfusion is already occurring [1]. - By the time **hypotension** (low BP) is observed, shock is often advanced, and other signs of organ dysfunction may already be present [1]. *Hydration* - **Hydration status** refers to the body's overall fluid balance and, while important in managing shock, is not the best clinical assessment tool for defining the presence or severity of shock itself. - While dehydration can contribute to hypovolemic shock, assessing hydration is an indirect measure and doesn't directly reflect systemic tissue perfusion or oxygen delivery.
Question 4: Drug of choice in cardiogenic shock is
- A. Noradrenaline
- B. Dopamine (Correct Answer)
- C. Adrenaline
- D. Phenylephrine
Explanation: ***Dopamine*** - **Dopamine** is often considered the **drug of choice** in cardiogenic shock because, at low to moderate doses, it increases myocardial contractility and heart rate (positive inotropic and chronotropic effects) while also improving renal perfusion. - Its ability to stimulate **alpha-1, beta-1, and dopaminergic receptors** makes it effective in improving cardiac output and maintaining organ perfusion in this critical condition. *Phenylephrine* - **Phenylephrine** is a selective **alpha-1 adrenergic agonist** that causes potent vasoconstriction and increases systemic vascular resistance. - While it effectively raises blood pressure, it **lacks inotropic effects** and can actually **reduce cardiac output** through reflex bradycardia and increased afterload. - Its strong vasoconstrictive effects without inotropic support make it **not suitable** as a primary agent in cardiogenic shock where cardiac contractility is already compromised. *Noradrenaline* - **Noradrenaline (norepinephrine)** is a potent vasoconstrictor primarily acting on alpha-1 receptors, leading to a significant increase in systemic vascular resistance and blood pressure. - While useful in some forms of shock, its strong vasoconstrictive effect can **increase afterload** and potentially worsen myocardial oxygen demand in cardiogenic shock with already compromised cardiac function. *Adrenaline* - **Adrenaline (epinephrine)** has strong **beta-1 and alpha-1 agonist effects**, leading to increased heart rate, contractility, and vasoconstriction. - While it can improve blood pressure and cardiac output, its significant **chronotropic and arrhythmogenic effects**, along with increased myocardial oxygen demand, make it less favorable than dopamine as a first-line agent in cardiogenic shock.
Question 5: A 70-year-old man develops pneumonia and septicemia, and subsequently experiences renal failure with a blood pressure of 70/50 mmHg. Which drug should be used to maintain blood pressure?
- A. Adrenaline
- B. Ephedrine
- C. Phenylephrine
- D. Norepinephrine (Correct Answer)
Explanation: ***Norepinephrine*** - **Norepinephrine** is the first-line vasopressor recommended for treating **septic shock** with hypotension unresponsive to fluid resuscitation, as it potently increases **mean arterial pressure** without excessive tachycardia. - It primarily acts on **alpha-1 adrenergic receptors** to cause vasoconstriction, thereby increasing systemic vascular resistance and blood pressure, which is crucial in stabilizing a patient with **sepsis and renal failure**. *Adrenaline* - **Adrenaline (epinephrine)** is a potent vasopressor but is generally reserved for septic shock unresponsive to norepinephrine or in cases of **cardiac arrest** due to its potential for increased arrhythmias and splanchnic vasoconstriction. - While it raises blood pressure, its broader **beta-adrenergic effects** can lead to undesirable side effects such as tachycardia and increased myocardial oxygen demand. *Ephedrine* - **Ephedrine** is an indirect sympathomimetic that releases stored norepinephrine, providing both alpha and beta effects, but its use in severe septic shock is limited by its **weaker and less predictable pressor effect** compared to direct-acting catecholamines. - It has a slower onset and longer duration of action, making it less suitable for rapid titration and precise blood pressure control in an acute, unstable condition like **septic shock**. *Phenylephrine* - **Phenylephrine** is a pure alpha-1 agonist that causes significant vasoconstriction and increases blood pressure, but its use in septic shock is generally discouraged due to its potential to cause **reflex bradycardia** and a higher risk of reducing **cardiac output**. - While it effectively raises blood pressure, its lack of direct inotropic effects and potential for reducing perfusion to vital organs make it a less optimal choice compared to norepinephrine in **septicemia-induced hypotension**.
Question 6: All are effects of the parasympathetic system on the heart except?
- A. Negative chronotropic
- B. Negative dromotropic
- C. All are seen
- D. Negative inotropic (Correct Answer)
Explanation: ***Negative inotropic*** - While the parasympathetic system (via the **vagus nerve**) primarily affects the **sinoatrial (SA) and atrioventricular (AV) nodes** to decrease heart rate and conduction velocity, it has a **minimal direct effect on ventricular contractility** (inotropy) in humans. - The ventricles are less densely innervated by parasympathetic fibers compared to the atria, so acetylcholine's direct negative inotropic effect is **clinically insignificant** in a healthy heart. - This is the **EXCEPTION** - not a significant parasympathetic effect on the heart. *Negative chronotropic* - The parasympathetic system, primarily through **acetylcholine** acting on **muscarinic receptors** in the SA node, decreases the heart rate (chronotropy). - This slows the rate of spontaneous depolarization of pacemaker cells. - This **IS** a major parasympathetic effect. *Negative dromotropic* - Parasympathetic stimulation also slows the conduction velocity through the **AV node** (dromotropy). - This increases the PR interval on an ECG and can lead to various degrees of AV block in extreme cases. - This **IS** a major parasympathetic effect. *All are seen* - This option is incorrect because the **negative inotropic effect** is NOT a significant parasympathetic effect on the heart. - While negative chronotropic and negative dromotropic effects are prominent features of parasympathetic activity, the direct influence on ventricular contractility is minimal.
Question 7: Beta2-agonists cause all except:
- A. Hyperkalemia (Correct Answer)
- B. Hyperglycemia
- C. Tremor
- D. Palpitation
Explanation: ***Hyperkalemia*** - Beta2-agonists actually cause **hypokalemia**, not hyperkalemia, by promoting the intracellular shift of potassium. - This effect is due to the stimulation of the **Na+/K+-ATPase pump** by beta-2 adrenergic receptors. *Hyperglycemia* - Beta2-agonists can lead to **hyperglycemia** by promoting glycogenolysis and gluconeogenesis in the liver. - They also decrease **insulin secretion** and increase insulin resistance. *Tremor* - **Tremor** is a common side effect of beta2-agonists, particularly in the hands, due to direct stimulation of beta2 receptors on skeletal muscle. - This muscle stimulation leads to increased muscle twitching and a fine tremor. *Palpitation* - **Palpitations** can occur due to the systemic absorption of beta2-agonists, leading to activation of beta1 receptors in the heart. - This can cause **tachycardia** and a sensation of a racing heart.
Question 8: Most common cause of maternal mortality in spinal anesthesia is ?
- A. Allergy to local anesthesia
- B. Nerve injury
- C. Hypotension (Correct Answer)
- D. High block
Explanation: ***Hypotension*** - **Profound hypotension** due to sympathetic blockade is the most common cause of maternal mortality in spinal anesthesia. - This can lead to **decreased placental perfusion**, fetal distress, and maternal cardiovascular collapse if not promptly managed. *Allergy to local anesthesia* - True allergic reactions to local anesthetics are **extremely rare**, especially to ester-type anesthetics used in spinal anesthesia. - While possible, it is not the most common cause of maternal mortality. *Nerve injury* - **Direct nerve injury** during spinal anesthesia is a rare complication, usually resulting in localized neurological deficits rather than mortality. - It does not represent the primary cause of maternal death. *High block* - A **high spinal block** can cause severe hypotension and respiratory compromise, which can lead to mortality. - However, the underlying mechanism for the life-threatening aspects of a high block is often **severe hypotension** and subsequent cardiovascular collapse.
Question 9: Historically, which anesthetic agent was considered most effective for uterine relaxation during surgical procedures?
- A. Nitrous oxide
- B. Halothane (Correct Answer)
- C. Sevoflurane
- D. Desflurane
Explanation: **Halothane** * **Halothane** was historically well-known for its potent ability to induce **uterine relaxation**, which was crucial for procedures like manual placenta removal or during challenging fetal extraction. * This property, however, also meant that it could cause significant **postpartum hemorrhage** due to uterine atony. * *Sevoflurane* * Sevoflurane provides **moderate uterine relaxation** but is less potent in this regard compared to halothane at equipotent doses. * It is a more modern inhaled anesthetic with a **faster onset and offset** than halothane. * *Nitrous oxide* * **Nitrous oxide** offers very **minimal to no uterine relaxation** and is often used as an adjunct to other anesthetics. * It is an analgesic and weak anesthetic, primarily used for its pain-relieving effects. * *Desflurane* * **Desflurane** also provides **moderate uterine relaxation**, similar to sevoflurane, but is less potent than halothane. * It has a very **rapid onset and offset**, making it suitable for quick adjustments in anesthetic depth, but it is also a respiratory irritant.
Question 10: Which volatile anesthetic agent is MOST commonly recognized for its clinically significant tocolytic effects in obstetric anesthesia?
- A. Isoflurane (Correct Answer)
- B. Sevoflurane
- C. Nitrous oxide
- D. Desflurane
Explanation: ***Isoflurane*** - **Isoflurane** is well-known for its potent dose-dependent uterine relaxation (tocolytic) properties, which can be clinically useful during obstetric procedures requiring uterine quiescence, such as manual placenta removal or fetal manipulation. - This effect is due to its ability to decrease the frequency and intensity of uterine contractions by relaxing myometrial smooth muscle. *Sevoflurane* - While sevoflurane does possess uterine relaxant properties, its tocolytic effect is generally considered less potent compared to isoflurane at equipotent doses. - It is frequently favored for maintenance of anesthesia in obstetrics due to its rapid onset and offset, but its uterine relaxation is often less pronounced than that of isoflurane. *Desflurane* - Desflurane also causes dose-dependent uterine relaxation, but its tocolytic effects are not typically considered as significant or as commonly utilized for specific uterine relaxation needs as isoflurane. - Its rapid pharmacokinetics make it suitable for obstetric anesthesia, but its uterine effects are generally in line with other volatile agents, with isoflurane having a more pronounced reputation for tocolysis. *Nitrous oxide* - **Nitrous oxide** has minimal to no direct significant uterine relaxant (tocolytic) effects, making it a common choice for analgesia during labor in sub-anesthetic concentrations. - It does not cause the widespread smooth muscle relaxation observed with potent volatile agents, hence is not used for obstetric scenarios requiring uterine quiescence.
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