Preoperative Evaluation and Management Practice Questions

Q: Atropine as preanesthesia has all effects except?

Bronchoconstriction. **Explanation:** Atropine is a competitive **muscarinic acetylcholine receptor antagonist** (anticholinergic). Its use in premedication is based on its ability to block parasympathetic (vagal) activity. **Why "Bronchoconstriction" is the correct answer:** Atropine causes **bronchodilation**, not bronchoconstriction. By blocking the M3 receptors on bronchial smooth muscle, it inhibits the constrictive effects of acetylcholine. This increases anatomical dead space but is beneficial in preventing intraoperative bronchospasm. **Analysis of other options:** * **A. Decrease secretion:** Atropine is a potent antisialagogue. It blocks M3 receptors in salivary and bronchial glands, reducing secretions. This is crucial for maintaining a clear airway and preventing laryngospasm during induction. * **C. Prevent bradycardia:** Atropine exerts a positive chronotropic effect by blocking M2 receptors at the SA node, thereby counteracting vagal-induced bradycardia caused by surgical maneuvers (e.g., traction on extraocular muscles) or drugs (e.g., succinylcholine, halothane). * **D. Prevent hypotension:** By preventing or treating bradycardia, atropine helps maintain cardiac output (CO = HR × SV), thereby preventing a drop in blood pressure associated with vagal stimulation. **NEET-PG High-Yield Pearls:** 1. **Blood-Brain Barrier:** Atropine is a tertiary amine; it **crosses** the BBB and can cause Central Anticholinergic Syndrome (confusion/delirium), especially in the elderly. 2. **Order of Potency:** * **Antisialagogue:** Scopolamine > Glycopyrrolate > Atropine. * **Tachycardia:** Atropine > Glycopyrrolate > Scopolamine. 3. **Contraindication:** Relative contraindication in patients with **narrow-angle glaucoma** (causes mydriasis) and prostatic hypertrophy (causes urinary retention). 4. **Glycopyrrolate** is often preferred over Atropine as it is a quaternary ammonium (does not cross BBB) and has a longer duration of action.

Q: Which drugs can interfere with anesthesia?

All of the above. **Explanation:** The correct answer is **D. All of the above**. Several classes of non-anesthetic drugs can significantly alter the pharmacodynamics and pharmacokinetics of anesthetic agents, leading to potential intraoperative complications. 1. **Calcium Channel Blockers (e.g., Nifedipine):** These drugs can potentiate the effects of both depolarizing and non-depolarizing neuromuscular blocking agents (NMBAs) by inhibiting calcium-mediated acetylcholine release at the motor endplate. They also increase the risk of myocardial depression and hypotension when combined with volatile anesthetics. 2. **Beta Blockers:** While often continued perioperatively for cardioprotection, they can interfere with the body’s compensatory sympathetic response to blood loss or deep anesthesia. They may lead to profound bradycardia and decreased cardiac contractility when used alongside agents like halothane or propofol. 3. **Aminoglycosides (e.g., Gentamicin, Neomycin):** These antibiotics are notorious for potentiating neuromuscular blockade. They inhibit the pre-junctional release of acetylcholine and decrease post-junctional sensitivity, potentially leading to prolonged respiratory depression or "recurarization" in the recovery room. **High-Yield Clinical Pearls for NEET-PG:** * **Antibiotics:** Besides aminoglycosides, **clindamycin and tetracyclines** also potentiate NMBAs. * **Lithium:** Prolongs the duration of action of both succinylcholine and pancuronium. * **Magnesium Sulfate:** Potentiates NMBAs significantly (often used in pre-eclampsia). * **MAO Inhibitors:** Must be monitored closely due to the risk of hypertensive crisis (with indirect sympathomimetics) or serotonin syndrome (with pethidine). * **Rule of Thumb:** Most drugs that interfere with NMBAs do so by affecting calcium channels or acetylcholine release at the neuromuscular junction.

Q: What is the dose of atropine for premedication per kilogram of body weight?

0.01 mg. ### Explanation **Correct Answer: C. 0.01 mg** **Understanding the Concept:** Atropine is a competitive muscarinic antagonist used in premedication primarily for its **antisialagogue** (reduction of secretions) and **vagolytic** (prevention of bradycardia) effects. In clinical anesthesia, the standard dose for premedication is **0.01 mg/kg to 0.02 mg/kg**. For an average 60 kg adult, this translates to a total dose of approximately 0.6 mg, which is the standard ampoule size. **Analysis of Options:** * **A. 10 mg:** This is a massive overdose. Such a dose would lead to severe "Atropine Toxicity" (central anticholinergic syndrome), characterized by delirium, hyperthermia, and potentially fatal arrhythmias. * **B. 0.1 mg:** While this is a common dose for certain pediatric scenarios, as a per-kilogram dose, it is 10 times the standard requirement for an adult. * **D. 0.001 mg:** This dose is sub-therapeutic. At very low doses (less than 0.4 mg total in adults), atropine can paradoxically cause **bradycardia** due to its central effects or blockade of presynaptic inhibitory M1 receptors. **High-Yield NEET-PG Pearls:** * **Route:** Usually administered Intramuscularly (IM) 30–60 minutes before induction or Intravenously (IV) immediately before induction. * **Drug of Choice:** While atropine is common, **Glycopyrrolate (0.005–0.01 mg/kg)** is often preferred as a premedication because it does not cross the blood-brain barrier (quaternary ammonium) and has a more potent antisialagogue effect. * **Contraindications:** Avoid in patients with **Narrow-angle Glaucoma**, Pyloric stenosis, and Tachyarrhythmias. * **Scopolamine:** Another anticholinergic used for premedication, specifically for its superior sedative and anti-emetic properties.

Question 1

A 27-year-old male patient is referred for resection of pheochromocytoma. Which of the following medications should the patient be taking prior to surgery?

Accepted Answer

Phenoxybenzamine

Answer

Propranolol

Answer

Labetalol

Answer

Hydralazine

Question 2

Which statement regarding calcium channel blockers in anesthesia is TRUE?

Accepted Answer

They should be given in normal doses as they prevent MI and angina.

Answer

They need to be decreased as they augment hypotension and muscle relaxation.

Answer

They should be withheld because they lower LES pressure.

Answer

All of the above.

Question 3

A 45-year-old male with a history of smoking is scheduled for elective surgery. Which of the following statements regarding the effects of smoking is FALSE?

Accepted Answer

Carbon monoxide shifts the O2-Hb dissociation curve to the right.

Answer

The effect of nicotine on aortic and carotid bodies can increase sympathetic tone.

Answer

Muscle relaxant dose requirements are increased in smokers.

Answer

Smoking decreases surfactant levels.

Question 4

Atropine as preanesthesia has all effects except?

Accepted Answer

Bronchoconstriction

Answer

Decrease secretion

Answer

Prevent bradycardia

Answer

Prevent hypotension

Question 5

According to AHA/American College of Cardiology guidelines, which of the following is NOT considered surgery with high risk in patients with known coronary artery disease?

Accepted Answer

Carotid endarterectomy

Answer

Emergency surgery

Answer

Peripheral vascular surgery

Answer

Aortic aneurysm surgery

Question 6

Which of the following is used as a preanesthetic medication?

Accepted Answer

Glycopyrrolate

Answer

Propanthelene

Answer

Ipratropium bromide

Answer

Hyoscine

Question 7

A 2-year-old child is scheduled for elective tonsillectomy and adenoidectomy. The mother reports the child has a runny nose. In which of the following situations would you proceed with the surgery?

Accepted Answer

Child is having bilateral bronchial breath sounds

Answer

Child is afebrile

Answer

Child is not actively wheezing

Answer

Child is alert and feeding normally

Question 8

Which drugs can interfere with anesthesia?

Accepted Answer

All of the above

Answer

Calcium channel blocker nifedipine

Answer

Beta blockers

Answer

Aminoglycosides

Question 9

A 50-year-old diabetic and hypertensive patient on amlodipine and glimepiride is scheduled for elective AV fistula creation for dialysis due to acute kidney failure. What are the appropriate preoperative orders from an anesthesiologist's perspective?

Accepted Answer

Continue amlodipine, stop glimepiride, and switch to insulin a day prior.

Answer

Stop amlodipine but continue glimepiride.

Answer

Stop both amlodipine and glimepiride.

Answer

Administer insulin and schedule surgery for one week later.

Question 10

What is the dose of atropine for premedication per kilogram of body weight?

Accepted Answer

0.01 mg

Answer

10 mg

Answer

0.1 mg

Answer

0.001 mg

Preoperative Evaluation and Management — MCQs

Preoperative Evaluation and Management — MCQs

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