Preoperative Laboratory Testing Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Preoperative Laboratory Testing. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Preoperative Laboratory Testing Indian Medical PG Question 1: In the immediate postoperative period, how is body potassium typically managed?
- A. Increased due to fluid retention
- B. Remains stable
- C. Excreted excessively (Correct Answer)
- D. Conserved by aldosterone action
Preoperative Laboratory Testing Explanation: ***Excreted excessively***
- **Stress responses** to surgery, including increased aldosterone and cortisol, can lead to enhanced **potassium excretion** via the kidneys.
- Additionally, cell breakdown and fluid shifts can contribute to a net loss of potassium from the **intracellular** to **extracellular** space.
*Increased due to fluid retention*
- While **fluid retention** can occur post-operatively, it's typically associated with **dilutional hyponatremia**, not hyperkalemia from increased body potassium.
- The stress response and associated hormonal changes usually promote potassium excretion, not retention.
*Remains stable*
- The **stress of surgery** significantly impacts electrolyte balance due to hormonal changes, fluid shifts, and tissue injury, making it unlikely for potassium levels to remain stable.
- **Aldosterone effects** and increased cortisol levels actively alter potassium handling.
*Conserved by aldosterone action*
- **Aldosterone**, a key hormone in the postoperative stress response, primarily promotes **sodium reabsorption** and **potassium excretion** in the kidneys.
- Therefore, its action leads to potassium loss rather than conservation.
Preoperative Laboratory Testing Indian Medical PG Question 2: In an accident case, after the arrival of medical team, all should be done in early management except;
- A. Glasgow coma scale
- B. Check BP (Correct Answer)
- C. Stabilization of cervical vertebrae
- D. Check Respiration
Preoperative Laboratory Testing Explanation: ***Check BP***
- In the **immediate/early management** of trauma (primary survey), while circulation assessment is crucial, the **initial assessment of circulation** focuses on:
- **Pulse rate and quality** (radial, carotid)
- **Capillary refill time**
- **Skin color and temperature**
- **Active hemorrhage control**
- **Formal blood pressure measurement** with a cuff, while important, is typically recorded during or after these rapid initial assessments, as it takes more time to obtain an accurate reading.
- In the context of this question, among the four options listed, BP measurement is relatively less immediate compared to the other life-saving priorities (airway protection, breathing assessment, C-spine stabilization, and GCS).
- **Note:** This is a nuanced distinction - BP is assessed during primary survey, but the other three options have more immediate life-threatening implications if not addressed.
*Glasgow coma scale*
- **GCS assessment** is part of the **"D" (Disability)** step in the ATLS primary survey.
- It is performed early to assess neurological status and level of consciousness.
- GCS <8 indicates need for **definitive airway protection** (intubation).
- This is a critical early assessment that guides immediate management decisions.
*Stabilization of cervical vertebrae*
- **C-spine immobilization** is part of the **"A" (Airway)** step - "Airway with cervical spine protection."
- It is performed **simultaneously** with airway assessment using a **rigid cervical collar**.
- This is the **first priority** in trauma management to prevent secondary spinal cord injury.
- All trauma patients should be assumed to have C-spine injury until proven otherwise.
*Check Respiration*
- **Respiratory assessment** is part of the **"B" (Breathing)** step in the ATLS primary survey.
- This involves checking:
- **Respiratory rate and pattern**
- **Chest wall movement**
- **Air entry bilaterally**
- **Signs of tension pneumothorax or flail chest**
- This is an immediate life-saving priority and must be assessed early.
Preoperative Laboratory Testing Indian Medical PG Question 3: In a Down's syndrome patient posted for surgery, the necessary preoperative investigation to be done is –
- A. CT Brain
- B. X-ray cervical spine (Correct Answer)
- C. Ultrasound Abdomen
- D. Echocardiography
Preoperative Laboratory Testing Explanation: X-ray cervical spine
- Patients with Down syndrome have an increased risk of **atlantoaxial instability (AAI)** due to ligamentous laxity and bony abnormalities, which can lead to spinal cord compression during neck manipulation for intubation.
- A **preoperative X-ray of the cervical spine** (flexion/extension views) is crucial to assess for AAI and guide anesthetic management to prevent neurological damage.
*CT Brain*
- While some Down syndrome patients may have structural brain differences, a **CT brain** is not a routine preoperative investigation for all surgeries unless specific neurological symptoms are present.
- It is not primarily indicated for assessing the immediate surgical risks associated with conditions common in Down syndrome, such as atlantoaxial instability.
*Echocardiography*
- Many Down syndrome patients have congenital heart defects (e.g., **AV canal defects**), and an echocardiogram is essential to evaluate cardiac function and structure, especially for major surgeries.
- However, compared to the immediate risk of spinal cord injury during airway management, assessing **atlantoaxial instability** with a cervical spine X-ray takes precedence as a necessary and specific preoperative investigation for general surgery.
*Ultrasound Abdomen*
- Down syndrome patients have a higher incidence of certain gastrointestinal anomalies (e.g., **duodenal atresia**, Hirshsprung's disease) and often develop premature aging of organs.
- An **abdominal ultrasound** is not a standard preoperative screening test unless there are specific abdominal symptoms or indications for evaluating potential anomalies or complications.
Preoperative Laboratory Testing Indian Medical PG Question 4: In a comatose patient with a blood glucose level of 750 mg/dL, which test is most important to perform in addition to serum potassium?
- A. Serum creatinine
- B. Serum sodium
- C. Serum ketones
- D. Arterial blood gases (Correct Answer)
Preoperative Laboratory Testing Explanation: ***Arterial blood gases***
- In a comatose patient with severe hyperglycemia (750 mg/dL), **arterial blood gases (ABGs)** are crucial to assess for **acidosis**, which could indicate **diabetic ketoacidosis (DKA)** or **hyperosmolar hyperglycemic state (HHS)** with lactic acidosis [1], [4].
- The **pH**, **bicarbonate (HCO3-)**, and **pCO2** levels from ABGs help determine the severity and type of metabolic derangement, guiding immediate treatment, especially for potential **cerebral edema** [3], [4].
*Serum creatinine*
- While important for assessing **kidney function** in hyperosmolar states, it does not directly evaluate the immediate acid-base status that is critical for neurologic function in a comatose patient.
- Renal insufficiency can exacerbate electrolyte imbalances and fluid overload but is secondary to the immediate need for acid-base assessment.
*Serum sodium*
- **Serum sodium** is important for calculating **effective serum osmolality**, which is elevated in both DKA and HHS, contributing to mental status changes [2].
- However, while important, it does not provide information about the **acid-base balance**, which is a more critical determinant of immediate neurologic stability and treatment in deep coma.
*Serum ketones*
- **Serum ketones** are essential for distinguishing between **DKA** (high ketones) and **HHS** (low or absent ketones) [4].
- While vital for diagnosis, ketones alone do not give the full picture of **acid-base status** (pH, bicarbonate) which is directly assessed by ABGs and more immediately actionable in managing a severely ill, comatose patient [1].
Preoperative Laboratory Testing Indian Medical PG Question 5: Among the following, which test is essential in pre-treatment evaluation for lithium therapy:
- A. Fasting blood sugar
- B. Serum creatinine (Correct Answer)
- C. Liver function tests
- D. Platelet count
Preoperative Laboratory Testing Explanation: ***Serum creatinine***
- **Lithium** is almost entirely excreted by the kidneys, so baseline renal function assessed by **serum creatinine** and estimated glomerular filtration rate (eGFR) is crucial.
- This helps determine the appropriate starting dose and monitor for potential **lithium-induced renal impairment** during therapy.
*Fasting blood sugar*
- While important for general health screening and monitoring metabolic syndrome, **lithium** does not directly impact glucose metabolism to the extent that it requires pre-treatment evaluation for dosing or safety reasons.
- This test is not considered essential specifically for lithium pre-treatment.
*Liver function tests*
- **Lithium** is not metabolized by the liver, and **hepatotoxicity** is not a known side effect.
- Therefore, baseline liver function tests are not considered essential for initiating lithium therapy.
*Platelet count*
- **Lithium** rarely causes significant hematological abnormalities like **thrombocytopenia** or **thrombocytosis**.
- A baseline platelet count is generally not required for pre-treatment evaluation unless there are other clinical indications.
Preoperative Laboratory Testing Indian Medical PG Question 6: Preoperative medication of thyrotoxicosis are all except?
- A. Carbimazole
- B. PTU
- C. Propranolol
- D. Levothyroxine (Correct Answer)
Preoperative Laboratory Testing Explanation: Levothyroxine
- Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism, meaning it increases thyroid hormone levels, which would worsen thyrotoxicosis [1].
- Its administration would be contraindicated in a patient with thyrotoxicosis, as the goal is to reduce thyroid hormone levels preoperatively.
Carbimazole
- Carbimazole is a thionamide drug that inhibits the synthesis of thyroid hormones, making it a critical medication for treating hyperthyroidism and preparing patients for surgery [1].
- It reduces the amount of thyroid hormone produced by the thyroid gland, thus mitigating the risks associated with thyrotoxicosis during surgery.
PTU
- Propylthiouracil (PTU), like carbimazole, is a thionamide that blocks thyroid hormone synthesis and also inhibits the conversion of T4 to T3 [1].
- It is used in the preoperative management of thyrotoxicosis to achieve a euthyroid state and prevent a thyroid storm.
Propranolol
- Propranolol is a beta-blocker used to manage the symptoms of thyrotoxicosis, particularly the cardiovascular effects such as tachycardia, palpitations, and tremors [1].
- While it does not affect thyroid hormone levels directly, it helps control symptoms and stabilize the patient preoperatively, making them a safer candidate for surgery [1].
Preoperative Laboratory Testing Indian Medical PG Question 7: In the immediate postoperative period, body potassium is
- A. Retained in body
- B. Exchanged with magnesium
- C. Exchanged with calcium
- D. Excreted excessively (Correct Answer)
Preoperative Laboratory Testing Explanation: ***Excreted excessively***
- In the immediate postoperative period, the body often experiences **stress-induced hormonal changes**, such as increased cortisol and aldosterone, and activation of the **renin-angiotensin-aldosterone system**.
- These hormonal changes can lead to increased renal potassium excretion and **catabolism** of muscle tissue, releasing intracellular potassium which is then excreted.
*Retained in body*
- **Potassium retention** is typically seen in conditions like **renal failure** or in states of **hypoaldosteronism**, which are not characteristic of the immediate postoperative period.
- The stress response and potential for **acidosis** generally shift potassium out of cells, leading to increased excretion rather than retention.
*Exchanged with magnesium*
- While potassium and magnesium are both important intracellular cations and their levels can influence each other, a direct "exchange" in the immediate postoperative period is not the primary mechanism of potassium handling.
- **Hypomagnesemia** can impair potassium reabsorption leading to **hypokalemia**, but this is a secondary effect, not a direct exchange causing excessive excretion.
*Exchanged with calcium*
- There is no primary physiological mechanism for direct "exchange" of potassium with calcium in the context of general body fluid and electrolyte regulation in the immediate postoperative period.
- **Calcium and potassium** have different regulatory pathways and serve distinct roles, though imbalances in one can indirectly affect the other's transport or cellular function.
Preoperative Laboratory Testing Indian Medical PG Question 8: A patient scheduled for elective inguinal hernia surgery has a history of myocardial infarction (MI) and underwent coronary artery bypass grafting (CABG). What should be included in the preoperative assessment?
- A. History + c/e + routine labs + V/Q scan
- B. History + c/e + routine labs
- C. History + c/e + routine labs + stress test (Correct Answer)
- D. History + c/e + routine labs + angiography to assess graft patency
Preoperative Laboratory Testing Explanation: ***History + c/e + routine labs + stress test***
- A **stress test** is crucial in patients with a history of MI and CABG to assess **myocardial ischemia** and functional capacity, guiding perioperative management.
- This evaluation helps determine the patient's **cardiac risk** for non-cardiac surgery and the need for further cardiac optimization.
*History + c/e + routine labs + angiography to assess graft patency*
- **Coronary angiography** is an invasive procedure and is generally not indicated as a routine preoperative assessment unless there are new, significant cardiac symptoms or signs of **graft dysfunction**.
- Assessing graft patency through angiography carries risks and would only be justified if there were strong clinical indications suggesting acute or severe **cardiac ischemia**.
*History + c/e + routine labs*
- While critical for any preoperative assessment, **routine history, physical examination, and basic laboratory tests** are insufficient for a patient with a significant cardiac history like MI and CABG.
- This approach would **underestimate the cardiac risk** and might miss undetected ischemia, leading to adverse perioperative cardiac events.
*History + c/e + routine labs + V/Q scan*
- A **ventilation-perfusion (V/Q) scan** is primarily used to diagnose **pulmonary embolism** or assess regional lung function.
- It does not provide information about myocardial ischemia or cardiac functional capacity, making it **irrelevant** for assessing cardiac risk in this clinical scenario.
Preoperative Laboratory Testing Indian Medical PG Question 9: A 50 year old male is posted for elective laparoscopic cholecystectomy. No history of comorbidities. His surgery is scheduled at 2 PM on the day of surgery. Which of the following is against the ASA guidelines for preoperative fasting
- A. Water at 12:00 PM
- B. Black coffee at 5:30 AM
- C. Pancakes at 10:00 AM (Correct Answer)
- D. A non-clear liquid (e.g., orange juice) at 7:30 AM
Preoperative Laboratory Testing Explanation: **Pancakes at 10:00 AM**
- According to ASA guidelines, the fasting period for solid food is typically **6-8 hours** before surgery. Eating pancakes, which are solid food, at 10:00 AM for a 2:00 PM surgery (4-hour interval) violates this guideline.
- This short fasting period for solids increases the risk of **pulmonary aspiration** during induction of anesthesia.
*Water at 12:00 PM*
- Water is considered a clear liquid, and ASA guidelines typically allow clear liquids until **2 hours** before surgery. Drinking water at 12:00 PM for a 2:00 PM surgery is within these guidelines.
- Rapid gastric emptying of clear liquids minimizes the risk of aspiration.
*Black coffee at 5:30 AM*
- Black coffee is considered a clear liquid, and it is consumed well within the **2-hour** fasting window for clear liquids before a 2:00 PM surgery.
- The absence of milk or cream ensures it is treated as a clear liquid, which empties quickly from the stomach.
*A non-clear liquid (e.g., orange juice) at 7:30 AM*
- Non-clear liquids, such as orange juice, are treated similarly to light meals and generally require a fasting period of **6 hours** before surgery. Drinking orange juice at 7:30 AM for a 2:00 PM surgery (6.5-hour interval) is compliant with these guidelines.
- The protein and pulp in non-clear liquids delay gastric emptying compared to clear liquids.
Preoperative Laboratory Testing Indian Medical PG Question 10: Preanaesthetic medication glycopyrrolate is primarily used for:
- A. Decrease secretion (Correct Answer)
- B. Antisialagogue effect
- C. Prevent aspiration
- D. Reduce bronchial secretions
Preoperative Laboratory Testing Explanation: ***Decrease secretion***
- Glycopyrrolate is an **anticholinergic drug** that primarily works by blocking muscarinic acetylcholine receptors, thereby reducing glandular secretions throughout the body.
- This effect includes reducing **salivary**, **bronchial**, and **gastric secretions**, which is beneficial during anesthesia.
*Reduce bronchial secretions*
- While glycopyrrolate does **reduce bronchial secretions**, this is a specific aspect of its broader effect of decreasing secretions, making "decrease secretion" a more comprehensive answer.
- Reducing bronchial secretions helps in maintaining a **clear airway** and preventing atelectasis.
*Prevent aspiration*
- By decreasing gastric and salivary secretions, glycopyrrolate can indirectly help to **reduce the risk of aspiration** of gastric contents or saliva into the lungs.
- However, preventing aspiration is a beneficial **consequence** of reduced secretions, not the direct pharmacological action described as "decrease secretion."
*Antisialagogue effect*
- The **antisialagogue effect**, which means reducing saliva production, is a prominent action of glycopyrrolate and is part of its overall secretion-decreasing property.
- Reducing salivary secretions creates a **dry operative field** during procedures involving the oral cavity or airway.
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