Treatment of Acute Contrast Reactions — MCQs
Which of the following contrast agents is PREFERRED in a patient with renal dysfunction for the prevention of contrast-induced nephropathy?
Acute allergic reaction to the penicillin group of drugs is classified as:
What is the Investigation of Choice (IOC) for Acute Aortic Dissection?
To obtain adequate diagnostic imaging in a morbidly obese patient, what modification to X-ray technique is most important?
Contrast media of choice for a myelogram is
Which of the following is a non-ionic contrast agent?
All of the following dyes are water soluble except:
What is the first-line fluid to be administered in a patient presenting with acute hemorrhagic shock?
A patient with leprosy had slightly erythematous, anesthetic plaques on the trunk and upper limbs. He was treated with paucibacillary multidrug therapy (PB-MDT) for 6 months. At the end of 6 months, he had persistent erythema and induration in the plaque. The next step of action recommended by the World Health Organization (WHO) in such a patient is:
A 39-year-old man is undergoing resuscitation with blood products for an upper GI bleed. He is suspected of having a hemolytic transfusion reaction. Which of the following is appropriate in the management of this patient?
Treatment of Acute Contrast Reactions Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following contrast agents is PREFERRED in a patient with renal dysfunction for the prevention of contrast-induced nephropathy?
- A. Iso-osmolar contrast (Correct Answer)
- B. High osmolar contrast
- C. Ionic contrast
- D. Low osmolar contrast
Explanation: ***Iso-osmolar contrast*** - **Iso-osmolar contrast agents** (e.g., iodixanol) have an osmolality of ~290 mOsm/kg, which is identical to that of plasma. - **This is the PREFERRED choice** in patients with renal dysfunction as multiple studies demonstrate the lowest risk of contrast-induced nephropathy (CIN). - The iso-osmolar formulation minimizes osmotic stress on renal tubules and reduces the risk of acute kidney injury. - **Current guidelines recommend iso-osmolar agents as first-line** in high-risk patients with pre-existing renal impairment. *Low osmolar contrast* - **Low osmolar contrast agents** have osmolality of 600-900 mOsm/kg, which is significantly lower than high osmolar agents but still 2-3 times higher than plasma. - While **acceptable and safer than high osmolar agents**, they are not as optimal as iso-osmolar contrast for patients with renal dysfunction. - These agents are widely used and represent a reasonable alternative when iso-osmolar agents are not available. *High osmolar contrast* - **High osmolar contrast agents** have osmolality >1400 mOsm/kg (about 5 times that of plasma). - They carry the **highest risk of contrast-induced nephropathy** due to severe osmotic load and direct tubular toxicity. - **Contraindicated or strongly avoided** in patients with pre-existing renal dysfunction. *Ionic contrast* - **Ionic contrast** refers to the chemical structure (dissociates into ions) rather than osmolality. - Can be either high or low osmolar—the ionic nature alone does not determine renal safety. - The critical factor for nephrotoxicity prevention is osmolality, not ionic charge.
Question 2: Acute allergic reaction to the penicillin group of drugs is classified as:
- A. Type 1 reaction (Correct Answer)
- B. Type 2 reaction
- C. Type 3 reaction
- D. Type 4 reaction
Explanation: ***Type 1 reaction*** - Penicillin allergy is a classic example of a **Type I hypersensitivity reaction**, mediated by **IgE antibodies**. - Symptoms like **anaphylaxis**, **urticaria**, and **angioedema** develop rapidly upon re-exposure to the drug. *Type 2 reaction* - **Type II hypersensitivity reactions** involve **IgG** or **IgM antibodies** binding to antigens on cell surfaces, leading to cell destruction. - Examples include **hemolytic anemia** due to drug-induced antibodies, which is not the primary mechanism of typical penicillin allergy. *Type 3 reaction* - **Type III hypersensitivity reactions** involve the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues. - This can lead to conditions like **serum sickness** or **vasculitis**, which are less common manifestations of penicillin allergy. *Type 4 reaction* - **Type IV hypersensitivity reactions** are **delayed-type hypersensitivity (DTH)** reactions, mediated by **T cells** rather than antibodies. - These reactions typically manifest 24-72 hours after exposure, as seen in **contact dermatitis**; while some penicillin reactions can be T-cell mediated, the acute, life-threatening allergic response is Type I.
Question 3: What is the Investigation of Choice (IOC) for Acute Aortic Dissection?
- A. USG
- B. Doppler
- C. CT-Angio (Correct Answer)
- D. MR-Angio
Explanation: ***CT-angio*** - **Computed tomography angiography (CTA)** is considered the **gold standard** imaging modality for diagnosing acute aortic dissection due to its rapid acquisition, wide availability, and excellent visualization of the aorta and its branches. - It precisely demonstrates the **intimal flap**, true and false lumens, and assesses the extent of the dissection and involvement of major branch vessels. *Usg* - **Ultrasound (USG)**, specifically **transesophageal echocardiography (TEE)**, is highly sensitive and specific for proximal aortic dissections. - However, its utility is operator-dependent and it has limitations in visualizing the entire aorta, especially the distal descending aorta. *Doppler* - **Doppler ultrasound** is used to assess blood flow velocity and patterns within vessels. - While it can detect flow disturbances, it is not the primary imaging modality for diagnosing the anatomical extent and characteristics of an aortic dissection flap. *Mr-Angio* - **Magnetic resonance angiography (MRA)** provides excellent soft tissue contrast, no radiation exposure, and detailed anatomical information for aortic dissection. - However, it is often less accessible, time-consuming, and contraindicated in patients with certain metallic implants or claustrophobia, making it less ideal for an acute emergency setting compared to CTA.
Question 4: To obtain adequate diagnostic imaging in a morbidly obese patient, what modification to X-ray technique is most important?
- A. Increase MAS
- B. Decrease KVP
- C. Increase KVP (Correct Answer)
- D. Decrease MAS
Explanation: ***Increase KVP*** - Increasing the **kilovoltage peak (KVP)** is essential for imaging morbidly obese patients because it increases the **penetrating power** of the X-ray beam, allowing adequate transmission through thick body tissues. - Higher KVP (typically 90-120 kVp range) ensures the X-ray beam can penetrate increased soft tissue thickness and reach the image receptor with sufficient intensity. - While higher KVP produces **longer scale (lower) contrast**, it is necessary for adequate **penetration** in obese patients - without sufficient KVP, the image would be underexposed and non-diagnostic. - In practice, both KVP and MAS are increased for obese patients, but **KVP increase is more critical** for penetration. *Increase MAS* - Increasing **milliampere-seconds (MAS)** increases the quantity of X-ray photons and image density (brightness), which is also helpful for obese patients. - However, MAS alone without adequate KVP cannot solve the penetration problem - the photons would still be too low energy to penetrate thick tissues effectively. - MAS increase without KVP increase would result in high patient dose with poor image quality. *Decrease KVP* - Decreasing KVP reduces **beam penetration**, which would be catastrophic for imaging an obese patient. - The X-ray beam would be absorbed by superficial tissues, resulting in a severely **underexposed** and non-diagnostic image. - While lower KVP produces higher contrast in theory, it is completely inappropriate for thick body parts. *Decrease MAS* - Decreasing MAS reduces the number of X-ray photons, resulting in an **underexposed, lighter** image. - This would make it even more difficult to obtain adequate imaging through increased body mass, resulting in a non-diagnostic radiograph with excessive quantum mottle.
Question 5: Contrast media of choice for a myelogram is
- A. Urografin 75%
- B. Conray 470
- C. Biligrafin
- D. Iohexol (Correct Answer)
Explanation: ***Iohexol*** - **Iohexol** is a **non-ionic, low osmolality contrast medium** that is widely considered the contrast agent of choice for myelography due to its safety profile. - It has a lower incidence of neurotoxicity and adverse systemic reactions compared to older ionic contrast agents, making it suitable for direct injection into the **subarachnoid space**. *Urografin 75%* - **Urografin** contains **diatrizoate meglumine and sodium**, which are **ionic contrast agents**. - While suitable for intravenous urography, **ionic contrast agents are generally contraindicated for myelography** due to a higher risk of neurotoxicity, including seizures and arachnoiditis, when injected into the cerebrospinal fluid. *Conray 470* - **Conray 470** contains **iothalamate meglumine**, another **ionic contrast medium**. - Similar to Urografin, its **high osmolality and ionic nature** make it unsuitable for intrathecal administration for myelography, as it can cause significant neurotoxic effects. *Biligrafin* - **Biligrafin** is an **ionic, high osmolality contrast medium** primarily designed for **cholangiography**, typically administered intravenously to visualize the biliary tree. - It is **not used for myelography** due to its neurotoxicity risks and formulation, which is not intended for intrathecal injection.
Question 6: Which of the following is a non-ionic contrast agent?
- A. Amidotrizoate
- B. Iothalamate
- C. Ioxoglate
- D. Iohexol (Correct Answer)
Explanation: ***Iohexol*** - **Iohexol** is a well-known example of a **non-ionic, low osmolar contrast agent**. It's widely used due to its lower incidence of adverse reactions compared to ionic agents. - Non-ionic contrast agents remain as **intact molecules** in solution and do not dissociate into charged ions, contributing to their lower osmolality and better tolerability. *Amidotrizoate* - **Amidotrizoate** (also known as diatrizoate) is an **ionic, high osmolar contrast agent**. It dissociates into two ions in solution. - Due to its high osmolality, it is associated with a higher risk of adverse effects, such as **nausea**, **vomiting**, and **nephrotoxicity**. *Iothalamate* - **Iothalamate** is another example of an **ionic, high osmolar contrast agent**. It also dissociates into charged ions when dissolved. - Its use has decreased significantly with the development of safer non-ionic alternatives due to its higher potential for **adverse drug reactions**. *Ioxoglate* - **Ioxoglate** is a **dimeric, ionic contrast agent**. Although it's ionic, it has a lower osmolality than monomeric ionic agents due to its dimeric structure. - Despite being dimeric, it still dissociates into ions, distinguishing it from truly non-ionic compounds like iohexol.
Question 7: All of the following dyes are water soluble except:
- A. Myodil (Correct Answer)
- B. Iohexol
- C. Conray 420
- D. Metrizamide
Explanation: ***Myodil*** - **Myodil** (Iophendylate) is an **oil-based** contrast medium previously used for myelography. - Due to its **oil-based nature**, it is not water-soluble and had to be removed after the procedure to prevent complications. *Iohexol* - **Iohexol** is a **non-ionic, water-soluble** contrast agent commonly used in various radiological procedures, including myelography. - Its water solubility allows for easy absorption and excretion from the body. *Conray 420* - **Conray 420** (Iothalamate meglumine) is an **ionic, water-soluble** contrast agent often used for angiography and urography. - It readily mixes with bodily fluids due to its water-soluble properties. *Metrizamide* - **Metrizamide** was an early **non-ionic, water-soluble** contrast agent specifically developed for myelography. - Although water-soluble, it had a higher incidence of neurotoxicity compared to newer agents like iohexol.
Question 8: What is the first-line fluid to be administered in a patient presenting with acute hemorrhagic shock?
- A. PRBC
- B. Crystalloid (Correct Answer)
- C. Colloid
- D. Whole blood
Explanation: ***Crystalloid*** - Initial fluid resuscitation in **hemorrhagic shock** prioritizes **crystalloids** (e.g., normal saline or lactated Ringer's) to restore intravascular volume rapidly and maintain perfusion. - This approach is based on their immediate availability, cost-effectiveness, and ability to expand the extracellular fluid compartment. *PRBC* - While **packed red blood cells (PRBCs)** are crucial for replacing oxygen-carrying capacity in significant hemorrhage, they are typically administered *after* or *concurrently* with initial crystalloid resuscitation once the need for blood products is established. - Administering PRBCs as the *first-line* fluid might delay volume expansion and could be less effective for initial circulatory support. *Colloid* - **Colloid solutions** (e.g., albumin, dextran) remain controversial in initial hemorrhagic shock resuscitation due to concerns about their cost, potential side effects, and lack of clear superiority over crystalloids in improving patient outcomes. - They are also not as readily available as crystalloids in all emergency settings. *Whole blood* - **Whole blood** is the ideal resuscitation fluid as it contains all components of blood but is generally not readily available for initial emergency resuscitation in most civilian settings. - Its use is often limited to specific trauma centers or military combat scenarios due to logistical challenges.
Question 9: A patient with leprosy had slightly erythematous, anesthetic plaques on the trunk and upper limbs. He was treated with paucibacillary multidrug therapy (PB-MDT) for 6 months. At the end of 6 months, he had persistent erythema and induration in the plaque. The next step of action recommended by the World Health Organization (WHO) in such a patient is:
- A. Continue dapsone alone for another 6 months
- B. Stop antileprosy treatment (Correct Answer)
- C. Continue PB-MDT till erythema subsides
- D. Biopsy the lesion to document activity
Explanation: ***Stop antileprosy treatment*** - According to WHO guidelines, once a patient with **paucibacillary (PB) leprosy** has completed the full 6-month course of PB-MDT, treatment should be stopped, regardless of residual signs or symptoms. - Persistent erythema and induration after completing the prescribed regimen often indicate **post-treatment inflammation** or residual scarring, not necessarily ongoing bacterial activity. *Continue dapsone alone for another 6 months* - **Monotherapy** with dapsone is not recommended for residual lesions after Multi-Drug Therapy (MDT) for leprosy due to the risk of **drug resistance**. - WHO guidelines clearly state that MDT for PB leprosy is a **fixed-duration treatment** (6 months) and single-drug therapy is not an acceptable follow-up. *Continue PB-MDT till erythema subsides* - Extending MDT beyond the recommended 6 months for PB leprosy is **not indicated** and does not provide additional benefits. - Doing so exposes the patient to **unnecessary drug toxicity** and contributes to non-adherence due to longer treatment duration. *Biopsy the lesion to document activity* - While a biopsy could show residual inflammation, it is **not the recommended next step** by WHO for persistent erythema after completing PB-MDT. - The focus is on **clinical resolution** and adherence to fixed-duration treatment regimens, rather than seeking pathological confirmation of activity unless there is strong evidence of relapse.
Question 10: A 39-year-old man is undergoing resuscitation with blood products for an upper GI bleed. He is suspected of having a hemolytic transfusion reaction. Which of the following is appropriate in the management of this patient?
- A. Fluids and mannitol (Correct Answer)
- B. Removal of nonessential foreign body irritants, for example, Foley catheter
- C. 0.1 M HCl infusion
- D. Fluid restriction
Explanation: ***Fluids and mannitol*** - **Aggressive intravenous fluids** are crucial to maintain renal perfusion and prevent acute kidney injury by flushing out free hemoglobin [1]. - **Mannitol** is an osmotic diuretic that promotes renal excretion of hemoglobin and prevents tubular obstruction; it should be used cautiously to avoid fluid overload [1]. *Removal of nonessential foreign body irritants, for example, Foley catheter* - While **infection control** is generally important, removing a Foley catheter is not a primary or direct intervention for managing a **hemolytic transfusion reaction**. - A Foley catheter actually assists in monitoring **urine output**, which is critical for assessing renal function during a hemolytic transfusion reaction [1]. *0.1 M HCl infusion* - **Hydrochloric acid (HCl) infusion** would cause severe **acidosis** and is not indicated in the management of a hemolytic transfusion reaction. - The focus is on **maintaining blood pressure**, **renal perfusion**, and addressing potential **coagulopathy**, not altering systemic pH with strong acids. *Fluid restriction* - **Fluid restriction** would be detrimental in a patient with a hemolytic transfusion reaction, as it can worsen **hypovolemia**, **renal hypoperfusion**, and accelerate acute kidney injury. - **Aggressive fluid hydration** is essential to help excrete hemolyzed products and maintain kidney function [1].
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free