Contrast Media and Reactions

Contrast Media and Reactions Indian Medical PG Question 1: Drug of choice for beta antagonist toxicity is?

• A. Adrenaline
• B. Glucagon (Correct Answer)
• C. ACE inhibitors
• D. Dopamine

Contrast Media and Reactions Explanation: ***Glucagon*** - **Glucagon** is the drug of choice for **beta-blocker overdose** because it bypasses the beta-adrenergic receptors and directly activates **adenylate cyclase** to increase intracellular cAMP [1]. - This action leads to increased heart rate and myocardial contractility, counteracting the cardiac depression caused by beta-blockers [1]. *Adrenaline* - **Adrenaline** (epinephrine) is a beta-agonist, but its effects are blunted in severe **beta-blocker overdose** due to **competitive antagonism** at beta receptors. - While it can be used for its alpha-agonist effects to increase blood pressure, its efficacy in reversing profound bradycardia and myocardial depression may be limited. *ACE inhibitors* - **ACE inhibitors** are used in the management of hypertension and heart failure, primarily by reducing **angiotensin II** formation and inhibiting **bradykinin** degradation. - They have no direct role in reversing the immediate cardiovascular effects of **beta-antagonist toxicity**. *Dopamine* - **Dopamine** is a **catecholamine** with dose-dependent effects, including positive inotropy and chronotropy at higher doses, but it relies on **adrenergic receptor activation**. - Its effects can be attenuated in **beta-blocker overdose**, similar to adrenaline, making it less effective than glucagon as first-line therapy.

Contrast Media and Reactions Indian Medical PG Question 2: First line therapy in anaphylactic shock is:

• A. Epinephrine .5 ml of 1:1000 IM (Correct Answer)
• B. Atropine 3 mg intravenously
• C. Adenosine 12 mg intravenously
• D. Epinephrine 1 ml of 1:10000 intravenously

Contrast Media and Reactions Explanation: ***Epinephrine .5 ml of 1:1000 IM*** - **Epinephrine** is the **first-line treatment** for anaphylaxis due to its alpha-1 agonist effects (vasoconstriction, which increases blood pressure) and beta-2 agonist effects (bronchodilation, which improves breathing). [1] - The recommended dose and concentration for intramuscular administration in adults is **0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) IM**, repeated every 5-15 minutes as needed. *Atropine 3 mg intravenously* - **Atropine** is an anticholinergic medication used to treat **bradycardia** or organophosphate poisoning, not anaphylaxis. [4] - It does not address the widespread vasaodilation or bronchoconstriction seen in anaphylactic shock. *Adenosine 12 mg intravenously* - **Adenosine** is an antiarrhythmic drug primarily used to convert **supraventricular tachycardia (SVT)** to normal sinus rhythm. [3] - It has no role in the management of anaphylactic shock. *Epinephrine 1 ml of 1:10000 intravenously* - While epinephrine is the correct drug, **intravenous administration** of epinephrine 1:10,000 is typically reserved for **cardiac arrest** [2] or in cases of severe, refractory anaphylaxis under expert care, and carries a higher risk of adverse effects. - The initial and preferred route for anaphylaxis is **intramuscular**, as it provides rapid absorption with lower risks compared to IM administration.

Contrast Media and Reactions Indian Medical PG Question 3: 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

Contrast Media and Reactions 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.

Contrast Media and Reactions Indian Medical PG Question 4: A cardiovascular parameter helpful in diagnosis of anaphylaxis during anaesthesia:

• A. Bradycardia
• B. Dysrhythmia
• C. Increased peripheral vascular resistance
• D. Hypotension (Correct Answer)

Contrast Media and Reactions Explanation: ***Hypotension*** - **Hypotension** is a hallmark cardiovascular sign of anaphylaxis, occurring due to widespread **vasodilation** and increased vascular permeability. - This symptom is often profound and unresponsive to initial fluid resuscitation due to the ongoing systemic release of inflammatory mediators. *Bradycardia* - While bradycardia can occur in some rare cases of anaphylaxis (e.g., **vasovagal response**), **tachycardia** is the more common cardiac response due to compensatory mechanisms. - It is not a primary or consistent indicator of anaphylaxis, making it less helpful for diagnosis in this context. *Dysrhythmia* - **Dysrhythmias** can occur during anaphylaxis due to myocardial ischemia or electrolyte imbalances, but they are not a direct or consistent diagnostic feature. - Their presence often reflects severe compromise or co-existing conditions rather than being a primary anaphylactic sign. *Increased peripheral vascular resistance* - Anaphylaxis is characterized by a significant **decrease in peripheral vascular resistance** due to mast cell and basophil degranulation releasing vasodilatory mediators like histamine. - Therefore, an increase in peripheral vascular resistance would contradict the pathophysiology of anaphylaxis.

Contrast Media and Reactions Indian Medical PG Question 5: Which of the following is NOT a characteristic feature of anaphylactic shock?

• A. Angioedema
• B. Urticarial rash
• C. Pedal edema (Correct Answer)
• D. Flushing

Contrast Media and Reactions Explanation: ***Pedal edema*** - While **edema** can occur in anaphylaxis due to increased vascular permeability, **pedal edema** (swelling primarily in the lower extremities) is not a defining characteristic or a primary life-threatening feature of anaphylactic shock. - Anaphylactic shock primarily manifests with systemic symptoms like **hypotension**, **bronchospasm**, and widespread **urticaria** or **angioedema**, rather than isolated peripheral swelling [1], [3]. *Angioedema* - **Angioedema** is a common and often serious feature of anaphylaxis, involving swelling of deeper layers of the skin and mucous membranes [1]. - It can affect the **lips**, **face**, **throat**, and **airway**, potentially leading to airway obstruction [3]. *Urticarial rash* - An **urticarial rash**, or **hives**, is a hallmark cutaneous manifestation of anaphylaxis, characterized by itchy red welts [2]. - It is caused by the release of histamine and other mediators that increase capillary permeability, leading to fluid leakage into the skin [2], [3]. *Flushing* - **Flushing** is a common early symptom of anaphylaxis, characterized by sudden redness and warmth of the skin [1]. - It results from widespread **vasodilation** caused by mediator release, such as histamine [3].

Contrast Media and Reactions Flashcard 1 of 5

Question: _____ monomers (Advantage) form better images in IVP and have anticoagulant property

Answer: Ionic

Contrast Media and Reactions Flashcard 2 of 5

Question: _____ has Iodine: particle ratio of 3:1

Answer: Non-ionic monomer

Contrast Media and Reactions Flashcard 3 of 5

Question: _____ has osmolarity of 300 mOsm (Iso-osmolar).

Answer: Non-ionic Dimer

Contrast Media and Reactions Flashcard 4 of 5

Question: Iodinated Contrast media: _____ monomer has Iodine: particle ratio of 3:2.

Answer: Ionic

Contrast Media and Reactions Flashcard 5 of 5

Question: Iodinated contrast media: While, _____ has only 1 particle and ionic has 2 charged particles.

Answer: non-ionic