Allergic Reactions to Local Anesthetics — MCQs
Which among the following is an example of type I hypersensitivity reaction?
A cardiovascular parameter helpful in diagnosis of anaphylaxis during anaesthesia:
A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?
A patient presented with rigidity, tremors, and trismus after being administered an anesthetic agent. Which anesthetic agent is most likely to have been administered?
Which of the following drugs produces dissociative anesthesia?
In ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?
What is the pathophysiological mechanism behind the increased risk of pelvic inflammatory disease with intrauterine device (IUD) insertion?
What will be the Glasgow Coma Scale (GCS) score for a head injury patient who opens eyes to painful stimulus, uses inappropriate words, and localizes pain?
Patient following peanut consumption presented with laryngeal edema, stridor, hoarseness of voice and swelling of tongue. Most likely diagnosis is:
A drug used to prevent niacin-induced flushing is
Allergic Reactions to Local Anesthetics Indian Medical PG Practice Questions and MCQs
Question 1: Which among the following is an example of type I hypersensitivity reaction?
- A. Graves' disease
- B. Pernicious anemia
- C. Arthus reaction
- D. Casoni's test (Correct Answer)
Explanation: ***Casoni's test*** - Casoni's test is a **diagnostic skin test** for **hydatid disease** (echinococcosis), involving intradermal injection of **hydatid cyst fluid antigen**. - A positive reaction produces an **immediate wheal and flare response** (within 15-30 minutes), which is a classic manifestation of **Type I hypersensitivity** mediated by **IgE antibodies** and **mast cell degranulation** [1], [2]. - Among the given options, Casoni's test is the correct answer because it **demonstrates/elicits** a Type I hypersensitivity reaction as part of its diagnostic mechanism. *Arthus reaction* - The Arthus reaction is a localized **Type III hypersensitivity** reaction caused by pre-formed IgG antibodies forming **immune complexes** with antigens injected intracutaneously. - It results in **vasculitis**, **edema**, **necrosis**, and **erythema** at the injection site, typically appearing **3-8 hours** after antigen exposure (delayed, not immediate). *Graves' disease* - Graves' disease is an **autoimmune disorder** causing **hyperthyroidism**, due to **stimulatory autoantibodies** (TSI - thyroid-stimulating immunoglobulins) against the **TSH receptor** [1]. - It is classified as a **Type II hypersensitivity** reaction, where antibodies bind to cell surface receptors leading to abnormal cell stimulation rather than destruction [1]. *Pernicious anemia* - Pernicious anemia is a **Type II hypersensitivity** reaction where autoantibodies target **intrinsic factor** or **gastric parietal cells**, leading to **vitamin B12 malabsorption** and subsequent megaloblastic anemia. - This antibody-mediated destruction or interference with normal cell function is characteristic of Type II hypersensitivity. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-213. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 171-172.
Question 2: A cardiovascular parameter helpful in diagnosis of anaphylaxis during anaesthesia:
- A. Bradycardia
- B. Dysrhythmia
- C. Increased peripheral vascular resistance
- D. Hypotension (Correct Answer)
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.
Question 3: A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?
- A. Malignant hyperthermia (Correct Answer)
- B. Halothane hepatitis
- C. Neuroleptic malignant syndrome
- D. Anaphylaxis
Explanation: ***Malignant hyperthermia*** - **Masseter muscle rigidity** following exposure to **succinylcholine** and a **halogenated inhalational anesthetic** (like halothane) is a hallmark sign of malignant hyperthermia. - This inherited disorder results in uncontrolled **calcium release** from the sarcoplasmic reticulum in skeletal muscle, leading to hypermetabolism, severe muscle contraction, and a rapid rise in body temperature. *Halothane hepatitis* - This is an idiosyncratic liver injury that can occur hours to days after exposure to halothane, not an acute intraoperative event causing muscle stiffness. - Symptoms include elevated liver enzymes, jaundice, and often fever, but without the immediate muscle rigidity seen here. *Neuroleptic malignant syndrome* - This condition is associated with the use of **antipsychotic medications** and presents with muscle rigidity, fever, altered mental status, and autonomic instability. - It does not involve exposure to succinylcholine or inhalational anesthetics and has a slower onset, typically over days. *Anaphylaxis* - Anaphylaxis is a severe, acute allergic reaction characterized by **bronchospasm**, **hypotension**, **urticaria**, and angioedema. - While it can manifest rapidly during anesthesia, it does not typically cause severe, generalized muscle stiffness as the primary symptom.
Question 4: A patient presented with rigidity, tremors, and trismus after being administered an anesthetic agent. Which anesthetic agent is most likely to have been administered?
- A. Halothane (Correct Answer)
- B. Nitrous Oxide (N2O)
- C. Thiopentone sodium
- D. Etomidate
Explanation: ***Halothane*** - The combination of **rigidity**, **tremors**, and **trismus** after an anesthetic agent suggests **malignant hyperthermia (MH)**, a rare but life-threatening inherited condition. - **Halothane (and other volatile anesthetics)**, along with succinylcholine, are known triggers for malignant hyperthermia. *Nitrous Oxide (N2O)* - While an anesthetic agent, **nitrous oxide** is not a known trigger for **malignant hyperthermia**. - It works by modulating **NMDA receptors** and does not typically cause rigidity, tremors, or trismus as a side effect. *Thiopentone sodium* - **Thiopentone sodium** is a **barbiturate** anesthetic and is not associated with triggering **malignant hyperthermia**. - Its effects primarily involve potentiation of **GABA-A receptors**, leading to sedation and hypnosis. *Etomidate* - **Etomidate** is a short-acting intravenous anesthetic that is not a known trigger for **malignant hyperthermia**. - It is typically associated with minimal cardiovascular depression but can cause **adrenocortical suppression** with prolonged use.
Question 5: Which of the following drugs produces dissociative anesthesia?
- A. Ketamine (Correct Answer)
- B. Propofol
- C. Thiopentone
- D. Enflurane
Explanation: ***Ketamine*** - **Ketamine** is a **dissociative anesthetic** that causes a trance-like state characterized by profound analgesia, amnesia, and catatonia, with the patient appearing to be awake but unresponsive. - It works by antagonizing the **NMDA receptor**, leading to a functional dissociation between the limbic and cortical systems. *Propofol* - **Propofol** is a short-acting intravenous anesthetic that produces a rapid loss of consciousness and has sedative-hypnotic properties. - It functions primarily by enhancing the activity of the **GABA-A receptor**, leading to central nervous system depression, not dissociation. *Thiopentone* - **Thiopentone** (Thiopental) is a barbiturate that induces rapid anesthesia and is used for induction and short procedures. - Its mechanism involves potentiation of the **GABA-A receptor**, causing global central nervous system depression without dissociative effects. *Enflurane* - **Enflurane** is an inhaled halogenated ether anesthetic that provides excellent muscle relaxation and analgesia. - It primarily acts by enhancing **GABAergic inhibition** and inhibiting excitatory neurotransmission, producing general anesthesia rather than a dissociative state.
Question 6: In ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?
- A. Procaine
- B. Cocaine
- C. Prilocaine (Correct Answer)
- D. Tetracaine
Explanation: **Local anesthetics are classified into two chemical groups: esters (aminoesters) and amides. Allergies to esters typically do not cross-react with amides.** ***Prilocaine*** - **Prilocaine** is an **amide-type local anesthetic**, and allergies to **aminoesters** typically do not cross-react with **amides**. - It is a safe alternative in patients with a known allergy to **ester-type local anesthetics**. *Cocaine* - **Cocaine** is an **ester-type local anesthetic**, sharing a similar chemical structure with **aminoesters**. - Patients allergic to **aminoesters** are likely to experience a **cross-reaction** with **cocaine**. *Procaine* - **Procaine** is a classic **ester-type local anesthetic** (an aminoester). - An allergy to aminoesters directly implies an allergy to **procaine** due to its chemical classification. *Tetracaine* - **Tetracaine** is also an **ester-type local anesthetic** (an aminoester). - It is contraindicated in patients with an allergy to **aminoesters** due to the high risk of **allergic reaction**.
Question 7: What is the pathophysiological mechanism behind the increased risk of pelvic inflammatory disease with intrauterine device (IUD) insertion?
- A. Inhibition of local immune responses by copper
- B. Introduction of vaginal bacteria during insertion procedure (Correct Answer)
- C. Direct trauma to endometrial tissue
- D. Enhancement of bacterial adhesion by IUD string
Explanation: ***Introduction of vaginal bacteria during insertion procedure*** - The **insertion process itself** can introduce bacteria from the vagina and cervix into the uterine cavity, leading to an **ascending infection**. - This risk is primarily associated with the **first 2-3 weeks post-insertion**, after which the risk significantly decreases and is not directly related to the IUD's presence. *Inhibition of local immune responses by copper* - **Copper IUDs** actually induce a **local inflammatory response** in the endometrium, which is part of their contraceptive mechanism. - This inflammation helps to prevent sperm survival and ovum implantation, rather than inhibiting immune responses. *Direct trauma to endometrial tissue* - While insertion can cause minor trauma, this **trauma itself does not directly cause PID** but rather provides a potential entry point for bacteria if disinfection protocols are not meticulously followed. - The risk of infection is primarily from the introduction of bacteria rather than the tissue damage. *Enhancement of bacterial adhesion by IUD string* - Although the **IUD string** could theoretically serve as a pathway for bacteria, studies have not definitively shown it to be a significant independent risk factor for PID beyond the initial insertion period. - The primary risk factor is the **bacterial translocation during the insertion procedure**, not ongoing bacterial ascent via the string.
Question 8: What will be the Glasgow Coma Scale (GCS) score for a head injury patient who opens eyes to painful stimulus, uses inappropriate words, and localizes pain?
- A. 10 (Correct Answer)
- B. 14
- C. 8
- D. 12
Explanation: ***10*** - The patient opens eyes to **painful stimulus (E2)**, uses **inappropriate words (V3)**, and **localizes pain (M5)**. - Summing these scores: **E2 + V3 + M5 = 10**. - This represents a **moderate head injury** (GCS 9-12). *14* - This score would require higher functioning in multiple domains. - Would need responses such as opening eyes to **speech (E3)**, **confused conversation (V4)**, and **localizing or obeying commands (M5-M6)**. - The described patient's responses do not reach this level of function. *8* - A GCS of **8 or less** indicates **severe head injury** requiring immediate **airway protection and intubation**. - The patient's ability to **localize pain (M5)** and use **inappropriate words (V3)** indicates a consciousness level above severe injury threshold. - This patient does not meet criteria for severe head injury. *12* - This score would require better responses in at least two categories. - Could include: opening eyes to **speech (E3)**, **confused conversation (V4)**, or **obeying commands (M6)**. - The patient's specified responses (E2 + V3 + M5) sum to only 10, not 12.
Question 9: Patient following peanut consumption presented with laryngeal edema, stridor, hoarseness of voice and swelling of tongue. Most likely diagnosis is:
- A. Foreign body bronchus
- B. Angioneurotic edema (Correct Answer)
- C. Foreign body larynx
- D. Pharyngeal abscess
Explanation: ***Angioneurotic edema*** - The rapid onset of **laryngeal edema**, **stridor**, **hoarseness**, and **tongue swelling** following peanut consumption points to an allergic reaction, specifically **anaphylaxis** causing angioedema [1], [2]. - This is a life-threatening condition due to potential **airway obstruction**. *Foreign body bronchus* - While a foreign body could cause **stridor** if large enough to impact the trachea, symptoms like **laryngeal edema** and **tongue swelling** are not typical. - It usually presents with sudden coughing, wheezing, and possibly dyspnea, often without rapid-onset, diffuse swelling. *Foreign body larynx* - A foreign body in the larynx might cause hoarseness and stridor, but **laryngeal edema** and **tongue swelling** are not primary features of a simple foreign body obstruction. - The history of peanut ingestion and rapid systemic inflammatory response makes an allergic reaction more likely [2]. *Pharyngeal abscess* - A pharyngeal abscess typically develops more slowly, with symptoms including **severe sore throat**, **fever**, and **difficulty swallowing**. - It would not usually present with the rapid onset of severe **laryngeal edema** and **tongue swelling** immediately after peanut consumption.
Question 10: A drug used to prevent niacin-induced flushing is
- A. Dexamethasone
- B. Aspirin (Correct Answer)
- C. Paracetamol
- D. Cetirizine
Explanation: ***Aspirin*** - Niacin-induced flushing is mediated by **prostaglandins**, primarily prostaglandin D2 (PGD2), which cause vasodilation. - **Aspirin**, being a non-steroidal anti-inflammatory drug (NSAID) and a cyclooxygenase (COX) inhibitor, blocks the synthesis of prostaglandins, thereby reducing flushing. *Cetirizine* - Cetirizine is a **second-generation H1 antihistamine** primarily used to treat allergic symptoms like rhinitis or urticaria. - It does not significantly affect prostaglandin pathways implicated in niacin-induced flushing. *Dexamethasone* - Dexamethasone is a **corticosteroid** with potent anti-inflammatory and immunosuppressive effects. - While it can broadly reduce inflammation, it is not the primary or most appropriate treatment for niacin-induced flushing, which is better managed with prostaglandin inhibitors. *Paracetamol* - Paracetamol (acetaminophen) is an **analgesic and antipyretic** that works primarily by inhibiting prostaglandin synthesis in the central nervous system. - It has minimal anti-inflammatory effects and does not effectively reduce peripheral prostaglandin production responsible for niacin flush.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free