Clinical sciences for MRCP Part 1

Minutes after eating a takeaway containing peanuts, a 25-year-old man develops widespread urticaria, swelling of his lips and tongue, wheeze and stridor, and becomes hypotensive with a systolic of 80 mmHg. He is anxious and short of breath. What is the most likely diagnosis?

1. Septic shock Distributive shock from infection, slower in onset. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it a consideration.
2. Vasovagal syncope A faint with bradycardia and quick recovery. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger raises it.
3. Anaphylaxis correct Correct. Sudden urticaria, angioedema, wheeze and hypotension within minutes of peanuts is anaphylaxis.
4. Angioedema without anaphylaxis Swelling without airway or circulatory collapse. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger points elsewhere.
5. Scombroid poisoning A histamine reaction from spoiled fish mimicking it. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger redirects it.

The point: Anaphylaxis is a severe, life-threatening, generalised hypersensitivity reaction, most often an IgE-mediated type I reaction in which allergen cross-links mast-cell and basophil IgE, triggering massive release of histamine and other mediators. It develops rapidly, usually within minutes of exposure to a trigger such as foods (nuts, shellfish), drugs (antibiotics, especially penicillins, and NSAIDs), insect stings or latex. The diagnosis is clinical: a sudden onset with rapidly progressing Airway, Breathing or Circulation problems (stridor and swelling, wheeze and hypoxia, or hypotension and collapse), usually with skin and mucosal changes such as urticaria and angioedema, though skin changes can be absent. The single most important treatment is intramuscular adrenaline into the anterolateral thigh (0.5 mg of 1 in 1000 in an adult), given immediately and repeated after 5 minutes if there is no improvement; delay in giving adrenaline is the commonest avoidable factor in fatal anaphylaxis. Alongside this the patient is positioned (lying flat with legs raised if hypotensive, sitting up if breathing is the problem), given high-flow oxygen and intravenous fluids for hypotension, and the trigger removed. Antihistamines and steroids are no longer first-line and, if used at all, are secondary to adrenaline. A serum mast-cell tryptase, taken during and after the reaction, supports the diagnosis retrospectively. After recovery, patients are observed for a biphasic reaction, prescribed adrenaline auto-injectors with training, and referred to an allergy clinic to identify the trigger. Anaphylaxis illustrates the core immunology of type I hypersensitivity that MRCP tests in clinical sciences.

Source: Resuscitation Council UK — emergency treatment of anaphylaxis guideline Resuscitation Council UK · tier 2, specialty society or college

Minutes after eating a takeaway containing peanuts, a 25-year-old man develops widespread urticaria, swelling of his lips and tongue, wheeze and stridor, and becomes hypotensive with a systolic of 80 mmHg. He is anxious and short of breath. What is the most appropriate investigation?

1. Serial serum mast-cell tryptase Supports the diagnosis retrospectively. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it confirmatory.
2. Clinical recognition of sudden ABC compromise with a trigger correct Correct. Anaphylaxis is a clinical diagnosis from sudden airway, breathing or circulation compromise with a trigger.
3. Allergy clinic referral and testing To confirm the allergen. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it thorough.
4. Observation for a biphasic reaction Because symptoms can recur. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it a safety step.
5. Monitoring of oxygenation and blood pressure To track severity. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it supportive.

The point: Anaphylaxis is a severe, life-threatening, generalised hypersensitivity reaction, most often an IgE-mediated type I reaction in which allergen cross-links mast-cell and basophil IgE, triggering massive release of histamine and other mediators. It develops rapidly, usually within minutes of exposure to a trigger such as foods (nuts, shellfish), drugs (antibiotics, especially penicillins, and NSAIDs), insect stings or latex. The diagnosis is clinical: a sudden onset with rapidly progressing Airway, Breathing or Circulation problems (stridor and swelling, wheeze and hypoxia, or hypotension and collapse), usually with skin and mucosal changes such as urticaria and angioedema, though skin changes can be absent. The single most important treatment is intramuscular adrenaline into the anterolateral thigh (0.5 mg of 1 in 1000 in an adult), given immediately and repeated after 5 minutes if there is no improvement; delay in giving adrenaline is the commonest avoidable factor in fatal anaphylaxis. Alongside this the patient is positioned (lying flat with legs raised if hypotensive, sitting up if breathing is the problem), given high-flow oxygen and intravenous fluids for hypotension, and the trigger removed. Antihistamines and steroids are no longer first-line and, if used at all, are secondary to adrenaline. A serum mast-cell tryptase, taken during and after the reaction, supports the diagnosis retrospectively. After recovery, patients are observed for a biphasic reaction, prescribed adrenaline auto-injectors with training, and referred to an allergy clinic to identify the trigger. Anaphylaxis illustrates the core immunology of type I hypersensitivity that MRCP tests in clinical sciences.

Source: Resuscitation Council UK — emergency treatment of anaphylaxis guideline Resuscitation Council UK · tier 2, specialty society or college

Minutes after eating a takeaway containing peanuts, a 25-year-old man develops widespread urticaria, swelling of his lips and tongue, wheeze and stridor, and becomes hypotensive with a systolic of 80 mmHg. He is anxious and short of breath. What is the most appropriate management?

1. Repeat adrenaline after 5 minutes if no improvement For ongoing reaction. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it standard.
2. Antihistamines and steroids only as secondary measures Not first-line. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it evidence-based.
3. High-flow oxygen and intravenous fluids For hypoxia and hypotension. Sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger makes it supportive.
4. Prescribe adrenaline auto-injectors with training and allergy referral After recovery, auto-injectors with training and allergy referral prevent and prepare for future episodes, and sudden urticaria, angioedema, wheeze and hypotension within minutes of a food trigger here points elsewhere.
5. Immediate intramuscular adrenaline into the anterolateral thigh correct Correct. Immediate intramuscular adrenaline into the thigh is the single most important treatment.

The point: Anaphylaxis is a severe, life-threatening, generalised hypersensitivity reaction, most often an IgE-mediated type I reaction in which allergen cross-links mast-cell and basophil IgE, triggering massive release of histamine and other mediators. It develops rapidly, usually within minutes of exposure to a trigger such as foods (nuts, shellfish), drugs (antibiotics, especially penicillins, and NSAIDs), insect stings or latex. The diagnosis is clinical: a sudden onset with rapidly progressing Airway, Breathing or Circulation problems (stridor and swelling, wheeze and hypoxia, or hypotension and collapse), usually with skin and mucosal changes such as urticaria and angioedema, though skin changes can be absent. The single most important treatment is intramuscular adrenaline into the anterolateral thigh (0.5 mg of 1 in 1000 in an adult), given immediately and repeated after 5 minutes if there is no improvement; delay in giving adrenaline is the commonest avoidable factor in fatal anaphylaxis. Alongside this the patient is positioned (lying flat with legs raised if hypotensive, sitting up if breathing is the problem), given high-flow oxygen and intravenous fluids for hypotension, and the trigger removed. Antihistamines and steroids are no longer first-line and, if used at all, are secondary to adrenaline. A serum mast-cell tryptase, taken during and after the reaction, supports the diagnosis retrospectively. After recovery, patients are observed for a biphasic reaction, prescribed adrenaline auto-injectors with training, and referred to an allergy clinic to identify the trigger. Anaphylaxis illustrates the core immunology of type I hypersensitivity that MRCP tests in clinical sciences.

Source: Resuscitation Council UK — emergency treatment of anaphylaxis guideline Resuscitation Council UK · tier 2, specialty society or college