Chemical Path, Long Answer and Short Answer OmpathStudy

--- SECTION 1: SODIUM DISORDERS Long Essay Question Question 1.1 A 72-year-old man with a history of chronic obstructive pulmonary disease (COPD) is admitted with pneumonia. He is started on intravenous antibiotics. On day 3 of admission, he becomes increasingly confused and drowsy. Laboratory investigations reveal: Serum Sodium: 118 mmol/L Serum Potassium: 4.1 mmol/L Serum Urea: 3.2 mmol/L Serum Creatinine: 68 μmol/L Serum Osmolality: 248 mOsm/kg Urine Sodium: 45 mmol/L Urine Osmolality: 520 mOsm/kg a) What is the primary electrolyte abnormality and classify its severity? (2 marks) b) Based on the clinical presentation and laboratory findings, what is the most likely diagnosis? Explain the pathophysiology. (5 marks) c) Discuss the principles of management for this condition, including rate of correction and potential complications of inappropriate treatment. (8 marks) --- Short Answer Questions Question 1.2 A 45-year-old woman on lithium therapy presents with confusion. Her serum sodium is 158 mmol/L. a) Name two causes of hypernatremia in this patient. (2 marks) b) What is the formula to calculate free water deficit? (1 mark) c) State two neurological complications of rapid correction. (2 marks) --- Question 1.3 List four causes of hyponatremia with: a) Low serum osmolality (2 marks) b) Normal serum osmolality (pseudohyponatremia) (2 marks) --- SECTION 2: POTASSIUM DISORDERS Long Essay Question Question 2.1 A 58-year-old woman with type 2 diabetes and hypertension presents to the emergency department with progressive muscle weakness over 48 hours. She is on metformin, ramipril, and spironolactone. She recently started NSAIDs for osteoarthritis. Laboratory results: Serum Potassium: 7.2 mmol/L Serum Creatinine: 245 μmol/L (baseline 95 μmol/L) Serum Bicarbonate: 18 mmol/L ECG: Tall peaked T waves, widened QRS complexes a) What is the electrolyte disorder and classify its severity? (2 marks) b) Explain THREE mechanisms contributing to hyperkalemia in this patient. (6 marks) c) Outline the emergency management of this condition, including specific treatments and their mechanisms of action. (7 marks) --- Short Answer Questions Question 2.2 A patient with severe diarrhea has a serum potassium of 2.3 mmol/L. a) List three ECG changes associated with hypokalemia. (3 marks) b) Name two factors that affect the distribution of potassium between intracellular and extracellular compartments. (2 marks) --- Question 2.3 a) What is the transcellular shift? Give two examples of conditions causing potassium to shift into cells. (3 marks) b) Calculate the potassium deficit in a 70 kg patient with serum K+ of 2.5 mmol/L (assume normal is 4.0 mmol/L). (2 marks) --- SECTION 3: ACID-BASE DISORDERS Long Essay Question Question 3.1 A 19-year-old woman with known type 1 diabetes mellitus presents to the emergency department with a 2-day history of nausea, vomiting, and abdominal pain. She admits to missing her insulin injections. On examination, she is dehydrated, has deep rapid breathing (Kussmaul respiration), and her breath has a fruity odor. Arterial blood gas: pH: 7.12 PaCO₂: 22 mmHg PaO₂: 95 mmHg HCO₃⁻: 8 mmol/L Base Excess: -18 mmol/L Biochemistry: Serum Glucose: 28 mmol/L Serum Sodium: 132 mmol/L Serum Potassium: 5.8 mmol/L Serum Chloride: 98 mmol/L Serum Creatinine: 145 μmol/L Serum Ketones: 5.2 mmol/L a) Interpret the arterial blood gas results and identify the primary acid-base disorder. Is there appropriate respiratory compensation? (4 marks) b) Calculate the anion gap and explain its significance in this case. (4 marks) c) Discuss the pathophysiology of diabetic ketoacidosis and outline the principles of management. (7 marks) --- Short Answer Questions Question 3.2 A patient's arterial blood gas shows: pH 7.50, PaCO₂ 48 mmHg, HCO₃⁻ 36 mmol/L. a) Identify the primary acid-base disorder. (1 mark) b) List three possible causes of this disorder. (3 marks) c) What is the expected respiratory compensation for a primary metabolic alkalosis? (1 mark) --- Question 3.3 a) Define the anion gap and provide the formula for its calculation. (2 marks) b) List four causes of high anion gap metabolic acidosis. (2 marks) c) What is the difference between type A and type B lactic acidosis? (1 mark) --- Question 3.4 A patient with chronic kidney disease has the following results:pH 7.32, PaCO₂ 38 mmHg, HCO₃⁻ 18 mmol/L a) What is the primary disorder? (1 mark) b) Use Winter's formula to determine if respiratory compensation is appropriate. (2 marks) c) Name the type of renal tubular acidosis most commonly seen in CKD. (2 marks) --- SECTION 4: CALCIUM DISORDERS Long Essay Question Question 4.1 A 68-year-old woman presents with fatigue, constipation, polyuria, and confusion. She has a history of recurrent renal stones. Physical examination reveals band keratopathy. Laboratory investigations: Serum Calcium (corrected): 3.2 mmol/L Serum Phosphate: 0.7 mmol/L Serum Alkaline Phosphatase: 85 U/L (normal) Serum Albumin: 38 g/L Serum PTH: 125 pg/mL