Respiratory Pharmacology, Diuretics, and Intravenous Fluids — WACS Viva & Clinical Scenarios (Pharmacology and Applied Pharmacology)

Exam-style respiratory pharmacology, diuretics, and intravenous fluids viva scenarios with examiner probes and model answers for ANAESTHESIA candidates.

Scenarios covered

• SCENARIO 1: A 30-year-old known asthmatic woman undergoing emergency laparotomy for a ruptured ectopic pregnancy develops sudden severe bronchospasm immediately after tracheal intubation and surgical incision. Peak inspiratory pressures rise to 48 cmH₂O, the capnograph demonstrates an upsloping shark-fin waveform, and SpO₂ falls from 99% to 86%. Detail your immediate pharmacological and ventilatory management to reverse this life-threatening airway crisis.
• SCENARIO 2: A 60-year-old man with end-stage renal disease and severe congestive cardiac failure presents with acute pulmonary oedema and severe volume overload. The surgical team plans an emergency incision and drainage of an extensive perineal necrotizing fasciitis. Explain the clinical pharmacology of loop diuretics, their site of action, ceiling effect, resistance mechanisms, and your anaesthetic strategy for optimizing fluid status and myocardial function.
• SCENARIO 3: A 24-year-old male unrestrained driver involved in a road traffic collision presents in haemorrhagic shock class III and a severe closed head injury with a Glasgow Coma Scale score of 7. The junior doctor begins rapid resuscitation with 3 litres of 0.9% normal saline. Provide a detailed critical analysis of the physiological and pharmacological consequences of large-volume 0.9% saline infusion, compare this with balanced crystalloids and colloids, and formulate a targeted resuscitation plan.
• SCENARIO 4: A 48-year-old male with acute respiratory distress syndrome (ARDS) secondary to severe peritonitis is ventilated in the intensive care unit. His PaO₂/FiO₂ ratio is 110 mmHg, and echocardiography demonstrates acute cor pulmonale with severe pulmonary hypertension. Explain the pharmacology, mechanisms of selective pulmonary vasodilation, delivery methods, and safety considerations of inhaled prostacyclins, sildenafil, and intravenous inodilators in this critical care setting.