Electrical Safety, Diathermy, Defibrillators, and Environmental Hazards — WACS Viva & Clinical Scenarios (Physics in Anaesthesia)

Exam-style electrical safety, diathermy, defibrillators, and environmental hazards viva scenarios with examiner probes and model answers for ANAESTHESIA…

Scenarios covered

• SCENARIO 1: A 55-year-old male with a temporary transvenous pacing wire in situ is admitted to the intensive care unit. While adjusting an infusion pump connected to the same electrical multi-socket outlet as the pacing console, the patient suddenly develops ventricular fibrillation. Explain the physics of microshock versus macroshock, state the current thresholds capable of triggering ventricular fibrillation in each, and describe the physical classification of electrical equipment (Type B, BF, and CF) designed to prevent this disaster.
• SCENARIO 2: In a modern teaching hospital operating suite, the Line Isolation Monitor (LIM) alarm sounds with a digital reading of 4.5 mA during an ongoing spine surgery involving multiple electrical warmers, suction units, and electrosurgical generators. Explain the physical principles of an isolated power supply (IPS) and line isolation monitor, assess whether the patient or staff are in immediate danger of electrocution, and describe the systematic physical troubleshooting steps.
• SCENARIO 3: A 62-year-old female with an implantable cardioverter-defibrillator (ICD) is scheduled for an open cholecystectomy where extensive monopolar diathermy will be used. Explain the physical differences between cutting and coagulation waveforms in diathermy, explain how high-frequency current avoids exciting nerve and muscle tissue, describe how monopolar current interferes with an ICD, and outline physical precautions including plate placement.
• SCENARIO 4: During an elective laser excision of vocal cord papillomas under general anaesthesia with 50% oxygen and 50% nitrous oxide, a sudden flash and black smoke erupt from the oral cavity. Outline the physics of the operating theatre fire triad in this situation, explain why nitrous oxide acts as an oxidiser, and detail the immediate step-by-step physical and airway management protocol.