tailieunhanh - Ebook Primary FRCA: OSCEs in Anaesthesia – Part 2

Part 2 book “Primary FRCA: OSCEs in Anaesthesia” has contents: Anaesthetic hazards, blood transfusion, lumbar puncture, cardiovascular examination, bradyarrhythmia, collapsedobst etricpatient, malignant hyperthermia, failed intubation, and other contents. | Section 5 Anaesthetic hazards Chapter 1. Electricity 5 The philosopher Wittgenstein once wrote ‘whereof one cannot speak, thereof remain silent’; however, Wittgenstein never had to sit the Primary FRCA. Here you need to say something sensible even if you do not really know. Hazard symbols are easy to examine but tedious to learn. It is highly unlikely you will be presented with an entire station on hazards but they may well be scattered among the relevant clinical stations. Questions 1. What are the potentially harmful effects of electric current passing through the body? 2. What is the frequency of mains (AC) current? 3. What magnitude of mains current is required to produce: (a) Pain (b) Muscle contraction (c) Ventricular fibrillation (VF) 4. What is ‘microshock’? 5. How do we prevent shocks in the theatre setting? 6. What do these safety symbols represent? 119 Section 5: Anaesthetic hazards – Electricity Answers 1. Electrocution and death, burns (resistors heat up when current flows across them), electrochemical effects (excitable tissues such as muscle or nerves can be stimulated) and ignition of flammable materials (. alcoholic skin preparation). 2. Mains electricity is at 50Hz in the UK (60Hz in the US). 3. The magnitudes of current required are as follows: Pain 5 mA Muscle contraction 15–20 mA Ventricular fibrillation 100 mA 4. Microshock occurs when medical devices that have electrodes in or around the heart (. a Swan-Ganz catheter) are utilised and a current can potentially pass directly to the heart. Here a current as low as 100 μA can cause VF. 5. Most shocks occur as a result of unwanted current returning to earth through the patient; thus safety strategies are devised to minimise this occurrence. The options are: (a) an isolating transformer either for the whole of the theatre or integrated into each electrical device, and (b) current-operated earth-leakage circuit breaker (better known in homes around the nation as a residual current