Anaes SAQs · Measurement & monitoring physics

Electricity fundamentals and electrical safety

Primary — Ohm's law V=IR; macroshock (whole-body via skin, VF threshold greater than 100 mA, AC more dangerous than DC); microshock (direct cardiac contact via catheter/pacemaker wire, VF threshold 100 microamperes = 0.1 mA, 1000 times lower); electrical safety (earthing diverts fault to ground, fuse breaks at excess current, RCD trips at 5-30 mA leakage, isolated/floating circuit means single fault cannot complete circuit through patient); diathermy high-frequency AC 400 kHz to 4 MHz (no muscle stimulation at high freq), monopolar (return plate) vs bipolar (between forceps); surgical fire triangle (ignition + oxidiser + fuel).