Anesthesia Equipment, Monitoring, and Instrumentation
Equipment is a system, not a collection of boxes
Know the anesthesia machine pathway: pipeline and cylinder gases, pressure regulators, fail-safe devices, flowmeters, vaporizers, fresh-gas outlet, breathing circuit, ventilator, CO2 absorber, and scavenging. Understand low-pressure versus high-pressure leaks, check valves, and oxygen failure alarms. Monitoring: capnography is mandatory for intubation and ventilation; pulse oximetry detects hypoxemia late in the cascade; ECG leads are not all equivalent; arterial and central lines require zeroing and understanding of dynamic response. Neuromuscular monitoring requires supramaximal stimulation and a baseline.
Traps: an absent capnogram can be disconnection, esophageal intubation, obstruction, or cardiac arrest-not automatically tube in esophagus. A normal oxygen saturation may persist briefly during apnea. Vaporizer interlock prevents two agents but does not prevent misfilling. CO2 absorbent exhaustion causes delayed hypercapnia; channeling and desiccation can produce carbon monoxide or compound A concerns. Never silence an alarm without identifying its cause.
Worked example: sudden EtCO2 falls from 38 to 8 mmHg with a flat waveform. Check circuit connection, tracheal tube position, and blood pressure; if the patient is pulseless, begin CPR. If the waveform is present but low, consider hyperventilation, low cardiac output, or embolism.
Rule of thumb: before anesthetizing, perform a structured machine check and ask whether you can ventilate, oxygenate, and rescue this patient if everything fails.