Intraoperative Monitoring, Vigilance and Patient Safety
Monitoring items ask which monitor detects which physiological failure, and how human factors cause harm. Capnography interpretation, oximetry limitations and the WHO checklist carry the most marks.
Mandatory standards
- Continuous pulse oximetry, capnography, ECG, non-invasive blood pressure, temperature, inspired and expired gas analysis, and ventilator alarms for every general anaesthetic.
- Capnography is mandatory to confirm and monitor tracheal tube position, and during propofol sedation.
- Arterial line for beat-to-beat pressure and sampling where non-invasive readings are unreliable (obesity, arrhythmia); CVP is not a routine measure of volume responsiveness.
Waveform reading
- Sudden EtCO₂ to zero: disconnection, extubation, oesophageal intubation or circuit leak - never dismiss as artefact.
- 'Shark-fin' upslope: bronchospasm or obstructive pattern; rising baseline: exhausted soda lime or rebreathing.
- Oximetry fails in poor perfusion and motion, and is misleading in methaemoglobinaemia (SpO₂ near 85%) and carboxyhaemoglobinaemia (falsely normal).
Safety science
- The WHO surgical safety checklist reduces morbidity; handover failure and alarm fatigue are recognised contributors to critical incidents.
- Report incidents through the local system and disclose harm to the patient.
Worked example
During laparoscopy, EtCO₂ falls from 35 to 8 mmHg while SpO₂ stays 99%. Oxygenation is intact but ventilation must be verified: check tube position, the capnography trace and the circuit. A flat trace with a moving chest suggests sampling-line disconnection; pulmonary embolism would typically lower but not abolish EtCO₂, and would worsen oxygenation.
Traps
Relying on SpO₂ alone to exclude oesophageal intubation; treating exhausted CO₂ absorbent as bronchospasm; calling a low EtCO₂ hyperventilation when the sampling line is disconnected.