Standard monitoring (aagbi standards)

Why standard monitoring matters

• Monitoring is about early detection of problems (hypoxia, hypotension, arrhythmia, hypoventilation) before harm occurs.
• AAGBI standards describe the minimum monitoring expected for any patient receiving anaesthesia and most sedation where airway/ventilation could be affected.
• Monitoring does not replace clinical observation: look at the patient, the airway, chest movement, skin colour, and the surgical field.
• If a monitor is unavailable or not working, you should pause and fix/replace it or escalate—do not “carry on and hope”.

Core principle: oxygenation, ventilation, circulation, temperature

• Oxygenation: pulse oximetry (SpO2) with an audible tone and alarms on.
• Ventilation: capnography (end-tidal CO2) whenever an airway device is used and whenever ventilation could be depressed (including many sedations).
• Circulation: non-invasive blood pressure (NIBP) and ECG; assess pulse quality and perfusion clinically.
• Temperature: measure and actively manage temperature for cases where hypothermia is likely (most general anaesthetics >30 minutes, major surgery, neuraxial with exposure, paediatrics, trauma).

Minimum monitoring for general anaesthesia (typical baseline set)

• Pulse oximeter (SpO2) with audible pulse tone and appropriate alarm limits.
• ECG (usually 3-lead; consider 5-lead if ischaemia risk or major surgery).
• NIBP at regular intervals (commonly every 3–5 minutes; more frequently if unstable).
• Capnography (ETCO2) for any patient with a tracheal tube, supraglottic airway, mask ventilation, or where ventilation is assisted/controlled.
• Inspired oxygen concentration (FiO2) monitoring when using an anaesthetic machine/ventilator.
• Airway pressure and ventilator parameters (tidal volume, minute ventilation) when ventilated.
• Temperature monitoring when clinically indicated (often most GA cases).

Sedation: when you must treat it like an anaesthetic

• If sedation might cause airway obstruction, hypoventilation, or loss of verbal contact, monitoring should approach GA standards.
• Pulse oximetry and NIBP are expected for most sedations; ECG is common depending on patient risk and depth of sedation.
• Capnography is strongly recommended for moderate/deep sedation and whenever ventilation may be impaired (e.g., opioids, propofol, high-risk patients, endoscopy).
• Have oxygen, suction, airway equipment, and trained help immediately available; plan how you will rescue the airway if sedation deepens.

Regional / neuraxial anaesthesia (spinal/epidural/blocks)

• Even without GA, neuraxial techniques can cause hypotension and bradycardia—monitor circulation closely.
• Minimum: SpO2, NIBP, and ECG during initiation and for an appropriate period afterwards; continue until stable.
• If sedation is added, escalate monitoring (including capnography if ventilation may be affected).
• Keep communication with the patient: symptoms like nausea, dizziness, or “feeling faint” can be early signs of hypotension.

Before you start: set-up and alarm discipline

• Check monitors are powered, connected, and displaying a plausible trace/value before induction or sedation.
• Set alarm limits appropriate to the patient (e.g., tighter BP limits for severe aortic stenosis; lower SpO2 alarm may be inappropriate in most patients).
• Do not silence alarms without addressing the cause; if you must mute briefly, keep it short and re-enable.
• Make sure the pulse oximeter tone is audible to the whole team (it is an early warning for desaturation and loss of pulse).

Capnography: practical interpretation for new starters

• Capnography confirms ventilation and airway patency; it is the fastest way to detect oesophageal intubation, disconnection, or apnea.
• A sudden loss of ETCO2 trace: think DISCONNECT / EXTUBATION / APNEA / OBSTRUCTION; check patient first, then circuit.
• A rising ETCO2: think hypoventilation, increased CO2 production (fever, shivering), rebreathing, exhausted soda lime (if applicable).
• A low ETCO2: think hyperventilation, low cardiac output, pulmonary embolism, major leak.

Blood pressure monitoring: frequency and escalation

• Set NIBP cycling at least every 5 minutes during anaesthesia; shorten interval if unstable, induction, major blood loss, or high-risk patient.
• If NIBP is unreliable (arrhythmia, tremor, poor perfusion) or rapid changes are expected, consider arterial line early and ask for help.
• Always interpret BP in context: check pulse, capillary refill, ETCO2 trend, surgical losses, and depth of anaesthesia.

Temperature: prevention is easier than treatment

• Hypothermia increases bleeding, wound infection risk, and delays recovery; it is common early in GA due to redistribution.
• Use active warming early (forced-air warming, warmed fluids) and monitor core temperature when indicated.
• Be cautious with warming in patients with impaired sensation or poor perfusion; avoid burns by correct device use.

Recovery (PACU): monitoring continues

• Continue monitoring until the patient is awake enough, stable, and maintaining airway/ventilation and circulation reliably.
• Minimum typically includes SpO2, NIBP, and clinical observation; ECG as indicated by risk and intra-op events.
• After opioids, neuraxial opioids, or heavy sedation, watch for delayed respiratory depression—consider capnography if concerned and ensure appropriate staffing.
• Handover should include: airway device used, oxygen requirements, analgesia given, antiemetics, fluids/blood loss, complications, and specific concerns.