Time-based charting of physiological variables allows trends in these vital signs to be seen Fig 1.

Pre-induction values should be recorded for comparison. Pulse, BP ETCO2 and oxygen saturation are core vital signs. The Royal College of Anaesthetists (RCoA) guidelines state that these vital signs should be recorded at least every 10 minutes and the Association of Anaesthetists of Great Britain and Ireland (AAGBI) suggest they should be recorded no less than every five minutes.

Blood loss may need to be recorded if excessive or out of proportion to the surgery.