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Anaesthesia

Maintenance

Maintenance and depth

Keeping a patient asleep, still, pain-free and physiologically stable for as long as the surgeon needs, and knowing which of those four is failing when something changes.

Volatile or intravenous

Volatile agents give you an end-tidal number that correlates with depth, which is a real safety feature. Total intravenous anaesthesia gives a smoother emergence with less nausea and is mandatory in malignant hyperthermia susceptibility. Both are correct; the choice follows the patient and the case.

Minimum alveolar concentration

The end-tidal concentration at which half of patients do not move to a standard stimulus. It falls with age, opioids, nitrous oxide, hypothermia and illness, and rises in children and with chronic alcohol use. Age-adjusted MAC is the number that matters, not the textbook one.

Reading the patient, not the vaporiser

Tachycardia and hypertension during surgery may be light anaesthesia, inadequate analgesia, hypercapnia, hypovolaemia or a full bladder. The reflex to turn up the vapour treats one of five possibilities. Look at the capnograph, the surgical field and the fluid balance before you reach for the dial.

Awareness

Rare, and devastating when it happens. Risk concentrates in paralysed patients on light anaesthesia: cardiac surgery, obstetrics, trauma, and any total intravenous technique where the line tissues without anyone noticing. Depth monitoring is recommended for paralysed patients on intravenous anaesthesia, and a visible, running infusion site is worth more than any monitor.

Watch it done