Clinical monitoring

Clinical monitoring of the depth of anaesthesia relies on the presence of autonomic reflexes:

• ophthalmic:
  • pupil size, reducing with increasing depth, but may dilate in very deep anaesthesia
  • opioids and anticholinergics alter pupil size by a central action and so make this index less valid
• cardiovascular:
  • the trend in heart rate and arterial blood pressure is followed
  • it may be modified by drugs, haemorrhage and body fluid abnormalities
• respiratory:
  • the trend in rate, depth and rhythmicity of breathing
  • effect of ventilation
  • hiccuping or bronchospasm may indicate light anaesthesia
• skin:
  • sweating can be a sign of light anaesthesia; reduced by anticholinergic agents
  • colour; good perfusion indicated by pink hue
  • capillary refill time; an indirect index of tissue perfusion
  • temperature; particularly important in infants