Standard induction

• During standard induction, we give a bolus of a short-acting opioid and propofol, usually dosed according to body weight
• After assessing loss of consciousness (LOC), we will administer muscle relaxants for intubation

TIVA induction

• We recommend slowly titrating up the target propofol concentration to observe the Ce when LOC happens, this will give us an idea of how sensitive to the anaesthesia our patient is
• The size of the initial target and the steps of increase can vary according to the perceived sensitivity to anaesthesia, with smaller steps for more sensitive patients
• We usually start with a target of 0.5 – 1 mcg/ml and stepping up 0.5 – 1 mcg/ml each time
• Depending on your plan for airway manipulation, propofol requirements may need to be titrated upwards to obtund the stimulation especially if your airway plan involves less opioid or without relaxants
• Infusion rates with TCI propofol are much slower than standard bolus propofol induction, but the patient will lose consciousness at roughly the same predicted effect-site concentration
  • This is because the time to peak effect for propofol is much slower than for example, thiopentone
  • The quick loss of consciousness we see with standard induction is because the dose we give will cause a huge overshoot in the plasma concentration to drive up the effect-site concentration quickly
  • With TCI propofol infusion, a more gentle induction is possible with less of the side effects such as haemodynamic instability caused by the overshooting.

Caveats for a quicker induction:

• Use effect-site targeting instead of plasma site targeting
• Make sure all the dead space between the propofol infusion line and IV access is primed with propofol and consider a running drip
• Begin propofol infusion as early as possible
• Some TCI pumps will give you the bolus dose when an initial target infusion is being set, this can be adjusted to your desired bolus should a quick induction is deemed necessary

Caution

• Change in the patient usually lags the calculation on the pump because it assumes instant distribution which is not the case in real life