Paediatric TIVA

The curriculum asks for knowledge of the 'maintenance of anaesthesia for children aged 1 year and above', which I suppose includes TIVA.

Resources

Patient	Surgical	Procedural
Malignant hyperpyrexia risk	Airway surgery	Remote-site anaesthesia e.g. MRI
History of PONV	Shared airway procedures	Muscle biopsy for neuromuscular diagnosis
Prior emergence delirium	Neurosurgery	Patient transfer
History or suspicion of reactive airway e.g. URTI	Middle ear surgery
Fear of facemask/gas induction not possible	High-risk PONV
Muscular dystrophy	Neurophysiological monitoring

Advantages	Disadvantages
↓ airway reactivity & risk of laryngospasm/stridor	Pain on injection
Does not rely on the airway for anaesthetic delivery	Risk of PRIS
↓ risk of ambient pollution	Need for IV access
Improved ciliary function	Need for specialised infusion pumps
Preserved hypoxic pulmonary vasoconstriction	Risk of bacterial contamination
↓ PONV	Environmental waste (plastic, propofol)
↓ emergence delirium	No point-of-care propofol measurement system/reliance on pEEG
No interference with neurophysiological monitoring	Caution in obese due to accumulation
Overall ↓ costs	Disposables may be costly

There is pharmacokinetic and pharmacodynamic variability between different ages of paediatric patient owing to the effect of maturation on propofol metabolism
In neonates, ex-prem infants and the critically ill propofol TIVA should be used with caution owing to extremely variable propofol pharmacokinetics and non-linear changes in both VD and propofol clearance

Pharmacokinetic changes with age

Larger central compartment and volume of distribution in infants, which decrease to adult levels over time
There is greater clearance (peak at 1yr of age), which also decreases over time
This necessitates a higher bolus dose and maintenance rates in younger populations
In the obese, propofol induction doses are proportional to lean body mass but maintenance doses are linked to total body weight
The context-sensitive half-life in children is longer than in adults:

Propofol manual models

Both regimens target a plasma propofol concentration (Cp) of 3mcg/ml, which may be inadequate to provide suitable depth of anaesthesia in a paediatric population without adjuncts or additional 1mg/kg boluses of propofol

Propofol pharmacokinetic models

Paedfusor and Kataria models use plasma concentration targeting (Cpt), therefore should allow adequate equilibration between Cp and Ce before up/down-titrating

Remifentanil models

Safety

Affixed firmly to patient's skin
Use anaesthetist-inserted cannula rather one from the ward
Visible so that disconnection, leakage or 'tissued' cannula are readily detected
Check infusion site if pump alarms
Routine checking of cannula during long cases

Only use Luer lock syringes
Standard order of syringes in the pumps (to prevent erroneous up- or down-titration of the incorrect agent)
Remifentanil syringe only labelled after drug added
Anti-siphon valve on drug lines
Non-return valve on IV fluid line
Minimal dead space distal to agent mixing

Performance

Use lidocaine to avoid pain on induction
In general, a propofol concentration of approximately 4.5μg/ml gives a BIS of roughly 50
May need higher (e.g. 5 or 6μg/ml) if propofol is the sole agent used, or lower (~3μg/ml) if adjuncts are used