Breaking down barriers

‘If you always do what you always did, you will always get what you always got’ – A. Einstein

It is time to break down these barriers, move out of our comfort zones and take a closer look closer at some of the frequently quoted reasons not to use TIVA. Our aim is after this week some of the myths will be banished for good.

Awareness

• NAP 5 looked at accidental awareness under general anaesthesia
• Accidental Awareness under General Anaesthesia (AAGA) was shown to be twice as likely in cases of TIVA than volatile anaesthetic
• This figure may not accurately reflect the actual risk posed to patients
• Many AAGA cases during TIVA involved the use of non-TCI techniques
  • Manual infusions
  • Fixed-rate infusions
  • Intermittent boluses
• Inadequate dosing using non-TCI regimens
• Conversion of a volatile anaesthetic to TIVA
• Transfer of paralysed patients outside theatres
• Outside theatres TCI infusions use was rare
• Inside of theatre failure to deliver the intended dose of propofol included
  • Disconnection
  • Tissued IV line
• Three-quarters of cases were considered preventable
• Further details of NAP 5 can be viewed here

Missed Drug Delivery Failure

• Pressure alarms, both low and high, may alert us to failures in drug delivery. Most pumps operate around 150-250 mmHg and alarm at 500 mmHg except when a bolus is given
• Disconnection
  • In the case of disconnection there will be a sudden drop in driving pressure triggering a low-pressure alarm
  • The infusion set through should have a Luer-lock connector at each end to minimise the chance of disconnection
• Failure to deliver the desired dose
  • Anti-syphon valves are recommended on the drug delivery line
  • Anti-reflux valves are recommended on any fluid administration line
  • Retrograde flow will trigger a high-pressure alarm
    • Accidentally closed 3-way tap
    • Kinked infusion line

Frequent checks of the line especially in the setting of change in clinical signs may alert the anaesthetist to early detection of failed drug delivery. We recommend the TIVA line is visible during the surgical procedures if feasible. We recommend not to set the high-pressure alarm to its maximum limit usually (1110mmHg) as this may delay recognition of failed drug delivery. All machines have a visual indicator of infusion and it is important to check this after any alterations are made such as dose adjustment, syringe change and infusion line repositioning.

AAGBI Monitoring Guidelines 2021

• State that processed electroencephalogram (pEEG) monitoring should be used when total intravenous anaesthesia (TIVA) is administered together with a neuromuscular blocking drug.
• It should start before induction and continue at least until full recovery from the effects of the neuromuscular blockade has been confirmed
• This new guidance may alter even the experienced TIVA users approach
• Further details can be viewed here

Expense

• TIVA use was initially restricted to proprietary drug preparations and pumps
• Historically, this significantly increased the cost and prevented widespread use
• Fortunately, the markets opened for competition and overall costs associated with modern-day use have decreased significantly
• Cost should not remain a barrier but 28% of infrequent users cite this as a reason not to use TIVA
• Ng and Lam in Melbourne Australia carried out a A cost comparison between total intravenous and volatile-based anaesthesia
  • Consumables and excess wasted drugs for TIVA were included in their calculations
  • TIVA was significantly less costly than a comparable sevoflurane anaesthetic at FGF1-2L/minute
  • TIVA was 5-10 times less costly than a desflurane anaesthetic at FGF 0.5-1 L/minute
  • However, the lower costs of intravenous anaesthetics compared to the higher costs of the newer inhalational agents such as desflurane mean that TIVA should no longer be seen as an additional expense compared with inhalational anaesthesia

For those of you who are interested please follow the link to the article for further detail.

Training

• Promotion of the safe use of TIVA is paramount
• Guidelines, articles, our recommended book and courses like this play an important role in the distribution of knowledge

Limitations

• TIVA is by no means perfect and we are the first to acknowledge its limitations.
• No widespread technology is available to alert anaesthetists to disconnection
  • Research and development in this area are quickly advancing
• Non-delivery of drug
  • No reliable real-time monitor of propofol concentration are widely available currently
  • New technology shows agreement between plasma and exhaled propofol concentrations suggests that proton transfer mass spectrometry can be used for real-time propofol monitoring
  • Real-time measurement of end-tidal volatile agent concentration is cited as a major advantage.
• Some of the medications we use as adjuncts to TIVA can make the processed electroencephalogram unreliable.
• In some scenarios, there may be a benefit to volatiles
  • Cytoprotective properties with ischemic preconditioning
  • Cardioprotective properties of volatile anaesthetics have been demonstrated experimentally and in haemodynamically stable patients undergoing coronary artery bypass grafting
    • This advantage may be overstated, The influence of propofol versus sevoflurane anaesthesia on outcome in 10,535 cardiac surgical procedures concluded
    • Sevoflurane and propofol both possess some, although different, cardioprotective properties.
    • Sevoflurane appears to be superior to propofol in patients with little or no ischemic heart disease
    • Propofol seems superior in patients with severe ischemia, cardiovascular instability, or in acute/urgent surgery
  • No IV access is required for paediatric gas induction
  • Potent bronchodilator
  • Less drug interaction and the majority exhaled unmetabolized

All anaesthetists are likely to need to use TIVA at some point. We may be required to provide general anaesthesia in circumstances or locations where a volatile cannot be administered. Therefore, all anaesthetists should be skilled and confident in delivering TIVA. The results suggest that is not currently the case.