How to adapt TIVA for emergency surgery

TIVA for Emergency Surgery

• Relatively few studies have looked at TIVA use in the emergency setting
  • TIVA can be adapted to provide anaesthesia in emergency settings even for high-risk patients with co-morbidity
• Patients undergoing emergency surgery should also benefit from TIVA
  • In particular, the improved recovery/emergence profile associated with its use
• TIVA is traditionally associated with longer induction times as this is usually carefully titrated
  • This is the main deterrent to its use in emergency surgery
• RSI seldom needs to be very rapid following pre-oxygenation and several techniques can be used
  • Titrate up the effect-site concentration
  • Application of cricoid at the loss of consciousness
  • Bolus of remifentanil a fast acting muscle relaxant
• In hemodynamically stable patients
  • Low dose TCI (1–1.5 μg.ml−1) during pre-oxygenation will allay anxiety and allow faster subsequent induction of anaesthesia
• Various modifications of the TCI technique exist in clinical practice to reduce induction times allowing the airway to be secured swiftly
• pEEG can help with titration to clinical effect
• Below are some of the different approaches used. If you have a favourite way of delivering TIVA that is not covered here please let us know on the discussion board!

Methods that retain the accuracy of plasma concentration predictions

• Manual bolus from the TCI pump
  • Some TCI pumps, such as Fresenius Kabi, will calculate the blood and effect-site concentrations of drugs if you manually push the plunger to deliver a bolus of drug
  • Set up, configure and commence the infusion at mild hypnotic levels
    • Effect-site 0.5 μg.ml−1
  • When preoxygenated and ready, manually depress the plunger to deliver a pre-determined bolus of propofol
  • Select an appropriate TCI concentration to continue the infusion
  • Once the airway is secure, titrate to response or pEEG as usual
• Deliberate overshoot of plasma level effect-site target
  • By targeting the EC to a very high level the induction bolus will be delivered by rapid infusion
    • Modern TCI pumps achieve flow bolus flow rates of 1200 ml.h-1 with a precision of 0.1 ml.h-1
  • Some pumps display the bolus dose to be administered allowing the clinician to modify it as required
    • The time at which the bolus will be administered may, in some pumps, be displayed
  • After the initial bolus is given, reduce the effect-site to an appropriate target for the clinical scenario
    • Titrate to response
• Set the target effect-site to an even higher number, e.g. 10 μg.ml−1
• Predetermine how many ml of propofol you would like to administer
• Carefully watch the plunger depress until the desired bolus dose has been delivered
• Stop the infusion and administer the muscle relaxant
• Restart the infusion at an appropriate effect-site target
• Caution is required to ensure timely stopping of the infusion so that excessive doses are not delivered to the patient

It is necessary to ensure that the configured maximal flow rate of the TCI pump during bolus delivery is adequate to allow the relatively large hypnotic bolus for RSI to be delivered in a short time

• Use of three-way tap and empty ‘reservoir syringe to syphon bolus dose from the TCI pump before delivery to the patient
• A ‘reservoir’ syringe is attached to the distal end of the infusion set
• At induction, close the tap to the patient and leave open to the reservoir syringe
• Allow the reservoir syringe to fill passively until you have your required bolus dose in the syringe
• Pause the TCI pump
• Rotate the three-way tap through 180 degrees and inject the induction dose of propofol and muscle relaxant
• Rotate the three-way tap promptly through 90 degrees to open the infusion line to the patient and restart the pump
• This can hasten onset and will be faster than the pumps

The introduction of a three-way tap requiring multiple rotations is a source of error and careful attention must be paid at all times whilst using this technique

Accuracy of plasma concentration predictions not maintained

• For those who prefer the traditional RSI the benefits of TIVA can still be brought to the patient
• TCI infusion can be started after manual bolus and titrated to BIS
• Lower doses should be used initially to counteract the additional propofol bolus
• One can consider using a plasma target site infusion to lessen the pharmacodynamic side effects

Specific advantages of TIVA in trauma patients

• Retrieval medicine and transfer of patients to ICU
  • Propofol infusion is easier to use in the field, especially along with ketamine. It also provides a seamless transition into the OT and from there to the ICU without accidental, emergence or awareness
• Closed head injury
  • Propofol is used widely for anaesthesia during neurosurgery as it preserves cerebral autoregulation
  • Maintains coupling of cerebral blood flow to cerebral metabolism
  • Favourable effect on intracranial pressure
  • Neuroprotective effects

This has not translated to improved outcomes following TBI

• Pulmonary injuries: Propofol
  • Hypoxic pulmonary vasoconstriction preserved
  • Reduces ventilation-perfusion mismatch in pulmonary contusions
  • Depth of anaesthesia is independent of ventilation
• Trauma surgery
  • Surgical stimulation and haemodynamic status can change rapidly and TIVA allows anaesthesia and analgesia to be altered individually as required
  • Remifentanil allows the level of analgesia to be titrated without changing the level of consciousness or ventilation

Specific advantages of TIVA in trauma patients

• Blood loss
  • Propofol has a large volume of distribution (Vd). Consequently, blood loss during surgery doesn’t significantly affect the propofol blood concentrations
  • Hypovolaemia, however, will reduce propofol clearance from the blood and increase pharmacodynamic sensitivity
  • Overall, blood loss does not require propofol “replacement”. Correction of hypovolaemia and blood transfusion takes priority