About the practice of TIVA and TCI in Neuroanaesthesia

1. .
.
TIVA IN NEUROANESTHESIA:
TCI VS MANUAL TECHNIQUES
DR UNNIKRISHNAN P
MD DA PDCC (NEUROANESTHESIA) MBA
SCTIMST, TRIVANDRUM

2. .
TWO METHODS: MCI & TCI
MCI
TCI

3. TARGET CONTROLLED
INFUSION (TCI)

4. .
TCI CARES...A LOT; YOU CAN’T COUNT
IT IN ML/MIN !
.
..but can count in ug/mL !!!

5. .
A BETTER AWARENESS OF THE WHOLE
SITUATION….
V2 V1 V3
Effect site
Elimination

6. .
WHEN YOU ARE USING TCI
➤ Faster achievement of a therapeutic concentration and a
reliable maintenance
➤ Optimum doses of the drug
➤ Reduces work
➤ Lesser chance for errors
➤ You can use the pump for induction too
➤ TIVA using Propofol TCI + Remifentanil TCI will provide a near
perfect choice for neuroanesthesia: easily titratable hypnosis &
analgesia, fast recovery

7. .
MANUALLY CONTROLLED INFUSION
(MCI)
➤ Without an appropriate bolus, a constant propofol infusion at
10 mg/kg/h requires 40–90 min to achieve a clinically useful
plasma concentration of 4 μg/ml in an 85 kg adult male
Bolus

8. .
TCI INDUCTION & MAINTENANCE
➤ Propofol: start with a target concentration 3-4 ug/ml; titrate up
by 0.5–1 μg/ml to reach LOC; note the concentration at which
there is no response to a noxious stimulus
➤ Target concentration (5-8 ng/ml) of remifentanil; adjust during
placement of the Mayfield head holder [manual 0.08–0.25
ug/kg/min]
➤ Remifentanil has little hypnotic action

9. .
FRESH PAIR
➤ Good synergism
➤ Maintenance: Propofol target concentrations of 3.0–6.0
ug/ml(without opioids) or 2.5–4.0 ug/ml (with opioids)
➤ Target remifentanil concentrations up to 10–15 ng/ml may
be required during procedures involving cranial nerve
stimulation or extensive craniotomies,
➤ May be associated with acute tolerance or hyperalgesia.
➤ The remifentanil infusion can be continued at a target of
1–2 ng ml−1 to smooth extubation if desired. Better cough
suppression

10. .
TCI EFFECT SITE CONCENTRATIONS
➤ Ferreira et al predicted the Propofol Ce at various stages of
neurosurgical anesthesia.
➤ Prop Ce at intubation: 5 ±1 , incision: 2.6 ± 0.9 , and
extubation: 1 ± 0.3 μg/mL.
➤ Remifentanil Ce at intubation: 2.2 ± 0.3 , incision: 6 ± 2.6, and
extubation: 2.2 ± 0.9 μg/mL.

11. .
SOMETIMES COMPOSURE IS BETTER
THAN AGGRESSION
➤ During induction --> TCI uses smaller doses, and slower
infusion rates, --> attenuate the reduction of MAP --> impaired
cerebral autoregulation --> safer way of induction in aneurysm
surgeries and TBI

12. .
IONM
➤ Anesthesia influences IONM and provision of a comparable
anesthesia throughout the surgery increases the reliability of
the signals and reduces confounding in interpreting the cause
of a derangement (pharmacological vs neurosurgical)
➤ Avoids a disastrous light plane of anesthesia or a too deep
plane causing hypotension which can affect the monitoring

13. .
WHILE EEG IS BEING MONITORED
➤ TCI allows a constant level of anesthetic effect --> avoid
misinterpretation of EEG depression caused by boluses or
rapid changes in anesthetic level from true insults

14. .
TCI FOR AWAKE CRANIOTOMY
➤ TCI Propofol + TCI Remifentanil moderate sedation
➤ TCI Propofol + TCI Remifentanil Asleep-Awake-Asleep (GA)
➤ Optimal use of the short acting agents using TCI…an excellent
choice
➤ Remifentanil: spontaneous ventilation is uncommon with
concentrations > 1.5 ng/ml

15. .
DON’T OVER ESTIMATE!
➤ Propofol: Schneider superior to Marsh. For intraoperative
neurological testing -->propofol concentrations as low as 0.8
ug/mL.
➤ Marsh (Cplasma=1.3 ± 0.5 ug/mL)
➤ Schnider model (Cplasma=1.0 ± 0.4 ug/mL).

16. .
TIME CHANGES EVERYONE; SPEND MORE
TIME WITH THEM!
➤ The Schnider TCI Vs Manual Propofol
➤ A slower induction of anaesthesia may be achieved by setting
a lower initial target propofol (e.g. 1 ug/ml) and making
repeated 0.5–1 ug/ml incremental increases in the target
concentration.

17. .
LOTS OF MODELS
Lots of…..
..but only for a few drugs

18. .
VERY LIMITED OPTIONS
➤ Marsh, Schnider : Propofol
➤ Minto: Remifentanil*
➤ The Kataria model
➤ The Paedfusor model

19. .
TCI ALSO FINDS IT DIFFICULT TO
TACKLE OBESITY
➤ Current TCI models are not formally validated for use in such
patients
➤ Marsh : upto 150 kg
➤ Schnider model : BMI < 35 kg.m-2 for women or < 42 kg.m-2 for
men.
➤ pEEG monitoring
➤ Minto: above the critical value, inadequate bolus dose and
infusion rate

20. .
ACCURATE DOSING
➤ The ‘correct’ body mass to use with TIVA has been investigated and
currently Servin's formula for calculating an input mass for TCI
infusions seems most useful:
➤ where ideal body weight= ideal BMI (male 22, female 26) × height2(m)
Input mass =(ideal body weight)+ 0.4×(actual−ideal)

21. .
PEDIATRIC POPULATION
➤ The Kataria model : patients aged 3–16 yr with weight of 15-61
kg.
➤ The Paedfusor model : for patients 1–16 yr of age and
weighing 5–61 kg
➤ Remifentanil adult TCI targets using the Minto model for
patients aged ≥ 12 years and weighing ≥ 30 kg.
➤ MRI sedation: you cant use DOA monitoring
Haven’t
heard
about
these!?

22. .
PEDIATRIC POPULATION
➤ When switching to TIVA following a gaseous induction:
➤ Set an initial propofol target of 4 ug/ml and decreasing the
target after the pump indicates that a 2–3 mg/kg bolus has
been delivered
➤ With remifentanil, propofol target can be reduced by up to 50%
(2.5– 4 ug/ml) in children aged < 12 years; else propofol will
accumulate.

23. .
OTHER PROBLEMS
➤ Renal dysfunction, CCF, liver dysfunction
➤ Neurosurgical patients taking AEDs and other enzyme
inducers: Actual concentration difficult to predict
➤ Synergism: Well known between Propofol and Remifentanil
when used in the TCI-TIVA mode. Both drugs reaching target
plasma/effect site concentration at the same time is important
➤ Unknown interaction between all other agents without a PK
model for TCI
➤ Ignorance about the models: e.g. Schneider in plasma
targeting may underdose…may reflect during pinning
➤ In Marsh model age is an input only to ensure that the patient
is ≥16 yr. It should better be used in plasma targeting mode
only.

24. MANUALLY CONTROLLED
INFUSION (MCI)

25. .
IF USING MCI, AND IF YOU BELIEVE IN
PHARMACOKINETICS
MCI propofol infusion regimen, designed to give a plasma concentration of 3 μg/ml: 1
mg/kg bolus f/b 10mg/kg/h, reduced to 8mg/kg/h at 10min, reduced to 6mg/kg/h at 20
min
Tea
time

26. .
MCI LAGS…..
➤ A fixed infusion rate --> rising, declining or stable concentrations
-->under or overdosage.
➤ For increasing the depth --> a bolus f/b a higher infusion rate
and for reducing the depth, a pause f/b a lower infusion rate -->
still the plasma conc lags--> more lag for Ce --> more lag for
clinical effect

27. .
BUT, YOU CANT LIVE WITHOUT MCI!
➤ Popular TCI models only for propofol and opioids
➤ In India, along with the propofol TCI, fentanyl has to be
administered as manual infusion
➤ Ketamine is a reemerging drug in neuroanesthesia
➤ Remifentanil: For children <12y : use a manual infusion, 0.2–0.5
ug/kg/min

28. .
YES WE NEED MCI!
➤ In diseases with end organ dysfunction
➤ Also in neurosurgical patients on AEDs
➤ propofol+fentanyl+dexmedetomidine with IONM?
➤ Single syringe TIVA?

29. DEXMEDETOMIDINE: IS IT THE MOST
SUITABLE DRUG (MSD) IN
AWAKE CRANIOTOMIES ??!!
➤ Calm, cool patient!
➤ Anxiolysis-Analgesic-Opioid sparing*
➤ No effect on ICP
➤ Less respiratory depression less hypercapnia
➤ Easily arousable despite sedation ; less PONV

30. .
TIVA WITH MANUALLY CONTROLLED
INFUSIONS: PLEASE NOTE
• The anesthesiologist has to spend time for dose calculation and its
titration throughout the procedure
• Importance of depth of anesthesia monitoring increases
• May affect the predictability of the recovery
• Over or under consumption of the drug/s
IF TCI NEEDS THIS
VIGILANCE
MCI NEEDS, THIS
VIGILANCE

31. “TEACHING TIVA MEANS TEACHING
A LOT OF ANESTHESIOLOGY
IT’S A GREAT
TRAINING TOOL
……………………………………………………………..

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