2008.04.05.karachi.english.fauzia n minal
TRANSCRIPT
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Dr Fauzia Minai
Course : 6
Year : 2008
Language : English
Country : PakistanCity : Karachi
Weight : 167 kb
Related text : no
AN OVERVIEW OF TOTAL
INTRAVENOUS ANAESTHESIA(TIVA)
http://www.feea.net
Department of Anaesthesia AKUH
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Objectives of this session
• To facilitate those who wish to practice TIVA
• Review some of the basic principles of
TIVA• Discuss the choice of drugs & technique
• Discuss its feasability of TIVA practice in a
developing country like Pakistan
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Focus of this presentation
Introduction and Definition Rationale for using TIVA
What is important to know before giving
TIVA Drugs used in TIVA
Delivery systems for TIVA
Monitoring in TIVA Application in developing countries
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Introduction
The concept of total intravenous anaesthesia
has evolved from primarily intravenous
induction of anaesthesia to induction as well
as maintenance of anaesthesia with
intravenously administered drugs
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Definition of TIVA
TIVA is defined as a method of inducing and
maintaining general anaesthesia exclusively by
intravenously administered drugs, without
simultaneous administration of any inhalation
agent.
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Why TIVA
Search for suitable drugs and techniques to meet
changing demands of
Advanced diagnostic and therapeutic treatment
modalities requiring alleviation of patientdiscomfort
Need to provide safe anaesthesia with rapid
patient turnover as in ambulatory care setting, tofacilitate maximum no of patients
Anaesthesia in non operative locations where
inhalational anaesthetics are logistically difficult
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Contd…
Availability of• Rapid short acting, easily titratable
intravenous hypnotic, analgesic and muscle
relaxant drugs
• Pharmaco-kinetic and -dynamic based IVdelivery systems which are portable
• Monitors to measure the depth of thehypnotic component of the anaesthetic state
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Advantages over commonly usedinhalational agents
Easy titratability of drugs
Quick induction and reversal
Superior recovery profile
Portable delivery system
Less operating room pollution
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Constraints
Cost
Availability of the most suitable drugs and
delivery systems No reliable technique for monitoring plasma
concentration of drugs equivalent to ET
inhalational agent monitoring Increased risk of awareness specially with
concurrent use of muscle relaxants
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Contd……
No single intravenous anaesthetic agent
provides all components of anaesthesia in its
therapeutic dose viz:• Amnesia
• Hypnosis
• Analgesia
• +/- muscle relaxation
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Hence necessity of
• Suitable drug combinations
• Awareness of drug interactionsfor optimal choice of drugs and dosing strategies
tailored to the patient and procedure requirements
and fast track recovery
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contd……
• Basically most of the analgesic and musclerelaxant components of TIVA are the same asthose which supplement inhalational
anaesthetics in current use
• The difference is mainly in the choice ofdrugs for the hypnotic component
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Drugs for TIVA
Individually or in combination, depending uponthe Patient and Procedure:
Hypnotics
Propofol, Ketamine, Benzodiazepines, Etomidate,
BarbituratesAnalgesics
Fentanyl, Remifentanyl, sufentanil, alfentanil,methadone, morphine
Muscle relaxants
Atracurium, Vecuronium
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What is important to know beforegiving TIVA?
As for any anaesthetic
Patient evaluation
Procedure specifications
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Basic pharmacological actions and interaction
of the drugs used
Effective concentration range of the drugs
used or therapeutic window has to be defined
because of individual pharmacodynamic
variability
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Context sensitive half time
One important drug characteristic for TIVA (since
it is being used for a variable length of time in
infusion form) is the Context sensitive half time
• Context is the duration of drug administrationand this property refers to the time taken for50% decrease of drug concentration at effectorsite after discontinuing the infusion
• This has approximation to awakening time. Is independent of elimination half time
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contd……
Dose titration to desired clinical effect of
sedation and hypnosis is essential to prevent
adverse effects on other organ systems, drug
accumulation and delayed recovery
This is facilitated by routine clinical monitoring
as well as EEG based newer monitors
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Example of a drug regimen
• Midazolam bolus as adjunct to propofol
loading dose followed by continuous infusion
of propofol
Combined with
• Fentanyl boluses or infusion
• Atracurium boluses or infusion
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PROPOFOL
Most commonly used hypnotic for TIVA
• No active metabolites
• Short CSHT
• Rapid onset
• Antiemetic
10-20 mg dose in postoperative period
• Not an MH trigger• CBF: Autoregulation and CO2 responsiveness not
affected
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Cerebroprotective effects
• Proportional Reduction in CMRO2 and CBF,
decrease in ICP
• Free radical scavenging-prevention of free radical
induced lipid peroxidation
• Membrane stabilisation
• Anticonvulsant
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Disadvantages
• Paediatric infusion syndrome
• Myoclonic phenomenon-imbalance between excitatory
and inhibtory phenomena
• Pain on injection
• Allergic reactions
• Bacterial growth
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How is TIVA delivered?
TIVA can be given by:
Simple intravenous boluses
Variable rate continuous infusion
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Continuous infusion devices
Manually controlled infusion through simplesyringe pumps using disposition kinetics suchas the 10-8-6 rule
Microprocessor controlled automated delivery
systems – Target Controlled Infusion Pumps-
Diprafusor
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BET infusion scheme
B = Loading dose
E = terminal elimination
T = transfer to peripheral compartment
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OPEN LOOP SYSTEM
Anaesthetist chooses “target” blood or brain
(effective site) drug concentration
Microprocessor of the pump infuses the drugat the rate needed to rapidly achieve and
maintain the desired concentration based on
population pharmacokinetic- dynamic dataNo feedback signal of output
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CLOSED LOOP SYSTEM
• Is the future
• Feedback signal of effect site concentration
built into the delivery system
• Prospective utilization of BIS and AER
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Advantages of continuous variable rateinfusion
Greater hemodynamic stability
More stable depth of anaesthesia
More predictable and rapid recovery
Potential lower total dose of drug used
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Monitoring in TIVA
• Routine ASA recommended monitoring +/-invasive monitoring as per requirement of
patient and procedure
• EEG based monitoring of hypnosis
(anaesthetic depth)Bispectral Index
Auditory Evoked Response
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Applications of TIVA
• As general anaesthetic-neurosurgery, daycase surgery, bariatric surgery
• Supplement to regional, local anaesthetic
• Sedation analgesia for diagnostic/therapeuticprocedures
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References
Eyres R. Update on TIVA. Pediatric
Anesthesia 2004;14:374-379.
White PF, Romero G. Nonopioid Intravenois
anaesthesia. Clinical Anaethesia 5th Ed
Barash, Cullen & Stoelting