2008.04.05.karachi.english.fauzia n minal

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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



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



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



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



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.



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



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



Advantages over commonly usedinhalational agents

Easy titratability of drugs

Quick induction and reversal

Superior recovery profile

Portable delivery system

Less operating room pollution



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



Contd……

No single intravenous anaesthetic agent

provides all components of anaesthesia in its

therapeutic dose viz:• Amnesia

• Hypnosis

• Analgesia

• +/- muscle relaxation



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



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



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



What is important to know beforegiving TIVA?

As for any anaesthetic

Patient evaluation

Procedure specifications



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



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



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



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



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



Cerebroprotective effects

• Proportional Reduction in CMRO2 and CBF,

decrease in ICP

• Free radical scavenging-prevention of free radical

induced lipid peroxidation

• Membrane stabilisation

• Anticonvulsant



Disadvantages

• Paediatric infusion syndrome

• Myoclonic phenomenon-imbalance between excitatory

and inhibtory phenomena

• Pain on injection

• Allergic reactions

• Bacterial growth



How is TIVA delivered?

TIVA can be given by:

Simple intravenous boluses

Variable rate continuous infusion



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



BET infusion scheme

B = Loading dose

E = terminal elimination

T = transfer to peripheral compartment



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



CLOSED LOOP SYSTEM

• Is the future

• Feedback signal of effect site concentration

built into the delivery system

• Prospective utilization of BIS and AER



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



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



Applications of TIVA

• As general anaesthetic-neurosurgery, daycase surgery, bariatric surgery

• Supplement to regional, local anaesthetic

• Sedation analgesia for diagnostic/therapeuticprocedures



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

2008.04.05.karachi.english.fauzia n minal

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