TIVA IN 21ST CENTURY Dr. Mrs. Minnu M. Panditrao Consultant Dept. Anesthesiology & ICU Rand memeorial Hospital Freeport, Bahamas
DEFINITION:It is a form of balanced anaesthesia where theanaesthetic state is achieved with the help ofintravenous administration of a combination ofhypnotic & analgesic drugs without the use ofinhalational anaesthetic agents including N2O
HISTORY: Christopher Wren 1657 Alexander Wood 1853 Pierre Cyprien Ore 1874 (Chloral Hydrate) Drs. Waters & Lundy 1934 (Thiopentane) Dr. Stoelting 1957 (Methiohexital)
INTRODUCTION:Volatile Inhalational Agents & N2O avoidedPROBLEMS: IN THE PAST - Unavailability of satisfactory drugs - Inadequate methods of administrationNowadays these problems have been solved.
BENEFITS OF TIVA:1. Rapid & Smooth Induction2. Better Control of Depth3. Decreased Awareness4. Fast Recovery5. Reduced Nausea Vomiting6. Reduced Stress Response7. No Organ Toxicity8. N2O Side Effects Avoided
BENEFITS (contd.):9. Better for Neurosurgery10. Higher conc. of O2 possible11. Better for Airway Endoscopies12. For Transits of Remote Locations Better13. During CPB (Cardiac Surgery)14. No atmospheric pollution, No environmental damage15. For prevention of MH in susceptible cases
DISADVANTAGES OF TIVA1. Once IV drug given, can’t be retrieved2. Phlebitis, Venous Irritation3. High Cost4. Infection in Propofol5. Special Equipment is required
Can Be Administered By: 1. Intermittent Boluses 2. Continuous Infusion
Advantages of Infusion1. Oscillations in Drug conc. Avoided2. Overdosing & Underdosing Avoided3. Provides stable depth of anaesthesia4. Side Effects reduced5. Recovery time reduced6. Total Drug requirements decreased (by 25-30%)
Disadvantages: 1. More Expensive & Complicated Equipment 2. Difficult to Use
RECENT ADVANCES:TCIS (Target Controlled Infusion Systems) - DiprifusorTIVA with Closed Loop Control of Anaesthesia with - AEPI - BISCLAN (Closed Loop Anaesthesia)
INDUCTION OF TIVA:Factors Influencing the Dose:KeO--Rate constant, is proportional to onset of actionConcentration Gradient between the blood & the effect site, is inversely proportional to onset of action
CLINICAL SIGNIFICANCEPropofol & Thiopentone because of their large KeO are better for inductionInduction doses vary depending upon pharmacokinetic & pharmacodynamic factorsAddition of 2 inhalational agents is simply additive but of IV agents is synergisticSynergism helps it providing adequate depth for stronger stimuli
CLINICAL SIGNIFICANCE (contd.)Decreased dose requirement provides more haemodynamic stabilityHowever synergism for side-effects (respiratory depression) should be kept in mind
INDUCTION WITHINDIVIDUAL/COMBINATION OF DRUGS1. Propofol: Induction dose is 1-2.5 mg/kg. Blood conc. reqd. is 2.5-5.5 μg/ml Onset of action is <60 sec. Time to peak effect is 90 sec. Duration of hypnosis is 5-10 min. Premedication with Opioids reduces the Induction Dose
2. Propofol with Opioids: Effect is Synergistic Reduced dosage required3. Ketamine: As a supplement to Propofol– Effect is additive Ketamine+Benzodiazepines+Opioids have also been used
MAINTENANCE WITH TIVAFactors controlling the dosage:Intensity of Surgical stimulationClinical signs of depth of anaesthesia
CLINICAL SIGNIFICANCEAdjust the dose depending upon the response to Surgical stimulusHigher dose required during Laryngoscopy & IntubationLower dose requirement during scrubbing, prep & drapingRequirement of max. conc.(2xCP50) at the time of skin incision
CLINICAL SIGNIFICANCE (contd.)Patients movement, haemodynamics &/or autonomic responses indicate inadequate anaesthesiaOther indicators like BIS, AEPI, Train of 4 have been tried with variable successIf no response for 10-15 min., decrease infusion rate by 20%Once patient starts responding, administer a bolus & set the new infusion rate midway between previous & present new rate
CLINICAL SIGNIFICANCE (contd.)Potent Opioid should be given for adequate analgesiaContinuous titration of hypnotic must be done & concept of CSHT kept in mindNet requirement of dose depends not only upon pharmacokinetics but also on pharmacodynamic variables
MAINTENANCE WITHINDIVIDUAL/COMBINATION OF DRUGS1. Propofol: Should be used along with an analgesic A manual infusion scheme is Loading dose 1-2mg/kg, followed by 10 mg/kg-hr for 10 min., followed by 8 mg/kg-hr for next 10 min. & 6 mg/kg-hr thereafter This provides a blood Propofol conc. of 3.7 μg/ml within 2 min.
PropofolInduction of GA: 1-1.2 mg/kg IV, dosedecreased in patients >50yrsMaintenance of GA: 80-150 Μg/kg-min. IVwith Opioids, dose decreased in patients >50yrsSedation: 10-50 μg/kg-min. IV infusion
Other agents used are Opioids, Benzodiazepines & Ketamine Only Ketamine can be used as a sole agent Its disadvantages being long recovery time & emergence phenomena Recommended Ketamine infusion regimen is:0.5-1 mg/kg IV, as required, with 50% N2O in O210-15 μg/kg-min., with 50% N2O in O230-90 Μg/kg-min., without N2O
Recommended Opioid infusion regimen formaintenance of anaesthesia along with ahypnotic are Drug Target plasma Bolus Infusion Conc. (ng/ml) μg/kg rate μg/kg/min Fentanyl 1 3 0.020 Alfentanil 40 20 0.2 Sufentanil 0.5 0.5 0.01 Remifentanil 3 1 0.1
RECOVERY FROM TIVARecovery is due to redistribution & not due to eliminationDecline in plasma conc. is due to distribution from central to peripheral comp. & eliminationDistribution & elimination depends upon eqbm. between central & peripheral comp.
CONTEXT SENSITIVE HALF TIME (CSHT) It is the time taken for plasma conc. to decline by 50% after infusion of different duration designed to maintain a constant plasma conc. This concept takes into consideration - Elimination & - Distribution CSHT increases with the increase in duration of infusion
CLINICAL SIGNIFICANCEDrugs that are metabolised & eliminated rapidly have short CSHT which is not affected by longer periods of infusionRecovery time for a drug varies depending upon its duration of infusion & desired %age decline required for recoveryTime to recovery depends upon the difference between the maintenance conc. & threshold conc. (%age decline) required for recovery. This %age decline may vary from 20%(with Opioid+Hypnotic) to 80%(when only hypnotic is used
RECOVERY CHARACTERISTICS OF INDIVIDUAL AGENTS1. Propofol: - Avg. Propofol blood conc. for: awakening is 1.6 μg/ml orientation is 1.2 μg/ml - CHST for Propofol after 3 hrs is 25 min. after 8 hrs is 40 min. The required %age decrease in Propofol conc. for awakening is <50% so recovery will remain rapid even after prolonged infusions. When combined with Opioids recovery time is even shorter(9-12 min. with Fentanyl)
2. Opioids: CSHT for Fentanyl, Sufentanil & Alfentanil are: after 1 hr infusion-20% ↓ in 15-20 min. after 4 hr infusion-20% ↓ for Sufent & Alfent takes half as long as for Fentanyl after 10 hrs infusion-20% ↓ for Fentanyl is 45 min & for Sufent & Alfent is ¼ of that With Remifentanil as it has shortest CSHT, most patients recover within 3-5 min. after stopping its infusion
SUMMARYTIVA in 21st Century has come a long wayPropofol (1986)First syringe driver by OhmedaDiprifusor chip softwareTCI & CLAN
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