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Barbiturates and Other IV Induction Agents for General Anesthesia

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Division Director, Anesthesia Services. UAB Department of Anesthesiology. Ideal Agent ... Induction of General Anesthesia. One arm-brain circulation time. Max ... – PowerPoint PPT presentation

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Title: Barbiturates and Other IV Induction Agents for General Anesthesia


1
Barbiturates and OtherIV Induction Agentsfor
General Anesthesia
  • James R. Boyce, M.D., FRCP(C)
  • Division Director, Anesthesia Services
  • UAB Department of Anesthesiology

2
Ideal Agent
  • Rapid Offset
  • Propofol
  • Etomidate
  • Methohexitone
  • Lack of accumulation
  • Propofol

3
Ideal Agent
  • No allergies
  • No histamine release
  • No CVS, respiratory system disturbance

4
CVS Disturbance
  • Inotropic
  • Chronotropic Heart
  • Dromotropic
  • Systemic vascular resistance

5
Respiratory Disturbance
  • Depression
  • Ketamine is best

V
CO2
6
Ideal Agent
  • Analgesia properties
  • Ketamine
  • Compatibility
  • Pentothal and succinylcholine
  • Low postop nausea
  • Suitable in porphyria
  • Aminolevolinic synthetase

7
Pharmacokinetics
  • VDss That volume that would be required if the
    concentration of drug in all body tissues were
    the same as in the blood.

Blood
Fat
Muscle
Other
8
Concentration
  • weight ? volume weight
  • volume concentration

Concentration
9
First Order Kinetics
  • First Order Kinetics Fractional Change per
    Unit Time

10
Elimination Constant
  • Elimination Constant (Ke) The Fraction

11
Clearance
  • Clearance (Cl) The fraction (Ke) of the apparent
    volume of distribution that is cleared of a drug
    per unit time
  • Cl Ke X VDss
  • Units Volume
  • Time

12
Half Life
  • Half Life (T½B) Time required for the
    concentration to be reduced by half

Log x x/2
Time T ½ B
13
Loading Dose
  • Loading Dose The weight of drug required to
    produce a therapeutic concentration when injected
    into the apparent volume of distribution ( Wt
    VDss)

14
Infusion Rate
  • Infusion Rate (units wt/time) IR Cl x

15
Factors Affecting Induction Dose
  • Weight
  • Lean body mass
  • Age
  • VDss
  • Hemodynamic status
  • Ejection fraction
  • Volume status of patient
  • Pentothal and Pearl Harbor

16
Factors Affecting Induction Dose
  • Premedication
  • Rate of injection
  • Drug binding
  • (Less STP in renal patients because of decreased
    albumin)

17
Mechanism of Hypnosis
A complex compound made up of two or more similar
units
  • Works at GABA receptor
  • GABA oligomeric complex
  • Benzodiazepine receptor
  • GABA receptor
  • Barbiturate receptor
  • Chloride channel with picroroxin receptor

18
Mechanisms of Hypnosis
19
(No Transcript)
20
Thiopentone
21
Thiopentone
  • Soluble in H2O pH 10-11
  • 2.5 or less
  • T ½ ? 3-8 minutes
  • T ½ ? 5-12 hours
  • VDss 170 L / 70 kgm
  • 80 bound to albumin
  • Metabolism oxidation
  • CRMO2 by 50 CBF ? 50

22
Blood Thiopentone
23
Induction of General Anesthesia
  • One arm-brain circulation time
  • Max effect one minute
  • Duration 5-8 minutes
  • Dose 3-5 mg/kgm
  • Reduce in
  • Aged Hypovolemia Inebriated
  • Anemia Hypothermia
  • Organ failure CHF

24
Specific Organ Function Effects
  • Cardiovascular
  • Venodilatation ? decreased preload
  • Slight depression of myocardial
    contractility?decrease cardiac output
  • SVR unchanged
  • Heart rate increased

25
Specific Organ Function Effects
  • Cardiovascular continued
  • Decrease sympathetic output
  • Thiopental not a good choice in
  • Pericardial tamponade
  • Hypovolemia
  • Congestive heart failure
  • Ischemic heart disease

26
Specific Organ Function Effects
  • Respiratory
  • Central respiratory depression
  • Decrease rate and depth
  • Decreased response to hypoxia
  • Laryngospasm
  • Bronchospasm
  • Depressed mucociliary clearance

27
Nighttime Sedation
  • Benzodiazepines better
  • Barbiturates have
  • Small therapeutic index
  • More respiratory depression
  • More CVS depression

28
Contraindications
  • Acute intermittant porphyria
  • Variegate porphyria
  • ?-Aminolevulinic synthetase
  • Allergies
  • Upper airway obstruction

29
Recovery
  • Impaired ability to drive a vehicle - 8 hours
  • Abnormal sleep patterns 12 hours
  • ? Dont drive for 24 hours
  • No antagonists
  • Venous thrombosis 4

30
Etomidate
31
Etomidate
  • Solubilized in 35 propylene
  • Glycol Pain
  • T ½ ? 1-4 hours
  • 90 excreted unchanged (kidneys)
  • Anticonvulsant
  • Myoclonus, epileptiform EEG
  • Decrease CMRO2 (40) CBF (30) ICP
  • Least hemodynamic changes

32
Etomidate
  • Stability in patients with CV disease
  • Slight respiratory depression
  • Inhibits mitochondrial
  • 11 ? and 17 ? hydroxylase
  • Bolus Delays cortisol increase
  • Infusion Prolonged suppression
  • Postop N/V higher

33
Propofol
34
Propofol
  • Alkylphenol or hindered phenol
  • Isotonic 1 in H2O, Soya bean oil
  • Glycerol, EGG phosphatide
  • VDss 70 L/kgm
  • 60 metabolized

35
Preemptive Ketamine Decreases Postoperative
Narcotic Requirements in Patients Undergoing
Abdominal Surgery
  • Eugene S Fu, M.D., Rafael Miguel, M.D., and John
    E Scharf, M.D.
  • Department of Anesthesiology, University of South
    Florida College of Medicine, Tampa, Florida
  • (Anesth Analg 1997, 841086-90)
  • Arylcycloalkylamine
  • Dissociative anesthesia
  • Hallucinations
  • Analgesia
  • Amnesia
  • CVS stability
  • Minimal respiratory depression
  • No bronchoconstriction with ? blockers VE
    inotrope
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