Intravenous Anesthetics Flashcards
Intravenous anesthetic are defined as….
Agents that induce loss of consciousness in a one arm-brain circulation time.
Uses:
Induction - rapid
Maintenance
Sedation during ICU and regional anesthesia
Treatment of epilepsy
Gaba receptor structure
Pentamer
2 alpha
2 beta1 gamma
Gaba funtion
Amnesia
Depress spinal reflexes
Hypnosis
Thiopental is…
Sulfur analogue of oxybarbiturate pentobarbital
Pale yellow powder
Vial contains sodium carbonate 6% by weight
2.5% solution stable for many days and needs to be bacteriostatic due to alkaline pH
Thiopental inductions dose
3 to 7 mg.kg-1
Thiopental duration
5 to 10 minutes
Thiopental most important effect?
Acute porphyria crisis
Does thiopental affect metabolism and elimination of other drugs?
Yes it increases it
Intra-arterial injection of TP is a serious condition why?
It is meant to be IV
It causes endothelial damage
Pain
Delayed or absent sleep
Blanching or cyanosis
Loss of peripheral pulse
Arterial thrombosis with gangrene
Treatment for intraarterial injection of TP
Stop injection and leave needle in
Dilute with saline
Give local anesthetics &/or vasodilator (papaverine)
Start IV heparin
Intraarterial injection of hydrocortisone
Postpone surgery
Propofol
Describe
Phenol derivative
Highly lipid soluble
1% or 2% lipid-water soluble
Weak organic acid
Liver metabolism and extrahepatic metabolism
pKa 11
Almost entirely unionized at pH 7.4
Propofol dose
1-2mg.kg-1
Propofol effects
Bradycardia
Decreases BP and myocardial contractility
Fat overload syndrome (Hyperlipidemia, fatty infiltration)
Green urine and hair
Antiemetic
Hpypotension
Respiratory depression Leading to apnoea
Excitatory effects in 10%
Injection into small veins is painful - reduce using lidocaine
Propofol infusion syndrome clinical features
Metabolic acidosis
Rhabdomyolysis
Renal failure
Cardiac failure
Advantage of propofol
Optimal sedation level
Antiemetic
Propofol metabolism
Liver metabolism- eliminated as sulfur &/or glucuronide conjugates in urine
Extrahepatic metabolism
Elderly- lower Vd and lower clearance, lower doses needed
Adverse effects of propofol
Iv injection site pain
Hypotension
Hypoxia
Lipidemia
Green discoloration of urine (& hair)
Ketamine general description
A phencyclidine derivative
Racemic mixture- S+ (more potent)
R- enantiomer
Water soluble, forms acidic solution (pH 3.5-5.5)
Dose: 1-2 mg/kg IV
Systemic effects of ketamine
Normotension/hypertension
Tachycardia
Airway reflexes & tone maintained
Bronchodilation
Emetogenic
Dissociative anesthesia, analgesia, hallucinations
Ketamime maim effect
Produces sympathetic nervous system stimulation- increase adrenaline and noradrenline
Ketamine effect on ICP
INCREASE!!!!
Etomidate dose
And formulation
0.3mg/kg
Prepared as 0.2% solution
Contains 35% propylene glycol for stability and reduction of irritant properties
Etomidate effects
Least cardiovascular effects
Suppress adrenocortical function
Increase in mortality when used as an infusion to sedate septic patients in ICU
Etomidate side effects
Pain on injection
Excitatory movements
Nausea
Vomiting
Porphyric crisis
Benzos characteristics
Enhance gaba transmission in CNS
Lipid soluble (except midazolam)
Anterograde amnesia
Anticonvulsant activity
Diazepam 5-20 mg
Midazolam 1-5 mg
Sodium thiopental:
Pale yellow powder
3-7mg/kg
30-40s
5-10m
Enhances GABA-A
Decreases CO, BP w/ reflex tachycardia
Resp. depression
Laryngospasm, bronchospasm
Decreases cerebral O2 consumption, cerebral blood flow, cerebral metabolic rate
Can exacerbate porphyria
Effects of sodium thiopental:
Decrease CO, BP w/ reflex tachycardia
Dose-dependent respiratory depression
May cause laryngospasm and bronchospasm
Decrease Cerebral O consumption, decrease cerebral blood flow, decrease cerebral metabolic rate
Favorable aspects of IV anesthetics:
Fast onset
Avoids the excitatory phase
4 IV anesthetics:
Propofol, etomidate, ketamine, thiopental,
5 Inhalational anesthetics:
Nitrous oxide, isoflurane, sevoflurane, desflurane, xenon
Propofol is presented as a _____ due tompoor water solubility
1% or 25% aqueous emulsion
TIVA indications:
- Risk of MH
- Long QT syndrome
- History of severe PONV
- Thoracic surgery
- Patients w/ anticipated difficult intubation/extubation
- Neurosurgery
- Myasthenia gravis/ neuromuscular disorders
- Non-theatre disorders
- Day-case surgery
- Patient choice
Propofol only TIVA dose:
Mixture dose:
2-2.5 mg/kg
1 mg/kg
Dexmedatomidine:
alpha-2 agonist
anxiolytic, sedative, analgesic, sympatholytic (respiratory depression)
