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GENERAL
ANAESTHESIA
Jozef Firment, MD PhD Department of
Anaesthesiology & Intensive Care Medicine
Šafárik University Faculty of Medicine, Košice
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DEFINITION
• (an) aisthetos = (un) perception
• general anaesthesia = „narcose“
• regional anaesthesia = local
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Str
es
s R
es
po
ns
e o
r
Pla
sm
a c
on
ce
ntr
ati
on
Anxiety
Mound
Sleep River
Lake
Prep.
Peritoneal
Traction
Bowel/
Vascular
Clamping ICU
Highlands
Recovery
Plains
Intubation
Incision
Mount
Surgery
Theoretical Plasma Drug
Concentration for Adequate
Anaesthesia
SURGICAL STRESS MAP
Barash, 1997
Duration of Surgery
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PHARMACO-ANAESTHESIA
METHODS
• Inhalational anaesthesia ... VIMA
• Intravenous anaesthesia... TIVA
• Intramuscular
• Rectal
• Combined anaesthesia
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Balanced
Anaesthesia
Analgesia Muscle
relaxation/
Areflexia
Consciousness/Hypnosis
BIS Monitoring
Hemodynamic
Monitoring
Peripheral
Nerve Stimulator
Monitoring Monitoring Anaesthetic Endpoints
BASAL PARTS OF GA
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CIRCULATORY EFFECTS
INHAL. ANAESTHETICS (Barash, 1997)
• BP according to dose (vasodiltion, C.O., cardiodepresion, sympat. activity)
• consumption O2 about 10-15%
• blood flow in liver, kidneys and gut, in brain, muscles & skin
• N2O SVR, PVR and BP, C.O.
• Sensibilisation myokardium to catecholamins: in children, HAL > ENF > ISO > DES > SEV (more in CO2, more with thiopental)
• No influence to pacemaker functions
• No coronary steal efect in man
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RESPIRATORY EFFECTS
INHAL. ANAESTHETICS (Barash, 1997)
• All VT and bronchodilational effect
• Bloc histamin effects on bronchi – bronch.
asthma treatment: HAL, SEV
• Respiratory depresion : N2O>HAL>ISO>DES
• No influence to hypoxic pulmonary
hypertension
• Up to 3x increase effects of musclerelaxants
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CNS EFFECTS OF
INHAL. ANAESTHETICS (Barash, 1997)
• intelectual functions, HAL for 2-8 days (B?)
• intensity of cerebral metabolism (CMRO2):
ISO > EFL>HAL.
• Vasodilat. cerebr. a. & pressure CSF:
HAL>ISO=DES=SEV,
• HAL > ISO influence production & absorbtion CSF
• Light hypocapnia - lower ICP in ISO than HAL
• Autoregulation to CO2 is more blocked by HAL than
ISO
• Epi EFL
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TOXICITY
• HAL = hepatotoxicity (imuno, repeated expositions)
• N2O = hematotoxicity „perniciose“ anaemia
• In septic pat. weakening Ne and Le functions
• Change platelets functions
• Myometrium relaxation – bleeding during C.s. (HAL > 0,5, ISO > 1,0)
Barash, 1997
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DISTRIBUTION COEFF.
ANAESTHETICS (BLOOD / GAS)
Miller. Anesthesia. 4th ed. Churchill Livingston, 1994; Data on file, Abbott Laboratories Inc.
Desflurane Nitrous
Oxide
Sevoflurane Isoflurane Enflurane Halothane
0.45 0.47 0.65
1.43
1.8
2.5
1
2
3
Dis
trib
uti
on
co
eff
icie
nt
(blo
od
: g
as)
Less solubility = faster onset
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GAS CONSUMPTION
DURING ANAESTHESIA
Low flow...
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ADVANTAGES OF
INHAL. ANAESTHESIA
• Easy regulation (deep of anaesthesia)
• Elimination by expiration
• Easier monitoring of anaesthesia deep
• Less risk of postanaesthetical respiratory depresion
• Potentiation of muscle relaxation effect
• Ambulatory anaesthesia
• Price
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ANAESTHETIC MACHINE
LAYOUT
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VAPORISER
VOLATILE ANAESTHETICS ROTAMETER
Cam
pbell
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ANAESTHETIC CIRCUIT
LAYOUT
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UNI-DIRECTIONAL
ANAESTHETIC SYSTEM
LAYOUT
Cam
pbell
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DEFINITIONS
• Intravenous anaesthesia (IVA) =
administartion of intravenous anaesthetics
with addition of N2O in inhalatory mixture
• Total intravenous anaesthesia (TIVA) =
all anaesthetics are administered only by i.v.
route, inspiratory gas contains only oxygen
and air (nitrogen)
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INDICATIONS OF IV
ANAESTHESIA
Support of inhalational anaestesia
Sedation during local anaestesia
Ambulantory anaestesia
Difficult administration of inhal. anaestetics (military or civil injuries, hyperbaric chamber)
Impossible administration of N20 ( FiO2) as bronchoscopy, laryngeal or tracheal surgery
Where is N20 relative CI - one lung anesthesia, vestibule ear surgery, neuroanaesthesia, ileus, air embolia...
• Extracorporeal circuit
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DISADVANTAGES OF TIVA
• Difficulties in an. depth assessment
• Postoperative respiratory depression after
opioids
• Necessity of several IV accesses
• Drug incompatibilities
• More infusion pumps and deliveries
• Air and oxygen source
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INSTRUMENTS FOR TIVA
• Linear pump
• Infusion bottle delivery
• Two IV lines or Y connector
• Oxygen flow-meter
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MEDICAMENTS USED FOR
TIVA
• Anaesthetics: propofol, thiopental,
metohexital, ketamin, midazolam...
• Opioids: morphin, fentanyl,
alfentanil, sufentanil, remifentanil...
• Muscle relaxants: sukcinylcholine,
vecuronium, atracurium, rocuronium,
pipecuronium...
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MUSCLE RELAXATION
• N.-m. junction, mediators
• Depolarising muscle relaxation
• Undepolarising muscle relaxation
• Curarisation
• Decurarisation
• Recurarisation
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POSTOPERATIVE
OBSERVATION
• No difusion hypoxia (N20)
• Absorbtion atelectase (during high FiO2)
• Early administration analgetics in cases
using short-acting opioids
• Possibilities aplication of antidots
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RISK FACTORS FOR PONV