general anesthesia - uniwersytet medyczny w Łodzia.umed.pl/anestezja/dokumenty/anestgeneral.pdf ·...
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Definition of anesthesia
• It is a reversable blocking of pain feeling inwhole body or in a part of it usingpharmacology or other methods
Anesthesia- division
• Local- regional anesthesia, patient isconscious or sedated
• General- anesthesia interact with wholebody, function of central nervous system isdepressed:– Intravenous
– Inhalation (volatile)
– Combined, balanced
Parts of general anesthesia
• Hypnosis- pharmacological sleep,reversable lack of consciousness
• Analgesia-pain management
• Areflexio-lack of reflexes
• Relaxatio musculorum- muscle relaxation,pharmacological reversable neuromuscularblockade
Parts of general anesthesia must bein balance
Hypnosis(anesthesia) Analgesia
Lack of reflexes (muscle relaxation)
• General anesthesia
features
LackLack ofof reflexesreflexes
3
LackLack ofof consciousnessconsciousness
11
PainPain managementmanagement
22NeuromuscularNeuromuscular blockadeblockade
44
Stages of general anesthesia
• Stadium analgesiae (analgesia andsedation stage)
• Stadium excitationis (excitation stage)
• Stadium anaesthesiae chirurgicae(anesthesia for surgery)
• Stadium paralysis respirationis(intoxication, respiratory arrest)
I. Analgesia stage
• Patient consciouss
• Spontaneus respiration
• Reflexes present
• Possible small surgery procedures likedressing change in burns
III. Anesthesia for surgery
• It begins with lack of lid reflex
• 4 substages
• Airway opening necessary
• Possible surgery except for abdominalopening if no relaxants are used
• Possible endotracheal intubation
IV. intoxication, overdosing
• Respiratory arrest
• If anesthesia not discontinued possiblecardiac arrest
EstimationEstimation ofof thethe riskrisk ofof anesthesiaanesthesia ((AmericanAmerican
SocietySociety ofof AnesthesiologistsAnesthesiologists scalescale))
•• ASA 1ASA 1:: healthyhealthy patientpatient..
•• ASA 2ASA 2:: patientpatient withwith stablestable,, treatedtreated illnessillness likelike arterialarterialhypertensionhypertension,, diabetesdiabetes melitusmelitus,, asthmaasthma bronchialebronchiale,,obesityobesity
•• ASA 3ASA 3:: patientpatient withwith systemicsystemic illnessillness decreasingdecreasingsuffitiencysuffitiency likelike heartheart ilnessilness,, latelate infarctinfarct
•• ASA 4ASA 4:: patientpatient withwith seriousserious illnessillness influencinginfluencing hishis statestatelikelike renalrenal insuficiencyinsuficiency,, unstableunstable hypertensionhypertension,,circulatorycirculatory insuficiencyinsuficiency
•• ASA 5ASA 5:: patientpatient inin lifelife treateningtreatening illnessillness
•• ASA 6ASA 6:: brainbrain deathdeath-- potentialpotential organ donororgan donor
PremedicationPremedication
MainMain reasonsreasons forfor premedicationpremedication::
•• AnxiolysisAnxiolysis-- lacklack ofof threatthreat
•• SedationSedation –– calmingcalming downdown
•• AmnesiaAmnesia –– lacklack ofof memoriesmemories ofofperioperativeperioperative periodperiod
• METHODS OF GENERAL ANESTHESIA
OPEN- old
SEMIOPEN – used mostly in pediatric anesthesia
SEMICLOSED- most common
CLOSED- modern anesthesia
• Methods of general anesthesia
CIRCLE SYSTEMCIRCLE SYSTEM
*HIGHHIGH--FLOWFLOW
FRESH GAS FLOW 3 l/min.
*LOWLOW--FLOWFLOW
FGF ok. 1l/min.
*MINIMALMINIMAL--FLOWFLOW
FGF ok. 0,5 l/min.
Stages of general anesthesia
• Introduction to anesthesia (induction)
• Maintaining of anesthesia (conduction)
• Recovery from anesthesia
Anesthesia agents1. Inhalation anesthetics (volatile anesthetics)
- gases : N2O, xenon
- Fluids (vaporisers)
2. Intravenous anesthetics
- Barbiturans : thiopental
- Others : propofol, etomidat
3. Pain killers
- Opioids: fentanyl, sufentanil, alfentanil, remifentanil, morphine
- Non Steroid Anti Inflamatory Drugs: ketonal, paracetamol
4. Relaxants
- Depolarising : succinilcholine
- Non depolarising : atracurium, cisatracurium, vecuronium, rocuronium
5. adiuvants
-benzodiazepins: midasolam, diazepam
Mechanism of action ofinhaled anesthetics
• Reaction depends on concentration. This dependson alveolar (first compartment), blood and brain(central compartment) concentration , (thirdcompartment- other tissue like muscles, fat-accumulation effect):
– Minute ventilation
– Lung blood perfusion
– Solubility in tissues
MAC-minimal alveolarconcentration
• Concentration in which 50% of anesthetisedpatients do not react on skin incision
• Corelation with solubility in fat tissue
• The lower MAC is the higher strenght ofaction is
Division of inhalation agents
1. Gases:
• N2O – old, weak, used as adiuvant
• Xenon – lately introduced
2. Vapors (fluids):
• Halothan
• Enfluran
• Isofluran
• Sevofluran
• Desfluran
Features of ideal volatileanesthetic
• Not disturbing smell• Fast acting, titrable• Low solubility in blood- fast transport to brain• Stable when stored, not reacting with other
chemicals• Non- flamable, non- explosive• Low methabolism in body, fast elimination, no
accumulative effect• No depressing effect on circulatory and respiratory
systems
Nitrous oxide, laughing gas
• Old
• Weak
• Used as adiuvant
• Will be removed form medical use up to2010- destroyes ozone lawyer
Halothan
• Used for many years with good effect
• First non-flamable volatile fluid anesthetic
• MAC high
• Depression of circulatory system
• May destroy liver
• Now-a-days used only in pediatricanesthesia
Isofluran
• Disturbing smell
• May interact with heart contractivity
• Increases relaxation of muscles
Sevofluran
• Not disturbing smell- may be used for VIMA
• Low solubility in blood- fast acting
• Does not disturbs airway
• May depress circulatory system
• Methabolised to Compound A- may be renal toxic(but not confirmed in humans)
• May be used in one-day surgery
• Modern, and more and more widely used volatileanesthetic
Desfluran
• Very disturbing smell- can not be used forVIMA
• Is not methabolised
• Very fast acting
• May be used for one-day surgery
• Expensive, difficult to store (boiling temp.about 20 C)
• Modern and widelly used
• TCI is an infusion system which allows theanaesthetist to select the target bloodconcentration required for a particulareffect …
… and then to control depth of anaesthesiaby adjusting the requested targetconcentration
Defining TCI
When applied to anaesthesia
What is TCI?• Instead of setting ml/h or a dose rate (mg/kg/h),
the pump can be programmed to target arequired blood concentration.
• Effect site concentration targeting is nowincluded for certain pharmacokinetic models.
• The pump will automatically calculate howmuch is needed as induction and maintenance tomaintain that concentration.
Thiopental
• Old, one of the first used intravenousanesthetics
• Depressing effect on circulatory system
• May be used in patients with ASA 1
Ketamine
• Only intravenous anesthetic which has good analgesiaeffect
• Does not depress circulatory nor respiratory function
• Used in children, and in emergency and diseaster medicine
• Gives night mare dreams in adult patients
Etomidat
• Has no depressing effect on circulatorysystem- may be used in patients withcirculatory insufficiency
• May give musle contractions
• Depressing effect on epirenals function
• Can not be given in repeated bolus norcontinuous infusion
Propofol
• Very good anesthetic for induction andmaintaince of anesthesia with noaccumulation effect
• Titrable
• May be used in short procedures – titrateddo not effect circulatory and respiratorysystem in important manner
• Good for sedation, brain protecting effect
• May be used in TCI
Opioids
• fentanyl, alfentanil, sufentanil, remifentanil
• May be used for induction and maintain ofanesthesia in repeated bolus or continuousinfusion technique
• Sedative effect
• In high doses may be used alone for so calledopioid anesthesia- formerly used incardioanesthesia- very stable circulatory effect
Compications of use
• Respiratory depression !!!!
• Muscle rigidity in high doses
• Post-Operative Nausea and Vomitings
• Accumulation effect after prolongedadministration (except for remifentanil)
Remifentanil – modern opioidanalgesic
• T1/2 3-5 min !!
• Methabolised by non-specific tissueesterases- methabolism is not altered byrenal or liver function
• No accumulation effect after prolongedinfusion !!
NSAID
• Used as adiuvants in short, not very painfulprocedures
• Used for „preemptive analgesia” –reduction of consumption of opioids byblocking COX
Division of relaxants dependingon mechanism of action
1.nondepolarising- combine with receptor for Achlike antagonists- they are fake mediators – do notcause muscle contractation but block access toreceptors for Ach
2.depolarising- they combine with receptors for Achand cause contractation of muscle but they stayconnected with receptor blocking access to it forAch. They act like agonists.
Nondepolarising agents
-d-tubocurine – oldest deliverate of curarine-alcuronium-pancuronium – cheap and still used-pipercuronium-vercuronium-atracurium-cisatracurium-mivacurium-rocuronium
Division of nondepolarisingrelaxants due to
Chemical structure:
Miwakurium (Mivacron)Cisatrakurium (Nimbex)Atrakurium (Trakurium)
Pankuronium (Pavulon)Pipekuronium (Arduan)Rapakuronium (Raplon)Rokuronium (Esmeron)Wekuronium (Norcuron)
Benzylizochinolons:Aminosteroids:
Division of nondepolarisingrelaxants due to
time of action:
• Short acting < 3 min: still searching
• Midle time <60 min: mivacurium,atracurium, cisatracurium, rocuronium,vecuronium
• Long acting > 60 min: pancuronium,pipecuronium
Atracurium
• Elimination non-enzymatic, independent ofrenal and liver function, Hoffmanelimination- hydrolisis
• Releases histamine
• Acts about 30 min
Mivacurium
• Releases histamine
• Acts about 15-20 min – used for shortprocedures
• Methabolised by plasma esterases
Rocuronium
• Fast acting- time to 100% supresion 60 sec.
• Do not release histamine
• Acts about 60 min
• Is methabolised in liver- disfunction of livermay alter elimination
Reverse of neuromuscular blockade
• Neostigmine, piridostigmine- blockers ofacetylocholinesterase
• Must be given toghether with atropine toavoid bradycardia caused by activation ofperisympatic system
Depolarising agents
Only one: chlorsuccinilocholine
- It is methabolised by pseudocholinesterase
- Causes many complications, has manycontraindications
- Indications:Rapid sequence induction: full stomach, suspected difficult
intubation because it acts very fast < 30 seconds and short < 3min
Obligatory
• Clinical observation
• Circulatory system function: ECG, bloodpressure - Non-Invasive-Blood Pressure
• Respiratory function: SpO2 (pulsoxymetry),EtCO2
• Neuromuscular function- ie accelerometryTOF Guard
Additional- advanced
• Invasive Blood Pressure
• Haemodynamic monitoring ie Dopplertransesophageal probe
• EEG monitoring for deepness of anesthesiaie BIS (Bispectral Index), AEP - AuditoryEvoced Potentials, Entropy
Complications of generalanesthesia
• Respiratory: residual relaxants/opioidsaction
• Circulatory
• Neurological: residual anesthetics/opioidsaction
• Post-Operative Nausea and Vomitings
Mortality connected with anesthesia
•• 0,050,05 -- 4/10000 GA4/10000 GA
•• 22 -- 16 %16 % ofof surgicalsurgical patientspatients
•• 80 %80 % isis causedcaused byby humanhumanmistakemistake
Major causes of deaths
•• AirwayAirway obstructionobstruction
•• DifficultDifficult andand unefficientunefficient intubationintubation
•• InsufficientInsufficient ventillationventillation
Other causes of mortality and morbidity
•• AnoxiaAnoxia
•• HaemodynamicHaemodynamic instabilityinstability
•• AspirationAspiration
•• ToxityToxity ofof drugsdrugs –– mostlymostly inhalationinhalationagentsagents
•• AnaphylaxiaAnaphylaxia andand drugdrug interationsinterations
AIRWAY MANAGEMENTAIRWAY MANAGEMENT
Respiratory Distress vs. Respiratory FailureRespiratory Distress vs. Respiratory Failure
DistressDistress
--Increased work of breathingIncreased work of breathing
--RelativeRelative hypoxia/hypoxia/hypercapneahypercapnea
--CompensatingCompensating
FailureFailure
--Increased work of breathingIncreased work of breathing
--ProfoundProfound hypoxia/hypoxia/hypercapneahypercapnea
--DecompensatingDecompensating
It’s a constant reassessment process…
Contraindications for face maskand bag ventillation
• Hernia hiatus aesophagus
• gastric reflux
• injury of face or neck
• brochial-esophagaeal connection
• injury of trachea cartiladges
• full stomach patient, vomitings
Indications for ET(endotracheal intubation)
• Airway obstruction
• Cardio Pulmonary Resuscitation
• Artificial ventilation
• Anesthesia
• Brain injury, facial injury, facial burn,airway burn
Complications of ET• Injuries:
- theeth injury, mouth injury
- laryngs rupture
- aspiration
- bleeding
• oesophagus intubation
• one bronchus intubation
• Reactions: vomitings, coughing, apnea,laryngospasm, bradycardia, hypertension
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