General anesthesia

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

TIVA

Total

Intra

Venous

Anaesthesia

VIMA

Volatile

Inductionand

Maintain

Anaesthesia

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

II. Excitation stage

• Possible uncontrolled movements,vomitings

• Increase in respiratory rate

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

SEMIOPEN

SEMICLOSED

CLOSED

• 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

Volatilevs

intravenous anesthesia

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

Inhalation agents

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

Intravenous anesthesia

Target

Controlled

Infusion

TCI

• 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.

Intravenous anesthetics

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

Pain killers

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

Benzodiazepines

Benzodiazepiny

• Used in anesthesia:

– Diazepam

– Midazolam

• Used as adiuvants for premedication

Muscle relaxants

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

Cisatracurium

• One of stereoisomers of atracurium,

• Do not release histamine

• Acts about 60 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

Monitoring during generalanesthesia

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 management andartificial ventillation

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

Alternative airway management

• Laryngeal mask- for short, not majoroperations ecxept for head and neck surgery

• for elective surgery- patient must beprepared for anesthesia