General anesthesia Definition of anesthesia It is a reversable - - PowerPoint PPT Presentation

General anesthesia

Definition of anesthesia

• It is a reversable blocking of pain feeling in

whole body or in a part of it using pharmacology or other methods

Anesthesia- division

• Local- regional anesthesia, patient is

conscious or sedated

• General- anesthesia interact with whole

body, function of central nervous system is depressed:

– Intravenous – Inhalation (volatile) – Combined, balanced

TIVA

Total Intra Venous Anaesthesia

VIMA

Volatile Induction and 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 neuromuscular blockade

Parts of general anesthesia must be in balance

Hypnosis (anesthesia) Analgesia Lack of reflexes (muscle relaxation)

• General anesthesia

features

Lack Lack of

• f reflexes

reflexes

3

Lack Lack of

• f consciousness

consciousness

1 1

Pain Pain management management

2 2

Neuromuscular Neuromuscular blockade blockade

4 4

Stages of general anesthesia

• Stadium analgesiae (analgesia and

sedation 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 like

dressing 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 abdominal
• pening if no relaxants are used
• Possible endotracheal intubation

• IV. intoxication, overdosing
• Respiratory arrest
• If anesthesia not discontinued possible

cardiac arrest

Estimation Estimation of

• f the

the risk risk of

• f anesthesia

anesthesia ( (American American Society Society of

• f Anesthesiologists

Anesthesiologists scale scale) )

• ASA 1

ASA 1: : healthy healthy patient patient. .

• ASA 2

ASA 2: : patient patient with with stable stable, , treated treated illness illness like like arterial arterial hypertension hypertension, , diabetes diabetes melitus melitus, , asthma asthma bronchiale bronchiale, ,

• besity
• besity
• ASA

3 ASA 3: : patient patient with with systemic systemic illness illness decreasing decreasing suffitiency suffitiency like like heart heart ilness ilness, , late late infarct infarct

• ASA 4

ASA 4: : patient patient with with serious serious illness illness influencing influencing his his state state like like renal renal insuficiency insuficiency, , unstable unstable hypertension hypertension, , circulatory circulatory insuficiency insuficiency

• ASA 5

ASA 5: : patient patient in in life life treatening treatening illness illness

• ASA 6

ASA 6: : brain brain death death-

• potential

potential organ donor

• rgan donor

Premedication Premedication

Main Main reasons reasons for for premedication premedication: :

• Anxiolysis

Anxiolysis-

• lack

lack of

• f threat

threat

• Sedation

Sedation – – calming calming down down

• Amnesia

Amnesia – – lack lack of

• f memories

memories of

• f

perioperative perioperative period period

• 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 SYSTEM CIRCLE SYSTEM *HIGH HIGH-

• FLOW

FLOW FRESH GAS FLOW  3 l/min. *LOW LOW-

• FLOW

FLOW FGF ok. 1l/min. *MINIMAL MINIMAL-

• FLOW

FLOW FGF ok. 0,5 l/min.

Stages of general anesthesia

• Introduction to anesthesia (induction)
• Maintaining of anesthesia (conduction)
• Recovery from anesthesia

Anesthesia agents

1. 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

Volatile vs intravenous anesthesia

Mechanism of action of inhaled anesthetics

• Reaction depends on concentration. This depends
• n alveolar (first compartment), blood and brain

(central compartment) concentration , (third compartment- other tissue like muscles, fat- accumulation effect):

– Minute ventilation – Lung blood perfusion – Solubility in tissues

MAC-minimal alveolar concentration

• Concentration in which 50% of anesthetised

patients do not react on skin incision

• Corelation with solubility in fat tissue
• The lower MAC is the higher strenght of

action 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 volatile anesthetic

• 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 to

2010- 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 pediatric

anesthesia

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 volatile

anesthetic

Desfluran

• Very disturbing smell- can not be used for

VIMA

• 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 the

anaesthetist to select the target blood concentration required for a particular effect … … and then to control depth of anaesthesia by adjusting the requested target concentration

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 a required blood concentration.

• Effect site concentration targeting is now

included for certain pharmacokinetic models.

• The pump will automatically calculate how

much is needed as induction and maintenance to maintain that concentration.

Intravenous anesthetics

Thiopental

• Old, one of the first used intravenous

anesthetics

• Depressing effect on circulatory system
• May be used in patients with ASA 1

Ketamine

• Only intravenous anesthetic which has good analgesia

effect

• 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 circulatory

system- may be used in patients with circulatory insufficiency

• May give musle contractions
• Depressing effect on epirenals function
• Can not be given in repeated bolus nor

continuous infusion

Propofol

• Very good anesthetic for induction and

maintaince of anesthesia with no accumulation effect

• Titrable
• May be used in short procedures – titrated

do not effect circulatory and respiratory system 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 of

anesthesia in repeated bolus or continuous infusion technique

• Sedative effect
• In high doses may be used alone for so called
• pioid anesthesia- formerly used in

cardioanesthesia- very stable circulatory effect

Compications of use

• Respiratory depression !!!!
• Muscle rigidity in high doses
• Post-Operative Nausea and Vomitings
• Accumulation effect after prolonged

administration (except for remifentanil)

Remifentanil – modern opioid analgesic

• T1/2 3-5 min !!
• Methabolised by non-specific tissue

esterases- methabolism is not altered by renal or liver function

• No accumulation effect after prolonged

infusion !!

NSAID

• Used as adiuvants in short, not very painful

procedures

• Used for „preemptive analgesia” –

reduction of consumption of opioids by blocking COX

Benzodiazepines

Benzodiazepiny

• Used in anesthesia:

– Diazepam – Midazolam

• Used as adiuvants for premedication

Muscle relaxants

Division of relaxants depending

• n mechanism of action

1.nondepolarising- combine with receptor for Ach like antagonists- they are fake mediators – do not cause muscle contractation but block access to receptors for Ach 2.depolarising- they combine with receptors for Ach and cause contractation of muscle but they stay connected with receptor blocking access to it for

• Ach. 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 nondepolarising relaxants due to Chemical structure:

Miwakurium (Mivacron)

Cisatrakurium (Nimbex) Atrakurium (Trakurium)

Pankuronium (Pavulon) Pipekuronium (Arduan) Rapakuronium (Raplon) Rokuronium (Esmeron) Wekuronium (Norcuron)

Benzylizochinolons: Aminosteroids:

Division of nondepolarising relaxants 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 of

renal and liver function, Hoffman elimination- 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 short

procedures

• 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 liver

may alter elimination

Reverse of neuromuscular blockade

• Neostigmine, piridostigmine- blockers of

acetylocholinesterase

• Must be given toghether with atropine to

avoid bradycardia caused by activation of perisympatic system

Depolarising agents

Only one: chlorsuccinilocholine

• It is methabolised by pseudocholinesterase
• Causes many complications, has many

contraindications

• Indications:

Rapid sequence induction: full stomach, suspected difficult intubation because it acts very fast < 30 seconds and short < 3 min

Monitoring during general anesthesia

Obligatory

• Clinical observation
• Circulatory system function: ECG, blood

pressure - Non-Invasive-Blood Pressure

• Respiratory function: SpO2 (pulsoxymetry),

EtCO2

• Neuromuscular function- ie accelerometry

TOF Guard

Additional- advanced

• Invasive Blood Pressure
• Haemodynamic monitoring ie Doppler

transesophageal probe

• EEG monitoring for deepness of anesthesia

ie BIS (Bispectral Index), AEP - Auditory Evoced Potentials, Entropy

Complications of general anesthesia

• Respiratory: residual relaxants/opioids

action

• Circulatory
• Neurological: residual anesthetics/opioids

action

• Post-Operative Nausea and Vomitings

Mortality connected with anesthesia

• 0,05

0,05 -

• 4/10000 GA

4/10000 GA

• 2

2 -

• 16 %

16 % of

• f surgical

surgical patients patients

• 80 %

80 % is is caused caused by by human human mistake mistake

Major causes of deaths

• Airway

Airway obstruction

• bstruction
• Difficult

Difficult and and unefficient unefficient intubation intubation

• Insufficient

Insufficient ventillation ventillation

Other causes of mortality and morbidity

• Anoxia

Anoxia

• Haemodynamic

Haemodynamic instability instability

• Aspiration

Aspiration

• Toxity

Toxity of

• f drugs

drugs – – mostly mostly inhalation inhalation agents agents

• Anaphylaxia

Anaphylaxia and and drug drug interations interations

Airway management and artificial ventillation

AIRWAY MANAGEMENT AIRWAY MANAGEMENT

Respiratory Distress vs. Respiratory Failure Respiratory Distress vs. Respiratory Failure

Distress Distress

• Increased work of breathing

Increased work of breathing

• Relative

Relative hypoxia/ hypoxia/hypercapnea hypercapnea

• Compensating

Compensating Failure Failure

• Increased work of breathing

Increased work of breathing

• Profound

Profound hypoxia/ hypoxia/hypercapnea hypercapnea

• Decompensating

Decompensating

It’s a constant reassessment process…

Contraindications for face mask and 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 major
• perations ecxept for head and neck surgery
• for elective surgery- patient must be

prepared for anesthesia