10. Anesthesia

7/28/2019 10. Anesthesia

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Nothing in life is to be feared.

It is only to be understood.Marie Curie (`868-1934)


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General anesthesia

Regional anesthesia

Monitored anesthesia care


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General anesthesia


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Before him surgery was agony.Epitaph on a monument honoring W. Morton


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General anesthesia

The goals of general anesthesia:

- Mandatory: -amnesia/sedation/hypnosis

-analgesia

-maintenance of homeostasis

- Optionally: -muscle relaxation


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General anesthesia indications

Indications based on the surgical procedure:

-surgical procedures requiring analgesia and

muscle relaxation, that cannot be performed

using regional anesthesia techniques: upperabdominal surgery, thoracic surgery, head and

neck surgery, shoulder surgery etc.

-surgical procedures that significally interfere

with vital functions: neurosurgery, thoracicsurgery, cardiac surgery, surgery of the aorta etc.


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Indicationsbased on the patient condition:

-different pathologies or ongoing treatments that

make the regional anesthesia tachniquescontraindicated: the patients with coagulation

disorders, anticoagulant treatments, infections or other

lesions in the area where a regional anesthesia

procedure would be performed;-systemic diseases with definite functional

limitations: the patient with respiratory insufficency,

shock, coma, major hydroelectrolytic or acido-basic

imbalance.

General anesthesia indications


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Drugs used for general anesthesia

Hypnosis

Analgesia

Muscle relaxation

Maintenance of homeostasis

can all be achieved by administering

one or more drugs


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Drugs used for general anesthesia

Inhalatory anesthetics:-gaseous form

nitrous oxide

-volatile liquids

halothane, isoflurane, sevoflurane si desflurane

The advantage of entering and leaving the body byventilation with minimal metabolization.

They result in sedation, analgesia and light musclerelaxation.


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The potency of an inhalatory anesthetic

MAC (minimal alveolar concentration)

= the alveolar concentration of the anesthetic thatabolishes the movements caused by the skin incision in50% of the patients

Each inhalatory anesthetic has its own specific MAC.

Modern anesthesia - new types of MAC: MAC intubation ( MAC that facilitates the intubation in 50% of the patients); MAC bar (MAC that abolishes the hemodynamic response in 50% of the

patients); MAC awake (MAC at which awakening occurs in 50% of the patients).


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Inhalantanesthetic

Class Concentrationin balancedanesthesia

Advantages/disadvantages Side effects

Nitrousoxide

Gaseous 40-66% Light analgesiaAccumulation in airwayspaces

Risk ofhypoxemiaEuforia

Halothane Volatile 1,5-2% BronchodilatationSlow dynamics

Cardio-vasculardepression

Isoflurane Volatile 1,5-2% BronchodilatationMedium dynamics

Vasodilatation

Sevoflurane Volatile 2-3% Bronchodilatation

Fast dynamicsCardio-vascular stability

Compound A

Desflurane Volatile 6-8% Airway irritantSpecial vapporiser

Sympatheticstimulation


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Intravenous anesthetics:

Short acting:

Barbiturates metohexitalthiopental, tiamital

Imidazolic compounds etomidate

Alkylphenols propofolSteroids eltanolone

Long acting:

Ketamine

Benzodiazepines diazepam, midazolam


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THIOPENTAL:

-very rapid induction; maximal effect in 40 s;

-superficial anesthetic sleep;

-NO an analgesic effect;

-weak muscle relaxation.

Administration: slow i.v.

Side effects: risk of respiratory and circulatorydepression


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PROPOFOL

-very liposoluble fatty acid;

-hepatic metabolisation in great extent short effect;

Pharmacodynamic action:

-pharmacologic effects similar with those ofThiopental;

-less residual effects.


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KETAMINE

Pharmacodynamic action:

Dissociative anesthetic:- dissociation from the environment

- superficial sleep

- strong analgesia

Advantages:-No respiratory depressant effect;

-hemodynamic stability by the release ofcatecholamines

-bronchodilatatory effect


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Hypnotic Class Inductiondose

Single doseduration ofaction

Side effects

Thiopental Short actingbarbituric

2-4 mg/kg 5-10 min Arterialhypotension,respiratorydepression,tachycardia,decreases thecardiac output

Propofol Alkylphenol 1-2 mg/kg 5-10 min Arterialhypotension,respiratorydepression,tachycardia

Etomidat Imidazoliccompound

0,3 mg/kg 5-10 min Adrenal gladinhibition

Diazepam Benzodiazepines 0,3 mg/kg 10-60 min Interindividualresponsevariability

Midazolam Benzodiazepines 0,2-0,3mg/kg

5-15 min Respiratorydepression


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Analgetics:

Opioids:

-the class of analgesics with the broadest intra-anesthetic utilisation;

-profound dose-dependant analgesia;

-in spite of their quasi-constant use during general

anesthesia, the opioids are not anesthetics becausethe loss of consciousness is not a regular effect

-they regularly result in respiratory dose-dependent depression. Cardiovascular depression is a

variable effect.


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Opioids Class Mediumdose


Side effects

Morphine Agonist 0,2 mg/kg 30-60 min Respiratory depression,sedation. hTA,bradycardia

Pethidine /Agonist

1 mg/kg 20-30 min Sedation,nausea/vomiting, HTA,tachycardia

Fentanil Agonist 5-15g/kg

20 min Respiratory depression

Sufentanil Agonist 0,3-1g/kg

Respiratory depression

Alfentanil Agonist 5-50g/kg

Respiratory depression

Remifentanil

Agonist 0,5-1g/kg

1-3 min Respiratory depression

Buprenorphine

Agonist/antagonist

0,3 mg 3-4 ore Ceilling effect


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Muscle relaxants:

-substances that act at the neuromuscular junction

level and prevent the transmission of the physiologicstimulus for the muscular contraction;

-NO action on the CNS, NO loss of consciousness,NO analgesia;

-utilized for the facilitation of the airwayinstrumentation, of mechanical ventilation and of thesurgical intervention;

-results in alveolar hypoventilation or apnea by the

action on the respiratory muscles;

-minimal cardio-vascular effects.


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Muscularrelaxant

Class Intubationdose


Particularinstructions

Succinylcholi

ne

D 1-1,5 mg/kg 10-15 min Full stomach

Pancuronium ND 0,1 mg/kg 30-40 min Bradycardia

Vecuronium ND 0,08 mg/kg 20-30 min Cardiacaffections

Atracurium ND 0,5 mg/kg 20 min Kidney failure

Cisatracurium ND 0,2 mg/kg 20 min Kidney failure

Mivacurium ND 0,2 mg/kg 10-15 min Shortinterventions

Rocuronium ND 0,6-0,9 mg/kg 30-60 min Full stomach


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Anesthesia apparatus


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Anesthesia Apparatus

Components:-connection with the sources

of medical fluids

-flowmeters

-vaporizers-anesthetic circuit

-CO2scavenger system

-balloon ventilation system

-overpressure valve-mechanical ventilation module

-emergency oxygen delivery circuit


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-ventilation parameters setting module;

-ventilation parameters and inhalation anesthetics

monitoring module;-alarm module;

-vacuum system (sucction).


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Intraanesthesic monitoring


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Intraanesthesic monitoring

Standard I:

-the presence in the room of an anesthesiologist ora qualified staff member throughout the duration ofthe anesthesia.

Standard II:

-oxygenation: inspiratory oxygen concentration(FiO2), pulsoxymetry (SpO2);

-ventilation: clinical evaluation, auscultation,

capnography;-circulation: electrocardioscopy (continuous),

noninvasive arterial blood pressure and pulsemeasurement;

-body temperature.


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Monitoring

Respiratory Airway pressure, tidal volume, minute ventilation, respiratory rate,O2/CO2 inspiratory concentration, concentration of volatileanesthetic agent, pulsoxymetry

Cardiovascular Non-invasive arterial pressure, multiple leads ECG, computerizedanalysis of ST segment, central venous pressure, pulmonaryartery pressure (systolic, medium, diastolic, wedge) cardiacoutput, extra-vascular pulmonary water, peripheral vascularresistance, ScvO2, SvO2.

Hypnosis BIS (bispectral index)

Muscle relaxation Peripheral nerve stimulatorRenal Diuresis

Temperature Central, peripheral

Acid - baseequilibrium

Blood gas analysis

Electrolytes Na, K, Cl, Ca

Haematologicalanalysis, coagulationstudies

Platelets, aPTT, INR

Oxygentransportation

Hb, Ht, cardiac output, SaO2, PaO2

Metabolic Glucose


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Preanesthetic visit


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Preanesthetic exam:

-psychological preparation of the patient;

-clinical and laboratory evaluation of the patient;

-asignement to an anesthetic risk group (ASA scale)

-choosing the anesthetic technique and obtaining the

informed consent;

-set up of an anesthetic plan.

Risk I Patient without systemic diseases

Risk II Patient with systemic diseases without functional limitation

Risk III Patient with systemic diseases with functional limitation

Risk IV Patient with uncompensated systemic disease

Risk V Dying patient

Risk VI Brain dead patient, organ donor

E Emergency procedure


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Optimizing the patient status:

-the correction of dysfunctions and diseases inthe preoperative period.

Premedication :

-reduced anxiety and reduced need for intra-operative anesthetics;

-decreasing certain risks (parasympathetic

reflexes, the risk of aspiration);

-the facilitation of postoperative analgesia.


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Phases of general anesthesia

Induction phase:

-the period of transition from the state of conscious to thestate of general anesthesia;

-CNS depression, ventilatory, cardiovascular depression,muscle relaxation;

-securing the airway.

Maintenace phase:

-providing the adequate depth of anesthesia byadministering anesthetics, analgesics and muscle relaxantagents.

Emergency phase:

-the interruption of the administration of all volatile orintravenous anesthetic agents;

-the antagonisation of the muscle relaxant drug.


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General anesthesia techniques

Balanced anesthesia;

Intravenous anesthesia;

Volatile anesthesia;

Combined techniques of general and regional

anesthesia:

-general anesthesia + epidural anesthesia.


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General anesthesia complications

Respiratory Hypoxemia, hypercapnia laryngeal spasm, bronchospasm,aspiration, ARDS, atelectasis

Cardio-vascular High/low blood pressure, tachy/bradycardia, myocardialischemia, arrhythmia , hypovolemia, low cardiac output

CNS Convulsions, shivers, post anoxic encephalopathy, paresisby compression or elongation of peripheral nerves

Digestive Vomiting or regurgitation, hiccup

Renal Oligo/anuria, urinary retention, pre - renal failure

Metabolice Hyper/hypoglycemia, malignant hyperthermia

Hidro-electrolitics Extracellular space expansion (interstitial oedema),hypo/hyperkalemia, hypocalcemia

Acid-base Hypercloremic metabolic acidosis, lactacidemic

Coagulation Thrombocytopenia, dilutional coagulopathy, deep venousthrombosis

Allergical Cutaneous eruptions, Quincke oedema, bronchospasm,anaphylactic shock

Cutaneous Decubitus injury, accidental burns


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Regional anesthesia Subarachnoid (spinal)

Epidural

Sequential

Caudal


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Regional anesthesia Indications:

-the area can be anesthetised using regional blocks;

-the surgical procedure does not affect the vitalfunctions;

-patient's informed consent; Contraindications:

-patient's refusal;

-active coagulation disorders or anticoagulant

treatment;

-infections or haematoma at injection site;

-neurological deficit and lack of cooperation.


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Spinal Anethesia:

analgesia

muscle relaxation

sympathetic blockade

-sympathetic blockade: hypotension, bradycardia,

urinary retention;

-hypovolemia is an absolute contraindication of spinal

anesthesia;

-epidural analgesia is the standard procedure forperipartum analgesia;

-complications: systemic (high spred of anesthetic-

total spinal anesthesia or systemic toxicity), headache.


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Local anesthetics

Amides Esters

Lidocain Prilocain Procain

Mepivacain Etidocain Tetracain

Bupivacain Ropivacain Benzocain

Clinical use of local anesthetics

Central regional anesthesia/analgesia

Regional intravenous anesthesia

Peripheral nerve block or plexus

Infiltration anesthesia

Local anesthesia

Blocking of thehemodynamic response duringtracheal intubation

in regional anesthesia we frequently use the combination between a local anesthetic andadrenaline, an opioid or clonidine, increasing the duration and quality of the block


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During regional anesthesia mandatory equipments:

Anesthesia delivery system

Equipments and materials for airway management

Oxygen source

Monitoring: ventilation, oxygenation, circulation, blood

pressure, EKG.


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Spinal anesthesia (sub-arachnoid block)


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Epidural anesthesia


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Sequential (combined) anesthesia

spinal / epidural


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Caudal anesthesia


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Plexus anesthesia or peripheral nervesblockade

Single-shot

Catheter


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Local anesthesiacontact

topical - skin, mucous membrane application

tissue infiltration


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- intravenous administration of anxiolytic, sedative,

analgesic and amnesic drugs either isolated orsupplementing a regional anesthesia procedure;

- indicated in: painful diagnostic or therapeuticprocedures or supplementing a inappropiate regional

block;- the CPR equipments must be close-by at all times;

- complications: respiratory depression withhypoventilation and loss of airway protection.


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10. Anesthesia