Anesthesia

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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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Anesthesia

• 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 upper
  abdominal surgery, thoracic surgery, head and
  neck surgery, shoulder surgery etc.
• -surgical procedures that significally
  interfere with vital functions neurosurgery,
  thoracic surgery, cardiac surgery, surgery of the
  aorta etc.

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General anesthesia indications

• Indications based on the patient condition
• -different pathologies or ongoing
  treatments that make the regional anesthesia
  tachniques contraindicated 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.

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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 by
  ventilation with minimal metabolization.
• They result in sedation, analgesia and light
  muscle relaxation.

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• The potency of an inhalatory anesthetic
• MAC (minimal alveolar concentration)
• the alveolar concentration of the anesthetic
  that abolishes the movements caused by the skin
  incision in 50 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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Inhalant anesthetic Class Concentration in balanced anesthesia Advantages/disadvantages Side effects
Nitrous oxide Gaseous 40-66 Light analgesia Accumulation in airway spaces Risk of hypoxemia Euforia
Halothane Volatile 1,5-2 Bronchodilatation Slow dynamics Cardio-vascular depression
Isoflurane Volatile 1,5-2 Bronchodilatation Medium dynamics Vasodilatation
Sevoflurane Volatile 2-3 Bronchodilatation Fast dynamics Cardio-vascular stability Compound A
Desflurane Volatile 6-8 Airway irritant Special vapporiser Sympathetic stimulation
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• Intravenous anesthetics
• Short acting
• Barbiturates ? metohexital
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  thiopental, tiamital
• Imidazolic compounds ? etomidate
• Alkylphenols ? propofol
• Steroids ? 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 circulatory
  depression

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• PROPOFOL
• -very liposoluble fatty acid
• -hepatic metabolisation in great extent ? short
  effect
• Pharmacodynamic action
• -pharmacologic effects similar with those of
  Thiopental
• -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 of catecholamines
• -bronchodilatatory effect

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Hypnotic Class Induction dose Single dose duration of action Side effects
Thiopental Short acting barbituric 2-4 mg/kg 5-10 min Arterial hypotension, respiratory depression, tachycardia, decreases the cardiac output
Propofol Alkylphenol 1-2 mg/kg 5-10 min Arterial hypotension, respiratory depression, tachycardia
Etomidat Imidazolic compound 0,3 mg/kg 5-10 min Adrenal glad inhibition
Diazepam Benzodiazepines 0,3 mg/kg 10-60 min Interindividual response variability
Midazolam Benzodiazepines 0,2-0,3 mg/kg 5-15 min Respiratory depression
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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 because the 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 Medium dose Single dose duration of action Side effects
Morphine µ Agonist 0,2 mg/kg 30-60 min Respiratory depression, sedation. hTA, bradycardia
Pethidine µ/? Agonist 1 mg/kg 20-30 min Sedation, nausea/vomiting, HTA, tachycardia
Fentanil µ Agonist 5-15 µg/kg 20 min Respiratory depression
Sufentanil µ Agonist 0,3-1 µg/kg Respiratory depression
Alfentanil µ Agonist 5-50 µg/kg Respiratory depression
Remifentanil µ Agonist 0,5-1 µg/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 physiologic stimulus for the muscular
  contraction
• -NO action on the CNS, NO loss of
  consciousness, NO analgesia
• -utilized for the facilitation of the
  airway instrumentation, of mechanical ventilation
  and of the surgical intervention
• -results in alveolar hypoventilation or
  apnea by the action on the respiratory muscles
• -minimal cardio-vascular effects.

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Muscular relaxant Class Intubation dose Single dose duration of action Particular instructions
Succinylcholine 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 Cardiac affections
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 Short interventions
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
• -CO2 scavenger 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 or a qualified staff member
  throughout the duration of the anesthesia.
• Standard II
• -oxygenation inspiratory oxygen
  concentration (FiO2), pulsoxymetry (SpO2)
• -ventilation clinical evaluation,
  auscultation, capnography
• -circulation electrocardioscopy
  (continuous), noninvasive arterial blood
  pressure and pulse measurement
• -body temperature.

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Monitoring
Respiratory Airway pressure, tidal volume, minute ventilation, respiratory rate, O2/CO2 inspiratory concentration, concentration of volatile anesthetic agent, pulsoxymetry
Cardiovascular Non-invasive arterial pressure, multiple leads ECG, computerized analysis of ST segment, central venous pressure, pulmonary artery pressure (systolic, medium, diastolic, wedge) cardiac output, extra-vascular pulmonary water, peripheral vascular resistance, ScvO2, SvO2.
Hypnosis BIS (bispectral index)
Muscle relaxation Peripheral nerve stimulator
Renal Diuresis
Temperature Central, peripheral
Acid - base equilibrium Blood gas analysis
Electrolytes Na, K, Cl, Ca
Haematological analysis, coagulation studies Platelets, aPTT, INR
Oxygen transportation 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 in the 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 the state of general
  anesthesia
• -CNS depression, ventilatory,
  cardiovascular depression, muscle relaxation
• -securing the airway.
• Maintenace phase
• -providing the adequate depth of
  anesthesia by administering anesthetics,
  analgesics and muscle relaxant agents.
• Emergency phase
• -the interruption of the administration
  of all volatile or intravenous 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, myocardial ischemia, arrhythmia , hypovolemia, low cardiac output
CNS Convulsions, shivers, post anoxic encephalopathy, paresis by 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 venous thrombosis
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
  vital functions
• -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 for peripartum 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 during tracheal intubation
in regional anesthesia we frequently use the
combination between a local anesthetic and
adrenaline, 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 nerves blockade
• Single-shot
• Catheter

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• Local anesthesia
• contact
• topical - skin, mucous membrane application
• tissue infiltration

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• Monitored anesthesia care

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Monitored anesthesia care
- intravenous administration of
anxiolytic, sedative, analgesic and amnesic drugs
either isolated or supplementing a regional
anesthesia procedure - indicated in
painful diagnostic or therapeutic procedures or
supplementing a inappropiate regional block
- the CPR equipments must be close-by at all
times - complications respiratory
depression with hypoventilation and loss of
airway protection.
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