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General and regional anesthesia (Cardiovascular system in anesthesia • HR…
General and regional anesthesia
Definition
partial or complete reversible analgesia and areflexia achieved pharmacologically or physically
Different levels of anaesthetic action
Local anesthesia – blockade of nerve conduction in injured area
Plexus and nerve blockades stop the pain transmission before in enters spinal cord
Spinal and epidural anesthesia block the stimuli in the spinal cord
Opioid analgesics act in the spinal cord and deeper cerebral structures
Hypnotics act in the brain, decreasing the level of consciousness
Important factors
• type of surgery
• Cardiorespiratory system
• chronic illness, drugs
• allergies, previous operations
Grading of the perioperative risk
• ASA (physical status!) American Society of Anesthesiologists
• NYHA (heart failure) New York Heart Association
• GCS (level of consciousness) Glasgow Coma Scale
ASA Classification Scheme
Code Description
I healthy patient
II A patient with mild systemic disease
III A patient with severe systemic disease
IV A patient with severe systemic disease that is threat to life
V A patient who is not expected to survive
VI A declared brain-dead organ donor
FUNCTIONAL CAPACITY
1 MET = 3,5 ml of oxigen per kg per minute
Metabolic equivalents of daily activities
1 MET = walk 100 meters on level ground
4 MET = climb stairs or walk up a hill
،، > 10 MET = strenous exercise
<4 METs = ↑↑↑ perioperative risk
specific cardiac risk factors for non-cardiac surgery
Low (<1%)
Endoscopic, Superficial, Cataract, Breast, Ortophaedic (minor)
Medium (1-5%)
Carotid endarterectomy, Head & neck, Intraperitoneal, Intrathoracic, Orthopaedic (major), Prostate
High (>5%)
Aortic vascular surgery, Peripheral vasc. surgery, Emergent major surg., Prolonged with large, fluid or blood shifts
predictors of increased perioperative cardiovascular risk
Major
Unstable coronary syndromes
Decompensated heart failure
arrhythmias & valvular disease
Intermediate
Mild angina pectoris، Previous MI or pathological Q waves
Compensated or prior heart failure
Renal insufficiency
Minor
Abnormal ECG
Rhythm other than sinus
Low functional capacity
stroke
Types of the anesthesia
General
Components
• Hypnosis – unconsciousness
• Analgesio – abolition of pain
• Areflexio – lack of reflexes
and (electively)
• Relaxatio musculorum – muscle relaxation
Intravenous
Advantages
Rapid onset
Dose titratable
Depression of laryngeal reflexes --> early insertion of LMA
Anti-emetic/anti-convulsive
Disadvantages
Venous access required
Risk of hypotension
Apnoea common
Loss of airway control
Anaphylaxis
Ideal intravenous anesthetic
• Stable in solution, light, room temperature
• Potent enough to provide surgical anesthesia
• Induction in one arm-brain circulation time
• Analgesia
• No pain on injection
• Non-epileptogenic
• No cardiovascular depression
• No respiratory depression
• No increase in ICP
• Unaffected by hepatic and renal failure
• Inactive and non-toxic metabolites
• Not teratogenic
Hypnosis
• Barbiturates - thiopental
metohexitone
• Non-Barbiturates - etomidate
propofol
ketamine
midazolam
Thiopental
• Strong, fast acting anesthetics
• Water soluble, pH 11!
• Anticonvulsant
• Short acting
• Not expensive
• Well known side effects
• Neuroprotective
• Not emetic
• crosses the placenta
• not teratogenic
disadvantages
• Hepatic metabolism, renal excretion
• Cardiovascular and Respiratory depression
• Bronchospasm
• Anaphylactic and anaphilactoid reactions
• tissue necrosis with extravasation or i.a. injection
• Increase in porphyrin levels (contraindicated in porphyria !)
Etomidate
advantages
• Fast and short acting agent
• Cardiovascular stability
• Metabolism: hepatic and plasma anticholinesterases
• Renal excretion
• ↓CBF, CMRO2, ICP, IOP
• rare allergic reactions
disadvantages
cortisol synthesis inhibition
painful at injection (less if lipid solution)
arousal at the induction
proemetic
venous thrombosis
muscle rigidity
Propofol
advantages
• Rapid induction and emergence
• Good control of anesthesia
• Decreases the cerebral metabolism
• Cardiovascular stability
• Metabolism: hepatic, renal excretion
• T1/2 – 3-4 hrs
• Pleasant dreams
• Anticonvulsant
• Anti-emetic
disadvantages
cardiovascular depression
painful at injection
respiratory depression
cost
allergic reactions
cause hiperlipidemia
Propofol Related Infusion Syndrome !!!
Midazolam
advantages
T1/2 – 5 hrs (diazepam 30 hrs)
water soluble
minimal activity of metabolites
relative cardiovascular stability (↑ HR, ↓ RR)
antagonist: flumazenil
• good amnesia (anterograde, retrograde – doubtful),
• sedation,
• anxiolysis,
• muscle relaxation
• anticonvulsant properties
• deepening of anesthesia
disadvantages
hypotension
respiratory depression
metabolism: hepatic
fast placental transfer
-T1/2 –5hrs
Ketamine
Produces sleep and dissociation
cause catalepsia, eyeball movements, unpleasant dreams
may be associated with hallucinations, diplopia or temporary blindness
anticholinergic: bronchodilatation, delirum, sympathomimetic
i.m. administration possible
preemptive analgesia (NMDA-receptor)
respiration usually not depressed
disadvantages
hypertension
tachycardia
increases salivation
increases brain oxygen consumption
increases ICP, IOP
hallucinations
nightmares
slow onset of action
Inhalational
Advantages
Avoids venepuncture
Respiration is maintained
Slow loss of reflexes
Concentration can be measured
Rapid recovery
Upper esopageal sphincer tone maintained
Disadvantages
Slow process
Irritant and unpleasant
Pollution
May cause a rise of ICP/IOP
Ideal Volatile Anesthetic
• Pleasant smell
• Fast and gentle induction
• Low blood-gas coefficient
• Stable
• Has strong analgesic and anesthetic properties
• Not metabolized
• safe
• Non-flammable
• No increase in ICP
drugs:
• Gases – nitrous oxide (N2O)
• Anesthetic vapours
halotane
enflurane
isoflurane
sevoflurane
desflurane
isoflurane
• MAC = 1,15%
•irritant smell
• Potentiation of muscle relaxants
• Cardiovascular depression
• steal syndrome
• Cardiac anti-ischemic protection
sevoflurane
• MAC = 2%
• pleasant smell
• Metabolites: fluoride compounds
• Potentiating muscle relaxation
• Cardiovascular depression
• Cardiac protection against ischemia
desflurane
• MAC = 6,35%
• Irritant smell
• Muscle relaxants potentiation
• Cardiovascular depression
• Sympathetic stimulation
N2O – nitrous oxide
• The only inorganic
• Strong analgetic, weak anaesthetic
• Increases sympathetic activity
• Influence on systemic resistance (↑SVR)
• hypoxia
• Diffuses into empty spaces
• Teratogenic
• Cardiac depression
• ↑CBF,↑ICP
• Suppresion of bone marrow
contraindications
• Ileus
• Pneumothorax
• Proceudres within inner ear
• Neurosurgery
• Air embolism
• Cardiac insufficiency
Balanced anesthesia
At least two different agents are used to achieve anesthesia
• Hypnotic + analgetic
• Hypnotic + analgetic + muscle relaxant
• Intravenous anesthetic + muscle relaxant
• Inhalational anesthetic + muscle relaxant
• Intravenous anesthetic + inhalational anesthetic
Analgesia;
• NSAIDs (more often perioperatively)
• Opioids (more often in anesthesia): (-fentanyl, morphine, pethidine, tramadole)
Regional:
temporary, reversible interruption of conduction in the neural fibres
Contraindications
• Patient refusal
• coagulopathy
• Unterated hypovolaemia
• Major infection (sepsis)
• Trauma or burns over injection sites
• Raised ICP
ESTHERS
o cocaine, procaine
o short acting
o degradation by plasma cholinestherases
o anaphylactic symptoms
o rare toxic symptoms
AMIDS
o lidocaine, bupivacaine, ropivacaine
o metabolised in liver
o toxic effects
o rare anaphylactic symptoms
Central neuraxial blockade
• Spinal : Injection into the cerebrospinal fluid, below the level of L1/2
• Epidural: Injection of large volume of LA at any level (cervical, thoracic, lumbar, sacral)
• Combined spinal-epidural (CSE)
Spinal vs. Epidural
Spinal Epidural
Onset 2-5 min 20-30 min
Duration 2-3 h (single shot) 3-5 h (single shot)
Drug Volume 2,5-4 ml 20-30 ml
Quality of block Rapid surgical Slow onset
Indications for spinal anesthesia
Region of surgery: limbs, lower abdomen, perineum, pelvis
Vascular surgery, urology, gynecology
Full stomach
systemic diseases (cardiovascular, respiratory, renal, hepatic)
Postoperative pain
Chronic pain
Bronchial asthma
Deafferentation / phantom pain
Complications of regional (esp.spinal) anesthesia
Inadvertent vascular puncture
Inadvertent spinal puncture
Inadvertent pleural puncture
Injury to the nerves or ligaments (pain)
Hypotonia
Inflammatory complications
Headache
Cranial nerves palsies (VI, phrenic)
Horse tail syndrome
Broken needle, cut / broken / damaged catheter
Clinical manifestation of local anesthetics systemic toxicity
Central nervous system (CNS)
Arousal of CNS
(anxiety, tingling tongue/lips, light headedness, metallic taste, tinnitus, slurred speech, muscle twitching, convulsions)
Depression of CNS
(coma, respiratory arrest)
Signs of cardiovascular toxicity
(rise of blood pressure, tachycardia, ventricular arrhythmias)
Signs of cardiovascular depression
(bradycardia, drop of blood pressure, conduction abnormalities, cardiac arrest)
Regional anesthesia perspectives:
Advantages
Cost effective
Techniques not requiring special skills nor equipment
Patients ASA III-IV
Drawbacks
Neurological complications 2. Anaphylactic, toxic reactions
Phases of anaesthesia
• Induction
• Conduction /maintenance of anesthesia
• Emergence and recovery
Muscle relaxants
NMBAs (neuro-muscular blocking agents)
Depolarizing
◦ Succynylcholine
Non-depolarizing
- Aminosteroids
◦ Pancuronium
◦ Pipecuronium
◦ Vecuronium
◦ Rapacuronium
◦ Rocuronium
- Benzylisoquinolinium esters
◦ Atracurium
◦ Cis-atracurium
◦ Mivacurium
Non-depolarizing muscle relaxants
Long acting (DUR25 > 50min.)
pancuronium
alcuronium
pipecuronium
Medium-time acting (DUR25 20- 50min.)
atracurium
cis-atracurium
vecuronium
rocuronium
Short acting (DUR25 < 20 min.)
mivacurium
Atracurium
• Toxic metabolite – laudanosine (convulsions)
• Histamine release
• Hoffman elimination (40%)
• T1/2 – 20 min
Cis-atracurium
• T1/2 – 30 min
• Hoffman elimination 80%
• Histamine release - minimal
Mivacurium
• Lasts twice long as suxamethonium (24 min)
• 94% metabolized by plasma cholinesterase
• Strong histamine release
Rocuronium
• T1/2 – 131 min
• Dose dependent onset of action
• N. X blockade – slight increase in HR, CO, RR
• metabolised in liver (80%)
• Caution in liver or kidney failure
• Specific antidote – sugammadex
Chlorsuccynylcholine
• T1/2 – 1-2 min
• duration of blockade 4-9 min
• 0,5-1,5 mg/kg
• Histamine release
• Arrhytmias
• Anaphylactic reactions
• Malignant hyperthermia
• Electrolyte disturbances
• Muscle pain
• Increases intraabdominal, intraocular, intracranial pressure
reversal of the blockade
• Anticholinesterases
Inhibit breakdown of acetylcholine
↑AChinNMJ
Act both on acetyl and plasma cholinesterase
Most often used: neostygmine
Widespread effects:
◦ ↓HR, SVR, RR
◦ Bronchoconstriction, increased secretion
◦ Increased salivation
◦ Increased GI tone & secretion
• Selective reversal agents
▫ Sugammadex
Synthetic γ-cyclodextrin
Specific binding of rocuronium and to smaller extent vecuronium
No use for benzylisoquinolinium derivates
Assessment of anesthesia depth
• Cardiovascular reactions [HR, BP]
• Psycho-somatic symptoms [movements, return of consciousness]
• Objective measurements [Bispectral Index (BIS), Spectral Entropy]
Cardiovascular system in anesthesia
• HR – tachy and bradyarrhythmias
• BP – hypo and hypertension
Causes of intraoperative Bradycardia
Healthy „trained” heart, Hypoxia, narcotics, B- adrenergic blockade, Vagal reflexes , MI, Increased ICP, Digitalis toxicity, Bradyarrhythmias
Causes of intraoperative Tachycardia
Decreased oxygen supply ( Hypoxemia, Hypovolaemia , Anaemia)
Increased oxygen consumption (Fever, Sepsis, Malignant hyperthermia, Hyperthyroidism)
Increased sympathetic stimulation (Inadequate anesthesia, Hypercarbia, Pheochromocytoma, Anaphylaxis, Antihypertensive, Hypovolaemia)
Drug related
• Volatile anesthetics e.g:sevoflurane, izoflurane
• musclerelaxants: pancuronium, chlorsuccynylocholine
• Antycholinergics: atropine
• Catecholamines
• Ketamine
• Aminophylline
Causes of intraoperative Hypertension
• Not proper depth of anesthesia
• Essential hypertension
• Hypercarbia
• Pheochromocytoma
• Bladder distention
• Antihypertensive
• Drugs: ketamine, pancuronium, rocuronium
• Increased ICP
Causes of intraoperative Hypotension
Decreased CO( Anesthetic drugs, Hypovolaemia, Dysrhythmia, Acidosis, Hypocalcemia, Pneumothorax, Pulmonary embolus, Cardiac tamponade)
Decreased vascular resistance (Anesthetic agents, Other drugs:( nitroprusside, nitroglicerine), Sepsis, Sympathetic spinal/epidural blockade)
Causes of intraoperative Hypoxia
• Compromised airway
• Intubation failure
• Aspiration !!!
• Inadequate oxygen concentration in the breathing circuit
• Diseases of respiratory
• Obstruction of the artificial airway or in the breathing circuit