ANAESTHESIA
ANAESTHESIA
ANAESTHESIOLOGY
It is that branch of medicine which
is concerned with the administration
of anaesthetics & the management
of the patient under anaesthesia.
WHAT DOES ANAESTHESIA MEAN?
The word anaesthesia is derived from the Greek: meaning insensible or without feeling.
ANAESTHETIC
also known as anaesthesiologist.
He is a doctor or a person specially trained in administering anaesthesia.
DEFINITION OF ANAESTHESIA
It is a pharmacologically induced and reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes, decreased stress response, or all of these simultaneously.
These effects can be obtained from a single drug which alone provides the correct combination of effects, or occasionally a combination of drugs (such as hypnotics, sedatives, paralytics and analgesics) to achieve very specific combinations of results.
This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience.
TOOLS OF ANAESTHESIA
1. Anaesthetic machine.
2. Monitoring system.
ANAESTHETIC MACHINE
1. Oxygen gas
supply.
2. Nitrous oxide gas
supply.
3. Flow meter.
4. Vaporizer specific
for every agent.
5. Mechanical
ventilator.
6. Tubes for
connection.
MONITORING
1. Pulse, ECG.
2. Blood pressure.
3. Oxygen saturation.
4. End tidal CO2.
5. Temperature.
6. Urine output, CVP, EEG, bispectral
index, muscle tone, ECHO, drug
concentration.
TYPES OF ANAESTHESIA
LOCAL ANAESTHESIA inhibits sensory
perception within a specific location on the
body, such as a tooth or the urinary bladder.
REGIONAL ANAESTHESIA renders a larger
area of the body insensate by blocking
transmission of nerve impulses between a
part of the body and the spinal cord. Two
frequently used types of regional anaesthesia
are spinal anaesthesia and epidural
anaesthesia.
GENERAL ANAESTHESIA refers to inhibition of sensory, motor and sympathetic nerve transmission at the level of the brain, resulting in unconsciousness and lack of sensation.
DISSOCIATIVE ANAESTHESIA uses agents that inhibit transmission of nerve impulses between higher centers of the brain (such as the cerebral cortex) and the lower centers, such as those found within the limbic system.
General anaesthetics are drugs that brings about areversible loss of all sensation and consciousness.
Cardinal signs of general anaesthesia:-
i. Loss of all sensation.
ii. Sleep and amnesia.
iii. Immobility and muscle relaxation.
iv. Abolition of reflexes.
CLASSIFICATION
1.INHALATIONAL
Gas Liquid
•Nitrous oxde •Ether
•Halothane
•Isoflurane
•Desflurane
2. INTRAVENOUS
Inducing agents Slower acting draugs
• Thiopentone sodium 1. Benzodiazepines:
Diazepam , Lorazepam ,
Midazolam.
• Methohexitone sod. 2. Dissociative anaesthesia:
Ketamine.
• Propofol 3. Opiod analgesia:
Fentanyl.
Mechanism of action
Exert their action by the activation of inhibitoryCNS receptors and their inactivation of CNSexcitatory receptors.
Ligated gated ion channels are the major targetsof anaesthetic action.
The GABA receptor gated chloride ion channel ismost important.
Many inhalational anaesthetics, barbiturates, BZDsand propofol potentiate the action of inhibitorytransmitter GABA to open chloride ion channels
Each one interacts with its own specific binding site on theGABA receptor Cl-complex.
Action of glycine in the spinal cord & medulla is augmentedby barbiturates, propofol & many inhalational anaesthetics.
This action may block responsiveness to painful stimuliresulting in immobility of the anaesthetic state.
Fluorinated anaesthetics & Barbiturates inhibit neuronalcation channel gated by nicotinic cholinergic receptor whichmay mediated analgesia & amnesia.
On the other hand N2O , Ketamine don’t affect GABA ,glycine gated Chloride channels.Rather they selectivelyinibit the excitatory NMDA type of glutamate receptor.
This receptor gates mainly Calcium ion selective cationchannels in the neurons & their inhibitor appears to be theprimary mechanism of anaesthetic action of ketamine aswell nitrous oxide.
Volatile anaesthetics have little action on this receptor.
1. INHALATION
2. INJECTION (Intravenous or Intramuscular)
Inhalation
Substances are either volatile liquids or gases , & areusually delivered using an:-
1. Anaesthesia machine.
An anaesthesia machine allows composing a mixture ofoxygen,anaesthetics & ambient air,delivering it to thepatient & machine parameters.
2. Anaesthetic chamber induction:-Uses sturdy, seenthrough containers.
Cautions-Small patients only difficult to monitor patientrisk of vomiting/regurgitation hyperthermia waste gascontamination of room & exposure of personnel.
3. Laryngeal mask airway.
4. Tracheal tube connected to some type of anaestheticvaporiser & an anaesthetic delivery system.
5. Mask induction suited for critical patients.
Caution: Prevention anaesthetic gas pollution of room use tight-fitting mask risk of stressing patient use pre-anaesthetic sedationmay be dangerous with animals with poor respiratory function.
6. Gases or vapors which produce general anaesthesia by inhalationare stored in gas cylinders & administered using flowmeters.
Liquid anaesthetics are vaporised in machine & are quitehydrophobic.
Ideal volatile anaesthetic agent offers:-
• smooth & reliable induction.
• maintainance of general anaesthesia with minimal effectson other organ systems.
• odourless or pleasant to inhale.
• safe for all ages.
• rapid in onset & offset.
• cheap to manufacture & easy to transport.
• store with long shelf life.
INJECTION
Injectable anaesthetics are used for the induction &maintainance of a state of unconsciousness.
Anaesthetics prefer to use intravenous injections , as theyare faster , less painful & more reliable than intramuscularor subcutaneous injections.
Standard dose is calculated , drawn into syringe injected asneeded directly into vein.
Techniques of Mandibular
Anesthesia
Mandibular AnesthesiaLower success rate than Maxillary anesthesia -
approx. 80-85 %
Related to bone density
Less access to nerve trunks
Mandibular Nerve BlocksInferior alveolar
Mental - Incisive
Buccal
Lingual
Gow-Gates
Akinosi
Mandibular AnesthesiaMost commonly performed technique
Has highest failure rate (15-20%)
Success depends on depositing solution within 1 mm of nerve trunk
Inferior Alveolar Nerve BlockNot a complete mandibular nerve block.
Requires supplemental buccal nerve block
May require infiltration of incisors or mesial root of
first molar
Inferior Alveolar Nerve BlockNerves anesthetized
Inferior Alveolar
Mental
Incisive
Lingual
Inferior Alveolar Nerve BlockAreas Anesthetized
Mandibular teeth to midline
Body of mandible, inferior ramus
Buccal mucosa anterior to mental foramen
Anterior 2/3 tongue & floor of mouth
Lingual soft tissue and periosteum
Inferior Alveolar Nerve BlockIndications
Multiple mandibular teeth
Buccal anterior soft tissue
Lingual anesthesia
Inferior Alveolar Nerve Block Contraindications
Infection/inflammation at injection site
Patients at risk for self injury (eg. children)
Inferior Alveolar Nerve Block10%-15% positive aspiration
Inferior Alveolar Nerve BlockAlternatives
Mental nerve block
Incisive nerve block
Anterior infiltration
Inferior Alveolar Nerve BlockAlternatives (cont.)
Periodontal ligament injection (PDL)
Gow-Gates
Akinosi
Intraseptal
Inferior Alveolar Nerve BlockTechnique
Apply topical
Area of insertion:
medial ramus, mid-coronoid notch,
level with occlusal plane (1 cm above),
3/4 posterior from coronoid notch to
pterygomandibular raphe
advance to bone (20-25 mm)
Inferior Alveolar Nerve Block Target Area
Inferior alveolar nerve, near mandibular foramen
Landmarks
Coronoid notch
Pterygomandibular raphe
Occlusal plane of mandibular posteriors
Inferior Alveolar Nerve BlockPrecautions
Do not inject if bone not contacted
Avoid forceful bone contact
Inferior Alveolar Nerve BlockFailure of Anesthesia
Injection too low
Injection too anterior
Accessory innervation
-Mylohyoid nerve
-contralateral Incisive nerve innervation
Inferior Alveolar Nerve BlockComplications
Hematoma
Trismus
Facial paralysis
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
Long Buccal Nerve BlockAnterior branch of Mandibular nerve (V3)
Provides buccal soft tissue anesthesia adjacent to
mandibular molars
Not required for most restorative procedures
Buccal Nerve BlockIndications
Anesthesia required - mucoperiosteum buccal to
mandibular molars
Contraindications
Infection/inflammation at injection site
Buccal Nerve BlockAdvantages
Technically easy
High success rate
Disadvantages
Discomfort
Buccal Nerve BlockAlternatives
Buccal infiltration
Gow-Gates
PDL
Intraseptal
Buccal Nerve BlockTechnique
Apply topicalInsertion distil and buccal to last molarTarget - Long Buccal nerve as it passes
anterior border of ramusInsert approx. 2 mm, aspirateInject 0.3 ml of solution, slowly
- 25-27 gauge needleArea of insertion:
- Mucosa adjacent to most distal
Buccal Nerve Block
Landmarks
Mandibular molars
Mucobuccal fold
Buccal Nerve BlockComplications
Hematoma (unusual)
Positive aspiration
0.7 %
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
Mental Nerve BlockTerminal branch of IAN as it exits mental foramen
Provides sensory innervation to buccal soft tissue
anterior to mental foramen, lip and chin
Mental Nerve BlockIndication
Need for anesthesia in innervated area
Contraindication
Infection/inflammation at injection site
Mental Nerve BlockAdvantages
Easy, high success rate
Usually atraumatic
Disadvantage
Hematoma
Mental Nerve BlockAlternatives
Local infiltration
PDL
Intraseptal
Inferior alveolar nerve block
Gow Gates
Mental Nerve Block
Complications
Few
Hematoma
Positive aspiration
5.7 %
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
March 5, 2007Faisal A. Quereshy, MD, DDS, FACS
Incisive Nerve BlockTerminal branch of IAN
Originates in mental foramen and proceeds
anteriorly
Good for bilateral anterior anesthesia
Not effective for anterior lingual anesthesia
Incisive Nerve BlockNerves anesthetized
Incisive
Mental
Incisive Nerve BlockAreas Anesthetized
Mandibular labial mucous membranes
Lower lip / skin of chin
Incisor, cuspid and bicuspid teeth
Incisive Nerve BlockIndication
Anesthesia of pulp or tissue required anterior
to mental foramen
Contraindication
Infection/inflammation at injection site
Incisive Nerve BlockAdvantages
High success rate
Pulpal anesthesia w/o lingual anesthesia
Disadvantages
Lack of lingual or midline anesthesia
Incisive Nerve BlockComplications
Hematoma
Positive aspiration
5.7 %
LOCAL
ANAESTHESIA
Local anaesthesia is defined as a loss of sensation
in a circumscribed area of the body caused by a
depression of excitation in nerve ending or inhibition
of the conduction process in the peripheral nerves
It does not cause loss of consciousness.
CLASSIFICATIONINJECTABLE
LOW POTENCY, SHORT DURATION
Eg: Procaine, chloroprocaine
INTERMEDIATE POTENCY AND DURATION
Eg: lidocaine, prilocaine
HIGH POTENCY, LONG DURATION
Eg: tetracaine, bupivacaine
SURFACE
SOLUBLE
Eg: cocaine, lidocaine
INSOLUBLE
Eg: benzocaine, oxethazaine
MECHANISM OF ACTION
The local anaesthetics block nerve conduction by
decreasing the entry of Na+ ions during upstroke of
action potential. As the concentration of LA is increased,
the rate of rise of action potential and maximum
depolarization decreases causing slowing of conduction.
Finally, local depolarization fails to reach the threshold
potential and conduction block ensues.
TECHNIQUES
SURFACE ANAESTHESIA
INFILTRATION ANAESTHESIA
CONDUCTION BLOCK
SPINAL ANAESTHESIA
EPIDURAL ANAESTHESIA
SURFACE ANAESTHESIA
It is produced by topical application of surface
anaesthetics to mucous membranes and abraded skin.
Only the superficial layer is anaesthetized. Onset and
duration depends on site, drug, its concentration and
form.
It is used extensively in the eye, throat, urethra and anal
canal. Topical LA is occasionally applie din mouth for
stomatitis, ulcers.
INFILTRATION
ANAESTHESIA
Dilute solution of LA is infiltrated under the skin in area of
operation- blocks sensory nerve endings. Onset of action
is almost immediate.
It is used for minor operations, eg. Incisions, excisions,
some dental procedures etc when area to be
anaesthesized is relatively small.
Relatively large amount of LA is required but motor
function is not affected.
CONDUCTION
ANAESTHESIA
This includes:
1.FIELD BLOCK: Produced by injecting the LA
subcutaneously in a manner that all nerves coming to a
particular field are blocked.
It is done for dental procedures, appendicectomy,
operations on legs and forearms etc.
2.NERVE BLOCK:
It is produced by injection of the LA around the
appropriate nerve trunks or plexuses. The muscles
supplied by injected nerve are paralysed.
In dentistry 2 important nerve blocks are there
Maxillary nerve block
Mandibular nerve block
MAXILLARY NERVE
BLOCK
MAXILLARY NERVE BLOCK
It includes:
A. posterior superior alveolar blockB. middle superior alveolar blockC. anterior superior alveolar blockD. greater palatine blockE. infraorbital blockF. nasopalatine block
pulpal anesthesia: through anesthesia of each nerve’s dental branches as they extend into the pulp tissue (via the apical foramen)
periodontal: through the interdental and interradicular branches
palatal: soft and hard tissues of the palatal periodontium (e.g. gingiva, periodontal ligaments, alveolar bone)
PSA block: recommended for maxillary molar teeth and associated buccal tissues in ONE quadrant
MSA block: recommended for maxillary premolars and associated buccal tissues
ASA block: recommended for maxillary canine and the incisors in ONE quadrant
greater palatine block: recommended for palatal tissues distal to the maxillary canine in ONE quadrant
nasopalatine block: recommended for palatal tissues between the right and left maxillary canines
POSTERIOR SUPERIOR ALVEOLAR
BLOCK• target: PSA nerve
– as it enters the maxillar through the PSA foramen on the maxilla’s infratemporal service
– into the tissues of the mucobuccal fold at the apex of the 2nd maxillary molar mandible is extended toward the side of the injection, pull the tissues at the injection site until taut
– needle is inserted distal and medial to the tooth and maxilla
– depth varies from 10 to 16 mm depending on age of patient
• no overt symptoms (e.g. no lip or tongue involvement)
• can damage the pterygoid plexus and maxillary artery
MIDDLE SUPERIOR ALVEOLAR
BLOCKlimited clinical usefulness
can be used to extend the infraorbital block distal to the maxillary canine
can be indicated for work on maxillary pre-molars and mesiobuccal root of 1st molar
if the MSA is absent – area is innervated by the ASA
blocks the pulp tissue of the 1st and 2nd maxillary premolars and possibly the 1st molar + associated buccal tissues and alveolar bone
useful for periodontal work in this area
to block the palatine tissues in this area – may require a greater palatine block
target area: MSA nerve at the apex of the maxillary
2nd premolar mandible extended towards injection
site
stretch the upper lip to tighten the
injection site
needle is inserted into the mucobuccal
fold
tip is located well above the apex of the
2nd premolar
harmless tingling or numbness of the upper lip
overinsertion is rare
ANTERIOR SUPERIOR ALVEOLAR
BLOCK
can be considered a local infiltration
used in conjunction with an MSA block
the ASA nerve can cross the midline of the maxilla onto the opposite side!
used in procedures involving the maxillary canines and incisors and their associated facial tissues
pulpal and facial tissues involved –restorative and periodontal work
blocks the pulp tissue + the gingiva, periodontal ligaments and alveolar bone in that area
target: ASA nerve at the apex of the maxillary canine
at the mucobuccal fold at the apex of the maxillary
canine
harmless tingling or numbness of the upper lip
overinsertion is rare
INFRAORBITAL NERVE BLOCK
anesthetizes both the MSA and ASA
used for anesthesia of the maxillary premolars, canine and incisors
indicated when more than one premolar or anterior teeth
pulpal tissues – for restorative workfacial tissues – for periodontal work
also numbs the gingiva, periodontal ligaments and alveolar bone in that area
the maxillary central incisor may also be innervated by the nasopalatine nerve branches
target: union of the ASA and MSA with the IO nerve after the IO enters the IO foramenalso anesthesizes the lower eyelid, side of nose and upper lipIO foramen is gently palpated along the IO rim
move slightly down about 10mm until you feel the depression of the IO foramen locate the tissues at the mucobuccal fold at the apex of the 1st
premolarplace one finger at the IO foramen and the other on the injection site –figure 9-17locate the IO foramen, retract the upper lip and pull the tissues tautthe needle is inserted parallel to the long axis of the tooth to avoid hitting the bone
GREATER PALATINE BLOCKused in restorative procedures that involve more than two maxillary posterior teeth or palatal tissues distal to the canine
also used in periodontal work – since it blocks the associated lingual tissues
anesthetizes the posterior portion of the hard palate – from the 1st premolar to the molars and medially to the palate midline
does NOT provide pulpal anesthesia – may also need to use ASA, PSA, MSA or IO blocks
may also need to be combined with nasopalatineblock
• target: GP nerve as it enters the GP foramen located at the junction of the maxillary alveolar process and the hard palate – at the maxillary 2nd or 3rd molar
• palpate the GP foramen –midway between the median palatine raphe and lingual gingival margin of the molar tooth
• can reduce discomfort by applying pressure to the site before and during the injection-produces a dull ache to block pain impulses
-also slow deposition of anaesthesia will also help
• needle is inserted at a 90 degree angle to the palate
NASOPALATINE BLOCKuseful for anesthesia of the bilateral portion of the hard palate
from the mesial of the right maxillary 1st premolar to the mesial of the left 1st premolar
for palatal soft tissue anesthesia periodontal treatment
required for two or more anterior maxillary teeth
for restorative procedures or extraction of the anterior maxillary teeth – may need an ASA or MSA block also
blocks both right and left nerves
target: both right and left nerves as they enter the incisive foramen from the mucosa of the anterior hard palate
posterior to the incisive papilla
injection site is lateral to the incisive papilla
head turned to the left or right
inserted at a 45 degree angle about 6-10 mm –gently contact the maxillary bone and withdraw about 1mm before administering
can reduce discomfort by applying pressure to the site before and during the injection
produces a dull ache to block pain impulsesalso slow deposition of anesthesia will also help
can anaesthetize the labial tissues between the central incisors prior to palatal block
can block some branches of the nasopalatine prior to injection
Anatomy. Skin
Subcutaneous fats
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
Dura
Subarachnoid space
The spinal cord usually ends at the level of L1in adults and L3 in children.
Dural puncture above these levels is asso with
a slight risk of damaging the spinal cord
and is best avoided.
An important landmark to remember is that
a line joining the top of the iliac crests is
at L4 to L4/5
Mechanism of action
Local anaesthetic solution injected into the subarachnoid
space blocks conduction of impulses along all nerves with
which it comes in contact, although some nerves are more
easily blocked than others. There are three classes of nerve:
motor, sensory and autonomic. Stimulation of the motor
nerves causes muscles to contract and when they are blocked,
muscle paralysis results. Sensory nerves transmit sensations
such as touch and pain to the spinal cord and from there to
the brain, whilst autonomic nerves control the calibre of
blood vessels, heart rate, gut contraction.
Indications
Spinal anaesthesia is best reserved for
operations below the umbilicus e.g. hernia
repairs, gynaecological and urological
operations and any operation on the perineum or genitalia.
Older patients and those with systemic
disease such as chronic respiratory disease,
hepatic, renal and endocrine disorders such as diabetes.
It is suitable for managing patients with trauma
In obstetrics, it is ideal for manual removal of
a retained placenta (again, provided there is no hypovolaemia).
Advantages
1.Cost
2.Patient satisfaction
3.Respiratory disease
4.Diabetic patients
5.Muscle relaxation
6.Blood loss during operation is less
Contra-indications to Spinal Anaesthesia:-
Absolute:
1.Inadequate drugs and equipment
2.Coagulopathy or other bleeding disorders
3.Severe hypovolaemia(Shock)
4.Patient refusal
5.Increased Intracranial Pressure
6.Severe aortic stenosis
7.Severe Mitral stenosis
Local Anaesthetics for Spinal Anaesthesia:-
Local anaesthetic agents are either heavier
(hyperbaric), lighter (hypobaric), or have the
same specific gravity (isobaric) as the CSF.
Hyperbaric solutions tend to spread below the
level of the injection, while isobaric solutions
are not influenced in this way. It is easier to
predict the spread of spinal anaesthesia
when using a hyperbaric agent. Isobaric
preparations may be made hyperbaric by the
addition of dextrose.
Bupivacaine (Marcaine):- 0.5% hyperbaric (heavy) bupivacaine is the best agent to use if it is available. 0.5% plain bupivacaine is also popular. Bupivacaine lasts longer than most other spinal anaesthetics: usually 2-3 hours.
Lignocaine (Lidocaine/Xylocaine):- Best
results are obtained with 5% hyperbaric
(heavy) lignocaine which lasts 45-90 minutes.
Cinchocaine (Nupercaine, Dibucaine, Percaine, Sovcaine):- 0.5% hyperbaric (heavy) solution is similar to bupivacaine.
Amethocaine (Tetracaine, Pantocaine,
Pontocaine, Decicain, Butethanol, Anethaine,
Dikain):- A 1% solution can be prepared with
dextrose, saline or water for injection.
Mepivacaine (Scandicaine, Carbocaine,
Meaverin) :- 4% hyperbaric (heavy)
solution is similar to lignocaine.
Pre-loading :-
All patients having spinal anaesthesia must have a
large intravenous cannula inserted and be given
intravenous fluids immediately before the spinal.
The volume of fluid given will vary with the age of the
patient and the extent of the proposed block. A
young, fit man having a hernia repair may only need
500 mls. Older patients are not able to compensate
as efficiently as the young for spinal-induced
vasodilation and hypotension and may need 1000mls
for a similar procedure. If a high block is planned,
at least a 1000mls should be given to all patients.
The fluid should preferably be normal saline or ringer lactate.
5% dextrose is readily metabolised and so is not effective in maintaining the blood pressure.
Position:-
1.Lateral ( Lt lateral )
2.Sitting
Males tend to have wider shoulders than hips and so
are in a slight "head up" position when lying on their
sides, whilst for females with their wider hips, the
opposite is true.
LEFT LATERAL POSITION
SITTING POSITION
The sitting position is preferable in the obese
whereas the lateral is better for uncooperative or
sedated patients.
Complication
1.Immediate complication
- Hypotension and Cardiac arrest.
- Total spinal block leading to respiratory arrest.
- Urinary retention.
- Epidural hematoma, Bleeding.
2.Late complication
- Post dural puncture headache (PDPH)
- Backache
- Bacterial meningitis
Treatment of spinal headache:
1.Remain lying flat in bed as this relieves the pain.
2.They should be encouraged to drink freely or,
if necessary, be given intravenous fluids to maintain adequate hydration.
3.Simple analgesics such as paracetamol, aspirin or codeine may be helpful.
Caffeine containing drinks such as tea, coffee or Coca-Cola are often helpful.
Prolonged or severe headache may be treated with epidural blood patch performed by aseptically injecting 15-20ml of the patient's own blood into the epidural space. This then clots and seals the hole and prevents further leakage of CSF.
It used to be thought that bedrest for 24 hours following a spinal anaesthetic would help reduce the incidence of headache.
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