Anasthesia 4

Regional Anaesthesia

• Regional anaesthesia involves blocking nerves in a specific region of the body.

1. Central Nerve Blocks

• These involve targeting nerves closer to the central nervous system.

• Spinal:
• Subarachnoid block
• Anesthesia injected into the subarachnoid space.

• Epidural:
• Anesthesia injected into the epidural space.

• Caudal anaesthesia:
• through the sacral hiatus.



• Type of epidural anasthesia

• Insertion at S4-S5 vertebral junction
• directed towards S2 segment.

• No risk of spinal cord injury.

• USG guidance can be used

• Administered only in postoperative phase in children > adults

• Increase risk of infection (due to bowel and bladder immaturity).

2. Peripheral Nerve Blocks

• Any nerve blocks

Spinal Anaesthesia/Subarachnoid Block

• Into the subarachnoid space.

Indications

• Below umbilical surgeries.

Absolute Contraindications (C/I)

• Patient refusal.

• Increased Intracranial Pressure (ICP).

• Severe hypovolemia/ shock

• Severe mitral and aortic stenosis.

• Bleeding tendencies.

• Local site infection.

• Drug allergy.

Site

• Adults:
• L3 - L4 (lumbar vertebrae).

• Children:
• L4 - L5 (lumbar vertebrae).

Procedure

• Preparation:
• Strict aseptic precaution.

• Position:
• Sitting/left lateral/prone.

• Projection of needle:
• Layers encountered:
• Skin → Subcutaneous tissue → Supraspinous ligament → Interspinous ligament → Ligamentum flavum → Dura mater → Arachnoid mater.

1. General anesthesia with IV induction by ketamine

2. Spinal anesthesia up to L4 level

3. General anesthesia with IV induction by propofol followed by maintenance with fluranes

4. Sedation and epidural analgesia

Spinal Anesthesia for Cesarean Section

• At T4 level

• Desired sensory level:
• T4 dermatome (nipple level).

• Drugs used:
• Bupivacaine (hyperbaric): 10–12 mg.
• Fentanyl (20–25 µg):
• improves block quality,
• prolongs duration,
• reduces shivering, minimizes referred pain.

• Epidural anesthesia → T10 nerve root.

• For instrumental deliveries → pudendal nerve block

Needles for Spinal Anaesthesia

Based on Action on Dura

Lumbar puncture

• L3-L4 or L4-L5;
• choose widest space.

Indications of CT before Lumbar Puncture: FAILS

• Focal neurological deficit

• Altered mental status

• Immuno-compromised

• Lesion

• Seizure

• Papilledema

Needles

• Dura cutting:
• Increased Post Dural Puncture Headache (PDPH).
• Pointed edge
• Technically easier.
• Examples: Quincke (most common).
• Mnemonic: Kuttunnath → quincke

• Dura splitting:
• Decreased PDPH.
• less traumatic
• Technically difficult.
• Examples: Whitacre, Sprotte
• Mnemonic: Wisely (Whitacre Sprotte) Split

• Steps
• Advance needle cephalad (bevel up).

• After CSF appears
• re-insert stylet halfway to prevent herniation.

Meningitis cause in Neonates

• Escherichia coli (most common)
• 0 - 2 months

• Group B Streptococcus (most common)
• > 2 months

• Listeria monocytogenes
• PALCAM media,
• tumbling motility
• treat with ampicillin

Meningitis cause in Children, Adults, and Elderly

• Streptococcus pneumoniae (most common)

• Neisseria meningitidis (meningococcus)

• Haemophilus influenzae type B (Hib)
• risk of deafness if no Hib vaccine

CSF tubes

Tube	Purpose	Collected CSF (mL)
1	Glucose, protein (biochemistry)	0.5
2	Cell count, DC (hematology)	1
3	Gram stain, CSF culture Latex agglutination (Immunology) • partially treated case of meningitis if required	2 - 5
4	Hold for repeat (in storage facility at 37°C)	ㅤ

Based on Needle Circumference (Gauge)

• ↓ gauge → thicker needle → ↑ PDPH.

Post Dural Puncture Headache (PDPH)

• PDPH is a common complication after dural puncture.

Incidence

• Most common after Lower Segment Caesarean Section (LSCS).

Characteristics

• Dull boring type pain with mild-moderate intensity.

• Seen 24 to 48 hours after symptoms at occipital and frontal region.

• Aggravating factors include change in posture.

Management (mx)

• Adequate bed rest and plenty of oral fluids.

• Analgesia: Caffeine + paracetamol.

• Severe cases: Epidural blood patch.
• Take patients blood → inject into epidural spac

Transient neurological symptoms

• Highest with Lidocaine

• Occur within 48 hrs after spinal

• Buttock pain with radiation to limbs

Factors Affecting Level of Anaesthesia (LOA)

Patient Factors

• Height is inversely proportional to LOA

• CSF volume is inversely proportional to LOA

• Pregnancy or Abdominal tumors:
• ↑↑ intra-abdominal pressure → ↑↑ subarachnoid and epidural venous pressure → ↑ blockade duration.
• Progesterone in pregnancy makes nerves more sensitive → ↑ blockade duration.

Drug Factors

• Volume & level of injection:
• Directly proportional to the level of anaesthesia.

• Baricity of drug:
• Density of the drug compared to CSF.
• Hyperbaric:
• Drug settles down, leading to decreased blockade.
• Hypobaric:
• Drug floats, leading to increased blockade.

Procedure Factors

• Position:
• Related to baricity of the drug.

Drug	Trendelenburg (Head down)	Reverse Trendelenburg (Head up)
Hyperbaric	Higher block	Lower block
Hypobaric	Lower block	Higher block

Side Effects of Spinal Anaesthesia

• SYMPATHETIC BLOCK

• CVS (Cardiovascular System):
• Decreased Heart Rate (HR):
• Rx: Atropine/glycopyrrolate.
• Decreased Blood Pressure (BP):
• Prevention: Preloading IV fluids.
• Rx: Pregnant / Aortic stenosis → Phenylephrine (Drug of choice).
• Rx: Non-pregnant → Ephedrine (Drug of choice)/mephentermine.
• Vasopressor of choice in anesthesia for a patient of aortic stenosis, who develops hypotension during surgery, is:
1. Ephedrine
2. Dopamine
3. Dobutamine
4. Phenylephrine
ANS
1. Phenylephrine

• Respiratory System:
• Low Level Of Anasthesia
• No effect.
• High Level Of Anasthesia:
• Only intercostal muscles paralyzed
• complaint of shortness of breath
• Rx: Oxygen
• No diaphragm paralysis → phrenic N (C3, C4)

• GIT (Gastrointestinal Tract):
• Sphincters relaxed → Reverse peristalsis.

• GUT (Genitourinary Tract):
• Urinary retention (most common):
• Sphincter is relaxed but detrusor is paralysed
• Rx: Foley's catheter.
• Penile enlargement.

Epidural Anaesthesia

• Local anaesthetic into the epidural space.

Technique

• Loss of Resistance (LOR) technique
• To the Tuohy needle, attach syringe with vaccum → Once ligamentum flavum is pierced, sucking of air d/t negative pressure in epidural space

• Epidural catheter set includes:
• Tuohy needle
• 16 - 18 G
• Loss Of Resistance syringe
• Epidural catheters

Advantages

• Increased duration of anaesthesia.

• Used in post-operative analgesia.

• No risk of PDPH (as long as dura is not accidentally punctured).

• Stable hemodynamics.

Disadvantages

• Technically difficult and not suitable for emergencies.

• Inadequate blockade.

• Severe PDPH if accidental dural puncture occurs.

Accidental catheter migration:

• To Subarachnoid Space:
• Total spinal anaesthesia
• Patient becomes unresponsive
• Hypotension
• Careful →
• Total spinal anasthesia → Epidural;
• high spinal anasthesia → spinal anasthesia
• Management: Intubation

• To Blood vessel:
• Local anesthesia toxicity.

Cardiovascular Complications of Central Blockade

• Hypotension (most common)
• inflitration into subarachnoid space → appears within minutes.

• Bradycardia

• Reflex tachycardia

• Respiratory depression

• Vasovagal effect
• immediate, before epidural needle insertion

• Systemic toxicity

Peripheral Nerve Block

• Regional block
1. Central Neuraxial block
• Spinal, Epidural, Caudal
2. Peripheral Neuraxial block
• Peripheral nerve blocks target specific nerves.

Brachial Plexus Block

Eye related anasthesia and N supply

Route	Target Space	Complications
Retrobulbar	Intraconal	More complications
Peribulbar	Extraconal	Fewer complications

• SET CEI

Nasociliary Nerve

• Courses along medial wall of the orbit.

• Branches
• Posterior ethmoidal nerve
• Anterior ethmoidal nerve
• Infratrochlear nerve

Innervation

• Lacrimal sac

• Inner canthus

• Lateral aspect of nose

Anterior Ethmoidal Nerve Block

• Branch of nasociliary nerve.

• Blocks distal external nasal branch.

• Clinical Use
• Provides pain relief during procedures involving:
• Lacrimal sac
• Inner canthus
• Lateral nose
• Infratrochlear Nerve Block Used in
• Dacryocystorhinostomy (DCR)

Infraorbital nerve block :

Sphenopalatine ganglion block :

• Anaesthesia of internal nose.
• Via nose
• Via greater palatine foramen (Medial to 3rd molar)

NOTE:

• Biopsy above VC → anesthetize ILN at thyrohyoid membrane

Local Anesthetics

Special points:

Local Anaesthetic Systemic Toxicity (LAST):

• Characterized by:
• Arrhythmias
• Cardiovascular collapse
• Seizures

• Treatment is:
• CPR
• 20% intralipid (DOC)

Mechanism of Action (MoA)

• Voltage-gated sodium channel blockade.

• Action of local anaesthetics is decreased in infected areas
• low pH (in pus) → ionized form of LA (active form) → poor penetration into cell → no action

Sequence of Blockade

Characteristics

• Onset:
• Quicker onset → small myelinated fibers.
• ↑ by the adding of NaHCO3
• (↑↑ pH → non-ionized form → quick onset of action).

• Absorption:
• Intercostal nerve block:
• Maximum absorption (risk of toxicity).
• Action Increased by (↓ absorption):
• Addition of adrenaline (1:200,000)
• Note: Do not inject in end arteries (causes gangrene).
• Fingers,
• toes, tip of nose,
• ear lobule,
• circumcision surgeries

• Duration:
• Increased by the addition of opioids (morphine, fentanyl).

Max Dose

• Lignocaine:
• 3 - 4.5 mg/kg.

• Bupivacaine & Ropivacaine:
• 2-3 mg/kg.

• Lignocaine + Adrenaline:
• 7 mg/kg.

Toxicity

• Lignocaine:
• Seizures mainly.
• Rx: Midazolam.

• Bupivacaine:
• Ventricular arrhythmias mainly.
• Rx: 20% Intralipid (1.5 ml/kg bolus, 0.25 ml/kg/hr infusion).

• Cocaine:
• ↑↑ BP → angina.
• Rx: Nitroglycerine.

• Prilocaine:
• Methemoglobinemia due to ortho-toluidine.

Applications

• EMLA Cream:
• 2.5% lignocaine + 2.5% prilocaine
• for IV cannulation

• Bier's block:
• IV regional anaesthesia with tourniquet.
• Drugs:
• Approved: Lignocaine 0.5%.
• Contraindicated: Bupivacaine.
• Indication:
• Short procedures
• long procedures cause tourniquet pain
• LA induced CNS toxicity
• Initial: Lightheadedness/Dizziness
• Later: Visual/Auditory
• Last: GTCS
• Rx: Midazolam
• Contraindication:
• Sickle cell anemia.

• Labour Analgesia:
• Bupivacaine 0.125%
• C & Aδ fibers blockade → Pain block
• Bupivacaine 0.25%
• Aβ & Aα fibers blockade → Motor blockade

Anaesthesia Workstation / Boyle’s machine

• Designed by Sir Henry Edmund Gaskin Boyle.

Zones

• Anaesthesia workstations are divided into three pressure zones:
• High pressure
• main: gas cylinders
• Intermediate pressure.
• Low pressure.

Gas Cylinders

• Classification:
• Liquifiable:
• N2O
• Non-liquifiable:
• O2

Identification of Gases in Cylinders

Material Used

• Molybdenum steel alloy.

• Aluminium
• for use in MRI rooms

Measurement

• Non-liquifiable gas:
• Bourdon's pressure gauge.
• Mnemonic: Borderil gas release cheyth

• Liquifiable gas:
• Manually weighing the cylinder.

Safety Features

• Markings:
• Prevents explosions.
• Non-liquifiable cylinders : Service pressure.
• Liquifiable cylinders : Filling ratio/density.

Pin index Safety System (PISS):

• prevent wrong connections of cylinders.

Cylinder	Pin index value
Air	1, 5
O2	2, 5
N2O	3, 5
CO2 7.5%	1, 6
Cyclopropane	3, 6
Entonox	7

• 50:50 mixture of N2O and O2

• Used for labour analgesic

Bodock's Pressure Seal (Gasket):

• Mnemonic: dock to seal leakage

• To prevent gas leakage.

Intermediate Pressure Zone

• 40 - 55 psi.

• Pipeline pressure indicator.

• Diameter index safety system.
• DISS

• O2 flush valve:
• 35 - 75 L O2/min.
• Disadvantage: Barotrauma.

Low Pressure Zone

• 10 - 15 PSI.

• O2 flow meters are always downstream.

• Safety feature:
• Link 25 system
• Cannot shut down O2 completely

• Bobbin → measure the flow of oxygen

 

Breathing Circuits

• Breathing circuits are classified into
1. Mapleson's/Semi-Closed Circuits
2. Closed Circuit/Circle Systems.

Mapleson's/Semi-Closed Circuits

• Advantage: Easy transportation.

• Disadvantage: Heavy fresh gas flow (FGF).

• Examples: Bain's circuit (co-axial circuit).

Types

• The efficiency in spontaneous ventilation (1, 3, 2)
• A > DFE > CB.

• The efficiency in controlled ventilation (3,2,1)
• DFE > BC > A.

• Mapleson A



• AKA Magill's circuit
• FGF = minute ventilation (MV)
• Use: Spontaneous ventilation
• NOTE:
• Adjustable Pressure valve
• Releases gas when exceeding 30 - 40 cm of water
• To prevent barotrauma
• Mnemonic: A → ASS (A → spontaneous) → AP near patient, FGF away

• Mapleson D



• Modification: Bain's circuit.
• most common type
• FGF = 1.6 x MV
• Use: Control ventilation.
• Mnemonic:
• D → F near patient
• D → B → Bains
• D → C → Control

Closed Circuit/Circle Systems

• Exhaled Air contains
• 16% O2
• 5% CO2

• Inhaled air should contain
• 21 % O2
• 0.3 % CO2

• Part of exhaled CO2 is reabsorbed by soda lime to make 0.3%
• Halothane interact least with it

• Gases are recycled.

• Composition of Classic soda lime (in %):
• Ca(OH)2: 80%
• NaOH: 3%
• KOH: 2%
• H2O: 16%

• Disadvantage:
• Bulky (increased chance of disconnection).

Basic Life Support (BLS) Algorithm

• Most frequent Rib fracture during CPR
• 3rd to 5th

• Depths for adults and infants:
• Infants: 
• At least 1/3rd of the AP diameter of the chest,
• approximately 1.5 inches (4 cm).
• Adults: 
• At least 2 inches (5 cm),
• no more than 2.4 inches (6 cm).

Shock Energy for Defibrillation

• Biphasic: 120 - 200 J.

• Monophasic: 360 J.

Drug Therapy (IV/IO dose)

• Epinephrine:
• 1 mg every 3-5 minutes (1:1000).

• Amiodarone:
• First dose: 300 mg bolus.
• Second dose: 150 mg.

• Lidocaine:
• First dose: 1-1.5 mg.

Reversible Causes (5 Hs and 5 Ts)

• 5 Hs:
• Hypovolemia.
• Hypoxia.
• Hydrogen ion (Acidosis).
• Hypo/hyperkalemia.
• Hypothermia.

• 5 Ts:
• Tension pneumothorax.
• Cardiac Tamponade.
• Toxins.
• Thrombosis (Pulmonary).
• Thrombosis (Coronary).

Indications that Resuscitation Was Successful

• ROSC (Return of spontaneous circulation).

• Monitor pulse & blood pressure.

• Abrupt sustained increase in ETCO2 (Typically 40 mmHg).

• Spontaneous BP tracing.

Indications to Stop BLS & ACLS

• Cardiac arrest not witnessed (BLS).

• Bystander CPR not provided (BLS).

• No ROSC after 20 mins of CPR (BLS & ACLS).

• AED unavailable/not delivered (BLS).

Adult Tachycardia with Pulse

Antiarrhythmic Infusion

• Procainamide:
• 20-50 mg/min until arrhythmia is suppressed.
• Maximum dose: 17 mg/kg.
• Maintenance infusion: 1-4 mg/min.
• Avoid if prolonged QT or CHF.

• Amiodarone:
• First dose: 150 mg over 10 mins.
• Repeat if VT recurs.
• Maintenance: Infusion of 1 mg/min for first 6 hrs.

• Sotalol:
• 100 mg (1.5 mg/kg) over 5 minutes.
• Avoid if prolonged QT.

• Adenosine:
• First dose: 6 mg rapid IV push then NS flush (peripheral line).
• Second dose: 12 mg.

• Note: Synchronised cardioversion, shock is synced with "R" wave.

Adult Bradycardia

• This algorithm details the management of adult bradycardia (HR < 60 bpm) or bradyarrhythmia (HR < 50 bpm).

Management

• Hemodynamically stable:
• Monitor & observe.

• Hemodynamically unstable:
• Atropine IV 1 mg bolus.
• Repeat every 3-5 mins.
• Maximum dose: 3 mg.
• If not effective, consider
• transcutaneous pacing
• Dopamine infusion
• Epinephrine infusion.