anaesthetic techniques

SUBMITTED TO:-Dr. P.B.PatelProfessor & HeadDept. of Veterinary Surgery & RadiologyCollege of veterinary science & A. H.S. K. Nagar SUBMITTED BY:-

Dr. Hitendra B. PrajapatiM. V. Sc ScholarDept. of Veterinary Surgery & RadiologyDr.V.M.Jhala Clinical Complex,DeesaSDAU-Dantiwada

Anaesthetic Techniques, Equipments &

Artificial Respiration

INTRODUCTION:-

• Anaesthesia is used to denote loss of sensetion to any part or whole of the body, produced by agents which depress the activity of nervous tissue either locally or centrally.

• It is revesible process.

Types of anaesthetic techniques:-

A. General anaesthesia:-

1.injectable anaesthesia

2.inhalation anaesthesia

B. Local anaesthesia:-

1.Topical anaesthesia

2.field block

3.regional nerve block

C. Other:-

1.electronarcosis

2.Acupuncture

3.Hypothermia

General Anaesthesia:-

• It is a state of unconsciousness produced by a process of controlled, reversible, intoxication of the central nervous system in which there is a lowered sensibility to stimuli from the environment and a diminished motor response to such stimuli.

• Intravenous anaesthesia in veterinary practice is primarily used for the induction of anaesthesia which is subsequently maintained by ihalation anaesthesia in small animals.

Intravenous Anaesthesia:-

e.g. 1.barbiturates:-

phenobarbital (20-30 mg/kg b.wt.),

pentobarbitone(6-8mg/kg b.wt.),

thopental,

methohexitone etc.

2.non barbiturates:-

chloral hydrate,

propofol(4-6mg/kg b.wt.)

3.dissiciative anaesthetics:-

ketamine(10mg/kg b.wt.),

tiletamine(6.6-13.2mg/ke b.wt.)

Inhalation anaesthesia:-

• Method of administration:-

1. Open insufflation

2. Semi open systems without nonbreathing valves

3. Semi open system with nonbreathing valves

4. Semi closed and closed systems

Inhalant anaesthetics

*Volatile or gaseous

e.g. ether

methoxiflurane

halothane

isoflurane

sevoflurane

desflurane

nitrous oxide

Inhalation anaesthetic method,open method

Jar/Box

Use of Cone/Mask

Cotton/Open drop

Non Rebreathing system

To & Fro System

Local anaesthesia:-

• Anaesthetic sloution is applied topically in the form of gel, solution or aerosol on the eye and mucous membrane of penis, vagina, rectum, urethra etc.(Topical) or injected locally in surgical site(Field Block).

• Besides, anaesthetics are injected around a large nerve trunk(Regional nerve block) or in the epidural or subarachnoid space(Epidural) Or in distal to the site of a tourniquet intravenously(Regional intravenous).

Common methods of producing local anesthesia

• Surface (topical) anesthesia • Intrasynovial anesthesia • Infiltration anesthesia • Spinal anesthesia • Intravenous regional local anesthesia • Regional anesthesia

Surface (topical) anesthesia:-

• This refers to the use of local anesthetics in solution sprays as well as in various creams and ointments, on mucous membranes; drops into the eye; sprays or brush in laryngeal area, infuse into the nostrils, urethra, or rectum.

Intrasynovial anesthesia:-

• In joints, bursa, and tendon sheaths. • Useful for both diagnosis of lameness, and for

general pain relief. • The local anesthetic chosen must cause

minimal irritation, and great care in sterility is necessary as infection in these sites occurs easily

Infiltration anesthesia:-

• By this method the nerve endings are affected at the actual site of operation.

• Most minor surgery can be done this way, excluding surgery on teats in cattle or small animal digits.

• Never inject local analgesic through infected tissues• where this is used is on the teats of cattle (do not

use epinephrine here, as vasoconstriction could lead to ischemic necrosis and sloughing of tissue) or around the limb of cattle.

Spinal anesthesia:-

• Spinal anesthesia is the injection of local anesthetic around the spinal cord.

• Spinal anesthesia is divided into two types; ‘epidural’ and ‘true spinal’. – Epidural (or extradural) anesthesia refers to

depositing of local anesthetics into the extradural space. The needle enters the spinal canal, but does not penetrate the meninges.

– True spinal anesthesia refers to the subarachnoid access (usually known as ‘spinal’ anesthesia) in which the needle penetrates the dura mater.

Intravenous regional local anesthesia (Bier’s block):-

• In this technique, a limb vein is catheterized

• Apply tourniquet placed around the limb, at a pressure adequate to prevent arterial circulation (> 150 mmHg).

• Local anesthetic (preferably without epinephrine) is then injected into the vein.

• After a period of 15 minutes the area distal to the tourniquet is anesthetized until the tourniquet is removed.

Caudal epidural

NERVE BLOCKS

Auriculopalpebral Nerve Block

Retrobulbar nerve block

Maxillary nerve block

Mandibulo-alveolar nerve block

Infra-Orbital nerve block

Mental nerve block

Paravertebral Nerve blocks:-

• It refers to the perineural injection of local anesthesia about the spinal nerves as they emerge from the vertebral canal through the intervertebral foraminae.

• Its advantage is that it provides analgesia and muscle relaxation of the whole area covered by the segmental nerves blocked. T-13, L-1, L-2

Auriculopalpebral Nerve Block:-

• This block can be used to prevent the eyelids moving during clinical examination or surgery.

• It blocks the orbicularis oculi muscle.

• The nerve course runs from the base of the ear past the eye ventrally along the facial crest.

• Purpose:– Prevent eyelid closure during examination of the

eyeball.

• Injection site:– The needle is inserted in front of the base of the

ear at the base of the ear at the end of the zygomatic arch and is introduced until its point lies at the dorsal border of the arch.

• Caution:– This block does not produce analgesia of the eye

or the lids.– In conjunction with topic analgesia (2% lidocaine)

it is useful for the removal of foreign bodies form the cornea and conjunctival sac.

Cornual Nerve Block:-

• This block is used for dehorning.

• The nerve can be found at the orbit running behind the lateral ridge of the frontal bone.

• The nerve supplies the horn coruim and the skin around the base of the horn.

Mandibulo-Alveolar Nerve Block:-

• It is used to desensitize the lower jaw alongwith its teeth and lower lip.

Indication:• Management of surgical condition of molar

teeth and incisors and the body of the mandible,suturing of wound of the teeth.

Mental Nerve Block:-

• To desensitize the dental nerves of the lower jaw in the mandibular canal and at the mental foramen.

Indication:-• Suturing of wound of lower lip, wiring

operations around the lower teeth and the body of the mandible.

Infra-Orbital Nerve Block:-

• To desensitize the whole anterior half of the face including the cheek teeth as far as the second molar, nostril,upper lip, gum and incisors.

Indication:-• Surgical management of conditions of upper

lip and nostril.

Maxillary Nerve Block:-

• For surgical management of the conditions of the upper lip, nose and upper jaw

• The maxillary nerve is blocked in the pterygopalatine fossa before it enter the infra orbital canal.

Retrobulbar Nerve Block:-

• For the surgical management of conditions of eyeball and membrana nictitans

• The needle is inserted through the lateral canthus of the eye

Brachial plexus block

Carpal Block

Other Routes:-

• Electronarcosis:-anaesthesia is achieved by passing an electric current through theccerebrum to induce deep nacosis although the method is rarely used in veterinary practice.

• Acupuncture:-an ancient Chinese system that involves insertion of specially designed needles at specific points and their stimulation by various means to produce analgesia.

• Hypothermia:-the procedure involves decreasing the body temperature either locally or generally to minimize the anaesthetic doses.

Anaesthetic instruments &

Artificial Respiration

Endotracheal Tubes (ET Tubes)

Flexible tube placed in the trachea Delivers anesthetic gases directly from the

anesthetic machine to the lungs Advantages

Open airway Less anatomical dead space Precision administration of anesthetic agent Prevents pulmonary aspiration Responds to respiratory emergencies Monitors respirations

Types of Endotracheal Tubes

Murphy tubes (A, C,D) Beveled end and side holes Possible cuff• A. silicone• C. PVC• D. Red rubber

Cole tubes (B) No side hole or cuff Abrupt decrease in diameter of the tube Used in birds and reptiles

Parts of the Endotracheal Tube

Patient end (i) Machine end (c ) Connector ( D) Cuff ( H) Pilot balloon (b)

and valve (a) Murphy Eye- J Internal diameter

measurement

Laryngoscope Used to increase the visibility of the larynx while

placing an ET tube Parts

Handle containing batteries Blade to depress tongue and epiglottis Light source to illuminate the throat

Sizes Small animal 0 to 5; large animal up to 18-inch blade

Types Miller blades A, C, E McIntosh blades B, D, F

Masks Cone-shaped devices used to administer oxygen

and anesthetic gases to nonintubated patients Used for induction and maintenance of anesthesia

in very small animals Plastic or rubber Variety of diameters and lengths Rubber gasket

Anesthetic Chambers Clear, aquarium-like boxes used to induce general

anesthesia Used in feral, vicious, or intractable animals to

reduce stress Acrylic or Perspex Removable top with two ports Cannot monitor patient closely

Anesthetic Machines

Used to deliver precise amounts of oxygen and volatile anesthetic under controlled conditions

Principles of Operation of Anesthetic Machines

Carrier gas: oxygen or nitrous oxide

Liquid inhalant anesthetic: to be vaporized

Mixed gases delivered to patient

Exhaled gases removed from patient: scavenging system or recirculated

Components of the Anesthetic Machine

Compressed gas supply

Anesthetic vaporizer (precision or nonprecision; VOC or VIC)

Breathing circuit (rebreathing or nonrebreathing)

Scavenging system

Components of the Anesthetic Machine (Cont’d)

Compressed Gas Supply Oxygen

Used to increase inspired air to at least 30% oxygen

Level necessary to maintain cellular metabolism under anesthesia

Used to carry vaporized anesthetic to patient

Cylinders (tanks) Contain large volume of gas under high

pressure E tanks (small), attached directly to

anesthetic machine H tanks (large), attached remotely to

anesthetic machine

Compressed Gas Supply (Cont’d)

Control valve (outlet port) Located on top of the tank Left loose (open), right tight (closed)

Pressure-reducing valve (B) Reduces outgoing pressure to a usable level

Tank pressure gauge C Line pressure gauge D

Rebreathing System Circle systems

Used on all but very small animals

Carbon dioxide removed from exhaled air

Exhaled air is inhaled again with added oxygen and anesthetic

Rebreathing System (Cont’d) Air flow:

Inhalation unidirectional valve → Inhalation tube → Animal → Exhalation tube → Exhalation unidirectional valve → Carbon dioxide absorber canister → past reservoir bag → Pop-off valve → Pressure manometer → Inhalation unidirectional valve

Rebreathing System (Cont’d) Closed rebreathing system

Total system Pop-off valve is nearly or completely closed and

oxygen flow is low Used mostly in large animal anesthesia

Semiclosed rebreathing system Partial system Pop-off valve is open and oxygen flow is high Excess air is released into scavenging system Most common configuration

Breathing Systems

Breathing Tubes and Y-Piece

Breathing tubes Corrugated breathing tubes or inspiratory and

expiratory breathing tubes Carry anesthetic gases to and from the patient Connected to unidirectional valve and Y-

piece Three sizes: 50 mm, 22 mm, and 15 mm in

diameter

Y-piece Connects breathing tubes Connects to mask or endotracheal tube

Non-rebreathing Systems Semiopen system

Used in very small patients (<2.5 kg) Little exhaled gas is returned to the patient Exhaled gas is evacuated by the scavenging system Fresh gas is routed to the patient directly from the

vaporizer No carbon dioxide absorber canister, pressure

manometer, or unidirectional valves Several configurations are available

Components: Endotracheal tube connector, fresh gas inlet, reservoir bag, overflow valve, scavenger tube, and scavenger system

Thank You !