ANAESTHESIA

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(No Transcript)
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ANAESTHESIA

• Anaesthesia means the absence of sensation.
• Anesthesia works in 4 ways
• As an analgesic (pain reliever)
• It promotes unconsciousness
• It causes immobility of the patient
• Elimination (or reduction) of autonomic responses
  such as tachycardia (increased heart beat),
  increased hypertension

Ref http//www.oyston.com/anaes/local.htm http//
www.facialplasticsurgery.net/anaesthesia.htm
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ANAESTHESIA TYPES

• General Anaesthesia
• Application of an anesthetic drug given by
  inhaled gas or by a liquid in IV form to the
  entire body and brain
• Local/Regional /Topical Anaesthesia
• Application of local anaesthetic (Freezing) to
  a specific area of the body

Ref http//www.healthAtoZ.com/-
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LOCAL/TOPICAL ANAESTHESIA

• Local or topical anaesthesia is currently
  performed for many ophthalmic procedures as it is
  associated with reduced morbidity and mortality
  when compared with general anaesthesia.

Ref http//www.nda.ox.ac.uk/
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LOCAL ANAESTHESIAMODES OF ADMINISTRATION

• INJECTIONS
• Needle perforation of the peri-orbital skin or
  conjunctiva
• Injecting local anaesthetic into the peri-orbital
  or orbital tissues.
• Disadvantages
• Chemosis
• Subconjunctival haemorrhage
• Sight or life threatening complications
• TOPICAL
• Local anaesthetic eye drops are applied to the
  surface of the eye

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TOPICAL OPHTHALMIC ANAESTHESIA DEFINITION

• Application of a local anaesthetic drug to a
  mucous membrane. such as the conjunctiva or the
  cornea

Ref Surveys of Ophthalmology Vol. 12, No.5
263-283
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TOPICAL ANAESTHESIA ADVANTAGES

• Avoidance of any needle-related complications
• Lack of need for an eye pad post-operatively
• Wears off rapidly
• More rapid recovery of sight
• Improved patient satisfaction

Ref 1) Chapter 5 Anaesthesia for ophthalmic
surgery. 7th Edition 847-859
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TOPICAL ANAESTHESIA ADVANTAGES

• Rapid onset of action
• Higher safety level,
• Increased analgesia consistency during surgery
• Lower rise in IOP
• Easy to administer
• The limited level of drugs employed inhibits the
  general side effects commonly observed with local
  anaesthesia.
• The return of sensitivity soon after surgery
  allows immediate detection of any unexpected
  ocular pain that might suggest complications.
• No systemic toxicity
• No tissue irritation
• No inhibition of healing process

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TOPICAL ANAESTHETICS STRUCTURAL CLASSIFICATION

• Oldest and largest group has an ester link
• Eg. Proparacaine, Tetracaine, Procaine,
  Chloroprocaine

• Newer group has an amide link
• Eg Lidocaine, Bupivacaine

Ref Chapter Physiology and pharmacology of
local anaesthetic agents Smith et al-35-59.
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TOPICAL OCULAR ANAESTHETIC AGENTS
Ref Business Briefing European Pharmacotherapy
2004 36-38
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TOPICAL ANAESTHETICS MECHANISM OF ACTION

• When applied to the nerve, local anaesthetics
  cause a temporary, reversible change in the
  chemical make up of the neuronal membrane.
• Causes reversible interruption of transmission of
  electrical impulse through the nerve thereby
  leading to anaesthesia.

Ref Update in Anaesthesia 1994 Issue 4
Article 7 Pages 1-7.
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TOPICAL ANAESTHESIA APPLICATIONS

• Application of surgical scrubs Povidone 2.5-10
• Conjunctiva
• Excision of superficial lesions such as cysts or
  naevi
• Cornea
• Removal of foreign bodies
• Removal of sutures
• Debridement of the corneal epithelium after
  recurrent erosions/herpetic keratitis
• Corneal scrapings/biopsy with infective keratitis
• Dissolution of Ca2 salts in band keratopathy

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TOPICAL ANAESTHESIA APPLICATIONS (contd.)

• Removal of pterygium/conjunctival autografts
• Intraocular
• Cataract Surgery
• Lid surgery

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WHY TOPICAL ANAESTHESIA FOR CATARACT SURGERY IS
PREFERRED

• Topical anesthesia is preferred over a regional
  block for cataract surgery because it is safer,
  more comfortable and it causes less anxiety.
• In addition, vision clears more quickly, and
  there is no risk of retrobulbar hemorrhage and
  perforation.

• Business Briefing European Pharmacotherapy 2004
  36-38
• http//www.ascrs.org/publications/jcrs/archives/cs
  nov6.html

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PROPARACAINE INTRODUCTION

• Proparacaine is an ester type of specific surface
  acting local anaesthetic.

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PROPARACAINE MECHANISM OF ACTION

• After topical application to the eye,
  proparacaine penetrates to sensory nerve endings
  in the corneal tissue.
• It blocks both the initiation and conduction of
  nerve impulses therby causing anaesthesia

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PROPARACAINE CLINICAL EFFICACY

• Improves visual acuity in patients with eye pain
  resulting from corneal injury or infection

Ref Annals of Emerg Med 1997 29 158-160
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PROPARACAINE CLINICAL EFFICACY

• Flap suturing with interface proparacaine
  application represents an important therapeutic
  option for the management of recurrent epithelial
  in growth following LASIK.
• Local anaesthesia with proparacaine is adequate
  in ensuring patient comfort during small incision
  clear corneal self sealing phacoemulsification in
  cataract surgery

• J. Cataract and Refractive Surgery 2005 31 916
• J. Cataract and Refractive Surgery 2002 28
  1977-1981

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PROPARACAINE EYE DROPS INDICATIONS

• Proparacaine ophthalmic solution is indicated
• for procedures in which topical ophthalmic
• anaesthetic is indicated
• Corneal anaesthesia of short duration e.g
  Tonometry, Gonioscopy,
• Removal of corneal foreign bodies and for short
  corneal and conjunctival procedures.

Ref PDR 2005
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PROPARACAINE EYE DROPSDOSAGE AND ADMINISTRATION

• Removal of foreign bodies and sutures and for
  Tonometry
• 1-2 drops (in single instillations) in each eye
  before operating.
• Short corneal and conjunctival procedures
• 1 drop in each eye every 5-10 minutes after 5-7
  doses.
• Children
• Safety and effectiveness in children has not been
  established. However, proparacaine has been used
  as a topical anaesthetic in children.

Ref PDR 2005
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PROPARACAINE CONTRAINDICATIONS

• Proparacaine ophthalmic solution should be
  considered contraindicated in patients with known
  hypersensitivity to any of the ingredients of the
  preparation.

Ref PDR 2005 244-245
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PROPARACAINE SPECIAL POPULATION

• Pregnancy Administered only if clearly needed.
• Nursing mothers Caution should be exercised.
• Paediatrics Safety not established, however it
  is being used as a local anaesthetic in children

Ref 1. PDR 2005 244 - 245
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PROPARACAINE EYE DROPS STORAGE

• Store bottles under refrigeration at 20C to 80C.
• Proparacaine needs to be refrigerated to retard
  discoloration of the solution which may further
  result in decrease in drug effect.

Ref PDR 2005244-245
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PROPARACAINE EYE DROPS HIGHLIGHTS

• Proparacaine eye drops provides complete
  analgesia during surgery, wears off rapidly
  following surgery and does not interfere with the
  patients ability to blink, see or move the eye

Ref J Cataract and Refractive Surgery 1993
19(3) 290-292
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PROPARACAINE HIGHLIGHTS

• Proparacaine 0.5 is the only topical anaesthetic
  approved
• for ocular administration by U.S. FDA
• Rapid onset of action
• Relatively short duration
• No Mydriasis
• No IOP change
• Minimal pain on instillation
• No cross allergy with tetracaine
• Solution remains sterile for a long period of
  time
• Repeated applications can be used during
  intraocular surgery/operations
• Fewer allergic reactions as compared to other
  topical ocular anaesthetics

Physiology and Pharmacology of local anaesthetic
agents Smith et al 35-59
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