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Thread: ANESTHETICS in Ophthalmic practice

  1. #1
    Join Date
    Oct 2017
    Riyadh, Saudi Arabia
    (Consultant Ophthalmologist at MALAZ MEDICAL GROUP)


    Default ANESTHETICS in Ophthalmic practice

    ❤️ANESTHETICS in Ophthalmic practice 

    ✍️ reversible blockage of nerve fiber conduction (block sodium channels)

    ✍️ pH dependent (less effective at low pH like inflamed tissue)

    Classes ( esters and amides)

    ✍️ Ester

     hydrolyzed by plasma cholinesterase
     metabolized in liver

     cocaine
     tetracaine (amethocaine)
     proparacaine
     procaine
     benoxinate

    ✍️ Amide

     longer duration and less systemic toxicity
     metabolized in liver



    Routes of administration

    ✍️ topical
     disturb intercellular junction of corneal epithelium (increase permeability)


     Proparacaine (Ophthaine)
    • 10- to 30-minute duration
    • cause allergic dermatitis

    Tetracaine (Pontocaine)
    •similar to proparacaine but longer duration
    • more toxic to corneal epithelium

     Benoxinate
    • similar to proparacaine
    • can be combined with fluorescein (Fluress) for tonometry

     Cocaine
    • greatest epithelial toxicity
    • excellent anesthesia
    • sympathomimetic effect (test for Horner’s syndrome)

    ✍️ Parenteral( injectables)

     may be used with epinephrine (1:100,000) to increase duration by preventing systemic absorption and decreases bleeding

    hyaluronidase (Wydase) 150 IU increases tissue penetration, but decreases duration.

    Side effect of retrobulbar anesthesia 1⁄4 respiratory depression, bradycardia

     Toxicity: hypotension, convulsions, nausea, vomiting

     examples

     Lidocaine (Xylocaine)
    • 1 hour duration (2 hours with epinephrine)
    • used for local anesthesia and akinesia

     Procaine (Novocain)
    • 30 to 45 minute duration

     Mepivacaine (Carbocaine)
    • 2 hours duration

     Bupivacaine (Marcaine)
    • 6 hours duration

    ✍️ General:

     all agents decrease intraocular pressure (IOP)except ketamine, chloral hydrate, N2O, and ether

     Malignant hyperthermia (Major complication)

    ✍️ rare

    ✍️ autosomal dominant

    ✍️ occurs after exposure to inhalation agents (most commonly halothane, also succinylcholine, haloperidol

    ✍️more common in children and males

    ✍️ due to calcium-binding disorder with increased intracellular calcium, which stimulates muscle contraction and interference with oxidative phosphorylation causes hypermetabolic crisis

    ✍️ Most have defect in ryanidine receptor (RYR-1 gene on chromosome 19q13.1)

    ANESTHETICS Ophthalmic practice attachment.php?attachmentid=3469&d=1513499262

    ✍️ Clinical picture

    tachycardia (first sign)
    elevated CO2 levels
    unstable BP
    muscle rigidity (trismus from masseter rigidity)
    increased temperature (later sign)
    heart failure
    disseminated intravascular coagulation

    ✍️ laboratory tests

     respiratory and metabolic acidosis
    increased K, Mg, myoglobin, creatine phosphokinase
    hypoxemia, hypercarbia
     myoglobinuria


     stop anesthesia
     hyperventilate with 100% oxygen
     give sodium bicarbonate
     cool patient (iced saline intravenous (IV) and
     lavage
    surface cooling
     mannitol and furosemide (Lasix)
     IV dantrolene (prevents release of calcium from sarcoplasmic reticulum)
     procainamide and insulin (do not use lactated Ringer’s solution, which increases potassium)

    ✍️ PROGNOSIS: < 5% mortality

    Attached Images  
    Last edited by Reda Gomah El Garia; 12-17-2017 at 08:30 AM.

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