Anesthesia in Ophthalmic Surgery

Overview & Pre-op - Setting Eye Stage

• Anesthesia Goals: Akinesia, analgesia, stable intraocular pressure (IOP), patient & surgeon comfort, minimize oculo-cardiac reflex (OCR).
• Pre-operative Evaluation:
  • Thorough history: Systemic diseases (DM, HTN, asthma, bleeding disorders), medications (anticoagulants!), allergies, prior anesthesia experience.
  • Ocular exam: Visual acuity, IOP, axial length (AL).
  • Systemic exam: Airway, cardiovascular, respiratory.
  • Investigations: Guided by ASA status & co-morbidities (ECG, blood sugar, coagulation profile if needed).
• Patient Preparation:
  • Informed consent: Discuss technique, risks (e.g., retrobulbar hemorrhage, globe perforation), benefits.
  • Fasting: NPO ~6 hrs for solids, ~2 hrs for clear fluids.
  • Premedication: Anxiolytics (e.g., Diazepam 5-10 mg oral / Midazolam 1-2 mg IV), antiemetics if high risk.

  ⭐ For patients on anticoagulants/antiplatelets (e.g., Warfarin, Aspirin, Clopidogrel), individualized decision on stopping/bridging (typically 5-7 days prior for Aspirin) balancing thrombotic vs. bleeding risk is crucial.

Local Anesthesia Types - Eye Block Party

• Topical: Proparacaine 0.5%, Tetracaine 0.5-1%. For minor procedures. Rapid onset, short duration.

• Infiltrative:

  • Subconjunctival: Chalazion, pterygium.
  • Sub-Tenon's (Episcleral): Cannula for posterior block. Good akinesia, safer.

• Regional Needle Blocks:

  • Retrobulbar (Intraconal):
    • Targets ciliary ganglion, CN II, III, VI. Volume: 3-5 mL.
    • Rapid, dense block. Risks: Globe perforation, RBH, optic nerve injury.
  • Peribulbar (Extraconal):
    • Larger volume: 6-12 mL. Safer than retrobulbar.
    • Slower onset, more chemosis.
  • Facial Nerve Blocks: Van Lint (periorbital), O'Brien (truncal). For eyelid akinesia.

⭐ Hyaluronidase (5-7 IU/mL) added to LA enhances spread & onset.

Anesthetic Agents & Mixes - Potion Power-Ups

• Local Anesthetics (LAs):
  • Amides (Low allergy risk):
    • Lignocaine (Xylocaine): Rapid onset, 1-2 hr duration. Max: 4.5 mg/kg (plain), 7 mg/kg (w/ adrenaline).
    • Bupivacaine (Sensorcaine): Slow onset, 4-8 hr duration. Highly cardiotoxic. Max: 2 mg/kg.
    • Ropivacaine: Similar to bupivacaine, less cardiotoxic.
  • Esters (e.g., Procaine): Higher allergy risk (PABA metabolite).
• Adjuvants:
  • Adrenaline: Vasoconstrictor. ↑duration, ↓toxicity, ↓bleeding. Conc: 1:100,000-1:200,000.
  • Hyaluronidase: Spreading factor. ↑diffusion. Dose: 5-15 IU/mL.
  • Sodium Bicarbonate: Alkalinization. Speeds LA onset by ↑non-ionized form.
• Common Mix (Retrobulbar): Lignocaine + Bupivacaine + Hyaluronidase ± Adrenaline.

⭐ Bupivacaine is highly cardiotoxic; lipid emulsion is the antidote for LA systemic toxicity (LAST).

GA & Complications - Risky Eye Business

• General Anesthesia (GA) Indications: Pediatrics, long surgery (>2 hrs), patient refusal local, open globe, uncooperative.
  • Agents: Propofol, Sevoflurane (all ↓IOP). Avoid Ketamine (↑IOP). LMA preferred over ETT (↓coughing, ↓IOP).
• Complications (Local & GA):
  • Oculocardiac Reflex (OCR): 📌 "Five (V) & Dime (X)" (Trigemino-vagal). Bradycardia from EOM traction. Mgmt: Stop stimulus, Atropine 0.01-0.02 mg/kg IV.

- **Retrobulbar Hemorrhage (RBH):** Proptosis, ↑IOP, diplopia. Mgmt: Lateral canthotomy & cantholysis (immediate).
    ![Complications of Anesthesia in Ophthalmic Surgery](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Ophthalmology_Ophthalmic_Surgery_Anesthesia_in_Ophthalmic_Surgery/e7394e1e-e2d8-4239-b625-2e2e90adbaf6.jpg)
- Globe Perforation: Pain, ↓vision, hypotony. Risk ↑ high myopia (long axial length).
- Brainstem Anesthesia (Retrobulbar): Apnea, LOC, seizures. Mgmt: Airway support.
- Malignant Hyperthermia (GA: Succinylcholine/inhalational agents).
- PONV common.

⭐ Oculocardiac reflex is most common with medial rectus muscle traction during strabismus surgery.

High‑Yield Points - ⚡ Biggest Takeaways

• Retrobulbar block (RBB): Most common, akinesia, anesthesia. Risks: hemorrhage, perforation.
• Peribulbar block: Safer than RBB, larger volume, slower onset. Lower perforation risk.
• Sub-Tenon's block: For glaucoma surgery, minimal IOP rise, limited akinesia.
• Topical anesthesia: For anterior segment surgery (phaco). Proparacaine, lignocaine.
• General anesthesia (GA): For children, uncooperative adults, long surgeries, open globe injuries.
• Oculocardiac reflex (OCR): EOM traction → bradycardia. Manage with atropine.
• Hyaluronidase: Added to LA to enhance spread, ↓ orbital pressure.