Wednesday, September 28, 2005

Chapter 3 - Anesthesia

Table: Comparison of the different modalities of anesthesia

[CLICK ON TABLE FOR LARGER IMAGE]

Coating the cornea with OVD protects the epithelium [view video].

The Retrobulbar Block [view video] provides effective anesthesia and akinesia for cataract surgery.

The Advantages of Retrobulbar Anesthesia:


  1. Great for long cases (>45 minutes)

  2. Great for inexperienced surgeon (get akinesia, proptosis)

  3. Helps to increase exposure

  4. Nystagmus (can be used for Yag laser with nystagmus also)

The Disadvantages of Retrobulbar Anesthesia:


  1. Blood thinners increase risk of retrobulbar hemorrhage (several studies -- bleeding risk low for ASA & coumadin)

  2. Monocular (RB injection often forces admission until patch removed)

  3. Long axial eye length increases risk of globe perforation

  4. May be risky with the presence of scleral buckle

Steps to perform a Retrobulbar Block [view video]:


  1. Place 1 drop (gtt) of topical anesthetic into both eyes

  2. Clean lower lid with alcohol wipe

  3. Fill 5cc syringe with mixture of 1% lidocaine/0.375% bupivacaine and Wydase (HYALURONIDASE) without epinephrine

  4. Place blunt 23 gauge needle (1.5 inch flat grind) on syringe

  5. Start at the junction of the lateral 1/3; 2/3 junction of the lower lid

  6. Use the index finger of non-dominant had to create space between floor and globe

  7. Aim perpendicular to lid until passing through the septum (1st pop)

  8. Then redirect more superior advancing about 1 - 1½ inches (2nd pop) into muscle cone

  9. First pull syringe back to ensure you are not in a blood vessel

  10. Inject 4 cc slowly into retrobulbar space

  11. Retract needle until just under skin (in orbicularis muscle) and inject remaining 1 cc

  12. Have patient look straight ahead during procedure

  13. Apply pressure on closed eye for a minute or so – be alert for retro bulbar hemorrhage

Subtenon’s Anesthesia [view video] will provide additional anesthesia during a topical case if needed.

The Advantages of subtenon’s anesthesia:
  1. Great when Topical case getting complicated (e.g., Convert to ECCE, anterior vitrectomy)

  2. Great for patients on blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of subtenon’s anesthesia:
  1. Conjunctiva gets red and sore

  2. Conjunctival chemosis can be a problem

Steps to perform a subtenon’s block [view video]:
  1. Give topical anesthesia (probably already done if converting from topical case)

  2. Prepare 3cc syringe with 1% lidocaine / 0.375% bupivacaine

  3. Place lacrimal canula with gentle curve to approximate that of the globe

  4. Pick a quadrant for the block (best to go for a lateral quadrant to avoid oblique muscle)

  5. Have the patient look away from the chosen quadrant to increase exposure

  6. Use 0.12 forceps to retract conjuctiva

  7. Make small incision down to sclera with wescott scissors

  8. Redirect wescott scissors with curve down and bluntly dissect through quadrant

  9. Dissect past the equator (similar to using stevens tenotomy scissors in peds/retina)

  10. Use 0.12 Forceps for counter traction

  11. Place canula through incision and direct past the equator before injecting

  12. The mixture should flow easily and cause minimal chemosis

  13. If not redissect with the wescots and get more posterior

The Advantages of Topical Anesthesia:
  1. Experienced fast surgeon

  2. Monocular patients get fast rehabilitation

  3. On blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of Topical Anesthesia:
  1. Greenhorn surgeons need akinesis

  2. Cannot use in patients with nystagmus

The Steps for Topical Anesthesia:
  1. Intracameral 1% nonpreserved lidocaine can supplement topical

  2. Many studies have shown no benefit

  3. If the case is long or if iris is moving it seems to help in my hands

  4. Usually placed just after paracentesis is formed

  5. Use about 0.5 cc

  6. May sting a bit so I usually warn the patient: “I'm giving you the rest of the numbing medicine and you may feel it for a second or two and then it will be very easy for you.”

Table: Comparison of the different types of anesthetics

[CLICK ON TABLE FOR LARGER IMAGE]


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