Peripheral Blocks 4 Eye Blocks and Airway Blocks

1. Peripheral Blocks 4Eye Blocks and Airway Blocks Vincent Conte, MD Clinical Assistant Professor FIU College of Nursing Nurse Anesthesia Program

2. Peripheral Blocks 4 • The presentation will be divided into three sections: • Eye Blocks • Airway Blocks • Subcutaneous and Field Blocks

3. Eye Blocks • The Eye Blocks are divided into: • Topical Anesthesia • Peribulbar Block • Retrobulbar Block

4. Eye Blocks • Regional anesthesia for eye surgery has traditionally consisted of a Retrobulbar Block or Peribulbar Block and IV sedation • Recent advances in topical anesthetics have eliminated the use of both Retrobulbar and Peribulbar blocks in many Opthalmologists practices but there are still some “Old Timers” who use them extensively

5. Eye Blocks • Opthalmologic surgery has changed dramatically in recent years • The most common method for removal of cataracts is now through a small self-sealing incision and phacoemulsification • It is no longer essential to ensure complete muscle paralysis, consequently topical anesthetic techniques have become much more popular and widespread

6. Eye Blocks • Regional innervation for the eye, orbit and periorbital structures are supplied primarily by the first division of the trigeminal nerve and its terminal branches • The intraorbital branches and the terminal branches are blocked by both retrobulbar and peribulbar blocks

7. Topical Anesthesia • Minor surgery to the cornea, sclera and conjunctiva can be carried out under topical anesthesia alone • These procedures may include intra-ocular pressure measurements, removal of foreign bodies, excision of pterygium, irrigation of lacrimal ducts, and removal of sutures • Correction of myopia surgery is also done under topical anesthetics

8. Topical Anesthesia • The most commonly used topical anesthetic for corneal surgery and cataract surgery is 0.4% oxybuprocaine drops (duration of action 30-45 min.) • This is usually supplemented by small doses of Lidocaine 4% or Bupivicaine 0.75% drops (duration of action 45 minutes)

9. Topical Anesthesia • Also used in some “cocktails” is Tetracaine 0.5% or Amethocaine 1% but their duration of action is only about 20 min. so the surgery must be pretty quick • Each ophthalmologist usually has his/her own cocktail of locals to use • They are usually applied several times at least 15 minutes prior to any blocks that are being performed or prior to surgery

10. Topical Anesthesia • It is also not uncommon that during the surgery, sensation may begin to return so the anesthetic may need to be reapplied • Usually, the bottles of local will follow the patients into the OR to be used as needed • Also, a little Versed and Fentanyl can be used to help supplement a patchy block from your end • It may be well appreciated by your surgeon

11. Topical Anesthesia • The most common protocol used at Baptist was as follows: • A HEP LOCK was placed • The first round of LA’s were applied to the eye (topical drops) • PO Versed was given based on weight (usually between 2-4mg) • A 2nd and 3rd round of LA’s would then be applied and the patient would be sent back to the OR for surgery

12. Topical Anesthesia • Once in the OR, depending on their mental state, Versed 1-2 mg was given with a 5cc LR Flush AFTER all monitors were applied • Oxygen was usually applied by NC at 2-3L/min and the hose was wound BELOW the ear first and then around the top and pulled down towards the chin and cinched under the chin for a snug fit

13. Topical Anesthesia • Once all the prep was done, more drops of LA’s were applied and the cornea was tested for sensation and if sufficient, surgery was begun • Only about 10-15% of cataracts were done by blocks, the rest were done by the above method of Topical anesthesia, usually with a HEP LOCK and about 20-25% having a regular IV

14. Retrobulbar Block • The aim of this technique is to block the branches of the oculomotor nerve BEFORE they enter the four rectus muscles in the posterior intraconal space • The patient is asked to place their eyes in a supranasal gaze, and an object (gauze pads, fingers, etc.) are held up as a focal point to keep the eyes from deviating from that position

15. Retrobulbar Block • The patient is then asked to stare at the target object and reinforced to look at it throughout the block • This positions the optic nerve directly behind the globe and toward the medial side of the midsagittal plane, out of the path of the advancing needle

16. Retrobulbar Block • The site of injection is just above the inferior orbital rim, usually 0.5cm medial to the lateral canthus (where the upper and lower lids come together at the lateral corner of the eye) • A 25 or 27 gauge needle NOT more than 2” in length is used for the injection and the lower lid is pulled downward right before the injection

18. Retrobulbar Block • The needle is advanced downward until the floor of the orbital rim is contacted and then the angle is raised to pass the globe of the eye and end up in the intraconal region • As the needle is advanced careful attention is placed on the position of the eye

19. Retrobulbar Block • If there is any resistance during passing the needle and the globe deviates downward coinciding with the resistance, then the globe is being contacted and the needle needs to be withdrawn and passed again at a lower angle • The needle is advanced about 3.5cm total in length and that should put its position passed the globe into the intraconal region posterior to the globe itself

20. Retrobulbar Block • After aspiration, 2-10cc (usually 5-7cc) of LA is injected and the needle is withdrawn • The injection should be easy and if ANY resistance is encountered during injection, then the needle needs to be withdrawn immediately as you may be injecting into the optic nerve itself • The choice of local anesthetics are usually Lidocaine 2% or Bupivicaine 0.75% • Addition of Epi may reduce bleeding and prolong the action of the anesthetic

21. Retrobulbar Block • Hyaluronidase, a hydrolyzer of connective tissue polysaccharides, is frequently added (3-7U/mL) • This helps enhance retrobulbar spread of the LA • A successful retrobulbar block is accompanied by anesthesia, paralysis of the injected eye, and loss of the oculocephalic reflex (eye moves when head is turned)

25. Retrobulbar Block • Possible Complications are: • Retrobulbar hemorrhage • Globe perforation • Optic nerve atrophy • Convulsions • Oculocardiac reflex (Bradycardia) • Acute neurogenic pulmonary edema • Trigeminal nerve block • Respiratory arrest

26. Retrobulbar Block • Forceful injection of LA can lead to injection directly into the opthalmic artery with retrograde flow to the brain with instantaneous seizures • The neurogenic apnea syndrome is most likely from injection of LA into the optic nerve sheath with spread into the CSF • The CNS is exposed to high concentrations of LA’s leading to unconsciousness followed by apnea within 5-20 minutes

27. Retrobulbar Block • The apnea usually resolves within an hour but you must be prepared to support respirations and oxygenation most likely with an ETT and mechanical ventilation until its resolution • The most common side effect BY FAR is Bradycardia from the Oculocardiac reflex • Most practitioners will carry a syringe with 1-2cc of Atropine in their pocket if doing eyes for the day just in case

28. Retrobulbar Block • The Oculocardiac reflex is a protective reflex • If any extrinsic pressure is applied to the eye (in this case an elevated pressure in the retrobulbar space) then the heart rate slows down to avoid pumping too much blood into the retina possibly leading to retinal hemorrhage and permanent retinal damage

29. Retrobulbar Block • Retrobulbar block is NOT usually performed in any patients with bleeding disorders or on any anticoagulants • Patients with severe myopia are also ususally not candidates as their globes are usually much longer than the regular eye • It is also contraindicated in anyone with an open eye injury • The added pressures from behind may lead to extrusion of globe contents through the injury site

30. Retrobulbar Block • Of interest is that any patients with bleeding disorders or on anticoagulants have been shown to be able to undergo corneal or cataract surgery under topical anesthesia without any increased incidence of postop hemorrhage or bleeding • It is a constant source of argument between Opthalmologist and Anesthetist, but the Opthalmologists actually have the data on their side to support this one!!!!

31. Peribulbar Block • The principle of this technique is to instill LA OUTSIDE of the muscle cone • This avoids proximity to the optic nerve • As compared to retrobulbar blocks, a larger volume of LA is needed • The onset time is longer and there is a higher failure rate with the quality of the anesthesia being less assured

32. Peribulbar Block • Advantages of the peribulbar block include less risk of eye penetration, less chance of damage or penetration of the optic nerve or opthalmic artery, and less pain on injection • A disadvantage besides the chance of a failed block, is that it often requires TWO injections and the chance of post injection ecchymosis is much higher

33. Peribulbar Block • A 25 or 27 gauge 1” needle is used • The first injection is in the same location and the same technique as with the Retrobulbar and 5-7mL of LA is injected • The second injection (if needed) is done with a 25 gauge 1” needle at the site of the medial canthus and directed upward until bone is contacted

34. Peribulbar Block • Then the angle is flattened out and at the max depth of the needle, about 5cc of LA is injected • The same LA solutions for Retrobulbar blocks are used with the Peribulbar technique • Complications are similar to those of the retrobulbar but occur with much less frequency since the depth of the block is much less

40. Peri vs. Retrobulbar • Retrobulbar block produces excellent anesthesia with paralysis of the extraocular muscles and better immobility of the eye during surgery • The majority of the patients will lose visual perception during the duration of the block • With peribulbar block, vision usually remains intact

41. Peri vs. Retrobulbar • Retrobulbar block carries a small but LARGER risk of hemorrhage, ocular perforation, subarachnoid and intradural injection, generalized seizures, optic nerve contusion and retinal vascular occlusion when compared to the PERIbulbar technique

42. Peri vs. Retrobulbar • However, the peribulbar technique FREQUENTLY requires a second injection and usually does NOT result in complete paralysis of the ocular muscles, so some movement may still be present • The risk of complications, though, is lower with the Peribulbar block • In either block, ptosis can occur in up to 5% of patients and may persist for up to 90 days

43. Airway Blocks • There are three airway blocks that can prove to be useful with awake intubations: • Superior Laryngeal Nerve block • Glossopharyngeal Nerve block • Transtracheal block

45. SLN Block • The Vagus nerve supplies innervation of the larynx • The laryngeal surface of the epiglottis and the laryngeal inlet down to the vocal folds are supplied by the internal laryngeal branch of the vagus nerve which reaches the larynx by piercing the thyrohyoid membrane

46. SLN Block • This branch can be blocked by anesthetizing the parent nerve, the Superior Laryngeal Nerve below the greater cornu of the Hyoid bone • This renders the laryngeal mucosa insensitive down to the vocal cords

47. SLN Block • The SLN is blocked using a 25 gauge ¾” needle and depositing 2-3mL of LA just below the greater cornu of the Hyoid bone • The patient is placed supine with the head extended and the Hyoid bone is palpated carefully • The LA of choice is usually Lidocaine 1 or 2%