anesthesia for eye surgery

1. Anesthesia for ophthalmic surgery
and complication
Prepared by:- Gammachis Akuma (Anesthetist)
February, 2023
2/20/2023 1

2. Outline
• Specific ophthalmic conditions and procedures
• Effects of commonly used anesthetic agents and
techniques on the eyes
• Preoperative assessment of ophthalmic patients
• Anesthesia for elective vs emergency (traumatic)
ophthalmic surgery
• General anesthesia
• Sedation techniques/MAC
• Regional anesthesia (preparation of LA, blocks,
infiltration, topical and complication)
2/20/2023 2

3. Objective
• At the end of this lesson participants will be
able:-
– To identify effect of anesthetic agent on IOP
– To describe systemic effect of commonly used
ophthalmic drugs
– To perform regional block for ophthalmic surgery
– To identify indications for providing regional
anesthesia for patients undergoing eye surgery.
– To describe complications that may result from
regional anesthesia for eye blocks.
2/20/2023 3

4. SPECIFIC OPHTHALMIC CONDITIONS
AND PROCEDURES
2/20/2023 4

5. 2/20/2023 5

6. 1. Cataract extraction
• Cataracts are opacities of the crystalline lens of
the eye.
• Cataract surgery incurs little risk since physiologic
stress is minimal and no blood loss or fluid shifts
occur
• No benefits derive from routine testing before
cataract surgery
2/20/2023 6

7. Cataract cont…
• Etiology may be varied
– Hereditary cataracts.
– Syndromes may be associated with cataracts.
– Metabolic causes
– Blunt or penetrating trauma
– Inflammation
– Tumors, such as retinoblastoma.
– Intrauterine infection
– Radiation for leukemia might cause cataracts.
– Chronic steroid use
2/20/2023 7

8. Cataract cont..
• Treatment involves surgical implantation of an
intraocular lens, which may need to be done
very early
• The procedure takes about 30 - 60 minutes,
but complications can be more frequent in
children,
• depending on the density of the cataract, the patient’s
cooperation, and the skill and experience of surgeons.
2/20/2023 8

9. 2. Vitreoretinal surgery
• Vitreoretinal surgery is performed for the repair
of a detached retina
– related to a defect in the retina, or secondary to an
underlying illness.
• Vitrectomy refers to surgical extraction of the
contents of the vitreous chamber and
replacement with a physiologic solution
2/20/2023 9

10. • The surgeon may also place an intraocular bubble of
either sulphur hexafluoride or perfluropropane to
tamponade the detached surfaces together
– Avoid nitrous oxide if an intraocular gas bubble is used.
– Avoid nitrous oxide in patients who have had an
intraocular bubble placed for several weeks after the
procedure.
– clear instructions in this regard for future anaesthetics.
2/20/2023 10

11. 3. Enucleation and evisceration
• Enucleation is the removal of the whole eye.
– surgical treatment of a retinoblastoma, significant eye
trauma or for cosmetic reasons where an eye is blind.
• It involves the dissection of EOM of the globe.
• similar risk here for the oculocardiac reflex,
although less risk of PONV?.
• Evisceration involves the removal of the contents
of the globe, but retention of the sclera?*
2/20/2023 11

12. 4. Glaucoma
• The causes of glaucoma are varied.
– Primary Congenital glaucoma is caused by a failure
of the development of the trabecular network
– Secondary Glaucoma is usually caused by a
blockage of existing drainage channels
• Treatment may be medical or surgical.
– Medical treatment consists of drugs used to
reduce IOP such as acetazolamide 15 – 30
mg/kg/day which suppresses aqueous production
2/20/2023 12

13. • After EUA and measurement of IOP, surgical
treatments may vary.
– Trabeculectomy, Iridectomy, Goniotomy and tube
shunt procedures.
• It takes approximately 30 to 60 minutes to
perform a glaucoma procedure.
2/20/2023 13

14. 5. Strabismus surgery
• It is ocular misalignment or deviation of one eye
relative to the visual axis of the other.
• Most strabismus is caused by refractive errors or
muscle imbalance, rare causes include
retinoblastoma or other serious ocular defects and
neurologic disease.
• The surgical correction of strabismus is a
repositioning of the EOMs.
– To strengthen a muscle, a resection is performed and To
weaken a muscle, a recession is performed.
2/20/2023 14

15. • In severe cases, a resection may be performed
on one muscle and a recession on the
opposing muscle.
• Because visual maturation occurs by age 5
years, strabismus correction usually is
attempted early in childhood.
• It takes 15 to 30 minutes to repair one muscle
• Strabismus repair causes the highest incidence
of oculocardiac reflex?
2/20/2023 15

16. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Atropine
• Used to produce mydriasis and cyclopiegia.
• The 1% solution contains 0.2 to 0.5 mg of
atropine per drop.
• Systemic reactions, include tachycardia,
flushing, thirst, dry skin, and agitation.
• Atropine is contraindicated in closed-angle
glaucoma?.
2/20/2023 16

17. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Scopolamine
• One drop of the 0.5% solution has 0.2 mg of
scopolamine.
• CNS excitement can be treated with
physostigmine 0.015 mg/kg IV, repeated one or
two times in a 15- minute period.
• It is contraindicated in closed-angle glaucoma.
2/20/2023 17

18. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Phenylephrine
• Phenylephrine is used to produce capillary decongestion
and pupillary dilatation.
• Applied to the cornea, it can cause palpitations,
nervousness, tachycardia, headache, nausea and
vomiting, severe hypertension?, reflex bradycardia, and
subarachnoid hemorrhage.
• Solutions of 2.5%, 5%, and 10% (6.25 mg phenylephrine
per drop) are available.
2/20/2023 18

19. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Epinephrine
• Topical 2% epinephrine will decrease aqueoua secretion,
improve outflow, and lower IOP in open-angle
glaucoma.
• Side-effects include hypertension, palpitations, fainting,
pallor, and tachycardia.
• The effects last about 15 minutes.
• One drop of 2% solution contains 0.5 to 1 mg of
epinephrine.
2/20/2023 19

20. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Timolol Maleate
• is a beta-blocker used in the treatment of
chronic glaucoma.
• Side- effects include light-headedness, fatigue,
disorientation, depressed CNS function, and
exacerbation of asthma/ bronchospasm,
• increased SVR?, bradycardia, decreased FEV,
and potentiation of systemic beta-blockers can
occur.
2/20/2023 20

21. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Acetylcholine
• Acetylcholine can be injected intraoperatively
into the anterior chamber to produce miosis.
Side-effects are due to its parasympathetic
action they include hypotension, bradycardia,
and bronchospasm.
2/20/2023 21

22. SYSTEMIC EFFECTS OF OPHTHALMIC DRUGS
Echothiophate Iodide
• A cholinesterase inhibitor, used as a miotic
agent.
• prolong the effect of both succinyicholine and
ester-type local anesthetics?.
• Levels of pseudocholinesterase decrease by
80% after 2 weeks on the drug.
• Succinyicholine and ester-type local
anesthetics should be avoided.
2/20/2023 22

23. Acetazolamide
• Causes carbonic anhydrase inhibition and interferes
with the formation of aqueous humor and lowers IOP.
• Metabolic acidosis, dehydration, electrolyte,
abnormalities long term therapy may result in
dyspepsia, allergies.
Mannitol
• Catheterizing
• increase in circulating blood volume w/c can cause
CHF /poor ventricular function/, pulmonary edema,
hypo/hypertension, myocardiac ischemia, renal failure
2/20/2023 23

24. •
2/20/2023 24

25. Effects of commonly used anesthetic
agents and techniques on the eyes/IOP
Why we concerned more on IOP?
• It interfere with choroidal and retinal blood
supply & corneal metabolism, potentially causing
– retinal ischemia and corneal opacification.
– choroidal hemorrhage, intraocular bleeding, and
expulsion of intraocular contents.
• Largely dec., increase the risk of retinal
detachment, vitreous hemorrhage, and corneal
edema.
2/20/2023 25

26. Effect of cardiac and respiratory variables on
IOP
2/20/2023 26

27. Any anaesthetic event that alters these
parameters can affect intraocular pressure
• laryngoscopy
• Intubation
• Coughing/straining/vomiting 30-40mmHg
• airway obstruction
– Hypoxia /Hypercapnia
• Trendelenburg position
• Face mask ventilation
– Normal blink increase the IOP
– Force full squeeze can increase more
• Drugs
2/20/2023 27

28. Intravenous Anesthetics
IVA drugs decrease intraocular pressure
Exception is ketamine, which usually raises ABP
and does not relax EOM.
 Current study shows no significant increase in IOP at
usual dose rather, it may cause nystagmus and
blepharospasm which limit its use in eye surgery
Narcotic has little effect
• Atropine usual dose don’t cause a significant
increase in IOP even with open angle glaucoma?
2/20/2023 28

29. Inhaled anesthetics
• IAA dec. IOP in proportion the depth anaesthesia.
30% -40%
• This decrease has multiple causes:
– drop in blood pressure reduces choroidal volume
– relaxation of the EOM lowers wall tension
– pupillary constriction facilitates aqueous outflow
Nitrous oxide? Should not be used
for patients who had an intravitreal injection of sulfur
hexafluoride (SF6) within the last 30 days or
octafluoropropane (C3F8) within the last 90 days?
2/20/2023 29

30. Muscle relaxants
• Sux increases IOP by 5-10 mm Hg?
– principally through prolonged contracture of the
EOM (Choroidal vascular dilation, relaxation of orbital
smooth muscles)?
• NDMR minimal effect IOP.
• NDMR has 2 effect:-
– direct effect lower IOP by relaxing Extraocular
muscles;
– indirectly paralysis of respiratory muscle causes
alveolar hypoventilation which increase IOP.
2/20/2023 30

31. 2/20/2023 31

32. Strategies to prevent increases in IOP
• Avoid direct pressure on the globe
– Patch eye with fox shield
– no retro bulbar or peribular injection
• Avoid increase in CVP
– Prevent coughing and straining during induction and
intubation, extubation
– Avoid head down/Position head up tilt 15 -20%
• Adequate premedication- avoided heavy sedation with?
– IV lidocaine or esmolol to obtund sympathetic reflex
• Avoid pharmacological agent that increase IOP
– Sux/Ketamine?
2/20/2023 32

33. Preoperative Evaluation
• Establishment of rapport and communication among
the anesthetist, the surgeon, and the patient
• Explanation of potential complications, balanced with
information concerning probability or frequency of
permanent adverse sequelae
• Such an approach also fulfills the medicolegal
responsibilities of the physician to obtain informed
consent.
• Instructions regarding fasting
2/20/2023 33

34. History
• Thorough Hx and PE are the foundation of safe
patient care
• A complete list of medications
– Anesthetist should be aware of potential systemic effects
of chronically administered eye drops or oral medications
• History of any allergies to medicines, foods, or tape
should be documented
• Previous Hx hospitalization and surgical procedures
and history of adverse reactions to anesthesia is
mandatory
2/20/2023 34

35. • The Patients might be very young or very old and have
comorbidity
• Infants often present with apnea of prematurity,
bronchopulmonary dysplasia, and PDA or congenital
• Elderly adults are likely to present with CAD, valvular
heart disease, HTN?, cerebrovascular disease, COPD,
diabetes, dementia, Parkinson's disease, renal disease,
arthritis, osteoporosis, or cancer
2/20/2023 35

36. • Patient factors that could influence anesthetic
management includes dementia, deafness,
language barrior, restlessness leg syndrome,
OSA, tremors, dizziness, and claustrophobia
• particular attention should be paid to
positioning issues such as severe scoliosis or
orthopnea
• check for signs of major cardiac or pulmonary
decompensation
2/20/2023 36

37. PULMONARY CONSIDERATIONS
• Standard airway assessment is always performed
• Preoperative risk reduction strategies include
cessation smoking, treatment of airflow obstruction
with bronchodilators or steroids, and administration
of antibiotics for respiratory infections.
• Patients should be assessed for sleep apnea
Intravenous sedation is often contraindicate in these
patients.
2/20/2023 37

38. • Severe hyperglycemia and hypoglycemia
should be avoided, FBS should be checked
preoperatively.
• The potential for autonomic neuropathy
needs to be considered, especially when
elevating the patient from the supine position.
2/20/2023 38

39. ANTICOAGULANTS
• Many elderly patients are on antiplatelet or
anticoagulant therapy because of CAD or
vascular disease
• Are at higher risk for perioperative hemorrhagic
events, including retrobulbar hemorrhage,
circumorbital hematoma, intravitreous bleeding,
and hyphema.
• The dilemma whether to continue or suspend
antithrombotic therapy prior to surgery?.
2/20/2023 39

40. • Perioperative management, risks of thrombotic
vs hemorrhagic complications.
• The risk of peirop hemorrhagic complication
depend on:
– The degree of anticoagulation.
– The hemorrhagic potential of the surgical procedure
serious hemorrhagic complication as in orbital and
oculoplastic surgery; of intermediate probability in
vitreoretinal, glaucoma, and corneal transplant
surgery; and least likely in cataract surgery
2/20/2023 40

41. • Another area of potential concern CAD patients
with drug-eluting stents
• Delaying elective surgery for at least 4 to 6 weeks
after placement of a bare metal stent and for 6-
12 months after drug-eluting stent placement
• Regional anesthesia for eye surgery also presents
another bleeding risk.
• Traditionally, some physicians held that patients
taking antithrombotic medications should not
receive a regional eye block owing to increased
2/20/2023 41

42. Preoperative testing
• Depending on the medical history and physical
status of the patient, as well as the nature of the
surgical procedure
• routine laboratory tests and ECG have not been
demonstrated to improve outcome
– New chest pain, decreased exercise tolerance,
palpitations, near-syncope, fatigue, or dyspnea, or
irregular pulse on examination.
2/20/2023 42

43. • Serum electrolytes:- History of severe vomiting or
diarrhea, poor oral intake, changes in diuretic
management, or arrhythmia.
• Urea nitrogen:- Signs or symptoms of renal
problem.
• Serum glucose:- Polydipsia, polyuria, or weight loss.
• Hematocrit/hemoglobin:- Hx of bleeding, poor oral
intake, fatigue, decreased exercise tolerance, or
tachycardia.
2/20/2023 43

44. Anesthesia for elective eye surgery
• Most elective eye surgery is performed with a
topical or regional anesthetic technique,
combined with monitored anesthesia care (MAC).
– Nature and duration of procedure
– Coagulation status
– Patient’s choice
– Ability to communicate and cooperate
– All of these factors must be considered when
selecting premedication
2/20/2023 44

45. Requirements for Ophthalmic Surgery
 Akinesia
 Profound analgesia
 Minimal bleeding
 Prevent/manage of oculo-cardiac reflex
 Control of IOP
 Awareness of drug interactions
 Emergence without coughing, straining or vomiting
2/20/2023 45

46. GENERAL ANESTHESIA
PREMEDICATION
• Pediatric patients often have associated congenital
disorders.
• Adult patients are usually elderly (HTN, DM, CAD).
• Special precautions should be taken to avoid
coughing, bucking, and/or PONV, i.e. deep
anesthesia, complete paralysis, IV lidocaine
2/20/2023 46

47. GENERAL ANESTHESIA
INDUCTION
The choice of induction technique for eye surgery
usually depends more on
– the patient’s medical problems
– the patient’s eye disease
– the type of surgery contemplated.
• Propofol/thiopenton
• NDMR vs Suxamethonium
• Consider using a reinforced or preformed right-
angle endotracheal tube
2/20/2023 47

48. MONITORING & MAINTENANCE
• Maintenance with IAA or TIVA
• shared airway, making pulse oximetry mandatory for
all ophthalmologic procedures.
• End-tidal CO2
• Body TM for paediatrics
• Continuous monitoring for breathing-circuit
disconnections or unintentional extubation.
• increases the importance of ECG
• Risk of hypotensive intraop is high? volume
resuscitation + ephedrine should be anticipated
2/20/2023 48

49. GENERAL ANESTHESIA
EXTUBATION & EMERGENCE
• a smooth emergence from general anesthesia
• deep level of anesthesia
• intravenous lidocaine (1.5 mg/kg)
• extubate early to avoid coughing and bucking
on the ETT
• Anti emetic for PONV
• Analgesia
2/20/2023 49

50. Anesthesia for emergency eye surgery
• True emergencies such as ocular burns and central
retinal artery occlusion require immediate intervention
• Urgent situations include open globe injuries,
endophthalmitis, acute narrow-angle glaucoma, acute
retinal detachment, corneal foreign body, and lid
laceration.
• Semi urgent conditions include ocular tumors, blowout
fractures of the orbit, congenital cataract, and chronic
retinal detachment.
2/20/2023 50

51. PREOPERATIVE ASSESSMENT
• Anesthetic concerns
– The mechanism of eye trauma and possibility of
associated traumatic injuries (e.g, orbital or
maxillofacial trauma, skull fractures, subdural
hematoma, intracranial trauma, cervical spine
trauma),
– risk extrusion of ocular contents if IOP becomes
elevated, and
– risk of pulmonary aspiration if the stomach is full
2/20/2023 51

52. • Findings of the eye exam performed by the
ophthalmologist, including the size of any
ocular perforation.
• Larger defects have a greater chance of extrusion of
ocular contents
• Standard issues for a preanesthetic
consultation(PE evaluation of airway anatomy,
last oral intake of fluids and/or solids.
2/20/2023 52

53. CHOICE OF ANESTHETIC TECHNIQUE
• Anesthetic goals during emergent eye surgery are
to provide profound analgesia and to prevent
coughing, retching, vomiting, forceful blinking, or
crying
• GA is the most common anesthetic technique for
surgical procedures to treat eye trauma,
especially for open globe injuries.
• In pediatric patients, general anesthesia is almost
always preferred because crying and struggling
2/20/2023 53

54. 2/20/2023 54

55. 2/20/2023 55

56. Maintenance:-
• A deep plane of anesthesia is maintained during
ophthalmologic surgery so that movement and
coughing are prevented.
• A primary inhalation technique or TIVA
• It is important to prevent coughing, retching, and
vomiting during and after extubation
• Prophylactic antiemetic agents (eg, ondansetron 4
mg and dexamethasone 4 mg
• Administration of IV lidocaine 1 to 2 mg/kg before
extubation
2/20/2023 56

57. Specific considerations for intraocular surgery
• Position the head at the top edge of the table to
avoid surgical back and neck pain due to poor
posture
• Support the head on a comfortable headrest to
prevent head movement.
• Position the head above or at the level of the
heart
• Restrain arms to the patient's side with the draw
sheet or secure straps on the arm boards to
prevent sudden arm movement.
2/20/2023 57

58. What OCR?
• Caused by traction on the EOM,
– ocular manipulation
– manual pressure on the globe
– Pinching of conjunctiva
• OCR is seen during eye muscle surgery, detached
retina repair, enucleation and etc
• Manifested by bradycardia, ectopic, nodal rhythm,
AV block, cardiac arrest
• Risk factor pre op anxiety, squint surgery, acidosis,
hypoxia, hypercarbia, increased vagal owing to
age, light anesthesia
2/20/2023 58

59. 2/20/2023 59

60. 2/20/2023 60

61. 2/20/2023 61

62. 2/20/2023 62

63. 2/20/2023 63

64. Regional Anesthesia for Ophthalmic
Surgery
• Options for local anesthesia for eye surgery
include:-
 Topical application of local anesthetic
 Placement of a retrobulbar, peribulbar
Sub-Tenon (episcleral) block
• Each of these techniques is commonly combined
with intravenous sedation.
2/20/2023 64

65. • Local anesthesia is preferred to general anesthesia for
eye surgery.
• Because local anesthesia involves less physiological
trespass.
• Less likely to be associated with postoperative nausea
and vomiting.
• The patient can return to ambulation faster.
• Most patients meet recovery discharge criteria at the
end of surgery.
•
2/20/2023 65

66. • Eye block procedures have potential complications and
may not provide adequate ophthalmic akinesia or analgesia.
• The appropriate equipment and qualified personnel
required to treat the complications of local anesthesia.
• And induce general anesthesia must be readily available.
2/20/2023 66

67. FACIAL NERVE BLOCKS
• A facial nerve block is performed when complete
akinesia of the eyelids is desired.
• Three methods for the eyelid block are as follows:
1. Modified van Lint block:
• The needle is placed 1cm lateral to the orbital rim,
• And 2 to 4mL of anesthetic is injected deep on the
periosteum just lateral to the superolateral and
inferolateral orbital rim.
• The disadvantages of this block include discomfort,
proximity to the eye, and common postoperative
ecchymoses.
2/20/2023 67

68. 2. O’Brien block:
• The mandibular condyle is palpated inferior to the
posterior zygomatic process and anterior to the tragus of
the ear as the patient opens and closes the jaw.
• The needle is inserted perpendicular to the skin
approximately 1cm to the periosteum.
• As the needle is withdrawn, 3mL of anesthetic is injected
2/20/2023 68

69. 3. Nadbath-Rehman block:
• A 12-mm, 25-gauge needle is inserted perpendicular to
the skin between the mastoid process and the posterior
border of the mandible.
• The needle is advanced its full length, and after careful
aspiration, 3 mL of anesthetic is injected as the needle is
withdrawn.
• This blocks the entire trunk of the facial nerve.
2/20/2023 69

70. • The patient should be told to expect a lower facial droop for
several hours postoperatively.
• The major disadvantage to this block is the proximity of the
injection to important structures, such as the carotid artery
and the glossopharyngeal nerve.
• This block is not recommended because it has been
associated with vocal cord paralysis, laryngospasm,
dysphagia, and respiratory distress.
2/20/2023 70

71. RETROBULBAR BLOCKADE
• Local anesthetic is injected behind the eye into the
cone formed by the extraocular muscles.
• A facial nerve block is utilized to prevent blinking.
• A blunt-tipped 25-gauge needle penetrates the lower
lid at the junction of the middle and lateral one-third
of the orbit.
• Awake patients are instructed to stare supranasally as
the needle is advanced toward the apex of the muscle
cone.
2/20/2023 71

72. • Commonly, patients undergoing such eye blocks will
receive a brief period of deep sedation or general
anesthesia during the block.
• After aspiration of the syringe to preclude intravascular
injection.
• Then 2 to 5 mL of local anesthetic is injected, and the
needle is removed.
• Lidocaine 2% or bupivacaine (or ropivacaine) 0.75%
are common.
2/20/2023 72

73. • The addition of epinephrine may reduce bleeding and prolong the
anesthesia.
• A successful retrobulbar block is accompanied by anesthesia, akines
and abolishment of the oculocephalic reflex.
• Complications of retrobulbar injection of local anesthetics include
retrobulbar
hemorrhage
perforation of the globe
optic nerve injury
intravascular injection with resultant convulsions
 oculocardiac reflex
 trigeminal nerve block, respiratory arrest
rarely, acute neurogenic pulmonary edema.
2/20/2023 73

74. • Forceful injection of local anesthetic into the ophthalmic
artery causes retrograde flow toward the brain and may result
in an instantaneous seizure.
• The postretrobulbar block apnea syndrome is probably due to
injection of local anesthetic into the optic nerve sheath, with
spread into the cerebrospinal fluid.
• In this situation, the central nervous system is exposed to
high concentrations of local anesthetic.
• Leading to mental status changes that may include
unconsciousness.
2/20/2023 74

75. • Apnea occurs within 20 min and resolves within an hour.
• Treatment is supportive, with positive-pressure ventilation
to prevent hypoxia, bradycardia, and cardiac arrest.
• Adequacy of ventilation must be constantly monitored in
patients who have received retrobulbar anesthesia.
• The adjuvant hyaluronidase is frequently added to local
anesthetic solutions used in eye blocks.
• To enhance the spread and density of the block.
2/20/2023 75

76. • Patients may rarely experience an allergic reaction to
hyaluronidase.
• Retrobulbar hemorrhage, cellulitis, occult injury, and contact
allergy to topical eye drops must be ruled out in the
differential diagnosis.
• Retrobulbar injection is usually not performed in patients
with bleeding disorders or receiving anticoagulation therapy
2/20/2023 76

77. • Because of the risk of retrobulbar
hemorrhage, extreme myopia.
• Because the elongated globe increases the
risk of perforation, or an open eye injury.
• Because the pressure from injecting fluid
behind the eye may cause extrusion of
intraocular contents through the wound.
2/20/2023 77

78. PERIBULBAR BLOCKADE
• The needle does not penetrate the cone
formed by the extraocular muscles.
• Advantages of the peribulbar technique
include less risk of penetration of the
globe, optic nerve, and artery and less
pain on injection.
• Disadvantages include a slower onset and
an increased likelihood of ecchymosis.
2/20/2023 78

79. • Both techniques will have equal success at
producing akinesia of the eye.
• The peribulbar block is performed with the
patient supine and looking directly ahead.
• After topical anesthesia of the conjunctiva,
one or two transconjunctival injections are
administered.
2/20/2023 79

80. • As the eyelid is retracted, an inferotemporal
injection is given halfway between the lateral
canthus and the lateral limbus.
• The needle is advanced under the globe,
parallel to the orbital floor; when it passes
the equator of the eye, it is directed slightly
medial (20°) and cephalad (10°), and 5 mL
of local anesthetic is injected.
2/20/2023 80

81. • Anatomic landmarks for the introduction of a needle or catheter in
most frequently employed eye blocks: (1) medial canthus peribulbar
anesthesia, (2) lacrimal caruncle, (3) semilunaris fold of the
conjunctiva, (4) medial canthus episcleral anesthesia, and (5) inferior
and temporal peribulbar anesthesia.
2/20/2023 81

82. Sub-Tenon (Episcleral) Block
• Tenon’s fascia surrounds the globe and
extraocular muscles.
• Local anesthetic injected beneath it into the
episcleral space spreads circularly around the
sclera and to the extraocular muscle sheaths.
• A special blunt curved cannula is used for a sub-
Tenon block.
2/20/2023 82

83. • After topical anesthesia, the conjunctiva is lifted along with Tenon’s
fascia in the inferonasal quadrant with forceps.
• A small nick is then made with blunt-tipped scissors.
• Then slid underneath to create a path in Tenon’s fascia that follows
the contour of the globe and extends past the equator.
• While the eye is still fixed with forceps, the cannula is inserted,
and 3 to 4 mL of local anesthetic is injected.
2/20/2023 83

84. • Complications with sub-Tenon blocks are significantly less
than with retrobulbar and peribulbar techniques.
• Globe perforation, hemorrhage, cellulitis, permanent visual
loss, and local anesthetic spread into cerebrospinal fluid have
been reported.
2/20/2023 84

85. TOPICAL ANESTHESIA OF THE EYE
• Use simple topical local anesthetic techniques for anterior
chamber (eg, cataract) and glaucoma operations rather than
local anesthetic injections.
• A typical regimen for topical local anesthesia involves the
application of 0.5% proparacaine local anesthetic drops
• Repeated at 5-min intervals for five applications,
• Followed by the topical application of a local anesthetic gel
(lidocaine plus 2% methyl-cellulose) with a cotton swab to the
inferior and superior conjunctival sacs.
2/20/2023 85

86. • Ophthalmic 0.5% tetracaine may also be utilized.
• Topical anesthesia is not appropriate for posterior chamber
surgery eg, retinal detachment repair with a buckle.
• It works best for faster surgeons using a gentle surgical
technique that does not require akinesia of the eye.
2/20/2023 86

87. SEDATION TECHNIQUE/MAC
• Deep sedation is almost never used intraoperatively
because of the risks of apnea, aspiration, and unintentional
patient movement during surgery.
• Though sometimes used during placement of ophthalmic
nerve blocks.
• An intraoperative light sedation regimen that includes small
doses of midazolam, with or without fentanyl or sufentanil,
is recommended.
2/20/2023 87

88. • Doses vary considerably among patients but should be
administered in small increments.
• Patients may find the administration of eye blocks
frightening and uncomfortable.
• Many anesthesia providers will administer small,
incremental doses of propofol to produce a brief state of
unconsciousness during the regional block.
2/20/2023 88

89. • Some will substitute a bolus of opioid to produce a brief period of
intense analgesia during the eye block procedure.
• Remifentanil 0.1–0.5 mcg/kg or alfentanil 375–500 mcg.
• Administration of an antiemetic should be considered if an opioid
is used.
• Regardless of the anesthetic technique, American Society of
Anesthesiologists standards for basic monitoring must be
employed.
• And equipment and drugs necessary for airway management and
resuscitation must be immediately available.
2/20/2023 89

90. What Is MAC Anesthesia?
• MAC anesthesia — also called monitored anesthesia
care or MAC, is a type of anesthesia service during
which a patient is typically still aware, but very
relaxed.
• The amount of sedation provided during MAC is
determined by the anesthesia professional providing
the care.
2/20/2023 90

91. • A patient may be only lightly sedated, moderately
sedated, or deeply sedated to the point that they’re
completely unaware of the procedure.
• The patient may not even remember any events during
the procedure.
• The level of sedation administered depends on the
health of the patient and the type of surgical or
diagnostic procedure being done.
2/20/2023 91

92. • This type of anesthesia is typically used for outpatient
procedures where the patient will be going home once
the anesthesia wears off.
• Medications used during MAC include:
midazolam
fentanyl
propofol
2/20/2023 92

93. • Monitored anesthesia care is the first choice in 10 to 30% of all
surgical procedures.
• It’s typically used for quick surgical procedures.
• MAC is called monitored anesthesia care because a patient’s vitals are
constantly monitored to assess pain control and vital functions.
• Surgical procedures that use MAC include:
 endoscopy
 dental procedures
 bronchoscopy
 eye surgery
 otolaryngologic surgery
 cardiovascular surgery
 neurosurgery
 pain management procedures
2/20/2023 93

94. MAC anesthesia side effects
• Side effects for monitored anesthesia care are usually
minimum.
• There are cases where one can be allergic to anesthesia,
but the anesthesiologist will work to monitor your reaction
upon administration.
• Common side effects include:
drowsiness
nausea
vomiting
trouble waking from sedation
cardiorespiratory depression
2/20/2023 94

95. REFERENCES
 Miller’s Anesthesia 9th edition volume 2
 Morgan & Mikhail’s Clinical Anesthesiology 6th Edition
 Alvaro A Macias, M., et al. (Mar 23, 2021.). "Anesthesia
for emergency eye surgery." www.uptodate.com.
 WFSA. Anesthesia Tutorial of The Week 197 20th
September 2010. e-safe
 Jatin D. Mary C. Continuing Education in Anesthesia,
Critical Care & Pain | Volume 7 Number 5 2007. e-safe
 Paul Barash 8th edition
2/20/2023 95