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Basics of Anesthesia > Week 5 - MAC and Ophthalmic Anesthesia > Flashcards

Week 5 - MAC and Ophthalmic Anesthesia Flashcards

1
Q

What is the definition of MAC?

A

A specific anesthesia service in which an anesthesiologist has been requested to participate in the care of a patient undergoing a diagnostic or therapeutic procedure

Anesthesia care that includes the monitoring of the patient by a practitioner who is qualified to administer anesthesia — provider of MAC must be able to convert to general when necessary

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2
Q

What is the difference between minimal, moderate, and deep sedation?

A

Minimal: normal response to verbal stimulation, unaffected airway/ventilation/cardiovascular function

Moderate: purposeful response to verbal or tactile stimulation, no airway intervention required, adequate spont ventilation, usually maintained CV function

Deep: purposeful response after repeated or painful stimulation, airway intervention may be required, spont ventilation may be inadequate, CV function is usually maintained

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3
Q

What are the goals of MAC?

A
  • # 1 is Safety (maintenance of respiration and physiological reflexes
  • Comfort (physiological and psychological)
  • Cooperation
  • Communication (with surgeon and patient) – set expectations
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4
Q

What is the dosing of Precedex for non-intubated procedural sedation?

A

Loading dose = 1mcg/kg over 10 mintues (adult)

Maintenance dose = 0.6 mcg/kg/hr and titrate 0.2-1 mcg/kg/hr

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5
Q

What is a normal intraocular pressure?

A

12-20 mmHg (16 +/-5mmHg)

  • determined by volume of aqueous humor, vitreous and blood within the eye, scleral compliance, extraocular muscle tone exerting inward pressure
  • increased pressure damages blood vessels
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6
Q

How can anesthesia increase IOP?

A
  • Venous congestion (coughing or bucking can cause transient increases up to 40mmHg)
  • Mechanical pressure on eye
  • Extraocular muscle contraction (succinylcholine can produce an increase of about 9mmHg in 1-4 min after admin)
  • Hypertension, Hypoxemia, Hypoventilation
  • Ketamine? (does cause nystagmus)
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7
Q

What anesthetic agents decrease intraocular pressure? Which increase it?

A

Decrease IOP:

  • Inhaled anesthetics (volatile agents > nitrous oxide)
  • Propofol, Benzos, Opioids

Increase IOP:
-Succinylcholine

**NDMRs have no or minimal effect on IOP

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8
Q

What is the Oculocardiac Reflex? What can it be triggered by?

A

“Five and Dime” – trigeminal nerve (ophthalmic division) provides the afferent limb of OCR and vagus nerve provides the efferent limb
-Causes bradycardia, and other arrhythmias including junctional, AV blockade, multifocal PVCs, V-tach, or asystole

-can be triggered by pressure on the globe, traction on extraocular muscles, conjunctiva, or orbital structures, regional ophthalmic anesthesia such as a retrobulbar or peribulbar block, ocular trauma, or pressure on tissue within the orbital apex after enucleation

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9
Q

How do you manage the oculocardiac reflex?

A

1 notify surgeon to stop ocular manipulation

If bradycardia doesn’t resolve (and hypertensive) administer atropine or glycopyrrolate 10-20mcg/kg

Optimize oxygenation

CPR if necessary

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10
Q

What is the MOA and systemic effect of acetylcholine for ocular procedures?

A

Cholinergic Agonist – causes miosis

Effect: bronchospasm, bradycardia, hypotension

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11
Q

What is the MOA and systemic effect of acetazolamide for ocular procedures?

A

Carbonic Anhydrase Inhibitor – decreases IOP

Effect: diuresis, hypokalemic metabolic acidosis

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12
Q

What is the MOA and systemic effect of atropine for ocular procedures?

A

Anticholinergic – causes mydriasis

Effect: central anticholinergic syndrome

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13
Q

What is the MOA and systemic effect of cyclopentolate for ocular procedures?

A

Anticholinergic – causes mydriasis

Effect: disorientation, psychosis, convulsions

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14
Q

What is the MOA and systemic effect of echothiophate for ocular procedures?

A

Cholinesterase Inhibitor – causes miosis and decreases IOP

Effect: prolongation of succinylcholine and mivacurium paralysis, bronchospasm

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15
Q

What is the MOA and systemic effect of epinephrine for ocular procedures?

A

Sympathetic Agonist – causes mydriasis and decreases IOP

Effect: HTN, bradycardia, tachycardia, headache

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16
Q

What is the MOA and systemic effect of Phenylephrine for ocular procedures?

A

Alpha-Adrenergic Agonist – causes mydriasis and vasoconstriction

Effect: HTN, tachycardia, dysrhythmias

17
Q

What is the MOA and systemic effect of scopolamine for ocular procedures?

A

Anticholinergic – causes mydriasis and vasoconstriction

Effect: central anticholinergic syndrome

18
Q

What is the MOA and systemic effect of timolol for ocular procedures?

A

Beta-Adrenergic Blocking Agent – decreases IOP

Effect: bradycardia, asthma, CHF

19
Q

What are the regional eye anesthetics?

A

“Needle Based” Blocks: Retrobulbar block (intraconal) and Peribulbar block (extraconal)

“Cannula Based” Block: local anesthetic is instilled via a blunt cannula and Sub-Tenon’s block

20
Q

What are complications of a retrobulbar block?

A
  • OCR (Initial pressure can cause OCR, then anesthetic effects ablate the response)
  • Retrobulbar or superficial hemorrhage
  • Patient on anticoagulants?
  • Intraocular injection (globe puncture)
  • Optic nerve trauma
  • Intravascular injection
  • Brainstem anesthesia
21
Q

What will you see with Brainstem Anesthesia with a RBB?

A

Loss of consciousness

Apnea

Cardiac instability

Possible contralateral mydriasis and contralateral eye block

22
Q

What will you see with Intravascular Injection with a RBB?

A

Loss of consciousness

Possible apnea

Possible cardiac instability

Seizure activity

23
Q

What is a Sub Tenon’s Block?

A

Instilling LA through a blunt cannula into the space between the sclera and the sub-Tenon’s capsule

24
Q

What are anesthetic considerations for cataract surgery?

A
  • Relatively short cases 15-45 minutes
  • Mainly topical anesthetic with RN sedation or MAC (Small doses of versed or no sedation at all)
  • Retrobulbar or peribulbar anesthesia for difficult cases or when akinesia is desired (Short acting sedative and/or narcotic while block is placed, then versed as needed)
25
Q

What are anesthetic considerations for retinal surgery?

A
  • Retinal detachment due to trauma or chronic disease such as diabetes
  • Longer case (~2-3 hours) and requires akinesa
  • Usually done under regional block with sedation or GA
  • Surgical interventions: sceleral buckle, vitrectomy, laser, cryotheraphy, and injection of intravitreal gas
  • Keep MAP at baseline to ensure optic nerve perfusion

**avoid nitrous oxide if surgeon injects sulfur hexafluouride into the aqueous humor (gas bubble can take 10-28 days to reabsorb)

26
Q

What is a scleral buckle?

A
  • The element pushes in, or “buckles,” the sclera toward the middle of the eye
  • This buckling effect on the sclera relieves the pull (traction) on the retina, allowing the retinal tear to settle against the wall of the eye

*The buckle effect may cover only the area behind the detachment, or it may encircle the eyeball like a ring

27
Q

What are anesthetic considerations for glaucoma surgery?

A
  • Can be done under sedation with ocular block (typically RBB), or GA
  • Make sure not to contribute to increased IOP — “Smooth” GA induction and remind patient not to cough, or to warn surgeon and team if they need to cough
  • Be aware of IOP and pharmacology – avoid drugs that cause midriasis (caution with scopolamine)
28
Q

What are anesthetic considerations for strabismus surgery “squint”?

A
  • GA
  • High incidence of OCR
  • High incidence of PONV
  • Increased risk of MH?
  • Goal to have patient awake and alert for adjustments as soon as possible
  • Some surgeons will inject local at end, or topical tetracaine
29
Q

What are anesthetic considerations for eye trauma open globe injuries?

A
  • Balance of risk of IOP with RSI
  • Control of airway supersedes
  • Consider pretreatment with non-depolarizer
  • Consider slight rev. Trendelenburg with induction
  • Continuation of muscle relaxation for case

Basics of Anesthesia (35 decks)

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