Ophthalmic Anesthesia Flashcards
Optic Neve photo
The ophthalmic artery is ______.
the main blood supply to the eye. It branches from the internal carotid artery near the Circle of Willis
The ophthalmic artery divides into the ______.
central retinal artery and the posterior ciliary arteries
The superior and inferior ophthalmic veins transport venous blood to the cavernous sinus
photo of the vascular supply to the eye
Function of the lacrimal gland
- produces the aqueous layer of the eye’s tear film
- aqueous layer of tears is made up of water, proteins, vitamins, electrolytes, and other substances
- these substances help lubricate the eye, wash away debris, and promote overall eye health
- tears get to the eye through the puncta
- can trigger reflex tears when something gets in your eye
Miosis = ____
What medications cause miosis?
constriction of the pupil
acetylcholine
Glaucoma = ____
What meds treat it?
increased intraocular pressure
Acetazolamide, Echothiophate ,Timolol
Mydriasis = ______
What causes it?
Pupillary dilation, ophthalmic capillary decongestion
Atropine, Cyclopentolate, Epinephrine, Phenylephrine, Scopolamine
Phenylephrine drops: clinical use? Systemic effects?
causes MYDRIASIS
systemic effects: SEVERE HTN, ARRYTHMIAS, HEADACHES, TREMORS, MYOCARDIAL ISCHEMIA
Epinephrine drops: clinical use? Systemic effects?
used for: REDUCES IOP
systemic effects: TACHYARRHYTHMIAS , PVC
Timilol drops: clinical use? Systemic effects?
used for: REDUCES IOP & TREATS GLAUCOMA
systemic effects: BRADYCARDIA, HYPOTENSION, CHF, EXACERBATION OF ASTHMA AND MYASTHENIA GRAVIS
Echthiophate drops: clinical use? Systemic effects?
used for: TREATS GLAUCOMA & MIOSIS
systemic effects: PROLONGED RESPONSE TO SUCCINYLCHOLINE AND ESTER LINKED LOCAL ANESTHETICS
Acetylcholine drops: clinical use? Systemic effects?
causes miosis
systemic effects: BRADYCARDIA, HYPOTENSION, BRONCHOSPASM, INCREASES SECRETIONS
CYCLOPENTOLATE drops: clinical use? Systemic effects?
causes MYDRIASIS. Used to dilate pupil.
systemic effects: DISORIENTATION, DYSARTHRIA, SEIZURES
SCOPOLAMINE drops: clinical use? Systemic effects?
causes MYDRIASIS. Used to dilate the pupil.
systemic effects: DISORIENTATION AND HALLUCINATIONS
COCAINE drops: clinical use? Systemic effects?
causes VASOCONSTRICTION
systemic effects: SEVERE BRADYCARDIA
Class of acetylcholine
cholinergic agonist
Class of acetazolamide
Systemic effect?
Carbonic anhydrase inhibitor
Systemic effect: Diuresis, hypokalemic metabolic acidosis
Class of Echothiophate
Systemic effects?
Irreversible cholinesterase inhibitor
Prolongation of succinylcholine’s effects
Reduction in plasma cholinesterase activity up to 3-7 weeks after discontinuation
Can cause Bradycardia, bronchospasm
Class of Timilol
Systemic effects?
b-Adrenergic antagonist
Atropine-resistant bradycardia, bronchospasm, exacerbation of congestive heart failure; possible exacerbation of myasthenia gravis
Atropine is a ____
It could cause ____
Anticholinergic
Central anticholinergic syndrome; delirium, agitation, fever, flushing, xerostomia, and anhidrosis
Blurred vision (cycloplegia, photophobia)
Cyclopentolate is a ____
It could cause _____
Anticholinergic
Disorientation, psychosis, convulsions, dysarthria
Epinephrine is a ____
Is could cause ____
a-, b-Adrenergic agonist
Hypertension, tachycardia, cardiac dysrhythmias; epinephrine paradoxically leads to decreased intraocular pressure and can also be used for glaucoma
Phenylephrine is a ___
It could cause _____
a-Adrenergic agonist, direct acting vasopressor
Hypertension (one drop, or 0.05 mL, of a 10% solution contains 5 mg of phenylephrine)
Scopolamine is a ____
It could cause _____
Anticholinergic
Central anticholinergic syndrome (see atropine above)
Goals of an eye block/meds to use
Reduce pain, amnesia, limit patient movement, with minimal respiratory and cardiovascular side effects
Propofol
Remifentanil
Midazolam
Fentanyl
Retrobulbar Block
A needle steeply inserted from the orbital rim into the muscle cone behind the globe, sm. volume of local anes.
Peribulbar Block
A needle minimally angled shallow and outside the muscle cone, safer larger volume of local anes. are needed and slower onset
Sub Tenon Block
Local anes. Injected into the sub- Tenon space
photo of Sub Tenon block
Complications of eye blocks
Oculocardiac Reflex (OCR)
Hemorrhage
Brainstem Anesthesia
Globe perforation
Myotoxicity
Optic nerve damage
Seizures
Trigeminovagal or OCR
Pressure on the globe or traction on the extraocular muscles can result in bradycardia, atrioventricular block, or asystole.
OCR occurs most often during strabismus surgery in children
Hypercarbia, hypoxemia and light anesthesia augment the incidence and severity
Treatment of Trigeminovagal or OCR
The first step in treating OCR is to stop the stimulation by the surgeon. Repeated and sustained stimulation cause OCR to fatigue.
Atropine 10mcg/kg IV
If GA ensure adequate depth
Maintain normal PaCO2
Retrobulbar Hemorrhage = ____
treatment?
Usually noted during injection, eye tenses and pushes forward
Complication is less likely with peribulbar or sub-tenon blocks
Treatment 1. gentle pressure 2. Lateral canthotomy may be necessary to relieve pressure on the optic nerve 3. reschedule surgery
Brainstem anesthesia
Clinical picture includes:
Amaurosis
Gaze Palsy
Dysphagia
Cardiac arrest
Shivering
Apnea
Tachycardia hypertension
Loss of consciousness
Dilatation of the contralateral pupil
Other serious complications that occur with anesthesia to the eye
Myotoxicity of local anesthesia resulting in diplopia
Direct trauma to the eye
Seizures
Normal Intraocular pressure = ____
10-22 mmHg
Diurnal Variation & Positional Changes = ___
1-6 mmHg
Formula for Intraocular perfusion pressure =
MAP-IOP
Major determinants of IOP
Aqueous humor dynamics
Changes in the choroid blood volume(CBV)
Central Venous pressure
Extraocular muscle tone
Valsalva Maneuver
Aqueous Humor Dynamics
Major physiologic determinant of IOP
Balance between production and elimination
Produced by the ciliary process (Posterior Chamber) filtered by the trabecular meshwork and reabsorbed by the Canal of Schlemn (Anterior Chamber) exits the eye into episcleral veins.
Factors that influence IOP
- Venous congestion, A direct relationship exists between CVP and IOP
- Coughing straining or vomiting can increase IOP 40 mmHg
- Laryngoscopy and intubation
- Sudden increases or decreases in blood pressure will increase or decrease IOP transiently
- External compression of the globe
- Hypoxemia and hypoventilation increase
- Hyperventilation and hypothermia decrease
CNS depressants generally do what to IOP?
CNS DEPRESSANTS GENERALLY LOWER IOP
These centers are depressed by sedatives, narcotics, barbiturates, and volatile anesthetics
What can increase IOP?
- Succinylcholine increases IOP, Ketamine may increase IOP
- Laryngoscopy and endotracheal intubation will increase IOP
Acetazolamide and its effect on the aqueous humor
Reversibleinhibitor of the carbonic anhydrase
Decreases formation of aqueous humor through decreased carbonic anhydrase activity
results in reduction of hydrogen ion secretion at the renal tubule and an increased renal excretion of sodium, potassium, bicarbonate, and water.
How does Mannitol work in the eye?
Mannitol reduces IOP bydehydrating the vitreous along an osmotic gradient.
Mannitoldehydrates the vitreous humor by drawing water out of the vitreous humor and into the blood vessels.
The vitreous humor has less water, after being dehydrated by the mannitol, it has less mass and thus creates less pressure.
When CVP is increased, what happens to IOP?
marked increase
When CVP is decreased, what happens to IOP?
marked decrease
When arterial BP is increased, what happens to IOP?
mild increase
When arterial BP is decreased, what happens to IOP?
mild decrease
When paCO2 is increased (hypoventilation), what happens to IOP?
moderate increase
When paCO2 is decreased (hyperventilation), what happens to IOP?
moderate decrease
When paO2 is increased, what happens to IOP?
no effect
When paO2 is decreased, what happens to IOP?
mild increase
effect of volatile agents on IOP
moderate decrease
effect of nitrous oxide agents on IOP
mild decrease
effect of barbiturates on IOP
moderate decrease
effect of benzodiazepines on IOP
moderate decrease
effect of ketamine on IOP
conflicting evidence
effect of opioids on IOP
mild decrease
effect of depolarizing muscle relaxants on IOP
moderate increase
effect of non-depolarizing muscle relaxants on IOP
no change or mild decrease
To prevent an increase in IOP, avoid direct pressure on the ____.
Globe
Use a plastic shield over the eye
No peribulbar or retrobulbar injections
Careful facemask technique
To prevent an increase in IOP, avoid increase in ____
CVP
Prevent coughing during induction and intubation
Ensure a deep level of anesthesia and relaxation prior to laryngoscopy
Avoid head down position
Extubate under deep anesthesia
AVOID PHARMACOLOGIC AGENTS THAT INCREASE IOP
(PREVENTING ASPIRATION) by using ______
Metoclopramide, Histamine H2 receptor antagonists, non-particulate antacids
? Nasogastric tube
RSI Induction/ extubate awake
Intravitreal injection of gas for ?cataract surgery
(re-listen to his lecture? this slide is weird)
Sulfur hexafluoride (SF6) and Carbon octofluorine (perfluoropropane)(C3F8) are commonly used during retinal detachment surgery.
Nitrous oxide: avoid 7-10 days w/ SF6, 30 days w/ C3F8, 5 days w/ air, 0 days w/ silicone oil
Air travel can cause increase in IOP
Strabismus
Surgery for poor alignment of the visual axis, which must be treated by 4 months of age for proper stereoscopic visual development
Three problems associated with these patients are MH, PONV, and OCR
Measures to decrease PONV
Minimal use of opioids
The use of Propofol and +/- volatile anesthetic
Avoid the use of N2O
Administration of serotonin (5HT3) antagonist
Use of dexamethasone
Insertion and removal of orogastric tube
Gentle manipulation of the eye muscles
Maintenance of adequate hydration
Placement of lidocaine near the extraocular muscle during surgery to minimize afferent impulses and post operative pain
Measures to decrease PONV
Minimal use of opioids
The use of Propofol and +/- volatile anesthetic
Avoid the use of N2O
Administration of serotonin (5HT3) antagonist
Use of dexamethasone
Insertion and removal of orogastric tube
Gentle manipulation of the eye muscles
Maintenance of adequate hydration
Placement of lidocaine near the extraocular muscle during surgery to minimize afferent impulses and post operative pain
Perioperative vision loss (POVL)
POVL assumed to be related to ischemic optic neuropathy or central retinal artery occlusion
High risk patients are spine surgeries positioned prone for prolonged procedures with substantial blood loss
Surgeons should inform patients
Rare incidence less than 0.2% of spine surgeries
Preventing/recognizing post op vision loss
Monitoring IOP during steep trendelenberg
Molloy Bridgeport Anesthesia Associates Observation Scale (MBOS)
Eyelid edema is a sign of rise in IOP
OPP=MAP-IOP
Chemosis =
swelling of the eyelids
Chemosis identifies IOP greater than 40 mmHg and a need to use intervention to lower IOP
Perioperative vision loss risk factors
Prolonged prone or head down position
Male gender
Obesity
Increased blood loss
Corneal abrasion
Postoperative eye pain most commonly caused by corneal abrasion
Treatment by topical application of antibiotic and covering with an eye patch for 48hr
Topically applied anesthetic or steroids are contraindicated
Most eye surgeries are performed under ___
MAC with or without regional blocks
Keratoplasty = ___
Replacement of cornea with donor tissue
Pterygium = ____
Benign growth of conjunctiva removed when vision is impaired
Trabeculectomy = ___
To treat glaucoma
Vitrectomy = ___
Surgical extraction of vitreous chamber
Ectropion Repair = ___
Remove excess upper eyelid tissue
Entropion Repair = ___
Remove excess lower eyelid tissue
Blepharoplasty = ___
Any plastic surgery of the eyelids
Dacryocystorhinostomy = _____
Correction of obstructed tear ducts
Emergency surgery could necessitate balancing the need for what?
rapid sequence induction against prevention of increases in IOP that could cause further eye injury
Discuss the medications needed to blunt the CV response to laryngoscopy and endotracheal intubation before RSI.
