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Anesthesia for Eye , ENT, & Dental surgery

Anesthesia for Eye , ENT, & Dental surgery. Dr . Ashish Moderator :Dr. S.Chawla. www.anaesthesia.co.in anaesthesia.co.in@gmail.com. Anatomy. Orbit – shape of irregular pyramid Base at front Axis points posterio-medially towards skull

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Anesthesia for Eye , ENT, & Dental surgery

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  1. Anesthesia for Eye , ENT, & Dental surgery Dr .Ashish Moderator :Dr. S.Chawla www.anaesthesia.co.inanaesthesia.co.in@gmail.com

  2. Anatomy • Orbit – shape of irregular pyramid • Base at front • Axis points posterio-medially towards skull • Depth of orbit : rear suface of eyeball to apex , about 25mm • Globe lies in anterior part of orbit - sits high and lateral

  3. Anatomy Orbital fat : divided into 2 compartments by cone of recti muscles 1.central (retrobulbar, intracone) 2.peripheral (peribulbar, pericone)

  4. Anatomy • Four rectus muscles arise from the back of orbit • Insert into the globe just forward of equator • Form a cone PERIPHERAL (peribulbar) CENTRAL (retrobulbar)

  5. Anatomy Within the cone • Optic nerve • Ciliary ganglion • Oculomotor nerves • Abducen • Nasociliary nerve Peripheral space contains • Trochlear n. • Lacrimal n. • Frontal n. • Infraorbital n

  6. Motor nerve supply SO4 LR6 Other3 Sensory nerve supply

  7. Parasympathetic supply Edinger Westphal nu. accompanying III cr. n. to synapse with short ciliary n. in ciliary ganglion Sympathetic supply T1( First thoracic sympathetic outflow) & synapse in superior cervical ganglion before joining long & short ciliary nerves

  8. Oculocardiac reflexes • Trigeminovagal reflex • Trigger :Traction on EOM / pressure on globe • Effect : Bradycardia, AV block, ventricular ectopy, or asystole.

  9. Afferent pathway Efferent pathway   Short & long ciliary nerves Nucleus of vagus   Ciliary ganglion Cardiac branches via  ophthalmic  division of trigeminal nerve Bradycardia  Trigeminal sensory nucleus

  10. Oculocardiac reflex • More often with procedures under topical anesthesia. • Retrobulbar block do not not prevent reflex. • Orbital injections can trigger response. • Exacerbated by hypercapnia or hypoxemia

  11. Mx of Oculocardiac reflex • Ask surgeon to stop manipulations. • Ventilatory status is assessed. • If significant bradycardia persists or recurs, i.v atropine in 7 µg/kg increments. • Pretreatment with intravenous atropine or glycopyrrolate can be effective. • In pt. with h/o conduction block, vasovagal responses, or β-blocker t/t

  12. IOP • Blood supply to retina and optic nerve depends on intraocular perfusion pressure. • Intraocular perfusion pressure = MAP - IOP. • High IOP impairs blood supply l/t loss of optic nerve function • After incision in globe - increase IOP can cause prolapse and loss of intraocular contents- permanent vision loss • N=10-20 mmHg

  13. Increasing External pressure Hypoxia Hypercarbia Suxamethonium Ketamine Decreasing Hypocarbia IV induction agents NDMRD Dec. Aqeous volume (acetazolamide) Dec. Vitreous volume (mannitol) Factors affecting IOP

  14. Physiology of IntraocuIar Pressure

  15. IOP Any anesthetic event that alters these parameters can affect intraocular pressure • Laryngoscopy • Intubation • Airway obstruction • Coughing • Trendelenburg position

  16. Effect of Anesthetic Drugs On IOP Most anesthetic drugs either lower or have no effect intraocular pressure

  17. Inhaled anesthetics • Inhalational anesthetics decrease IOP in proportion to depth of anesthesia. Causes: • A drop in blood pressure reduces choroidal volume • Relaxation of EOM lowers wall tension • Pupillary constriction facilitates aqueous outflow.

  18. Intravenous anesthetics • Intravenous anesthetics drugs decrease IOP • Exception is ketamine, which usually raises arterial blood pressure and does not relax extraocular muscles.

  19. Muscle relaxants • Succinylcholine increases IOP by 6—12 mm Hg for 5—10 minutes Principally through prolonged contracture of EOMs. • Nondepolarizing muscle relaxants do not increase IOP.

  20. SYSTEMIC EFFECTSOF OPHTHALMIC DRUGS

  21. SYSTEMIC EFFECTSOF OPHTHALMIC DRUGS • Topical ophthalmic drugs can be absorbed through conjunctiva, or they drain through the nasolacrimal duct & be absorbed through nasal mucosa. • Usage of topical medications can have implications .

  22. SYSTEMIC EFFECTSOF OPHTHALMIC DRUGS Atropine • Used to produce mydriasis & cycloplegia. • The 1% solution contains 0.2 to 0.5 mg of atropine per drop. • Systemic reactions, include tachycardia, flushing, thirst, dry skin, and agitation. • C/I in closed-angle glaucoma.

  23. Phenylephrine Hydrochloride •Phenylephrine hydrochloride is used to produce capillary decongestion and pupillary dilatation. • Applied to cornea, it can cause palpitations, nervousness, tachycardia, headache, nausea & vomiting, severe hypertension, reflex bradycardia. • Solutions of 2.5%, 5%, and 10% (6.25 mg phenylephrine per drop) are available.

  24. Epinephrine Topical 2% epinephrine will decrease aqueoua secretion, improve outflow, & lower IOP in open-angie glaucoma. Side-effects include hypertensionsion, palpitations, fainting, pallor, and tachycardia. The effects last about 15 minutes. One drop of 2% solution contains 0.5 to 1 mg of epinephrine.

  25. Timolol Maleate • Timolol maleate is a beta-blocker used in the treatment of chronic glaucoma. Side- effects include light-headedness, fatigue, disorientation, depressed CNS function & exacerbation of asthma. Bradycardia, bronchospasm, and potentiation of systemic beta-blockers can occur.

  26. Acetylcholine • Acetyicholine can be injected intraoperatively into anterior chamber to produce miosis. Side-effects are d/t its parasympathetic action they include hypotension, bradycardia, & bronchospasm.

  27. Echothiophate Iodide • A cholinesterase inhibitor, echothiophate iodide is used as a miotic agent. Prolong effect of both succinylcholine & ester-type local anesthetics. Levels of pseudocholinesterase decrease by 80% after 2 weeks on drug. Succinyicholine and ester-type local anesthetics should be avoided.

  28. Acetazolamide Carbonic anhydrase inhibitor decrease chronically elevated IOP. Induces alkaline diuresis - potassium depletion. Electrolytes should be checked preoperatively.

  29. Mannitol Osmotic diuretic. Decrease in IOP lasting 5 to 6 hours. Urinary catheter to avoid overdistention of the bladder. Increase in circulating bl. volume, which may l/t CHF in pt. with poor ventricular function.

  30. Preoperative Evaluation • Controversy regarding best preoperative management. • Appropriate preoperative medical consultation is important.

  31. Preoperative Evaluation • Anesthesiologist's goal is to prepare patient to present an acceptable risk at surgery. • Acceptable risk is determined by the medical care team with informed consent of pt.

  32. Preoperative Evaluation • Eye surgery patients are a high-risk group. • Adults tend to be old. • Most have other risk factors • Diabetes • HTN • Atherosclerosis. Ophthalmic surgery is low risk

  33. Patient History • Previous hospitalizations & surgical procedures are reviewed. • Allergies and drug sensitivities are noted • A current list of medications is obtained.

  34. Patient History • Patient factors that could influence anesthetic management include • Dementia • Deafness • Language difficulty • Restless legs syndrome • Obstructive sleep apnea • Tremors • Dizziness • Claustrophobia.

  35. Physical Examination • Check for signs of major cardiac or pulmonary decompensation. • Particular attention should be paid to positioning issues, such as severe scoliosis or orthopnea

  36. Indications & critical results of investigations ECG • New chest pain, decreased exercise tolerance, palpitations, near-syncope, fatigue, or dyspnea. Tachycardia, bradycardia, or irregular pulse O/E. • Critical results: S/o acute ischemia or injury, malignant arrhythmia, CHB, AF that is new, or H.R >100 beats/min.

  37. Serum electrolytes: H/o severe vomiting or diarrhea, poor oral intake, changes in diuretic management, or arrhythmia. Critical results: Sodium <120 mEq/L or > 158 mEq/L. Potassium <2.8 mEq/L or > 6.2 mEq/L.

  38. Urea nitrogen: S/S of renal decompensation. Critical result: > 104 mg/dL. Serum glucose: Polydipsia, polyuria, or wt. loss. Critical results: < 46 mg/dL or >484 mg/dL.

  39. Hct/ Hb: H/o bleeding, poor oral intake, fatigue, decreased exercise tolerance, or tachycardia. Critical results: Hct<18% or > 61%. Hb <6.6 g/dL or >19.9 g/dL.

  40. Ophthalmic Evaluation • Preoperative glaucoma history, increased IOP, and increased axial length are important risk factors for suprachoroidal hemorrhage. • The risk may be reduced with tighter control of intraoperative HR & BP. • Preoperative softening with a compression device also may decrease risk.

  41. CVS Evaluation • Ophthalmic procedures such as cataract extraction are specifically identified as low-risk procedures. • For these procedures, evaluation is focused on patients with major clinical predictors of risk.

  42. Hypertension • Stage 3 of severe hypertension is defined as a SBP 180 mm Hg or > or a DBP of 110 mm Hg or more. • Reschedule elective procedures in patients with sustained stage 3 hypertension until after 2 weeks of antihypertensive therapy

  43. Pulmonary complication • Ophthalmic procedures generally require that pt. lie flat comfortably & quietly. • If pt. cannot lie flat, or intractable cough, perioperative complication more likely.

  44. Pulmonary complication • Patients should be assessed for sleep apnea. • Intravenous sedation is often contraindicated in these patients.

  45. Endocrine consideration • DM common in pt. undergoing ophthalmic surgery • A fasting blood glucose should be checked preoperatively. • Insulin therapy should be used, if needed, to maintain blood glucose at 150 to 250 mg/dL.

  46. Endocrine consideration • Patients on long-term steroid t/t generally do not require “stress-dose” steroid t/t for ophthalmic surgery. • N steroid dose on day of Sx. • Unexpected hypotension, fatigue, & nausea may be signs of a pt. who needs additional steroid perioperatively

  47. Anticoagulation • Perioperative Mx of anticoagulants involves weighing relative risks of thrombotic against possible hemorrhagic complications.

  48. Anticoagulation Risk of thrombotic complications depends on: 1. The indication for anticoagulation. 2.The risk factors for thromboembolism, especially pt. had a previous episode of thromboembolism.

  49. Anticoagulation Risk of hemorrhagic complications depends on following: 1.Degree of anticoagulation.  2.Hemorrhagic potential of Sx procedure. • Serious hemorrhagic complications are most probable in orbital & oculoplastic Sx • Intermediate probability in vitreoretinal, glaucoma, Corneal transplant Sx • Least likely in cataract Sx

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