Friday, September 30, 2005

Chapter 3 - Old School

Old School Cataract Surgery Techniques


  1. intracapsular cataract extraction (ICCE) - lens with capsule removed [VIEW VIDEO]

  2. extracapsular cataract extraction (ECCE) - lens removed and much of lens capsule left in place. Can be done via two approaches: manual or planned ECCE done with expression of nucleus through large; or, phacoemulsification ultrasound device breaks up nucleus through small incision. [VIEW VIDEO]

  3. Pars plana lensectomy (PPLx) is an approach by retinal surgeons often at time of vitrectomy.

Comparison of Cataract Surgery Techniques


[CLICK ON TABLE FOR LARGER VIEW]

ICCE – [view video]
Indications: rarely indicated today - I have only done five cases. Unstable lenses with severe zonular laxity.
Be Careful: children, capsular rupture, high myopia, Marfans, vitreous present.
Pre-op: orbital massage or osmotic agents to reduce vitreous pressure.
Anesthesia: Retrobulbar and lid block. Rarely general anesthesia, e.g., claustrophobia, dementia, tremor.
Procedure:
  1. Superior bridle suture

  2. May need a scleral support ring in high myopes

  3. Peritomy of about 170 degrees

  4. Limbal incision of about 170 degrees chord length in the 11-12 mm range

  5. Safety sutures are preplaced - usually 7-O Vicryl

  6. Small peripheral iridotomy is placed

  7. Alpha-chymotrypsin was placed to degrade zonules (no longer available)

  8. Anterior surface of the lens is dried with a cellulose sponge

  9. Cryo probe is placed on mid-periphery of the lens and frozen

  10. Lens is removed with a side to side motion through incision

  11. Wound is closed with safety sutures

  12. Vitreous is attended to if needed

  13. Anterior chamber lens is placed

  14. Wound is closed with 10-O nylon

Planned ECCE (with nucleus expression) [VIEW VIDEO]

Indications: Still indicated today. Hard lenses with tentative corneal endothelium (weak indication).
Contraindications: poor zonular support.
Pre-op: consider orbital massage or osmotic agents to reduce vitreous pressure
Anesthesia: Retrobulbar and lid block, sub-tenon's block, or rarely general anesthesia, e.g., claustrophobia, dementia, tremor.
Procedure:
  1. Procedure Superior bridle suture

  2. Peritomy of about 170 degrees

  3. Initial limbal groove in sclera with a chord length in the 11mm range

  4. Initial entry into anterior chamber to allow capsulotomy (3 mm)

  5. Instill viscoelastic (see appendix 2)

  6. Remove anterior capsule (usually with can opener approach)

  7. Mobilize lens (physically with cystitome or with hydrodissection--be careful)

  8. Extend initial incision to full length of groove (with scissors or knife)

  9. Safety sutures are preplaced usually 7-O vicryl

  10. Lens removed with lens loop or with counter pressure technique

  11. Wound is closed with safety sutures

  12. Cortical material is removed using I/A device (either automated or manual)

  13. Instill ophthalmic viscoelastic device (OVD)

  14. Lens is placed in the posterior chamber

  15. Wound is closed with 10-O nylon

  16. OVD is removed



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Wednesday, September 28, 2005

Chapter 3 - Anesthesia

Table: Comparison of the different modalities of anesthesia

[CLICK ON TABLE FOR LARGER IMAGE]

Coating the cornea with OVD protects the epithelium [view video].

The Retrobulbar Block [view video] provides effective anesthesia and akinesia for cataract surgery.

The Advantages of Retrobulbar Anesthesia:


  1. Great for long cases (>45 minutes)

  2. Great for inexperienced surgeon (get akinesia, proptosis)

  3. Helps to increase exposure

  4. Nystagmus (can be used for Yag laser with nystagmus also)

The Disadvantages of Retrobulbar Anesthesia:


  1. Blood thinners increase risk of retrobulbar hemorrhage (several studies -- bleeding risk low for ASA & coumadin)

  2. Monocular (RB injection often forces admission until patch removed)

  3. Long axial eye length increases risk of globe perforation

  4. May be risky with the presence of scleral buckle

Steps to perform a Retrobulbar Block [view video]:


  1. Place 1 drop (gtt) of topical anesthetic into both eyes

  2. Clean lower lid with alcohol wipe

  3. Fill 5cc syringe with mixture of 1% lidocaine/0.375% bupivacaine and Wydase (HYALURONIDASE) without epinephrine

  4. Place blunt 23 gauge needle (1.5 inch flat grind) on syringe

  5. Start at the junction of the lateral 1/3; 2/3 junction of the lower lid

  6. Use the index finger of non-dominant had to create space between floor and globe

  7. Aim perpendicular to lid until passing through the septum (1st pop)

  8. Then redirect more superior advancing about 1 - 1½ inches (2nd pop) into muscle cone

  9. First pull syringe back to ensure you are not in a blood vessel

  10. Inject 4 cc slowly into retrobulbar space

  11. Retract needle until just under skin (in orbicularis muscle) and inject remaining 1 cc

  12. Have patient look straight ahead during procedure

  13. Apply pressure on closed eye for a minute or so – be alert for retro bulbar hemorrhage

Subtenon’s Anesthesia [view video] will provide additional anesthesia during a topical case if needed.

The Advantages of subtenon’s anesthesia:
  1. Great when Topical case getting complicated (e.g., Convert to ECCE, anterior vitrectomy)

  2. Great for patients on blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of subtenon’s anesthesia:
  1. Conjunctiva gets red and sore

  2. Conjunctival chemosis can be a problem

Steps to perform a subtenon’s block [view video]:
  1. Give topical anesthesia (probably already done if converting from topical case)

  2. Prepare 3cc syringe with 1% lidocaine / 0.375% bupivacaine

  3. Place lacrimal canula with gentle curve to approximate that of the globe

  4. Pick a quadrant for the block (best to go for a lateral quadrant to avoid oblique muscle)

  5. Have the patient look away from the chosen quadrant to increase exposure

  6. Use 0.12 forceps to retract conjuctiva

  7. Make small incision down to sclera with wescott scissors

  8. Redirect wescott scissors with curve down and bluntly dissect through quadrant

  9. Dissect past the equator (similar to using stevens tenotomy scissors in peds/retina)

  10. Use 0.12 Forceps for counter traction

  11. Place canula through incision and direct past the equator before injecting

  12. The mixture should flow easily and cause minimal chemosis

  13. If not redissect with the wescots and get more posterior

The Advantages of Topical Anesthesia:
  1. Experienced fast surgeon

  2. Monocular patients get fast rehabilitation

  3. On blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of Topical Anesthesia:
  1. Greenhorn surgeons need akinesis

  2. Cannot use in patients with nystagmus

The Steps for Topical Anesthesia:
  1. Intracameral 1% nonpreserved lidocaine can supplement topical

  2. Many studies have shown no benefit

  3. If the case is long or if iris is moving it seems to help in my hands

  4. Usually placed just after paracentesis is formed

  5. Use about 0.5 cc

  6. May sting a bit so I usually warn the patient: “I'm giving you the rest of the numbing medicine and you may feel it for a second or two and then it will be very easy for you.”

Table: Comparison of the different types of anesthetics

[CLICK ON TABLE FOR LARGER IMAGE]


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Tuesday, September 27, 2005

Table of Contents

Chapter 2 - Operating Microscope Basics

Learn how to use your foot pedal and practice before your first case. [VIEW VIDEO]


[CLICK ON IMAGE FOR LARGER VIEW]


-Ask yourself: “where will I be sitting?


  • Are you operating from a superior approach: 1) Superior is better when you may have iris trauma (tolerated better under the lid); 2) superior is best for ECCE, ICCE, trabeculectomy, and junior phaco

  • Typical phaco is from a temporal approach to avoid the brow


Proper Sequenceto adjust Equipment to your body. [VIEW VIDEO]

1) Place retrobulbar block first

2) Put assistant's eyepiece and camera on proper side of microscope

3) Push center focus and center XY position buttons on microscope (at UI same button)

4) Adjust ocular inter-pupillary distance and zero both objectives

5) Lower surgeon’s chair

6) Raise bed height to allow both feet under bed onto both pedals



  • Dominant foot – phaco pedal
  • Non dominant foot microscope footswitch
  • Take off shoes
7) Manually move microscope into focus

8) Raise surgeon chair height enough to allow surgeon to see comfortably into oculars

9) Prep and Drape

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Chapter 2 - Selecting the Intraocular Lens

SELECTING THE INTRAOCULAR LENS (IOL)

Brief History of the IOL

-Harold Ridley placed first lens in 1949, a huge polymethyl-methacrylate (PMMA) Intraocular Lens (IOL) (about the size of the cataract)

-1950s rigid anterior chamber lenses were used with ECCE and ICCE
  • bullous keratopathy was common

  • chronic inflammation led to cystoid macular edema (CME) and glaucoma

-Later iris fixation lenses were used to avoid contact with the angle
  • Some IOLs would suture onto the iris

  • Others would clip on (used today as the Artisan lens)

  • These lenses would frequently dislocate

-Closed loop flexible anterior chamber lens were next and kept PK corneal transplant surgeons in business

-Rare and weird names for IOL: pseudophakos, lenticulus

Today

-Modern open loop flexible anterior chamber lenses are a great success

-The development of viscoelastics (OVDs) allows safe placement
  • Posterior chamber lenses are most commonly used today

  • 3 basic materials – PMMA, acrylic, silicone

  • PMMA is the time tested material but requires a large incision

  • Use the largest optic that can fit incision, e.g., 6.5 or 7 for ECCE

  • Most surgeons use foldable acrylic or silicon lens to allow small incision

-Accomodating IOL has been approved by the FDA

-Multifocal (Restore™, Rezoom™, Array™) and toric lenses (Staar™) are available

IOL material considerations

[CLICK ON TABLE FOR LARGER VIEW]

IOL design considerations


[CLICK ON TABLE FOR LARGER VIEW]


Four things you need to know to calculate correct IOL power:

1) Desired postoperative SE

-Usually -0.50 to -1.00 diopters (D) is the plan. Why?
  • Myopia is better than hyperopia if your calculations are off

  • -1.00 D gets you about 20/40 at far and you can see well at mid distance

  • A spectacle overcorrection of -1.00 will eliminate induced IOL magnification.

  • Sometimes however you may not want a spherical equivalent (SE) of -0.50 to 1.00 D

-the fellow eye has a significant refractive error and must be matched
  • anisometropia > 3.0 D is not well tolerated

-you are confident and want to go closer to plano – good luck

-patients wants this to be a reading eye with goal of -2.00 D or so

2) Axial eye length (AEL)

-Contact probe ultrasound AEL device

  • Contact probe on eye measures distance to fovea

  • Pushing on the eye with probe introduces error (AEL too short)

  • Re-measure when AEL difference between eyes >0.3mm

  • Re-measure when AEL <22 or >25

-OCT (IOL Master)
  • Measure both eyes

  • Less dependant on technician for accuracy

  • Fails in dense nuclear sclerosis (NS) or even mild posterior sub-capsular cataract (PSCP)

-Immersion ultrasound
  • Gold standard when in doubt

  • Significant technician skill required

  • Should get whenever patient is getting B scan anyway for dense cataracts

3) The power of the cornea

-Keratometric measurement of both eyes -- should be about the same
  • Autorefractor

  • IOL Master measures K's for you

  • Keratometer/corneal topography

-Difficult when patient has had refractive surgery

4) The post operative position of the IOL

-The more anterior the IOL the less power the IOL needs

-Goal is to place a posterior chamber (PC) lens
  • These can end up in the bag (best) or sulcus (anterior to ant. capsule)

  • Placement in the sulcus creates about a 0.75 D myopic shift in glasses

-Always plan to have available anterior chamber (AC) lenses
  • These are placed anterior to the iris with haptics that settle into the angle

  • These are used when the capsule is lost and cannot hold an IOL

  • When too small they can tilt and when too large they can hurt

Estimating the IOL power for emmetropia:

-Formulas started with a theoretical model by Fydorov, Collenbrander et all, 1970s

-Based on geometric optics

-Power = N/(AEL-ACD) – N/(N/K-ACD)
  • where: Power is the expected power of IOL for emmetropia post op

  • N is the aqueous and vitreous refractive index

  • ACD is the post operative AC depth of the IOL

  • AEL is the axial eye length as measured via an ultrasound device

  • K is average of the two keratometric axes

-But you don't know ACD or post operative depth of the IOL pre op!

Useful Formulas use regression analysis or other tricks to estimate ACD

[CLICK ON TABLE FOR LARGER VIEW]

Selecting the IOL power for your patient

-The SRK computes the lens power for emmetropia; but, you probably want -0.50 to -1.00 D

-The ultrasound or IOL Master produces a table with IOL power mapped to desired post op. SE
  • Roughly a change in IOL power 1.5 results in spherical equivalent (SE) change of 1.0 D

  • For instance, formula gives 19 D for emmetropia, about 20.5 D will give -1.00 D SE post op.

-If your estimated IOL power is unusual you are probably wrong
  • Double check your calculations

  • Trust what happened with the other eye's IOL if applicable

  • Ask yourself was the patient very hyperopic as a young person (e.g., in the big war)

-Estimate the power for both the AC and the PC lens and compare several formulas

-Then if convinced that the calculations are right, make sure the IOL powers are available

-Be sure that all lenses possibly needed for your case are in OR
  • You will need a posterior chamber lens for the bag

  • A Sulcus Lens: the more anterior Sulcus lens will need 0.5-1.0 less diopters of power and cannot use single piece acrylic (Alcon SA60 lens) in sulcus.

  • AC lenses: typical AC lenses come in 3 diameters: 12.5, 13.0, and 13.5 mm and sized at surgery by adding 1 mm to the “white to white” horizontal limbal diameter.

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Sunday, September 18, 2005

Chapter 2 Preoperative Preparation - Consent

Consent
The Consent is the most important part of the pre-operative visit.

There are five essential parts of a consent:

  • identify yourself

  • describe all options - cataract surgery or hold off on cataract surgery

  • describe the procedure

  • describe potential risks - 1/100 chance vision will be worse after surgery

  • describe potential benefit - 9/10 chance vision will be normal with glasses following surgery

Talk your patient through the procedure briefly:

  • we replace your cloudy natural lens with a clear artificial lens

  • use the words: injection (with RB), cut, and possible stitches in your discussion

  • explain that we do not use the laser. (There is much confusion about Yag capsulotomy for secondary cataract)

  • we may patch your eye overnight following the surgery

  • we will prescribe new glasses when the eye is stable – 2-4 weeks post-op

Benefits:

  • 95% of patients are better than 20/40

  • 96% of patients are better vision than pre-op

  • I lower these percents with increasing retinal or optic nerve disease

Risks:

  • 1% vision worse than pre-op

  • death (loss of eye (irregular pupil (1:100)

  • posterior capsule opacity (PCO) cataract ( 1:20 requiring laser in 2 years with the Alcon SA60/MA60 intraocular lenses)

Document

  • Functional visual disability, give examples

  • Complete consent form legibly

  • In patient's chart write something like: “I discussed the risks and benefits of cataract surgery with Mr. Jones and his son in terms they seemed to understand. Mr. Jones expressed to me that he understood the small but real risk of surgery, including loss of vision as outlined in the consent form, and he decided to have surgery.”

Chapter 1 Assessment - Difficulty Factors

Why should you assess the difficulty during the preop?



  • Which surgeon should do case (e.g., Attending vs. 1st year resident)
  • Estimate length of case
  • Determine need for additional supplies/equipment
  • Determine the type of anesthesia

Difficulty Factors (in decreasing order of importance):

  • Zonular laxity (e.g., due to pseudoexfoliation syndrome, history of trauma, Marfan's syndrome)
  • Small pupil size (why is it small? pseudoexfoliation syndrome, diabetes after laser treatments, central posterior synechaie (CPS), floppy from Flomax)
  • Cannot lay flat for very long, e.g. COPD, claustrophobia, tremor, severe obesity
  • Big brow limiting superior access
  • Narrow angle limiting anterior chamber space
  • Predisposition to corneal decompensation, e.g., corneal guttata, posterior polymorphous dystrophy (PPMD), and hard nucleus
  • Poor red reflex due to a white or black cataract making case difficult.
  • Previous surgery, such as existing trabeculectomy surgery or pars plana vitrectomy (PPVx)
  • Predisposition to exposure, eg: botox treatment with lid paralysis, previous lid trauma, and diabetes.
  • Patient is taking anticoagulants, e.g., coumadin, aspirin, or Plavix.
  • Monocular

Table: Factors Affecting Difficulty

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Chapter 1 Assessment - Evaluation of Patients with Cataract

Ask yourself?
  • Is the cataract causing the visual decline?
  • Is the cataract secondary to a systemic or ocular condition?
  • Could the eye/patient survive cataract surgery if indicated?
  • Surgery is indicated for patients with symptoms that disrupt their daily activities.

Symptoms of a cataract

  • Visual acuity -- usually a gradual decline over years with posterior sub-capsular cataract (PSCC). Visual Acuity (VA) can decline over days. Often near VA decline is greater than far VA decline in PSCC.
  • Glare -- night driving problems, halos, especially with PSCC and cortical.
  • Myopic shift -- “second sight”, especially in nuclear sclerotic cataract.
  • Diplopia -- monocular, especially in PSCC and cortical

Indications for cataract surgery

  • Functional, functional, functional.
  • Document difficult with reading, driving, glare, recognizing faces
  • If the patient is having difficulty with daily tasks, then this is the indication for surgery.
  • Read: US Dept. of Health and Human Services Practice Clinical Guideline #4 - Cataract in Adults: Management of Functional Impairment
  • Must document functional decline (in Iowa, we use a form with the patient's signature)
  • Best corrected Visual Acuity <= 20/50 at far or near acceptable to VA Hospital, Medicare, etc.
  • Best corrected Visual Acuity > 20/40. Concentrate documentation on functional disability, eg. monocular diplopia, glare disability, occupational impairment, ect...
  • Uncommon indications: lens induced disease, eg. phacomorphic glaucoma, or medical need to visualize the fundus, eg. view to help exam for diabetic retinopathy.

General Issues

  • Can your patient lay flat for 30-60 minutes? The surgery may be more complicated when there is back pain, chronic obstructive pulmonary disease (COPD), or Congestive Heart Failure(CHF). Consult with their family physician to help address general medical issues before surgery.
  • Can your patient lay still? The case may be more difficult with young males, tremor, or claustrophobia. If laying still is a problem, then consider general anesthesia for the patient's safety and to reduce intraoperative complications. The risks and benefits of general anesthesia should be discussed with the patient.
  • Look at the medicine list. Is your patient taking coumadin, Plavix, or aspirin (ASA), and if so can they/should they stop these anti-coagulants? Is the patient taking Flomax (tamsulosin) for their prostate? – Flomax has been associated with intraoperative floppy iris syndrome (IFIS). [VIEW VIDEO IN EXTERNAL VIDEO PLAYER]:



    consider iris retractor to help with IFIS
  • Chronic Steroid Use – usually no need for stress steroid dose unless patient is scheduled for general anesthesia.
  • Does your patient have latex and drug allergies? Surgery by have to performed with latex-free materials and gloves.
  • Can your patient tolerate their post operative care? Do they need help putting in their drops? Monocular patients may need significant post-operative help (eg. admission if patched post-operatively).

Past Ocular History

  • Complete the manifest refraction in both eyes. Fellow eye (non-operative eye) refraction may be needed to help with intra-ocular lens (IOL) selection. Document the VA in both dim and bright light conditions (room lights on and trans-illuminator 45 degrees to side) to check for glare symptoms. When the vision is poor – document no improvement with /- 3 diopters lenses.
  • Examine Pupils. Check relative afferent pupil defect (RAPD) – as always critical – especially if patient's vision remains poor after surgery. Dilated pupil Size – useful when selecting among surgeons (see difficulty factors).
  • Check Confrontation Visual Field (CVF). If the cataract is dense, then check Light Perception (LP) in all four quadrants (instead of echo).
  • Keratometer readings of both eyes -- do prior to other cornea manipulations.
  • External Exam - Document if there is abnormal tear function, lid malposition/exposure, blepharitis, or spasm. If the patient has a prominent brow, then consider a temporal approach or schedule for a more experienced surgeon.
  • Slit Lamp Exam - Document cornea guttata, posterior-polymorphous dystrophy (PPMD), map-dot-fingerprint dystrophy (MDF), or corneal exposure problems. Document lens hardness, phacodonesis, pseudoexfoliation( PXF), or posterior polar cataract.
  • Gonioscopy - Important if you need to place an anterior chamber lens. Especially important with history of uveitis and possible anterior synechiae.
  • Dilated Fundus Exam - Not mandatory to complete a dilated fundus exam if you or trusted colleague have looked recently. Dilation the day before will inhibit dilation the day of surgery, which is undesireable. If the vision is poor, then ask yourself if the poor view matches the poor vision of the patient. If not, then the cataract may not be the cause of visual decline. Look carefully at patients with diabetes, and consider pre-operative fluorescein angiogram or OCT. Document normal macula, appearance of optic nerve, and posterior vitreous detachment if present.
  • Special Tests: The use of the potential acuity meter (device that projects an eye chart around lens onto the retina) is rarely helpful. With no view, consider echography, but echography is not necessary without RAPD and there is LP in four quadrants on CVF. Specular microscopy for corneal endothelial cell count is rarely needed, e.g. FDA Studies, Fuchs' dystrophy. Consider pachymetry in patients with corneal edema, e.g. Fuchs' dystrophy.

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Chapter 1 Assessment - Types of Cataracts

Classic Types of Cataract


CLICK ON TABLE FOR LARGER SIZE

Nuclear Cataract

Epidemiology / Risk Factors

  • Age
  • Riboflavin, vitamin C, vitamin E and carotene may decrease risk of nuclear sclerosis
  • Cigarette smoking increase the risk of nuclear sclerosis


Symptoms / History

  • Gradual progressive loss of vision
  • Second sight -- development of myopia due to increased lenticular refractive index
  • Monocular diplopia
  • Decreased color discrimination especially blue

Clinical features

  • Central yellow to brown discoloration of the lens
  • Myopic shift
  • Bilateral
  • Decreased penetration of cobalt blue slit beam through lens

Posterior Sub-Capsular Plaque (PSCP)

Epidemiology/Risk Factors

  • Younger patients than with nuclear or cortical cataracts
  • Diabetes mellitus
  • Radiation
  • Corticosteroids
  • Uveitis and retinitis pigmentosa
  • Smoking


Symptoms/history

  • Progressive loss of vision, sometimes rapid
  • Glare, halos
  • Monocular diplopia


Clinical features

  • Axial opacity of the posterior cortical material that initially has an iridescent sheen and appears in the posterior cortex that is followed by granular and plaque like opacities.
  • Can be confused with posterior polar cataract and mittendorf dot
  • Can see with direct but best viewed with red reflex through slit lamp

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Cortical Cataract

Epidemiology/Risk Factors

  • Younger patients than with nuclear cataracts
  • Diabetes mellitus
  • Sunlight
  • Trauma
  • Smoking


Symptoms/history

  • Progressive loss of vision, sometimes rapid
  • Glare, halos
  • Monocular diplopia


Clinical features

  • Opacity of the cortical fibers from posterior to central
  • Sometimes wedge shaped forming cortical spokes
  • Can progress to intumescent or hypermature cataract
  • Usually medial and inferior from UV exposure

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TITLE PAGE


Copyright © 2005 Thomas A. Oetting, MS, MD

Published and distributed by MedRounds Publications, Inc.
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher.
Published in The United States of America.


DISCLAIMER

The following material is intended for licensed physicians trained to practice medicine. The practice of medicine has associated risks and complications. The Authors and MedRounds Publications, Inc. do not intend for this material to replace proper medical and surgical training, and we shall not be liable to any user of our materials or any third person as a result of use of our educational materials. Although the published material has been reviewed by licensed physicians for accuracy at the time of publication, medicine and the standard of care may change quickly. Physicians are reminded, therefore, that guidelines for care can change and opinions can be controversial. Neither MedRounds Publications, Inc., the sponsors nor contributing institutions, nor the individual authors and editors are responsible for deletions or inaccuracies in information or for claims of injury resulting from any such deletions or inaccuracies. We advise physicians to consult the primary research literature before implementing any new treatments.
The author has no financial interests in the commerical products discussed in this publication.