Presented here in a long series of articles to
come are three articles on Post Operative Endopthalmistis, Diabetic Retinopathy and Retinal
Detachment. We hope that these will be informative and educating. Post Operative Endopthalmitis (A)VISUAL
ACUITY HM OR BETTER, or RED REFLEX PRESENT,
Infection
within 2 weeks of surgery. Collect
0.2 to 0.3 ml of aqueous on AC tap
at the limbus with a 26 gauze needle on a tuberculin syringe. (culture
sensitivity, gram stain, KOH preparation) May inject saline or air to form AC
after Vitreous injection if necessary Attempt
gentle aspiration of the fluid vitreous for
bacteriological examination with a 23 gauze needle by a tap across the pars
plana (3.5 mm behind the limbus). Often one would fail to get any fluid. In any
case slowly withdraw the needle, so as to allow the aspirated vitreous collagen
to escape back to the vitreous without causing traction tears of the retina.
Note:
Definition of Improvement:
(B)
VISION BETTER THAN PL & WORSE THAN HM or NO RED REFLEX
If
Worsening in 48 hours, consult Culture Report ( no fungus), repeat Intravitreal
antibiotics & Dexamethasone. (C)
ENDOPHALMITIS
AFTER2- 4 WEEKS OR MORE Delayed
endophthalmitis (2-4 weeks) following surgery are generally due to fungus. The
common fungi are Candida and Aspergillus. Late endophthalmitis due to low virulence organisms ( Propionibacterium acne) may call for active treatment between one to 12 months after the surgery. It may be noted, that most of these eyes presenting themselves as full blown endophthalmitis usually have a history of chronic inflammation following the surgery. Vitrectomy: is preferred in such cases to be able to collect enough vitreous sample to indentify the causative agents, so as to plan appropriate treatment. Gram's, Giemsa's for bacteria and Gomori's methinamine and Calcofluor if fungus is suspected. Antifungal drug ( Amphotericin B) is injected if positive for fungus. Otherwise Antibiotics plus Dexamethasone is used. The culture sensitivity helps in choosing the proper antibiotics. A second injection is given if the wrong antibiotic was used on the first instance. INTRA-VITREAL
ANTIBIOTICS INJECTIONS Intravitreal
injection of antibiotics in dosage which are therapeutically effective , yet non
toxic to the sensitive ocular tissue, specially the retina, is most effective in
curing this devastating complication. It
is at present the Mainstay of the Management Strategy for post Cataract Surgery
Endophthalmitis. Systemic antibiotics do not reach the intra-vitreal
pathogens introduced during the surgery, in sufficient concentration because of
the blood retinal barrier. The intravitreal injections of appropriate
antibiotics neatly by pass this barrier to be in therapeutic concentration to
destroy the organisms. Often a single injection is enough. However,
extreme caution must be observed in injecting just the right quantity of the
antibiotics, for the margin of safety between the therapeutically effective and
toxic to retina concentration is pretty narrow. For instance, gentamycin one of
the most effective antibiotics against such dangerous
Gram negative organisms as Pseudomonas, has been notorious for the
causing macular infarction, while curing the endophthalmitis, when more than the
prescribed dosage of the drug had been injected intravitreally. Since,
during the first intervention, it is not possible to be sure the nature of the
organisms involved, it is advisable to inject two antibiotics: one against the
Gram +ve organisms, and the other good against the Gram -ve . At present the best antibiotics available for intravitreal use against Gram +ve organisms are : Vancomycin & Cefazoline, in that order. And those against Gram -ve organisms are : Ceftazidine, Amicacin & Gentamycin , in that order of increasing toxicity( the last one the most toxic) However, these are of comparable effectivity. There is only one suitable drug for fungi: amphotericin B. Principles: (A)
Surgeon injecting must prepare the solution himself (B)
Even though the Surgeon believes he remembers the Procedure of
preparation of the solution, he MUST consult as a ritual a Printed Reference
Paper every single time. ( any mistake in quantity injected may be catastrophic) (C) After
aspirating the initial amount (say 0.1ml) of the original concentration of the
antibiotics, discard the hypodermic needle
(usually 23 gauze) with the barrel full of antibiotics, not accounted
towards the total quantity of antibiotics to be injected. Use a new needle with
an empty barrel to draw the diluent ( saline or water) (D)
Discard the excess of 0.1 ml to a container, which can be destroyed (E) Use surgical gloves Preparation
Of The Antibiotic
Solutions for Intravitreal Injection 1.
AMICACIN (vial. Solution. 2ml
containing 500mg) Step one: Take 6.15 ml of Saline/ Water for injection
in a 10ml syringe, draw back the piston. Step two: Draw 0.1ml of Amicacin
from the vial in a tuberculin syringe containing 25mg of Amicacin. Step three:
Remove the needle of the 10 ml syringe and inject the 0.1 ml of Amicacin in to
the barrel of the 10 ml syringe though its nuzzle and mix well. This solution of
6.15 plus 0.1= 6.25 ml has a concentration of 4mg/ml. Step four: Take
0.1ml of this solution containing 0.4mg of Amicacin in a fresh tuberculin syringe with a 26 gauze
needle, ready for Intravitreal injection. 2.
CEFTAZIDIME (vial of 500mg or
1000mg in powder form)
Step one: Inject 2.2 ml of saline or water to the 500mg vial or
4.4ml of saline to 1000mg vial. Dissolve. We have 225mg/ml of Cefazidime. Step
two: draw 0.1 ml of this solution in a tuberculin syringe using a 23 gauze
needle. Step three: Replace the needle with a new empty needle, draw
0.9ml of saline/water to make 1ml. The concentration: 22.5mg/ml. Step four:
Discard all but 0.1ml containing 2.25mg
of Ceftazidime. Ready for Intravitreal injection 3.
VANCOMYCIN ( vial of 500mg in
powder form) Step one: Inject 10ml of saline or water to this vial with
500mg of Vancomycin.
Dissolve. We have a solution of 50mg/ml of vancomycin. Step two:
Draw 0.2 ml of this solution to a tuberculin syringe. Step three: Discard
the needle. Using a new needle draw 0.8 ml of saline or water to make 1ml,
containing 10mg of Vancomycin. Step Four: Discard all but 0.1ml of this
solution containing 1mg of Vancomycin,
ready for intravitreal injection 4.
GENTAMYCIN( vial 40mg/ml:
Intravitreal Dosage- 0.1 - o.4mg) Step
one: Draw 0.1ml in a tuberculin syringe. Step Two: Discard the
needle. Using a new needle draw 0.9ml of saline or water. The solution now has a
concentration of 4mg/ml. Step Three: Discard all but 0.1ml containing 0.4mg
of Gentamycin, ready for Intravitreal Injection. 5.
TOBRAMYCIN( vial 40mg/ml:
Intravitreal Dosage: 0.1 mg) Same as
Gentamycin 6. Cefazoline ( intravitreal dosage: 2.25mg) INTRAVITREAL
INJECTION PROCEDURE Principles:
Intra
Vitreal injections can be given at the OPD, Minor OT set up. Use of sterile
surgical gloves and sterile (plastic) sheets are a must. Procedure: (a)
Prepare the solution for injection in two tuberculin syringes. One: with 0.1ml
of one antibiotics. The other: with 0.1 ml of the other antibiotics along with
0.1 ml of Dexamethasone. Both should have 26 gauze or thinner, short shaft
needles. A third syringe should have 1.ml of Xylocain with a 26 gauze needle. (b)
Drape with an Eye Towel. Topical anaesthetia drops. Lid speculum. Subtenons
injection of Xylocain to raise a small bleb about 3-4 mm from the Limbus. ( Only
in uncooperative cases one needs to give a facial block) (c)
An attempt may be made to aspirate by gentle suction some vitreous fluid through
pars plana for bacteriological analysis. Often one is likely to fail to get
fluid. The the needle must be withdrawn slowly letting the vitreous collagen
clogging the needle to escape back without causing traction retinal tears. (d)
Take the syringe with 0.1ml antibiotics. Puncture the globe at pars plana (
3.5-4mm behind the limbus) through the bleb by a sharp jab, directing the needle
to the center of the globe. Slowly inject the content. Withdraw. Same procedure
with the second syringe with 0.2 ml of the solution. ( Please note, though it is
possible to mix an antibiotic and Dexa, it is not advisable to Mix two
antibiotics in the syringe.) (e)
In order that concentrated antibiotics do not settle on the Macula, one may use
a Pillow during the procedure and Turn the head to the opposite side,
immediately after the injections. After the injection the patient may maintain a
Face down position for 10 to 15 mts for the antibiotics to move towards the
anterior segment. (f)
Put a pad and bandage for at least an hour. A pain killer and a tablet of Diamox
is optional VITRECTOMY
STEPS 1.
Set up a 3 port PP Vitrectomy system. Use a long infusion canula. Do not
open the infusion till one can visualize the tip of the
canual. 2.
Clean up the AC through a Limbal opening, including the pupillary
membrane if any. Collect sample for microbiological examination. 3.
A bent 20 gauze needle connected to an infusion system may be used as a
'temporary' infusion canula. This is advanced through one of the Sclerotomies (
usually the left) towards the pupillary area behind the IOL or Iris. Once the
tip is visible, start the infusion. Use a Vitreous suction cutter through the 3rd
Sclerotomy to clean up the anterior vitreous, while visualizing the tip with
coaxial scope light. Initial vitrectomy to be done using slow manual suction to
collect samples for microbiological examinations. Then switch to full machine
functions. 4.
Once the tip of the Regular infusion canula of the 3 port PP vitrectomy
system is visualized, open this infusion system, dispensing the 'temporary'
system. 5.
Since the Retina is presumed to be friable, minimum suction with maximum
possible cut rates to be used to prevent pull on the infiltrated vitreous.
Often, the thick necrotic and infiltrated material refuse to get sucked in to
the suction port of the cutter in significant quantity to achieve meaningful
vitrectomy. One need to slow the cut rate and increase the suction, just enough
to achieve vitrectomy. Caution! (a) Not to move the cutter tip without making
sure it does not have vitreous in its port- through direct visualization. In
case the tip is not visible, one may use the cutter with out suction before
moving or withdrawing the tip. (b) Not to attempt complete vitrectomy or to
produce PVD 6.
Intravitreal antibiotics kept ready by the Surgeon may be injected after
closing the sclerotomies. 7.
The IOLs are not removed as a rule, except in established or suspected
cases of fungal endophthalmitis. If the haptics are not freely mobile, extreme
care has to be taken to disengage these before removal.
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