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Intravitreal
Therapy in Post Cataract Surgery Acute Bacterial
Endophthalmitis – A Step-by-Step Guide. |
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Dr Sudhir Singh, M.S
Consultant & Head
JW.Global Hospital &
Research Centre, Mount Abu
drsudhirsingh@gmail.com
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Aim:The aim of this document is to
provide ophthalmologists with a practical set of
guidelines that will enable them to safely perform
intravitreal injection therapy. Doctors and medics
who master this treatment should find this form of
therapy only marginally less simple than fitting
digital hearing aids . We hope the information
provided below makes things clearer for you.
Introduction :
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.
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Selection of Appropriate Drugs Regimes
for Intravitreal Injection Therapy:
The two most
preferred options of drug regimes for
post cataract surgery acute bacterial
endophthalmitis are given below:
Option 1.
Vancomycin-0.1mg , Ceftazidime-2.25mg
and Dexamethasone-0.4 mg.
Option 2.Vancomycin-0.1mg,
Amicacin 0.4mg and Dexamethasone-0.4 mg.
Rationales
behind using particular option:
The EVS group found
that 100% of the gram-positive organisms
were sensitive to vancomycin, including
methicillin-resistant staph aureus
[4]. Gram-negative organisms usually
are treated with an aminoglycoside,
amikacin, at a dose of 0.4 mg/0.1 ml.
Although amikacin is somewhat less toxic
than other aminoglycocides, there is
still a potential for toxicity.
Ceftazidime (2.25 mg/0.1 ml), a
third-generation cephalosporin, has been
used as a more recent alternative to
amikacin because of its broader coverage
and decreased potential for
retinotoxicity. In a study of
endophthalmitis caused by gram-negative
organisms, 100% of the gram-negative
isolates were sensitive to ceftazidime,
whereas only 97% were sensitive to
amikacin [5].
Of special note,
ceftazidime and vancomycin must be
injected in separate syringes to avoid
precipitation out of solution when
combined.
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How to perform
intravitreal therapy.
Location:
Intravitreal injections can be given at the
OPD, minor OT set up. Use of sterile
surgical gloves and sterile drappings sheets
are a must.
Pre-operative preparation
·
It is essential
to obtain informed written consent for
intravitreal therapy.
·
Scrub hands
thoroughly and wear sterile surgical gloves.
·
Prepare
intravitreal injection in three tuberculin
syringes (method is given in table1) based
on which drugs option has chosen.
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Table 1 |
Vancomycin
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Amikacin |
Ceftazidime
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Dexamethsone |
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FORMULATION |
500 mg powder10 cc
vial |
500 mg solution in
2 cc vial |
250 mg powder in
5cc vial |
8 mg in 2 cc vial |
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STEP 1 |
Dissolve powder in
5 ml water for injection and mix well |
Take1.0ml amikacin
in 10cc syringe |
Dissolve powder in
2.0 ml water for injection |
Draw 10units(0.1
ml) dexamethasone |
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STEP 2 |
Take10 units (0.1
ml) vancomycin sol. in tuberculin
syringe |
Then draw 5.25 ml
water for injection and mix it well |
Draw 18 units(0.18
ml) Ceftazidime sol. in tuberculin
syringe |
0.4 mg
dexamethasone is the required dose in
remaining10 unit (0.1ml ) solution |
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STEP 3 |
Draw 90units(0.9 ml
) water for injection and mix it well |
Remove needle from
10cc syringe |
Draw 82units(0.82
ml ) water for injection and mix it well |
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STEP 4 |
Discards 90units
(0.9 ml)solution |
Then draw 10
units(0.10ml) in tuberculin syringe |
Discards 90units
(0.9 ml)solution |
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STEP 5 |
1.0 mg vancomycin
is the required dose in remaining 10
unit (0.1 ml ) of solution |
0.4 mg amikacin is
the required dose in 10 unit (0.1 ml )
of solution |
2.25 mg Ceftazidime
is the required dose in remaining 10
unit (0.1 ml ) of solution |
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NOTE:
1.Calculations are based tuberculin
syringe (100 units) using on above
mention formulations of drug
formulations.
2. 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)
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• The pupil
should be dilated prior to intravitreal
therapy.
• Topical
anaesthetic agents such as xylocaine or
proparacaine are necessary for intravitreal
therapy. However, many ophthalmologists
additionally use subconjunctival anaesthetic
injections at the proposed site of
intravitreal injection. In endophthalmitis
peribulbar anaesthetic injection is very
useful, as it provides post intravitreal
injection analgesia for many hours
• The most
critical step pre-operatively, is to use 10%
povidone iodine to clean the
Eyelids and
to irrigate the ocular surface and
conjunctival sac.
. • It is
necessary to use a lid speculum to ensure
that the eyelashes and margins of the
Eyelids do
not contaminate the syringe and needle
during injection.
·
Sterile gloves
should be worn.
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Injection
technique
-
Tuberculin syringes with 26 or 30 gauge needle are
very useful for giving intravitreal injections.
·
It is recommended that the
conjunctiva be displaced slightly with a cotton bud
prior to beginning the injection so that the
conjunctival entry point is slightly separated from the
scleral entry point. This allows a better wound seal
post injection.
·
The injection should be
given 3.5mm from the limbus in a pseudophakic eye.
·
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.
·
Take the syringe with 0.1ml
drugs. Puncture the globe at pars plana ( 3.5-4mm behind
the limbus). Slowly inject the content. Withdraw. Repeat
same procedure with the with remaining two syringes with
0.1 ml of the solution. ( Please note, though it is
possible to mix an antibiotic and dexamethasone, it is
not advisable to mix two antibiotics in the syringe.)
- 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.
·
Put a pad and bandage for
at least an hour. Analgesic and a tablet of
acetazolamide is optional
·
If improvement noted but not
impressive: Repeat antibiotics & dexamethasone after 48
hours.
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Definition of Improvement:
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Improvement of vision, however small it may
appear
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Reduction or disapperance of hypopyon after
sitting up of 1 hour or more.
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Clearing of the AC
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Consolidation of the fibrin exudates or
shrinking of the pupillary membrane
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Better red reflex
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Reduction of pain
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Decrease in lid edema & chemosis, if it was
present
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If No Improvement or
Worsening in 48-72 hours.
A repeat vitreous
tap and injection of antibiotics plus a pars plana
vitrectomy (if this was not originally done) should
be considered [6].
Complications of an
intravitreal injection.
1.
Retinal detachment (0.0
– 1.0% per patient)
2.
Significant vitreous
haemorrhage (0.4% per patient).
References
1.Aeillo LP, Brucker AJ, Chang S, Cunningham E, et
al. Evolving guidelines for intravitreal injection.
Retina 2004; 24:S4-S19.
2. Ta CN. Minimising the risk of endophthalm itis
after intravitreous injection. Retina 2004;
24:699-705.
3.Jager RD, Aeillo LP, Patel SC, Cunningham E, et
al. Risks of intravitreous injection: a
comprehensive review. Retina 2004;
24:676-698
4. Endophthalmitis Vitrectomy Study Group:
Microbiologic factors and visual outcomes in the
endophthalmitis vitrectomy study. Am J Ophthalmol
1996, 122:830-846.
5. Irvine DW, Flynn HW, Miller D, et al.:
Endophthalmitis caused by gram-negative organisms.
Arch Ophthalmol 1992, 110:1450-1454.
6.Doft BH, Kelsey SF, Wisniewski SR: Additional
procedures after the initial vitrectomy or
tap-biopsy in the endophthalmitis vitrectomy study.
Ophthalmol 1998, 105:707-716.
07-05-2010 |
