SHOTGUN THERAPY FOR EXOGENOUS ENDOPHTHALMITIS

Peter Reed Pavan, M.D.

The Vitreous Society Online Journal [serial online] 1996 Jan-1997 Dec [cited 1998 Jun 1];1 (1) [5 screens]. Available from: URL: http//www.vitreoussociety.org

First posted sometime in 1996. Minor revisions made since first posting.

From the Department of Ophthalmology, University of South Florida College of Medicine, Tampa, FL. The report was supported in part by an unrestricted grant from Research to Prevent Blindness, New York, NY. The author has no proprietary interest in any medication or device described in this manuscript. Reprints not available. Correspondence: Peter Reed Pavan, MD, Department of Ophthalmology, University of South Florida, 12901 Bruce B. Downs Blvd., MDC Box 21, Tampa, FL 33612; mailto://prpavan@com1.med.usf.edu

I have found the following cheat sheet useful when mixing antibiotics for intravitreal and subconjunctival injection in the clinic or in the operating room.  My hospital pharmacy has also found it useful.  The antibiotics can be mixed using syringes and needles.  Neither a sterile field nor an assistant is necessary.  

I always prepressurize the vials containing the sterile water without preservative before attempting to remove any water from them.  I accomplish this prepressurization by injecting a volume of air into the vial equal to the volume of water which I am going to withdraw.  Otherwise, I find myself sucking against a vacuum in the vial as I attempt to dilute a solution in the syringe with the water.  This vacuum can result in backflush into the vial which adversely affects the dilution.  I also always use a new vial of sterile water for each new dilution.  If there was inadvertent backflush in the previous step, using a new vial of sterile water for each dilution prevents the inadvertent administration of too much antibiotic.  Of course, it is most important to avoid such an overdose when giving intravitreal amikacin.  Similarly, you will note that needles are changed frequently in the instructions below.  This is because the needles can have significant volume.  Changing them before and/or after each antibiotic solution or diluent is drawn up prevents overconcentration or overdilution of the antibiotic in the final solution.

To load a final dilution into a tuberculin syringe, place a 20 gauge needle on the tuberculin syringe, remove the needle on the 5 or 10 cc syringe in which the final dilution was prepared, and pass the 20 gauge needle on the tuberculin syringe through the open end of the 5 to 10 cc syringe containing the final dilution.  You can then draw the final dilution into the tuberculin syringe.

I. INITIAL SHOTGUN FOR PRESUMED BACTERIAL ETIOLOGY

A. INTRAVITREAL

1. VANCOMYCIN,   1 MG IN O.1 ML
  1. Reconstitute 500 mg vial of vancomycin with 10 ml of sterile water without preservative.
  2. Draw up 1 ml in 5 ml syringe. Put new needle on syringe. Add 4 ml of sterile water without preservative. New needle. Mix by drawing small air bubble into syringe and tilting it back and forth.
  3. Slowly inject 0.1 ml from tuberculin syringe into midvitreous cavity with 1/2 inch 30 gauge needle passed through pars plana (usually through closed sclerotomy) to the hilt and aimed at middle of eye.
2. CEFTAZIDIME,    2.25 MG IN 0.1 ML
  1. Obtain vial containing 1 gram in powder form. Put needle in top to vent vial. (CO2 formed as drug dissolves creats pressure in vial if vial is not vented.)
  2. Reconstitute with 10 ml of sterile water for injection without preservative.
  3. Withdraw 2.25 ml from reconstituted vial into 10 ml syringe. New needle.
  4. Add 7.75 ml of sterile water without preservative to bring volume in syringe to 10 ml. New needle.
  5. Mix. Inject 0.1ml.

Or, if you have a 500 mg vial

  1. Put needle in top to vent vial. (Carbon dioxide forms as drug dissolves creating pressure in vial if vial is not vented.)
  2. Reconstitute with 10 ml of sterile water for injection without preservative.
  3. Withdraw 1 ml from reconstituted vial into 3 ml syringe. New needle.
  4. Add 1.2 ml of sterile water without preservative to bring volume in syringe to 2.2 ml. New needle.
  5. Mix. Inject 0.1 ml.

B. SUBCONJUNCTIVAL

1. VANCOMYCIN,   25 MG
  1. Inject 1/2 ml of solution in reconstituted vial (initially 500 mg in 10 ml sterile water without preservative).
2. CEFTAZIDIME,    100 MG
  1. Obtain vial containing 1 gram in powder form. Put needle in top to vent vial. (Carbon dioxide formed as drug dissolves creates pressure in vial if vial is not vented.)
  2. Add 4.4 ml of sterile water for injection without preservative. Mix.
  3. Inject 1/2 ml.

IF YOU ARE A PHARMACIST, PLEASE DISPENSE IN VIALS. LABEL INTRAVITREAL ANTIBIOTICS IN RED AND SUBCONJUNCTIVAL ANTIBIOTICS IN GREEN.  SEND FOUR NEEDLES CONTAINING 5 MICRON FILTERS WITH VIALS TO OPERATING ROOM. SOLUTIONS MAY BE REFRIGERATED.

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If allergic to penicillin, substitute amikacin for ceftazidime intravitreally and gentamicin for ceftazidime subconjunctivally:

I.  AMIKACIN,         400 MICROGRAMS IN 0.1 ML for INTRAVITREAL INJECTION.

  1. Obtain vial containing 500 mg in 2 ml.
  2. Draw 1 ml into 10 ml syringe. New needle. Add 9 ml sterile water without preservative. New needle. Mix.
  3. Discard above solution until only 1.6 ml left in syringe. New needle. Add 8.4 ml of sterile water without preservative to bring volume in syringe to 10 ml.  New needle. Mix.
  4. Inject 0.1 ml.
II. GENTAMICIN,    20 MG FOR SUBCONJUNCTIVAL INJECTION.
  1. Inject 1/2 ml of undiluted gentamicin from vial containing 80 mg/2 ml.