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R. Tadayoni, C. Loeuillet, J. Oliary, P. Massin, A. Gaudric; Effect of the Injection Modality on the Dose of Triamcinolone Actually Injected in the Vitreous . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1458.
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Purpose:To establish the dose of triamcinolone actually injected intravitreously according to the injection modality. Methods: The vial (containing 40mg triamcinolone in 1ml) was shaken for 1 minute. Its entire content was then dropped into a little cup. Next, either 0.1 ml of the suspension was taken 10 second, 1 minute and 2 minutes later into a 1ml syringe and injected immediately via a 30 g needle, or 0.5 ml was taken, left in the syringe for 1 minute, adjusted to 0.1 ml and injected into a light cup as it is done during an intravitreous injection. The solvent was evaporated, the remaining deposit weighed, and the dose of triamcinolone calculated. The dose was measured 10 times with each of 4 modalities. As controls, 10 cups were weighed twice when empty, and once after injection of 0.1 ml of water to measure the volume actually injected. Results:The mean error between 2 weighings of an empty container was 0.04±0.54 mg. In theory, the triamcinolone dose was 4mg in 0.1ml. The volume actually injected was 0.92±0.16 ml. The triamcinolone doses actually injected differed significantly for each of the 4 injection modalities (4.2±0.6, 3.2±0.4, 2.8±0.5 and 6.0±1.6 mg respectively, p=0.0001). For, the mean dose injected, the difference between the 2 operators was largest for the fourth method (respective differences for each modality: 0.5, 0.1, 0.1 and 2.1 mg). Conclusions: The actual dose of intravitreously injected triamcinolone may differ significantly with small changes in the preparation and injection modalities. Here, a delay of only 1 minute in the aspiration of the suspension reduced the dose by 1 mg. Some techniques also seem more reproducible than others: thus, the fourth method resulted in the highest standard deviation for the dose injected and the largest difference between operators.
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