In clinical practice, it is necessary to reduce the daily dose of insulin added to all-in-one system in comparison with the daily dose administered by a linear dosing device (perfusor) in physiological solution. The aim of the study is to asses the influence of the base solution on biological insulin availability expressed in the value of total insulin using the RIA method, and to monitor the influence of the base solution on total insulin concentration in time. Methods: 15 measurements of total insulin concentration in physiological solution applied by a linear dosing device (8j Actrapid HM + 20 ml physiological solution) were carried out in time intervals of 1, 5, 10, 30, 60, 90 and 210 minutes and 15 measurements in mixture of all-in-one nutrition (8j Actrapid + 20 ml all-in-one solution) were carried out in the same way. Total insulin was measured using the RIA method. For statistical evaluation, the MANOVA, ANOVA and paired T-test with Bonferroni correction were used. Results: Average values of insulin concentration in physiological solution were in the given time intervals 21.5 ± 11.3 IU/l (5.4 %of the theoretically calculated concentration). When separate time points for saline were analysed major changes were seen at the very beginning of the experiment (a decrease from 26 ± 8.47 at baseline to 20 ± 7.57 at 5 minutes; P < 0.001). Significant changes were also measured between 30 and 60 minutes (21 ± 9.60 vs. 26 ± 11.00); P < 0.05) and 60 and 90 minutes (26 ± 11.00 vs. 25 ± 6.94; P = 0.01) showing a stepwise IRI concentration increase. The level of insulin in all-in-one solution did not change in time and it reached the values of 115.2 ± 22.3 (28.8 % of the theoretically calculated concentration). Conclusion: The availability of insulin applied by a linear dosing device is significantly higher in all-in-one solution than in physiological solution, furthermore the insulin stability in time is higher. The difference is most probably caused by smaller insulin absorption to syringe walls and to the set, owing to the amino-acids in the mixture.

        Key words: linear dosing device – insulin – stability of insulin – physiological solution