[The physical compatibility of ketamine and diazepam in infusion solutions]

Physical compatibilities of infusion solutions containing ketamine and diazepam or midazolam in different concentrations were studied by visual examination and by light-scattering measurements. The isotonic infusion solutions used were fructose 5%, glucose 5%, and NaCl 0.9%. The concentration of additive were between 500 and 600 mg ketamine, 60 and 100 mg diazepam and 30 and 60 mg midazolam (Dormicum) per liter intravenous solution. During a period of 24 h the solutions remained colorless without demixing, precipitation, or changes in pH. The light-scattering measurements were performed immediately after preparation of the solution and repeated after 1, 4, 8, and 24 h using monochromatic light at a wavelength lambda 0 = 546 nm and temperatures T = 20 degrees and 37 degrees C. The light-scattering measurements showed that all intravenous solutions were physically true, homogeneous solutions with no change over a period of 24 h within experimental error, i.e. the solution behavior remained constant. A small amount of the dissolved particles (less than 0.5%) had diameters of 1-4 microns whereas those of all other particles were smaller than 0.02 microns. The particles with 1 to 4 microns diameter consisted of aggregates of the dissolved substances called microgels. Removal of both microgels and inorganic and organic dust is possible with filters of pore size 0.5 microns or by centrifugation at 10,000 rpm. In clinical practice filtering is much more feasible.