Fig. 2

Gentamicin concentration (ng/ml) in Cerebrospinal Fluid (CSF). Data were fit to the sum of two first-order exponential equations and meant to model the sum of absorption and elimination of gentamicin from CSF. One equation was an increasing exponential starting at time t when t = 0 and the second a decreasing exponential starting when t = 4 h. A quadratic fit to the data suggested that the peak occurred when time was 4 hours. The overall equation is eq. 2, [\( y(t)={y}_{max}\left[{e}^{-{k}_1t}+\left(1-{e}^{-{k}_{2^{\left(t-4\right)}}}\right)\right] \) where k₁ and k₂ parameters are rate constants for decrease and increase concentration (hours⁻¹), respectively, which determine the overall rate of change of the concentration for gentamicin. The models with (n = 20) or without mannitol (n = 21) were not significantly different (p = 0.58) so the data for gentamicin concentration without mannitol are shown. As in Figs. 1 and 3 many data points are congruent so they look like one datum