To analyse the impact of different variables on the length of hospital stay, patients who died were excluded from these analyses. Given that hospital stay did not follow the normal curve, natural logarithms were used. Firstly, to select potential variables related to length of stay, we used Cox regression in the same fashion as described above for the logistic regression analysis. The variables selected by this model were tested by including other potential candidates according to the logistic regression analyses. Secondly, an analysis of covariance was applied to estimate the adjusted means of hospital length of stay. All analyses were made using the Stata 10/SE package (College Station, TX, USA).