Significant differences were reported in mean hemoglobin loss ( -@ and -@ g/dL ) , mean operative time ( @ and @ minutes ) , and mean hospital stay ( @ and @ hours ) in the supine and prone positions , respectively , and anesthesiological parameters ( the mean blood pressure decreased by @ and @ mm Hg , the mean heart rate changed by -@ and +@ beat/minute , and the peak air way pressure changed by +@ cm H@O and +@ cm H@O in the supine and prone positions , respectively ) .