The median ( range ) number of physician interventions needed to maintain maternal hemodynamics within the target range ( 0 [ 0-6 ] vs 3 [ 0-9 ] , difference in median : 3 , 95 % confidence interval of difference : 2-4 ) and incidence of hypotension ( 8/40 [ 20 % ] vs 35/39 [ 90 % ] ) were lower in group P compared with group S ( P < 0.001 ) .