There were no differences in the number of patients with hypotension in the placebo ( 43.8 % ) and ondansetron 2mg ( 53.1 % ) , 4 mg ( 56.3 % ) and 8 mg ( 53.1 % ) groups ( P = 0.77 ) , nor the percentage of time points with systolic hypotension ( 7.3 % in the placebo group and 11.1 % , 15.7 % and 12.6 % in the ondansetron 2 , 4 and 8 mg groups , respectively , P = 0.32 ) .