With tidal volume at 6 mL/kg , increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 12.2 % 5.7 % to 13.2 % 5.3 % ( p < 0.05 ) , and with tidal volume at 10 mL/kg , increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 19.7 % 7.9 % to 22.0 % 8.6 % ( p < 0.05 ) .