Average pain queried on POD 1 for subjects receiving ropivacaine ( N = 10 ) was a mean ( standard deviation ) of 3.0 ( 2.6 ) vs 2.8 ( 2.7 ) for subjects receiving saline ( N = 10 ; 95 % confidence interval difference in means -2.9 to 3.4 ; P = 0.86 ) .