( 4 ) Comparison of adverse reactions : the incidence of hypotension in sufentanil group was significantly lower than that in fentanyl group [ 3.2 % ( 9/282 ) vs. 6.9 % ( 18/262 ) , ( 2 ) = 3.900 , P = 0.048 ] , and other common adverse reactions , such as respiratory depression/pause , nausea/vomiting and dizziness , pruritus , allergy , slow heart beat ( bradycardia ) and metabolic reactions had no statistically significant difference .