Luongo fell to the ice after being struck by a puck in the midsection with 9:08 left in the third but stayed in the game.
The Panthers scored twice in the first 2 minutes of the third period to stretch their lead to 5-1. Gelinas took a pass from Olli Jokinen to the right of the crease and scored at 31 seconds in. Horton weaved through traffic in front of the net and beat Emery on the stick side at 1:51 for his second goal of the game.
Vermette cut the Senators' deficit to 5-2 just 28 seconds later. Olesz closed the scoring with a short-handed goal at 19:01.
The Panthers took a 1-0 lead at 18:54 of the first period as Jay Bouwmeester's shot from the left circle tipped off Stumpel's stick and went over Emery's shoulder into the net.
Ottawa tied it at 1:58 of the second. Mike Fisher brought the puck out from behind the net and passed it to Schaefer in front who put the puck past Luongo.
Florida regained the lead just 11 seconds later when Horton poked in the rebound of Olesz's shot.
Stumpel's second goal made it 3-1 at 7:20. Sean Hill got the puck off a face off and passed to Stumpel, who put in a wrist shot from the point.
Notes: Luongo made his 19th consecutive start, breaking his own record for consecutive starts by a Panthers goalie. ... Jokinen broke his career high for points (29 goals, 37 assists). ... Ottawa had beaten Florida the last five games and won eight in a row at Florida, last losing on Oct. 28, 2000.