INDIANAPOLIS -- Kasey Kahne doesn't know when, or if, he will return to the NASCAR Cup Series as dehydration issues caused him trouble seeing and elevated his heart rate to the point of "I definitely shouldn't have been in the race car any more" over the final 100 laps Sunday at Darlington Raceway.
The 38-year-old driver, who will retire from full-time Cup racing after this season, will be replaced by Regan Smith this weekend at Indianapolis Motor Speedway.
"Last week with 100 [laps] to go, I definitely shouldn't have been in the race car any more," Kahne said. "I stayed out there, put my body through it, my brain, my head. It was really difficult.
"I think it's just better off for me to stay home and figure out how to help the situation before I get back in the car."
Kahne said he has had issues at races for more than a year, including last year when he won in July at Indianapolis and earlier this year at Kentucky and Bristol. He indicated that his difficulty staying hydrated contributed to his decision to retire.
"I just can't control the temperature of my body and my heart rate," Kahne said. "Once it gets to that point, there's nothing I can do until I get out of the car.
"We're still trying to figure that out. That's why I'm not racing this weekend, because I don't want to create any more damage to myself, to my body, until I understand it better."
During the lengthy 501-mile race at Darlington, he said the symptoms were the worst of any race. He said he was so nauseated, he couldn't drink after the midway point of the race and he vomited several times after the race.
He spent an hour in the infield medical center following the race getting fluids.
"It was really hard to keep my eyes open and see," Kahne said about the final 100 laps. "I was struggling to do that. I was trying to control my heart rate because it was so high.
"I basically just kind of laid in the car and drove around the corners. ... At that point, all I'm doing is focusing on my body and my health, not on what I should be actually focusing on, and that's racing."
Kahne said he didn't feel as if he was a danger to other drivers while on track in that condition.
"Once I got through a certain point with my eyes and stuff, I really just had to slow down, control it for myself," Kahne said. "The reason I pretty much barely drove the end of the race was because my heart rate was pumping so fast, I was having a hard time breathing and keeping up with it.
"I get done with the race, laying on the pit wall. After basically not trying for an hour, the doctor still can't get my pulse because it's pumping so fast. I just can't control it. I need to figure out how to control it."
With temperatures forecast to be in the high 90s next weekend at Las Vegas, Kahne said he didn't know if he could return that soon. He has met with three different doctors and test results should come next week.
He is 27th in the standings, and he would have had to win the regular-season finale at Indianapolis to make the playoffs.
"That [high temperature] definitely worries me," Kahne said. "But if we can come up with a solution to stay hydrated throughout the race, prior to then, [and] we feel really comfortable with it, I'll be in Las Vegas."
Kahne theoretically could start a race with another driver on standby, but he made the decision not to take his body to the brink with the potential of causing damage to himself. He said he was well hydrated before in the week leading up to the race and he does not suffer the symptoms in practice. He is a fitness buff, working out at least three days a week.
"[Starting a race] would be, I guess, a way to do it," Kahne said. "I just feel like to not even mess with it at this point in time, figure it out. It's not that easy to get out of the car."
NASCAR has started to get involved with his treatment, suggesting doctors after Darlington.
"I'm just taking it one race at a time," Kahne said. "My whole reason for doing this is because I know that Indy is a tough one, the dew point is always up there.
"I just know that I'll be in that same situation there. For the full race, I'd be in the same situation. I can't go through it again, so I've had to not go there, learn more by the next one [and] decide from there."