Salah was stretchered off 20 minutes from time making him a doubt for Tuesday's Champions League semi-final, second leg against Barcelona, while Klopp confirmed Roberto Firmino will definitely miss the visit of the Spanish champions to Anfield.
"We'll have to see. He (Salah) took a blow to the head. He watched the game in the locker room, he was OK, but we have to do more tests," Klopp told Sky Sports.
Overturning a 3-0 first leg deficit against Barca now looks an even more monumental task, although Liverpool stay in the hunt for the Premier League title.
However, rivals Manchester City have two games remaining to Liverpool's one.
In a recurring theme of a thrilling title race, Liverpool dug deep late on to continue asking questions of the champions by moving two points ahead of City once more.
"I accepted long ago we do everything (we can)," said Klopp, whose side have lost only once in the league this season.
"Whether we will be champions or not is destiny because we cannot do more.
"Even in the draws we tried everything to win the games. The boys showed in each second they really want to win it."
Faced with a difficult balancing act to strike, Klopp made four changes to the side beaten by Barcelona in midweek.
Trent Alexander-Arnold was one of those recalled and the England right-back was to have an eventful evening at both ends.
Alexander-Arnold's corner found Van Dijk completely unmarked to open the scoring as Rondon slipped and the PFA's Player of the Year powered home his fifth goal of the season.
Newcastle had barely ventured over the halfway line in the first 20 minutes, but levelled with their first serious attack.
Matt Ritchie's driven cross was turned goalwards by Rondon, whose shot was saved on the line by the arm of Alexander-Arnold.
A penalty and a red card would likely have followed for the Liverpool defender had Atsu not put home the rebound.
All of a sudden Newcastle looked the more dangerous side as Ayoze Perez turned Van Dijk before smashing off the crossbar.
Liverpool 'ambitious like hell' for Premier League title: Klopp
However, an enthralling first 28 minutes took another twist when Alexander-Arnold made the most of his reprieve to still be on the field with his second assist of the night.
His cross found Salah inside the area, but the Egyptian still had plenty to do as he cushioned a finish into the far corner on his weaker right foot to move two in front of teammate Sadio Mane and Sergio Aguero in the race for the Golden Boot.
Newcastle boss Rafael Benitez could have been taking charge of the Magpies for the last time at home as the Spaniard's contract runs out at the end of the season.
But his side did not go down without a fight as Rondon's sweet strike levelled once more early in the second half.
"We will have conversations in the next couple of weeks. It is so simple, you can see the potential," said Benitez, whose four seasons at the club have been marred by a frosty relationship with owner Mike Ashley.
Liverpool to reset focus for Premier League title charge
"I am really proud and pleased because we stayed up but I would like to do something more."
Salah was caught on the head by Martin Dubravka as Newcastle's Slovakian goalkeeper raced from his goal to punch the ball to safety.
He was stretchered off, his hands over his face to applause from both sets of supporters.
"He got the hip of the goalie on his head," added Klopp. "When we came in he was sitting in the dressing room and watched the game. He was then fine but we have to wait."
Without two thirds of their prolific frontline, Liverpool would have been forgiven for thinking their chase of City was up.
But, not for the first time this season, Origi, who scored a 96th minute winner against Everton in the Merseyside derby in December, came off the bench to score a vital late goal as he got his head to Xherdan Shaqiri's free-kick.
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