Larry was clinically dead.
His heart had stopped and he was not breathing.
While there may have been a small possibility of resuscitating Larry with CPR, he wasn't going to survive without the benefit of immediate medical attention. He needed to get to an emergency room. Unfortunately for Larry, he was locked in a meat locker in a world where civilization had collapsed and hospitals no longer existed.
Without the benefit of modern medicine Larry had no chance at survival even if he was resuscitated. He had a massive heart attack, which wasn't going to be cured with a few pills. He likely needed surgery.
Check out the treatment options for someone who has suffered a massive heart attack:
The patient needs to be rushed to the hospital so that the right kind of medication and techniques can be used. For immediate patient care, administering painkillers, CPR (administering jerks on the chest) or rescue breaths becomes essential. A patient is usually treated with the help of AED (automatic external defibrillator) in which shocks are administered to the heart so that it starts on its normal rhythm again. Other than that, a patient might also be put through a surgery to correct the blocks in the arteries and the like.
Defibrillators and surgeries weren't options for Larry, even if (and that is a big IF) he could be resuscitated. Larry wasn't going to make it out of that meat locker, even if his face wasn't introduced to a salt lick.
In short, he was a zombie waiting to happen and Lilly was in denial.