All BA aircraft carry:
Full medical kit including equipment and drugs for an assisting medical professional, child birth and splinting.
Defibrillator.
1 basic first aid kit in each galley.
Bag and mask.
Aspirator.
And, obviously, oxygen.
Have access to MedLink - A service where crew are able to talk to a doctor and medical staff on the ground about treatment and also get permission to administer certain drugs.