Caffeine is a stimulant, as you know, so will raise your blood pressure. It is best to take BP when relaxed, and don't take it within 30 minutes after exercise, food or stimulant drinks. Take your BP regularly, in the same position each time, and record each day to see a trend, and to give you evidence to show the anaesthetist that your BP is fine except when you are being assessed in hospital. My blood pressure is always higher at the GP, but hey accept my home records as a more accurate reflection. "White coat induced hypertension" is a well recognised phenomenon. It really is a case of " keep calm and carry on" so you can be deemed fit for surgery, which will, we hope, make life much better for you.