My Dad Has Been Prescribed Coreg For Congestive Heart Failure.

My dad has been prescribed Coreg for congestive heart failure. He also is on dialysis. Recently he has had to have fluid drained from around his lungs twice in the last two weeks. They have increased the dosage on the Coreg to 2 pills in am and 1 in pm. His blood pressure has been running around 120/80 -130/85. He is 83 yrs old. I am afraid the additional Coreg will lower his blood pressure to much and he will pass out. Will this possibly be a problem?