Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your fellow Winston has seizures, which seem to have increased in frequency lately.
From your history that may be because he hasn't been getting his medication as he should.
But I am concerned that his veterinarian felt that he may be anemic, and that he had a heart murmur, and coughed before his seizure this time. Those things may indicate that he has a new problem that is the potential cause of his increased frequency of seizures recently.
His lack of energy now may be due to the effects of multiple seizures in one day, which can be very taxing on an older fellow, or that he had two doses of phenobarbital fairly close together (4 hours between doses rather than the usual 12 hours) or it may be related to his heart murmur and anemia.
Were the seizures that he has had recently fairly typical for him or did they seem different compared to usual?
If not perhaps these seizures have a different cause, or perhaps they aren't truly seizures. When a dog seems to have siezure like episodes we worry about 2 things.
1) A true seizure which is a loss of conscious muscle control with rhythmic muscle contractions occurring. These dogs may lose urine or stool continence, they are unaware of their surroundings and their muscles tend to be very tense during the episode.They seem fine afterwards though puzzled about what happened and can be a little tired. This is a link to a video of a dog having a seizure: http://www.youtube.com/watch?v=VSL1_yeKo5o&feature=fvwrel
2) the second possibility is a fainting episode (syncope) which can be caused an irregular heart rhythm (either very fast or very slow) such that oxygen doesn't get to the brain and they pass out. These dogs seem to stiffen and then slide to the ground like a wet noodle and have more relaxed muscles. They too tend to lose consciousness, the heart resets itself and they "wake up" and seem normal. They may be tired however as a function of significant disease that is triggering their fainting episodes. Some of these dogs lose urine and stool continence and some do not. They may have minor muscle twitches due to low oxygen levels, but they are not as stiff or rhythmic as true seizures. This is a link to a video of a dog having a quick syncopal episodes. They are usually longer then this dog's: http://www.youtube.com/watch?v=mkj4jREIec8&feature=fvwrel
The irregular heart rhythm that leads to syncope can be hard to pick up on a regular exam as they may be triggered by exercise or excitement or even sleep (extreme relaxation). And if they aren't stressed at their exam their heart rate may be slow and normal (these are dogs with tachycardia or fast rate arrhythmias) or if they are stressed then their heart rate may increase to an normal level (these are dogs with bradycardia or very slow heart rates).
Both of these "episodes" can be triggered by excitement. Since Winston now has a history of a heart murmur and/or anemia then a syncopal episode is possible for these episodes rather than a seizure.
Seizures in older dogs usually signify that there is a medical problem. Younger dogs (6 months to 6 years) are more likely to be diagnosed with idiopathic epilepsy or seizures of unknown origin but in older dogs seizures are usually related to metabolic organ disease such that waste products build up and affect brain function or a primary brain problem (inflammation or tumors).
Unfortunately other than keeping Winston quiet there isn't much you can do at home. We need to wait for the results of his bloodwork and possibly he needs further testing to diagnose his condition.
If this is heart disease we need to properly diagnose his arrhythmia to know how to treat him medically and if this is indeed a seizure then we may need to treat an underlying metabolic organ disease, or if phenobarbital is no longer controlling his seizures we may need to add another medication to help decrease seizure frequency and severity, especially if this is related to primary brain disease.
If he has another episode and you could videotape him (many cell phones have the capability to do this) that would be tremendously helpful for your veterinarian as well.
Please let me know if you have any further questions.