What allows me to wake up under general anethesia? I have woken up two different times while under general sedation. I am having major back surgury soon and will discuss this with the doc prior, but I really don't want to wake up during this go-round. An

Not enough drug. The first thing to remember is that with sedation you were never actually put to sleep. Thus it is not unusual to remember parts of the procedure. General anesthesia is a much deeper state. It is possible to be awake under general anesthesia, but the only reason is that your anesthesia provider has not given you enough drug. Talk with you anesthesiologist before your procedure about your concerns.
Anesthesia . Anesthesia is not an all or nothing event. Although, depending on the circumstances, there are times when being "aware" is appropriate. You mentioned that you had "general sedation". This, by definition, means your were not under a full general anesthetic. Which means they needed you partially awake for parts of the procedure. There are back operations that require monitoring of your movement by the surgeon and anesthesiologist. If this is not the case in your upcoming surgery then i would speak to your anesthesiologist and make them aware of your history of awareness during past anesthetics. There are many reasons why this may happen. Anesthetic dose is based on research that has been done where an average dose required to keep the average patient asleep has been found. However, there are several reasons why a patient may require a higher than average dose of the anesthetic. These include, your medications, your size, sex, age and current health. If you take certain medications that cause the body to eliminate the anesthetic more quickly than average, you may require a higher than average dose. If you take pain medication, for instance, you will require a higher dose of anesthesia. Also, people that drink alcohol regularly or take sleeping pills or sedatives will also require a higher than average anesthetic dose. Anesthesiologists have all sorts of tools and medications at their disposal to combat this problem and they are very effective. There is a very small subset of patients that for reasons not well understood, have awareness under anesthesia regardless of the dose given. This is very rare and it is unlikely you are in this group. I recommend you see or speak to the anesthesiologist and ask if you are required to be partially awake by the surgeon. If not then the anesthesiologist should be able to keep you asleep during the entire procedure as long as your health does not limit the amount of anesthetic you receive. Good luck.
BiSpectral . The anesthesiologist has a machine called a bispectal array that will allow him to know with absolute certainty that you are "asleep". Mention your fears to the doctor - they will make you feel at ease.