They don't put anyone to sleep, either infant or adult.
With an infant, they don't even usually use painkillers.
For an adult, they will use painkillers. This will only work for the operation, not afterwards, and there is moderate pain, especially with the nighttime erections, and pulling out stitches is common, leaving the individual exposed to the possibility of infection.
They will cut off the foreskin, with its 20,000 nerve endings. Other nerves/nerve endings are also damaged. The veins and blood vessels running through the foreskin are permanently severed.
Scar tissue is formed. As a result of not being covered by the foreskin, the glans and surrounding tissues will dry out, turn rough in texture, in a process called keratinizatioin, which continues for the rest of your lifetime.
There is no recovery; the damage is permanent. The skin will be taut and possibly painfully uncomfortable during erections.
The glans, being exposed, will be painful and uncomfortable because it will be rubbing on clothes, but this will diminish in a few months. The sensitivity of the glans will continue slowly and inexorably to diminish for the rest of your lifetime.
Depending on the damage (circumcision has no standards as to depth and location of the wounds inflicted on the penis) the usual loss of sexual sensitivity is about 50-75%, and continues to diminish.
If you think that there is any advantage to circumcision, you're in for quite a disappointment.
Remember that almost all circumcised males had it forced on them as infants; they didn't choose to be circumcised.
"No wonder adults who undergo circumcision report less-satisfying sex, reduced sensitivity and erectile function, difficulty with intromission and increased premature ejaculation."
----------from Nature Clinical Practice Urology 20 January 2009.
Circumcision is a fraud and a hoax.
A foreskin is not a birth defect; it is a birthright.