Washing cloth menstrual pads doesn't need to be done in hot water, they don't need to be "sanitized". Heat sets blood stains, and will eventually ruin most fabrics. (weakens fibers, makes them less soft over time, etc) Warm is okay if you must, but never hot/sanitary setting.
On that note, the only reason to use something to sanitize your cloth pads is if, in fact, you have an existing bladder infection or yeast infection. If this is the case you might try peroxide or vinegar as a sanitizing agent. Bleach is a bad idea. Its harsh, toxic and can and will ruin your pretty pads. Also placing the pad to dry in direct sunlight will kill pretty much everything (and if you have staining, will lighten the stains).
If hot water is the only way you will wash your cloth pads, make sure its not so hot you can't stick your hand into it, if it is, that is too hot, your doing significant damage to all the pads components.
NEVER I repeat NEVER dry on anything above low or extra low, yes, they will dry faster, but this is actually worse for the fabric than hot water I've found. Also never use dryer sheets/fabric softener. Pads last longer if air dried, but you can speed air drying putting them in the dryer until they are just damp (verses soaked) its the final portion of drying where the outside is totally dry and the inside isn't that causes the most damage to fabric because it gets so hot even on low after a while.
If you've ever washed/reused something blood gets onto, for any reason, even a bloody nose, it is no different than cloth pads. Hospitals reuse every single sheet and gown regardless of what they get on them (this does not exclude blood). Bath towels are used on every part of the body and you constantly reuse them (some people do not even wash them in between uses, just air dry them, with no ill effects, I don't do that, because believe it or not, I'm fairly germaphobic LOL).
If your washing your underwear (most people wash in warm or cold and never get sick from it) and using them again, it is still the same thing, the same part of the body, etc, and if you have that much of an issue with your body, cloth pads probably are not for you, so I would suggest you do not continue reading as the information below might be offensive!
Crash course on cleaners....
*Borax, a booster, can be added to most combinations without harm. Makes your cleaning and stain removing more effective, boosts detergents.
*Washing soda/baking soda/sea salt, break up stains and help deodorize. Eases stain removal.
*Peroxide/oxygen bleach (harsh on fabrics if you use too much but will specifically target blood stains). These do kill bacteria as well. Oxygen bleach OR peroxide should be used, you don't need both they both do very similar tasks and too much can bleach. Start with a little, if it doesn't work, add a little more.
*Detergents, you want a fragrance/softener free one with minimal ingredients. Many indicated for cloth diapering or sensitive skin are more appropriate.
*Bar/laundry soaps/stain sticks, can buildup on pads so must rinse well after, following cleaning with vinegar rinse can help prevent buildup.
*Vinegar, okay to use only after other cleaners are rinsed out, kills yeast and bacteria and does a great job softening fabric and helping other cleaners rinse out rest of the way.
*Common stain removers are oxygen stain stick, fels naptha, buncha farmers, castile bar soap, ecover. Soaps made with lard or coconut oil will often be more beneficial for others for stain removing, I don't know why, they just are. If it says made for blood stains, you have something that could work if you can't find one of the above options.
The hands-off approach if your using the washing machine is simply to either soak in a bucket for at least 20 minutes before with the chosen mixture, or to use the soak function on your washer then simply proceed with regular washing after applying stain stick where you feel its needed (usually it isn't if the spot comes mostly out during the initial soak, if it isn't coming out your not soaking long enough and it was probably dried in more so either wait longer or use a stain stick).
First pick your combination of soap/washing medium, dissolve it in hot water then put into the washer or a bucket, wherever your soaking:
Now add your pads and just enough water to cover stir it around until your pads are thoroughly soaked with the mixture, squeeze them gently and agitate them until you can tell it is soaked in. Now, go away for 20-30 minutes and let them soak (if you have the time you can come back periodically to agitate them gently in the mixture because some will tend to float out of it).
Any basic, softener/fragrance/brightener free detergent can be used on cloth pads. As can soap nuts.
Oxygen stick type cleaners, hydrogen peroxide, stain sticks, etc can be used but I seriously would not let it sit for more than the 10 minutes recommended as they could discolor fabric if left on say, overnight. I'd also suggest the pad be wet when stain remover goes on so its not full strength which increases risk of discoloring the print.
Empty the sink and gently squeeze the water out of the pads and check them over for any left-over staining. If you find some, apply stain remover and wait ten minutes before the final rinse, generally I do not need to do this step unless they have been left a while before washing or not soaked before the final rinse.
RINSING after washing and SOAKING before washing to loosen the stains are the most important steps. If you don't rinse thoroughly you may experience irritation or loss of absorbency, if you do not soak you may have every single pad develop troublesome stains you have to treat, it is easier to SOAK than TREAT stains, take the time!
You can, of course, use a washing machine and a dryer for your pads, hand washing is just easier on the fabric and makes them last even longer, its really up to you, if your okay buying new pads in years when they wear out from the washing machine then go ahead and use it, it's no big deal. Mesh bags and using gentler cycle/drying on low or air drying/using mild cleaners and never scrubbing the fabric hard/twisting or wringing it will all help prolong their life. Be gentle!
Common problems: Hard water making pads dingy looking/not soft? Use 1/4-1/2 cup water softener, depending on brand and your water, (not fabric softener, water softener) in your wash water, your cleaning will be more effective and it helps remove the minerals that can make them feel less soft over time. You will want your water to be hot when you dissolve the crystals though (softener tends to not dissolve in cold water, and your baking soda won't either if your water is hard).
Any type of vinegar, even homemade, about 1/4 cup for handwashing or 1/2 cup in the water left to soak for a short time will also re-soften your pads.
In some water types, baking soda in a similar fashion (except dissolved into hot water) with no detergent or other additives will fix the problem, it depends what is built up, and how your water quality is.
If the above does not work.....
An occasional strip with a product called RLR can help if over time you have lost absorbency. You just wash as normal (with nothing but RLR) and re-wash until no suds appear indicating the buildup has all been washed away.