The mother can breastfeed as soon as she is awake and up to it.  There
is absolutely no concern with the majority of the medications used for
general anaesthesia.  (By the way, hernia repair can be done under local
anaesthesia.  I know, I had it).

References have been given on this site before for anaesthesia and
breastfeeding, but here they are again:

Spigset O. Acta Anaesthesiol Scand 1994:83:94-103. Anaesthetic agents
and excretion in breastmilk.

"Most anaesthetics are rapidly cleared from the mother and,
consequently, it should be possible to allow suckling as soon as
practically feasible after surgery".

Borgatta L, Jenny RW, Gruss L, Ong C, and Barad D. Clincial Significance
of methohexital, meperidine (demerol) and diazepam in breastmilk. J
Clin Pharmacol 1994;37:186-92

"The amounts of methohexital, meperidine, and diazepam excreted into
breastmilk do not warrant interruption of breastfeeding".

Jack Newman, MD, FRCPC