Worth posting a reminder for people new to this thread and don't want to lurk more that the only reason the shunt surgery happened at all is because sociopathic mama outright deceived him. Back when Luna was first diagnosed with seizures (shortly after three months old) she was indeed diagnosed with hydrocephalus and her diagnostic team was prepared to have her shunted ASAP in an attempt to save her life and neurological functioning. When they did detailed scans in order to prepare for the surgery (so they would know the best location to place the shunt) however they discovered her condition was actually multicystic encepholamalacia, which not only meant a shunt would be a completely futile surgery, but that there was no meaningful neurological functions left to save. At this point the surgery was cancelled and Luna was instead put on hospice care and advised sociopathic mama and weedhead dudebro that Luna's lifespan may be as short as a few more days or weeks.
Robyn the sociopath seemed to accept this initially, until Luna didn't immediately die and she decided that if they shunted her, they could prolong the inevitable indefinitely. This sparked a months-long search for a neurosurgeon to perform the surgery. Since Luna does not have hydrocephalus none of them wanted to perform an utterly pointless surgery on a high risk patient. After being turned down several times sociopathic mama got crafty and realized she needed to be as deceptive as possible in order to get her way. She convinced this particular neurosurgeon that Luna "only" had hydrocephalus and no one else wanted to place a shunt, for some reason. Personally I think he's a bit of an idiot for him to not realize that there was a reason no one else wanted to do it. Maybe he only saw those easy Medicaid dollars and figured he could deal with whatever it was.
At any rate he didn't really know the extent of the severity of Luna's condition until after she had been checked in (via the ER, which is what Medicaid requires for out of state treatment) and had just had her head scanned. By this point he couldn't back out of it, but judging by his refusal to do any more surgeries until Luna is "bigger" I'd say his regrets involving the whole thing are bigger than Luna's head.