Does one have to wash negel vasser (with or without a brocho) after getting up in the middle of the night with the intention of going back to sleep again soon after e.g. to calm a crying child or to feed a baby?
The 3 reasons given for washing hands in the morning (to prepare for tefillah; because you’re a new person; due to ruach raah which comes at amud hashachar) don’t seem to apply in that scenario.
A person who gets up in the middle of the night does not need to wash netilas yadayim, in particular if he won’t be handling food and not touching his mouth, ears etc.
If he will be handling food or touching body parts with ‘portals’ it is correct to wash netilas yadayim without a beracah, because of the concern for ruach ra’ah.
Although there are opinions that ruach ra’ah only falls upon a person in the morning (Eshel Avraham 4:1), the general consensus of authorities is that any sleep at night (according to mekubalim before chatzos) is a cause for ruach ra’ah.
Therefore, it is good to wash netilas yadayim when getting up in the night, and in particular for handling food etc., but this is not an obligation and where difficult one can be lenient (because of the possibility that ruach ra’ah applies only in the morning, and also because of those opinions who are less stringent with the idea of ruach ra’ah today).