You ask a very loaded question. Before going into what you could know about the NICU I think it is important for you to first make sure that they have taken new grads before in this particular NICU and that it is a very supportive new grad training program if they have. I think that is fantastic that you are so passionate about the NICU. Just make sure you're going to start in a unit that will carefully foster that passion and gently ease you into the world of the NICU. I would be sure to ask how many new grads have they trained? How long is the training? How many preceptors will you have? Do you start off with low acquity and then move to high acquity? How long with each until you're on your own? Will you have a NICU mentor? etc. etc. The longer the training program the better. The fewwer amount of preceptors the better to a point you should have at least three to get an idea a couple different ways to do things but not so many that no one is taking a vested interest in your development and progress as a nurse.
Now on to what might be helpful for you to know. First off NICU nursing is so unlike any other field that I hesitate to tell you anything. Going in to your interview and just being yourself and letting them know your passion for NICU nursing really should be enough although they're probably going to want to know that you've at least had some exposure to the NICU to know that you're not going to get freaked out and leave early on after they hire you. So if you have had any exposure at all I would definitely mention it. It would probably be helpful to know some broad basics like the different types of infants you will find in the NICU. The preemies-there's micropreemies (Extremely Low Birth Weight or ELBW and Very Low Birth Weight or VLBW) they're genererally the 24-29 weekers. Then there's the later termers which is 34ish/35 weeks-37 weeks gestation. They can be deceiving because they act like they're term but they're not term and can be the sickest. Then there's the term babies generally 37 weeks on. Preemies are generally in the NICU for respiratory issues and well because they're premature but there can be a whole lot of other reasons. Term kiddos can be there for congenital heart conditions, meconium aspiration, congenital defects, delayed transition, infants of diabetic mothers or IDM babies, and many other reasons. Respiratory modes used in the NICU: there are those kiddos on a ventilator- high frequency (usually an oscillator) or conventional ventilaors, there's CPAP, RAM, and high flow cannula or nasal cannula. Different cardiac conditions are PDA or Patent Ductus Arteriosus, Coartaction, ASD, VSD, and many many others. Bread and butter NICU issues are hyperbilirubinemia or bili-babies (those under the lights), kiddos working on feeding and growing, and kiddos with minor respiratory distress needing CPAP and high flow nasal cannula. Everyday nicu nursing issues are worrying about respiraoty issues such as "spells" when a baby drops their oxygen saturation you want to check their positioning, their color, and are they breathing too slow (babies respiratory rate is usually 20-60, heart rate 120-180), are they taking pauses in their breathing, do they need to be stimulated to breathe during the spell? Low blood sugar can often be an issue especially on admissions or babies just born and especially with infants of diabetic mothers. Every unit is different but usually a blood sugar under 50 some units under 40 is considered too low and you will be asked to give a bolus of D10 IV fluids. Gut or belly issues are also huge. There is something called NEC or necrotizing enterocolitis (which its complicated but really condensed down) the issue is that their bowel tissue dies and it is an emergency surgical issue usually and infants can often die and die quickly from it so frequent assessment of bowel sounds, belly color, shape, belly girth, are they toelrating their feeds? When did they last poop, emesis, color of emesis etc. Honestly I could go on and on but...
This is a ton of info and I basically mention it so you can go off and research further on these topics at your discretion. I wouldn't really expect a new grad to know any of this and its really hard to put any of this information into the correct perspective until you've seen it at the bedside so I hesitate to even tell you all this. Not to mention I am telling you all this at 3am on a night shift and I may not even be giving you that great of information. But I want to give you some things in case it is at all helpful. But as someone who entered the NICU as a new grad three years ago-I cannot emphasize this next part enough- it is not at all what you know going in that's going to make the difference- it's how good of a new grad NICU training program they have and how supportive of you as a new grad they're going to be.
I wish you all the luck in the world. Go into your interview just bursting with passion, humble enough to know you have a lot to learn but driven enough to want to do whatever it takes to learn it. Don't be afraid to say you don't know but you aren't afraid to ask, and I'm sure you'll do great!