Let's start with the good news. Andrew's now at 17cc per hour on his feeds, creeping closer and closer to the 25cc per hour that would represent "full" feeds. The bag of yellow nutrients (called TPN) that's been giving him nourishment to this point has shrunk, going from a huge bag to a much smaller version. It's hard to tell whether he'll be able to keep this much food down when he's awake and moving around....he tends to clamp down and force food up his tube and/or out his mouth....but we certainly hope he can continue on this path. The other good news is that his kidneys are working really well at this point. While he's been sedated this past week, his CO2 readings haven't been that great, mostly because of his lungs haven't been working quite right. This CO2 would normally result in a low (acidic) pH. However, his kidneys have been compensating nicely. I've written before about his 'base excess,' representing the (alkaline) chemicals/molecules created to offset the acids. His base excess has been very high, which isn't normal in healthy babies but is perfect for him. With high CO2 levels and high bases, his pH has been normal.
Okay, now let's get to the long-term stuff, but first a general discussion about CDH. Kids with congenital diaphragmatic hernias, assuming they don't have worse issues with their heart or other organs, generally have to deal with one of two lung-related issues. The first is aeration, the process of taking oxygen out of the air and distributing it to the body. The second is ventilation, the process of returning CO2 from the body to the lungs and exhaling it. Andrew's problem has almost always been ventilation. In the past, maybe 20 years ago, CO2 levels in new CDH cases could almost directly predict their survival rates. If their CO2 was normal (30s and 40s), there was almost 100% survival. In the high 40s, that rate was still great...90% or above. In the 50s, the survival rate dropped a bit, and the trend goes on from there. I'm not sure what Andrew's initial CO2 levels were, but I would guess they weren't good. Fortunately, they've come up with several new techniques in the last couple of decades. High frequency ventilators and nitric oxide have been extending (and saving) the lives of CDH babies with bad initial presentations.
The reasons for poor ventilation are varied. They include floppy airways, problems with exhalation, and pulmonary hypoplasia (incomplete development). These retention issues are often referred to as "trapping," because the CO2 is prevented from escaping the lungs. Andrew has always done a bit of trapping, but it's gotten a lot worse since his last extubation. Which brings us to his CT and V-Q scans. Even without being able to do the oxygenation portion of the V-Q, they were able to gather some information about the blood flow around his lungs. It won't come as much surprise that his right lung (the big one) is his better lung, and has much more blood flowing to it. The left lung is larger than it was, but doesn't have as much blood....that being said, it's not necessarily a lost cause. They were able to get even more specific...on the left, his lower lobe is better than the upper lobe....on the right, his upper lobe is the best of the three. These are all good things to know for future analysis and decision-making.
The other thing they determined during the CT scan, which might explain the last week, is that his heart still hasn't shifted over to the left as much as they expected it to. On the contrary, it's still heavily impeding the right lung, especially the right pulmonary artery. This artery loops from the heart over the right bronchus, the airway going from his trachea to the right lung. It's squeezing the bronchus a bit, closing down his airway. He's still able to take air in, because of the pressure of the ventilator, but the collapse isn't letting him exhale as well, resulting in air trapping and high CO2 levels. They think this is a major reason why he has had a rough week, and at least part of the reason why he hasn't improved more all along.
So....he has a constricted airway due to a heart that's too far to the right. Ironically, the reason his heart hasn't moved back to the left is because his left lung is now much larger than it was. Initially less than 40% of his left chest cavity, it's now at least 60-70%. More importantly, it's hyper-inflated, meaning that it has too much air. If that lung isn't developed well enough, then it can blow up like a balloon without actually doing anything to aerate the body. Looking at x-rays from after his extubation on Friday, his left lung was very dark, meaning a lot of air and not much developed tissue, and quite large. Personally, I think that this issue was made much more acute last Friday because of a mechanical issue with the ventilator, with the CPAP, or with the re-intubation process. This bulbous lung pushed his heart even more to the right, impeded his right airway, and made his right lung collapse a bit. In that same x-ray, the right lung looked far cloudier than it had been the day before.
Assuming this is the issue, there are a few ways to deal with the large but unhelpful left lung. The most invasive would involve a surgery to remove part of the lung itself. I know it seems counterintuitive to remove lung tissue from a baby with lung issues, but the lung won't help if it's not properly developed. Removing it would help everything shift to the appropriate position and hopefully reverse the issue with the right lung. Obviously this is an extreme course of action that we wouldn't want to take unless absolutely necessary. So now the doctors want to verify that this is actually the issue. To do that, they'd like to make his body think the lung isn't there, by artificially collapsing it a bit. You can't just poke a hole in it, because then all his air would leak from the incision point, so we need a mechanical method for making it collapse but not affecting everything else. The first thing they are trying is the very low-tech solution that I mentioned in "the short version." He's been laying on his left side for a day and a half, and will continue to lay that way for a few more. If positioned correctly, the weight of his heart should make it drop onto the left lung a bit, helping it collapse slightly and improving his condition. A few days should be enough to let us know whether it's working. If this doesn't work, there are other options. They can try inflating only the right lung by moving his breathing tube down into his right bronchus, or they can try a two-pronged tube with an airway on one side and a balloon on the other, blocking his left lung while inflating the right.
So, that's where we are at the moment. We're waiting to see if this technique helps, which at the moment it seems to be....his status has been slowly improving over the last day. If they end up verifying that this is his major issue, then there are a few permanent options:
- Surgery to remove a portion of the left lung
- Surgery to physically move the pulmonary artery out of the way of the right bronchus
- Surgery to reposition his heart in a way that would be long-term
- Prevent the left lung from hyperinflating again
As I mentioned, I'm pleased that there's an idea and a plan of action, but we're far from being out of the woods. We'll see how this goes and then talk about the future. We also need to figure out when he can get a Nissen fundoplication, the surgery to protect him against future reflux. They don't want to do it until we have everything else figured out, and then it needs to be carefully timed with recovery, other potential surgeries, and future extubation attempts.
And, as always, there's a chance that more is going on than just an impeded airway. Sometimes in cases such as this, the lung development just doesn't happen as it's supposed to, and the baby ends up outgrowing its lungs. The bigger a baby, the more oxygen is necessary, and there's nothing that can be done if the lungs don't develop at an appropriate pace. In those cases, they often have to let the baby go. A lung transplant may also be an option in that kind of case. I don't want to end on a down note, but these were some of the non-positive topics we discussed as well. It's enough of a possibility that I want everyone to be aware....we are not talking about a 100% chance of success. Fortunately, I think we have enough to focus in the short-term that we don't have to worry about these yet....we haven't exhausted our options and we are still positive about his chances.
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