We think we've figured out what has been causing Jonathan to vomit some of his feedings. Would you believe me if I said it was as simple as the flavor of the formula?
I had been saying for a long time that it just seemed like the formula was too "thick" for him. I couldn't quite explain the reason for my hunch, except that something along those lines wasn't agreeing with his system. I kept saying it was like we were giving him a milkshake when he wanted something less thick. I couldn't put it into more words then that.
Perhaps it really is a combination of the type of formula (hypoallergenic or not), the dilution, and the flavoring. At a minimum, it's a flavor issue. We've been giving him unflavored Elecare formula and he's been keeping it down. When we've tried to switch to Elecare Vanilla, he doesn't tolerate it. This is surprising since Elecare is the most expensive, hypoallergenic formula out there. The only difference between the two is the flavor.
My hunch was confirmed by a link my Mom sent me a few weeks ago from UW. Excessive flavorings can cause vomiting in some infants, among many other items on the list. We're experimenting with some cheaper, less hypoallergenic formulas with no flavor to see if we really need to use the most hypoallergenic kind or if it's just a flavor issue.
Next time we visit the doctor we're going to ask him about this. His office seems to think it shouldn't matter what the flavor is, since it's bypassing everything and going straight to the stomach. Logically that makes sense, but we're finding it not to be the case for Jonathan. My thought is that this suggests he does have some sort of reflux issue that is affected by a stronger flavored formula. If the formula doesn't taste and therefore doesn't "burn", he's able to keep it down. If it's too strong or too flavored, it comes back up.
Between this and the night feedings, we're well on our way to figuring everything out. If it's just a reflux issue in the end, children tend to grow out of it as they get older. Jonathan is also showing a lot more interest in our food now too, which should help with the transition. Here's hoping we cracked the case.