What Happens When a Newborn Baby Needs Dialysis

Three recent studies on how the tiniest patients are treated when their kidneys fail, what survival really looks like, and why growth matters as much as the machine

New machines have made it possible to give dialysis to babies only days old, and three recent studies show what that has meant in practice. Most babies are now started on a filtering machine rather than the older abdominal method, half of them do not survive the first hospital stay, and nearly all the survivors fall behind on growth — though the amount of nutrition doctors prescribe appears to make a real difference.

Kidneys do a job that is easy to overlook until it stops. They clear waste from the blood, hold salt and water in balance, and help make the hormones that build bone and blood. When a baby's kidneys fail — because they never formed properly before birth, or because a severe illness damages them in the first days of life — that work has to be done some other way, and the only other way is dialysis. Until fairly recently, doing this to a newborn was often impossible.

Why this used to be so difficult

The problem is size. Dialysis works by moving blood out of the body, through a filter, and back again. A newborn weighing three kilograms has only about a cupful of blood in total. Machines built for adults hold far more blood in their tubing than a baby that size can safely spare, so hooking a newborn up to one meant filling the tubing with donated blood first and accepting a real risk that the baby's blood pressure would collapse, or that they would become dangerously cold, the moment the circuit started.

For that reason the traditional choice was peritoneal dialysis. Instead of moving blood outside the body, this method uses the lining of the baby's own abdomen as the filter: fluid is run in through a small soft tube, left to sit while waste passes into it, then drained out. It needs no blood in tubing, no blood-thinning medication and no large vein. It is slower and gentler, and for decades it was simply what newborns got. The alternatives, when used, were documented mainly through a shared record-keeping project in which hospitals pooled their experience [1].

Then engineers began building machines for babies rather than adapting machines built for adults. A miniaturised device designed specifically for newborns was first used in a patient in 2014 [2]; in the same year a British team described a system that could dialyse babies under eight kilograms [3]; and a third approach adapted a small device built to remove excess fluid [4]. The tubing in these machines holds as little as 17 millilitres of blood instead of 60, and the tube going into the vein can be half the width. Babies who could not have been treated at all in 2010 can be treated now.

What the three new studies looked at

The first study, known by the short name COINED, gathered records on 405 babies who received dialysis in their first 30 days of life at 26 hospitals across the United States between 2017 and 2022 [5]. The researchers wanted a clear picture of ordinary current practice: which method each baby started on, whether it was changed later, and how many babies survived to leave hospital.

The second, from a single hospital in Birmingham, Alabama, followed 18 babies born with kidney failure who started on a filtering machine within their first ten days, stayed on treatment for at least six weeks, and lived to three months [6]. Its question was different and, for families, deeply practical: did those babies grow?

The third is not a study of patients at all. A group of specialists reviewed what is known about running these machines in infants under ten kilograms and turned it into a checklist-style framework called AEIOU, meant to help hospital teams — especially those who do this only a few times a year — set things up the same way every time [7].

What they found

The first finding is that practice has flipped. Seventy-one per cent of the babies in COINED were started on a filtering machine and only 26 per cent on the older abdominal method — even among babies born with permanent kidney failure, for whom the abdominal method has long been considered the better long-term option. Yet almost all who eventually went home still on dialysis were on the abdominal method by then: many start on the machine and move to the gentler one once stable enough for the small operation that places the tube. Nearly a third changed methods at least once.

The second finding is harder. Half the babies — 203 of 405 — died before leaving hospital. Among babies whose kidney failure came on suddenly during a severe illness, 41 per cent survived; among babies born with permanent kidney failure, 58 per cent did. In most cases the recorded reason for death was a decision, made with the family, to stop life-sustaining treatment when it was no longer helping.

The third finding has drawn the most attention, and it needs care. Among babies whose kidney failure came on suddenly, those started on the abdominal method were less likely to die than those started on a machine. This does not mean the machine causes harm. Babies stable enough to have an abdominal tube placed in theatre — and then to wait two weeks for it to heal — are by definition less critically ill than babies who need blood filtering within hours, and the researchers say clearly that their study cannot show cause and effect. What it shows is that when a baby is well enough for either option, there is no evidence that reaching for the machine is better.

The growth study found something more immediately fixable. Every one of the 18 babies fell behind: measured against healthy babies of the same age, by 90 days only about four in ten had a length in an acceptable range and about five in ten a weight in an acceptable range. But partway through the study period the unit raised its nutrition targets — from 90 to 110 calories per kilogram per day up to at least 130, and from 3.5 to at least 4 grams of protein per kilogram per day. Every single baby cared for under the higher targets reached acceptable length and weight, against about a third of those cared for earlier. With only 18 babies this cannot be the last word, but the direction is clear, and it is a change a hospital can make tomorrow at almost no cost.

Why nutrition is such a struggle on dialysis

It helps to understand why these babies lose ground. Dialysis does not only remove waste; it also removes protein and nutrients the baby needs, while critically ill babies burn through their own muscle for energy. And there are many days when full feeding cannot happen: an operation is scheduled, the tubing clots, or feeds are not tolerated. Meanwhile roughly a third of all the growing a person does in childhood happens in the first two years of life, so time lost here is not easily made up.

The Birmingham team's practical answers were unglamorous and worth repeating. They weighed babies twice a day, even those on ventilators and blood-pressure medications, and updated the weight used to calculate feeds weekly — because a stale weight quietly means an under-prescription every single day. They adjusted protein according to a blood test, and deliberately lowered the targets when a baby moved to the abdominal method, because the fluid used there contains sugar the body absorbs. International recommendations for children on dialysis had already argued that they need at least as much energy as healthy children of the same age, plus extra protein to replace what dialysis takes out [8].

What families are usually told, and what these studies add

When a serious kidney problem is picked up on an antenatal scan, parents are often given survival figures drawn from older records, which suggested that around three quarters to four fifths of such babies survived their first hospital stay [9]. Those conversations have been the subject of their own research, because what parents are told before birth shapes what they choose [10]. The newer figures are lower — a large international collaboration has similarly reported survival close to half [11] — and the likeliest explanation is not that care has worsened but that newer machines let hospitals treat sicker babies who would previously have been offered nothing, so the group being counted has changed.

One quiet finding deserves mention. In the whole 405-baby American study, no baby weighing under one kilogram at birth was started on dialysis, and fewer than ten weighed under 1.5 kilograms. Treatment has been reported in far smaller babies elsewhere, but in ordinary practice a line is being drawn — and the babies on the far side of it appear in none of these numbers.

What researchers are working on next

The most striking thing about this field is how much of it is still unsettled. The same international collaboration found the dose of filtering prescribed varied more than tenfold between hospitals treating similar babies, and surveys of European intensive care units have found wide differences in who prescribes the treatment, how many nurses are assigned per baby, and whether staff receive formal training [12]. That is why the AEIOU framework exists: not to introduce anything new, but to make each hospital's practice consistent enough that hospitals can finally be compared. Its authors are careful to say it has not yet been tested for whether it improves outcomes.

Three things are likely to move next. The first is a genuine trial comparing methods; almost none exist, and one of the few was a British study across six hospitals comparing the abdominal method, machine filtering, and a new infant dialysis device [13]. The second is a serious look at what happens to a baby's veins after two or three different tubes in three months, since those veins may be needed for a lifetime of treatment. The third is building proper neonatal kidney support programmes — a named lead, written protocols, practice drills and shared record-keeping — which specialists argue is the change most likely to help [14].

For a family sitting beside a baby on dialysis, the takeaways are these. The choice of method is not a verdict on the baby; it usually reflects how stable they are right now, and it is expected to change. Growth is not a side issue but a treatable one, and it is entirely reasonable to ask how many calories and how much protein your baby is prescribed and when that was last recalculated. And the honest answer about survival is that it remains difficult, that the numbers reflect a group of babies sicker than those counted a decade ago, and that this is why so much research effort is going into kidney injury in newborns [15]. In[Neo]Sight has also covered early tests that detect kidney injury in newborns sooner and what kidney injury in very premature babies means for later development.

References

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