At Kartini Clinic we have long been aware of the problem of hypophosphatemia (low blood phosphorus) with refeeding. In past decades when nearly all of our patients came to us via an initial hospitalization for medical instability, we were protected from hypophosphatemia in outpatient or day treatment settings by the fact that we had been so aggressive in testing for it and treating it while they were in the hospital. Today the majority of our patients are not hospitalized and re-feeding is done in a partial hospital (day treatment) or outpatient setting.

Hypophosphatemia is such a potential problem because of the central role phosphorus plays in many metabolic processes, such as muscle contraction in a beating heart, and conduction of signals to the heart telling it to beat in a regular fashion. Consequences of severe hypophophatemia can be heart failure, edema (swelling), paralysis and cardiac arrest, among others. Former prisoners of war and camp inmates after World War II actually died of uncontrolled (“ad lib”) re-feeding. Later, with the advent of intravenous feeds in burn patients, some of them suffered a similar fate until the biology of phosphorus metabolism was understood.

For those who would like to read an excellent scientific summary article, you can find one by Brown and Sable et al in the International Journal of Eating Disorders. This blog will be a brief summary of their findings, our clinical experience and other reports in the literature. There are two problems with hypophosphatemia:

1. It is silent; there are no reliable “symptoms”.
2. It is caused by the medical provider (or parent), as it is not the direct result of starvation but rather by the process of re-feeding itself.

Here’s what happens: following a prolonged period of semi-starvation or even acute starvation total body phosphorus stores are depleted. When carbohydrates are ingested the pancreas pumps out insulin which drags phosphorus (among other elements) into the cells of the body, effectively dropping its level in the blood (serum). This makes it unavailable to, for example, the heart muscle. Often, sometime around refeeding day 2 to 4, this low phosphorus level will be apparent in the patient’s labs. That is why we checked phosphorus levels every day when they were in the hospital.

The article cited above looked at predictors or risk factors for hypophosphatemia (btw, in this case controlled study about 1/3 of patients experienced some level of hypophosphatemia). How can we know which patients are most at risk of getting it?

Risk factors turned out to be:

• degree of weight loss (the lower the body weight or the greater the weight loss, the higher the risk)
• lower potassium levels (often seen with purging, but can be seen with extreme restricting)
• lower prealbumin
• higher hemoglobin (possibly reflecting dehydration).

Since many children at a very low weight are currently re-fed at home, I think our clinical experience might prove important here.

Any child who has been severely restricting their intake should be considered at risk, but possibly the most endangered child is the one who was premorbidly overweight or obese before they developed AN. These children may still be in the normal range for weight or BMI even after losing fantastic amounts of weight loss between 30-90 lbs, or more. Do not be fooled! They are very sick.

So how do we now handle that risk in day treatment or outpatient settings? After all, putting everyone in the hospital to initiate refeeding is probably not necessary or responsible.

People who regularly read this blog know that Kartini Clinic does not allow “ad lib” refeeding, meaning “eat all you want”, for many reasons. But more importantly, we check a phosphorus level during the first week of our refeeding, and we start kids on oral phosphorus supplements from day one if we are worried. It has been our (inpatient) experience that hypophosphatemia (less than 3.0 mg/dL in our lab) responds swiftly to supplementation. We use Neutra-Phos tablets (potassium phosphate/sodium phosphate), one tablet twice a day — or less, or more, depending on the phosphorus results. You’ll need a medical provider to help with this, even if you’re refeed at home.

In the past, fear of hypophosphatemia induced many practitioners to refeed very slowly (starting in some cases below 1000 kcals/day), which we now feel unnecessarily prolongs hospitalization and keeps a patient underweight longer. In general, the faster you get kids refed, the better off they are. And there is good data to support this view.

At Kartini Clinic we feed much more aggressively now in our partial hospital (day treatment) setting and simply start the phosphorus prophylactically. Then we check levels a couple of times over the first 7-10 days, depending on clinical indication. Both articles cited in this blog actually found no increase in hypophosphatemia in patients who were re-fed more “aggressively” — however, it must be noted that even these more aggressive intakes were below ours.

So refeed as you think best, but be aware and informed. Hypophosphatemia is real.