A dramatic decline in vitamin D levels among children undergoing congenital heart surgery was associated with the use of the cardiopulmonary bypass machine, a prospective observational study found.

During surgery, researchers found a mean decline of 25 nm in serum 25-hydroxyvitamin D (25[OH]D), which translated into a mean acute change of 40 percent, according to Dermot R. Doherty, MB, BCh, MD, of the University of Ottawa in Ontario, and colleagues.

However, when they compared the decline in 25(OH)D between four patients who did not undergo cardiopulmonary bypass with the rest of the patients who did, they found a greater mean change among the cardiopulmonary bypass group (11 percent versus 42 percent, P=0.01).

The "abrupt" change in 25(OH)D coincided with the initiation of the cardiopulmonary bypass machine, they wrote in the study published online in the journal Anesthesiology.

A linear regression analysis pointed to three independent variables associated with postoperative 25(OH)D: preoperative levels of 25(OH)D, need for cardiopulmonary bypass, and preoperative weight.

"Although we did not test for it specifically, it is highly unlikely that anesthetic technique factored into the decline in vitamin D," researchers wrote.

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