Serum calcium should be measured because of the strong association of 22q11 deletion syndrome with hypocalcemia. Serum glucose and sodium levels should be reviewed, as the infant will have been started on total parenteral nutrition due to the inability of oral feeding from dysphagia caused by the cystic hygroma. Because there is also the potential for severe metabolic acidosis secondary to inadequate perfusion of the lower body as a result of the IAA, serum pH and bicarbonate concentrations must be obtained. The Paco₂ will indicate baseline adequacy of ventilation in the face of a potentially obstructing mass, and the Pao₂ will serve as a guide in assessing the degree of CHF, pulmonary insufficiency, and central shunting. Because the surgery can be extensive with a significant loss of blood, a baseline complete blood count with hematocrit, as well as a type and screen, should be obtained. Prothrombin time and partial thromboplastin time should be obtained before surgery because of the possibility of baseline immaturity in coagulation factor production and the inherent bleeding potential from the large dissection that will be done.