Randomized controlled trial of evaluation of the optimal dose of postoperative enteral high N-nutrition and effect on clinical outcome in complex congenital heart disease children

INTERVENTION: High‐protein Group:Feed ordinary milk powder + whey albumen powder (3.5 g / kg / day);Medium‐protein Group:Feed ordinary milk powder + whey albumen powder (2.5 g / kg / day);Low‐protein Group:Feed ordinary milk powder + whey albumen powder (1.5 g / kg / day); Control Group:Feed ordinary milk powder ; CONDITION: complex congenital heart disease PRIMARY OUTCOME: nitrogen balance;Aminogram; SECONDARY OUTCOME: Biochemical Indicator;Clinical Indicator;Milk yield Indicator;Tolerance Indicator; INCLUSION CRITERIA: 1. Complex congenital heart disease with concurrent cardiopulmonary bypass; 2. Aged between 1 and 12 months; 3. Intensive care unit (ICU) for at least 5 days after operation.