Pre-operative Short-term Administration of a Formula Diet Containing a Non-milk-derived Protein Source for Prevention of Acute Kidney Injury After Cardiac Surgery

Cardiac surgery is associated with a high risk of postoperative AKI with significant morbidity and mortality. Acute kidney injury (AKI) constitutes a significant complication in hospitalized patients with an incidence of about 30%. Depending on existing comorbidities, a mortality of up to 60% occurs in critically ill or postoperative patients with AKI. To date, no preventive or therapeutic measures exist to prevent this. According to the data from animal trials, a preoperative diet low in sulfur-containing amino acids may be a new preventive measure in this context.

This trial will investigate whether one week of changing the diets protein source to a non-milk-derived one prior to surgery effectively induces renal protection from post-surgery AKI in humans. Patients undergoing elective cardiac surgery are randomized into two arms.

In the non-milked-derived based diet arm, patients receive an appropriate formula diet based on a protein source other than milk derived proteins. The formula diet replaces the regular diet completely from day -7 until the scheduled cardiothoracic surgery. The amount of formula diet is based on individual calculations to cover the patients daily energy demand.

In the control arm, patients are provided with a formula diet based on milk-protein, accordingly. Total amount of calories and proteins is not restricted and - due to randomization - assumed not to be significantly different between the two arms.

The primary endpoint of the clinical trial is to investigate whether a preoperative diet with a deficiency of milk-derived proteins leads to a reduction of AKI incidence within 72 hours after surgery. AKI is defined according to 'Kidney Disease: Improving Global Outcomes' (KDIGO) classification as an increase in serum creatinine of ≥0.3 mg/dl within 48 hours, or an increase of serum creatinine to ≥1.5 times baseline, which is known or presumed to have occurred within the prior 7 days, or a reduction of urine output to <0.5ml/kg/hour for more than 6 hours.

Baseline creatinine will be assessed prior to the start of the surgical procedure. The time frame for the following assessments with respect to the primary endpoint will be 72 hours from the onset of ischemia (cross-clamping). Blood samples will be obtained at 24 hours, 48 hours, and 72 hours after cross-clamping. Hourly urine output will be assessed as long as a Foley-catheter is in place.

Inclusion criteria

• Men and women ≥50 years of age
• Caucasian ethnicity
• Scheduled cardiac surgery with use of the heart-lung machine with a lead time of at least 9 days
• Written informed consent

Exclusion criteria

• Chronic renal replacement therapy
• Status post kidney transplantation
• Vegetarian lifestyle
• BMI <18.5 kg/m2
• Calorie-reduced diet within the preceding 4 weeks
• Underlying wasting disease
• Uncontrolled local or systemic infection
• Contraindication for enteral nutrition
• Known allergy to or intolerance of the ingredients of the formula diets used
• Pregnancy or breastfeeding
• Absence of safe contraceptive measures or non-occurrence of menopause (in women)
• Participation in other interventional trials
• Persons who are in a dependency/employment relationship with the investigators
• Accommodation in an institution by judicial or administrative order.