Conclusions
Replacing 50% of the caloric input with lactic acid increased total CO2 production by less than 5% compared to an equal caloric load provided entirely by a 50% glucose solution.
Methods
Six pigs (45 ± 5 kg) were sedated and mechanically ventilated. Estimated caloric needs were 2,300-2,400 Kcal/die (95 to 100 Kcal/h). A sequence of two steps lasting four hours each was performed: 1) Glucose, 97 kcal/h were administered as 50% glucose solution, and 2) Lactic Acid, approximately 48.5 kcal/h were administered as lactic acid and approximately 48.5 kcal/h as 50% glucose solution. This sequence was repeated three times with two-hour intervals. Every hour VCO2, arterial blood gases and lactate were measured. Blood glucose level was kept constant by titrating an insulin infusion, ventilation was adjusted to maintain arterial PCO2 at 50 mmHg, a normal value for our animal model.
Results
During Lactic Acid steps VCO2 increased less than 5% compared to the Glucose steps (282 vs. 269 ml/min, P < 0.05); blood glucose did not differ between the two groups (respectively 101 ± 12 vs. 103 ± 8 mg/dl). Arterial lactate was always lower than 3 mmol/L. Arterial pH was lower during Lactic Acid steps (7.422 vs. 7.445, P < 0.05). Conclusions: Replacing 50% of the caloric input with lactic acid increased total CO2 production by less than 5% compared to an equal caloric load provided entirely by a 50% glucose solution.