title: Infusion of 2.5 meq/min of Lactic Acid minimally increases CO2 production compared to an isocaloric glucose infusion in healthy anesthetized, mechanically ventilated pigs.
abstract: BACKGROUND
  Blood acidification by lactic acid infusion converts bicarbonate to CO2. This effect can be exploited to increase the transmembrane PCO2 gradient of an extracorporeal membrane lung, resulting in a significant increase of extracorporeal CO2 removal. Lactic acid, however, is an energetic substrate and its metabolism might increase total body CO2 production (VCO2), limiting the potential beneficial effects of this technique. The aim of our study was to compare VCO2 during isocaloric infusion of lactic acid or glucose.
  
  
  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.
authors.forename: Alberto
authors.initials: A
authors.lastname: Zanella
authors.forename: Marco
authors.initials: M
authors.lastname: Giani
authors.forename: Sara
authors.initials: S
authors.lastname: Redaelli
authors.forename: Paolo
authors.initials: P
authors.lastname: Mangili
authors.forename: Vittorio
authors.initials: V
authors.lastname: Scaravilli
authors.forename: Valentina
authors.initials: V
authors.lastname: Ormas
authors.forename: Marco
authors.initials: M
authors.lastname: Costanzi
authors.forename: Mariangela
authors.initials: M
authors.lastname: Albertini
authors.forename: Giacomo
authors.initials: G
authors.lastname: Bellani
authors.forename: Nicolò
authors.initials: N
authors.lastname: Patroniti
authors.forename: Antonio
authors.initials: A
authors.lastname: Pesenti
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D002405:Catheterization, Central Venous; D002149:Energy Intake; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D007262:Infusions, Intravenous / Q000379:methods; D007558:Italy; D019344:Lactic Acid / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D012121:Respiration, Artificial; D013552:Swine
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid; D005947:Glucose