Xavier Leverve

Effect of cardiopulmonary bypass on lactate metabolism

ObjectiveWe have investigated the role of cardiopulmonary bypass on lactate metabolism in patients undergoing uncomplicated surgery for elective coronary artery bypass grafting (CABG).DesignProspective non-randomized observational study.SettingsNational Cardiovascular Center.PatientsThree independent groups were studied: preoperative (n=20), postoperative with bypass (CPB, n=20) and postoperative without bypass (NO-CPB, n=20).InterventionsLactate metabolism was investigated with the use of an exogenous lactate challenge test (2.5xa0mmolxa0Na-lactate/kgxa0bodyxa0weightxa0in 15xa0min). Blood lactate was sequentially determined after the end of infusion. Lactate clearance and endogenous production were estimated from the area under the curve, and a bi-exponential fitting permitted modeling the lactate-decay into two compartments.Measurements and main resultsLactate metabolism parameters (basal lactate, clearance, endogenous production and half-lives [HL] I and II) were not different between the NO-CPB and preoperative groups. In the CPB group, as compared to the other two groups, basal lactate and endogenous production were not significantly affected while lactate clearance (CPB: 6.02±0.97 versus preoperative: 9.41±0.93 and NO-CPB: 9.6±0.8xa0ml/kg per min) and HL-I (CPB: 10.6±1.4 versus preoperative: 17.2±2.3 and NO-CPB: 18.8±2.5xa0min) were decreased (p<0.001) and HL-II was increased (CPB: 171±41versus preoperative: 73±12 and NO-CPB: 48±2.9xa0min, p<0.01).ConclusionWhile surgery and anesthesia per se do not seem to alter lactate metabolism, CPB significantly decreased lactate clearance, this effect being possibly related to a mild liver dysfunction even in uncomplicated elective surgery.

Muscle protein degradation in severely malnourished patients with chronic obstructive pulmonary disease subject to short-term total parenteral nutrition.

Patients with chronic obstructive pulmonary disease (COPD) often lose weight and muscle mass with progression of the disease. Muscle protein degradation in patients with COPD has never been examined before and during hypercaloric feeding. Eight severely malnourished patients with COPD were examined at home consuming their usual intake, in the hospital after 3 days of a meat-free regular oral diet (period B), and during a hypercaloric (55 kcal/kg) high-lipid (55%) parenteral formula (total parenteral nutrition [TPN]). During period B, 8 well-nourished patients and 10 malnourished cancer patients were used as control groups. Measurements included plasma assays, leg blood flow, leg exchange (of 3-methylhistidine [3MeH], glucose, lactate, and oxygen) and urinary measures of 3MeH, creatinine, and nitrogen. During period B, net release of 3MeH across the leg in patients with COPD was similar to that in well-nourished control subjects and cachectic cancer patients. In COPD patients, there was only a transient decrease in leg exchange values of 3MeH with administration of TPN. COPD patients demonstrated a reduction (p less than .01) in urinary 3MeH excretion and an increase in nitrogen balance (p less than .01) with TPN compared with period B. The decrease in muscle protein degradation with administration of TPN accounts for about 50% of the increase in nitrogen retention in patients with COPD. These data suggest that in severely malnourished patients with COPD the weight loss is not dependent on increased rates of skeletal muscle protein degradation; nevertheless, degradation rates attenuate with a positive nitrogen balance during nutrition repletion.

Nutrition parentérale: modélisation appliquée à la stabilité des mélanges ternaires

Resume Cette etude porte sur la stabilite des solutions utilisees en nutrition parenterale se presentant sous forme dun melange unique renfermant acides amines, glucides et lipides (melange dit «ternaire). La stabilite est evaluee par la mesure du pH et de la taille des globules lipidiques disperses dans lemulsion, sur des solutions standards auxquelles on ajoute lun des electrolytes suivants : Na + , K + , Ca ++ . Ces reponses sont decrites a laide de modeles lineaires (Y = A0 + A1.X1 + A2.X2 + A3.X3 + A4.X4) comme des fonctions des parametres influants suivants Xi: -- temps de stockage des melanges ternaires -- temperature de stockage -- concentration en electrolytes -- temps de conservation apres addition de lelectrolyte. Une telle modelisation permet danalyser et de quantifier linfluence de chaque parametre.