LUNG FLUXES OF LACTATE, PYRUVATE AND OTHER ENERGY BLOOD-BORNE SUBSTRATES DURING SURGICAL STRESS

Objective: To measure the pulmonary artery (PA)-systemic arterial conc entration differences and lung fluxes of glucose, lactate, pyruvate, a nd other substrates in response to surgical stress. Design: A prospect ive study Setting: Operating rooms in a University Hospital Patients: Seven patients undergoing radical cystectomy Measurements and Main Res ults: Blood was sampled simultaneously - after induction of anesthesia and before surgery, and during surgery - from an arterial and a PA ca theter. Blood glucose, lactate, pyruvate, alanine, beta-hydroxybutyrat e, and glycerol were determined by specific enzymic methods. Cardiac o utput was measured simultaneously. A progressive increase in glucose ( p < 0.001), lactate (p < 0.001), pyruvate (p < 0.01), alanine (p < 0.0 01), and a progressive decrease in beta-hydroxybutyrate (p < 0.025) (w ith no change in glycerol) concentrations were observed both in PA and arterial blood. Blood PA concentrations of glucose and substrates wer e not different from those in arterial blood (p NS). Significant linea r correlations (p < 0.01 or less) were found between glucose/substrate concentrations in PA and arterial blood. In each patient, the slopes of the changes over time in PA and arterial blood glucose and substrat es (except for glycerol) were all different from zero (p < 0.05 or les s). The mean difference in slopes and intercepts of the regression fun ctions were not different from zero. The PA-arterial systemic concentr ation differences and the respective lung fluxes for glucose and subst rates remained stable (p NS) and were not different from zero througho ut the study. Conclusions: During surgery: 1) glucose and substrate me asurements in PA blood yield concentrations that are essentially equiv alent to those in arterial blood 2) there is neither net production no r net consumption of glucose or other substrates across the lung 3) bl ood sampled from a PA can be used interchangeably with arterial blood to measure glucose and substrate concentrations.