title: Elevated arterial lactate concentrations early after coronary artery bypass grafting are associated with increased anaerobic metabolism in skeletal muscle.
abstract: OBJECTIVE
  To assess the effect of coronary artery bypass grafting with cardiopulmonary bypass on muscle perfusion, oxygen extraction, and lactate release during postoperative rest and exercise.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Patients undergoing planned coronary artery bypass grafting.
  
  
  METHODS
  Knee-extensor exercise before and after coronary artery bypass grafting.
  
  
  RESULTS
  Femoral artery blood flow was measured with ultrasound. Femoral vein blood and arterial blood were sampled at rest and during light exercise and were analyzed for hemoglobin, lactate, oxygen saturation, and oxygen partial pressure. Fourteen patients were tested before and after surgery. The arterial lactate concentrations were increased after surgery, both at rest and during light exercise. Resting arterial lactate increased from 0.65 (0.5-0.8) to 1.0 (0.9-1.3) mmol/L (p=0.01) (median and interquartile range). Furthermore, lactate was released from the leg even during postoperative rest, and the release of lactate was increased during postoperative exercise. There were no significant differences between the preoperative and postoperative femoral artery blood flow. Femoral vein oxygen partial pressure was reduced significantly after surgery, indicating reduced muscle cell oxygen partial pressure.
  
  
  CONCLUSIONS
  The patients had elevated anaerobic metabolism in skeletal muscle after surgery to compensate for anemia. Lactate was released from the leg into the general circulation during postoperative rest and exercise. The postoperatively reduced hemoglobin concentration of 11.4 mg/dL (10.6-12.3) resulted in increased anaerobic metabolism and release of lactate from skeletal muscle. The authors concluded that coronary artery bypass grafting patients are susceptible to anaerobic metabolism even with maintained peripheral blood flow.
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; K. G. Jebsen Center for Exercise in Medicine, Norwegian University of Science and Technology, Trondheim, Norway. Electronic address: hans.h.dedichen@ntnu.no.
authors.forename: Hans Henrik
authors.initials: HH
authors.lastname: Dedichen
authors.affiliation: Section for Vascular Investigations, Oslo Vascular Centre, Oslo University Hospital Aker, Oslo, Norway.
authors.forename: Jonny
authors.initials: J
authors.lastname: Hisdal
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Petter
authors.initials: P
authors.lastname: Aadahl
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; Department of Cardiothoracic Surgery, St. Olav's Hospital, Trondheim, Norway.
authors.forename: Dag
authors.initials: D
authors.lastname: Nordhaug
authors.affiliation: Department of Cardiothoracic Anesthesiology and Intensive Care, St. Olav's Hospital, Trondheim, Norway.
authors.forename: Per Olav
authors.initials: PO
authors.lastname: Olsen
authors.affiliation: Department of Cardiothoracic Anesthesiology and Intensive Care, St. Olav's Hospital, Trondheim, Norway.
authors.forename: Idar
authors.initials: I
authors.lastname: Kirkeby-Garstad
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology*; D015415:Biomarkers / Q000097:blood; D001026:Coronary Artery Bypass / Q000639:trends*; D005260:Female; D005263:Femoral Artery / Q000378:metabolism*; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D011184:Postoperative Period; D011446:Prospective Studies
chemical_list: D015415:Biomarkers; D019344:Lactic Acid
keywords: cardiac surgery; lactate; oxygen consumption; postoperative care