title: Temperature and acid-base balance in coronary bypass grafting with cardiopulmonary bypass, under hypothermia and normothermia.
abstract: OBJECTIVE
  Cardiopulmonary bypass (CPB) is related to several changes in normal physiology. The multiple causes of these changes interact and are a potential risk for postoperative organic dysfunction. This study aimed at investigating changes in acid-base and metabolic balance during cardiopulmonary bypass with hypothermia and at comparing them to those observed in patients submitted to normothermal cardiopulmonary bypass.
  
  
  METHODS
  Participated in this study 30 adult patients of both genders, aged 41 to 78 years, scheduled for coronary bypass grafting with CPB, under normothermia or hypothermia. The following parameters were evaluated: hemoglobin and blood gases concentration, pH, bicarbonate, base excess, anion gap, lactate ion, tissue oxygenation parameters and flow and systemic vascular resistance.
  
  
  RESULTS
  There were no statistically significant differences in arterial pH, arterial bicarbonate, Na+ and Cl- plasma concentrations, anion gap, carbon dioxide partial pressure and arterial oxygen content between Normothermia and Hypothermia Groups. A time-effect was observed for all variables except for base excess and anion gap. Base excess and K+ concentration were lower in the hypothermia group. Serum lactate increased in both groups when comparing time before CPB to after CPB, with higher levels in the hypothermia group.
  
  
  CONCLUSIONS
  Mild hypothermia does not seem to substantially change acid-base balance as compared to normal temperature during CPB. Plasma lactate, however, has significantly increased in patients under hypothermia, suggesting inadequate oxygen transport to periphery during the proposed observation period. Low temperature, although mild, does not seem to offer the expected degree of cell protection to CPB blood flow.
authors.affiliation: Instituto do Coração do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP.
authors.forename: Hugo Leonardo de Moura
authors.initials: HL
authors.lastname: Luz
authors.forename: José Otávio Costa
authors.initials: JO
authors.lastname: Auler Junior