Acid-base and bio-energetics during balanced versus unbalanced normovolaemic haemodilution.
Fluids balanced to avoid acid-base disturbances may be preferable to saline, which causes metabolic acidosis in high volume. We evaluated acid-base and bio-energetic effects of haemodilution with a crystalloid balanced on physical chemical principles, versus crystalloids causing metabolic acidosis or metabolic alkalosis. Anaesthetised, mechanically ventilated Sprague-Dawley rats (n=32, allocated to four groups) underwent six exchanges of 9 ml crystalloid for 3 ml blood. Exchange was with one of three crystalloids with strong ion difference (SID) values of 0, 24 (balanced) and 40 mEq/l. Controls did not undergo haemodilution. Mean haemoglobin concentration fell to approximately 50 g/l after haemodilution. With SID 24 mEq/l fluid, metabolic acid-base remained unchanged. Dilution with SID 0 mEq/l and 40 mEq/l fluids caused a progressive metabolic acidosis and alkalosis respectively. Standard base excess (SBE) and haemoglobin concentration were directly correlated in the SID 0 mEq/l group (R2 = 0.61), indirectly correlated in the SBE 40 mEq/l group (R2 = 0.48) and showed no correlation in the SID 24 mEq/l group (R2 = 0.003). There were no significant differences between final ileal values of CO2 gap, nucleotides concentration, energy charge, or luminal lactate concentration. SID 40 mEq/l crystalloid dilution caused a significant rise in subcutaneous lactate. In this group mean kidney ATP concentration was significantly less than controls and renal energy charge significantly lower than SID 0 mEq/l and control groups. We conclude that a crystalloid SID of 24 mEq/l provides balanced haemodilution. Bio-energetic perturbations with higher SID haemodilution may be more severe and need further investigation.
Morgan
T J
TJ
University of Queensland Intensive Care Laboratories, Royal Brisbane Hospital, Brisbane, Queensland, Australia.
Venkatesh
B
B
Beindorf
A
A
Andrew
I
I
Hall
J
J
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000138:Acidosis / Q000139:chemically induced; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000471:Alkalosis / Q000139:chemically induced; D000818:Animals; D000077324:Crystalloid Solutions; D004734:Energy Metabolism / Q000187:drug effects*; D006438:Hemodilution / Q000379:methods*; D006454:Hemoglobins / Q000187:drug effects; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007552:Isotonic Solutions / Q000008:administration & dosage / Q000494:pharmacology*; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014882:Water-Electrolyte Balance
D000077324:Crystalloid Solutions; D006454:Hemoglobins; D007552:Isotonic Solutions; D019344:Lactic Acid; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate