Effects of acute dilutional hyponatremia on acid-base changes and electrolyte concentrations in rats with bilateral renal pedicle ligation.
OBJECTIVE
To describe the effects of increasing the extracellular fluid (ECF) volume by approximately 20% on acid-base changes and electrolyte concentrations in anesthetized rats.


METHODS
18 adult male Sprague-Dawley rats.


METHODS
Rats were assigned to a control group (n = 6 rats) and a treatment group (12). All rats were anesthetized, and instrumentation and bilateral renal pedicle ligation were performed. The treatment group was infused IV with sterile water throughout a 30-minute period. Acid-base variables and concentrations of electrolytes, lactate, albumin, phosphorus, and hemoglobin were measured before (baseline) and 30 and 60 minutes after onset of infusion. Anion gap, strong ion difference, strong ion gap, and contributions of sodium, chloride, albumin, phosphorus, and lactate concentrations to base excess were calculated at each time point.


RESULTS
Infusion of sterile water led to an increase in ECF volume of approximately 18%. This had no effect on acid-base balance, compared with that in control rats. Infusion of sterile water caused a significant decrease in sodium, chloride, ionized calcium, lactate, and albumin concentrations, compared with concentrations in the control group. Anion gap and calculated effects of sodium, chloride, albumin, and lactate concentrations on base excess at 60 minutes differed significantly between infused and control rats.


CONCLUSIONS
Infusion of sterile water did not cause clinically relevant dilutional acidosis. The acidotic impact of water administration was offset by generation of new bicarbonate via carbonic acid equilibration and intracellular buffering in combination with the alkalotic effects of decreases in albumin, phosphorus, and lactate concentrations.
Hopper
Kate
K
Department of Veterinary Surgery and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA. khopper@ucdavis.edu
Haskins
Steve C
SC
D000818:Animals; D001639:Bicarbonates / Q000097:blood; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D002712:Chlorides / Q000097:blood; D004573:Electrolytes / Q000097:blood*; D045604:Extracellular Fluid / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D007262:Infusions, Intravenous / Q000379:methods / Q000662:veterinary; D008297:Male; D010758:Phosphorus / Q000097:blood; D011188:Potassium / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012077:Renal Artery / Q000601:surgery; D012082:Renal Veins / Q000601:surgery; D012964:Sodium / Q000097:blood; D014139:Tracheostomy / Q000379:methods / Q000662:veterinary
D001639:Bicarbonates; D002712:Chlorides; D004573:Electrolytes; D006454:Hemoglobins; D002245:Carbon Dioxide; D010758:Phosphorus; D012964:Sodium; D011188:Potassium