Crystalloid strong ion difference determines metabolic acid-base change during acute normovolaemic haemodilution.
OBJECTIVE
To study the acid-base effects of crystalloid strong ion difference (SID) during haemodilution.


METHODS
Prospective in vivo study.


METHODS
University laboratory.


METHODS
Anaesthetised, mechanically ventilated Sprague-Dawley rats.


METHODS
Rats were studied in seven groups of three. Each group underwent normovolaemic haemodilution with one of seven crystalloids, with SID values from 0 to 40 mEq/l. Six exchanges of 9 ml crystalloid for 3 ml blood were performed.


RESULTS
[Hb] fell from 142+/-17 to 44+/-10 g/l ( p<0.0001). Final plasma [lactate] was 1.1+/-0.6 mmol/l. Final standard base excess values ranged from -8 to +7 mmol/l, and were directly correlated with crystalloid SID (R(2)=0.91). By linear regression, the SID of a crystalloid balanced to maintain standard base excess=0 mmol/l was 23.7 mEq/l. Dilutions 2-5 produced similar results.


CONCLUSIONS
There is a linear relationship between crystalloid SID and post-dilutional metabolic acid-base status. The SID of a crystalloid balanced for normovolaemic haemodilution is 24 mEq/l. These principles are applicable in designing fluids for volume resuscitation, acute normovolaemic haemodilution and cardio-pulmonary bypass.
Morgan
Thomas J
TJ
Adult Intensive Care Unit, Mater Misericordiae Hospital, Raymond Terrace, 4101 South Brisbane, Queensland, Australia. thomas_morgan@mater.org.au
Venkatesh
Balasubramanian
B
Hall
Jonathan
J
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000818:Animals; D000077324:Crystalloid Solutions; D006438:Hemodilution / Q000379:methods*; D007477:Ions; D007552:Isotonic Solutions; D016014:Linear Models; D008297:Male; D023421:Models, Animal; D010952:Plasma Substitutes / Q000008:administration & dosage* / Q000494:pharmacology; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley
D000077324:Crystalloid Solutions; D007477:Ions; D007552:Isotonic Solutions; D010952:Plasma Substitutes