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Erschienen in:
01.07.2004 | Experimental
Crystalloid strong ion difference determines metabolic acid–base change during acute normovolaemic haemodilution
Erschienen in: Intensive Care Medicine | Ausgabe 7/2004
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Objective
To study the acid–base effects of crystalloid strong ion difference (SID) during haemodilution.
Design
Prospective in vivo study.
Setting
University laboratory.
Subjects
Anaesthetised, mechanically ventilated Sprague-Dawley rats.
Interventions
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.
Measurements and main 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 (R2=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.