Dilution with three diff erent solutions : plasmatic eff ects and quantity and quality of urinary output

Introduction Crystalloids have diff erent electrolyte composition
and therefore diff erent strong ion diff erences (SIDinf ). The aim of the
study was to investigate the response of the kidney to plasmatic acid–
base changes induced by dilution with three crystalloid solutions at
diff erent SID.
Methods Six pigs (22 ± 4 kg) were anesthetized and mechanically
ventilated. The respiratory rate was adjusted to maintain pCO2
constant. A urinary catheter was placed and connected to a urinary
analyzer (Orvim, Paderno Dugnano, Italy) [1]. Pigs were randomly
assigned to a sequence of dilutions (10% of body weight in 2 hours,
followed by 4 hours of washout period) with the following three fl uids:
normal saline (NS), SID = 0, [Na] = 154, [Cl] = 154; lactated Ringer’s
(LR), SID = 29, [Na] = 132, [Cl] = 112; and polysaline RIII (RIII), SID = 55,
[Na] = 140, [Cl] = 103. Blood gases and electrolytes as well as urinary pH
(pHu), urinary electrolytes and urinary output (UO) were recorded at
baseline and at the end of each dilution. Plasmatic SID was defi ned as
[Na] + [K] + 2[Ca] – [Cl] – [Lac]. Variations (d) were defi ned as baseline
– 2-hour value.
Results Plasmatic changes are consistent with previous in vitro studies
[2]. dSID was mainly due to d[Cl]: 9.0 ± 1.7 for NS, no change for LR,
–1.5 ± 1.6 for RIII. Of note, while no diff erence was yet observed for
urinary electrolytes and UO, pHu signifi cantly diff ered between the
three solutions. See Table 1.
Table 1 (abstract P86)
NS LR RIII
dpHa –0.08 ± 0.02 –0.00 ± 0.03* 0.04 ± 0.03*#
dSID (mEq/l) –4.56 ± 1.36 0.21 ± 1.41* 3.56 ± 1.95*#
dpHu –0.16 ± 0.47 0.23 ± 0.44 1.00 ± 0.75*#
UO (ml) 639 ± 235 768 ± 172 896 ± 293
Data presented as mean ± standard deviation. *P <0.05 vs. NS. #P <0.05 vs. LR.
One-way ANOVA RM.
Conclusions The quality of infused fl uids aff ects greatly the acid–base
and electrolyte equilibrium of plasma. This in turn alters the quality of
urine (pHu).
References
1. Caironi P: Minerva Anestesiol 2010, 76:316-324.
2. Carlesso E: Intensive Care Med 2010. [Epub ahead of print]