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]