During citrate-based Continuous Renal Replacement Therapy (CRRT), an infusion of calcium is necessary to replace the calcium lost in the effluent. The replacement takes place through a central venous catheter (CVC) that is primed with saline solution. Thus, we hypothesized a potential systemic anticoagulation caused by the unchelated citrate reaching the patient at the start of CRRT because of 0.42 ml of line dead space. In this pilot study, two subpopulations of 7 patients who underwent Continuous Veno-Venous Hemodiafiltration (150 ml/min of blood flow, 1500 ml/h dialysate flow, 1500 ml/h of citrate predilution) were studied. One had the CVC primed with saline, the second with calcium chloride 10%. Calcium replacement rate was 6.3 ± 0.2 ml/h. Ionized calcium concentration was studied over time in the two groups and in the group with saline priming we detected a transient period of hypocalcemia (ionized calcium concentration [iCa] < 1.00 mmol/l for the first 2 hours). In the subpopulation with the calcium priming, this was not present. No significant effect on filter life emerged. Priming of the catheter with calcium seems effective in avoiding a potential issue regarding citrate accumulation at the start of CRRT. More studies are needed to assess the clinical significance of this finding.

Background: The importance of knowing the blood volume, in critically ill patients, collides with the difficulty to have its direct measure through a safe and economic method. Hydroxyethyl starch (HES) was introduced by Tschaikowsky as a useful marker for the dilution method, calculating the HES concentration (HESC) in a solution by inducing an in-vitro hydrolysis of starch molecules into glucose monomers and dosing the consequent increase of the solution glucose level (Δ GLUCOSE).Objective: This study develops a simple and cheap laboratory technique which uses a new generation 6% 130/0,4 Hydroxyethyl starch as a possible "dilution marker" for the measurement of patient's blood volume maintaining Tschaikowsky's study protocol. The aim is to refocus attention on an interesting method that could lead the way to a number of possibilities in critical area. Method:We designed a two-phase in-vitro experiment. Firstly, we found out the suitable treatment duration to ensure a complete hydrolysis of starch molecules. Secondly, we aimed to the achievement of a univocal constant of proportionality (K) between Δ GLUCOSE and HES concentration. HESC will be expressed as HESV/PV (μl/mL) where HESV represents the HES volume and PV the plasma volume. Plasma volumes were calculated as BV*(1-Ht).Results: K was planned by means of a linear regression analysis between HESV/PV and Δ GLUCOSE on 133 validated samples collected from 30 healthy volunteers. The obtained hematocrit values ranged between 39.9 and 48 (mean ± CI 95%=42,62 ± 2,93). This corresponded to HESC ranging from 0,033 to 0,038 HES (mL)/PV (mL) (mean ± CI 95%=0,035 ± 0,002). While hydrolysis times increase, glucose values tended to augment until they reached stable plateau. During the second phase we handled a total of 720 specimens. Hematocrit of collected samples ranged from 33,9 to 49 (mean ± CI 95%=41,3 ± 1,21). HESC ranged between 0,015 and 0,089 mL HES/mL PV (mean ± CI 95%=0,037 ± 0,003). The regression analysis showed that HESC equals 0,592 times Δ GLUCOSE (R2=0,947). Conclusion:This study might be the first step in reintroducing starches into the clinical management of critical patients, not just as therapeutic agents for volume resuscitation but even as useful markers in the diagnosis of hemodynamic derangements, improving fluid and blood therapy strategies.

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