Effect of 7.5% hypertonic saline solution on whole blood coagulation in healthy dogs using thromboelastography

Intravenous Fluid Administration and the Coagulation System

Intravenous fluid administration in veterinary patients can alter coagulation function by several mechanisms. Both crystalloid and colloid fluids cause hemodilution, reducing platelet count and plasma coagulation protein concentrations. Hemodilution is associated with a hypercoagulable effect at low dilutions and a hypocoagulable effect at higher dilutions. Composition of crystalloid fluids likely has a minor effect, primarily dependent on fluid ion composition. Hypertonic crystalloids may also cause hypocoagulability. Colloids, both synthetic and natural, can cause hypocoagulability by several mechanisms beyond the effects of hemodilution. These include impaired platelet function, decreased plasma coagulation factor activity, impaired fibrin formation and crosslinking, and accelerated fibrinolysis. The vast majority of the veterinary literature investigates the hypocoagulable effects of hydroxyethyl starch-containing fluids using in vitro, experimental, and clinical studies. However, results are inconsistent, likely due to the varying doses and physicochemical properties of the specific fluid products across studies. In addition, some evidence exists for hypocoagulable effects of gelatin and albumin solutions. There is also evidence that these colloids increase the risk of clinical bleeding in people. Limitations of the veterinary evidence for the hypocoagulable effects of colloid fluids include a predominance of in vitro studies and in vivo studies using healthy subjects, which exclude the interaction of the effects of illness. Therefore, clinical relevance of these effects, especially for low-molecular-weight hydroxyethyl starch, is unknown. Firm recommendations about the most appropriate fluid to use in clinical scenarios cannot be made, although it is prudent to limit the dose of synthetic colloid in at-risk patients. Clinicians should closely monitor relevant coagulation assays and for evidence of hemorrhage in at-risk patients receiving any type of fluid therapy, especially in large volumes.

Effect of 7.5% hypertonic saline solution on whole blood coagulation in healthy dogs using thromboelastography

Objective

To evaluate the effects of 7.5% hypertonic saline solution (HSS) on whole blood coagulation in healthy dogs and to compare electrolyte and osmolality measurements between in vivo and in vitro dilution with HSS.

Design

Experimental study.

Setting

University teaching hospital.

Animals

Twelve adult purpose‐bred Beagles.

Interventions

All 12 dogs received 5 mL/kg 7.5% HSS at 1 mL/kg/min. After a 14‐day washout period, 5 of these dogs were randomly selected and received the same volume of 0.9% NaCl. Blood samples were collected before infusion, immediately after infusion, and at 30, 60, and 90 minutes after infusion for the measurement of coagulation using thromboelastography. For comparison of electrolyte concentrations and osmolality between in vitro dilution and in vivo dilution of HSS, 6‐mL blood samples were diluted with 7.5% HSS (1:18 ratio) at baseline.

Measurements and Main Results

None of the thromboelastography variables differed significantly between the 7.5% HSS group and the 0.9% NaCl group. The sodium and chloride levels, and the osmolality, were significantly increased at all postinfusion time points compared to baseline, while those levels were significantly higher with in vitro dilution than all postinfusion time points. However, almost all the values gradually decreased and became similar to baseline values in case of in vivo dilution.

Conclusions

The clinically relevant dose of 7.5% HSS (5 mL/kg) did not affect whole blood coagulation significantly in healthy Beagles. Further studies are necessary to assess the effect of HSS on blood coagulation in canine patients with shock.