The Effect of an Intravenous Fluid Bolus on the Endothelial Glycocalyx
Abstract Number: F 19
Abstract Type: Original Research
Background: Due to normal physiologic changes during pregnancy, the parturient is prone to develop interstitial edema from decreased intravascular oncotic pressure. This edema can be exacerbated by crystalloid administration. However, crystalloid therapy is routinely used to treat hypovolemia and hypotension during labor and delivery. The endothelial glycocalyx (EG), a layer of extracellular glycoproteins and proteoglycans, plays an important role in regulating fluid shifts. Disruption of the EG can lead to edema formation. To study the potential harmful effects of a crystalloid bolus on the EG in the parturient, we measured two biomarkers of the EG before and after giving a fluid bolus.
Methods: Patients recruited for the study were healthy term parturients scheduled for elective cesarean delivery under spinal anesthesia. Two peripheral IVs were placed in opposite arms – one for fluid administration and one for blood sampling. A baseline blood sample was obtained. Then, 750 mL of warmed (approximately 38 degrees Celsius) lactated Ringer’s was infused over 15 minutes. Afterwards, a post-bolus blood sample was obtained. Finally, a blood sample was collected at the end of surgery to be used as a reference. Blood markers studied were serum heparan sulfate and serum syndecan-1. To account for the dilutional effects of fluid administration, we adjusted the serum concentrations by total serum protein. We used a paired t-test to test the null hypothesis H0:μBL=μBolus versus Ha:μBL<μBolus where BL=baseline.
Results: There were notable trends towards increased values for both glycocalyx markers. Mean serum syndecan-1 levels were 15.1 ng/mg protein compared to 17.0 ng/mg protein after fluid bolus (p=0.179) and mean serum heparan levels were 395.3 ng/mg protein compared to 472.9 ng/mg protein after fluid bolus (p=0.120).
Conclusions: The results of this study indicate that a crystalloid fluid bolus disrupts the EG. If this trend is confirmed, then alterations in fluid management strategies in both the parturient and other patients at risk for edema must be considered. Specifically, crystalloids given at a slower rate may be more effective due to the disruptive effects of a fluid bolus on the EG. Our study could provide the rationale basis for the optimal method of volume replacement in normotensive but hypovolemic patients at risk for interstitial edema.
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