Hypertonic cardiopulmonary bypass primes and endothelial damage

The objective of this study was to investigate whether hypertonic hyperosmolar primes solution (HHPS), with an osmolarity of 2300 mOsmol/L, causes endothelial damage/loss. The bodies' normal osmolarity is -280 mOsmol/L. Aortic endothelial cells were cultured and plated to confluence, confirmed by light microscopy, on a 96-well plate. Serial dilutions of HHPS (n = 10) were incubated with the cells (n = 160) for 1 hour. The plates were agitated to simulate flow that occurs during cardiopulmonary bypass (CPB). One half the cells (n = 80) were stained with crystal violet to provide a visual analogue of cell survival. The second half of the cells had the HHPS removed and replaced with culture medium and were incubated overnight before being stained with crystal violet. Optical densities were measured using an optical plate reader set at 470 nm. Analysis of the endothelium after 1 hour showed that HHPS (2300 mOsmol/L) and water (positive control for 100% cell death) resulted in equal cell death, which was significantly higher (p < .05) than any of the other osmolarities tested for. There was no significant difference in the endothelial death rates for osmolarities between 260 and 400 mOsmol/L. Results of overnight incubation showed that cells in contact with a solution of osmolarity >320 mOsmol/L resulted in a significantly greater endothelial cell death rate (p < .05). Our results indicate that the endothelium can be irreversibly damaged by HHPS with osmolarities >320 mOsmol/L. The experimental protocol showed that this endothelial damage, which obviously occurs at the time of contact with the HHPS, may only become manifest 24 hours later.