Recent clinical reports suggest that newborn infants with polycythemia and other causes of hyperviscosity may be at risk for developing necrotizing enterocolitis (NEC). This study evaluates the relationship of polycythemia and increased blood viscosity on survival and bowel integrity and an ischemic bowel model in rats. Ninety nine weanling Sprague Dawley rats underwent one-minute occlusion of the superior mesenteric artery. Animals were divided into five treatment groups. Group 1 (n=40) ischemic controls had a mean hematocrit (HCT) of 44.3±3.3%. Group 2 (n=19) rats were transfused with whole blood from donor rats followed by a dose of lasix (2mg/kg) intravenously (IV) 20 hours prior to ischemic injury, raising the HCT to 53.6±3.2%. Group 3 (n=19) animals were transfused with whole blood × 2 and given lasix at 20 and 4 hours before operation, raising the HCT to 63.0±1.6%. Group 4 (n=16) (HCT 68.6±2.55%) and group 5 (n=15) rats (HCT 71.6±2.07%) were prepared with multiple blood transfusions and given lasix as group 3 animals to achieve those hematocrit levels. Animals were kept in individual cages and fed rat chow and water ad libitum. Survival, length of survival, and evidence of bowel perforation or necrosis were recorded at seven days following the ischemic insult. Blood viscosity was determined in each group. Survival at one week was 65% in group 1, 63% in group 2, and 63% in group 3. Survival was significantly decreased in group 4 to 31% (P<.05 v groups 1,2, and 3) and in group 5 to 0% (P<.002 v groups 1,2, and 3). The mean length of survival (in days) was 5.7±2.0 in group 1, 5.3±2.4 for group 2, 6.0±1.7 in group 3, 4.1±2.29 in group 4 (P<.02 v groups 1-3), and was lowest in group 5, 2.2±.44 (P<.001 v all groups). The perforation rate was similar among all of the experimental groups. The incidence of ischemic gut was 20% for group 1, 26.3% for group 2, 15.7% for group 3, 50% for group 4, and 80% for group 5 (P<.025 v groups 1-3). The relative blood viscosity in group 1 was 2.84±.27; group 2,3.59±14 (P<.001 v group 1); group 3 6.24±.66 (P<.001 v groups 1 and 2); and group 4 7.96±3.49 (P<.02 v groups 1 and 2). These observations suggest a direct relationship between mortality, the incidence of bowel ischemia, polycythemia and blood viscosity in this animal model. Hematocrit levels greater than 65% resulted in a higher animal mortality and a more extensive ischemic injury. These findings imply that plasmaphoresis or other methods to reduce the hematocrit level to 55% may be beneficial in the clinical setting in selected subjects with significant polycythemia who are considered at risk for NEC.
- necrotizing enterocolitis
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health