Effects of analgesic use on inflammation and hematology in a murine model of venous thrombosis

Abstract

Venous thrombosis (VT) is a significant cause of morbidity and mortality in humans. Surgical animal models are crucial in studies investigating the pathogenesis of this disease and evaluating VT therapies. Because inflammation is critical to both the development and resolution of VT, analgesic medications have the potential to adversely affect multiple parameters of interest in VT research. The objective of this study was to determine how several common analgesics affect key variables in a murine ligation model of deep vein thrombosis. Male C57BL/6 mice were randomly assigned to receive either local (bupivacaine) or systemic parenteral analgesia (buprenorphine, tramadol, or carprofen) or 0.9% NaCl (control). All mice underwent laparotomy and ligation of the inferior vena cava, and treatment was continued until euthanasia at 6 or 48 h after surgery. Analysis of harvested tissues and blood included: hematology, thrombus weight, serum and vein-wall cytokines (IL1β, IL6, IL10, TNFα), soluble P-selectin, and vein-wall leukocyte infiltration. Compared with 0.9% NaCl, all of the analgesics affected multiple parameters important to VT research. Carprofen and tramadol affected the most parameters and should not be used in murine models of VT. Although they affected fewer parameters, a single dose of bupivacaine increased thrombus weight at 6 h, and buprenorphine was associated with reduced vein wall macrophages at 48 h. Although we cannot recommend the use of any of the evaluated analgesic dosages in this mouse model of VT, buprenorphine merits additional investigation to ensure the highest level of laboratory animal care and welfare.

Figure 1.

Allocation of mice to experimental groups. For each group, 30 mice were divided equally between 2 time points and then further assigned according to the type of tissue and blood sample that was collected for analysis.

Figure 2.

Significant differences in (A) Hct at 48 h are eliminated when (B) Hct is normalized to surgery time (s). (C) The Hct at 48 h shows an inverse correlation with the duration of surgery (P = 0.0167) Treatment groups are no analgesia (NA), bupivacaine (BV), buprenorphine (BR), tramadol (TR), and carprofen (CA). Results are reported as median and interquartile range.