The approximated cardiovascular reserve index complies with haemorrhage related hemodynamic deterioration pattern: A swine exsanguination model

Background To estimate the cardiovascular reserve we formulated the Cardiovascular Reserve Index (CVRI) based on physiological measurements. The aim of this study was to evaluate the pattern of CVRI in haemorrhage-related haemodynamic deterioration in an animal model simulating combat injury. Methods Data were collected retrospectively from a research database of swine exsanguination model in which serial physiological measurements were made under anesthesia in 12 swine of haemorrhagic injury and 5 controls. We calculated the approximated CVRI (CVRI_A). The course of haemodynamic deterioration was defined according to the cumulative blood loss until shock. The ability of heart rate (HR), mean arterial blood pressure (MABP), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) and the CVRI_A to predict haemodynamic deterioration was evaluated according to three criteria: strength of association with the course of haemodynamic deterioration (r² > 0.5); threshold for haemodynamic deterioration detection; and range at which the parameter remained consistently monotonous course of deterioration. Results Three parameters met the first criterion for prediction of haemodynamic deterioration: HR (r² = 0.59), SV (r² = 0.57) and CVRI_A (r² = 0.66). Results were negative for MABP (r² = 0.27), CO (r² = 0.33) and SVR (r² = 0.02). The detection threshold of the CVRI_A was 200–300 ml blood loss whereas HR, SV and CO showed a delay in detection, MABP and CVRI exhibited a wide indicative range toward shock. Conclusions The CVRI_A met preset criteria of a potential predictor of haemorrhage-related haemodynamic deterioration. Prospective studies are required to evaluate use of the CVRI in combat medicine. Level of evidence Level III.