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 (CVRIA). 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 CVRIA 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 CVRIA (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 CVRIA 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 CVRIA 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.
Keywords: Cardio-Vascular Reserve Index (CVRI); Haemodynamic deterioration; Haemorrhage; Shock; Swine model.