Abstract 29: Heart Rate and Systolic Arterial Pressure Variability during Controlled Hemorrhagic Shock in Rats
OBJECTIVES: The autonomic response to hemorrhagic shock is complex and has been under-investigated. Spectral analyses of RR interval (RRI) and systolic arterial pressure (SAP) have been proposed as an indirect index of autonomic modulation. The objective of this study was to investigate the relationship among hemodynamic variables and autonomic nervous activity presented by the spectral analyses of RRI and SAP during controlled hemorrhagic shock in rats.
METHODS: Twelve Wistar male rats weighing 215±9 g were anesthetized with sodium pentobarbiturate (1.5 mg/kg i.p.). RRI and SAP were recorded continuously and analyzed by wavelet transform using PC soft ware (FlucletTM, Dainippon-Sumitomo Pharma Co., Ltd., Osaka, Japan). Their power spectra were quantified into low-frequency (LF: 0.27– 0.74 Hz) and high-frequency (HF: 0.74–2.00 Hz) components. Baroreceptor sensitivity (BRS) was defined as RRI-LF/SAP-LF. The left carotid artery was cannulated to draw blood (0.1 ml/min) continuously to induce hemorrhagic shock. Spontaneous respiration was kept during this study. Cerebral blood flow (CBF) was measured by Laser flow meter (Advance Co., Ltd., Tokyo, Japan). Statistical analyses were performed by a factor analysis using SPSS15.0J.
RESULTS: During controlled hemorrhagic shock, SAP gradually decreased (0 min: 104±18 mmHg, 20 min: 69±9, 40 min: 60±16, 60 min: 47±7). Factor analysis extracted three major factors: vagal activity, volume status, and sympathetic activity. In the factor extracted as vagal activity, variables which had greater than 0.3 of partial correlation coefficient, were RR-HF (0.98), RR-LF (0.97), and BRS (0.96). Volume status was indicated by SAP (0.92), shed volume (−0.90), CBF (0.62), and SAP-HF (0.61). Sympathetic activity was indicated by SAP-LF (0.89), respiratory rate (0.85), and CBF (0.32).
CONCLUSIONS: Factor analysis extracted autonomic activity and volume status. During hemorrhagic shock, sympathetic activity including arterial sympathetic activity indicated as SAP-LF, which was correlated with respiratory rate, could contribute to maintain CBF, although vagal activity did not affect hemodynamic variables. SAP-HF, represented as respiration related fluctuation of SAP, was indicative of volume status.