Scientific Publications by FDA Staff

Shock 2015 Feb 13 [Epub ahead of print]

Evaluation of Heart Rate and Blood Pressure Variability as Indicators of Physiological Compensation to Hemorrhage Prior to Shock.

Scully CG, Kramer GC, Strauss DG

Individual responses to hemorrhage vary, with varying periods of compensation before the development of shock. We characterized heart rate and blood pressure variability measures during a hemorrhage of 25 ml/kgBody-Weight over 15 minutes in conscious sheep (N=7, 14 total hemorrhages) as markers of the transition from compensated to decompensated shock using the continuous wavelet transform. Heart rate-low frequency (HR-LF) and systolic blood pressure-low frequency (SBP-LF) indices were developed to represent the change in spectral power during hemorrhage as low frequency [0.06 - 0.15 Hz] power divided by the sum of high [0.15 - 1.0 Hz] and very low frequency [0.02 - 0.06 Hz] power. Heart rate rose from 96.3 (22.2) BPM (mean (standard deviation) across all trials) to a peak of 176.0 (25.4) BPM occurring at a minimum time of 5.3 minutes to a maximum of 22.1 minutes (11.7 (1.6) minutes), depending on the trial, after the start of hemorrhage. During the heart rate compensated response to hemorrhage there was elevated HR-LF and SBP-LF in 5 of the 7 animals. In these animals, HR-LF and SBP-LF dropped to below baseline levels around the time of the peak heart rate. The results from this conscious animal study suggest that heart rate and systolic blood pressure low frequency power rise during the compensation phase of the response to hemorrhage in conscious sheep. Use of variability monitoring could aid in describing an individual's current response to hemorrhage and anticipation of impending decompensation; however individual differences in the response limits this potential.