PURPOSE: Nonlinear analysis of hemodynamic parameters may provide insight not available from standard linear measures such as heart rate and blood pressure. We have previously shown decreased heart rate and blood pressure variability during sepsis. We hypothesized that surgical stress decreases hemodynamic volatility in the post-operative period.
METHODS: Radio-transmitters were implanted into the ascending aorta of C57/BL6 mice (n=31) for continuous hemodynamic monitoring. Continuous heart rate and blood pressure recordings were taken for 24hr following implantation (Post-Operative). Following 72 hours of recovery, recordings were taken for 24 hours (Baseline). Sepsis was induced by cecal ligation and puncture and recordings taken for 24 hours (Sepsis). Heart rate volatility (HRV) and blood pressure volatility (BPV) measurements (% of 5-minute standard deviations < cutoff, defined as lowest 5% during baseline) were compared among groups.
RESULTS: Low BPV was found during 8.4% of post-operative intervals (p<0.001 vs. baseline) and during 30.9% of sepsis intervals (p<0.001 vs. baseline and vs. post-operative). Mean arterial pressure (MAP) was 112 mm Hg at Baseline and 104 mm Hg Post-Operative. Low HRV was found during 21.2% of intervals post-operative (p<0.001 vs. baseline) and 72.7% of intervals during sepsis (p<0.001 vs. baseline and vs. post-operative). Mean heart rate was 530 beats per minute (bpm) at Baseline and 569 bpm post-operative. In 9 animals followed to recovery from surgery, low HRV was found during >40% intervals in the first 8 hours before gradually returning to baseline at 28 hours. Low BPV was found in >10% of intervals between hours 12-52 post-op before returning to baseline.
CONCLUSIONS: Hemodynamic volatility significantly decreases following surgical stress, but to a lesser extent than during sepsis. Blood pressure and heart rate did not change at this time; therefore, nonlinear measures were more sensitive indicators of stress.
CLINICAL IMPLICATIONS: Surgical stress might predispose to secondary cardiovascular insults. Measurement of volatility in the post-operative period may be a useful method to assess cardiovascular recovery from surgical stress.
DISCLOSURE: The following authors have nothing to disclose: Michael Kwiatt, Joe LaChant, Sergio Zanotti, Steven Hollenberg
No Product/Research Disclosure Information