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Continuous peripheral resistance measurement during hemorrhagic hypotension
Luciana N Torres1, Ivo P Torres Filho, R Wayne Barbee
1Dept. Physiology,, Virginia Commonwealth University Reanimation Engineering Shock Center, Virginia Commonwealth University Health System, Richmond, Virginia 23298-0401, USA. LNTORRES@vcu.edu
Summary
Continuous monitoring of total peripheral resistance (TPR) in rats undergoing hemorrhagic hypotension revealed that survivors had higher peak TPR values than nonsurvivors. This method accurately tracks critical hemodynamic changes, distinguishing survival outcomes.
Area of Science:
- Physiology
- Cardiovascular Research
- Hemorrhagic Shock Models
Background:
- Prolonged hemorrhagic hypotension (HH) poses significant challenges in critical care.
- Distinguishing between survivors and nonsurvivors (NS) during HH is crucial for effective treatment.
- Intermittent measurements may not capture dynamic physiological changes during HH.
Purpose of the Study:
- To evaluate if continuous total peripheral resistance (TPR) measurements are superior to intermittent data collection.
- To determine if TPR variables can differentiate between survivors and nonsurvivors of prolonged HH.
- To assess the utility of transit-time ultrasound for real-time TPR monitoring.
Main Methods:
- 21 rats underwent 4 hours of HH at 40 mmHg after aortic probe implantation.
- Continuous TPR was measured online using blood flow and arterial pressure recordings.
- Data were collected before, during, and up to 4 hours after HH initiation.
Main Results:
- Continuous TPR measurement successfully detected the maximum TPR (TPRmax), which intermittent data missed.
- Survivors exhibited significantly higher TPRmax values (P <0.005) compared to NS.
- Survivors maintained elevated TPR above baseline for a longer duration than NS (116 ± 20 vs. 51 ± 10 min).
Conclusions:
- High-sampling-rate transit-time ultrasound enables accurate, continuous real-time TPR monitoring.
- Bleeding endpoints and Ringer-Lactate infusion times correlate with time to TPRmax.
- Continuous TPR monitoring, unlike intermittent methods, can reveal differences between survivors and nonsurvivors of HH.