Haemodynamic changes caused in rats by prolonged accelerations

Area of Science:

• Physiology
• Biomedical Engineering
• Aerospace Medicine

Background:

• Understanding physiological responses to acceleration is crucial for aerospace and high-performance environments.
• Previous research indicates potential fluid shifts and tissue damage under G-force exposure.

Purpose of the Study:

• To investigate the effects of sustained 5 Gz acceleration on blood distribution and vascular permeability in rat hind limbs.
• To quantify albumin extravasation and blood volume changes following centrifugation.

Main Methods:

• Rats (n=60) were subjected to 5 Gz acceleration along the longitudinal axis for 1 hour.
• 131I-labelled albumin was administered intravenously prior to centrifugation.
• Radioactivity in hind limb muscles was measured at various time points post-acceleration.

Main Results:

• 5 Gz acceleration induced significant blood displacement to hind limbs and subsequent extravascular albumin leakage.
• A rapid decrease in hind limb blood volume was observed immediately after centrifugation, followed by a slower decline.
• Albumin transudation persisted for several hours, with only partial recovery of normal blood volume within 3 hours.

Conclusions:

• Sustained longitudinal Gz acceleration causes significant hemodynamic alterations, including blood stasis and protein leakage in the hind limbs.
• The observed extravascular albumin leakage indicates increased vascular permeability induced by G-force exposure.
• These findings highlight the potential for tissue edema and compromised vascular integrity following significant acceleration events.