The vascular-interstitial pH gradient during and after hemorrhagic shock

Area of Science:

• Physiology
• Biochemistry
• Shock Research

Background:

• Hemorrhagic shock (HS) induces metabolic acidosis, significantly impacting physiological parameters.
• The interstitial fluid space (IFS) role in buffering acidosis during HS is not fully understood.
• Prenodal skin lymph serves as a surrogate for interstitial fluid space monitoring.

Purpose of the Study:

• To investigate the interstitial fluid space's response to hemorrhagic shock-induced metabolic acidosis.
• To compare interstitial fluid space parameters with central venous blood parameters during shock and resuscitation.
• To elucidate the mechanisms by which the IFS maintains homeostasis during acidosis.

Main Methods:

• Utilized a canine model of hemorrhagic shock and resuscitation.
• Monitored prenodal skin lymph and central venous blood parameters (pH, pO2, pCO2, HCO3, flow rate).
• Compared measurements taken before shock, during shock, and post-resuscitation.

Main Results:

• Hemorrhagic shock induced significant metabolic acidosis in venous blood (pH decreased to 7.16-7.03).
• Prenodal skin lymph pH remained stable at physiological levels (7.51) throughout shock and resuscitation.
• Skin lymph oxygen tension (pO2) was maintained, contrasting with a sharp decrease in mixed venous pO2.

Conclusions:

• The interstitial fluid space demonstrates remarkable stability in pH and pO2 during hemorrhagic shock-induced acidosis.
• Stoichiometric changes within the IFS likely facilitate protein adherence, preserving cellular homeostasis.
• These findings highlight the IFS's critical role in mitigating the effects of acidosis during shock.