Metabolic component of intestinal PCO(2) during dysoxia

Area of Science:

• Physiology
• Biochemistry
• Critical Care Medicine

Background:

• Intestinal perfusion adequacy during shock and resuscitation is crucial for patient outcomes.
• Tissue acid-base balance offers a potential method for assessing intestinal perfusion.
• Distinguishing between respiratory (CO2-related) and metabolic (lactate-related) acid-base changes is key.

Purpose of the Study:

• To examine the feasibility of estimating intestinal tissue acid-base balance.
• To differentiate respiratory from metabolic acid-base disturbances in the intestine.
• To quantify the buffering of lactate's hydrogen ions (H+) by bicarbonate (HCO3-) and non-bicarbonate anions (A-) in anoxic intestinal tissue.

Main Methods:

• Anesthetized swine intestinal segments were compressed in a steel pipe to induce anoxia.
• Measurements of partial pressure of carbon dioxide (PCO2) and lactate were taken at 5- to 10-minute intervals.
• Kinetic analysis was used to determine the rate of change and half-time for PCO2 and lactate.

Main Results:

• Lactate and PCO2 increased over time, following first-order kinetics with a half-time of approximately 22 minutes.
• The relationship between PCO2 and lactate was linear.
• Approximately half of the lactate's H+ was buffered by tissue bicarbonate (HCO3-) and half by non-bicarbonate anions (A-).

Conclusions:

• The respiratory and metabolic components of tissue acidosis can be distinguished in the intestine.
• Estimating tissue buffer base from measured pH and PCO2 can provide insights into intestinal perfusion adequacy.
• Findings support the use of tissue acid-base balance for monitoring shock and resuscitation.