Splenic storage volume in the unanesthetized resting beagle

Area of Science:

• Veterinary Physiology
• Hematology
• Cardiovascular Physiology

Background:

• Determining splenic storage volume in dogs non-surgically is challenging.
• Radioisotope methods for circulating red blood cell volume are hindered by splenic uptake.
• Accurate red cell volume calculation requires correcting large vessel hematocrit for uneven distribution.

Purpose of the Study:

• To develop a method for determining the red blood cell distribution correction factor in intact dogs.
• To quantify splenic red blood cell storage in resting and exercising beagles.
• To assess physiological changes during maximal exertion.

Main Methods:

• Utilizing severe exercise to "physiologically splenectomize" intact dogs.
• Measuring plasma volume and large vessel hematocrit before and during exercise.
• Comparing results with splenectomized dogs where splenic function was simulated.

Main Results:

• A method was established to determine the correction factor in intact, exercising dogs.
• In unanesthetized resting beagles, approximately one-third of erythrocytes are stored in the spleen.
• Maximal exertion led to significant increases in large vessel hematocrit and plasma osmolarity, with a decrease in plasma volume.

Conclusions:

• Severe exercise provides a viable method to estimate red blood cell distribution factors in intact dogs.
• The spleen plays a significant role in erythrocyte storage in resting beagles.
• Physiological responses during maximal exertion include hemoconcentration and altered fluid balance.