Effect of pneumatic tourniquet application to the distal extremities of the horse: blood gas, serum electrolyte, osmolality, and hematologic alterations.

The study investigates the impact of using a pneumatic tourniquet on a horse’s limb for 120 minutes. It found that while this caused some chemical and physiological changes in the treated limb, these effects largely reversed within 15 minutes of removing the tourniquet.

Research Context and Methodology

• The study was conducted to investigate the effects of pneumatic tourniquet application on the distal extremity (far end limb) of a horse, for a period of 120 minutes.
• The focus was on examining several physiological parameters including blood gas levels, serum electrolyte concentrations, osmolality (concentration of a solution), and alterations in the blood composition (hematocrit values) in the tourniqueted limb vein (TLV).
• These attributes were compared to their values in the control leg, i.e., an untreated limb of the same animal.

Findings of the Study

• Application of the tourniquet resulted in local venous acidemia, which is an abnormal decrease of pH in the blood emanating from the tourniquet-clad limb.
• It also led to an increase in serum potassium (K+) concentrations, meaning that more of this electrolyte was found in the blood serum of the treated limb compared to the control.
• However, the changes observed in the plasma total solids, sodium (Na+), and osmolality were minimal, suggesting that these attributes did not significantly get affected by the tourniquet application.
• The hematocrit values, which measure the proportion of blood volume that is taken up by red blood cells, apparently reduced when compared to the control leg.

Results After Tourniquet Removal

• Upon release of the tourniquet after the 120-minute period, the packed cell volume (PCV, another name for hematocrit) and the partial pressure of oxygen (PO2) in the TLV promptly returned to their base line, mirroring the values in the untreated limb.
• However, the blood pH, partial pressure of carbon dioxide (PCO2), and potassium concentrations in the TLV required between 10 and 15 minutes to return to their baseline levels.
• This indicates that the effect of tourniquet application on these parameters is significantly reversed in a relatively short period after its removal.