Blood clotting defect in hibernating ground squirrels (Citellus tridecemlineatus)

¹ Department of Pathology, University of North Carolina School of Medicine, Chapel Hill, North Carolina

In investigating the hypocoagulability of the blood during hibernation, multiple plasma-clotting factors, numbers of platelets, and hematocrits were determined in 17 hibernating 13-lined ground squirrels and compared with levels in 23 nonhibernating ground squirrels. Human plasma was used as the standard in procoagulant assays. At the time of withdrawal of the blood from the aortas of hibernating animals, their rectal temperatures ranged from 6.9 to 8.6 C. Significant differences between active and hibernating animals were found in the whole-blood clotting times (210 and 315 sec), partial thromboplastin times (45.5 and 109.3 sec), plasma prothrombin (443 and 698 U/ml), 1-hr serum residual prothrombin (27 and 449 U/ml), factor VIII (165 and 35%), factor IX (359 and 188%), and blood platelet concentration (445,150 and 47,940/mm³). No decisive changes were demonstrated in the prothrombin times or levels of factors V, VII, X, XI, XII, or fibrinogen. Inhibitors were not detected. Both thrombocytopenia and plasma defects seemed to contribute to the impairment of the blood-clotting mechanism during hibernation.

Key Words: Hypocoagulability • hypothermia • thrombocytopenia platelets • plasma factor VIII • plasma factor IX • prothrombin • prothrombin conversion

Submitted on June 17, 1963