Vascular and hematologic effects of hemorrhage in the chicken

Chickens have been reported to have a rate of posthemorrhagic fluid mobilization twice that of mammals and lack a phase of shock irreversible to transfusion. In the present study we measured several hemodynamic and hematologic parameters in chickens subjected to sustained hemorrhagic hypotension. Total peripheral resistance was unaffected or fell slightly and skeletal muscle vascular resistance judged from changes in gastrocnemius resistance was not affected by hemorrhage. Blood compositional changes included a progressive hyperkalemia, hyperglycemia, and hemodilution as evidenced by linear falls in hematocrit, hemoglobin, and plasma total protein concentration. Plasma sodium and osmolality were unchanged, as were arterial pH and oxygen tension; however, there was a fall in carbon dioxide tension. These studies demonstrate that fluid mobilization in the chicken after hemorrhage does not require an increase in precapillary resistance and suggest that, because the chicken does not exhibit intense precapillary constriction, it is spared some of the deleterious effects of inadequate tissue perfusion. Thus, the findings tend to incriminate the peripheral action of the sympathetic nervous system as a major contributor to the development of irreversibility in other species.