The natural leukocyte response to hemorrhagic shock.

There is a high incidence of bacterial infection in patients after trauma or hemorrhagic shock. Since circulating white blood cells (WBC) are a vital component of host defense mechanisms, we examined leukocyte responses in canine hemorrhagic shock. Twenty adult mongrel dogs were anesthetized with 28.6 mg/kg of IV pentobarbital. Arterial and venous cannulas were inserted, and after baseline hemodynamic and blood determinations the dogs were rapidly bled into a reservoir to a mean arterial pressure of 45 +/- 3 mmHg. The animals were maintained at this pressure for one hour and then resuscitated with twice the volume of shed blood over two hours using Ringer's lactate solution. Serial WBC counts after shock were compared to baseline values using Student's t test. In the first few hours after hemorrhagic shock the total WBC count falls, while the neutrophil population rises significantly. During the first week following shock and resuscitation, the leukocyte count remains elevated due to a persistent increase in the neutrophil population. The lymphocyte count remains depressed. Therefore, changes in the number of WBC after canine hemorrhagic shock do not favor the development of bacterial sepsis, because the neutrophil count remains elevated. Whether or not neutrophil function is adequate remains to be determined.