Systemic Inflammatory Response Syndrome (SIRS) is characterized by a systemic inflammatory state commonly triggered by infections, including surgical site infections. One of the key clinical features is tachycardia, reflecting the body's systemic response to stress and inflammation. Tachycardia helps maintain adequate tissue perfusion and oxygen delivery during the heightened metabolic demand caused by infection. In contrast, bradycardia is not typical, and while hypothermia or leukopenia may occur, they are not defining or consistent features. Recognizing tachycardia in a surgical patient is crucial for early diagnosis and management of SIRS to prevent progression to sepsis.

Reference: Sabiston Textbook of Surgery, 21st Edition.