Final answer:
Thrombocytopenia is the laboratory indicator that suggests sepsis as a cause of shock, as it is associated with septic shock, which results from an overwhelming response to infection.
Step-by-step explanation:
The nurse suspects sepsis as a cause of shock when the laboratory test results indicate thrombocytopenia. Thrombocytopenia, which is a reduced platelet count, is commonly associated with septic shock. Septic shock is a severe and potentially fatal condition caused by an overwhelming immune response to a bacterial infection in the bloodstream, leading to low blood pressure and multiple organ failure. Laboratory results showing thrombocytopenia can be indicative of widespread clotting within the vessels, a complication seen in severe sepsis or septic shock. Other clinical findings that can support a diagnosis of septic shock include fever, hypotension, increased heart rate, altered mental status, and signs of organ dysfunction such as increased blood urea nitrogen (BUN).