Final answer:
Infection in tissue leads to a decreased pH, which diminishes the effect of local anesthetics due to the acidic environment inhibiting their ability to block pain signals.
Step-by-step explanation:
The presence of infection in the tissue causes a decrease in the pH of the tissue, which in turn diminishes the effect of local anesthetics. An infection commonly leads to an inflammatory response, resulting in the production of various acids, such as lactic acid, thereby lowering the pH. A more acidic pH environment can reduce the efficacy of local anesthetics, as they typically require a more neutral to slightly alkaline pH to penetrate nerve membranes effectively and block pain signals.
This decrease in pH can be represented as option 'd' from the given selections, which states a decreased pH, increased pCO2, and increased HCO3-. This reflects the body's attempt to compensate for the acidosis through respiratory and renal adjustments.
It's important to monitor the pain sensation and the presence of skin lesions, as these can increase susceptibility to secondary injuries and infections with other pathogens, complicating the overall clinical picture and potentially requiring additional interventions.