A nurse cares for a patient who has a sprained ankle. The patient notices that the ankle is swollen, red, and hot to touch.
Which of these explains why the patient's ankle is hot to touch?

Choice A rationale

Exudate accumulation, which is fluid and cells leaking from blood vessels, certainly contributes to the swelling (tumor) associated with a sprained ankle and inflammation. However, the feeling of heat (calor) is primarily a direct result of vasodilation and the subsequent increase in the volume of warm blood flowing into the injured area, raising the local tissue temperature.

Choice B rationale

The cardinal sign of inflammation described as heat (calor) is a direct physiological consequence of arteriolar vasodilation at the site of injury. This increased vascular permeability and localized hyperemia results in a greater volume of warm, oxygenated blood entering the capillary beds of the sprained ankle, which raises the local skin and tissue temperature.

Choice C rationale

An infection is a potential cause of inflammation but is not the mechanism that explains the localized heat. The process of an infection would still trigger the inflammatory response, including vasodilation and increased blood flow, which is the direct cause of the elevated local temperature observed on palpation.

Choice D rationale

A thermal injury, such as a burn, is a type of injury that causes inflammation and heat, but a sprained ankle is a mechanical injury (ligament tear/stretch). In a sprain, the heat is a result of the body's inflammatory response to the tissue damage, not a direct application of external heat or thermal damage itself.

Choice A rationale

Airborne precautions are reserved for diseases with very small particles that remain suspended in the air and travel over long distances, such as tuberculosis, measles, or varicella (chickenpox). Influenza droplets are generally large and do not remain suspended in the air for long periods, falling rapidly, thus requiring droplet precautions instead of the more restrictive airborne type.

Choice B rationale

Contact precautions are used for infections spread by direct or indirect contact with the patient or the patient's environment, such as Clostridium difficile or antibiotic-resistant organisms like MRSA. While contact can spread influenza, the primary route is large respiratory droplets, making droplet precautions the most specific and necessary type of isolation.

Choice C rationale

Influenza is primarily spread by large respiratory droplets expelled when an infected person coughs, sneezes, or talks. These droplets travel a short distance (typically less than 3 to 6 feet) before settling. Droplet precautions, including placing the patient in a private room and requiring staff to wear a surgical mask within the specified distance, are essential to prevent transmission.

Choice D rationale

Universal precautions, now generally referred to as Standard Precautions, involve basic infection control practices like hand hygiene and using personal protective equipment (PPE) for contact with blood, body fluids, non-intact skin, and mucous membranes of all patients. While always used, they are insufficient alone for preventing influenza spread, which requires the added barrier of droplet precautions.