Infection occurs when a pathogenic microorganism (a bacterium, virus, fungus, or parasite capable of causing disease) enters the body, multiplies within living tissue, and triggers an immune response. The body defends itself through inflammation (increased blood flow, immune cell recruitment, and chemical mediators) and other immune mechanisms designed to contain and eliminate the invading organism.
In cardiac care and critical illness, infections are common and serious complications. Patients in the intensive care unit following cardiac arrest are at elevated risk due to compromised immune function, invasive lines and catheters (which provide a route for microorganisms to enter the body), mechanical ventilation (which bypasses normal upper airway defences), and immobility. Common infections in this setting include ventilator-associated pneumonia, central line-associated bloodstream infection, and catheter-associated urinary tract infection.
Sepsis is the life-threatening condition that occurs when the body’s response to infection becomes dysregulated and begins to damage its own organs. Septic shock (sepsis with cardiovascular collapse) can lead to cardiac arrest. Cardiac patients who develop fever, new haemodynamic instability, or unexplained deterioration should be assessed promptly for infection.
Management of infection requires identifying the causative microorganism (by blood cultures before starting antibiotics), choosing appropriate antimicrobial therapy, and addressing the source. In patients with implanted cardiac devices such as pacemakers or ICDs, device infection is a particularly serious complication often requiring device explantation alongside prolonged antibiotic treatment.
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