General infections Notes

NOTES NOTES GENERAL INFECTIONS GENERALLY, WHAT ARE THEY? TREATMENT PATHOLOGY & CAUSES ▪ Localized, systemic disorders caused by microbial infections SIGNS & SYMPTOMS MEDICATIONS ▪ Antimicrobials OTHER INTERVENTIONS ▪ Drainage ▪ See individual conditions DIAGNOSIS ▪ See individual conditions ABSCESSES osms.it/abscesses PATHOLOGY & CAUSES ▪ Localized, circumscribed pus collection surrounded by inflamed tissue ▪ May develop in any body region ▫ Superficial (e.g. skin, soft tissue) ▫ Internal (e.g. lung, liver, brain) ▪ Caused by pyogenic bacteria (e.g. S. aureus, S. pyogenes, S. epidermidis, P. aeruginosa) ▪ Bacterial invasion → local inflammatory response ▫ Suppuration (pus production) ▫ Necrosis, liquefaction ▫ Cellular debris accumulation ▪ Loculation, walling off of abscess by adjacent, healthy cells RISK FACTORS ▪ ▪ ▪ ▪ ▪ Trauma Foreign body presence (e.g. body piercing) Intravenous (IV) drug use Dermatological conditions (e.g. cellulitis) Anatomical involvement-related risks ▫ Examples: ascending infection → pelvic abscess, hematologic spread → central nervous system (CNS) abscess, local spread → liver abscess COMPLICATIONS ▪ Spread to other tissue ▪ Fistula formation ▪ Sepsis OSMOSIS.ORG 405

SIGNS & SYMPTOMS ▪ Localized warmth, erythema, swelling, tenderness/pain, induration ▪ Fluctuant mass DIAGNOSIS ▪ History, physical examination: characteristic findings DIAGNOSTIC IMAGING CT scan ▪ Central decreased attenuation area with circumferential enhancement ring MRI ▪ T1: central hypointense area ▪ T2: hyperintense ▪ T1, T2: rim is iso- to hypointense Ultrasound ▪ Internal abscess ▫ Homogeneous fluid collection appears as hypoechoic region within tissue ▫ Edema: cobblestone appearance—thin hyperechoic (dark gray) bands, anechoic (black) fluid Figure 75.1 The clinical appearance of a pilonidal abscess. LAB RESULTS ▪ Ultrasound-guided needle aspiration ▫ Specimen collection, culture TREATMENT MEDICATIONS ▪ Antimicrobials OTHER INTERVENTIONS ▪ Incision, drainage 406 OSMOSIS.ORG Figure 75.2 A CT scan of the brain in the coronal plane demonstrating a cerebral abscess of the left frontal lobe. The abscess shows typical ring enhancement.

Chapter 75 General Infections SEPSIS osms.it/sepsis PATHOLOGY & CAUSES ▪ Serious, life-threatening, systemic infection reaction ▫ Microbial host barrier breach (skin, mucous membranes) → provokes host dysregulated immune response → proinflammatory mediator release (e.g. TNF-α, interleukins) → detrimental physiological effects, tissue damage ▫ Endothelial damage, dysfunction; ↑ vascular permeability; microvascular dysfunction; coagulopathies RISK FACTORS ▪ Bacteremia (most common) Gram-positive organisms ▪ Hospital/intensive care unit (ICU) admission → nosocomial infection ▪ Immune system deficiency ▫ E.g. HIV/AIDS, hematologic malignancy, immunosuppressant medication ▪ Recent surgery/hospitalization → altered microbiome ▪ Indwelling medical device presence ▫ E.g. urinary catheter, venous access device ▪ Bimodal age distribution ▫ Infants, adults ≥ 65 ▪ Community-acquired pneumonia ▪ Chronic disease ▫ E.g. diabetes, heart failure (HF), chronic obstructive pulmonary disease (COPD) ▪ Genetic factors ▪ Respiratory failure ▪ Disseminated intravascular coagulation (DIC) ▪ Metabolic acidosis ▪ Stress ulcer ▪ Treatment complications ▫ E.g. ventilator-associated pneumonia, venous thrombosis ▪ Death SIGNS & SYMPTOMS General presentation ▪ Fever; tachypnea; tachycardia; hypotension; hypoxemia; ↓ urine output; ↓ PaO2; edema; ileus, ↓ bowel sounds ▪ Altered mental status ▫ Malaise, agitation, lethargy, stupor ▪ Signs of shock ▫ E.g. cool skin, cyanosis, ↑ capillary refill, mottling Quick Sequential Organ Failure Assessment (qSOFA) ▪ Score ≥ 2 → ↑ mortality risk ▪ See table COMPLICATIONS ▪ Severe sepsis → septic shock ▫ Sepsis-induced vasodilation, hypotension ▫ Unresponsive to fluid resuscitation ▪ Multiple organ dysfunction syndrome (MODS) OSMOSIS.ORG 407

DIAGNOSIS ▪ History, clinical presentation, physical examination LAB RESULTS Blood studies ▪ ↑ white blood cell (WBC) count, left shift ▪ ↑ C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) ▪ Indications of organ hypoperfusion, injury, dysfunction ▫ ↑ lactate, ↓ platelets (may precede DIC), ↑ glucose, ↑ creatinine, ↑ bilirubin ▪ Coagulation studies ▫ ↑ international normalized ratio (INR), activated partial thromboplastin time (aPTT) ▪ Blood cultures ▫ Identify pathogen TREATMENT MEDICATIONS ▪ Antimicrobials ▫ Initial broad-spectrum antibiotics until pathogen identified ▪ Hemodynamic support ▫ Fluid resuscitation ▫ Vasopressors ▪ Infection prevention ▫ Vaccinations for at risk individuals (influenza, pneumonia) ▪ Complication prevention ▫ Proton pump inhibitor 408 OSMOSIS.ORG SURGERY ▪ Source control ▫ E.g. infected device removal, abscess drainage) OTHER INTERVENTIONS Hemodynamic support ▪ Invasive monitoring Respiratory support ▪ Supplementary oxygen; mechanical ventilation Infection prevention ▪ Infection control practices ▫ ↓ hospital-acquired infections (ventilator-associated pneumonia, catheter-associated bloodstream infections) Complication prevention ▪ Deep-vein thrombosis prophylaxis ▪ Glycemic control