Infections in Older Adults

Aka: Infections in Older Adults, Systemic Infections in Elderly Patients, Elderly with Systemic Infections, Geriatric Infectious Disease

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II. Epidemiology

  1. Infections cause the majority of hospitalizations in patients over age 65 years
  2. Infections cause 30% of deaths in over age 65 years
  3. Risk of death in over age 65 years compared with younger patients
    1. Pneumonia: 3x
    2. Urinary Tract Infection: 5-10x
    3. Appendicitis: Elderly account for 60% of Appendicitis deaths

III. Precautions

  1. Bacterial Infections represent 95% of systemic infections in elderly
    1. Consider Viral Infection only as a diagnosis of exclusion
  2. Presenting signs and symptoms are typically non-focal and atypical for underlyng infection in the elderly
    1. Pneumonia in the Elderly
      1. In up to 65% of Pneumonia cases, presents with no fever, cough, Shortness of Breath or Chest Pain
    2. Intra-Abdominal Infection in Older Patients
      1. Classic signs (e.g. Abdominal Pain) are typically absent in the elderly
        1. Present in only a third of Acute Cholecystitis, Appendicitis and Diverticulitis cases
        2. Abdominal tenderness is absent in 65% of elderly with intra-abdominal infections
      2. Exercise a low threshold for diagnostic imaging (e.g. CT Abdomen or RUQ Ultrasound)
    3. UTI in Older Adults
      1. Classic symptoms and diagnostic tests (Urinalysis) are unreliable in the elderly
        1. See UTI in Older Adults for diagnosis
        2. Combined negative Urine Leukocyte Esterase and urine nitrite Negative Predictive Value of 88%
        3. Dysuria with abnormal urine findings is most suggestive of urinary tract source
      2. Asymptomatic Bacteriuria is common in the elderly (as high as 40%)
        1. Consider other causes of Altered Level of Consciousness or Sepsis
        2. Other causes should especially be considered when presentation is not classic for UTI
    4. Laboratory testing
      1. Urinalysis, Chest XRay and Blood Cultures identify infectious source in only 70% of cases
      2. Blood Cultures are positive in only 10% of cases
  3. Elderly patients present unique challenges
    1. Multiple comorbid conditions including Dementia
    2. Multi-drug resistant pathogen exposures (long-term care facilities, frequent hospitalizations, indwelling lines)
    3. Decreased physiologic reserve
    4. Decreased host defenses and immune response
    5. Altered Pharmacokinetics in elderly patients
      1. See Medication Use in the Elderly
      2. See Drug Dosing in Chronic Kidney Disease
      3. See Prolonged QT Interval due to Medication

IV. Symptoms: Typically non-specific even in overwhelming infection

  1. Confusion (30-60%)
    1. Cognitive Impairment
    2. Altered Level of Consciousness
    3. Delirium (50%)
  2. Functional status decreased (35%)
  3. Anorexia or Failure to Thrive
    1. See Failure to Thrive in the Elderly
  4. Chronic comorbid condition exacerbation (e.g. COPD exacerbation, CHF exacerbation)
  5. Falls
  6. Generalized weakness

V. Signs: Fever

  1. Atypical febrile response in the elderly
  2. Fever when present is specific for infection
    1. Test Specificity: >90%
  3. Fever has poor Test Sensitivity for bacteremia in the elderly
    1. Elderly with bacteremia report fever in <20% of cases
    2. Elderly with bacteremia have fever in emergency department in only 70-85% of cases
  4. Fever cut-offs with better sensitivity in the elderly
    1. Systemic infection: 37.2 (99 F)
      1. Temperature over 38.3 C (101 F) in the elderly suggests severe infection
      2. Hypothermia associated with systemic infection is an ominous sign in the elderly
    2. Temperature rise of 1.1-1.3 C (2.0-2.4 F) over baseline
      1. Temperature baseline decreases with aging (as much 1.5 C per decade)

VI. Signs: Red Flag findings suggestive of more serious infection

  1. Temperature over 38.3 C (101 F) or Hypothermia
  2. Tachypnea (may be only slightly increased)
  3. Vomiting
  4. Altered Level of Consciousness
  5. Band Neutrophil predominance >6%

VII. Causes: Common Serious Infections in Older Patients

  1. Urinary Tract Infections (25-55%)
  2. Respiratory Infections (10-34%)
    1. See Pneumonia in the Elderly
    2. Influenza
  3. Infections with unknown source (11-31%)
  4. Intraabdominal Infections (9-20%)
    1. See Intra-Abdominal Infection in Older Patients
    2. Diverticulitis
    3. Clostridium difficile
    4. Acute Cholecystitis
    5. Appendicitis
    6. Peptic Ulcer Disease
    7. Small Bowel Obstruction
  5. Skin Infections (9%)
    1. See Cellulitis
    2. See Pressure Ulcer
    3. Herpes Zoster (Shingles)
    4. Methicillin-Resistant Staphylococcus aureus (MRSA)
    5. Vancomycin-Resistant Enterococcus (VRE)

VIII. Evaluation: History and Examination

  1. Chronic medical conditions predisposing to infection
    1. Diabetes Mellitus
    2. Peripheral Vascular Disease
    3. Chronic Renal Failure
    4. Dysphagia with risk of Aspiration Pneumonia
  2. Immunosuppressant medications
    1. Corticosteroids
    2. Chemotherapy
    3. Antibiotics
  3. Immobility (risk for Decubitus Ulcers)
  4. Nutritional deficiency
  5. Neurologic Exam with Mental Status Examination
  6. Dermatologic infections
  7. Pulmonary symptoms

IX. Labs

  1. Complete Blood Count
    1. Leukocytosis present in 60% with serious infection
  2. Urinalysis and Urine Culture
  3. Serum chemistry (basic metabolic panel) including Serum Creatinine
  4. Serial Lactic Acid
  5. Blood Culture
  6. Sputum Culture

X. Imaging

  1. Chest XRay
  2. CT Abdomen and Pelvis

XI. Diagnosis

  1. See Systemic Inflammatory Response Syndrome (SIRS)

XII. Management

  1. Disposition
    1. Exercise a low threshold for admission in the elderly
  2. Manage Septic Shock aggressively
    1. See Septic Shock
  3. Supportive Care
    1. Antipyretics
    2. Intravenous FluidResuscitation
  4. Treat specific conditions
    1. Pneumonia in the Elderly
    2. Intra-Abdominal Infection in Older Patients
    3. Urinary Tract Infection
    4. Cellulitis

XIII. Prevention

  1. Respiratory infection prevention
    1. Pneumococcal Vaccine
    2. Influenza Vaccine
  2. Urinary Tract Infection prevention
    1. Limit Urinary Catheters
    2. Apply Topical Estrogen to vulva and vagina in women
    3. Treat Benign Prostatic Hypertrophy in men

XIV. References

  1. Khoujah (2013) Crit Decis Emerg Med 27(4): 12-21
  2. Adedipe (2006) Emerg Med Clin North Am 24(2): 433-48 [PubMed]
  3. Caterino (2008) Emerg Med Clin North Am 26(2):319-43 [PubMed]
  4. Fraser (1997) J Gerontol Nurs 23:5-10 [PubMed]
  5. Mouton (2001) Am Fam Physician 63:257-68 [PubMed]

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