14.1 Geriatric Syndromes, Polypharmacy & Atypical Disease Presentations

14.1 Geriatric Syndromes, Polypharmacy & Atypical Disease Presentations

Clinical Scenario: An 82-year-old female with hypertension, vascular dementia, and osteoporosis is admitted to the ICU from assisted living following an unwitnessed fall, progressive lethargy, and anorexia over 24 hours. Vital signs: temperature 35.8°C (96.4°F), HR 86 bpm, BP 94/56 mmHg (MAP 69 mmHg), RR 22 breaths/min, and SpO2 94% on room air. Physical exam reveals hypoactive delirium (CAM-ICU positive), dry mucous membranes, and mild suprapubic fullness without abdominal guarding or rigidity. Labs: WBC 6,400/mcL with 16% band forms (left shift), BUN 28 mg/dL, and serum creatinine 0.6 mg/dL. Baseline weight is 48 kg. Home medications include diphenhydramine 25 mg nightly, alprazolam 0.5 mg twice daily, sliding-scale regular insulin, and omeprazole 40 mg daily. The acute care nurse practitioner must evaluate multiorgan reserve, assess kidney function beyond serum creatinine alone, identify high-risk Beers medications, and manage an atypical presentation of sepsis.

Normal Physiologic Changes of Aging & Functional Reserve

Aging diminishes homeostatic reserve across organ systems, narrowing the physiological safety margin during acute critical illness:

• Cardiovascular: Arterial stiffening from elastin loss and collagen cross-linking elevates pulse wave velocity and systolic blood pressure, widening pulse pressure. Concentric left ventricular remodeling and delayed myocyte relaxation impair early passive diastolic filling (reversing the normal E/A ratio), making cardiac output highly dependent on late atrial contraction ("atrial kick"). New-onset atrial fibrillation with rapid ventricular response frequently precipitates pulmonary edema and hemodynamic collapse. Progressive sinus node loss and beta-1 adrenergic receptor down-regulation blunt maximal heart rate and inotropy during shock.
• Pulmonary: Loss of alveolar elastic recoil increases lung compliance and residual volume, while costochondral stiffening reduces chest-wall compliance. Closing volume exceeds functional residual capacity (FRC) in the supine position, producing dependent airway closure during tidal breathing that worsens ventilation-perfusion ($V/Q$) mismatch and baseline hypoxemia. Ventilatory responses to hypoxemia and hypercapnia may be blunted, while depressed cough and mucociliary reflexes elevate aspiration and pneumonia risk.
• Renal & Sarcopenia Trap: Sarcopenia (loss of skeletal muscle mass) decreases daily creatinine generation. Consequently, an elderly patient with severe renal impairment often exhibits a misleadingly "normal" serum creatinine (0.6–0.8 mg/dL). Cockcroft–Gault estimates creatinine clearance and remains the dosing method specified for many medications: $\text{CrCl (mL/min)} = \frac{(140 - \text{Age}) \times \text{Weight (kg)}}{72 \times \text{Serum Creatinine (mg/dL)}} \times (0.85\text{ if female})$ For the 82-year-old woman, estimated CrCl is 54.8 mL/min at 48 kg or 45.6 mL/min at 40 kg. These are estimates, and severe muscle wasting can make either value too high. When dosing depends on an accurate estimate, consider combined creatinine–cystatin C eGFR or measured kidney function and monitor drug concentrations and renal trends.
• Hepatic: Liver mass and hepatic blood flow decline with age. Clearance of some phase I drugs may decrease, prolonging exposure to agents such as diazepam and midazolam; the effect varies by drug and patient. Conversely, Phase II conjugation (glucuronidation) is preserved, making Phase II agents (lorazepam, oxazepam) preferable when sedatives cannot be avoided.

Pharmacokinetics & Pharmacodynamics in Geriatric Critical Care

• Volume of Distribution ($V_d$): Total body water generally decreases with age. Hydrophilic drugs (aminoglycosides, vancomycin, digoxin) distribute into a smaller volume, generating high peak concentrations ($C_{\text{max}}$) after standard loading doses. Conversely, relative adipose tissue generally increases, expanding $V_d$ for lipophilic drugs (fentanyl, midazolam, propofol, amiodarone) and prolonging elimination half-life ($t_{1/2}$), resulting in drug accumulation and delayed awakening.
• Protein Binding & Sensitivity: Hypoalbuminemia can increase the unbound fraction of highly protein-bound drugs such as phenytoin, making total levels misleading. Interpret exposure using clinical response and free levels when indicated. Older adults are often more sensitive to opioids, sedatives and anesthetics.

The AGS Beers Criteria: Critical Care High-Risk Medications

The American Geriatrics Society (AGS) Beers Criteria identifies high-risk medications whose harms generally outweigh benefits in older adults:

Dementia and Superimposed Delirium

Dementia involves acquired cognitive decline that interferes with independent daily function. Obtain collateral history about baseline cognition, ADLs/IADLs and time course; combine a validated cognitive assessment with neurologic examination, medication review, targeted laboratory testing and structural brain imaging. A test score alone does not establish the diagnosis. Sudden fluctuating inattention in a patient with dementia suggests superimposed delirium and needs an acute-cause evaluation. Rapidly progressive or atypical decline warrants specialist referral. Care planning addresses medication support, falls, driving/home safety, caregiver burden and the patient's preferences. Assess decision-making capacity for the particular decision; dementia does not automatically remove all capacity.

Atypical Presentations of Acute Illness

Older adults frequently present without textbook hallmarks of acute pathology:

• Severe Sepsis: Fever and leukocytosis may be absent. Hypothermia, bandemia, acute delirium or functional decline can signal serious infection. Assess perfusion and organ dysfunction, investigate the source and evaluate other causes of delirium; a positive urinalysis alone does not establish urosepsis.
• Acute Coronary Syndromes (ACS): In SILVER-AMI, 44% of patients aged $\ge 75$ years with acute MI did not report chest pain as their primary symptom. Common presentations include new-onset dyspnea, acute pulmonary edema, unexplained syncope, profound fatigue, nausea, or sudden functional decline.
• Silent Peritonitis: Loss of abdominal wall musculature and blunted visceral peritoneal pain perception obscure classic findings. Perforated diverticulitis, appendicitis, or mesenteric ischemia may manifest without abdominal rigidity, fever, or rebound tenderness.

Osteoporosis and Fragility Fractures

In postmenopausal women and men aged 50 or older, DXA T-score at or below −2.5 supports osteoporosis; a T-score between −1.0 and −2.5 is osteopenia. A hip or vertebral fragility fracture warrants osteoporosis treatment assessment regardless of DXA. For osteopenia, US treatment thresholds include a 10-year FRAX hip-fracture risk of at least 3% or major osteoporotic-fracture risk of at least 20%. Evaluate secondary causes, calcium/vitamin D adequacy, medication risks and falls. Arrange fracture-prevention therapy and follow-up after acute stabilization; selecting an antiresorptive or anabolic agent depends on fracture risk, renal function and contraindications.

Maltreatment, Neglect and Protection

Unexplained injuries, conflicting histories, fear of a caregiver, poor hygiene, untreated illness or unusual financial changes can signal abuse, neglect or exploitation. A warning sign warrants assessment; it does not prove abuse. Speak with the patient privately, using appropriate communication support, and document objective findings and the patient's account. Treat urgent injuries and establish immediate safety. Involve social work and the appropriate adult protective services or law-enforcement pathway; reporting duties and definitions vary by state and patient circumstances. Do not require proof before making a legally required report. Make a protection/discharge plan with the patient, respecting a capable adult's right to refuse services.

Frailty Syndrome, Assessment Tools & Acute Care Risk Calculus

Frailty is a biological syndrome of decreased physiological reserve across multiple organ systems:

• Fried Frailty Phenotype: Evaluates 5 physical components: unintentional weight loss (>10 lbs in past year), exhaustion, slow walking speed, low physical activity, and weak grip strength. Frailty is diagnosed when $\ge 3$ criteria are present (1–2 indicates pre-frailty).
• Clinical Frailty Scale (CFS): Validated 9-point scale used in critical care: CFS 1–3 (fit to managing well), CFS 4 (living with very mild frailty), CFS 5 (mildly frail; requires help with instrumental ADLs), CFS 6 (moderately frail; requires help with personal ADLs), CFS 7 (severely frail; completely dependent), CFS 8 (very severely frail), and CFS 9 (terminally ill; life expectancy <6 months).
• ICU Risk Calculus: Pre-admission frailty (CFS $\ge 5$) independently predicts prolonged mechanical ventilation, failed extubation, ICU delirium, 30-day mortality, and institutional discharge. Integrating a comprehensive geriatric assessment into critical care enables objective shared decision-making regarding high-acuity interventions (CRRT, mechanical circulatory support, emergency laparotomy).