Approach to the Patient with Critical Illness¶
Chapter 311 | Harrison's 22e · Part 8 – Critical Care Medicine · Chapter 311
Key Clinical Points¶
- Critical care focuses on rapid resuscitation of patients at extremes of physiologic deterioration.
- SOFA and APACHE II are validated for population assessment, but their utility in predicting individual bedside outcomes is limited by factors like age and chronic illness.
- qSOFA is a screening tool for sepsis risk, particularly useful in resource-poor settings.
- Shock is defined by multi-system end-organ hypoperfusion.
- Distinction between 'Cold' (low cardiac output) and 'Warm' (high cardiac output) shock is critical for initial management.
- Cardiogenic shock involves a 'full' heart; hypovolemic shock involves an 'empty' heart.
- ARDS lung mechanics are defined by lower and upper inflection points on pressure-volume curves.
- High airway resistance with auto-PEEP can lead to incomplete expiration before the next breath.
- Management of septic shock requires antibiotics and aggressive fluid resuscitation.
- Refractory shock may indicate adrenal crisis, right heart syndrome, or pulmonary embolism.
ASSESSMENT OF ILLNESS SEVERITY¶
• Context: Illnesses in the ICU are categorized by degree of severity to guide management and research. • Utility of Scoring Systems: ◦ Valided for population assessment, clinical trial outcomes, and epidemiologic studies. ◦ Useful for hospital administration (resource allocation, nursing care) and quality of care assessment. ◦ Individual bedside prediction is less clear due to variables like age, chronic medical illnesses, and derangements from normal physiology. • Clinical Approach: ◦ Initial focus: Rapid resuscitation at extremes of physiologic deterioration. ◦ Secondary focus: Gathering background medical information during stabilization to supplement real-time assessment. • SOFA Scoring System (Table 311-1): ◦ Components: Six organ systems graded 0–4 based on degree of dysfunction. ◦ Clinical Use: Repeated measurements; rising scores correlate with increased mortality. ◦ Sepsis Diagnosis: An increase of ≥2 points from baseline in the setting of suspected or documented infection is diagnostic of sepsis. • qSOFA (Quick SOFA): ◦ Purpose: Screening for risk of poor outcomes from sepsis, especially in resource-poor settings. ◦ Criteria: Presence of 2 or more of the following: → Respiratory rate ≥22 breaths/min → Altered mental status → Systolic blood pressure ≤100 mmHg • APACHE II Scoring System (Table 311-2, Table 311-3): ◦ Usage: Most common system in North America. ◦ Components: Age, admission type (elective vs. non-surgical/emergency), chronic health, and 12 physiologic variables (worst values in first 24h). ◦ Outcome: Predicts hospital mortality rate.
SOFA Scoring System Details¶
Table 311-1 provides the following scoring criteria: • Respiration: ◦ ≥400 (53.3) → 0 ◦ <400 (53.3) → 1 ◦ <300 (40) → 2 ◦ <200 (26.7) with respiratory support → 3 ◦ <100 (13.3) with respiratory support → 4 • Liver: ◦ <1.2 (20) → 0 ◦ 1.2–1.9 (20–32) → 1 ◦ 2.0–5.9 (33–101) → 2 ◦ 6.0–11.9 (102–204) → 3 ◦ >12.0 (204) → 4 • Central Nervous System: ◦ Glasgow Coma Scale: 15 → 0; 13–14 → 1; 10–12 → 2; 6–9 → 3; <6 → 4 ◦ (Alternative scale): <1.2 (110) → 0; 1.2–1.9 (110–170) → 1; 2.0–3.4 (171–299) → 2; 3.5–4.9 (300–440) → 3; <500 → 4 • Cardiovascular: ◦ MAP ≥70 mmHg → 0 ◦ MAP <70 mmHg → 1 ◦ Dopamine <5 or dobutamine (any dose) → 2 ◦ Dopamine 5.1–15 or epinephrine ≤0.1 or norepinephrine ≤0.1 → 3
APACHE II Scoring Details¶
Table 311-2 and Table 311-3 provide the following scoring components: • Temperature: ≥41 (+4); 39.0–40.9 (+3); 38.5–38.9 (+2); 36.0–38.4 (+1) • Heart Rate: ≥180 (+4); 140–179 (+3); 110–139 (+2); 70–109 (+1) • Arterial pH: ≥7.70 (+4); 7.60–7.69 (+3); 7.50–7.59 (+2); 7.33–7.49 (+1) • Serum Sodium: ≥180 (+4); 160–179 (+3); 155–159 (+2); 150–154 (+1) • Serum Creatinine: ≥3.5 (+4); 2.0–3.4 (+3); 1.5–1.9 (+2); 0.6–1.4 (+1) • WBC Count: ≥40 (+4); 20–39.9 (+3); 15–19.9 (+2); 3–14.9 (+1) • Age Points (Table 311-3): ◦ <45 → 0 ◦ 45–54 → 2 ◦ 55–64 → 3 ◦ 65–74 → 5 ◦ ≥75 → 6 • Chronic Health: ◦ None → 0 ◦ If patient is admitted after elective surgery → 2 ◦ If patient is admitted after emergency surgery or for reason other than after elective surgery → 3
SHOCK¶
• Definition: Shock is defined by the presence of multi-system end-organ hypoperfusion. • Clinical Indicators: ◦ Reduced volume ◦ Tachycardia ◦ Tachypnea ◦ Cool skin and delayed capillary refill (colloquially "cold shock") ◦ Warm extremities with bounding pulses and rapid capillary refill (colloquially "warm shock") • Clinical Differentiation of Shock Types: ◦ Cold Shock (Low Cardiac Output): → Associated with hypovolemic or cardiogenic shock. → Clinical features: Cold, clammy extremities; reduced perfusion. ◦ Warm Shock (High Cardiac Output): → Associated with distributive shock (e.g., sepsis). → Clinical features: Warm, bounding extremities; low systemic vascular resistance. • Diagnostic Differentiation via JVP: ◦ Used to assess volume status in patients with low cardiac output. ◦ JVP high/crescent → Heart is "full" → Cardiogenic shock (evaluate for myocardial infarction/dysfunction; consider echocardiogram). ◦ JVP low/orthostatic → Heart is "empty" → Hypovolemic shock (initiate intravenous fluids). • Lung Mechanics in ARDS: ◦ Pressure-volume relationship (Figure 5) identifies: → Lower inflection point: Alveoli begin to open; lung compliance changes. → Upper inflection point: Alveoli become overdistended. ◦ Functional range is between these two points. • Airway Dynamics: ◦ High airway resistance → Large difference between peak and plateau pressure (Figure 6). ◦ Auto-PEEP → Flow persists into next inspiration, preventing full lung emptying.
DIAGNOSTIC APPROACH¶
- Initial Assessment: Identify presence of shock via clinical indicators (tachycardia, tachypnea, skin temperature, capillary refill).
- Categorize Shock Type: → Assess extremities: → Cold/clammy → Low cardiac output (Hypovolemic or Cardiogenic) → Warm/bounding → High cardiac output (Septic shock)
- Determine Volume Status (for Low Cardiac Output): → Measure Jugular Venous Pressure (JVP): → JVP high/crescent → Heart is "full" → Cardiogenic shock → JVP low/orthostatic → Heart is "empty" → Hypovolemic shock
- Assess Response to Intervention: → Administer intravenous fluids. → If no improvement → Proceed to differential for refractory shock.
- Refractory Shock Differentiation: → If patient remains in shock or has complex features, evaluate for: → Adrenal crisis → Right heart syndrome → Pulmonary embolism
- Advanced Imaging/Monitoring: → Consider echocardiogram and invasive monitoring for cardiogenic or refractory cases.
MANAGEMENT & TREATMENT¶
- Septic Shock Management: → Administer antibiotics. → Initiate aggressive fluid resuscitation.
- Cardiogenic Shock Management: → Evaluate for myocardial infarction or dysfunction. → Consider echocardiogram and invasive monitoring.
- Refractory/Complex Cases: → If initial trial of invasive care is not effective, transition to comfort measures. → Assess for specific causes: Adrenal crisis, right heart syndrome, or pulmonary embolism.
KEY PEARLS & HIGH-YIELD POINTS¶
• Sepsis Screening: qSOFA is a rapid bedside tool; 2/3 criteria (RR ≥22, altered mental status, SBP ≤100) indicate high risk. • Clinical Differentiation: "Cold" vs. "Warm" shock distinction is vital for determining the primary treatment path (e.g., volume vs. vasopressors). • Lung Mechanics: The range between lower and upper inflection points in ARDS represents the functional lung capacity. • Airway Resistance: A large gap between peak and plateau pressure indicates high airway resistance; auto-PEEP can lead to incomplete expiration.
Reference Tables¶
TABLE 311-1 Calculation of SOFA Score a SYSTEM Respiration¶
Harrison's 22e, p.2291
| SYSTEM | SCORE | ||||
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | |
| Respiration | |||||
| Pao/FIo, mmHg (kPa) 2 2 |
≥400 (53.3) | <400 (53.3) | <300 (40) | <200 (26.7) with respiratory support |
<100 (13.3) with respiratory support |
| ≥150 | <150 | <100 | <50 | ||
| Liver | |||||
| Bilirubin, mg/dL (μmol/L) | <1.2 (20) | 1.2–1.9 (20–32) | 2.0–5.9 (33–101) | 6.0–11.9 (102–204) | >12.0 (204) |
| MAP ≥70 mmHg | MAP <70 mmHg | Dopamine <5 or dobutamine (any dose)b |
Dopamine 5.1–15 or epinephrine ≤0.1 or norepinephrine ≤0.1b |
||
| Central nervous system | |||||
| Glasgow Coma Scalec | 15 | 13–14 | 10–12 | 6–9 | <6 |
| <1.2 (110) | 1.2–1.9 (110–170) | 2.0–3.4 (171–299) | 3.5–4.9 (300–440) or <500 |
TABLE 311-2 Calculation of Acute Physiology and Chronic Health Evaluation II (APACHE II) Score a Acute Physiology Score…¶
Harrison's 22e, p.2292
| Acute Physiology Score | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| SCORE | +4 | +3 | +2 | +1 | +0 | +1 | +2 | +3 | +4 |
| Rectal temperature (°C) | ≥41 | 39.0–40.9 | 38.5–38.9 | 36.0–38.4 | 34.0–35.9 | 32.0–33.9 | 30.0–31.9 | ≤29.9 | |
| ≥160 | 130–159 | 110–129 | 70–109 | 50–69 | |||||
| Heart rate (beats/min) | ≥180 | 140–179 | 110–139 | 70–109 | 55–69 | 40–54 | ≤39 | ||
| ≥50 | 35–49 | 25–34 | 12–24 | 10–11 | 6–9 | ||||
| Arterial pH | ≥7.70 | 7.60–7.69 | 7.50–7.59 | 7.33–7.49 | 7.25–7.32 | 7.15–7.24 | <7.15 | ||
| ≥500 | 350–499 | 200–349 | <200 >70 |
61–70 | 55–60 | ||||
| Serum sodium (meq/L) | ≥180 | 160–179 | 155–159 | 150–154 | 130–149 | 120–129 | 111–119 | ≤110 | |
| ≥7.0 | 6.0–6.9 | 5.5–5.9 | 3.5–5.4 | 3.0–3.4 | 2.5–2.9 | ||||
| Serum creatinine (mg/dL) | ≥3.5 | 2.0–3.4 | 1.5–1.9 | 0.6–1.4 | <0.6 | ||||
| ≥60 | 50–59.9 | 46–49.9 | 30–45.9 | 20–29.9 | |||||
| WBC count (103/mL) | ≥40 | 20–39.9 | 15–19.9 | 3–14.9 | 1–2.9 | <1 | |||
| Glasgow Coma Scoreb,c | |||||||||
| EYE OPENING | VERBAL (NONINTUBATED) | VERBAL (INTUBATED) | MOTOR ACTIVITY | ||||||
| 4—Spontaneous | 5—Oriented and talks | 5—Seems able to talk | 6—Verbal command | ||||||
| 4—Disoriented and talks | 3—Questionable ability to talk | ||||||||
| 2—Painful stimuli | 3—Inappropriate words | 1—Generally unresponsive | 4—Withdraws from pain | ||||||
| 2—Incomprehensible sounds 1—No response |
|||||||||
| Points Assigned to Age and Chronic Disease | |||||||||
| AGE, YEARS | SCORE | ||||||||
| <45 | 0 | ||||||||
| 2 | |||||||||
| 55–64 | 3 | ||||||||
| 5 | |||||||||
| ≥75 | 6 | ||||||||
| CHRONIC HEALTH (HISTORY OF CHRONIC CONDITIONS)d | SCORE | ||||||||
| None | 0 | ||||||||
| 2 | |||||||||
| If patient is admitted after emergency surgery or for reason other than after elective surgery | 5 |