Management of Shock

Definition

Classification

Hemorrhagic Shock - ATLS Classification

General Principles of Management

Step-by-Step Initial Management

1. Airway and Oxygenation

• Apply supplemental oxygen, titrate to maintain SpO2 92-95%
• If the patient cannot maintain adequate respiratory compensation for metabolic acidosis, or if hypoxemia is severe, proceed with intubation and mechanical ventilation
• Use lung-protective strategies: low tidal volume (6 mL/kg IBW), optimize PEEP, daily sedation holidays - Harrison's 22E

2. Vascular Access and Monitoring

• Place two large-bore peripheral IV catheters (16 or 18 gauge) for initial resuscitation
• If vasopressors are needed or volume resuscitation is inadequate, place a central venous catheter (CVC) - provides CVP monitoring and central venous O2 saturation (ScvO2), a surrogate for mixed venous saturation
• Arterial line for continuous MAP measurement, pulse/systolic pressure variation (volume responsiveness), and repeated ABG/lactate sampling (peripheral oximetry is unreliable in hypoperfusion states)
• Urinary catheter for hourly urine output monitoring as a marker of renal perfusion
• In cardiac arrest or critical illness, intraosseous access is the fastest route when IV access fails
• If cardiogenic shock is suspected and more detailed hemodynamics are needed, a Swan-Ganz catheter (measuring PCWP, CO, SVR) may be placed - Harrison's 22E

3. Point-of-Care Ultrasound (POCUS)

• Cardiac windows: LV function (cardiogenic vs distributive), pericardial effusion/tamponade
• IVC collapsibility: Collapsible IVC in a spontaneously breathing patient at end-expiration suggests reduced intravascular volume
• Pleural space: Pneumothorax (more sensitive than CXR), pleural effusion
• Abdomen: Free fluid suggesting hemorrhage or infection
• Lower extremity veins: DVT, raising suspicion for PE Limitation: performance and interpretation are operator-dependent. A 2018 RCT of 253 ED patients did not show a 30-day survival benefit from POCUS-guided management of undifferentiated shock. - Harrison's 22E

4. Fluid Resuscitation

Crystalloids vs Colloids

• Crystalloids are first-line (normal saline or balanced solutions such as Lactated Ringer's / Plasmalyte)
• Colloids (albumin, starches) have not been shown superior to crystalloids for survival in critical illness; modern evidence favors balanced crystalloid solutions over 0.9% saline (associated with less hyperchloremic acidosis and renal injury)
• In hemorrhagic shock: whole blood is optimal; plasma is an acceptable substitute when whole blood is unavailable; dextran solutions provide colloidal oncotic support - Guyton & Hall

By Shock Type:

• Hypovolemic/distributive: Aggressive volume resuscitation is first-line; 30 mL/kg IV crystalloid bolus is recommended in septic shock per Surviving Sepsis Campaign
• Cardiogenic shock: Volume must be used cautiously - aggressive fluid administration risks worsening pulmonary edema. Transfusion threshold is 8 g/dL (same safety as 10 g/dL in AMI patients) but the patient must be monitored carefully for worsening failure - Goldman-Cecil Medicine
• Septic shock: Transfuse packed red blood cells at Hb <7 g/dL (as effective as 9 g/dL threshold); no routine role for platelets or other blood products in resuscitation
• Volume reassessment: As the patient evolves (e.g., develops ARDS or renal failure), the fluid strategy must be adjusted - volume removal may then be appropriate - Harrison's 22E

In vasodilatory shock: Permissive hypotension targeting MAP ≥60 mmHg is acceptable rather than targeting higher pressures with more aggressive fluid loading, which yields similar outcomes. - Goldman-Cecil

5. Vasopressors and Inotropes

6. Antibiotic Therapy (Septic Shock)

• Sepsis is the most common cause of shock
• Every hour of delay in appropriate antibiotics is associated with increased mortality
• Obtain appropriate cultures (blood cultures x2 sets, urine, respiratory) before starting antibiotics - but inability to obtain cultures must not delay treatment
• Start broad-spectrum antibiotics as soon as septic shock is suspected
• When sepsis is excluded, practice antibiotic stewardship and discontinue antibiotics promptly - Harrison's 22E

7. Cause-Specific (Tailored) Interventions

• Harrison's 22E; Rosen's Emergency Medicine

8. Endpoints of Resuscitation

• MAP ≥65 mmHg (≥60 mmHg may be acceptable in distributive shock)
• Urine output >0.5 mL/kg/hr
• Serum lactate normalization / clearance ≥10-20% (marker of tissue hypoperfusion resolving)
• ScvO2 ≥70% (surrogate for adequacy of oxygen delivery relative to demand)
• Improving mental status and skin perfusion (capillary refill, temperature)
• Decreasing base deficit (approaching 0)
• Resolution of tachycardia and return of normal pulse pressure

9. Irreversible Shock

Monitoring

• Continuous ECG, pulse oximetry
• Arterial line for continuous MAP and repeated ABG
• CVP (central venous pressure)
• ScvO2 (central venous oxygen saturation)
• Hourly urine output
• Serial lactate measurements
• POCUS for dynamic assessment

Prognosis

• Response of blood pressure and cardiac output to resuscitation
• Trend in serum lactate
• Early development of multi-organ dysfunction (predictive of prolonged ICU course and higher mortality)
• Age, comorbidities, and the inciting event determine long-term outcomes
• Interestingly, acute features of shock (degree of hypotension) predict short-term mortality but are less predictive of long-term survival - Goldman-Cecil Medicine

Summary Algorithm

SHOCK RECOGNIZED (hypotension + tissue hypoperfusion)
        |
        ▼
Simultaneous: Airway/O2 | IV Access | Monitor | Labs | ECG | CXR | POCUS
        |
        ▼
Undifferentiated? → Start IV fluids + cultures + empiric antibiotics
        |
        ├── HYPOVOLEMIC → Crystalloids ± blood products → Control bleeding
        |
        ├── DISTRIBUTIVE → Fluids → Norepinephrine → Antibiotics (sepsis)
        |                   Epinephrine (anaphylaxis) | Steroids (adrenal)
        |
        ├── CARDIOGENIC → Judicious fluids → Dobutamine ± Norepinephrine
        |                  Revascularize (AMI) | Mechanical support
        |
        └── OBSTRUCTIVE → Immediate decompression
                           Pericardiocentesis | Needle thoracostomy | Thrombolysis