What is the management approach for shock in the context of Systemic Inflammatory Response Syndrome (SIRS)?

Management of Shock in the Context of SIRS

Begin immediate resuscitation with 30 mL/kg crystalloid bolus within the first 3 hours, initiate norepinephrine as first-line vasopressor to target MAP ≥65 mmHg, and administer empiric antibiotics within 1 hour of recognition. 1, 2

Initial Resuscitation (First 3 Hours)

Fluid Resuscitation:

• Administer 30 mL/kg of crystalloid (isotonic saline or balanced crystalloid) as a fixed initial bolus within 3 hours of recognition 1
• This volume enables clinicians to initiate resuscitation while obtaining more specific hemodynamic information 1
• After initial bolus, use dynamic variables (pulse pressure variation, passive leg raise) rather than static measures (CVP) to guide further fluid administration 1
• Critical pitfall: Many patients require more than 30 mL/kg, but avoid fluid overload once tissue hypoperfusion resolves, as this decreases ventilator-free days and worsens outcomes 1, 3

Hemodynamic Targets:

• Target MAP ≥65 mmHg as the initial goal 1
• Consider lactate normalization as a marker of adequate tissue perfusion 1
• In pediatric patients, push 20 mL/kg boluses up to and over 60 mL/kg until perfusion improves 1

Vasopressor Therapy

First-Line Agent:

• Norepinephrine is the first-choice vasopressor (strong recommendation) 1
• Place arterial catheter as soon as practical for continuous blood pressure monitoring 1

Second-Line Options:

• Add vasopressin (up to 0.03 U/min) to norepinephrine to raise MAP to target or to decrease norepinephrine dosage 1
• Alternatively, add epinephrine to norepinephrine if MAP targets not met 1
• Dopamine should only be used in highly selected patients (low risk of tachyarrhythmias, absolute or relative bradycardia) 1
• Do not use low-dose dopamine for renal protection (strong recommendation against) 1

Inotropic Support:

• Add dobutamine in patients with persistent hypoperfusion despite adequate fluid loading and vasopressor use 1
• Titrate to endpoints reflecting perfusion; reduce or discontinue if worsening hypotension or arrhythmias develop 1

Antimicrobial Therapy

Timing and Selection:

• Administer empiric antibiotics within 1 hour of identifying severe sepsis/septic shock 1, 2
• Obtain blood cultures before antibiotics when possible, but never delay antibiotic administration for cultures 1
• Adjust empiric choices based on local resistance patterns (MRSA, resistant gram-negatives, etc.) 1

Corticosteroid Therapy

Indications:

• Consider IV hydrocortisone 200 mg/day only if adequate fluid resuscitation and vasopressor therapy fail to restore hemodynamic stability 1
• Do not use ACTH stimulation test to identify patients who should receive hydrocortisone 1
• Taper hydrocortisone when vasopressors are no longer required 1
• Do not administer corticosteroids for sepsis in the absence of shock 1
• In pediatric patients, use hydrocortisone if at risk for absolute adrenal insufficiency 1

Mechanical Ventilation (If ARDS Develops)

Lung-Protective Strategy:

• Target tidal volume of 6 mL/kg predicted body weight (strong recommendation) 1, 3
• Maintain plateau pressures ≤30 cmH₂O 1, 3
• Use higher PEEP (≥12 cmH₂O) in moderate to severe ARDS 1, 3
• Limit driving pressure to <18 cmH₂O to reduce right ventricular strain 3

Advanced Interventions:

• Implement prone positioning for >12 hours daily if PaO₂/FiO₂ <150 mmHg (strong recommendation) 1, 3
• Consider neuromuscular blockade for ≤48 hours if PaO₂/FiO₂ <150 mmHg 1, 3
• Maintain head of bed elevation 30-45 degrees to prevent ventilator-associated pneumonia 1, 3

Fluid Management After Initial Resuscitation

Conservative Strategy:

• Once tissue hypoperfusion resolves, apply conservative fluid strategy targeting negative fluid balance 1, 3
• This is particularly important in established ARDS without evidence of ongoing tissue hypoperfusion (strong recommendation) 1
• Critical pitfall: In patients with generalized peritonitis, excessive fluid increases intra-abdominal pressure and worsens outcomes 2

Blood Product Administration

Transfusion Thresholds:

• Transfuse RBCs only when hemoglobin <7.0 g/dL, targeting 7.0-9.0 g/dL once tissue hypoperfusion resolved 1
• Exception: Target hemoglobin ≥10 g/dL during active resuscitation with ScvO₂ <70% 1
• In alveolar hemorrhage, maintain hemoglobin >8 g/dL to preserve oxygen-carrying capacity 3

Platelets and Plasma:

• Administer platelets prophylactically when <10,000/mm³ without bleeding 1
• Consider platelets when <20,000/mm³ with significant bleeding risk 1
• Target ≥50,000/mm³ for active bleeding, surgery, or invasive procedures 1
• Do not use fresh frozen plasma to correct laboratory clotting abnormalities without bleeding or planned procedures 1

Monitoring and Reassessment

Hemodynamic Monitoring:

• Use dynamic variables over static measures to predict fluid responsiveness 1
• Consider transpulmonary thermodilution or echocardiography to guide therapy in refractory shock 1
• Monitor for acute cor pulmonale (occurs in 20-25% of ARDS cases) using echocardiography 1, 3
• Do not routinely use pulmonary artery catheters in sepsis-induced ARDS 1, 3

Metabolic Targets:

• Normalize lactate as marker of adequate resuscitation 1
• Control hyperglycemia targeting <180 mg/dL 1
• Correct hypoglycemia and hypocalcemia, particularly in pediatric patients 1

Special Populations

Pediatric Considerations:

• Use atropine/ketamine for intubation if needed 1
• Reverse cold shock by titrating central dopamine or epinephrine 1
• Reverse warm shock by titrating central norepinephrine 1
• Target cardiac index 3.3-6.0 L/min/m² 1
• Consider ECMO for refractory shock 1

Immunocompromised Patients:

• Have increased susceptibility to septic shock due to pre-existing immune dysfunction 2
• Maintain high index of suspicion and lower threshold for intervention 2

Critical Pitfalls to Avoid

• Never delay antibiotics beyond 1 hour to obtain cultures or additional testing 1, 2
• Avoid excessive fluid administration after initial resuscitation, particularly in ARDS or peritonitis 1, 2, 3
• Do not use dopamine for renal protection - this is ineffective and potentially harmful 1
• Recognize progression early: SIRS progresses to sepsis, severe sepsis, and septic shock with stepwise increases in mortality (7%, 16%, 20%, 46% respectively) 4
• Monitor for right ventricular failure in mechanically ventilated patients, as positive pressure ventilation increases RV afterload 1