Management of Shock: Evidence-Based Approach
Pathophysiology Overview
Shock represents acute widespread reduction in effective tissue perfusion causing oxygen supply-demand imbalance, anaerobic metabolism, lactic acidosis, and cellular dysfunction that, if prolonged, leads to irreversible organ damage and death 1. The four primary shock categories—distributive (including septic), hypovolemic, cardiogenic, and obstructive—each require distinct management strategies, though distributive shock is by far the most common in critical care settings 2.
Initial Fluid Resuscitation
Crystalloid Administration
Administer at least 30 mL/kg of crystalloid solution within the first 3 hours of resuscitation in patients with sepsis-induced hypoperfusion or septic shock 3, 4. This represents a strong recommendation with moderate quality evidence from the Surviving Sepsis Campaign 5.
- Crystalloids are the fluid of choice for initial resuscitation and subsequent intravascular volume replacement (strong recommendation, moderate quality evidence) 5, 3
- More rapid administration and greater amounts beyond the initial 30 mL/kg may be needed in some patients 5, 3
- Continue fluid administration using a fluid challenge technique as long as hemodynamic factors continue to improve 5, 3
Crystalloid Type Selection
Balanced crystalloids (lactated Ringer's or Plasma-Lyte) should be preferred over normal saline when available 4. The evidence supporting this includes:
- Balanced crystalloids reduce the risk of hyperchloremic metabolic acidosis compared to normal saline 4
- In septic patients, balanced crystalloids are associated with lower in-hospital mortality (17.7% vs 20.2% with saline alone, P < 0.001) 6
- Either balanced crystalloids or saline can be used, though balanced solutions are preferred (weak recommendation, low quality evidence) 5
Albumin Considerations
Albumin may be added to crystalloids when patients require substantial amounts of crystalloids to maintain adequate mean arterial pressure (weak recommendation, low quality evidence) 5. This is a second-line consideration after initial crystalloid resuscitation 3.
Fluids to Avoid
Hydroxyethyl starches must NOT be used for intravascular volume replacement (strong recommendation, high quality of evidence) 5, 3. These agents increase the risk of acute kidney injury and mortality 3, 4.
- Gelatins should also be avoided in favor of crystalloids (weak recommendation, low quality evidence) 5
Hemodynamic Monitoring and Reassessment
Dynamic Assessment Approach
Use a fluid challenge technique where administration continues only as long as hemodynamic improvement occurs 5, 3. This requires:
- Frequent reassessment of hemodynamic status including heart rate, blood pressure, arterial oxygen saturation, respiratory rate, temperature, urine output, mental status, and peripheral perfusion 3
- Dynamic measures of fluid responsiveness (pulse pressure variation, stroke volume variation) are preferred over static measures like central venous pressure 3, 4
- Stop fluid administration when no improvement in tissue perfusion occurs, signs of fluid overload develop, or hemodynamic parameters stabilize 4
Critical Pitfall to Avoid
Do not delay resuscitation due to concerns about fluid overload—delayed resuscitation increases mortality 4. However, monitor continuously for signs of fluid overload including pulmonary crackles, increased jugular venous pressure, and worsening respiratory function 7.
Vasopressor Therapy
First-Line Vasopressor
If the patient remains hypotensive despite adequate fluid resuscitation, initiate norepinephrine as the first-choice vasopressor targeting a mean arterial pressure (MAP) of 65 mmHg (strong recommendation, moderate quality evidence) 5, 3, 4, 7.
- All patients requiring vasopressors should have an arterial catheter placed as soon as practical if resources are available 5
- Norepinephrine is superior to dopamine and other agents for first-line therapy 5
Second-Line Vasopressor Options
When additional agents are needed to maintain adequate blood pressure:
- Add epinephrine to norepinephrine (grade 2B, weak recommendation, low quality evidence) 5, 7
- Add vasopressin 0.03 units/minute to norepinephrine with intent of either raising MAP to target or decreasing norepinephrine dosage (weak recommendation, moderate quality evidence) 5, 8
Vasopressin Dosing Specifics
For septic shock, the FDA-approved dosing is 8:
- Starting dose: 0.01 units/minute
- Titrate up by 0.005 units/minute at 10-15 minute intervals
- Maximum recommended: 0.07 units/minute for septic shock
- Vasopressin should NOT be used as the single initial vasopressor 5
- Doses higher than 0.03-0.04 units/minute should be reserved for salvage therapy 5
Agents to Avoid or Use Sparingly
Dopamine should only be used as an alternative vasopressor in highly selected patients (e.g., those with low risk of tachyarrhythmias and absolute or relative bradycardia) (grade 2C, weak recommendation) 5.
- Low-dose dopamine must NOT be used for renal protection (grade 1A, strong recommendation, high quality evidence) 5, 4
- Phenylephrine is not recommended except in specific circumstances: norepinephrine-associated serious arrhythmias, high cardiac output with persistently low blood pressure, or as salvage therapy 5
Inotropic Support
Administer dobutamine infusion up to 20 μg/kg/min in patients who show evidence of persistent hypoperfusion despite adequate fluid loading and vasopressor use (weak recommendation, low quality evidence) 5. Specific indications include:
- Myocardial dysfunction with elevated cardiac filling pressures and low cardiac output 5
- Ongoing signs of hypoperfusion despite achieving adequate intravascular volume and MAP 5
- Dosing should be titrated to perfusion endpoints and reduced or discontinued if worsening hypotension or arrhythmias occur 5
Source Control
Identify or exclude anatomic diagnosis of infection requiring emergent source control as rapidly as possible 5. Key actions include:
- Implement required source control intervention as soon as medically and logistically practical after diagnosis 5
- Promptly remove intravascular access devices that are possible sources of sepsis after establishing alternative vascular access 5, 7
Type-Specific Shock Considerations
Cardiogenic Shock
For cardiogenic shock, the management differs significantly 9:
- Fluid resuscitation must be cautious to avoid worsening pulmonary edema
- Inotropic support with dobutamine or milrinone is often required earlier
- Vasopressors may worsen cardiac function and should be used judiciously 8
Hypovolemic Shock
- Aggressive fluid resuscitation remains the cornerstone
- Identify and correct the primary cause (hemorrhage, dehydration)
- Vasopressors are generally not needed once volume is restored
Obstructive Shock
For obstructive shock (e.g., pulmonary embolism, cardiac tamponade) 2, 1:
- Definitive treatment requires relieving the obstruction
- Fluid resuscitation and vasopressors are temporizing measures only
Common Pitfalls in Shock Management
The most common errors leading to poor outcomes are 10:
- Late diagnosis and delayed recognition of early shock signs
- Inadequate control of the primary problem causing shock
- Inadequate fluid loading during initial resuscitation
- Delayed ventilator assistance when needed
- Excessive reliance on vasopressors and diuretics before adequate fluid resuscitation 10
Do not rely solely on static measures like central venous pressure to guide fluid therapy, as they have poor predictive ability for fluid responsiveness 4.