When should pressors be started in a patient with hypotension?

When to Start Vasopressors in Hypotensive Patients

Vasopressors should be initiated when hypotension persists after initial fluid resuscitation, specifically when mean arterial pressure (MAP) remains below 65 mmHg despite adequate fluid loading, or when life-threatening hypotension (systolic blood pressure <80-90 mmHg) occurs requiring immediate blood pressure support to prevent organ ischemia. 1

Initial Fluid Resuscitation Before Vasopressors

• Fluid resuscitation must be attempted first before initiating vasopressors, as blood volume depletion should always be corrected as fully as possible 2
• Administer 30 mL/kg of crystalloid fluid within the first 3 hours for patients with septic shock or hypotension 1
• Use balanced crystalloid solutions (lactated Ringer's, Plasma-Lyte) rather than normal saline for resuscitation 1
• In resource-limited settings or when pulmonary edema risk is high, consider a more restrictive initial bolus of 1-2 L, escalating to 30 mL/kg if inadequate response 1

Specific Triggers for Vasopressor Initiation

After fluid challenge, start vasopressors when:

• MAP remains <65 mmHg despite adequate fluid resuscitation 1
• **Systolic blood pressure <90 mmHg** (or drop >40 mmHg from baseline) after crystalloid challenge of 30 mL/kg 3
• Life-threatening hypotension requiring immediate pressure support to prevent cerebral or coronary ischemia, even before completing full fluid resuscitation 2
• Patient shows signs of persistent tissue hypoperfusion (altered mental status, oliguria, elevated lactate) despite fluid administration 1
• Patient is not a candidate for further fluid resuscitation due to pulmonary edema or fluid overload 1

Timing Considerations

• A large retrospective analysis found mortality was lowest when vasopressors were delayed by 1 hour and infused from hours 1-6 following onset of shock, suggesting some fluid resuscitation should precede vasopressor initiation when possible 1
• However, do not delay vasopressors when life-threatening hypotension threatens vital organ perfusion 2
• Vasopressors can be administered before and concurrently with blood volume replacement as an emergency measure to maintain intraaortic pressures 2

First-Line Vasopressor Choice

• Norepinephrine is the first-choice vasopressor for hypotensive shock 1, 4
• Start norepinephrine at 0.02 mcg/kg/min (or 2-3 mL/min of standard dilution = 8-12 mcg/min), titrating to MAP goal 1, 2
• Target MAP of 65 mmHg in most patients (may target 40 mmHg below baseline in chronic hypertensives) 1, 2
• Norepinephrine can be initiated peripherally until central access is obtained 1

Second-Line Agents

• Add vasopressin (0.03-0.04 units/min) if MAP inadequate on low-to-moderate norepinephrine doses (0.1-0.2 mcg/kg/min) 1, 5
• Add epinephrine as alternative second-line agent if vasopressin unavailable 1
• Consider dobutamine (up to 20 mcg/kg/min) if persistent hypoperfusion despite adequate fluid and vasopressors, suggesting cardiac dysfunction 1

Critical Monitoring

• Place arterial catheter as soon as practical for continuous blood pressure monitoring in all patients requiring vasopressors 1
• Monitor for signs of adequate perfusion: capillary refill, skin temperature, mental status, urine output (>0.5 mL/kg/h) 1
• Assess lactate clearance and tissue perfusion markers within 6 hours 1

Important Caveats

• Avoid dopamine as first-line agent due to increased arrhythmia risk; reserve only for highly selected patients with bradycardia and low arrhythmia risk 1
• In trauma/hemorrhagic shock, prioritize blood product resuscitation over excessive crystalloid, and use vasopressors cautiously only after addressing hypovolemia 6, 7
• Do not use low-dose dopamine for renal protection—this is ineffective 1
• In pregnant patients, standard MAP targets apply but monitor fetal status when using vasopressin due to theoretical oxytocin receptor interaction 1