Vasopressor Management in Severe Hypotension
Norepinephrine is the first-line vasopressor for severe hypotension, with an initial dose of 0.02-0.05 μg/kg/min titrated to maintain a target mean arterial pressure (MAP) ≥65 mmHg. 1, 2, 3
Initial Approach to Severe Hypotension
- Begin with rapid fluid resuscitation using crystalloids at 30 mL/kg within the first 3 hours for patients with hypoperfusion, while simultaneously considering early vasopressor initiation in profound hypotension 1, 4
- Place an arterial catheter as soon as practical for continuous blood pressure monitoring in all patients requiring vasopressors 1, 5
- Target a MAP of 65 mmHg as the initial goal for vasopressor therapy, though this should be higher (approximately 40 mmHg below baseline) in previously hypertensive patients 1, 2, 3
- Monitor for signs of adequate perfusion, including mental status, capillary refill, lactate clearance, and urine output 1
Norepinephrine Administration
- Dilute norepinephrine in dextrose-containing solutions (4 mg in 1000 mL of 5% dextrose) to yield a concentration of 4 μg/mL 3
- Administer through a central venous catheter whenever possible to avoid extravasation 3
- Initial dosing should be 0.02-0.05 μg/kg/min (approximately 2-3 mL/min of standard dilution), titrated to maintain target MAP 1, 3
- Average maintenance dose ranges from 0.5-1 mL/min (2-4 μg/min of base), but higher doses may be necessary in refractory cases 3
Management of Refractory Hypotension
- For persistent hypotension despite norepinephrine at 0.1-0.2 μg/kg/min, consider adding vasopressin (up to 0.03 U/min) to either raise MAP or decrease norepinephrine requirements 1, 2, 5
- Epinephrine (0.1-0.5 μg/kg/min) is an alternative second agent, particularly in patients with myocardial dysfunction 6, 2
- Consider hydrocortisone 200 mg/day (as 50 mg IV every 6 hours) if no response to vasopressors after 4 hours 1
- In cardiogenic shock or when signs of hypoperfusion persist despite adequate fluid resuscitation and vasopressor therapy, add dobutamine (5-10 μg/kg/min) 6, 5
Shock-Specific Considerations
- In septic shock with low systemic vascular resistance (SVR), norepinephrine is the first choice vasopressor 6, 7
- In shock with low cardiac index, normal blood pressure, and high SVR, consider vasodilators like nitroprusside or nitroglycerin 6
- In shock with low cardiac index, low blood pressure, and low SVR, add norepinephrine to epinephrine to increase diastolic blood pressure and SVR 6
- In shock with high cardiac index and low SVR, consider adding low-dose vasopressin or angiotensin when titration of norepinephrine and fluid does not resolve hypotension 6
Common Pitfalls and Caveats
- Avoid relying solely on fluid resuscitation in profound shock as this may prolong hypotension and worsen outcomes 1, 4
- Avoid phenylephrine except in specific circumstances (norepinephrine-associated arrhythmias, high cardiac output with persistent low BP, or as salvage therapy) 1, 2
- Do not use low-dose dopamine for renal protection as it has not shown benefit and carries higher risk of arrhythmias 1, 2
- Avoid targeting supranormal cardiac index levels as this may be harmful 5
- When discontinuing vasopressors, reduce gradually to avoid abrupt withdrawal and hypotension 3
- In patients with baseline left ventricular ejection fraction ≤45%, achieving MAP values ≥75 mmHg with norepinephrine may not improve cardiac output 8
Special Considerations
- Early administration of norepinephrine may be particularly beneficial in patients with profound hypotension (diastolic BP ≤40 mmHg) or high diastolic shock index (heart rate/diastolic BP ≥3) 4
- Consider early norepinephrine in patients at risk for fluid accumulation or in whom fluid accumulation would be particularly harmful (ARDS, intra-abdominal hypertension) 4
- For refractory shock, rule out and address potential underlying causes: pericardial effusion, pneumothorax, adrenal insufficiency, hypothyroidism, ongoing blood loss, increased intra-abdominal pressure, or inadequate source control of infection 6