How to manage a patient with hypotension?

Management of Hypotension

The most critical first step in managing hypotension is determining the underlying physiological cause—hypovolemia, vasodilation, bradycardia, or low cardiac output—rather than reflexively administering fluids, as only approximately 50% of hypotensive patients are fluid-responsive. 1

Initial Assessment and Stabilization

Determine Hemodynamic Stability

• Immediately assess whether the patient is stable or unstable by evaluating for signs of end-organ dysfunction (altered mental status, oliguria, cool extremities, elevated lactate) 2
• Unstable patients displaying end-organ dysfunction require immediate treatment in a high-acuity care setting 2
• Symptomatic hypotension should be treated immediately 2

Identify the Underlying Cause

Treatment must be directed at the specific physiological derangement causing hypotension, as each requires fundamentally different management 1:

For Hypovolemia:

• Administer intravascular fluids (crystalloid, colloid, or blood products) 1
• In pediatric patients, give an initial normal saline bolus of 10-20 mL/kg (maximum 1,000 mL) 2, 1

For Vasodilation:

• Use vasopressors (phenylephrine, norepinephrine, or epinephrine) 1
• Phenylephrine is best for hypotension accompanied by tachycardia, as it causes reflex bradycardia 2, 1

For Bradycardia:

• Administer anticholinergics (atropine or glycopyrronium) as first-line 1
• Use epinephrine or isoprenaline if refractory 1
• Consider pacing for profound bradycardia 1

For Low Cardiac Output:

• Administer positive inotropes (dobutamine or epinephrine) 1, 3

Diagnostic Approach: The Passive Leg Raise Test

Why Perform PLR Before Giving Fluids

• A passive leg raise (PLR) test should be performed before administering fluids to determine if hypovolemia is contributing to hypotension 2, 1
• This is critical because only 54% of postoperative patients with suspected hypovolemia actually respond to fluid boluses 2, 1
• The remaining ~50% require correction of vascular tone or inotropy instead 2, 1

Interpreting PLR Results

• Positive PLR: An increase in cardiac output after PLR strongly predicts fluid responsiveness (positive likelihood ratio = 11; 95% CI, 7.6-17; pooled specificity 92%) 2, 1
• Negative PLR: No increase in cardiac output after PLR indicates the patient will likely not respond to fluid (negative likelihood ratio = 0.13; 95% CI, 0.07-0.22; pooled sensitivity 88%) 2, 1
• If PLR does not correct hypotension, focus management on vascular tone and chronotropy/inotropy 2

Practical Application

• Although existing literature specifically examined PLR's effect on monitored cardiac output, it is likely useful in detecting whether inadequate preload is contributing to hypotension even without advanced monitoring 2
• Non-invasive cardiac output monitors and portable ultrasound devices may help identify the root cause of hypotension and guide treatment selection 2

Pharmacological Management

Vasopressors and Inotropes

Phenylephrine:

• Best used when hypotension is accompanied by tachycardia 2, 1
• Critical caveat: Can cause reflex bradycardia, especially in the preload-independent state 2, 1

Epinephrine (for septic shock):

• Dilute 1 mg in 1,000 mL of 5% dextrose to produce 1 mcg/mL solution 3
• Infusion rate: 0.05-2 mcg/kg/min, titrated to achieve desired mean arterial pressure 3
• Adjust every 10-15 minutes in increments of 0.05-0.2 mcg/kg/min 3
• After hemodynamic stabilization, wean incrementally over 12-24 hours 3

Dopamine:

• At lower infusion rates, if hypotension persists despite increasing the rate, discontinue dopamine and switch to a more potent vasoconstrictor like norepinephrine 4
• Important interaction: Patients on MAO inhibitors within 2-3 weeks should receive initial doses no greater than one-tenth of the usual dose 4
• Monitor closely for ventricular arrhythmias; reduce dose if ectopic beats increase 4

Dobutamine:

• Recommended for low cardiac output from myocardial dysfunction 1

Special Considerations for Pediatric Patients

• Avoid additional fluid boluses in children with underlying cardiac dysfunction or signs of volume overload (pulmonary edema) 2, 1
• Consider early colloid solutions due to potential rapid capillary leak development in certain conditions 2, 1
• Transfer to intensive care should be considered early in the management process 2

Context-Specific Approaches

Trauma Patients

• Without brain injury: Use restricted volume replacement with target systolic BP 80-90 mmHg (MAP 50-60 mmHg) until major bleeding is controlled 1
• With severe traumatic brain injury: Maintain MAP ≥80 mmHg to ensure adequate cerebral perfusion 1

Postoperative Patients

• Only 54% of postoperative patients with suspected hypovolemia respond to fluid boluses 2, 1
• Typical signs and symptoms of suspected hypovolemia (systolic pressure <90 mmHg, MAP <70 mmHg, oliguria, heart rate >100 bpm) are not predictive of fluid responsiveness 2
• Patient transfer to higher level of care may be required to deliver appropriate therapies 2

Critical Pitfalls to Avoid

Do Not Reflexively Give Fluids

• The most common error: Approximately 50% of hypotensive patients are not hypovolemic 2, 1
• Administering fluids to non-fluid-responsive patients delays appropriate treatment and may cause harm 2, 1

Avoid Aggressive Fluid Resuscitation in Specific Contexts

• In trauma without brain injury, aggressive fluid resuscitation increases mortality 1
• In patients with cardiac dysfunction or volume overload, additional fluids can cause pulmonary edema 2, 1

Do Not Use Permissive Hypotension in Traumatic Brain Injury

• Maintain MAP ≥80 mmHg in TBI patients, as permissive hypotension compromises cerebral perfusion 1

Monitor for Supine Hypertension

• When using vasopressors, avoid the last dose after 6 PM to prevent supine hypertension during sleep 5
• Target blood pressure should account for increased venous outflow pressure and extravascular compartment pressures 2

Monitoring and Reassessment

• Continuous intraoperative arterial pressure monitoring reduces severity and duration of hypotension compared to intermittent monitoring 1
• Close monitoring of urine flow, cardiac output, and blood pressure is necessary during vasopressor infusion 4
• Serial reassessment of the patient's condition is paramount after initiating treatment 6
• The therapeutic goal should be minimizing symptoms and improving functional status, not necessarily restoring normotension 5, 7, 8