Perioperative hypotension remains one of the most critical challenges in modern anesthesia and surgical care. Maintaining adequate mean arterial pressure (MAP) is essential to ensure sufficient tissue perfusion and prevent postoperative complications such as acute kidney injury (AKI) and myocardial injury.

A recent clinical review highlights the expanding role of vasopressors, emerging technologies, and individualized strategies in optimizing hemodynamic stability during noncardiac surgery.

Understanding arterial pressure and perfusion

Arterial pressure is determined by the interaction between:

• Cardiac output (CO)
• Systemic vascular resistance (SVR)

MAP is widely used as the primary clinical target because it reflects the driving pressure for organ perfusion.

Why hypotension matters

Even short periods of intraoperative hypotension can lead to:

• Myocardial ischemia
• Acute kidney injury
• Increased postoperative morbidity

Mechanisms of hypotension in surgical patients

1. Vasodilation (most common cause)

Vascular tone is regulated by:

• Sympathetic nervous system
• Vasopressin system
• Renin–angiotensin–aldosterone system

During surgery:

• Anesthetic agents suppress sympathetic tone
• Nitric oxide (NO) increases vasodilation
• Inflammatory mediators worsen vascular relaxation

2. Reduced cardiac output

Caused by:

• Hypovolemia
• Cardiac dysfunction
• Increased venous capacitance

What are vasopressors?

Vasopressors are pharmacologic agents that:

• Increase vascular tone
• Elevate blood pressure
• Improve organ perfusion

They are broadly classified into:

Adrenergic vasopressors

• Norepinephrine
• Phenylephrine
• Ephedrine
• Epinephrine

Non-adrenergic vasopressors

• Vasopressin
• Angiotensin II
• Methylene blue
• Hydroxocobalamin

Mechanism of action: how vasopressors work

Vasopressors influence circulation:

• α1 receptor stimulation → vasoconstriction
• β1 receptor stimulation → increased heart rate and contractility
• V1a receptor activation (vasopressin) → direct vasoconstriction

Common vasopressors used in the operating room

Norepinephrine

• Mixed α1 and β1 agonist
• First-line in many shock states
• Provides stable blood pressure control

Phenylephrine

• Pure α1 agonist
• May reduce cardiac output
• Useful in patients with arrhythmias

Ephedrine

• Indirect and direct adrenergic effects
• Preserves cardiac output
• Risk of tachyphylaxis with repeated use

Comparison of vasopressors

Hemodynamic effects:

• Phenylephrine → ↑ SVR, ↓ or neutral CO
• Norepinephrine → ↑ SVR with preserved CO
• Ephedrine → ↑ CO and heart rate
• Vasopressin → ↑ SVR without cardiac stimulation

Step-by-step approach to hypotension management

Step 1: Identify the cause

Assess:

1. Blood loss
2. Anesthetic depth
3. Cardiac function
4. Infection or inflammation

Step 2: Evaluate hemodynamic signals

• Low diastolic pressure → suggests vasodilation
• Narrow pulse pressure → suggests low stroke volume

Step 3: Decide between fluids or vasopressors

Use clinical indicators:

• Hypovolemia → fluids first
• Vasodilation → vasopressors

Step 4: Initiate therapy

• Start with a first-line vasopressor
• Titrate based on MAP response

Step 5: Reassess continuously

• Monitor perfusion
• Adjust therapy dynamically

Fluids vs vasopressors: which comes first?

Use fluids when:

• Evidence of hypovolemia
• Low stroke volume
• Positive fluid responsiveness tests

Use vasopressors when:

• Low arterial tone
• Normal or high cardiac output
• Anesthesia-induced vasodilation

Key insight: Fluids and vasopressors are complementary, not competing therapies.

Second-line therapies and adjuncts

Vasopressin

• Used when norepinephrine is insufficient
• May reduce the need for catecholamines

Angiotensin II

• Effective in refractory vasodilatory shock
• Potential renal benefits

Methylene blue

• Inhibits the nitric oxide pathway
• Limited evidence, potential risks

Hydroxocobalamin

• Scavenges nitric oxide
• Associated with kidney injury

Risks and complications of vasopressors

Potential adverse effects include:

• Excessive vasoconstriction → tissue ischemia
• Arrhythmias (β1 stimulation)
• Increased myocardial oxygen demand
• Organ hypoperfusion

Advances in vasopressor therapy

1. Peripheral norepinephrine use

• Now considered safe at low doses
• Enables rapid initiation of therapy

2. Individualized blood pressure targets

• Tailored to patient physiology
• Based on autoregulation thresholds

3. Artificial intelligence and prediction tools

• Machine learning models can predict hypotension
• Early intervention may improve outcomes

4. Closed-loop vasopressor systems

Automated systems can:

• Adjust infusion rates in real-time
• Reduce hypotensive episodes
• Improve time within the target MAP

Clinical pearls

• Avoid prolonged hypotension at all costs
• Choose vasopressors based on physiology, not habit
• Monitor both pressure and perfusion
• Reassess frequently
• Use multimodal strategies

Conclusion

Perioperative vasopressor management is rapidly evolving. While traditional pharmacologic principles remain foundational, emerging innovations, including closed-loop systems, AI-guided prediction, and individualized hemodynamic targets, are transforming clinical practice.

Ultimately, optimal outcomes depend on:

• Understanding the underlying physiology
• Tailoring therapy to the individual patient
• Integrating new technologies with clinical judgment

As ongoing trials such as VEGA-2 continue to provide evidence, the future of perioperative hemodynamic management is poised to become increasingly precise, personalized, and data-driven.

Reference: Nguyen M et al. Perioperative Vasopressor Management in Noncardiac Surgical Patients. Anesthesiology. 2026;144:670-682.

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