What is the role of pressors (pressor medications), such as norepinephrine, in resuscitation (resus) for treating hypotension?

Role of Pressors in Resuscitation for Treating Hypotension

Norepinephrine is the first-choice vasopressor for treating severe hypotension (systolic blood pressure <70 mmHg) during resuscitation, particularly when associated with low peripheral vascular resistance. 1

Indications for Vasopressor Use in Resuscitation

• Vasopressors are indicated for severe hypotension (systolic blood pressure <70 mmHg) that persists despite adequate fluid resuscitation 1
• Vasopressors should be initiated when fluid resuscitation alone fails to restore adequate tissue perfusion, and may be started during fluid resuscitation in severe cases 1
• Hemodynamic instability is common after cardiac arrest, with vasodilation occurring from loss of sympathetic tone and metabolic acidosis 1

First-Line Vasopressor Choice

• Norepinephrine (0.1-0.5 mcg/kg/min) is strongly recommended as the first-choice vasopressor for most types of shock 1
• Norepinephrine increases systemic vascular resistance and mean arterial blood pressure while reducing the need for excessive fluid administration 2
• In septic shock specifically, early administration of norepinephrine increases cardiac output, improves microcirculation, and avoids fluid overload 2

Target Blood Pressure

• Vasopressor therapy should initially target a mean arterial pressure (MAP) of 65 mmHg 1
• Higher MAP targets may be appropriate for patients with chronic hypertension 2
• Titration should be guided by both arterial pressure and markers of tissue perfusion (lactate clearance, urine output, mental status) 1

Alternative Vasopressors

• Epinephrine (0.1-0.5 mcg/kg/min) can be added to or substituted for norepinephrine when additional support is needed 1
• Epinephrine is particularly useful for anaphylaxis with hemodynamic instability or respiratory distress 1
• Vasopressin (up to 0.03 U/min) can be added to norepinephrine to either raise MAP or decrease norepinephrine dosage 1
• Dopamine (5-10 mcg/kg/min) should be reserved for highly selected patients with hypotension associated with symptomatic bradycardia or low risk of tachyarrhythmias 1
• Phenylephrine (0.5-2.0 mcg/kg/min) should be reserved for specific situations where norepinephrine causes serious arrhythmias or as salvage therapy 1

Specific Clinical Scenarios

Post-Cardiac Arrest

• Hemodynamic instability after cardiac arrest is common and associated with poor outcomes 1
• Myocardial stunning and dysfunction can last many hours after cardiac arrest 1
• Norepinephrine is appropriate for initial management of post-arrest hypotension 1

Trauma Resuscitation

• In trauma, vasopressors should only be used if a restricted volume replacement strategy fails to achieve target blood pressure 1
• Norepinephrine is recommended if severe hemorrhage-induced hypotension (systolic BP <80 mmHg) persists despite fluid resuscitation 1

Cardiogenic Shock

• In cardiogenic shock, inotropes (dobutamine, dopamine, phosphodiesterase III inhibitors) are first-line agents 1
• If hypotension persists with tachycardia, norepinephrine is advised 1
• In bradycardic cardiogenic shock, dopamine may be considered 1

Administration Considerations

• Vasopressors should ideally be administered through a central venous line to prevent tissue necrosis from extravasation 1
• If extravasation occurs, infiltrate 5-10 mg of phentolamine diluted in 10-15 mL of saline into the site as soon as possible 1
• Adrenergic drugs should not be mixed with sodium bicarbonate or other alkaline solutions as they may be inactivated 1
• Vasopressors must be titrated at the bedside to achieve the intended effect while limiting side effects 1

Potential Adverse Effects

• Norepinephrine may increase myocardial oxygen requirements, requiring cautious use in patients with ischemic heart disease 1
• Norepinephrine can cause renal and mesenteric vasoconstriction, though in sepsis it may actually improve renal blood flow 1
• High-dose epinephrine is harmful and not recommended in cardiac arrest as it does not improve survival to discharge or neurologic outcomes 3
• Vasopressors are relatively contraindicated in hypovolemia until adequate fluid resuscitation has been provided 1

Pharmacologic Considerations

• Norepinephrine acts primarily on alpha-adrenergic receptors to cause vasoconstriction 1
• Vasopressin causes vasoconstriction by binding to V1 receptors on vascular smooth muscle, providing a non-adrenergic mechanism of action 4
• The pressor effect of vasopressin reaches its peak within 15 minutes and fades within 20 minutes after stopping the infusion 4
• Dobutamine has both alpha and beta effects, with the vasodilating beta-adrenergic effects often counterbalancing the vasoconstricting alpha effects 1