What cardiac function tests are required before administering a vasopressor?

Cardiac Function Testing Prior to Vasopressor Administration

No formal cardiac function testing is required before initiating vasopressors in acute hypotensive emergencies, but rapid bedside assessment of volume status and cardiac function should be performed when feasible to guide therapy. 1

Initial Assessment Strategy

Immediate Clinical Evaluation

• Vasopressors should be administered simultaneously with fluid replacement to prevent and decrease duration of hypotension, rather than delaying for formal testing 2
• Blood volume depletion should be corrected as fully as possible before vasopressor administration, though in emergencies vasopressors can be given before and concurrently with volume replacement 3
• Early baseline assessment of volume status, perfusion, and cardiovascular function should be performed in all critically ill patients with hypotension 1

Bedside Echocardiography When Available

• Bedside transthoracic echocardiography (TTE) is reasonable to evaluate volume status and cardiac function in patients with hypotension or shock, but should not delay vasopressor initiation 1
• TTE can assess left ventricular and right ventricular contractility, structural/valvular abnormalities, and guide the use of inotropes and vasopressors once optimal intravascular volume is achieved 1
• An assessment of cardiac function during initial ultrasound is essential because vasopressors may increase cardiac afterload if left ventricular function is impaired 1

Critical Monitoring During Vasopressor Use

Hemodynamic Monitoring

• Invasive hemodynamic monitoring (arterial and central venous catheter) may be needed for adequate assessment of cardiac function and titration of vasopressors and fluid resuscitation 1, 4
• Arterial lines facilitate earlier detection of hypotension and allow regular arterial blood gas analysis 1
• Continuous monitoring of ECG, blood pressure, oxygen saturation, urine output, and serum lactate is recommended when using vasopressors 4

Cardiac Dysfunction Recognition

• Cardiac dysfunction must be suspected in the presence of poor response to fluid expansion and norepinephrine, particularly in the absence of cardiac output monitoring 1
• The presence of myocardial dysfunction requires treatment with an inotropic agent such as dobutamine or epinephrine 1
• Dobutamine (starting at 2-5 mcg/kg/min) should be added when hypotension is due to low cardiac output states, after blood pressure is stabilized with norepinephrine 4

Common Pitfalls and Caveats

Avoiding Delays in Treatment

• Do not delay vasopressor initiation to obtain formal echocardiography in life-threatening hypotension 3, 2
• Norepinephrine can be started via large peripheral vein in shocked patients until central access is established 1
• Target mean arterial pressure (MAP) of 65 mm Hg should be maintained with ongoing assessment of end-organ perfusion 1, 4

Understanding Limitations of Testing

• Echocardiographic left ventricular ejection fraction (LVEF) alone does not predict vasopressor requirements or mortality after cardiac arrest 5
• Doppler hemodynamic parameters (stroke volume, cardiac power output, left ventricular stroke work index) correlate better with vasopressor requirements than LVEF alone 6
• Decreased left ventricular systolic function is associated with increased vasopressor use, but the relationship is complex and not captured by TTE assessment alone 6

Special Considerations

• In trauma patients, cardiac dysfunction could be altered following cardiac contusion, pericardial effusion, or secondary to brain injury with intracranial hypertension 1
• For patients with cirrhosis and refractory shock, consider screening for adrenal insufficiency or empiric hydrocortisone 50 mg IV every 6 hours 1
• Vasopressin can worsen cardiac function (decrease cardiac index), so monitoring is important 7