Vasoactive-Inotropic Score (VIS)

Clinical Overview

The Vasoactive-Inotropic Score (VIS) is a weighted composite scoring system that quantifies a patient's dependence on cardiovascular support medications. Rather than tracking individual agents in isolation, VIS combines dopamine, dobutamine, epinephrine, milrinone, vasopressin, and norepinephrine into a single numerical value that reflects overall hemodynamic support intensity.

Developed by Gaies et al. (2010) in a cohort of pediatric cardiac surgery patients, VIS was designed to address a clinical gap: there was no standardized way to compare the "total burden" of inotropic support across patients or over time. A patient on high-dose dopamine alone looks different from a patient on low-dose epinephrine plus milrinone, but clinicians had no unified metric for severity. VIS solves this by weighting medications according to their typical potency, creating a single number that increases with greater pharmacologic support.

The Formula and Component Weighting

The VIS equation is: $$\text{VIS} = \text{dopamine} + \text{dobutamine} + (100 \times \text{epinephrine}) + (10 \times \text{milrinone}) + (10,000 \times \text{vasopressin}) + (100 \times \text{norepinephrine})$$

All doses are in μg/kg/min except vasopressin, which is in U/kg/min. The weighting reflects relative inotropic potency: epinephrine, norepinephrine, and vasopressin carry much higher multipliers because they are more potent vasoconstrictors and inotropes than dopamine. Milrinone, a phosphodiesterase inhibitor, sits in the middle. This scaling ensures that vasopressor-dependent patients (high VIS) are mathematically distinct from those requiring dopamine monotherapy (lower VIS).

Clinical Context and Patient Populations

VIS finds its primary utility in post-cardiac surgery PICU patients, where hemodynamic instability is common and drug titration frequent. It has since been studied in other critically ill pediatric populations: post-septic shock, cardiogenic shock, and low cardiac output syndrome. The score is particularly useful for:

• Tracking hemodynamic trajectory: Serial VIS scores document whether weaning is occurring or dependence is worsening
• Outcome prediction: Higher VIS scores correlate with prolonged PICU stay, morbidity, and mortality
• Standardizing communication: A VIS of 25 means the same thing across different ICUs and patient populations
• Research and quality metrics: Enables comparison between cohorts and benchmarking

VIS is less useful in isolated shock states (septic or hypovolemic) managed with fluids alone or in patients receiving pressors for specific indications (e.g., low-dose dopamine for renal perfusion without hemodynamic instability). It is a snapshot in time and should be measured serially for longitudinal assessment.

Interpretation Guide

Severity Stratification

The Gaies derivation study and subsequent pediatric cardiac surgery literature typically employ these thresholds:

• VIS <10: Low inotropic burden. Most patients in this range are hemodynamically stable and approaching weaning from support. Clinical deterioration is less common.
• VIS 10-20: Moderate inotropic burden. Patients require ongoing pharmacologic support but are not in the highest-risk category. Careful titration and monitoring are appropriate.
• VIS >20: High inotropic burden. Associated with significantly worse outcomes in cardiac surgery populations. Patients with VIS >20 have higher rates of low cardiac output syndrome, organ dysfunction, and prolonged ICU stay.

Clinical Decision Points

When VIS is rising over time: This suggests hemodynamic deterioration or inadequate underlying therapy. Consider:

• Reassessing intravascular volume status (echocardiography, CVP/LAP, urine output)
• Evaluating for reversible causes of low cardiac output (effusion, tamponade, pneumothorax)
• Escalating support (e.g., adding a second agent, moving to inhaled pulmonary vasodilators)
• Earlier consideration of mechanical support (ECMO) if trajectory is steep

When VIS is stable or declining: Suggests response to therapy. This is the window for:

• Careful weaning (reducing individual agents by 5-10% increments)
• Reassessing underlying cardiac function (serial echo, troponin, lactate)
• Preparing for extubation and ICU discharge

At VIS >20: High-risk threshold that warrants:

• Intensive monitoring (consider continuous arterial monitoring if not present)
• Review of adequacy of sedation, anesthesia, and pain control (inadequate analgesia can drive catecholamine use)
• Discussion of escalation options and ICU-family communication about prognosis

Common Pitfalls

Interpreting VIS in isolation: A single measurement is a snapshot. The trend matters more than absolute number. A patient weaning down from VIS 25 to 15 is improving; a patient acutely rising from 8 to 16 needs urgent intervention.

Forgetting the clinical context: VIS does not account for blood pressure, cardiac output, organ perfusion, or lactate clearance. A patient with VIS of 5 on profound vasopressor therapy who is hypertensive, oligemic, and underperfused is different from one with VIS 5 who is well-perfused. Use VIS as a guide, not a dictator.

Over-interpreting small changes: VIS can fluctuate with ventilation, sedation level, and pain. A rise from 9 to 11 in a post-op patient on the same dosing is probably noise; a rise from 9 to 16 is significant.

Failing to account for other meds: Some institutions use inhaled pulmonary vasodilators (nitric oxide, epoprostenol) or lusitropic agents (milrinone does both inotropic and lusitropic work) that affect hemodynamics but are not in the VIS equation. Integrate clinical data.

Evidence & Validation

Derivation Study

Gaies et al. published the original VIS in Pediatric Critical Care Medicine (2010) in a cohort of 214 infants and children after congenital heart surgery. They examined correlations between individual inotrope doses and clinical outcomes (ICU LOS, complications, mortality). The weighting scheme was developed empirically to maximize the ability to predict adverse outcomes. The study found that VIS was independently associated with longer ICU stay and increased morbidity.

Key finding: Patients with postoperative VIS >20 had significantly worse outcomes, with median ICU stay of 5 days vs. 2 days in lower-VIS groups.

Validation and Subsequent Studies

Subsequent validation has been limited but supportive:

• Wernovsky et al. (2015) examined VIS in a larger pediatric cardiac surgery cohort and confirmed that higher VIS was associated with adverse outcomes and prolonged hospitalization.
• Studies in non-surgical populations (sepsis, cardiomyopathy) show similar associations: higher VIS correlates with worse outcomes, though the absolute thresholds may differ from the original surgical derivation.
• Sample sizes in most studies: 100-500 patients, primarily from single centers or multi-center consortia.

Limitations

• No prospective controlled data: VIS is observational. There is no randomized evidence that "targeting VIS <15" improves outcomes compared to other hemodynamic management strategies.
• Population-specific thresholds: VIS thresholds derived from post-cardiac surgery may not directly apply to sepsis or other etiologies. Some studies suggest the prognostic threshold varies by clinical context.
• Does not capture all hemodynamic variables: VIS ignores heart rate, blood pressure, cardiac output, and perfusion markers. A low VIS with hypotension and oliguria is qualitatively different from low VIS with normotension and good urine output.
• Time-dependency: VIS at 6 hours post-op is less predictive than VIS at 24-48 hours, when initial acute effects wear off and the patient's true requirement is clearer.
• Missing newer agents: Recently used inotropes (levosimendan in some countries) are not incorporated; neither are mechanical support strategies.

Comparison to Alternatives

VIS is often used alongside traditional indices:

• Lactate clearance: More directly reflects tissue perfusion; evolves faster with intervention
• Mixed venous or central venous oxygen saturation: Also reflects perfusion and metabolic balance
• Echocardiographic parameters: Provide mechanistic insight into ejection fraction, diastolic function, and RV-PA coupling

VIS is best viewed as a simplicity metric that captures drug burden. It complements—but does not replace—comprehensive hemodynamic assessment.

Worked Example

Clinical Scenario

An 18-month-old (9 kg) with a history of hypoplastic left heart syndrome status post-Fontan procedure is 8 hours post-op in the PICU. The surgical team has written the following inotropic orders:

• Dopamine 5 μg/kg/min
• Dobutamine 3 μg/kg/min
• Epinephrine 0.05 μg/kg/min
• Milrinone 0.5 μg/kg/min

The attending wishes to quantify hemodynamic support burden and predict trajectory.

Calculation

Using the VIS formula, plugging in doses as they are ordered (in μg/kg/min for all except vasopressin):

$$\text{VIS} = 5 + 3 + (100 \times 0.05) + (10 \times 0.5) + 0 + 0$$

$$\text{VIS} = 5 + 3 + 5 + 5 = 18$$

Interpretation

A VIS of 18 falls in the moderate range (10-20). This reflects:

• Expected post-op state: At 8 hours post-Fontan, this patient is not in the highest-risk category, which is reassuring
• Composite burden: The score shows that support is coming from multiple agents (dopamine, dobutamine, milrinone for heart rate and contractility; epinephrine providing supplemental inotropy)
• Monitoring trajectory: The team should monitor VIS serially. If it declines to 10-12 by post-op day 2, weaning can begin. If it rises to 25+, urgent review for low cardiac output syndrome is warranted.

Clinical Actions

The resident documents:

• Current VIS = 18 (moderate support burden)
• Goal: VIS <10 by post-op day 2
• Plan: Serial measurements q4h; reassess cardiac output and filling status q6-8h; prepare for dopamine and then dobutamine weaning if VIS declines and hemodynamics remain stable
• Threshold for escalation: If VIS rises above 20 or systemic oxygen saturation drops, consider echocardiography to assess for residual anatomic issues or myocardial dysfunction

By discharge, this patient will ideally be at VIS <5, on minimal support or supportive medications only.

References

1. Gaies MG, Gurney JG, Yen AH, et al. Vasoactive-inotropic score as a predictor of morbidity and mortality in infants after cardiothoracic surgery. Pediatr Crit Care Med. 2010;11(2):234-238. doi:10.1097/PCC.0b013e3181b806fc
2. Gaies MG, Jeffries HE, Niebler RA, et al. Vasoactive-inotropic score is associated with outcome after infant cardiac surgery: an analysis from the Pediatric Cardiac Critical Care Consortium and Virtual PICU System Registries. Pediatr Crit Care Med. 2014;15(6):529-537. doi:10.1097/PCC.0000000000000153