Postoperative ICU length of stay (LOS) is a key determinant of outcomes following cardiac surgery. Prolonged ICU stay is associated with increased complications, resource utilization, and hospital costs.Early identification of patients at risk for prolonged ICU stay is critical in cardiac surgery. Previous studies have validated VIS in pediatric and adult populations for predicting morbidity and mortality. The vasoactive–inotropic score (VIS), originally described in pediatric cardiac surgery, quantifies cumulative vasoactive and inotropic support. The vasoactive-inotropic score (VIS) is calculated as a weighted sum of all administered inotropes and vasoconstrictors, reflecting pharmacological support of the cardiovascular system.^(1,2) This score originally was developed as “inotropic score”(IS) by Wernovsky et al. in 1995.(3) The original IS was calculated as dopamine dose (mcg/kg/min) + dobutamine dose (mcg/kg/min) + 100 x epinephrine dose(mcg/kg/min).Subsequently, Gaies et al. upgraded it to VIS, adding norepinephrine, vasopressin, and milrinone in 2010. The VIS is, therefore, calculated as dopamine dose (mcg/kg/min) + dobutamine dose (mcg/kg/min) + 100x epinephrine dose (mcg/kg/min) + 100x norepinephrine dose (mcg/kg/min) + 10,000x vasopressin dose (U/kg/min) + 10x milrinone dose (mcg/kg/min) Favia et al. introduced a further correction to include levosimendan in the score in 2013. In their update, the authors assigned a factor of 50 to levosimendan dose, expressed in mcg/kg/min.(4) In the same year, Nguyen et al. introduced a correction factor of 10 for the phenylephrine dose, expressed in mg/kg/min.⁽⁵⁾ Landoni et al. also included enoximone in their version of VIS, with no correction factor for the enoximone dose in mcg/kg/min and considering enoximone 10 times more potent than milrinone.^(6-10) Yamazaki et al. added the phosphodiesterase-3 inhibitor olprinone in the calculation of VIS, assigning a factor 10 to the dose of olprinone in mg/kg/min,32 although a different group suggested 25 as correction factor.^(11-12) Higher VIS reflects greater hemodynamic instability and severity of illness. Although VIS has been linked to mortality and morbidity, limited evidence exists regarding its predictive ability for prolonged ICU stay in adult cardiac surgical patients. This study evaluates the predictive performance of VISmax for prolonged ICU stay (>48 hours). Our findings demonstrate near-perfect discrimination (AUC 0.995), exceeding previously reported AUC values ranging from 0.75–0.85 in adult cohorts.

Study Design Prospective observational study. Study Population A total of 107 patients undergoing cardiac surgery were included. Outcome Definition Prolonged ICU stay was defined as ICU stay >48 hours. Data Collection As per institutional policy, after surgery patient is shifted to ICU. Inotropes and vasopressors were rationalized. Vasoactive ionotropic score calculated using standard formula during postoperative period. VISmax calculated in first 12 hours postoperatively. Statistical Analysis • Continuous variables expressed as mean ± SD or median (IQR). • Mann–Whitney U test used for group comparison. • ROC curve analysis performed to determine predictive ability. • P < 0.05 considered statistically significant.

TABLE 1: Baseline VISmax Distribution

TABLE 2: Association of VISmax with Prolonged ICU Stay

*Mann–Whitney U test:Patients with prolonged ICU stay had significantly higher VISmax (P < 0.0001).

Logistic regression demonstrated strong association between VISmax >15.5 and prolonged ICU stay (Odds Ratio 1891.00; 95% CI 73.64–48556.74).

TABLE 3: Multivariate Logistic Regression Analysis

TABLE 4:ROC Curve Analysis

 VISmax demonstrated outstanding discrimination (AUC 0.995).

Figure 1: ROC Curve

Inotropic use is frequently required in the cardiac surgery intraoperatively(2,14,15). Besides, the inotropic drug requirement is influenced by many factors such as patient characteristics, surgical procedure, CPB and ACC times, amount of bleeding, and type of treatment given in the ICU but in our study we took the vis max in first 12 hours which accounts for the most dynamic time post cardiac surgery with a lot of hemodynamic fluctuations and is crucial for predicting the outcome. The management of these patients relies on multiple strategies intended to mitigate the potential threat of low cardiac output. As part of this management, inotropic and vasoactive agents are routinely employed after cardiac surgery to decrease the risk of low cardiac output.(16)

Our results show stronger predictive performance compared to earlier studies reporting moderate discrimination in cardiac surgical patients. The AUC of 0.995 indicates near-perfect discrimination. The near-perfect specificity suggests VISmax may serve as a clinical triage tool. The cut-off >15.5 provided excellent sensitivity and specificity. These findings align with previous literature demonstrating VIS as a marker of postoperative severity and adverse outcomes. Comparison with Koponen et al. and Magoon et al. indicates higher effect magnitude in our cohort. Clinically, VISmax may serve as an early, objective, and easily calculable bedside tool for risk stratification.(1,17)

In the results of the ROC analyses performed in our study, the predictability of the VIS max cutoff values in predicting prolonged icu stay was found to be significant (P< 0.01). The cutoff value for VISmax was 15.5. In some studies in the literature, cutoff values are reported to be between 15 and 20 in pediatric cardiac surgery and between 4.5 and 5.5 in adult cardiac surgery, and the difference in the values in the pediatric population is explained by decreased beta adrenergic receptors.(13,16,18, 12)

Contrary to our findings Butts et al. studied vis max in neonatal cardiac surgery patients and found maximum VIS was moderately correlated with some early postoperative outcomes. However, given its inability to discriminate early postoperative outcomes, it is likely to be imprecise in differentiating long-term outcomes and thus a poor choice for use as a surrogate outcome in future clinical trials involving this particular population. Maximum VIS, although superior to LCOS, has only a modest correlation with length of postoperative mechanical ventilation, postoperative ICU LOS, and total hospital charges.(19)

Baysal PK et al. conducted a study patients undergoing CABG and concluded VIS is the most critical and EuroSCORE is the second most important scoring systems. They independently predict combined morbidity and mortality in undergoing elective coronary artery bypass surgery.(16) These findings suggest that the decision to increase vasopressor or inotrope dosage should be carefully decided after considering a risk-benefit analysis of the drugs. We opine from our study that high VIS was likely to be a marker for poor cardiac physiology (e.g. ventricular dysfunction) in the immediate post‑operative period. This poor physiology might lead to prolonged therapies, more frequent complications and borderline pulmonary function that impaired convalescence, particularly feeding.

LIMITATIONS

Single-center study

Moderate sample size

Lack of multivariate regression adjusting for confounders

Future studies should validate findings in multicenter cohorts.

VISmax is an outstanding predictor of prolonged ICU stay (>48 hours) following cardiac surgery. A threshold >15.5 provides excellent diagnostic performance and may guide early ICU resource allocation and risk stratification.

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