Inotropic Effects of Vasopressin Versus Noradrenaline In Patients With Vasoplegic Syndrome After Cardiac Surgery

Inotropic Effects of Vasopressin Versus Noradrenaline In Patients With Vasoplegic Syndrome After Cardiac Surgery

This is a randomized, double-blind clinical trial designed to compare the inotropic effects of vasopressin versus norepinephrine in patients who develop vasoplegic syndrome in the immediate postoperative period following cardiac surgery.

Vasoplegic syndrome is characterized by severe hypotension due to systemic vasodilation, despite adequate fluid resuscitation and preserved or elevated cardiac output. Vasopressors are essential in restoring hemodynamic stability in this context; however, their impact on myocardial performance remains uncertain. While norepinephrine is the standard first-line agent, vasopressin has shown potential benefits, including reduced catecholamine exposure and fewer adverse cardiovascular effects.

This study aims to assess changes in cardiac output and other echocardiographic and hemodynamic parameters after administration of either vasopressin or norepinephrine. The findings are expected to contribute to optimizing vasopressor selection in vasoplegic patients after cardiac surgery and improving clinical outcomes.

This prospective, randomized, double-blind clinical trial investigates the inotropic effects of vasopressin versus norepinephrine in patients who develop vasoplegic syndrome (VS) in the immediate postoperative period following cardiac surgery.

Vasoplegic syndrome is characterized by severe hypotension with low systemic vascular resistance despite adequate cardiac output, often unresponsive to standard fluid resuscitation and catecholamine vasopressors. It is associated with significant morbidity and mortality, especially in cardiac surgery patients. In recent years, vasopressin has been explored as an alternative or adjunctive treatment due to its different mechanism of action and potentially fewer adverse effects compared to catecholamines.

Eligible patients (≥18 years) undergoing coronary artery bypass grafting or valve surgery, who develop vasoplegic syndrome within 24 hours postoperatively, will be randomized in a 1:1 ratio to receive vasopressin or norepinephrine. Drug allocation will be blinded to the clinical and research teams, with identically prepared infusion bags.

The study protocol includes a detailed vasopressor infusion regimen, beginning at 5 mL/h with titration every 10 minutes to a maximum of 30 mL/h, aiming for a target mean arterial pressure (MAP) ≥65 mmHg. Hemodynamic parameters (SBP, DBP, MAP, HR, lactate, SVO₂, CO₂ gap) and echocardiographic indices (LVEF, TAPSE, VTI, CO, SVR) will be collected at baseline (T0) and upon reaching the MAP goal (T1).

Primary endpoint: Comparative assessment of the inotropic effects between the two vasopressors based on echocardiographic and hemodynamic changes from T0 to T1.

Sample size: 175 patients per arm, considering a 30% effect size and 5% attrition rate, powered at 80% with a 5% type I error.

Statistical analysis will follow an intention-to-treat approach using appropriate parametric and non-parametric tests, with p-values <0.05 considered statistically significant.

This trial is expected to provide clinically relevant data on the efficacy and safety of vasopressin in improving myocardial performance in vasoplegic patients, potentially supporting its use as a first-line vasopressor in this context

Inclusion Criteria:

• Age over 18.
• Patients undergoing coronary artery bypass grafting, valve surgery or both, with a diagnosis of vasoplegic syndrome in the immediate postoperative period (<24 hours), defined as mean arterial pressure < 65 mmHg (measured using an invasive blood pressure catheter) and resistance to fluid replacement - at least 1000ml of crystalloids.

Exclusion Criteria:

• Pregnancy or breastfeeding.
• Aortic surgery.
• Surgeries to correct congenital heart disease.
• Heart transplants.
• Emergency surgery.
• Use of vasopressor therapy in the preoperative period.
• Presence of a ventricular assist device other than an intra-aortic balloon in the postoperative period.
• Severe hyponatremia in the postoperative period (serum sodium less than 130mEq/l).
• Postoperative acute coronary syndrome.
• Mesenteric ischemia in the postoperative period.
• History of Raynaud's disease.
• History of neoplasia.