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

Overview

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.

Detailed description

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

Interventions

• Drug Vasopressin intravenous infusion
  Vasopressin will be administered intravenously in a blinded 250 mL bag of 5% glucose solution, at a final concentration of 0.12 U/mL. The infusion will begin at 5 mL/h and be increased by 2.5 mL/h every 10 minutes during the first hour, up to a maximum rate of 30 mL/h (equivalent to doses from 0.01 to 0.06 U/min). The target is to reach and maintain mean arterial pressure (MAP) ≥65 mmHg. If this is not achieved, open-label norepinephrine may be added. Hemodynamic and echocardiographic parameters
• Drug Norepinephrine intravenous infusion
  Norepinephrine will be administered intravenously in a blinded 250 mL bag of 5% glucose solution, at a final concentration of 120 µg/mL. The infusion will begin at 5 mL/h and be increased by 2.5 mL/h every 10 minutes during the first hour, up to a maximum rate of 30 mL/h (equivalent to doses from 10 to 60 µg/min). The goal is to reach and maintain MAP ≥65 mmHg. If the MAP target is not reached, open-label norepinephrine may be initiated. Clinical and hemodynamic parameters will be collected at b

Primary outcome measures

• Change in inotropic function assessed by cardiac output between T0 and T1 [Time frame: Up to 1 hour after initiation of vasopressor therapy]

Secondary outcome measures (7)

• Change in left ventricular ejection fraction (LVEF) between T0 and T1 [Time frame: Up to 1 hour after vasopressor initiation]
• Time to achieve target mean arterial pressure (MAP ≥65 mmHg) [Time frame: Up to 1 hour]
• Change in heart rate (HR) between T0 and T1 [Time frame: Up to 1 hour]
• Change in arterial lactate levels between T0 and T1 [Time frame: Up to 1 hour]
• Change in central venous oxygen saturation (SvO₂) [Time frame: Up to 1 hour]
• Change in CO₂ gap (central venous-to-arterial CO₂ difference) [Time frame: Up to 1 hour]
• Need for additional open-label norepinephrine [Time frame: During initial vasopressor titration (up to 1 hour)]

Eligibility criteria

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.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Quadruple blind

Primary purpose

Treatment

Study locations

Brazil · 1 center

• Instituto do Coração HCFMUSP — São Paulo

Publications

• Belletti A, Musu M, Silvetti S, Saleh O, Pasin L, Monaco F, Hajjar LA, Fominskiy E, Finco G, Zangrillo A, Landoni G. Non-Adrenergic Vasopressors in Patients with or at Risk for Vasodilatory Shock. A Systematic Review and Meta-Analysis of Randomized Trials. PLoS One. 2015 Nov 11;10(11):e0142605. doi: 10.1371/journal.pone.0142605. eCollection 2015. PMID 26558621
• Pelletier JS, Dicken B, Bigam D, Cheung PY. Cardiac effects of vasopressin. J Cardiovasc Pharmacol. 2014 Jul;64(1):100-7. doi: 10.1097/FJC.0000000000000092. PMID 24621650
• Dunser MW, Mayr AJ, Ulmer H, Knotzer H, Sumann G, Pajk W, Friesenecker B, Hasibeder WR. Arginine vasopressin in advanced vasodilatory shock: a prospective, randomized, controlled study. Circulation. 2003 May 13;107(18):2313-9. doi: 10.1161/01.CIR.0000066692.71008.BB. Epub 2003 May 5. PMID 12732600
• Hamzaoui O, Jozwiak M, Geffriaud T, Sztrymf B, Prat D, Jacobs F, Monnet X, Trouiller P, Richard C, Teboul JL. Norepinephrine exerts an inotropic effect during the early phase of human septic shock. Br J Anaesth. 2018 Mar;120(3):517-524. doi: 10.1016/j.bja.2017.11.065. Epub 2017 Nov 21. PMID 29452808
• Hamzaoui O, Georger JF, Monnet X, Ksouri H, Maizel J, Richard C, Teboul JL. Early administration of norepinephrine increases cardiac preload and cardiac output in septic patients with life-threatening hypotension. Crit Care. 2010;14(4):R142. doi: 10.1186/cc9207. Epub 2010 Jul 29. PMID 20670424
• Elgebaly AS, Sabry M. Infusion of low-dose vasopressin improves left ventricular function during separation from cardiopulmonary bypass: a double-blind randomized study. Ann Card Anaesth. 2012 Apr-Jun;15(2):128-33. doi: 10.4103/0971-9784.95076. PMID 22508204
• Gordon AC, Mason AJ, Perkins GD, Ashby D, Brett SJ. Protocol for a randomised controlled trial of VAsopressin versus Noradrenaline as Initial therapy in Septic sHock (VANISH). BMJ Open. 2014 Jul 3;4(7):e005866. doi: 10.1136/bmjopen-2014-005866. PMID 24993769
• Russell JA, Walley KR, Singer J, Gordon AC, Hebert PC, Cooper DJ, Holmes CL, Mehta S, Granton JT, Storms MM, Cook DJ, Presneill JJ, Ayers D; VASST Investigators. Vasopressin versus norepinephrine infusion in patients with septic shock. N Engl J Med. 2008 Feb 28;358(9):877-87. doi: 10.1056/NEJMoa067373. PMID 18305265

Identifiers

NCT: NCT06934798 · 16286719.1.0000.8069

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗