Differential Regulation of RAAS-axis in Patients Undergoing Cardiac Surgery

In patients undergoing cardiac surgery, the occurrence of vasoplegia or vasoplegic shock is a common and sometimes very severe complication. Although there are multiple factors that may affect the incidence and severity of vasoplegia, it remains unclear which role the use of cardiopulmonary bypass may play in the pathogenesis of this complication. The heart normally pumps blood through the lungs where the blood primarily gets oxygenated. However, it is also known that pulmonary blood flow is also essential for the activation of various hormones, some of which are central to the regulation of vascular tension and blood pressure. If the pulmonary circulation is bypassed, as is the case in on-pump cardiac surgery, it is likely that the resulting differential activity of hormones may cause or contribute to the incidence of vasoplegia. This study aims to show whether cardiopulmonary bypass leads to the differential regulation of hormones of the renin-angiotensin-aldosterone-system which could explain why some patients suffer from vasoplegia or vasoplegic shock following such procedures.

Inclusion criteria

• adult patients undergoing on- or off-pump coronary artery bypass graft surgery
• written informed consent

Exclusion criteria

• emergency surgery in the context of acute coronary syndrome
• ACE-inhibitor or Angiotensin 1 (AT1)-receptor-blocker intake that was not paused on the day of surgery
• Chronic kidney disease with estimated glomerular filtration rate (eGFR)<30ml/min/1.73m²
• Severe structural lung disease (asbestosis, silicosis, severe sarcoidosis, tuberculosis, severe emphysema, chronic obstructive pulmonary disease (COPD) Gold 3-4, lung fibrosis)
• Chronic pulmonary hypertension
• Pregnancy or breastfeeding
• Persons with any kind of dependency on the investigator or employed by the institution responsible or investigator
• Persons held in an institution by legal or official order