The Analgesia Nociception Index (ANI) reflects the balance between sympathetic and parasympathetic tone. It is based on a specific interpretation of the R-R interval variation. During fluid removal by net ultrafiltration in patients with fluid overload and continuous renal replacement therapy, some data suggest that haemodynamic variation could be induced by the autonomic nervous system. The study aims to investigate ANI variations in this context and their association with the haemodynamic variations observed.

Inclusion Criteria:

• Continuous renal replacement therapy in intensive care unit

• Initiation of net ultrafiltration according to the protocol of the department or to EARLYDRY study (NCT 05817539) (3 criteria required):

  • Fluid overload > 5% or peripheral oedema
  • Noradrenaline equivalent <0.5μg/kg/min
  • No peripheral hypoperfusion

• Invasive blood pressure monitoring

• Central venous line in superior vena cava territory

• Regular sinus rhythm

• Patient awake or Richmond Agitation and Sedation Scale > -3

Exclusion Criteria:

• Ongoing administration of inotropes
• Ongoing administration of beta blockers
• Current administration of alpha-2 agonists
• History of dysautonomia
• Pregnant or breast-feeding woman
• Mechanical circulatory assistance
• Opposition to participate
• Adults under legal protection
• Persons deprived of their liberty by judicial or administrative decision

Critically ill patients with continuous renal replacement therapy, fluid overload and haemodynamically stable.