Heart rate variability reflects the autonomic nervous system on the intrinsic activity of sinus node cells. Sympathetic hyperactivity is an adaptation to stress, while parasympathetic hyperactivity is present at rest. Thus, any variability in the heart frequency rate reflects variations in sympathetic and parasympathetic components in the autonomic nervous system. Failure to return to normal or a reduction in the variability of the heart rate in the postoperative period is correlated with complications in colorectal surgery.

Inclusion Criteria:

• Patients operated for a scheduled colorectal resection due to cancer, diverticulitis, or Chronic Inflammatory Bowel Disease,
• American Society of Anesthesiologists score 1-2
• The patient must have given their free and informed consent and signed the consent form
• The patient must be a member or beneficiary of a health insurance plan

Exclusion Criteria:

• Patient taking antidepressants, antipsychotics, antihypertensive beta blocker type, anti-arythmic or oral contraception
• Uncontrolled diabetes or associated with a neuropathy
• Arrhythmias and conduction disturbances, , coronaropathy and heart failure, kidney failure
• Neuropathies
• Pacemaker or defibrillator
• The subject is participating in another interventional study, or is in a period of exclusion determined by a previous study
• The subject refuses to sign the consent
• It is impossible to give the subject informed information
• The patient is under safeguard of justice or state guardianship

All patients undergoing scheduled colorectal resection or operated on in the digestive surgery department of the CHU Nîmes