Glycemic Variability and Autonomic Nervous System in Cardiac Surgery Patients

On-pump coronary artery bypass graft (CABG) and valve replacement surgeries are high-risk procedures. Among the risk factors for postoperative complications, perioperative hyperglycemia and blood glucose variability have been reported to be associated with increased morbidity and mortality. The treatment of hyperglycemia using intravenous insulin infusion improves the prognosis in cardiac surgery patients. However, the determinants of postoperative blood glucose variability and the mechanisms leading to its deleterious impact are unknown. Thus, to date, there is no therapeutic intervention that could effectively prevent and treat the deleterious impact of glycemic variability on postoperative outcome. The purpose of the study is to evaluate whether perioperative alteration of the autonomic nervous system and preoperative blood glucose variability could be related to perioperative glycemic variability.

The main objective is to describe the relationship between preoperative glycemic variability and glycemic variability during the first 48 postoperative hours.

The secondary objectives are :

1. to describe the relationship between preoperative glycemic variability and glycemic variability during the first 48 hours postoperative according to:

   * diabetic and non-diabetic status
   * the type of surgical intervention
2. to describe the relationship between the parameters evaluating the preoperative activity of the autonomic nervous system and:

   * preoperative glycemic variability
   * glycemic variability during the first 48 postoperative hours
3. to describe the relationship between glycemic variability during the first 48 postoperative hours and:

   * parameters evaluating the activity of the autonomic nervous system during the first 48 postoperative hours
   * diabetes phenotype
   * markers of inflammation
   * markers of endothelial dysfunction
4. to describe the morbidity and mortality within 30 days after surgery.

Eligibility Criteria:
Inclusion Criteria:

* Planned cardiac surgery
* Age ≥ 18 years old and \< 80 years old
* Group 1: patients with known insulin-requiring type 2 diabetes mellitus undergoing planned on-pump coronary artery bypass surgery
* Group 2: patients with known non-insulin-requiring type 2 diabetes mellitus undergoing planned on-pump coronary artery bypass surgery
* Group 3: non-diabetic patients undergoing planned aortic valve replacement surgery
* Group 4: non-diabetic patients undergoing planned on-pump coronary artery bypass surgery

Exclusion Criteria:

* Emergent surgery (less than 48 hours between anesthestetic consultation and surgery)
* Combined surgery (coronary artery bypass graft associated with valve surgery, multiple valve replacement, surgery of the ascending aorta)
* Extreme weight: body mass index (BMI) \> 35 kg.m-2 or \< 18 kg.m-2.
* Off-pump coronary artery bypass graft surgery
* Type 1 diabetes mellitus
* Patient unable to consent
* Pregnant and/or breastfeeding woman
* Permanent preoperative chronic heart rhythm disorder
* Pacemaker
* Unstable patient condition in preoperative period
* Expected life expectancy less than 48 hours.
* Subject unlikely to cooperate in the study and/or low cooperation anticipated by the investigator.
* Duration of continuous preoperative glycemic recording of less than 48 hours.