General anesthesia used to be based on the association of hypnotics and opioid drugs. But recent studies showed that opioids may be related to a many different complications, like respiratory distress, hyperalgesia.

Opioid free anesthesia (OFA) aim is to control de cardiovascular nociceptive response to the surgical stimulation. The scientific literature is not clear yet on the cardiovascular effect of the OFA. Optimization of the cardiac index proved its worth in reducing morbidity and mortality.

The purpose of this study is to increase our understanding of the impact of opioid free anesthesia on the cardiovascular system and to evaluate the effectiveness and the security of the technic.

General anesthesia used to be based on the association of hypnotics and opioid drugs. But recent studies showed that opioïds may be related to a many different complications, like respiratory distress, hyperalgesia etc… Those sides effects are known, but there might be some recent technics that could allow anesthesiologist to reduce those unintended symptoms. As surgery became an important pilar of the modern medicine even in fragile people, the weight of opioids sides effect increased.

Opioid free anesthesia (OFA) consists in the simultaneous administration of alpha2-agonist (for example the dexmedetomidine (DEXDOR)), sodium channel blocker (lidocaine), and N-methyl-D-aspartate (NMDA) antagonists receptors (Ketamine). Its aim is to control de cardiovascular nociceptive response to the surgical stimulation. The scientific literature is not clear yet on the cardiovascular effect of the OFA. Optimization of the cardiac index proved its worth in reducing morbidity and mortality. The investigators thinks that exploring the impact of two different general anesthesia technics on cardiac index, might allow anesthesiologists to have a better understanding of the anesthetic strategy applied to the patient.

General anesthesia with or without opioid is used on a daily basis at the hospital center of Montauban. The possible sides effects of OFA as well as those affiliate to balanced anesthesia are known by all the care workers.

The purpose of this study is to increase our understanding of the impact of opioid free anesthesia on the cardiovascular system and to evaluate the effectiveness and the security of the technic.

Inclusion Criteria:

• Eligible patients for scheduled total hip arthroplasty with general anesthesia.
• Patients with an American Society of Anesthesiologists (ASA) score between 1 and 3
• Patient who has received appropriate information and has provided informed consent.
• Patient with French social security system.

Exclusion Criteria:

• Patients eligible to rapid sequence intubation.
• Patients with medical contraindication to the use of OFA : allergy to one of the drug used in the protocol, spontaneous bradycardia under 40bpm or atrioventricular block.
• Patients with a medical condition that could alter measurement of cardiac index by NICCOMO™: acute pulmonary oedema, severe valvular heart disease, pulmonary hypertension, atrial fibrillation.
• Patients who cannot give their informed consent.
• Patients pregnant or breastfeeding.
• Patients odler than 90 years old or with a weigh superior at 150kg.

Randomized into two groups depending on the type of general anesthesia: Opioid free anesthesia (OFA), or anesthesia with opioid (OA)