Inclusion Criteria:  Age ≥ to 18 years old Admission to intensive care unit for traumatic brain injury or subarachnoid hemorrhage without other life-threatening injury Patients under sedation with administration of opiate-agonists, μ receptor agonists (Sufentanil, Fentanyl, Remifentanil, Morphine) for less than 24 hours Expected duration of invasive mechanical ventilation and sedation of 72 hours or more Intracranial pressure monitoring Enteral feeding by oro / nasogastric tube Affiliated or beneficiary of the French social security system  Exclusion Criteria:  Patient who received opioids for more than 24 hours Patient with refractory intracranial hypertension at the time of inclusion: intracranial hypertension requiring therapy other than analgo-sedation (thiopental, targeted temperature management, decompressive craniectomy) Acute or chronic renal failure with creatinine clearance <60ml / min Known or suspected acute gastrointestinal obstruction  Risk of digestive perforation:  history of peptic ulcer Crohn's disease Ogilvie syndrome acute diverticulitis infiltrating gastrointestinal tumor recurrent or advanced ovarian cancer peritoneal metastasis recent abdominal trauma with risk of digestive perforation Concomitant treatment with a strong or moderate inhibitory effect of CYP 3A4 (For example: clarithromycin, ketaconazole, itraconazole, telithromycin, ritonavir, indinavir, saquinavir) or with a strong inducing effect (carbamazepin, rifampicin, millepertuis) Concomitant treatment with vascular endothelial growth factor (VEGF) inhibitor Allergy to Naloxegol or one of its excipients Recent history of myocardial infarction within the past 6 months, symptomatic congestive cardiovascular disease, QT ≥ 500 msec Patient with a medical decision for rapid palliative care Pregnancy and / or breastfeeding Child Pugh C stage cirrhosis Patient under legal protection or deprived of liberty Patient with another life-threatening injury History of clinically important alterations of the blood-brain barrier: primary brain tumors, metastasis or other inflammatory pathologies in the CNS, active multiple sclerosis, Alzheimer's disease at an advanced stage.