Opioid-free anaesthesia with dexmedetomidine and lidocaine versus remifentanil-based anaesthesia in cardiac surgery: study protocol of a French randomised, multicentre and single-blinded OFACS trial

Standard anaesthesia and postoperative care in both groups

Anxiolysis may be administrated according to the practices of each centre. Preoperative chronic medication use will be managed as recommended by the French Society of Anesthesiology and Critical Care, and notably β blockers will be maintained on the day of the surgery, whereas calcium channel blockers and ACE inhibitors or equivalent will be stopped at least 24 hours before surgery.

Patients will be monitored according to the current guidelines for cardiac surgery36: electrocardioscopy, pulse oximetry, capnography, invasive arterial catheter for blood pressure measurement, jugular or subclavicular central catheter with continuous central venous pressure, rectal or vesical temperature and bispectral index.

After preoxygenation with a 100 FiO2 to achieve an end-expired oxygen fraction over 90%, general anaesthesia will be induced in both groups by using propofol (target concentration infusion (TCI)—site effect 1–5 µg/mL) or etomidate (0.2–0.5 mg/kg) in association with a neuromuscular blocker (cisatracurium 0.2 mg/kg or atracurium 0.5 mg/kg). Anaesthesia will be maintained using TCI of propofol or volatile anaesthesia to target a bispectral index between 40 and 60, and intermittent or continuous administration of neuromuscular blockers to obtain a train of 4 at 0. In the absence of specific guidelines or recommendations on this topic, the choice of hypnotic and paralysing drugs will be left at the discretion of the anaesthetist according to patient characteristics and local protocols. Patients will receive dexamethasone (0.1 mg/kg) and ketamine (0.2 mg/kg) at the beginning of anaesthesia, followed by a continuous infusion of ketamine (0.2 mg/kg/hour, stopped 45 min before the end of surgery), as recommended by the French guidelines.37

In cases of hypotension with a mean arterial pressure ≤65 mm Hg during the off-CPB period, circulatory intervention will be initiated with the use of vasopressors (ephedrine or phenylephrine or norepinephrine) in combination with fluid administration if required. Because the recommended threshold for mean arterial pressure (MAP) during the CPB period is large (50–80 mm Hg according to European Assocation for Cardio-Thoracic Surgery (EATCS) guidelines36), vasopressor use will be left at the discretion of the anaesthetist, with a lower value of 50 mm Hg, and after optimisation of pump flow. In cases of hypertension, antihypertensive drugs will be administrated (nicardipine 1 mg or urapidil 10 mg every 2–5 min to obtain adequate blood pressure). The maximal upper blood pressure level permitted will be determined between the anaesthetic and surgical team, and according to pre-existing protocols if existing.

Antibioprophylaxis will consist of cefazolin 2 g (+1 g every 4 hours and 1 g for CPB priming) or vancomycin 30 mg/kg in case of a history of allergy.

CPB will be carried out according to the recent guidelines and the local practices of each centre.36

At the end of surgery, patients will receive analgesia with paracetamol 1 g, nefopam 20 mg and a non-steroidal anti-inflammatory (ketoprofen or diclofenac at the discretion of the clinician).

After surgery, patients will be transferred under invasive mechanical ventilation to cardiac surgical ICU for postoperative care. Extubation will be performed in awakened patients with spontaneous ventilation under pressure support of no more than 10 cmH2O and positive end-expiratory pressure (PEEP) of no more than 5 cmH2O. In cases of ventilation for more than 48 hours, extubation will be performed after a successful spontaneous breathing trial (low-pressure ventilation with pressure support of 7–8 cmH2O and zero PEEP, or T-tube trial; absence of polypnoea, hypoxaemia, agitation, tachycardia or hypertension within 30 min of the trial).38 Then, oxygen will be administrated if required to obtain SpO2 between 92% and 96%.

Circulation management (fluid therapy and vasoactive drugs) will be conducted according to each centre practice, with an objective of a mean arterial pressure of at least 65 mm Hg.

Postoperative analgesia within the first 48 hours will be performed using paracetamol 1 g/6 hours (intravenous or oral), nefopam 80 mg/day by continuous infusion, ketoprofen or diclofenac every 8 hours (respectively 100 and 75 mg, or 50 and 50 mg if weight <70 kg) and patient-controlled analgesia based on morphine 1 mg and droperidol 0.05 mg/7 min.

The design of the trial and the specificities of each arm are described below and in online supplemental file 1.

Supplemental material

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