Table 1 Drugs used in the anesthesia regimens of opioid-inclusive (OIA) and opioid-free (OFA) groups

Premedication: Midazolam (2 mg IV)

Premedication: Midazolam (2 mg IV) + Clonidine (1–2 mcg/kg IV)

Induction: Propofol (2 mg/kg IV) + Rocuronium Bromide (0.6 mg/kg IV) + Remifentanil (TCI with an effector site concentration (Cet) of 3–4 ng/ml). Orotracheal intubation.

Induction: Propofol (2 mg/kg IV) + Rocuronium Bromide (0.6 mg/kg IV) + MgSO₄ (1 g IV) + Ketamine (0.2–0.4 mg/kg/h IV). Orotracheal intubation.

Maintenance: Desflurane or Propofol TCI (Schnider protocol [39] with a Cet of 4–5 mcg/ml) + Remifentanil TCI (Cet of 3–4 ng/ml).

Maintenance: Desflurane or Propofol TCI (Schnider [39] protocol with a Cet of 4–5 mcg/ml) + Ketamine 0.2–0.4 mg/kg/h + MgSO₄ 8–10 mg/kg/h.