Background and aims: Thoracotomy is associated with severe pain. Postoperative pain is often uncontrollable despite the administration of large amounts of IV morphine. It may cause respiratory and hemodynamic depression. 
This study evaluates the efficacy of ketamine1 as adjuvant in patients undergoing lobectomy by open approach, through the evaluation of opioid-sparing effect and functional recovery. 
Methods: This single-blind, randomized, clinical trial was conducted from October 2017 to September 2018.
Inclusion criteria:
Open surgery lobectomy;
Patients aged ≥ 18 years.
Exclusion criteria:
Psychological disturbances;
Elevated intracranial or intraocular pressure;
Hepatic dysfunction;
Cardiovascular disease or uncontrolled hypertension.
In PACU, patients received IV morphine infusion at 0.015 mg/kg/h plus saline solution (MO) or IV morphine infusion at 0.005 mg/kg/h plus IV ketamine infusion at 0.5-1 mg/kg/h (MK) for 48 hours. If NRS>3, IV ketorolac was available.
NRS, wakefulness degree, rescue analgesia requirement, and adverse reactions were registered every 2 hours.
Results: 28 patients were enrolled. NRS scores improved more in MK group than in MO group (p< 0.05), with more stable hemodynamic and respiratory conditions. No significant side effects were recorded.
Conclusions: Ketamine shows a consistent opioid-sparing effect obtaining quick functional recovery in absence of severe side effects.
References: 
Schwenk ES, Viscusi ER, Buvanendran A, et al. Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management from the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists. Reg Anesth Pain Med. 2018;43(5):456-466.

LOW-DOSE INTRAVENOUS KETAMINE INFUSION FOR POSTTHORACIC SURGERY PAIN: OPIOID-SPARING EFFECT AND IMPROVED FUNCTIONAL RECOVERY. A RANDOMIZED CLINICAL TRIAL