The effect of low-dose intravenous ketamine on continuous intercostal analgesia following thoracotomy

Ketamine, a noncompetitive N-methyl-d-aspartate antagonist, provides analgesia and prevents chronic pain following thoracotomy. The study was aimed to assess the effect of intravenous low-dose ketamine on continuous intercostal nerve block analgesia following thoracotomy. The study was a prospective, randomized, double-blinded, and placebo-controlled clinical study, performed in a single university hospital. Sixty patients, undergoing elective lobectomy through an open posterolateral thoracotomy, were included. For postoperative pain, all patients received a continuous intercostal nerve block with bupivacaine plus intravenous paracetamol and ketoprofen. In addition, patients were randomized to have intravenous ketamine (0.1 mg/kg as a preincisional bolus followed by a continuous infusion of 0.05 mg/kg/h) in group 1 or intravenous placebo in group 2. Patients reporting a visual analog scale pain score at rest ≥40 mm received intravenous morphine sulfate as rescue analgesia. The following parameters were assessed every 6 hours for 3 postoperative days: Visual analog scale pain scores at rest and during coughing, requirement of rescue analgesia with morphine, Ramsay sedation scores and psychomimetic adverse effects. Both the groups were statistically comparable regarding visual analog scale pain scores at rest (P=0.75) and during coughing (P=0.70), number of morphine deliveries (P=0.17), cumulative dose of rescue morphine (P=0.2), sedation scores (P=0.4), and psychomimetic adverse effects (P=0.09). Intravenous low-dose ketamine, when combined with continuous intercostal nerve block, did not decrease acute pain scores and supplemental morphine consumption following thoracotomy.