title: Morphine with adjuvant ketamine versus higher dose of morphine alone for acute pain: a meta-analysis.
abstract: OBJECTIVE
  Ketamine is currently the N-methyl-D-aspartate receptor channel blocker in clinical use. Morphine in pain management is usually limited by adverse effect such as nausea and vomiting. Adjuvant treatment with ketamine may be value in giving better analgesia with fewer adverse effects. The purpose of this meta-analysis was to evaluate the differences when patients received morphine with adjuvant ketamine (MK) compared with higher dose of morphine (MO) for acute pain.
  
  
  METHODS
  The PubMed, EMBASE and the Cochrane Library databases were searched (Last search performed on July 1, 2014) by two reviewers independently. Data were extracted independently by the same two individuals who searched the studies.
  
  
  RESULTS
  A total of 7 trials involving 492 patients were included in the current analysis. We found pain scores were lower in the MK group compared to the MO group [MD 2.19, 95% CI (1.24, 3.13) P<0.00001]. And more patients in the MO required diclofenac [OR 1.97, 95% CI (1.06, 3.67) P=0.03]. Furthermore, morphine plus ketamine can reduced post-operative nausea and vomiting (PONV) [OR 3.71, 95% CI (2.37, 5.80) P<0.00001]. Importantly, the wakefulness scores for the MK group were consistently and significantly better than those for the MO group [MD -1.53, 95% CI (-2.67, -0.40) P=0.008].
  
  
  CONCLUSIONS
  The use of ketamine plus 1/4~2/3 the dose of morphine is better than higher dose of morphine alone in reducing pain scores, and rescuing analgesic requirement. It also improved PONV and wakefulness.
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Xibing
authors.initials: X
authors.lastname: Ding
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Shuqing
authors.initials: S
authors.lastname: Jin
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Xiaoyin
authors.initials: X
authors.lastname: Niu
authors.affiliation: Department of Anesthesiology, Shanghai Huashan Hospital, Fudan University School of Medicine Shanghai, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ren
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Tong
authors.affiliation: Department of Anesthesiology, East Hospital, Tongji University School of Medicine Shanghai, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Li
keywords: Morphine; acute pain; ketamine; meta-analysis