Background:Postoperative cognitive dysfunction (POCD) is a serious and frequent complication after surgery, especially in elderly patients. Ketamine is an N-methyl D-aspartic acid receptor antagonist with demonstrated neuroprotective effects. An intravenous bolus of a sub-anesthetic dose (0.5 mg/kg) of ketamine can reduce postoperative delirium (POD) and POCD after cardiac surgery. But, the influence of ketamine on early POCD after non-cardiac surgery is unclear.Objectives:The current study aimed to evaluate the influence of ketamine on early postoperative cognitive function after orthopedic surgery in elderly patients.Patients and Methods:Fifty six elderly patients (> 60-years-old), scheduled for elective orthopedic surgery during general anesthesia (duration of anesthesia > two hours) were enrolled. Patients received intravenous bolus, a total of 3 mL mixed with 0.9% normal saline and 0.5 mg/kg ketamine (K group) or 3 mL of 0.9% normal saline (N group). Three neurocognitive function tests (mini-mental status examination, trail-making test, digit substitution test), and c-reactive protein (CRP) concentration were determined before surgery and on postoperative day one (POD 1) and postoperative day six (POD 6).Results:The two groups had similar demographic characteristics except for the gender. Surgical and anesthetic data were not significantly different. A statistically significant difference was observed in comparison of trail-making test score. Trail-making test score increased more in the N group (52.5 points) than the K group (13 points) at POD 1 (P = 0.047) compared with baseline scores. There were no significant differences in the mini-mental status examination, digit substitution test and CRP concentration at POD 1 and POD 6 between the two groups. POCD (the two Z-scores in more than two tests or the combined Z-score was 1.96 or more) was present in one patient (4%) in the K group at POD 6 (P = 0.98).Conclusions:The incidence of POCD was not significantly influenced by a bolus dose of ketamine (0.5 mg/kg) after orthopedic surgery in elderly patients. There were no negative effects of ketamine on early POCD.

ObjectiveA prospective, double-blind, randomized controlled trial to compare the effect of preoperative midazolam or ketamine on the incidence of emergence agitation (EA) following sevoflurane anaesthesia in children.MethodsPaediatric patients (2–6 years old) undergoing ophthalmic surgery were allocated to receive premedication with either 0.1 mg/kg midazolam or 1 mg/kg ketamine. Incidence of EA and postoperative pain scores were recorded at 10-min intervals in the postanaesthetic care unit (PACU). The use of EA rescue medications (fentanyl or midazolam) was recorded.ResultsThe incidence of EA was significantly lower in the ketamine group (n = 33) than the midazolam group (n = 34) at 10 and 20 min after transfer to PACU. There was no significant difference in overall incidence of EA. The frequency of midazolam use as rescue medication was significantly lower in the katamine group than in the midazolam group.ConclusionPremedication with ketamine is more effective than midazolam in preventing EA during the early emergence period after sevoflurane anaesthesia in children.

The PLEM100 (Inbody Co., Ltd., Seoul, Korea) is a device for measuring phase lag entropy (PLE), a recently developed index for the quantification of consciousness during sedation and general anesthesia. In the present study, we assessed changes in PLE along with the level of consciousness during the induction of general anesthesia using propofol. PLE was compared with the bispectral index (BIS), which is currently the most commonly used index of consciousness. After obtaining Institutional Review Board approval and written informed consent, we enrolled 15 patients (8 men, 7 women; mean age: 37 ± 9 years; mean height: 168 ± 8 cm; mean weight; 68 ± 11 kg) undergoing nasal bone reduction. PLE and BIS sensors were attached simultaneously, and general anesthesia was induced via target-controlled infusion (TCI) of propofol. PLE and BIS scores were recorded when the calculated effect site concentration shown on the TCI pump was equal to the target concentrations of 1.5, 2.0, 2.5, 2.8, 3.0, 3.2, 3.4, and 3.5 μg/mL (and at each 0.1 μg/mL increase, thereafter). Observer's Assessment of Alertness/Sedation (OAA/S) scores were also recorded until unconsciousness was achieved. Throughout the anesthesia period, all pairs of PLE and BIS data were collected using data acquisition software. The partial correlation coefficients between OAA/S scores and PLE, and between OAA/S scores and BIS were 0.778 ( P < .001) and 0.846 ( P < .001), respectively. Throughout the period of anesthesia, PLE and BIS exhibited a significant positive correlation. The partial correlation coefficient prior to the loss of consciousness was 0.838 ( P < .001), and 0.669 ( P < .001) following the loss of consciousness. Intra-class correlation between the 2 indices was 0.889 ( P < .001) and 0.791 ( P < .001) prior and following the loss of consciousness, respectively. PLE exhibited a strong and predictable correlation with both BIS and OAA/S scores. These results suggest that PLE is reliable for assessing the level of consciousness during sedation and general anesthesia.

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