Does Intraoperative Ketamine Attenuate Inflammatory Reactivity Following Surgery? A Systematic Review and Meta-Analysis

The effect of a perioperative ketamine infusion on the incidence of chronic postsurgical pain-a pilot study

Chronic postsurgical pain (CPSP) is a common and debilitating complication of major surgery. We undertook a pilot study at three hospitals to assess the feasibility of a proposed large multicentre placebo-controlled randomised trial of intravenous perioperative ketamine to reduce the incidence of CPSP. Ketamine, 0.5 mg/kg pre-incision, 0.25 mg/kg/hour intraoperatively and 0.1 mg/kg/hour for 24 hours, or placebo, was administered to 80 patients, recruited over a 15-month period, undergoing abdominal or thoracic surgery under general anaesthesia. The primary endpoint was CPSP in the area of the surgery reported at six-month telephone follow-up using a structured questionnaire. Fourteen patients (17.5%) reported CPSP (relative risk [95% confidence interval] if received ketamine 1.18 [0.70 to 1.98], P=0.56). Four patients in the treatment group and three in the control group reported ongoing analgesic use to treat CPSP and two patients in each group reported their worst pain in the previous 24 hours at ≥3/10 at six months. There were no significant differences in adverse event rates, quality of recovery scores, or cumulative morphine equivalents consumption in the first 72 hours. Numeric Rating Scale pain scores (median [interquartile range, IQR]) for average pain in the previous 24 hours among those patients reporting CPSP were 17.5 [0 to 40] /100 with no difference between treatment groups. A large (n=4,000 to 5,000) adequately powered multicentre trial is feasible using this population and methodology.

Comparing Postoperative Complications and Inflammatory Markers Using Total Intravenous Anesthesia Versus Volatile Gas Anesthesia for Pancreatic Cancer Surgery

Objectives

The objective of this study is to evaluate postoperative complications and inflammatory profiles when using a total intravenous anesthesia (TIVA) or volatile gas-opioid (VO) based anesthesia in patients undergoing pancreatic cancer surgery.

Methods

Design, retrospective propensity score matched cohort; Setting, major academic cancer hospital; Patients, all patients who had pancreatic surgery between November 2011 and August 2014 were retrospectively reviewed. Propensity score matched patient pairs were formed. A total of 134 patients were included for analysis with 67 matched pairs; Interventions, Patients were categorized according to type of anesthetic used (TIVA or VO). Patients in the TIVA group received preoperative celecoxib, tramadol, and pregabalin in addition to intraoperative TIVA with propofol, lidocaine, ketamine, and dexmedetomidine. The VO-group received a volatile-opioid based anesthetic; Measurements, demographic, perioperative clinical data, platelet lymphocyte ratios, and neutrophil lymphocyte ratios were collected. Complications were graded and collected prospectively and later reviewed retrospectively.

Results

Patients receiving TIVA were more likely to have no complication or a lower grade complication than the VO-group (P = 0.014). There were no differences in LOS or postoperative inflammatory profiles noted between the TIVA and VO groups.

Conclusions

In this retrospective matched analysis of patients undergoing pancreatic cancer surgery, TIVA was associated with lower grade postoperative complications. Length of hospital stay (LOS) and postoperative inflammatory profiles were not significantly different.

Intraoperative ketamine for prevention of postoperative delirium or pain after major surgery in older adults: an international, multicentre, double-blind, randomised clinical trial

BACKGROUND

Delirium is a common and serious postoperative complication. Subanaesthetic ketamine is often administered intraoperatively for postoperative analgesia, and some evidence suggests that ketamine prevents delirium. The primary purpose of this trial was to assess the effectiveness of ketamine for prevention of postoperative delirium in older adults.

METHODS

The Prevention of Delirium and Complications Associated with Surgical Treatments [PODCAST] study is a multicentre, international randomised trial that enrolled adults older than 60 years undergoing major cardiac and non-cardiac surgery under general anaesthesia. Using a computer-generated randomisation sequence we randomly assigned patients to one of three groups in blocks of 15 to receive placebo (normal saline), low-dose ketamine (0·5 mg/kg), or high dose ketamine (1·0 mg/kg) after induction of anaesthesia, before surgical incision. Participants, clinicians, and investigators were blinded to group assignment. Delirium was assessed twice daily in the first 3 postoperative days using the Confusion Assessment Method. We did analyses by intention-to-treat and assessed adverse events. This trial is registered with clinicaltrials.gov, number NCT01690988.

FINDINGS

Between Feb 6, 2014, and June 26, 2016, 1360 patients were assessed, and 672 were randomly assigned, with 222 in the placebo group, 227 in the 0·5 mg/kg ketamine group, and 223 in the 1·0 mg/kg ketamine group. There was no difference in delirium incidence between patients in the combined ketamine groups and the placebo group (19·45% vs 19·82%, respectively; absolute difference 0·36%, 95% CI -6·07 to 7·38, p=0·92). There were more postoperative hallucinations (p=0·01) and nightmares (p=0·03) with increasing ketamine doses compared with placebo. Adverse events (cardiovascular, renal, infectious, gastrointestinal, and bleeding), whether viewed individually (p value for each >0·40) or collectively (36·9% in placebo, 39·6% in 0·5 mg/kg ketamine, and 40·8% in 1·0 mg/kg ketamine groups, p=0·69), did not differ significantly across groups.

INTERPRETATION

A single subanaesthetic dose of ketamine did not decrease delirium in older adults after major surgery, and might cause harm by inducing negative experiences.

FUNDING

National Institutes of Health and Cancer Center Support.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of a review first published in 2003 and updated in 2012.Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of refractory cancer pain, when opioids alone or in combination with appropriate adjuvant analgesics prove to be ineffective. Ketamine is known to have psychomimetic (including hallucinogenic), urological, and hepatic adverse effects.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids for refractory cancer pain in adults.

SEARCH METHODS

For this update, we searched MEDLINE (OVID) to December 2016. We searched CENTRAL (CRSO), Embase (OVID) and two clinical trial registries to January 2017.

SELECTION CRITERIA

The intervention considered by this review was the addition of ketamine, given by any route of administration, in any dose, to pre-existing opioid treatment given by any route and in any dose, compared with placebo or active control. We included studies with a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results and performed 'Risk of bias' assessments. We aimed to extract data on patient-reported pain intensity, total opioid consumption over the study period; use of rescue medication; adverse events; measures of patient satisfaction/preference; function; and distress. We also assessed participant withdrawal (dropout) from trial. We assessed the quality of the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation).

MAIN RESULTS

One new study (185 participants) was identified by the updated search and included in the review. We included a total of three studies in this update.Two small studies, both with cross-over design, with 20 and 10 participants respectively, were eligible for inclusion in the original review. One study with 20 participants examined the addition of intrathecal ketamine to intrathecal morphine, compared with intrathecal morphine alone. The second study with 10 participants examined the addition of intravenous ketamine bolus in two different doses to ongoing morphine therapy, compared with placebo. Both of these studies reported reduction in pain intensity and reduction in morphine requirements when ketamine was added to opioid for refractory cancer pain. The new study identified by the updated search had a parallel group design and 185 participants. This placebo-controlled study examined rapid titration of subcutaneous ketamine to high dose (500 mg) in participants who were using different opioids. There were no differences between groups for patient-reported pain intensity.Pooling of the data from the three included trials was not appropriate because of clinical heterogeneity.The study examining intrathecal drug administration reported no adverse events related to ketamine. In the study using intravenous bolus administration, ketamine caused hallucinations in four of 10 participants. In the rapid dose escalation/high-dose subcutaneous ketamine study, there was almost twice the incidence of adverse events in the ketamine group, compared to the placebo group, with the most common adverse events being needle site irritation and cognitive disturbance. Two serious adverse events (bradyarrhythmia and cardiac arrest) thought to be related to ketamine were also reported in this trial.For all three studies there was an unclear risk of bias overall. Using GRADE, we judged the quality of the evidence to be very low due to study limitations and imprecision due to the small number of participants in all comparisons.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of refractory cancer pain. The evidence was of very low quality, meaning that it does not provide a reliable indication of the likely effect, and the likelihood that the effect will be substantially different is high. Rapid dose escalation of ketamine to high dose (500 mg) does not appear to have clinical benefit and may be associated with serious adverse events. More randomised controlled trials (RCTs) examining specific low-dose ketamine clinical regimens in current use are needed.

Effect of low-dose ketamine on post-operative serum IL-6 production among elective surgical patients: a randomized clinical trial

BACKGROUND

Surgery and Anesthesia cause an excessive pro-inflammatory response. Mulago Hospital is faced with staff shortage making post-operative pain management difficult.Interleukin-6 (IL-6) drives inflammatory pain, endothelial cell dysfunction and fibrogenesis. Ketamine is cheap and, readily available. We hypothesized that its attenuation of serum IL-6 was a surrogate for clinical benefit.

MATERIALS AND METHODS

Institutional Review Board's approval was sought and RCT was registered at clinical trials.gov (identifier number: NCT01339065). Consenting patients were randomized to receive pre-incision intravenous ketamine - 0.5mg/kg or 0.9% saline placebo in weighted dosing. Blood samples were collected and laboratory analyzed at baseline, post-operatively in PACU, 24 and 48 hours respectively.

RESULTS

We recruited 39 patients of whom 18 were randomized to the ketamine arm and 21 in the placebo arm with follow up at 24 and 48 hours. Serum IL-6 and IL-1β levels were analyzed using ELIZA assay of pre-coated micro wells. Ketamine suppressed serum IL-6 at PACU with reduced increase at 24 hours. There was no reaction in 98% of IL-1β assayed.

CONCLUSION

Low-dose ketamine attenuated early serum IL-6 levels due to surgical response with reduced 24 hour increase, but the difference was not statistically significant and we recommend more studies.

Pharmacogenetics of Ketamine-Induced Emergence Phenomena: A Pilot Study

BACKGROUND

Up to 55% of patients who are administered ketamine experience an emergence phenomena (EP) that closely mimics schizophrenia and increases their risk of injury; however, to date, no studies have investigated genetic association of ketamine-induced EP in healthy patients.

OBJECTIVES

The aim of the study was to investigate the feasibility and sample sizes required to explore the relationship between CYP2B6*6 and GRIN2B single-nucleotide polymorphisms and ketamine-induced EP.

METHODS

This cross-sectional, pharmacogenetic candidate, gene pilot study recruited 75 patients having minor elective outpatient surgeries. EP was measured with the Clinician Administered Dissociative State Scale. Genetic association of CYP2B6*6 and GRIN2B (rs1019385 and rs1806191) single-nucleotide polymorphisms and ketamine-induced EP occurrence and severity were tested using logistic and linear regression.

RESULTS

Forty-seven patients (63%) received ketamine and were genotyped, and 40% of them experienced EP. Occurrence and severity of EP were not associated with CYP2B6*6 or GRIN2B (p > .10). Exploratory analysis of nongenotype models containing age, ketamine dose, duration of anesthesia, and time from ketamine administration to assessment for EP significantly predicted EP occurrence (p = .001) and severity (p = .007). This pilot study demonstrates feasibility for implementing a pharmacogenetic study in a clinical setting, and we estimate that between 380 and 570 cases will be needed to adequately power future genetic association studies.

DISCUSSION

Younger age, higher dose, and longer duration of anesthesia significantly predicted EP occurrence and severity among our pilot sample. Although the small sample size limited our ability to demonstrate significant genotype differences, we generated effect sizes, sample size estimates, and nongenetic covariates information in order to support future pharmacogenetic study design for evaluating this adverse event.

Targeting glutamate signalling in depression: progress and prospects

Major depressive disorder (MDD) is severely disabling, and current treatments have limited efficacy. The glutamate N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine was recently repurposed as a rapidly acting antidepressant, catalysing the vigorous investigation of glutamate-signalling modulators as novel therapeutic agents for depressive disorders. In this Review, we discuss the progress made in the development of such modulators for the treatment of depression, and examine recent preclinical and translational studies that have investigated the mechanisms of action of glutamate-targeting antidepressants. Fundamental questions remain regarding the future prospects of this line of drug development, including questions concerning safety and tolerability, efficacy, dose-response relationships and therapeutic mechanisms.

Successful Use of Ketamine for Central Neurogenic Hyperventilation: A Case Report

This report describes the use of ketamine in a patient with central neurogenic hyperventilation following intracerebral hemorrhage. A 41-year-old man was admitted with right thalamic intracerebral hemorrhage with intraventricular extension requiring emergent external ventricular drain placement. After aggressive management of his neurologic status and other associated complications, the patient subacutely developed an altered respiratory pattern characterized by shallow, rapid breaths. After the use of multiple sedative agents to control respiratory drive had failed, a single 2 mg/kg bolus dose of intravenous ketamine was administered. In the 6 hours prior to ketamine dosing, respiratory rate ranged from 24 to 40 breaths per minute. Within minutes of ketamine administration, respiratory patterns improved and primarily ranged from 16 to 20. Twenty-four hours after ketamine administration, the patient was successfully extubated following 12 days of mechanical ventilation. Further research is needed to determine the widespread applicability of this strategy.

Altered peripheral immune profiles in treatment-resistant depression: response to ketamine and prediction of treatment outcome

A subset of patients with depression have elevated levels of inflammatory cytokines, and some studies demonstrate interaction between inflammatory factors and treatment outcome. However, most studies focus on only a narrow subset of factors in a patient sample. In the current study, we analyzed broad immune profiles in blood from patients with treatment-resistant depression (TRD) at baseline and following treatment with the glutamate modulator ketamine. Serum was analyzed from 26 healthy control and 33 actively depressed TRD patients free of antidepressant medication, and matched for age, sex and body mass index. All subjects provided baseline blood samples, and TRD subjects had additional blood draw at 4 and 24 h following intravenous infusion of ketamine (0.5 mg kg^-1). Samples underwent multiplex analysis of 41 cytokines, chemokines and growth factors using quantitative immunoassay technology. Our a priori hypothesis was that TRD patients would show elevations in canonical pro-inflammatory cytokines; analyses demonstrated significant elevation of the pro-inflammatory cytokine interleukin-6. Further exploratory analyses revealed significant regulation of four additional soluble factors in patients with TRD. Several cytokines showed transient changes in level after ketamine, but none correlated with treatment response. Low pretreatment levels of fibroblast growth factor 2 were associated with ketamine treatment response. In sum, we found that patients with TRD demonstrate a unique pattern of increased inflammatory mediators, chemokines and colony-stimulating factors, providing support for the immune hypothesis of TRD. These patterns suggest novel treatment targets for the subset of patients with TRD who evidence dysregulated immune functioning.

Ketamine-A Narrative Review of Its Uses in Medicine

One of the most fascinating drugs in the anesthesiologist's armament is ketamine, an N-methyl-D-aspartate receptor antagonist with a myriad of uses. The drug is a dissociative anesthetic and has been used more often as an analgesic in numerous hospital units, outpatient pain clinics, and in the prehospital realm. It has been used to treat postoperative pain, chronic pain, complex regional pain syndrome, phantom limb pain, and other neuropathic conditions requiring analgesia. Research has also demonstrated its efficacy as an adjunct in psychotherapy, as a treatment for both depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and neurologic conditions. Ketamine is not without its adverse effects, some of which can be mitigated with certain efforts. Such effects make it necessary for the clinician to use the drug only in situations where it will provide the greatest benefit with the fewest adverse effects. To the best of our knowledge, none of the reviews regarding ketamine have taken a comprehensive look at the drug's uses in all territories of medicine. This review will serve to touch on its chemical data, pharmacokinetics and pharmacodynamics, medical uses, and adverse effects while focusing specifically on the drugs usage in anesthesia and analgesia.

Effect of ketamine on pro- and anti-inflammatory cytokine response in paediatric cardiac surgery: A prospective randomised controlled study

Background and Aims:

Paediatric cardiac surgery with cardiopulmonary bypass (CPB) is associated with a marked inflammatory response and triggers release of inflammatory cytokines. The aim of this study was to study the effect of ketamine on the inflammatory response during correction of congenital cyanotic heart diseases.

Methods:

Sixty-six patients with congenital cyanotic heart diseases scheduled for cardiac surgery were randomised into three groups. Group A patients did not receive ketamine (control group), Group B patients received 2 mg/kg ketamine intravenous (IV) and Group C patients received ketamine 2 mg/kg IV and an IV infusion of ketamine (50 μg/kg/min). Interleukin (IL) levels for IL-6, IL-8, IL-10, C-reactive protein (CRP) and tumour necrosis factor-α (TNF-α) levels were examined in the three groups at four timings: pre-operative (baseline), intraoperative (after weaning off the CPB) and post-operative (6 and 24 h after weaning off CPB). Paired sample t-test and ANOVA test were used for statistical analysis and P < 0.05 was considered statistically significant.

Results:

Within each group, the intra- and post-operative serum levels of IL-6, IL-8, IL-10 and CRP were significantly elevated from the baseline, however, TNF-α was not significantly elevated. There were no statistically significant differences in the IL, CRP or TNF-α levels between the three groups.

Conclusion:

Paediatric cardiac surgery for congenital cyanotic heart disease is a triggering factor for the inflammatory response, yet we could not detect any beneficial effect of ketamine on that response whether given either as an IV induction dose or continued as an IV infusion.

A comparison between intravenous lidocaine and ketamine on acute and chronic pain after open nephrectomy: A prospective, double-blind, randomized, placebo-controlled study

BACKGROUND

Recently, there has been increasing interest in the use of analgesic adjuncts such as intravenous (IV) ketamine and lidocaine.

OBJECTIVES

To compare the effects of perioperative IV lidocaine and ketamine on morphine requirements, pain scores, quality of recovery, and chronic pain after open nephrectomy.

STUDY DESIGN

A prospective, randomized, placebo-controlled, double-blind trial.

SETTINGS

The study was conducted in Charles Nicolle University Hospital of Tunis.

METHODS

Sixty patients were randomly allocated to receive IV lidocaine: bolus of 1.5 mg/kg at the induction of anesthesia followed by infusion of 1 mg/kg/h intraoperatively and for 24 h postoperatively or ketamine: bolus of 0.15 mg/kg followed by infusion of 0.1 mg/kg/h intraoperatively and for 24 h postoperatively or an equal volume of saline (control group [CG]).

MEASUREMENTS

Morphine consumption, visual analog scale pain scores, time to the first passage of flatus and feces, postoperative nausea and vomiting (PONV), 6-min walk distance (6MWD) at discharge, and the incidence of chronic neuropathic pain using the "Neuropathic Pain Questionnaire" at 3 months.

RESULTS

Ketamine and lidocaine reduced significantly morphine consumption (by about 33% and 42%, respectively) and pain scores compared with the CG (P < 0.001). Lidocaine and ketamine also significantly improved bowel function in comparison to the CG (P < 0.001). Ketamine failed to reduce the incidence of PONV. The 6 MWD increased significantly from a mean ± standard deviation of 27 ± 16.2 m in the CG to 82.3 ± 28 m in the lidocaine group (P < 0.001). Lidocaine, but not ketamine, reduced significantly the development of neuropathic pain at 3 months (P < 0.05).

CONCLUSION

Ketamine and lidocaine are safe and effective adjuvants to decrease opioid consumption and control early pain. We also suggest that lidocaine infusion serves as an interesting alternative to improve the functional walking capacity and prevent chronic neuropathic pain at 3 months after open nephrectomy.

Change in cytokine levels is not associated with rapid antidepressant response to ketamine in treatment-resistant depression

Several pro-inflammatory cytokines have been implicated in depression and in antidepressant response. This exploratory analysis assessed: 1) the extent to which baseline cytokine levels predicted positive antidepressant response to ketamine; 2) whether ketamine responders experienced acute changes in cytokine levels not observed in non-responders; and 3) whether ketamine lowered levels of pro-inflammatory cytokines, analogous to the impact of other antidepressants. Data from double-blind, placebo-controlled studies of patients with major depressive disorder (MDD) or bipolar disorder (BD) who received a single infusion of sub-anesthetic dose ketamine were used (N = 80). Plasma levels of the eight cytokines were measured at baseline and at 230 min, 1 day, and 3 days post-ketamine. A significant positive correlation was observed between sTNFR1 and severity of depression at baseline. Cytokine changes did not correlate with changes in mood nor predict mood changes associated with ketamine administration. Ketamine significantly increased IL-6 levels and significantly decreased sTNFR1 levels. IL-6 and TNF-α levels were also significantly higher-and sTNFR1 levels were significantly lower-in BD compared to MDD subjects. The functional significance of this difference is unknown. Changes in cytokine levels post-ketamine were not related to antidepressant response, suggesting they are not a primary mechanism involved in ketamine's acute antidepressant effects. Taken together, the results suggest that further study of cytokine levels is warranted to assess their potential role as a surrogate outcome in the rapid antidepressant response paradigm.

Efficacy of Ketamine as an Adjunct to Local Anesthesia in the Surgical Removal of Impacted Mandibular Third Molars - A Split Mouth Prospective Controlled Clinical Study

INTRODUCTION

The removal of impacted teeth is one of the most common procedures performed by oral and maxillofacial surgeons. Reduction of discomfort post-operatively and efficient local anesthesia are imperative for success in surgical practice. At sub-anesthetic doses, ketamine has a noticeable analgesic action, which can be used to supplement local anesthesia with minimal side effects.

AIM

To assess the efficacy of low-dose ketamine as an adjunct to local anesthesia in the management of pain, swelling and trismus after surgical removal of impacted mandibular third molars.

MATERIALS AND METHODS

Twenty five patients with bilaterally symmetrical impacted mandibular third molars requiring surgical removal under local anesthesia were selected for the controlled clinical study. The third molar sites of all patients enrolled in the trial were randomly assigned into 2 groups: Local Anesthesia (Lignocaine) Alone [LAA] and Local Anesthesia plus ketamine [LAK]. 5ml of local anesthetic (Lignocaine Hydrochloride 2% with epinephrine 1:100,000) was injected in the 'LAA' group while the 'LAK' group received 5ml of local anesthetic plus 0.2mg/kg ketamine. Patients were blinded to the solution used and the operator recorded the group (LAA or LAK) and the respective site (Right or Left) for analysis. Bilaterally symmetrical impacted mandibular molars were removed at an interval of 15 days.

RESULTS

Facial swelling on post-operative days was significantly lower in the LAK group than in the LAA group (p<0.05). The pain scores on the VAS were significantly higher in the LAA group than in the LAK group (p<0.05).

CONCLUSION

The role of ketamine in low doses as an analgesic and anti-inflammatory is evident in our study. The combination of a local anesthetic and sub-anesthetic doses of ketamine injected for surgical removal of impacted third molars provides good local anesthesia while alleviating post-operative sequelae for the patient by providing a degree of post-operative analgesia with less swelling.

Effectiveness of low-dose intravenous ketamine to attenuate stress response in patients undergoing emergency cesarean section with spinal anesthesia

PURPOSE

Cesarean section is a surgical procedure. Surgical procedures will induce stress responses, which may have negative impact on postoperative recovery. Ketamine plays a role in the homeostatic regulation of inflammatory response in order to attenuate stress response. We tried to determine the effectiveness of low-dose intravenous ketamine to attenuate stress response in patients undergoing emergency cesarean section with spinal anesthesia.

PATIENTS AND METHODS

Thirty-six pregnant women undergoing emergency cesarean section with spinal anesthesia were randomly divided into two groups (n=18). Ketamine 0.3 mg/kg (KET group) or NaCl 0.9% (NS group) was administered intravenously before the administration of spinal anesthesia. C-reactive protein (CRP) and neutrophil levels were measured preoperatively and postoperatively.

RESULTS

Elevation of CRP stress response was lower in the KET group and significantly different (P≤0.05) from that in the NS group. Neutrophil level was elevated in both the groups and hence not significantly different from each other (P>0.05). Postoperative visual analog scale pain score was not significantly different between the two groups (P>0.05), but there was a statistically significant (P≤0.05) positive and weak correlation between visual analog scale and CRP level postoperatively.

CONCLUSION

Low-dose intravenous ketamine effectively attenuates the CRP stress response in patients undergoing emergency cesarean section with spinal anesthesia.

Ketamine use in current clinical practice

After nearly half a century on the market, ketamine still occupies a unique corner in the medical armamentarium of anesthesiologists or clinicians treating pain. Over the last two decades, much research has been conducted highlighting the drug's mechanisms of action, specifically those of its enantiomers. Nowadays, ketamine is also being utilized for pediatric pain control in emergency department, with its anti-hyperalgesic and anti-inflammatory effects being revealed in acute and chronic pain management. Recently, new insights have been gained on ketamine's potential anti-depressive and antisuicidal effects. This article provides an overview of the drug's pharmacokinetics and pharmacodynamics while also discussing the potential benefits and risks of ketamine administration in various clinical settings.

High Spinal Anesthesia Enhances Anti-Inflammatory Responses in Patients Undergoing Coronary Artery Bypass Graft Surgery and Aortic Valve Replacement: Randomized Pilot Study

Background

Cardiac surgery induces many physiologic changes including major inflammatory and sympathetic nervous system responses. Here, we conducted a single-centre pilot study to generate hypotheses on the potential immune impact of adding high spinal anaesthesia to general anaesthesia during cardiac surgery in adults. We hypothesized that this strategy, previously shown to blunt the sympathetic response and improve pain management, could reduce the undesirable systemic inflammatory responses caused by cardiac surgery.

Methods

This prospective randomized unblinded pilot study was conducted on 14 patients undergoing cardiac surgery for coronary artery bypass grafting and/or aortic valve replacement secondary to severe aortic stenosis. The primary outcome measures examined longitudinally were serum pro-inflammatory (IL-6, IL-1b, CCL2), anti-inflammatory (IL-10, TNF-RII, IL-1Ra), acute phase protein (CRP, PTX3) and cardiovascular risk (sST2) biomarkers.

Results

The kinetics of pro- and anti-inflammatory biomarker was determined following surgery. All pro-inflammatory and acute phase reactant biomarker responses induced by surgical stress were indistinguishable in intensity and duration between control groups and those who also received high spinal anaesthesia. Conversely, IL-10 levels were markedly elevated in both intensity and duration in the group receiving high spinal anesthesia (p = 0.005).

Conclusions

This hypothesis generating pilot study suggests that high spinal anesthesia can alter the net inflammatory response that results from cardiac surgery. In appropriately selected populations, this may add incremental benefit by dampening the net systemic inflammatory response during the week following surgery. Larger population studies, powered to assess immune, physiologic and clinical outcomes in both acute and longer term settings, will be required to better assess potential benefits of incorporating high spinal anesthesia.

Trial Registration

ClinicalTrials.gov NCT00348920

Ketamine in adult cardiac surgery and the cardiac surgery Intensive Care Unit: an evidence-based clinical review

Ketamine is a unique anesthetic drug that provides analgesia, hypnosis, and amnesia with minimal respiratory and cardiovascular depression. Because of its sympathomimetic properties it would seem to be an excellent choice for patients with depressed ventricular function in cardiac surgery. However, its use has not gained widespread acceptance in adult cardiac surgery patients, perhaps due to its perceived negative psychotropic effects. Despite this limitation, it is receiving renewed interest in the United States as a sedative and analgesic drug for critically ill-patients. In this manuscript, the authors provide an evidence-based clinical review of ketamine use in cardiac surgery patients for intensive care physicians, cardio-thoracic anesthesiologists, and cardio-thoracic surgeons. All MEDLINE indexed clinical trials performed during the last 20 years in adult cardiac surgery patients were included in the review.

Preventive Treatment with Ketamine Attenuates the Ischaemia-Reperfusion Response in a Chronic Postischaemia Pain Model

Ischemia and inflammation may be pathophysiological mechanisms of complex regional pain syndrome (CRPS). Ketamine has proposed anti-inflammatory effects and has been used for treating CRPS. This study aimed to evaluate anti-inflammatory and analgesic effects of ketamine after ischaemia-reperfusion injury in a chronic postischaemia pain (CPIP) model of CRPS-I. Using this model, ischemia was induced in the hindlimbs of male Sprague-Dawley rats. Ketamine, methylprednisolone, or saline was administered immediately after reperfusion. Physical effects, (oedema, temperature, and mechanical and cold allodynia) in the bilateral hindpaws, were assessed from 48 hours after reperfusion. Fewer (56%) rats in the ketamine group developed CPIP at the 48th hour after reperfusion (nonsignificant). Ketamine treated rats showed a significantly lower temperature in the ischaemic hindpaw compared to saline (P < 0.01) and methylprednisolone (P < 0.05) groups. Mechanical and cold allodynia were significantly lower in the ischaemic side in the ketamine group (P < 0.05). Proinflammatory cytokines TNF-α and IL-2 were significantly lower at the 48th hour after reperfusion in ketamine and methylprednisolone groups, compared to saline (all P < 0.05). In conclusion, immediate administration of ketamine after an ischaemia-reperfusion injury can alleviate pain and inflammation in the CPIP model and has potential to treat postischaemic pain.

Best practice in the administration of analgesia in postoncological surgery

The rationale for using multimodal analgesia after any major surgery is achievement of adequate analgesia while avoiding the unwanted effects of large doses of any analgesic, in particular opioids. There are two reasons why we can hypothesize that multimodal analgesia might have a significant impact on cancer-related outcomes in the context of oncological orthopedic surgery. First, because multimodal analgesia is a key component of enhanced-recovery pathways and can accelerate return to intended oncological therapy. And second, because some of the analgesic used in multimodal analgesia (i.e., COX inhibitors, local analgesics and dexamethasone) can induce apoptosis in cancer cells and/or diminish the inflammatory response during surgery which itself can facilitate tumor growth.

Efficacy of an intrathecal multidrug infusion for pain control in older adults and in end-stage malignancies: A report of three cases

The aim of the present study was to explore the effectiveness of an alternative method to manage pain based on a time-limited intrathecal (IT) infusion of an analgesic medication mixture. Three patients (69, 64 and 94 years of age) with intractable and poorly controlled pain due to bed sores, pelvic metastatic mass, and thoracic vertebra and rib fractures, respectively, were treated. Daily doses of opioids could not be increased due to side effects. An IT catheter (20 G) was placed by percutaneous approach in the lumbar area while advancing toward the thoracic region, and was then tunnelled and fixed subcutaneously. It was connected to an external infusion pump with a mixture of bupivacaine 1 mg⁄mL, naloxone 0.02 ng⁄mL, ketamine 100 µg⁄mL, morphine 0.01 mg⁄mL and clonidine 0.75 µg⁄mL. The starting rate was 1 mL⁄h. The pain was mostly controlled at a rate of <1 mL⁄h. Opioid consumption was reduced dramatically. The catheter was kept in place for one month in the first and third patients, and for six months in the second patient, until his death. Major side effects, such as hypotension, constipation, muscle weakness, sphincter dysfunction, and cognitive or mood deterioration, were not observed with this approach. One patient experienced a urinary tract infection followed by sepsis and meningitis, which was cured by antibiotics. The catheter was removed in this patient. IT infusion with a low-concentration multidrug mixture could be considered as an alternative modality for intractable pain relief in older adults or in malignancies.

Evaluation of the effect of ketamine on remifentanil-induced hyperalgesia: a double-blind, randomized study

STUDY OBJECTIVE

Opioids are associated with hyperalgesia that can reduce their analgesic effect. The aim of this study was to determine whether the addition of ketamine reduces remifentanil-induced hyperalgesia; improves its analgesic effect; and alters interleukin 6 (IL-6), IL-8, and IL-10 levels.

DESIGN

This is a prospective, randomized, double-blind study.

SETTING

The setting is in a operating room and ward in a university hospital.

PATIENTS

There are 56 patients, aged ≥18 years, American Society of Anesthesiologists I or II, who underwent laparoscopic cholecystectomy.

INTERVENTIONS

Anesthesia was induced with remifentanil, 50% oxygen, and isoflurane. Patients randomized to group 1 received remifentanil (0.4 μg/kg per minute) and ketamine (5 μg/kg per minute), and patients randomized to group 2 received remifentanil (0.4 μg/kg per minute) and saline solution. Postoperative analgesia was achieved using morphine via patient-controlled analgesia.

MEASUREMENTS

The measurements were postoperative pain intensity during 24 hours; morphine consumption; time to first morphine supplementation; hyperalgesia (using monofilaments and an algometer) and allodynia (using a soft brush) in the thenar eminence of the nondominant hand and in the periumbilical region 24 hours after surgery; extent of hyperalgesia using a 300-g monofilament near the periumbilical region 24 hours after surgery; and serum levels of IL-6, IL-8, and IL-10.

MAIN RESULTS

Groups were similar for baseline characteristics. There were no differences in pain intensity, time to first request of morphine, and total 24 hours dose of morphine between groups. There was a difference in hyperalgesia using monofilaments 24 hours after the surgery in the thenar eminence of the nondominant hand, with a better profile for the experimental group. However, there were no differences in hyperalgesia using an algometer, in allodynia using a soft brush; in extent of hyperalgesia; or in levels of IL-6, IL-8, and IL-10.

CONCLUSIONS

It was not possible to demonstrate that the addition of ketamine (5 μg/kg per minute) is effective in preventing or reducing remifentanil-induced postoperative hyperalgesia in laparoscopic cholecystectomy.

Immunomodulatory activity of ketamine in human astroglial A172 cells: Possible relevance to its rapid antidepressant activity

To determine if the immunomodulatory effect of ketamine is relevant to its rapid antidepressant activity, cultured human astroglial cells were incubated with ketamine, cytokine mix, or both. At 24h, ketamine dose-dependently (100-500 μM) decreased IL-6 and TNFα production and gene expression and, at clinically relevant concentration (100 μM), augmented IL-β release and gene expression in both unstimulated and cytokine-stimulated cells. In unstimulated cells, ketamine also increased IL-8 production and mRNA expression. The reduction in IL-6 mRNA was significant within 1h in unstimulated cells and at 4h after stimulation. Ketamine suppressed the production of the only established depression-relevant proinflammatory cytokines, IL-6 and TNFα.

Optimal analgesia during major open and laparoscopic abdominal surgery

Optimal analgesia is a key element of enhanced recovery after surgery (ERAS), not only for humanitarian reasons but also because poorly relieved surgical pain contributes to surgical stress and impairs recovery. A multimodal analgesic approach is advised in order to provide adequate analgesia, reduce opioid consumption, reduce side effects and facilitate the achievement of ERAS milestones. For open surgery, a thoracic epidural for 48 to 72 hours, with regular acetaminophen and antiinflammatories is probably the treatment of choice. For laparoscopic surgery, intrathecal or local anesthesia in the wound combined with regular acetaminophen and antiinflammatory drugs is effective.

A comparison of the effects of ketamine and remifentanil on renal functions in coronary artery bypass graft surgery

We have investigated the effects of ketamine-based and remifentanil-based anesthetic protocol on perioperative serum cystatin-C levels, and creatinine and/or cystatin-C-based eGFR equations in terms of acute kidney injury in coronary artery bypass graft (CABG) surgery. Using a simple randomization method (coin tossing), patients were divided into the two groups and not-blinded to the anesthetist. Remifentanil-midazolam-propofol or ketamine-midazolam-propofol-based anesthetic regimen was chosen. Different eGFR formulas using creatinine (MDRD, CKD-EPI, Cockrauft Gault); cystatin-C (eGFR1, eGFR2) or a combination of creatinine and cystatin-C (eGFR 3) were used to calculate estimated glomerular filtration rates (eGFRs). High-sensitive troponin T was used to determine if ketamine use in coronary surgery contributed to myocardial cell damage. Thirty-seven patients were included in the study (remifentanil group = 19, ketamine Group = 18). Urea, creatinine, cystatin-C levels were comparable between the groups in all the measurement times and also postoperative day 2 samples showed statistically higher results compared to baseline (p < 0.001). Effects of ketamine and remifentanil on renal functions were found similar. Creatinine and cystatin-C-based eGFR equations resulted similar in our study. Reversible stage 1 acute kidney injury (AKI) was observed on postoperative day 2 in seven patients from the remifentanil group and six patients from the ketamine group. Hs-troponin T was found to be higher in postoperative day 1 samples; there were no significant difference between the groups. Our results indicated that patients who have normal renal functions undergoing on-pump coronary bypass surgery, effects of ketamine and remifentanil on renal functions in terms of AKI were found to be similar.

The rapid antidepressant effect of ketamine in rats is associated with down-regulation of pro-inflammatory cytokines in the hippocampus

OBJECTIVES

Active inflammatory responses play an important role in the pathogenesis of depression. We hypothesized that the rapid antidepressant effect of ketamine is associated with the down-regulation of pro-inflammatory mediators.

METHODS

Forty-eight rats were equally randomized into six groups (a control and five chronic unpredictable mild stress (CUMS) groups) and given either saline or 10 mg/kg ketamine, respectively. The forced swimming test was performed, and the hippocampus was subsequently harvested for the determination of levels of interleukin (IL)-1β, IL-6, tumour necrosis factor-α (TNF-α), indoleamine 2,3-dioxygenase (IDO), kynurenine (KYN), and tryptophan (TRP).

RESULTS

CUMS induced depression-like behaviours and up-regulated the hippocampal levels of IL-1β, IL-6, TNF-α, IDO, and the KYN/TRP ratio, which were attenuated by a sub-anaesthetic dose of ketamine.

CONCLUSION

CUMS-induced depression-like behaviours are associated with a reduction in hippocampal inflammatory mediators, whereas ketamine's antidepressant effect is associated with a down-regulation of pro-inflammatory cytokines in the rat hippocampus.

Does the Method and Timing of Intravenous Ketamine Administration Affect Postoperative Morphine Requirement After Major Abdominal Surgery?

OBJECTIVE

Single intravenous bolus administration and postoperative or perioperative infusions are the most preferred methods of ketamine. Nevertheless, there is no clear explanation on the ideal ketamine administration method. In this study, we aimed to compare the effects of the most common ketamine administration methods and administration time on postoperative opioid consumption.

METHODS

Fifty-two patients undergoing colectomy for colon cancer were randomly assigned into four groups. Group 1 was the control group. Group 2 received only a single intravenous bolus dose of 0.5 mg kg(-1) ketamine at induction. Group 3 received 0.5 mg kg(-1) intravenous ketamine bolus at induction and perioperative ketamine infusion at a rate of 0.25 mg kg(-1) h(-1). Group 4 received a bolus of 0.5 mg kg(-1) intravenous ketamine at induction and perioperative and postoperative ketamine infusion at a rate of 0.25 mg kg(-1) h(-1). Postoperatively, visual analogue scale pain scores, side effects, and morphine consumption were recorded.

RESULTS

There was no statistically significant difference in postoperative pain scores. Total morphine consumption was found to be significantly lower in Group 4 compared to the other groups (p=0.03, p=0.004, p=0.03, respectively). During the 1(st), 2(nd), and 4(th) hours in the postoperative period, patient-controlled analgesia morphine consumption was significantly lower in Group 4 compared to the control group (p<0.01).

CONCLUSION

Preoperative single-bolus dose or intraoperative low-dose ketamine infusion does not decrease postoperative morphine consumption; however, per- and postoperative 48-hour ketamine infusion has a significant effect in decreasing morphine consumption without decreasing the incidence of side effects in patients undergoing major abdominal surgery.

Effect of ketamine as an adjuvant in ultrasound-guided supraclavicular brachial plexus block: A double-blind randomized clinical trial study

Background:

Supraclavicular brachial plexus block is one of the most effective anesthetic procedures in operations for the upper extremity. Ketamine has been reported to enhance the analgesic effects of local anesthetics. We have conducted this study to assess whether coadministration of ketamine can prolong the local analgesic effect of lidocaine in the supraclavicular brachial plexus block for patients undergoing elective upper extremity surgery.

Materials and Methods:

Sixty adult patients undergoing elective surgery of the elbow, forearm, wrist or hand were randomly allocated in two groups of 30 patients each. Group 1 (ketamine group) received 5 mg/kg lidocaine 1.5% plus 2 mg/kg ketamine, Group 2 (control group) received 5 mg/kg lidocaine 1.5% and saline. The outcome measures included severity of pain by using visual analog scale (VAS, 0 = no pain 10 cm = the most severe pain), time of first request for analgesia, and total dose of postoperative opioid administration. The data was analyzed using the χ² test, student's t-test, Kaplan-Meier survival analysis, and Multivariate analysis tests.

Results:

Patients in the control group had a higher VAS than patients who received ketamine, at all time points during the first 24 hours after surgery (all P < 0.05). The time of first request for analgesia in the ketamine group was significantly more than in the control group (8.93 ± 1.0 vs. 7.30 ± 1.9, respectively, P < 0.001).

Conclusion:

The addition of ketamine to lidocaine in the ultrasound-guided brachial plexus block could decrease the postoperative pain and need for analgesic. Therefore, it could be considered as an option in the brachial plexus block to enhance the analgesic action of lidocaine.

Autoimmunity and inflammation in status epilepticus: from concepts to therapies

The understanding of immunological mechanisms underlying some forms of epilepsy and encephalitis has rapidly increased for the last 10 years leading to the concept of status epilepticus of autoimmune origin. Actual treatment recommendations regarding autoimmune status epilepticus are based on retrospective case studies, pathophysiological considerations and experts' opinion. In addition, there are no clear indicators to predict outcome. In situations where autoimmune mechanisms are suspected in patients with status epilepticus, there is evidence that earlier treatment is related to better outcome. Increased awareness is mandatory to decrease the number of patients with major neurological problems or fatal outcome, which is overall about 50%. We here summarize findings of all pediatric and adult patients reported to date, and review the current state of knowledge in the field of immune therapeutic approaches of status epilepticus.

Does intravenous ketamine enhance analgesia after arthroscopic shoulder surgery with ultrasound guided single-injection interscalene block?: a randomized, prospective, double-blind trial

Ketamine has anti-inflammatory, analgesic and antihyperalgesic effect and prevents pain associated with wind-up. We investigated whether low doses of ketamine infusion during general anesthesia combined with single-shot interscalene nerve block (SSISB) would potentiate analgesic effect of SSISB. Forty adult patients scheduled for elective arthroscopic shoulder surgery were enrolled and randomized to either the control group or the ketamine group. All patients underwent SSISB and followed by general anesthesia. During an operation, intravenous ketamine was infused to the patients of ketamine group continuously. In control group, patients received normal saline in volumes equivalent to ketamine infusions. Pain score by numeric rating scale was similar between groups at 1, 6, 12, 24, 36, and 48 hr following surgery, which was maintained lower than 3 in both groups. The time to first analgesic request after admission on post-anesthesia care unit was also not significantly different between groups. Intraoperative low dose ketamine did not decrease acute postoperative pain after arthroscopic shoulder surgery with a preincisional ultrasound guided SSISB. The preventive analgesic effect of ketamine could be mitigated by SSISB, which remains one of the most effective methods of pain relief after arthroscopic shoulder surgery.

Anesthetic Management for Cardiopulmonary Bypass

Cardiopulmonary bypass has revolutionized the practice of cardiac surgery and allows safe conduct of increasingly complex cardiac surgery. A brief review of the bypass circuit is undertaken in this review. A more thorough review of the anesthetic management is accomplished including choice of anesthetic medications and their effects. The inflammatory response to cardiopulmonary bypass is reviewed along with interventions that may help ameliorate the inflammation.

Pain Management Strategies for Thoracotomy and Thoracic Pain Syndromes

Pain after thoracic surgery can be severe and, in the acute phase, contribute to perioperative morbidity and mortality. Unfortunately, patients also incur a significant risk of chronic pain. Although there are guidelines for postoperative pain management in these patients, there is no widespread surgical or anesthetic “best practice.” Here, we review the recent literature on techniques specific to perioperative pain control for thoracic patients, including medical management, neuraxial blockade, and other regional techniques, and suggest an algorithm for developing a multimodal pain management strategy.

Ketamine: synaptogenesis, immunomodulation and glycogen synthase kinase-3 as underlying mechanisms of its antidepressant properties

Major depressive disorder is an extremely debilitating condition affecting millions of people worldwide. Nevertheless, currently available antidepressant medications still have important limitations, such as a low response rate and a time lag for treatment response that represent a significant problem when dealing with individuals who are vulnerable and prone to self-harm. Recent clinical trials have shown that the N-methyl-D-aspartate receptor antagonist, ketamine, can induce an antidepressant response within hours, which lasts up to 2 weeks, and is effective even in treatment-resistant patients. Nonetheless, its use is limited due to its psychotomimetic and addictive properties. Understanding the molecular pathways through which ketamine exerts its antidepressant effects would help in the developing of novel antidepressant agents that do not evoke the same negative side effects of this drug. This review focuses specifically on the effects of ketamine on three molecular mechanisms that are relevant to depression: synaptogenesis, immunomodulation and regulation of glycogen synthase kinase-3 activity.

Ketamine and peripheral inflammation

The old anesthetic ketamine has demonstrated interactions with the inflammatory response. This review intends to qualify the nature and the mechanism underlying this interaction. For this purpose, preclinical data will be presented starting with the initial works, and then, the probable mechanisms will be discussed. A summary of the most relevant clinical data will be presented. In conclusion, ketamine appears as a unique "homeostatic regulator" of the acute inflammatory reaction and the stress-induced immune disturbances. This is of some interest at a moment when the short- and long-term deleterious consequences of inadequate inflammatory reactions are increasingly reported. Large-scale studies showing improved patient's outcome are, however, required before to definitively assert the clinical reality of this positive effect.

The CYP2B6*6 allele significantly alters the N-demethylation of ketamine enantiomers in vitro

Ketamine is primarily metabolized to norketamine by hepatic CYP2B6 and CYP3A4-mediated N-demethylation. However, the relative contribution from each enzyme remains controversial. The CYP2B6*6 allele is associated with reduced enzyme expression and activity that may lead to interindividual variability in ketamine metabolism. We examined the N-demethylation of individual ketamine enantiomers using human liver microsomes (HLMs) genotyped for the CYP2B6*6 allele, insect cell-expressed recombinant CYP2B6 and CYP3A4 enzymes, and COS-1 cell-expressed recombinant CYP2B6.1 and CYP2B6.6 protein variant. Effects of CYP-selective inhibitors on norketamine formation were also determined in HLMs. The two-enzyme Michaelis-Menten model best fitted the HLM kinetic data. The Michaelis-Menten constants (K(m)) for the high-affinity enzyme and the low-affinity enzyme were similar to those for the expressed CYP2B6 and CYP3A4, respectively. The intrinsic clearance for both ketamine enantiomers by the high-affinity enzyme in HLMs with CYP2B6*1/*1 genotype were at least 2-fold and 6-fold higher, respectively, than those for CYP2B6*1/*6 genotype and CYP2B6*6/*6 genotype. The V(max) and K(m) values for CYP2B6.1 were approximately 160 and 70% of those for CYP2B6.6, respectively. N,N'N'-triethylenethiophosphoramide (thioTEPA) (CYP2B6 inhibitor, 25 μM) and the monoclonal antibody against CYP2B6 but not troleandomycin (CYP3A4 inhibitor, 25 μM) or the monoclonal antibody against CYP3A4 inhibited ketamine N-demethylation at clinically relevant concentrations. The degree of inhibition was significantly reduced in HLMs with the CYP2B6*6 allele (gene-dose P < 0.05). These results indicate a major role of CYP2B6 in ketamine N-demethylation in vitro and a significant impact of the CYP2B6*6 allele on enzyme-ketamine binding and catalytic activity.

Ketamine: use in anesthesia

The role of ketamine anesthesia in the prehospital, emergency department and operating theater settings is not well defined. A nonsystematic review of ketamine was performed by authors from Australia, Europe, and North America. Results were discussed among authors and the final manuscript accepted. Ketamine is a useful agent for induction of anesthesia, procedural sedation, and analgesia. Its properties are appealing in many awkward clinical scenarios. Practitioners need to be cognizant of its side effects and limitations.

Ketamine exerts antidepressant effects and reduces IL-1β and IL-6 levels in rat prefrontal cortex and hippocampus

Ketamine has fast-acting and robust antidepressant effects in animal models and depressed patients. It has been hypothesized that its underlying mechanism of action is associated with the inflammatory response in the central nervous system. Therefore, the present study was designed to investigate the antidepressant effects of ketamine and the expression of interleukin (IL)-1β and IL-6 in the prefrontal cortex and hippocampus of a rat model. Twenty Wistar rats were randomly divided into 2 groups (each group, n=10); the saline group and the ketamine group. On the 1st day, rats undertook a forced swimming test (FST) for 15 min (pre-test session). On the 2nd day, saline or ketamine was administered intraperitoneally 30 min before the test session. Following this, rats performed another FST for 5 min (test session) and the immobility time was recorded. The rats were then sacrificed, and the prefrontal cortex and hippocampus were harvested for determination of IL-1β and IL-6 levels. Compared with the saline group, ketamine administration significantly decreased the immobility time of rats during the FST (P<0.05). In addition, the ketamine group demonstrated a statistically significant decrease in the expression of IL-1β and IL-6 in rat prefrontal cortex and hippocampus compared with the saline group (P<0.05). Ketamine-induced antidepressant effects are associated with decreased levels of IL-1β and IL-6 in rat prefrontal cortex and hippocampus.