Efficacy and safety of ketamine alone and ketamine-dexmedetomidine combination for sedation for brain computed tomography in paediatric patients with head injuries: A retrospective study

OBJECTIVE

To compare the efficacy and safety of ketamine alone with those of ketamine-dexmedetomidine combination for sedation during brain CT in paediatric patients with head injuries.

METHODS

We retrospectively analysed the data of paediatric patients who underwent sedation for brain CT at the ED. We included patients aged 6 months to 6 years with American Society of Anesthesiologists physical status I or II. The sedative protocol involved the administration of intramuscular (IM) ketamine 3 mg/kg (K), ketamine 2 mg/kg with dexmedetomidine 1.5 μg/kg (KD) or ketamine 1.5 mg/kg with dexmedetomidine 1.5 μg/kg (low-KD). The primary and secondary outcomes were sedation failure and adverse events, respectively.

RESULTS

We included 77 patients; among them, 28, 23 and 26 were in the K, KD and low-KD groups, respectively. In multivariable analysis, the combination groups (KD and low-KD groups) were significantly associated with a lower possibility of sedation failure compared to the K group (adjusted odds ratio, 0.12; 95% confidence interval, 0.02-0.56). Moreover, there were no significant differences in adverse events between the groups, and the sedation-related time variables also did not significantly differ among the three groups.

CONCLUSIONS

Our findings indicated that a combination of IM ketamine-dexmedetomidine provides effective sedation for paediatric patients undergoing brain CT without significant adverse events. Further research is needed to investigate the potential benefits of using lower doses of ketamine in combination.

The impact of scheduling ketamine as an internationally controlled substance on anaesthesia care in Sub-Saharan Africa: a case study and key informant interviews

BACKGROUND

Access to anaesthesia and surgical care is a major problem for people living in Sub-Saharan Africa. In this region, ketamine is critical for the provision of anaesthesia care. However, efforts to control ketamine internationally as a controlled substance may significantly impact its accessibility. This research therefore aims to estimate the importance of ketamine for anaesthesia and surgical care in Sub-Saharan Africa and assess the potential impact on access to ketamine if it were to be scheduled.

METHODS

This research is a mixed-methods study, comprising of a cross-sectional survey at the hospital level in Rwanda, and key informant interviews with experts on anaesthesia care in Sub-Saharan Africa. Data on availability of four anaesthetic agents were collected from hospitals (n = 54) in Rwanda. Semi-structured interviews with 10 key informants were conducted, collecting information on the importance of ketamine, the potential impact of scheduling ketamine internationally, and opinions on misuse of ketamine. Interviews were transcribed verbatim and analysed using a thematic analysis approach.

RESULTS

The survey conducted in Rwanda found that availability of ketamine and propofol was comparable at around 80%, while thiopental and inhalational agents were available at only about half of the hospitals. Significant barriers impeding access to anaesthesia care were identified, including a general lack of attention given to the specialty by governments, a shortage of anaesthesiologists and migration of trained anaesthesiologists, and a scarcity of medicines and equipment. Ketamine was described as critical for the provision of anaesthesia care as a consequence of these barriers. Misuse of ketamine was not believed to be an issue by the informants.

CONCLUSION

Ketamine is critical for the provision of anaesthesia care in Sub-Saharan Africa, and its scheduling would have a significantly negative impact on its availability for anaesthesia care.

Effects of ketamine on penile tissues in an experimental priapism model in rats

BACKGROUND

This study aimed to evaluate the histopathological and biochemical effects of ketamine on penile tissues following ischemia-reperfusion injury induced by priapism.

METHODS

Twenty-four male rats were randomized into three groups. Group 1 served as the control group. Group 2 underwent the priapism model to induce ischemia-reperfusion injury. Group 3, the treatment group, experienced a similar ischemia-reperfusion model as Group 2; additionally, 50 mg/kg of ketamine was administered intraperitoneally just before reperfusion. Blood biochemical analyses and penile histopathological evaluations were performed.

RESULTS

In Group 3, significant improvements were observed in all histopathological scores, including desquamation, edema, inflammation, and vasocongestion compared to Group 2 (p<0.001). Blood biochemical analyses showed that the malondialdehyde (MDA) levels were recorded as 10 in Group 2, with a significant decrease in Group 3 (p=0.013). Similarly, proinflammatory cytokine levels, including interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), were found to be suppressed in Group 3 compared to Group 2 (p=0.003, p=0.022, and p=0.028, respectively). Antioxidant enzyme activities, such as glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), were higher in Group 3 compared to Group 2 (p=0.016 and p=0.024, respec-tively).

CONCLUSION

Ketamine is an effective anesthetic agent in alleviating the effects of penile ischemia-reperfusion injury.

Electrocardiography, Blood Pressure Measurements, Vital Parameters and Anaesthetic Indices in the African Giant Rat (Cricetomys Gambianus Waterhouse) Immobilized with Diazepam or Ketamine

In spite of the increasing use and importance of the African giant rat (Cricetomys gambianus Waterhouse) in research, and other fields, like location of landmines, there is still not enough information on their physiology. In this study, we assessed the electrocardiogram, blood pressure, vital parameters and anaesthetic indices of the African giant rat (Cricetomys gambianus Waterhouse), both genders, using diazepam or ketamine as chemical restraints. A total of 24 adult African Giant Rats (AGR), 12 males and 12 females were used in this experiment. The animals were divided into two groups of twelve animals each (6 males and 6 females). One group was assessed for the effect of diazepam, and the other group ketamine. Diazepam (Roche®, Switzerland) was administered intraperitoneally at a dose rate of 7.5 mg/kg, while ketamine was administered intraperitoneally at a dose rate of 45 mg/kg. Parameters measured were recorded from the time desirable sedation was achieved, and every 15 minutes till the animal was awake. Animals administered diazepam took a longer time to sleep or achieve desirable sedative state, a longer time to respond to stimuli before waking up fully and a longer time to be fully awake, relative to ketamine-induced sedation. Ketamine caused a continuous increase in respiratory rate and blood pressure, while diazepam caused a continuous decrease in the respiratory rate. The electrocardiogram showed tachycardia throughout the experiment with the use of both drugs, although this was more pronounced with the use of diazepam, causing a decrease in QRS interval and a decrease in QT interval. Gender differences were observed in most parameters measured. The results obtained gave baseline values for electrocardiogram and blood pressure readings, while also detailing the changes and gender differences observed with sedation. In addition, results indicated ketamine is best used for short procedures and diazepam at a higher dose used for procedures requiring longer time in the African giant rat.

Enhanced Fear Memories and Altered Brain Glucose Metabolism (18F-FDG-PET) following Subanesthetic Intravenous Ketamine Infusion in Female Sprague-Dawley Rats

Although women and men are equally likely to receive ketamine following traumatic injury, little is known regarding sex-related differences in the impact of ketamine on traumatic memory. We previously reported that subanesthetic doses of an intravenous (IV) ketamine infusion following fear conditioning impaired fear extinction and altered regional brain glucose metabolism (BGluM) in male rats. Here, we investigated the effects of IV ketamine infusion on fear memory, stress hormone levels, and BGluM in female rats. Adult female Sprague–Dawley rats received a single IV ketamine infusion (0, 2, 10, or 20 mg/kg, over a 2-h period) following auditory fear conditioning (three pairings of tone and footshock). Levels of plasma stress hormones, corticosterone (CORT) and progesterone, were measured after the ketamine infusion. Two days after ketamine infusion, fear memory retrieval, extinction, and renewal were tested over a three-day period. The effects of IV ketamine infusion on BGluM were determined using ¹⁸F-fluoro-deoxyglucose positron emission tomography (¹⁸F-FDG-PET) and computed tomography (CT). The 2 and 10 mg/kg ketamine infusions reduced locomotor activity, while 20 mg/kg infusion produced reduction (first hour) followed by stimulation (second hour) of activity. The 10 and 20 mg/kg ketamine infusions significantly elevated plasma CORT and progesterone levels. All three doses enhanced fear memory retrieval, impaired fear extinction, and enhanced cued fear renewal in female rats. Ketamine infusion produced dose-dependent effects on BGluM in fear- and stress-sensitive brain regions of female rats. The current findings indicate that subanesthetic doses of IV ketamine produce robust effects on the hypothalamic–pituitary–adrenal (HPA) axis and brain energy utilization that may contribute to enhanced fear memory observed in female rats.

Intranasal dexmedetomidine and intranasal ketamine association allows shorter induction time for pediatric sedation compared to intranasal dexmedetomidine and oral midazolam

BACKGROUND

Non-painful diagnostic procedures require an inactive state for a prolonged time, so that sedation is often needed in younger children to perform the procedures. Our standard of care in this setting consists of the association between oral midazolam (0.5 mg/kg) and intranasal dexmedetomidine (4 mcg/kg). One of the limits of this approach is that the onset of action is quite delayed (up to 55 min) and poorly predictable. We chose to compare this association with intranasal-ketamine and intranasal-dexmedetomidine.

METHODS

This is a "pre-post" study. The study population included the first forty children receiving sedation with the "new" combination intranasal ketamine (3 mg/kg) and intranasal dexmedetomidine (4 mcg/kg) compared to a historical cohort including the last forty children receiving sedation with our standard of care combination of intranasal dexmedetomidine (4mcg/kg) and oral midazolam (0,5 mg/kg).

RESULTS

The association intranasal dexmedetomidine and intranasal ketamine allowed for a significantly shorter sedation induction time than the combination intranasal dexmedetomidine and oral midazolam (13,5 min versus 35 min). Both group's cumulative data showed a correlation between age and sedation effectiveness, with younger children presenting a higher success rate and shorter induction time (p 0,001).

CONCLUSIONS

This study suggests that the ketamine and dexmedetomidine intranasal association may have a shorter onset of action when compared to intranasal dexmedetomidine and oral midazolam.

Minimally invasive protocols and quantification for microglia-mediated perineuronal net disassembly in mouse brain

Enzymatic digestion of the extracellular matrix with chondroitinase-ABC reinstates juvenile-like plasticity in the adult cortex as it also disassembles the perineuronal nets (PNNs). The disadvantage of the enzyme is that it must be applied intracerebrally and it degrades the ECM for several weeks. Here, we provide two minimally invasive and transient protocols for microglia-enabled PNN disassembly in mouse cortex: repeated treatment with ketamine-xylazine-acepromazine (KXA) anesthesia and 60-Hz light entrainment. We also discuss how to analyze PNNs within microglial endosomes-lysosomes.

For complete details on the use and execution of this protocol, please refer to Venturino et al. (2021).

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PNN disassembly with repeated ketamine-mediated anesthesia in mice

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60 Hz light entrainment as an alternative approach

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Strategy to quantify density of PNN-coated cells

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Determine PNN material enriched within microglial lysosomes

Subanesthetic ketamine rapidly alters medial prefrontal miRNAs involved in ubiquitin-mediated proteolysis

Ketamine is a dissociative anesthetic and a non-competitive NMDAR antagonist. At subanesthetic dose, ketamine can relieve pain and work as a fast-acting antidepressant, but the underlying molecular mechanism remains elusive. This study aimed to investigate the mode of action underlying the effects of acute subanesthetic ketamine treatment by bioinformatics analyses of miRNAs in the medial prefrontal cortex of male C57BL/6J mice. Gene Ontology and KEGG pathway analyses of the genes putatively targeted by ketamine-responsive prefrontal miRNAs revealed that acute subanesthetic ketamine modifies ubiquitin-mediated proteolysis. Validation analysis suggested that miR-148a-3p and miR-128-3p are the main players responsible for the subanesthetic ketamine-mediated alteration of ubiquitin-mediated proteolysis through varied regulation of ubiquitin ligases E2 and E3. Collectively, our data imply that the prefrontal miRNA-dependent modulation of ubiquitin-mediated proteolysis is at least partially involved in the mode of action by acute subanesthetic ketamine treatment.

Pediatric Sedation in the Emergency Department: Trends from a Nationwide Population-based Study in Korea, 2007-2018

BACKGROUND

Pediatric sedation in the emergency department (ED) is widely performed in Korea; thus exploring the trends of its use is necessary. This study aimed to investigate the characteristics of patients and sedatives use in the ED and verify their changes over recent years.

METHODS

A nationwide population-based retrospective study was conducted including pediatric patients aged ≤ 15 years who received sedative medication in the ED and were discharged during 2007-2018, using the Korean Health Insurance Review and Assessment Service database. Patient characteristics (age, sex, level of ED, and diagnosis) and type of sedative used were analyzed.

RESULTS

Sedation was performed in total 468,221 visits during 2007-2018 (399,320 visits, at least 3.8% of overall ED visits during 2009-2018). Among these, 71.0% were children aged 1-3 years and 93.5% were sedated to support diagnosis of injury. An increase in total sedation was observed in patients aged 4-6 years during the study period (from 13.8% to 21.8%). A gradual decrease in the use of chloral hydrate (CH) compared with an increase in ketamine use was observed (CH, from 70.6% to 28.6%; ketamine, from 23.8% to 60.7%). Therefore, ketamine was the most used sedative since 2014. The most frequently used sedatives over the study period differed according to age groups (CH in <1 year and 1-3 years; ketamine in 4-6 years and 7-10 years; and midazolam in 11-15 years).

CONCLUSIONS

The characteristics of patients related to sedatives use in the ED have changed over time. These changes should be considered in the development of future Korean guidelines regarding pediatric sedation in the ED.

Dissociative symptoms with intravenous ketamine in treatment-resistant depression exploratory observational study

There is evidence for ketamine use in treatment-resistant depression (TRD). Several safety and tolerability concerns arise regarding adverse drug reactions and specific subpopulations. This paper aims to investigate the relationship between dissociative and psychometric measures in course of intravenous ketamine treatment in TRD inpatients with major depressive disorder and bipolar disorder.This study result represents safety data in a population of 49 inpatients with major depressive disorder and bipolar disorder subjects receiving eight 0.5 mg/kg of ketamine intravenous infusions, with a duration of 40 min each, as an add-on treatment to standard-of-care pharmacotherapy, registered in the naturalistic observational protocol of the tertiary reference unit for mood disorders (NCT04226963). The safety psychometrics assessed dissociation and psychomimetic symptomatology with the Clinician-Administered Dissociative States Scale (CADSS) the Brief Psychiatric Rating Scale (BPRS).The significant differences in CADSS scores between measurements in course of the treatment were observed (P = .003). No significant differences between BPRS measurements were made after infusions. In each case, both BPRS and CADSS values dropped to the "absent" level within 1 hour from the infusion. Neither CADSS nor BPRS scores were associated with the treatment outcome.The study demonstrates a good safety profile of intravenous ketamine as an add-on intervention to current psychotropic medication in TRD. The abatement of dissociation was observed in time with no sequelae nor harm. The study provides no support for the association between dissociation and treatment outcome.This study may be underpowered due to the small sample size. The protocol was defined as a study on acute depressive symptomatology without blinding.

Out-of-Hospital Ketamine: Indications for Use, Patient Outcomes, and Associated Mortality

STUDY OBJECTIVE

To describe out-of-hospital ketamine use, patient outcomes, and the potential contribution of ketamine to patient death.

METHODS

We retrospectively evaluated consecutive occurrences of out-of-hospital ketamine administration from January 1, 2019 to December 31, 2019 reported to the national ESO Data Collaborative (Austin, TX), a consortium of 1,322 emergency medical service agencies distributed throughout the United States. We descriptively assessed indications for ketamine administration, dosing, route, transport disposition, hypoxia, hypercapnia, and mortality. We reviewed cases involving patient death to determine whether ketamine could be excluded as a potential contributing factor.

RESULTS

Indications for out-of-hospital ketamine administrations in our 11,291 patients were trauma/pain (49%; n=5,575), altered mental status/behavioral indications (34%; n=3,795), cardiovascular/pulmonary indications (13%; n=1,454), seizure (2%; n=248), and other (2%; n=219). The highest median dose was for altered mental status/behavioral indications at 3.7 mg/kg (interquartile range, 2.2 to 4.4 mg/kg). Over 99% of patients (n=11,274) were transported to a hospital. Following ketamine administration, hypoxia and hypercapnia were documented in 8.4% (n=897) and 17.2% (n=1,311) of patients, respectively. Eight on-scene and 120 in-hospital deaths were reviewed. Ketamine could not be excluded as a contributing factor in 2 on-scene deaths, representing 0.02% (95% confidence interval 0.00% to 0.07%) of those who received out-of-hospital ketamine. Among those with in-hospital data, ketamine could not be excluded as a contributing factor in 6 deaths (0.3%; 95% confidence interval 0.1% to 0.7%).

CONCLUSION

In this large sample, out-of-hospital ketamine was administered for a variety of indications. Patient mortality was rare. Ketamine could not be ruled out as a contributing factor in 8 deaths, representing 0.07% of those who received ketamine.

Ketamine for Pain Management: A Review of Literature and Clinical Application

Ketamine is a dissociative anesthetic used increasingly as analgesia for different manifestations of pain, including acute, chronic, cancer and perioperative pain as well as pain in the critically ill patient population. Its distinctive pharmacologic properties may provide benefits to individuals suffering from pain, including increased pain control and reduction in opioid consumption and tolerance. Despite wide variability in proposed dosing and method of administration when used for analgesia, it is important all clinicians be familiar with the pharmacodynamics of ketamine in order to appropriately anticipate its therapeutic and adverse effects.

Ketamine-50 years in use: from anesthesia to rapid antidepressant effects and neurobiological mechanisms

Over the past 50 years, ketamine has solidified its position in both human and veterinary medicine as an important anesthetic with many uses. More recently, ketamine has been studied and used for several new indications, ranging from chronic pain to drug addiction and post-traumatic stress disorder. The discovery of the rapid-acting antidepressant effects of ketamine has resulted in a surge of interest towards understanding the precise mechanisms driving its effects. Indeed, ketamine may have had the largest impact for advancements in the research and treatment of psychiatric disorders in the past few decades. While intense research efforts have been aimed towards uncovering the molecular targets underlying ketamine's effects in treating depression, the underlying neurobiological mechanisms remain elusive. These efforts are made more difficult by ketamine's complex dose-dependent effects on molecular mechanisms, multiple pharmacologically active metabolites, and a mechanism of action associated with the facilitation of synaptic plasticity. This review aims to provide a brief overview of the different uses of ketamine, with an emphasis on examining ketamine's rapid antidepressant effects spanning molecular, cellular, and network levels. Another focus of the review is to offer a perspective on studies related to the different doses of ketamine used in antidepressant research. Finally, the review discusses some of the latest hypotheses concerning ketamine's action.

Subcutaneous ketamine prolongs the analgesic effect of local infiltration of plain Bupivacaine in children undergoing inguinal herniotomy

Background

Inguinal herniotomy is one of the commonest paediatric surgical procedures at the University of Benin Teaching Hospital. Incisional infiltration with plain bupivacaine has been used to provide postoperative analgesia for this procedure but with a short duration of action, 4–6 hours.

Aims/Objectives

The aim of this study therefore was to evaluate the efficacy of subcutaneous ketamine on post-operative analgesia in children undergoing unilateral inguinal herniotomy

Methods

Forty-six (46) ASA I or II patients aged three to seven years scheduled for unilateral inguinal herniotomy were recruited. The patients were randomized to receive surgical wound site infiltration with plain bupivacaine plus subcutaneous injection of ketamine for group I or surgical wound site infiltration plain bupivacaine plus 2ml of saline subcutaneously for group II at the end of surgery. Data obtained were analyzed using SPSS version 20. Continuous data were compared using student t-test while categorical data were compared using Chi-square or Fisher's exact test. P-value <0.05 was considered statistically significant.

Results

In group, I, the mean time to first analgesic request was 667.7 minutes (11.12 hours) and in group II, it was 371.3 minutes (6.2 hours) with p<0.001. The pain scores were better and more favourable in group I from the 8th hour and above of the assessment period. The mean post-operative analgesic consumption in 24 hours was less in group I (19.35±5.4mg) than in group II (27.32±5.8 mg) with p-value <0.001.

Conclusion

The study showed that subcutaneous ketamine prolonged the analgesic effect of plain bupivacaine surgical wound site infiltration in children undergoing unilateral inguinal herniotomy.

Effective Field Immobilization of Andean Fox (Lycalopex culpaeus) with Ketamine-Dexmedetomidine and Antagonism with Atipamezole

A combination (mean±SD) of ketamine (4.0±1.0 mg/kg in juveniles and 3.0±0.4 in adults) and dexmedetomidine (0.055±0.01 and 0.049±0.01, respectively), reversed with atipamezole (at 10 mg/mg of dexmedetomidine), was assessed in 57 Andean foxes (Lycalopex culpaeus) in field conditions. Induction times in juveniles and adults were 4.6±3.9 min and 4.3±2.4 min, respectively. Immobilization was smooth and safe, and lasted 50±8 min in juveniles and 50±10 min in adults. Full recovery was recorded at 40±29 min in juveniles and 37±23 min in adults after atipamezole administration. Drug dose, season, body temperature, and fox sex and body condition were not related to variations in induction and recovery times, body temperature, heart rate, respiratory rate, or hemoglobin oxygen saturation. No side effects were observed other than a slight but significant decrease in mean body temperature during the procedure. This combination allowed carrying out all the typical procedures of a research project, including the collection of several biologic samples.

Update on the Physiologic Effects of Ketamine in General Anesthesia and Spinal Blockade: A Review of the Literature

Ketamine, a phencyclidine analog and dissociative anesthetic, has been used in anesthesia since the 1960s. Serial subanesthetic administration has been explored for treatment of depression and chronic pain; however, there has been a recent surge in its intraoperative and perioperative use among anesthesia providers. As ketamine becomes an important addition to multimodal acute pain regimens, it important that anesthesia providers review the physiologic underpinnings of ketamine administration. Herein, we review the primary scientific literature and discuss recent studies that have implicated ketamine in inflammation and oxidative stress, inhibition of ion channels in dorsal horn neurons, and in disruption of frontoparietal communication. Also discussed are the potential clinical implications these effects may have for patients.

Ketamine sensitization: Influence of dose, environment, social isolation and treatment interval

Ketamine is a dissociative anesthetic first developed in the 1960s but is increasingly used at subanesthetic doses for both clinical and non-clinical purposes. There is evidence from human recreational users of compulsive use and addiction. Sensitization is an increase in an effect of a drug with repeated use that is thought to be important in the development of addiction. Research on psychomotor stimulants has shown the development of sensitization in laboratory animals to be modified by factors that influence addiction. In the current paper we describe four experiments on the development of sensitization in laboratory rats aimed at determining if ketamine sensitization is also influenced by factors thought to be important in addiction. Adult, male Sprague-Dawley rats received ketamine (5, 10, 20 or 50 mg/kg i.p.) for five or more days and the development of locomotor sensitization was followed. Experiment 1 examined the ability of low doses of ketamine to produce sensitization and found sensitization at 5, 10 and 20 mg/kg. Experiment 2 examined the influence of environmental context and found that ketamine sensitization (20 mg/kg) was greater when administration occurred in a novel environment (the experimental apparatus) than in home cages. Experiment 3 found that ketamine sensitization (20 mg/kg) did not occur when animals were housed in social isolation but occurred readily in pair-housed animals. Finally, Experiment 4 found that ketamine sensitization (20 or 50 mg/kg) was similar whether drug was administered daily or at 3-day intervals. Together, the results demonstrate that ketamine sensitization is robust and reliable, occurring under a variety of circumstances. Moreover, ketamine sensitization is influenced by factors that influence the development of addiction in humans. The current results may lead to a better understanding of ketamine abuse and addiction and may help inform clinical use of the drug.

Ketamine and Treatment-Resistant Depression

Major depressive disorder affects tens of millions of people each year. One-third of those affected have depression that is resistant to conventional pharmacologic, psychologic, or somatic treatments. Patients with treatment-resistant depression have few remedies other than electroconvulsive therapy or transcranial magnetic stimulation. Recent research has highlighted the promising antidepressant effects of subanesthetic ketamine infusions. This journal course examines the efficacy of ketamine for treatment-resistant depression. Evidence from 10 systematic reviews and randomized controlled trials suggest that most of the researchers concluded ketamine significantly decreased depression severity ratings at short-term assessment intervals, whereas evidence examining the long-term effects is lacking. Ketamine infusion therapy was generally well tolerated, with minimal untoward effects. Large, randomized controlled trials are needed to discern the longer-term efficacy, tolerance, and dependence profiles of ketamine infusions. Optimal dosing schedules to best prolong the antidepressant effects of ketamine have yet to be determined.

Effect of Anesthesia on Intraocular Pressure Measured With Continuous Wireless Telemetry in Nonhuman Primates

Purpose

To compare the effects of both injectable anesthesia (ketamine/dexmedetomidine versus ketamine/xylazine) and inhalant anesthesia (isoflurane) on IOP using continuous, bilateral IOP telemetry in nonhuman primates (NHP).

Methods

Bilateral IOP was recorded continuously using a proven implantable telemetry system in five different sessions at least 2 weeks apart in four male rhesus macaques under two conditions: ketamine (3 mg/kg) with dexmedetomidine (50 μg/kg) or ketamine with xylazine (0.5 mg/kg) for induction, both followed by isoflurane for maintenance. IOP transducers were calibrated via anterior chamber manometry. Bilateral IOP was averaged over 2 minutes after injectable anesthetic induction and again after isoflurane inhalant had stabilized the anesthetic plane, then compared to baseline IOP measurements acquired immediately prior to anesthesia (both before and after initial human contact).

Results

When compared to pre-contact baseline measurements, ketamine/dexmedetomidine injectable anesthesia lowers IOP by 1.5 mm Hg on average (P < 0.05), but IOP did not change with ketamine/xylazine anesthesia. IOP returned to baseline levels shortly after isoflurane gas anesthesia was initiated. However, injectable anesthesia lowered IOP by an average of 5.4 mm Hg when compared to that measured after initial human contact (P < 0.01).

Conclusions

Anesthetic effects on IOP are generally small when compared to precontact baseline but much larger when compared to IOP measures taken after human contact, indicating that IOP is temporarily elevated due to acute stress (similar to a "white coat effect") and then decreased with anesthetic relaxation. Anesthetic induction with ketamine/xylazine and maintenance with isoflurane gas should be used when IOP is measured postanesthesia.

Single Dose of Ketamine During Kyphoplasty Procedures Does Not Reduce Postoperative Narcotic Consumption

This retrospective cohort study aimed to explore the study institution’s intraoperative ketamine use during kyphoplasty and compare narcotic requirements in patients who received intraoperative ketamine with those who did not. The authors hypothesized that a single dose of ketamine during kyphoplasty would reduce postoperative narcotic consumption. Included patients underwent kyphoplasty under monitored anesthesia care between 2012 and 2013. Excluded patients were younger than 18 years or had general anesthesia, endotracheal intubation, or major intraoperative complications. Narcotics were converted into morphine equivalents for comparison. Analysis included c², correlation analyses, multivariate regression analysis, and analysis of variance. Overall, 279 patients were included. Men were a minority of the sample, 26.2% (73/279). More than 83% of patients were ASA class 3 (232/279), and more than 50% repaired a single vertebra (154/279). A single dose of ketamine was administered in 15.8% of kyphoplasties, with an average dose of 38.7 mg (range = 2-150 mg). Intraoperative ketamine administration was predictive of decreased intraoperative narcotic requirements (P < .001) but was not associated with decreased postoperative narcotic requirements (P = .442). Patients remained hemodynamically stable in the preoperative and postoperative period. Ketamine did not reduce postoperative narcotic consumption but reduced intraoperative narcotic consumption in this sample.

Sex- and dose-dependent abuse liability of repeated subanesthetic ketamine in rats

RATIONALE

Subanesthetic ketamine (KET) elicits rapid, robust, but transient antidepressant effects. KET's antidepressant actions can be augmented and maintained for a longer duration when repeatedly delivered. However, KET is recreationally abused, raising long-term treatment safety concerns. Women are more likely than men to seek treatment for depression, escalate from casual to compulsive drug use, and are more sensitive to antidepressants. Similarly, female rodents are more sensitive than males to KET's rapid antidepressant-like behavioral effects; dose-response thresholds in these assays equal 2.5 and 5.0mg/kg (i.p.), respectively. This suggests the utility of preclinical rodent models in optimizing sex-differential KET therapy protocols and minimizing adverse drug reactions.

OBJECTIVES

Here, we assessed behavioral and biochemical correlates of abuse liability following six serial KET treatments on alternating days at three subanesthetic, antidepressant-like doses (2.5, 5.0, or 10mg/kg, i.p.) in adult male and female rats. A potential role for ΔFosB-mediated transcription in the nucleus accumbens is outlined in the context of KET-mediated locomotor sensitization.

RESULTS

Antidepressant-like threshold doses (2.5, 5.0mg/kg KET) failed to evoke a conditioned place preference in all animals, but only males positively responded to a higher dose (10mg/kg). Behavioral sensitization to 5.0 or 10mg/kg KET's locomotor-activating effects was established in both sexes, and females' sensitized response to 5.0mg/kg was greater than males'. KET-induced hyperlocomotion positively correlated with ΔFosB protein expression in the nucleus accumbens. rAAV-ΔJunD inhibition of ΔFosB-mediated transcription in the accumbens failed to block locomotor sensitization to 10mg/kg KET.

CONCLUSIONS

These data suggest that in rats, six alternating-day treatments with 2.5mg/kg KET do not induce apparent behavioral signatures of abuse liability despite accumulation of ΔFosB protein in the accumbens. Additionally, females are more sensitive than males to KET's locomotor-stimulant properties, both acutely and after repeated treatments. More studies are needed to determine brain regions and neural mechanisms responsible for KET-induced behavioral adaptations and to extrapolate these data to inform sex-dependent strategies for long-term KET therapy protocols for depression.

The long-term effects of single and repeated subanaesthetic ketamine administration on regional cerebral blood flow in healthy dogs measured with 99mTc-HMPAO SPECT

Subanaesthetic ketamine has recently been established as an effective and rapid treatment for major depressive disorder showing antidepressant effects for up to 1 week on average. The use of repeated ketamine infusions has been put forward to augment and to prolong the antidepressant response and increase the remission rates. The underlying neurobiological mechanisms responsible for ketamine's antidepressant effects remain unclear. Nevertheless, it has been shown, both in dogs and humans, that ketamine can alter neuronal perfusion and therefore neuronal function in brain regions involved in psychiatric and behavioural disorders. Consequently, the aim of the current placebo controlled study was to assess the long-term effects on cerebral perfusion of single and repeated subanaesthetic ketamine infusions in dogs. Twelve healthy, laboratory dogs were scanned at six different time points following single and repeated ketamine administration, using Single Photon Emission Computed Tomography with the radiotracer ^99mTc-hexamethylpropylene amine oxime. We hypothesised that repeated infusions could lead to more prolonged perfusion alterations in brain regions critical for behaviour regulation. We found that repeated subanaesthetic ketamine administration did not result in more prolonged cerebral perfusion alterations compared to a single ketamine administration.

Ketamine as a potential option in the treatment of short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing

A number of treatment options have been used over the years in short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) with variable results. The most common preventive treatments include carbamazepine, lamotrigine, indomethacin, gabapentin and topiramate. Ketamine is being increasingly used in the treatment of neuropathic pain. The parentral formulations are generally used as oral preparations have poor bioavailability. Recently, ketamine lozenges have been shown to have sufficiently high bioavailability to support their use as a preventive treatment in a number of conditions causing intractable neuropathic pain. We report a 58-year-old man whose symptoms of SUNCT were not responsive to conventional preventive treatments but responded well to a subcutaneous, sub-anaesthetic ketamine infusion and subsequently, sublingual ketamine lozenges.

Comparison of effects of propofol and ketofol (Ketamine-Propofol mixture) on emergence agitation in children undergoing tonsillectomy

BACKGROUND

The aim of this study was to compare the effect of propofol and ketofol (ketamine-propofol mixture) on EA in children undergoing tonsillectomy.

METHOD

In this randomized clinical trial, 87 ASA class I and II patients, aged 3-12 years, who underwent tonsillectomy, were divided into two groups to receive either propofol 100 µg/kg/min (group p, n=44) or ketofol : ketamine 25 µg/kg/min + propofol 75 µg/kg/min (group k, n= 43). Incidence and severity of EA was evaluated using the Pediatric Anesthesia Emergence Delirium (PAED) scales on arrival at the recovery room, and 10 and 30 min after that time.

RESULTS

There was no statistically significant difference in demographic data between the two groups. In the ketofol group, the need for agitation treatment and also mean recovery duration were lower than in the propofol group (30 and 41%, and 29.9 and 32.7 min), without statistically significant difference (P value=0.143 and P value=0.187). Laryngospasm or bronchospasm occurred in 2 patients in each group and bleeding was observed in only one individual in the ketofol group.

CONCLUSION

Infusion of ketofol in children undergoing tonsillectomy provides shorter recovery time and lower incidence of EA despite the non significant difference with propofol.

The pharmacokinetics of ketamine following intramuscular injection to F344 rats

Ketamine is a glutamate N-methyl-D-aspartate receptor antagonist that is a rapid-acting dissociative anesthetic. It has been proposed as an adjuvant treatment along with other drugs (atropine, midazolam, pralidoxime) used in the current standard of care (SOC) for organophosphate and nerve agent exposures. Ketamine is a pharmaceutical agent that is readily available to most clinicians in emergency departments and possesses a broad therapeutic index with well-characterized effects in humans. The objective of this study was to determine the pharmacokinetic profile of ketamine and its active metabolite, norketamine, in F344 rats following single or repeated intramuscular administrations of subanesthetic levels (7.5 mg/kg or 30 mg/kg) of ketamine with or without the SOC. Following administration, plasma and brain tissues were collected and analyzed using a liquid chromatography-mass spectrometry method to quantitate ketamine and norketamine. Following sample analysis, the pharmacokinetics were determined using non-compartmental analysis. The addition of the current SOC had a minimal impact on the pharmacokinetics of ketamine following intramuscular administration and repeated dosing at 7.5 mg/kg every 90 minutes allows for sustained plasma concentrations above 100 ng/mL. The pharmacokinetics of ketamine with and without the SOC in rats supports further investigation of the efficacy of ketamine co-administration with the SOC following nerve agent exposure in animal models.

A fixed moderate-dose combination of tiletamine+zolazepam outperforms midazolam in induction of short-term immobilization of ball pythons (Python regius)

Laboratory animals are commonly anesthetized to prevent pain and distress and to provide safe handling. Anesthesia procedures are well-developed for common laboratory mammals, but not as well established in reptiles. We assessed the performance of intramuscularly injected tiletamine (dissociative anesthetic) and zolazepam (benzodiazepine sedative) in fixed combination (2 mg/kg and 3 mg/kg) in comparison to 2 mg/kg of midazolam (benzodiazepine sedative) in ball pythons (Python regius). We measured heart and respiratory rates and quantified induction parameters (i.e., time to loss of righting reflex, time to loss of withdrawal reflex) and recovery parameters (i.e., time to regain righting reflex, withdrawal reflex, normal behavior). Mild decreases in heart and respiratory rates (median decrease of <10 beats per minute and <5 breaths per minute) were observed for most time points among all three anesthetic dose groups. No statistically significant difference between the median time to loss of righting reflex was observed among animals of any group (p = 0.783). However, the withdrawal reflex was lost in all snakes receiving 3mg/kg of tiletamine+zolazepam but not in all animals of the other two groups (p = 0.0004). In addition, the time for animals to regain the righting reflex and resume normal behavior was longer in the drug combination dose groups compared to the midazolam group (p = 0.0055). Our results indicate that midazolam is an adequate sedative for ball pythons but does not suffice to achieve reliable immobilization or anesthesia, whereas tiletamine+zolazepam achieves short-term anesthesia in a dose-dependent manner.

Effects of Subanesthetic Intravenous Ketamine Infusion on Corticosterone and Brain-Derived Neurotrophic Factor in the Plasma of Male Sprague-Dawley Rats

Posttrauma anesthetic agents influence neuroendocrine responses that may affect fear memory. The effects of a subanesthetic intravenous (IV) ketamine infusion on mediators of stress and memory in rodents are unknown. Therefore, we used a clinically relevant method to administer a 2-hour subanesthetic IV ketamine infusion following a rodent fear-conditioning paradigm (paired tone plus foot shock) to evaluate the effects on corticosterone and brain-derived neurotrophic factor in the plasma of male Sprague-Dawley rats. We found that subanesthetic ketamine infusions (5 and 20 mg/kg/h) dose-dependently increased plasma corticosterone levels. Ketamine at 20 mg/kg/h significantly reduced plasma brain-derived neurotrophic factor measured 2 hours after the conclusion of the ketamine infusion. These results demonstrate that a subanesthetic IV ketamine infusion maintained a heightened neuroendocrine stress response after fear conditioning and reduced levels of a neurotrophin associated with memory, which may influence fear memory processing. The behavioral outcomes of these effects are unknown and warrant future investigation.

Ketamine dosing for sedation during repeated radiotherapy sessions in children

Background/aim

We report the analysis of ketamine doses needed and the recovery times in pediatric oncology patients undergoing repeated radiotherapy sessions.

Materials and methods

In a single-blind prospective study design, thirty-three pediatric patients undergoing radiotherapy due to oncologic disorders received 2 mg/kg ketamine and 10 μg/kg atropine intravenously and the rescue drug to be administered was ketamine at 0.5 mg/kg when the sedation level was inadequate. Total ketamine consumption, additional doses, and recovery time were recorded.

Results

Data of 635 consecutive radiotherapy sessions were evaluated. There was no significant alteration in total ketamine consumption required to complete the radiotherapy periods during consecutive procedures (P > 0.05). However, the recovery times started to decrease by the fourth session (P = 0.02) and continued to decrease onwards during the whole study period (P = 0.001). The mean of the first recovery time was 13.68 ± 3.99 min, whereas the mean of the last recovery time was 7.66 ± 6.35 min.

Conclusion

A requirement for an incremental increase in ketamine dose after subsequent administrations was not detected, despite a significant decrease in recovery times being anticipated when ketamine is used repeatedly for sedative purposes in consecutive radiotherapy sessions.

S(+)-ketamine : Current trends in emergency and intensive care medicine

S(+)-ketamine, the pure dextrorotatory enantiomer of ketamine has been available for clinical use in analgesia and anesthesia for more than 25 years. The main effects are mediated by non-competitive inhibition of the N-methyl-D-aspartate (NMDA) receptor but S(+)-ketamine also interacts with opioid receptors, monoamine receptors, adenosine receptors and other purinergic receptors. Effects on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, metabotropic glutamate receptors (mGluR) and L‑type calcium chanels have also been described. S(+)-ketamine stimulates the sympathetic nerve system, making it an ideal drug for analgosedation or induction of anesthesia in instable patients. In addition, the neuroprotective properties, bronchodilatory, antihyperalgesic or antiepileptic effects provide interesting therapeutic options. In this article we discuss the numerous effects of S(+)-ketamine under pharmacological and clinical aspects especially for typical indications in emergency medicine as well as intensive care.

Total intravenous anesthesia using a midazolam-ketamine-xylazine infusion in horses: 46 cases (2011-2014)

This study evaluated use of midazolam, ketamine, and xylazine (MKX) for total intravenous (IV) anesthesia (TIVA) in horses. Medical records of 46 horses undergoing a clinical procedure using MKX for TIVA were reviewed. Age, breed, procedure, heart rate (HR), respiratory rate (RR), pre-anesthetic drugs, induction drugs, and total volume of MKX were recorded. Duration of anesthesia, time to standing, number of attempts to stand, and recovery score were also recorded. All horses were premedicated with an alpha-2 adrenoceptor agonist and anesthesia was induced with ketamine and midazolam. Duration of MKX infusion was 33 ± 14 min. Heart rate and RR decreased during the infusion of MKX. Time to endotracheal extubation was 19 ± 12 min. Horses stood at 33 ± 13 min. Median number of attempts to stand was 1. Maintenance of anesthesia of horses with MKX was useful for a variety of procedures and recovery from anesthesia was good.

Cerebral blood flow predicts differential neurotransmitter activity

Application of metabolic magnetic resonance imaging measures such as cerebral blood flow in translational medicine is limited by the unknown link of observed alterations to specific neurophysiological processes. In particular, the sensitivity of cerebral blood flow to activity changes in specific neurotransmitter systems remains unclear. We address this question by probing cerebral blood flow in healthy volunteers using seven established drugs with known dopaminergic, serotonergic, glutamatergic and GABAergic mechanisms of action. We use a novel framework aimed at disentangling the observed effects to contribution from underlying neurotransmitter systems. We find for all evaluated compounds a reliable spatial link of respective cerebral blood flow changes with underlying neurotransmitter receptor densities corresponding to their primary mechanisms of action. The strength of these associations with receptor density is mediated by respective drug affinities. These findings suggest that cerebral blood flow is a sensitive brain-wide in-vivo assay of metabolic demands across a variety of neurotransmitter systems in humans.

Behavioral Changes in Children After Emergency Department Procedural Sedation

OBJECTIVE

The purpose of this study was to determine the proportion of children undergoing procedural sedation for fracture reduction in the emergency department (ED) observed to experience negative postdischarge behaviors. Predictors of negative behaviors were evaluated, including anxiety.

METHODS

This was a prospective cohort study of children receiving intravenous ketamine sedation for ED fracture reduction. The child's anxiety prior to sedation was measured with the Modified Yale Preoperative Anxiety Scale. Negative behavioral changes were measured with the Post-Hospitalization Behavior Questionnaire 1 to 2 weeks after discharge. Descriptive statistics and odds ratios (ORs) were calculated. Chi-square test was used for comparisons between groups. Multivariable logistic regression models evaluated predictors of negative behavioral change after discharge.

RESULTS

Ninety-seven patients were enrolled; 82 (85%) completed follow-up. Overall, 33 (40%) children were observed to be highly anxious presedation and 18 (22%) had significant negative behavior changes after ED discharge. Independent predictors for negative behaviors were high anxiety (OR = 9.0, 95% confidence interval [CI] = 2.3-35.7) and nonwhite race (OR = 6.5, 95% CI = 1.7-25.0).

CONCLUSION

For children undergoing procedural sedation in the ED, two in five children have high preprocedure anxiety and almost one in four have significant negative behaviors 1 to 2 weeks after discharge. Highly anxious and nonwhite children have increased risk of negative behavioral changes that have not been previously recognized in the ED setting.

Comparison of hemodynamic effects of sevoflurane and ketamine as basal anesthesia by a new and direct monitoring during induction in children with ventricular septal defect: A prospective, randomized research

BACKGROUND

Sevoflurane and ketamine are commonly used to obtain sedation and facilitate intravenous anesthetic induction in children undergoing cardiac surgery who are uncooperative. We used a new and direct systemic hemodynamic monitoring technique pressure recording analytical method and compared the hemodynamic effects of sevoflurane and ketamine to facilitate intravenous anesthetic induction.

METHODS

Forty-four children with ventricular septal defect (2.2 ± 1.2 years) were enrolled and randomized to receive sevoflurane (Group S) or intramuscular ketamine (Group K) for sedation, followed by intravenous midazolam-sufentanil induction and tracheal intubation. Recorded parameters included heart rate (HR), arterial pressures, stroke volume index (SVI), cardiac index (CI), systemic vascular resistance index (SVRI), the maximal slope of systolic upstroke (dp/dtmax) after sedation obtained with sevoflurane or ketamine, 1, 2, 5 minutes after midazolam-sufentanil, 1, 2, 5, and 10 minutes after tracheal intubation. Rate-pressure product (RPP) and cardiac power output (CPO) were calculated.

RESULTS

As compared with Group S, Group K had faster decreases during intravenous anesthetic induction in arterial pressures (P < .01 for all), higher HR, arterial pressures, SVRI, dp/dtmax, RPP, lower SVI, CI, CPO (P < .05 for all) during the study period.

CONCLUSION

As compared with sevoflurane, ketamine facilitated intravenous anesthetic induction exerts unfavorable effects on systemic hemodynamic and myocardial energetic in children with ventricular septal defect.

Depression in chronic ketamine users: Sex differences and neural bases

Chronic ketamine use leads to cognitive and affective deficits including depression. Here, we examined sex differences and neural bases of depression in chronic ketamine users. Compared to non-drug using healthy controls (HC), ketamine-using females but not males showed increased depression score as assessed by the Center of Epidemiological Studies Depression Scale (CES-D). We evaluated resting state functional connectivity (rsFC) of the subgenual anterior cingulate cortex (sgACC), a prefrontal structure consistently implicated in the pathogenesis of depression. Compared to HC, ketamine users (KU) did not demonstrate significant changes in sgACC connectivities at a corrected threshold. However, in KU, a linear regression against CES-D score showed less sgACC connectivity to the orbitofrontal cortex (OFC) with increasing depression severity. Examined separately, male and female KU showed higher sgACC connectivity to bilateral superior temporal gyrus and dorsomedial prefrontal cortex (dmPFC), respectively, in correlation with depression. The linear correlation of sgACC-OFC and sgACC-dmPFC connectivity with depression was significantly different in slope between KU and HC. These findings highlighted changes in rsFC of the sgACC as associated with depression and sex differences in these changes in chronic ketamine users.

Ketamine as treatment for depression

Ketamine infusions administered intravenously 1 to 3 times per week are the quickest and most effective treatment for depression. Short-course ketamine medication is established treatment both for unipolar depression and depressive episodes of bipolar affective disorder. Ketamine is suitable for initiating the treatment for treatment-resistant depression, alleviation of suicidal tendencies, and treatment of depressive patients suffering from simultaneous pain. The safety of prolonged treatment with ketamine is not known to sufficient degree. However, even long periods (up to 1.5 years) of ketamine treatment have not been associated with adverse effects. It would be appropriate to use short-course ketamine treatment more often than is currently done.

Anaesthetic and cardiopulmonary effects of intramuscular morphine, medetomidine and ketamine administered to telemetered cats

The quality and duration of anaesthesia, cardiorespiratory effects and recovery characteristics of a morphine, medetomidine, ketamine (MMK) drug combination were determined in cats. Six healthy, adult female cats were administered 0.2 mg/kg morphine sulphate, 60 μg/kg medetomidine hydrochloride, and 5 mg/kg ketamine hydrochloride intramuscularly. Atipamezole was administered intramuscularly at 120 min after MMK administration. Time to lateral recumbency, intubation, extubation and sternal recumbency were recorded. Cardiorespiratory variables and response to a noxious stimulus were recorded before and at 3 min and 10 min increments after drug administration until sternal recumbency. The time to lateral recumbency and intubation were 1.9±1.2 and 4.3±1.2 min, respectively. Body temperature and haemoglobin saturation with oxygen remained unchanged compared to baseline values throughout anaesthesia. Respiratory rate, tidal volume, minute volume, heart rate, and blood pressure were significantly decreased during anaesthesia compared to baseline values. One cat met criteria for hypotension (systolic blood pressure <90 mmHg). End tidal carbon dioxide increased during anaesthesia compared to baseline values. All but one cat remained non-responsive to noxious stimuli from 3 to 120 min. Time to extubation and sternal recumbency following atipamezole were 2.9±1.1 and 4.7±1.0 min, respectively. MMK drug combination produced excellent short-term anaesthesia and analgesia with minimal cardiopulmonary depression. Anaesthesia lasted for at least 120 min in all but one cat and was effectively reversed by atipamezole.

Comparison of intranasal ketamine versus IV morphine in reducing pain in patients with renal colic

BACKGROUND

Various drugs have been used to relieve abdominal pain in patients with renal colic. Ketamine is a popular choice as an analgesic.

OBJECTIVE

To compare the effectiveness of intranasal (IN) ketamine versus intravenous (IV) morphine in reducing pain in patients with renal colic.

METHODS

A randomized double-blind controlled trial was performed in 53 patients with renal colic recruited from the emergency department (ED) in 2015. Finally, 40 patients were enrolled in this study. Patients in the ketamine group received IN ketamine 1 mg/kg and IV placebo while patients in the control group received IV morphine 0.1mg/kg and IN placebo. Our goal was to assess visual analogue scale (VAS) changes between the 2 groups. Patients' VAS scores were reported before and 5, 15, 30min after drug injection.

RESULTS

Before drug administration, the mean±SD VAS score was 7.40±1.18 in the morphine group (group A) and 8.35±1.30 in the ketamine group (group B) (P-value=0.021). After adjustment by the appropriate analysis, the mean±SD VAS score in group (A) and (B) at 5min were (6.07±0.47 vs 6.87±0.47; mean difference -0.79, 95% confidence interval (CI) -1.48 to -1.04) (P-value=0.025), at 15 and 30min, the mean±SD VAS score in group (A) and (B) were (5.24±0.49 vs 5.60±0.49; mean difference -0.36, 95% CI -1.08 to 0.34) and (4.02±0.59 vs 4.17±0.59; mean difference -0.15, 95% CI -1.02 to 0.71) (P-value=0.304 and 0.719) respectively.

CONCLUSIONS

IN ketamine may be effective in decreasing pain in renal colic.

Effects of a medetomidine-ketamine combination on Schirmer tear test I results of clinically normal cats

OBJECTIVE

To evaluate the effects of a medetomidine-ketamine combination on tear production of clinically normal cats by use of the Schirmer tear test (STT) 1 before and during anesthesia and after reversal of medetomidine with atipamezole.

ANIMALS

40 client-owned crossbred domestic shorthair cats (23 males and 17 females; age range, 6 to 24 months).

PROCEDURES

A complete physical examination, CBC, and ophthalmic examination were performed on each cat. Cats with no abnormalities on physical and ophthalmic examinations were included in the study. Cats were allocated into 2 groups: a control group (n = 10 cats) anesthetized by administration of a combination of medetomidine hydrochloride (80 μg/kg) and ketamine hydrochloride (5 mg/kg), and an experimental group (30) anesthetized with the medetomidine-ketamine combination and reversal by administration of atipamezole. Tear production of both eyes of each cat was measured by use of the STT I before anesthesia, 15 minutes after the beginning of anesthesia, and 15 minutes after administration of atipamezole.

RESULTS

Anesthesia with a medetomidine-ketamine combination of cats with no ophthalmic disease caused a significant decrease in tear production. The STT I values returned nearly to preanesthetic values within 15 minutes after reversal with atipamezole, whereas the STT I values for the control group were still low at that point.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that a tear substitute should be administered to eyes of cats anesthetized with a medetomidine-ketamine combination from the time of anesthetic administration until at least 15 minutes after administration of atipamezole.

A comparison of prophylactic use of meperidine, meperidine plus dexamethasone, and ketamine plus midazolam for preventing of shivering during spinal anesthesia: a randomized, double-blind, placebo-controlled study

STUDY OBJECTIVES

The aim of this study is to compare the efficacy of combination of meperidine and dexamethasone with that of placebo, meperidine alone, and the combination of ketamine and midazolam in preventing shivering during spinal anesthesia.

DESIGN

This is a prospective, placebo-controlled study.

SETTING

The setting is at an operating room of a university-based teaching hospital.

PATIENTS

Two hundred American Society of Anesthesiologists I and II patients undergoing orthopedic and urologic surgery under spinal anesthesia were included.

INTERVENTIONS

Subarachnoid anesthesia was performed by using 15mg of 0.5% hyperbaric bupivacaine. Patients were randomly allocated to receive saline (placebo, group C), meperidine 0.4mg/kg (group Me), ketamine 0.25mg/kg plus midazolam 37.5μg/kg (group KMi), and meperidine 0.2mg/kg plus dexamethasone 0.1mg/kg (group MeD). All drugs were given as an intravenous bolus immediately after intrathecal injection.

MEASUREMENTS

During surgery and stay in the recovery room, shivering score, blood pressure, and some other adverse effects were recorded at 5-minute intervals. Axillary and tympanic temperatures were recorded at 15-minute intervals during the perioperative period.

MAIN RESULTS

The incidence of shivering after 30minutes of spinal anesthesia in groups C, Me, KMi, and MeD was 64%, 20%, 20%, and 4%, respectively, which was significantly higher in group C compared with other groups (P<.0001). Regarding adverse effects, there was no significant difference between groups (P≥.2). Axillary temperature significantly increased in the 15th-120th-minute interval in groups Me, KMi, and MeD (P<.0001) and in group MeD was higher than that in other groups. Core temperature decreased in the 15th-120th-minute interval in group MeD, lower than that in other groups (P<.0001).

CONCLUSIONS

Prophylactic use of meperidine 0.2mg/kg plus dexamethasone 0.1mg/kg was more effective than meperidine 0.4mg/kg as a sole agent or the combination of ketamine 0.25mg/kg and midazolam 37.5μg/kg in preventing shivering resulting from spinal anesthesia.

Effects of ketamine and lidocaine in combination on the sevoflurane minimum alveolar concentration in alpacas

This study investigated the effects of ketamine and lidocaine in combination on the minimum alveolar concentration of sevoflurane (MACSEVO) in alpacas. Eight healthy, intact male, adult alpacas were studied on 2 separate occasions. Anesthesia was induced with SEVO, and baseline MAC (MACB) determination began 45 min after induction. After MACB determination, alpacas were randomly given either an intravenous (IV) loading dose (LD) and infusion of saline or a loading dose [ketamine = 0.5 mg/kg body weight (BW); lidocaine = 2 mg/kg BW] and an infusion of ketamine (25 μg/kg BW per minute) in combination with lidocaine (50 μg/kg BW per minute), and MACSEVO was re-determined (MACT). Quality of recovery, time-to-extubation, and time-to-standing, were also evaluated. Mean MACB was 1.88% ± 0.13% and 1.89% ± 0.14% for the saline and ketamine + lidocaine groups, respectively. Ketamine and lidocaine administration decreased (P < 0.05) MACB by 57% and mean MACT was 0.83% ± 0.10%. Saline administration did not change MACB. Time to determine MACB and MACT was not significantly different between the treatments. The quality of recovery, time-to-extubation, and time-to-standing, were not different between groups. The infusion of ketamine combined with lidocaine significantly decreased MACSEVO by 57% and did not adversely affect time-to-standing or quality of recovery.

High-Dose Ketamine Sedation of an Agitated Patient During Air Medical Transport

We report a case in which a high-dose ketamine infusion was used to sedate an agitated patient for air medical transport, avoiding the risks of general anesthesia and causing no exacerbation of psychiatric symptoms.

Low-Dose Ketamine Pretreatment Reduces the Incidence and Severity of Myoclonus Induced by Etomidate: A Randomized, Double-Blinded, Controlled Clinical Trial

Myoclonic movement induced by etomidate is a common but undesirable problem during general anesthesia induction. To investigate the influence of pretreatment with low-dose ketamine on the incidence and severity of myoclonus induced by etomidate, 104 patients were randomized allocated to 1 of 2 equally sized groups (n = 52) to receive either intravenous low-dose ketamine 0.5 mg/kg (group K) or an equal volume of normal saline (group S) 1 minute before induction of anesthesia with 0.3-mg/kg etomidate. The incidence and severity of myoclonus were assessed for 2 minutes after administration of etomidate. Here, we found that the incidence and intensity of myoclonus were both significantly reduced in low-dose ketamine-treated group compared with saline-treated group. The incidence of adverse effects was low and similar between groups. These results demonstrate that intravenous infusion of low-dose ketamine 0.5 mg/kg 1 minute prior to etomidate administration is effective in relieving etomidate-induced myoclonic movements during general anesthesia induction.

Decreasing the need for mechanical ventilation after surgery for retinopathy of prematurity: sedoanalgesia vs. general anesthesia

BACKGROUND/AIM

Premature infants experience more respiratory problems after surgical procedures. We aimed to compare general anesthesia with sedation regarding the need for postoperative mechanical ventilation in infants undergoing retinopathy of prematurity (ROP) surgery.

MATERIALS AND METHODS

Sixty patients who underwent laser surgery for ROP were included in this study. This study was performed between October 2010 and December 2012. The sedation group (Group S, n = 30) received 1 mg/kg ketamine and 1 mg/kg propofol as a bolus for induction. The patients then received an infusion of 100-150 μg kg(-1) min(-1) propofol and 0.25 mg kg(-1) h(-1) ketamine for maintenance. In the general anesthesia group (Group G, n = 30), anesthesia was induced using 8% sevoflurane by inhalation with 50% nitrous oxide in oxygen. Anesthesia was maintained with sevoflurane (2%) and 50% nitrous oxide in oxygen.

RESULTS

There was no difference in gestational age, birth weight, current age, or current body weight between the two groups. Preoperative medical histories of the groups were similar. Two patients in Group S and 11 patients in Group G required postoperative mechanical ventilation (P = 0.010). Blood pressures and heart rates were similar.

CONCLUSION

In premature infants, sedoanalgesia administration reduced the need for postoperative mechanical ventilation after surgery for ROP.

Previous Ketamine Produces an Enduring Blockade of Neurochemical and Behavioral Effects of Uncontrollable Stress

Recent interest in the antidepressant and anti-stress effects of subanesthetic doses of ketamine, an NMDA receptor antagonist, has identified mechanisms whereby ketamine reverses the effect of stress, but little is known regarding the prophylactic effect ketamine might have on future stressors. Here we investigate the prophylactic effect of ketamine against neurochemical and behavioral changes that follow inescapable, uncontrollable tail shocks (ISs) in Sprague Dawley rats. IS induces increased anxiety, which is dependent on activation of serotonergic (5-HT) dorsal raphe nucleus (DRN) neurons that project to the basolateral amygdala (BLA). Ketamine (10 mg/kg, i.p.) administered 2 h, 1 week, or 2 weeks before IS prevented the increased extracellular levels of 5-HT in the BLA typically produced by IS. In addition, ketamine administered at these time points blocked the decreased juvenile social investigation produced by IS. Microinjection of ketamine into the prelimbic (PL) region of the medial prefrontal cortex duplicated the effects of systemic ketamine, and, conversely, systemic ketamine effects were prevented by pharmacological inhibition of the PL. Although IS does not activate DRN-projecting neurons from the PL, IS did so after ketamine, suggesting that the prophylactic effect of ketamine is a result of altered functioning of this projection.

SIGNIFICANCE STATEMENT

The reported data show that systemic ketamine, given up to 2 weeks before a stressor, blunts behavioral and neurochemical effects of the stressor. The study also advances understanding of the mechanisms involved and suggests that ketamine acts at the prelimbic cortex to sensitize neurons that project to and inhibit the DRN.

Initial Experience with IV Ketamine Infusion for Treatment of Post Sternotomy Pain in a Patient with a Total Artificial Heart

The implantation of total artificial hearts (TAH) via midline sternotomy for the treatment of severe biventricular cardiac dysfunction is associated with complex postoperative pain management. Ketamaine increases blood pressure by raising sympathetic outflow and cardiac output; however, ketamine is a direct vasodilator on isolated arterial tissues. In the setting of a TAH with a mechanically fixed cardiac output, a ketamine infusion for postoperative pain control has the potential to decrease blood pressure due to direct arterial vasodilation. We present the initial experience with a ketamine infusion in a patient with a TAH with minimal observed decreases in blood pressure and significantly improved postoperative pain.

Ketamine/propofol admixture (ketofol) at induction in the critically ill against etomidate (KEEP PACE trial): study protocol for a randomized controlled trial

BACKGROUND

Endotracheal intubation (ETI) is commonly performed as a life-saving procedure in the intensive care unit (ICU). It is often associated with significant hemodynamic perturbations and can severely impact the outcome of ICU patients. Etomidate is often chosen by many critical care providers for the patients who are hypotensive because of its superior hemodynamic profile compared to other induction medications. However, recent evidence has raised concerns about the increased incidence of adrenal insufficiency and mortality associated with etomidate use. A combination of ketamine and propofol (known as ketofol) has been studied in various settings as an alternative induction agent. In recent years, studies have shown that this combination may provide adequate sedation while maintaining hemodynamic stability, based on the balancing of the hemodynamic effects of these two individual agents. We hypothesized that ketofol may offer a valuable alternative to etomidate in critically ill patients with or without hemodynamic instability.

METHODS/DESIGN

A randomized controlled parallel-group clinical trial of adult critically ill patients admitted to either a medical or surgical ICU at Mayo Clinic in Rochester, MN will be conducted. As part of planned emergency research, informed consent will be waived after appropriate community consultation and notification. Patients undergoing urgent or emergent ETI will receive either etomidate or a 1:1 admixture of ketamine and propofol (ketofol). The primary outcome will be hemodynamic instability during the first 15 minutes following drug administration. Secondary outcomes will include ICU length of stay, mortality, adrenal function, ventilator-free days and vasoactive medication use, among others. The planned sample size is 160 total patients.

DISCUSSION

The overall goal of this trial is to assess the hemodynamic consequences of a ketamine-propofol combination used in critically ill patients undergoing urgent or emergent ETI compared to etomidate, a medication with an established hemodynamic profile. The trial will address a crucial gap in the literature regarding the optimal induction agent for ETI in patients that may have potential or established hemodynamic instability. Greater experience with planned emergency research will, hopefully, pave the way for future prospective randomized clinical trials in the critically ill population.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02105415. 31 March 2014.