Intravenous midazolam significantly enhances the lethal effect of thiopental but not that of ketamine in mice

Basic metabolic and vascular effects of ketamine and its interaction with fentanyl

Ketamine is a short-acting general anesthetic with hallucinogenic, analgesic, and amnestic properties. In addition to its anesthetic use, ketamine is commonly abused in rave settings. While safe when used by medical professionals, uncontrolled recreational use of ketamine is dangerous, especially when mixed with other sedative drugs, including alcohol, benzodiazepines, and opioid drugs. Since synergistic antinociceptive interactions between opioids and ketamine were demonstrated in both preclinical and clinical studies, such an interaction could exist for the hypoxic effects of opioid drugs. Here, we focused on the basic physiological effects of ketamine as a recreational drug and its possible interactions with fentanyl-a highly potent opioid that induces strong respiratory depression and robust brain hypoxia. By using multi-site thermorecording in freely-moving rats, we showed that intravenous ketamine at a range of human relevant doses (3, 9, 27 mg/kg) dose-dependently increases locomotor activity and brain temperature, as assessed in the nucleus accumbens (NAc). By determining temperature differentials between the brain, temporal muscle, and skin, we showed that the brain hyperthermic effect of ketamine results from increased intracerebral heat production, an index of metabolic neural activation, and decreased heat loss due to peripheral vasoconstriction. By using oxygen sensors coupled with high-speed amperometry we showed that ketamine at the same doses increases NAc oxygen levels. Finally, co-administration of ketamine with intravenous fentanyl results in modest enhancement of fentanyl-induced brain hypoxia also enhancing the post-hypoxic oxygen increase. Therefore, in contrast to fentanyl, ketamine increases brain oxygenation but potentiates brain hypoxia induced by fentanyl.

Midazolam Attenuates Esketamine-Induced Overactive Behaviors in Mice Before the Sedation, but Not During the Recovery

Esketamine showed more potency, more rapid recovery from anesthesia, and less psychotomimetic side effects when compared with ketamine. However, the patients still experience psychotomimetic side effects of esketamine. In order to investigate whether midazolam can attenuate the esketamine-induced overactive behaviors and neuronal hyperactivities, midazolam 0, 40, 80, and 120 mg/kg combined with esketamine 50 mg/kg were administrated on Kunming mice to assess the behaviors changes during anesthesia. The indicators, including action time, duration of agitation before the sedation, duration of sedation, duration of loss of pedal withdrawal reaction (PWR), duration of loss of righting reaction (RR), duration of agitation during the recovery, and recovery time, were monitored for up to 3–4 h after intraperitoneal administration. The results demonstrated that midazolam 40, 80, and 120 mg/kg efficiently decreased the esketamine-induced overactive behaviors including ataxia, excitation, and catalepsy before sedation. Midazolam and esketamine synergically improved the anesthesia quality assessed by PWR and RR. However, even high doses of midazolam were not able to suppress the esketamine-induced psychotomimetic effects during the recovery.

Management of Ketamine Extravasation in a Pediatric Patient During Procedural Sedation

Ketamine is a commonly used intravenous and intramuscular medication for procedural sedation within pediatric emergency medicine. There is limited availability of data on the rate of absorption and use of subcutaneous ketamine administration. We describe the case of a 12-year-old male who was sedated after extravasation and subsequent absorption of ketamine 1 mg/kg from a peripheral intravenous line (PIV). Despite being an unintended route, absorption of subcutaneous ketamine resulted in satisfactory procedural sedation with no complications. Given limited data on subcutaneous ketamine pharmacokinetics, the aim of this case report is to present the observed absorption of subcutaneous ketamine due to extravasation of PIV during a pediatric procedural sedation.

Ketamine-New Possibilities in the Treatment of Depression: A Narrative Review

The SARS-CoV-2 coronavirus epidemic has led to an increase in the number of people with depression. Symptoms related to the mental sphere (mainly depression and anxiety) may be experienced by one third of the worldwide population. This entails the need for the effective and rapid treatment of depressive episodes. An effective drug seems to be s-ketamine, which was accepted in March 2019 by the Food and Drug Administration (FDA) for the treatment of drug-resistant depression. This drug provides a quick antidepressant effect with maximum effectiveness achieved after 24 h. It also appears to reduce the occurrence of suicidal thoughts. However, research into undesirable effects, especially in groups of people susceptible to psychotic episodes or those who use alcohol or psychoactive substances, is necessary.

Caffeine combined with sedative/anesthetic drugs triggers widespread neuroapoptosis in a mouse model of prematurity

OBJECTIVES

Caffeine (CAF) and sedative/anesthetic drugs (SADs) are often coadministered to premature infants in the neonatal intensive care unit (NICU). While SAD neurotoxicity in the developing brain is well established, it is not fully clear whether CAF interacts with SADs and whether this interaction is detrimental. Using a mouse model of prematurity, we hypothesized that CAF would increase apoptotic neurotoxicity when coadministered with SADs.

METHODS

Postnatal day 3 mice were treated with vehicle or 80 mg/kg CAF prior to challenge with 6 mg/kg midazolam, 40 mg/kg ketamine, or 40 μg/kg fentanyl. Six hours later, pups were sacrificed for activated caspase 3 (AC3) immunohistochemistry, and number of AC3 positive cells per mm³ throughout neocortex, hippocampus, caudate, thalamus, and colliculi was analyzed.

RESULTS

CAF caused a statistically significant increase in AC3 positive cells when coadministered with midazolam (p = 0.002), ketamine (p = 0.014), or fentanyl (p < 0.001). Our composite dataset suggests that the addition of CAF to these SADs has a supra-additive effect, causing more neurotoxicity than expected.

CONCLUSIONS

CAF may augment the neurotoxic action of SADs indicated for neonatal sedation/anesthesia in the NICU by triggering widespread apoptosis in the developing brains of premature infants.

Ketamine use: a review

AIMS

Ketamine remains an important medicine in both specialist anaesthesia and aspects of pain management. At the same time, its use as a recreational drug has spread in many parts of the world during the past few years. There are now increasing concerns about the harmful physical and psychological consequences of repeated misuse of this drug. The aim of this review was to survey and integrate the research literature on physical, psychological and social harms of both acute and chronic ketamine use.

METHOD

The literature on ketamine was systematically searched and findings were classified into the matrix of Nutt et al.'s (2007) rational scale for assessing the harms of psychoactive substances.

RESULTS

A major physical harm is ketamine induced ulcerative cystitis which, although its aetiology is unclear, seems particularly associated with chronic, frequent use of the drug. Frequent, daily use is also associated with neurocognitive impairment and, most robustly, deficits in working and episodic memory. Recent studies suggest certain neurological abnormalities which may underpin these cognitive effects. Many frequent users are concerned about addiction and report trying but failing to stop using ketamine.

CONCLUSIONS

The implications of these findings are drawn out for treatment of ketamine-induced ulcerative cystitis in which interventions from urologists and from addiction specialists should be coordinated. Neurocognitive impairment in frequent users can impact negatively upon achievement in education and at work, and also compound addiction problems. Prevention and harm minimization campaigns are needed to alert young people to these harmful and potentially chronic effects of ketamine.

Ketamine and midazolam delivered by patient-controlled analgesia in relieving pain associated with burns dressings

BACKGROUND

A study involving the use of a mixture of ketamine and midazolam delivered via patient-controlled analgesia (PCA) device was trialed to assess its effectiveness in reducing pain associated with repeated burns dressings in an adult population.

METHODS

Patients undergoing burns dressings changes were given a PCA device of ketamine and midazolam to use during the procedure. The aims were to investigate the efficacy of the device and to ascertain what (if any) adverse effects were associated with its use.

RESULTS

During the trial period, 44 patients who underwent 95 separate procedures were enrolled. The effectiveness of the device was rated (out of 10) by both staff and patients with the mean scores being 8.47 and 8.50, respectively. In all but 1 case, the proposed procedure was carried out successfully. Thirteen patients reported a total of 23 adverse effects, with hallucinations (11) being the most common.

CONCLUSIONS

The use of ketamine/midazolam delivered by PCA was shown to be an effective means of pain control during burns dressings as assessed by both staff and patients. The incidence of adverse events was low.

Improved postoperative analgesia with coadministration of preoperative epidural ketamine and midazolam

STUDY OBJECTIVE

To assess postoperative pain regulation and pharmacokinetic effects of preoperative administration of ketamine and midazolam.

DESIGN

Double-blind, randomized clinical study.

SETTING

University hospital.

PATIENTS

46 ASA physical status I and II patients (age, 26-58 yrs), scheduled for gastrectomy.

INTERVENTIONS

Patients were randomly assigned to three treatment groups: a preoperative epidural injection of 10 mL (1) ketamine (0.5 mg/kg) solution (Ket group); (2) ketamine (0.5 mg/kg) plus midazolam (0.05 mg/kg) solution (KM group); or (3) normal saline solution (Ctr group).

MEASUREMENTS

Analgesic effects were evaluated by Visual Analog Scale (VAS) pain scores at rest, time to first request for analgesic (TFA), and morphine consumption during the initial postoperative time of 48 hours. Plasma concentration of ketamine in the Ket group and the KM group was measured by high-performance liquid chromatography, and the elimination half-life of ketamine was calculated.

MAIN RESULTS

Compared with the Ctr group, the Ket and KM groups had lower VAS pain scores, longer TFA, and lower morphine consumption. The KM group had the longest TFA and the lowest morphine consumption of the three groups. The KM group also had higher plasma concentrations of ketamine 90 to 240 minutes after injection, and a longer elimination half-life of ketamine, than did the Ket group.

CONCLUSIONS

Preoperative epidural coadministration of a low dose of ketamine with midazolam is more effective in relieving postoperative pain than using ketamine alone. In addition, epidural midazolam prolongs the elimination of ketamine.

Potential of ketamine and midazolam, individually or in combination, to induce apoptotic neurodegeneration in the infant mouse brain

Recently, it was reported that anesthetizing infant rats for 6 h with a combination of anesthetic drugs (midazolam, nitrous oxide, isoflurane) caused widespread apoptotic neurodegeneration in the developing brain, followed by lifelong cognitive deficits. It has also been reported that ketamine triggers neuroapoptosis in the infant rat brain if administered repeatedly over a period of 9 h. The question arises whether less extreme exposure to anesthetic drugs can also trigger neuroapoptosis in the developing brain. To address this question we administered ketamine, midazolam or ketamine plus midazolam subcutaneously at various doses to infant mice and evaluated the rate of neuroapoptosis in various brain regions following either saline or these various drug treatments. Each drug was administered as a single one-time injection in a dose range that would be considered subanesthetic, and the brains were evaluated by unbiased stereology methods 5 h following drug treatment. Neuroapoptosis was detected by immunohistochemical staining for activated caspase-3. It was found that either ketamine or midazolam caused a dose-dependent, statistically significant increase in the rate of neuroapoptosis, and the two drugs combined caused a greater increase than either drug alone. The apoptotic nature of the neurodegenerative reaction was confirmed by electron microscopy. We conclude that relatively mild exposure to ketamine, midazolam or a combination of these drugs can trigger apoptotic neurodegeneration in the developing mouse brain.