The dose-dependent effect of S(+)-ketamine on cardiac output in healthy volunteers and complex regional pain syndrome type 1 chronic pain patients

Impact of different doses of esketamine on the incidence of hypotension in propofol-based sedation for colonoscopy: a randomized controlled trial

Background

Hypovolemia is common in colonoscopy due to fasting and bowel preparation, and propofol itself can reduce systemic vascular resistance, resulting in relative hypovolemia. Therefore, hypotension is not a rare event during propofol-based sedation for colonoscopy.

Objectives

Our objective was to explore the efficacy of esketamine as a sedative adjuvant in reducing the incidence of hypotension during colonoscopy.

Design

This was a prospective randomized trial. The trial was registered with the Chinese Clinical Trial Registry (ID: ChiCTR 2100047032).

Methods

We included 100 eligible patients who planned to receive a colonoscopy and randomly divided them into 4 groups with 25 patients in each group, which were propofol 2 mg/kg (Group P), propofol 1 mg/kg with esketamine 0.2 mg/kg (Group E1), propofol 1 mg/kg with esketamine 0.3 mg/kg (Group E2), and propofol 1 mg/kg with esketamine 0.4 mg/kg (Group E3). The hemodynamic and respiratory parameters were documented at various times during the procedure, including the patient's entry into the endoscopic room (T0), the induction of sedation (T1), the insertion of the colonoscope (T2), the removal of the colonoscope (T3), and the awakening of the patient (T4). The primary outcome was the incidence of hypotension. Secondary outcomes were cardiovascular side effects other than hypotension, incidence of hypoxia, cumulative changes in cardiovascular and respiratory parameters, total propofol dosage, anesthesia recovery time, and satisfactory levels of both patients and endoscopists.

Results

The incidence of hypotension in Group E1 (16%), Group E2 (16%), and Group E3 (12%) was significantly lower than in Group P (60%), with p values 0.003, 0.003, and <0.001 respectively. The cumulative changes in diastolic blood pressure and mean arterial pressure in Groups E1, E2, and E3 were significantly higher than in Group P (p = 0.024, p < 0.001, p = 0.006, respectively). Cumulative changes in systolic blood pressure in Group E3 were significantly higher than those in Group P (p = 0.012). The respiratory-related parameters were not statistically significant.

Conclusions

This study showed that the application of 0.4 mg/kg esketamine in propofol-based sedation reduced the incidence of hypotension during colonoscopy while providing satisfactory sedation.

Comparing the hemodynamic effects of ketamine versus fentanyl bolus in patients with septic shock: a randomized controlled trial

BACKGROUND

Ketamine and fentanyl are commonly used for sedation and induction of anesthesia in critically ill patients. This study aimed to compare the hemodynamic effects of ketamine versus fentanyl bolus in patients with septic shock.

METHODS

This randomized controlled trial included mechanically ventilated adults with septic shock receiving sedation. Patients were randomized to receive either 1 mg/kg ketamine bolus or 1 mcg/kg fentanyl bolus. Cardiac output (CO), stroke volume (SV), heart rate (HR), and mean arterial pressure (MAP) were measured at the baseline, 3, 6, 10, and 15 min after the intervention. Delta CO was calculated as the change in CO at each time point in relation to baseline measurement. The primary outcome was delta CO 6 min after administration of the study drug. Other outcomes included CO, SV, HR, and MAP.

RESULTS

Eighty-six patients were analyzed. The median (quartiles) delta CO 6 min after drug injection was 71(37, 116)% in the ketamine group versus - 31(- 43, - 12)% in the fentanyl group, P value < 0.001. The CO, SV, HR, and MAP increased in the ketamine group and decreased in the fentanyl group in relation to the baseline reading; and all were higher in the ketamine group than the fentanyl group.

CONCLUSION

In patients with septic shock, ketamine bolus was associated with higher CO and SV compared to fentanyl bolus.

CLINICAL TRIAL REGISTRATION

Date of registration: 24/07/2023.

CLINICALTRIALS

gov Identifier: NCT05957302. URL: https://clinicaltrials.gov/study/NCT05957302 .

Esketamine Exposure Impairs Cardiac Development and Function in Zebrafish Larvae

Esketamine is a widely used intravenous general anesthetic. However, its safety, particularly its effects on the heart, is not fully understood. In this study, we investigated the effects of esketamine exposure on zebrafish embryonic heart development. Zebrafish embryos were exposed to esketamine at concentrations of 1, 10, and 100 mg/L from 48 h post-fertilization (hpf) to 72 hpf. We found that after exposure, zebrafish embryos had an increased hatching rate, decreased heart rate, stroke volume, and cardiac output. When we exposed transgenic zebrafish of the Tg(cmlc2:EGFP) strain to esketamine, we observed ventricular dilation and thickening of atrial walls in developing embryos. Additionally, we further discovered the abnormal expression of genes associated with cardiac development, including nkx2.5, gata4, tbx5, and myh6, calcium signaling pathways, namely ryr2a, ryr2b, atp2a2a, atp2a2b, slc8a3, slc8a4a, and cacna1aa, as well as an increase in acetylcholine concentration. In conclusion, our findings suggest that esketamine may impair zebrafish larvae's cardiac development and function by affecting acetylcholine concentration, resulting in weakened cardiac neural regulation and subsequent effects on cardiac function. The insights garnered from this research advocate for a comprehensive safety assessment of esketamine in clinical applications.

Effect of esketamine on the EC50 of remifentanil for blunting cardiovascular responses to endotracheal intubation in female patients under general anesthesia: a sequential allocation dose-finding study

BACKGROUND

This study aimed to investigate the effect of esketamine on the dose-effect relationship between remifentanil and the cardiovascular response to endotracheal intubation during target-controlled infusion (TCI) of propofol.

METHODS

Patients underwent elective gynecological laparoscopic surgery under general anesthesia with endotracheal intubation, aged 18-65 years, American Society of Anesthesiologists class I or II, 18 kg/m2 ≤ body mass index ≤ 30 kg/m2, were randomly divided into the control (group C) and esketamine groups (group E). Before anesthesia induction, group E received an intravenous injection of 0.3 mg/kg of esketamine, while group C received an equal dose of physiological saline. TCI of propofol to the effect-site concentration (EC) of 3.0 μg/mL, and then TCI of remifentanil to the effect room and intravenous injection of rocuronium 0.6 mg/kg after MOAA/S was 0. Endotracheal intubation was performed after 2 min. Dixon's modified sequential method was used, and the initial EC of remifentanil was 3.0 ng/mL. The EC of remifentanil was determined according to the intubation response of the previous patient, with an adjacent concentration gradient of 0.3 ng/mL. The EC50 and EC95 values and their 95% confidence intervals (CIs) were determined using probit regression analysis.

RESULTS

The EC50 for cardiovascular response inhibition to endotracheal intubation using remifentanil was 3.91 ng/mL (95% CI: 3.59-4.33 ng/mL) and EC95 was 4.66 ng/mL (95% CI: 4.27-6.23 ng/mL) with TCI of propofol 3.0 μg/mL. After intravenous administration of 0.3 mg/kg of esketamine, the EC50 of remifentanil was 3.56 ng/mL (95% CI: 3.22-3.99 ng/mL) and EC95 was 4.31 ng/mL (95% CI: 3.91-5.88 ng/mL).

CONCLUSIONS

Combined with TCI of propofol 3.0 μg/mL for anesthesia induction, esketamine significantly reduced the EC50 and EC95 of remifentanil to inhibit the cardiovascular response to endotracheal intubation.

TRIAL REGISTRATION

The trial was registered in the Chinese Clinical Trials Registry ( www.chictr.org.cn ; registration number: ChiCTR2200064932; date of registration:24/10/2022).

Modelling buprenorphine reduction of fentanyl-induced respiratory depression

BACKGROUND

Potent synthetic opioids, such as fentanyl, are increasingly abused, resulting in unprecedented numbers of fatalities from respiratory depression. Treatment with the high-affinity mu-opioid receptor partial agonist buprenorphine may prevent fatalities by reducing binding of potent opioids to the opioid receptor, limiting respiratory depression.

METHODS

To characterize buprenorphine-fentanyl interaction at the level of the mu-opioid receptor in 2 populations (opioid-naive individuals and individuals who chronically use high-dose opioids), the effects of escalating i.v. fentanyl doses with range 0.075–0.35 mg/70 kg (opioid naive) and 0.25–0.70 mg/70 kg (chronic opioid use) on iso-hypercapnic ventilation at 2–3 background doses of buprenorphine (target plasma concentrations range: 0.2–5 ng/mL) were quantified using receptor association/dissociation models combined with biophase distribution models.

RESULTS

Buprenorphine produced mild respiratory depression, while high doses of fentanyl caused pronounced respiratory depression and apnea in both populations. When combined with fentanyl, buprenorphine produced a receptor binding–dependent reduction of fentanyl-induced respiratory depression in both populations. In individuals with chronic opioid use, at buprenorphine plasma concentrations of 2 ng/mL or higher, a protective effect against high-dose fentanyl was observed.

CONCLUSION

Overall, the results indicate that when buprenorphine mu-opioid receptor occupancy is sufficiently high, fentanyl is unable to activate the mu-opioid receptor and consequently will not cause further respiratory depression in addition to the mild respiratory effects of buprenorphine.

TRIAL REGISTRATION

Trialregister.nl, no. NL7028 (https://www.trialregister.nl/trial/7028)

FUNDING

Indivior Inc., North Chesterfield, Virginia, USA.

Research advances in the clinical application of esketamine

Esketamine is dextrorotatory ketamine, which is an enantiomer of ketamine. Compared with ketamine, it has the advantages of a fast metabolism, fewer side effects, and strong pharmacological effects, so it is more suitable for clinical use. Esketamine has a powerful analgesic effect and has little effect on breathing. It has a wide range of applications in the fields of pediatric anesthesia, conscious sedation anesthesia, and emergency analgesia. In addition, it is also used for pain that is difficult to relieve with conventional drugs and to prevent postoperative pain. Various routes of administration are also suitable for patients who need short-term analgesia and sedation. As a drug, esketamine inevitably brings some side effects when it is used clinically. In this article, by introducing the mechanism of action and pharmacological characteristics of esketamine, its clinical application is reviewed, and it provides a reference for the more reasonable and safe clinical application of esketamine.

The Options for Neuraxial Drug Administration

Neuraxial drug administration, i.e., the injection of drugs into the epidural or intrathecal space to produce anesthesia or analgesia, is a technique developed more than 120 years ago. Today, it still is widely used in daily practice in anesthesiology and in acute and chronic pain therapy. A multitude of different drugs have been introduced for neuraxial injection, only a part of which have obtained official approval for that indication. A broad understanding of the pharmacology of those agents is essential to the clinician to utilize them in a safe and efficient manner. In the present narrative review, we summarize current knowledge on neuraxial anatomy relevant to clinical practice, including pediatric anatomy. Then, we delineate the general pharmacology of neuraxial drug administration, with particular attention to specific aspects of epidural and intrathecal pharmacokinetics and pharmacodynamics. Furthermore, we describe the most common clinical indications for neuraxial drug administration, including the perioperative setting, obstetrics, and chronic pain. Then, we discuss possible neurotoxic effects of neuraxial drugs, and moreover, we detail the specific properties of the most commonly used neuraxial drugs that are relevant to clinicians who employ epidural or intrathecal drug administration, in order to ensure adequate treatment and patient safety in these techniques. Finally, we give a brief overview on new developments in neuraxial drug therapy.

Stereoselective ketamine effect on cardiac output: a population pharmacokinetic/pharmacodynamic modelling study in healthy volunteers

Background

Ketamine has cardiac excitatory side-effects. Currently, data on the effects of ketamine and metabolite concentrations on cardiac output are scarce. We therefore developed a pharmacodynamic model derived from data from a randomised clinical trial. The current study is part of a larger clinical study evaluating the potential mitigating effect of sodium nitroprusside on the psychedelic effects of ketamine.

Methods

Twenty healthy male subjects received escalating esketamine and racemic ketamine doses in combination with either placebo or sodium nitroprusside on four visits: (i) esketamine and placebo, (ii) esketamine and sodium nitroprusside, (iii) racemic ketamine and placebo, and (iv) racemic ketamine and sodium nitroprusside. During each visit, arterial blood samples were obtained and cardiac output was measured. Nonlinear mixed-effect modelling was used to analyse the cardiac output time-series data. Ketamine metabolites were added to the model in a sequential manner to evaluate the effects of metabolites.

Results

A model including an S-ketamine and S-norketamine effect best described the data. Ketamine increased cardiac output, whereas modelling revealed that S-norketamine decreased cardiac output. No significant effects were detected for R-ketamine, metabolites other than S-norketamine, or sodium nitroprusside on cardiac output.

Conclusions

S-Ketamine, but not R-ketamine, increased cardiac output in a dose-dependent manner. In contrast to S-ketamine, its metabolite S-norketamine reduced cardiac excitation in a dose-dependent manner.

Clinical trial registration

Dutch Cochrane Center 5359.

Combined Recirculatory-compartmental Population Pharmacokinetic Modeling of Arterial and Venous Plasma S(+) and R(–) Ketamine Concentrations

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

The pharmacokinetics of infused drugs have been modeled without regard for recirculatory or mixing kinetics. We used a unique ketamine dataset with simultaneous arterial and venous blood sampling, during and after separate S(+) and R(–) ketamine infusions, to develop a simplified recirculatory model of arterial and venous plasma drug concentrations.

Methods

S(+) or R(–) ketamine was infused over 30 min on two occasions to 10 healthy male volunteers. Frequent, simultaneous arterial and forearm venous blood samples were obtained for up to 11 h. A multicompartmental pharmacokinetic model with front-end arterial mixing and venous blood components was developed using nonlinear mixed effects analyses.

Results

A three-compartment base pharmacokinetic model with additional arterial mixing and arm venous compartments and with shared S(+)/R(–) distribution kinetics proved superior to standard compartmental modeling approaches. Total pharmacokinetic flow was estimated to be 7.59 ± 0.36 l/min (mean ± standard error of the estimate), and S(+) and R(–) elimination clearances were 1.23 ± 0.04 and 1.06 ± 0.03 l/min, respectively. The arm-tissue link rate constant was 0.18 ± 0.01 min–1, and the fraction of arm blood flow estimated to exchange with arm tissue was 0.04 ± 0.01.

Conclusions

Arterial drug concentrations measured during drug infusion have two kinetically distinct components: partially or lung-mixed drug and fully mixed-recirculated drug. Front-end kinetics suggest the partially mixed concentration is proportional to the ratio of infusion rate and total pharmacokinetic flow. This simplified modeling approach could lead to more generalizable models for target-controlled infusions and improved methods for analyzing pharmacokinetic-pharmacodynamic data.

Pharmacokinetics and Bioavailability of Inhaled Esketamine in Healthy Volunteers

BACKGROUND

Esketamine is traditionally administered via intravenous or intramuscular routes. In this study we developed a pharmacokinetic model of inhalation of nebulized esketamine with special emphasis on pulmonary absorption and bioavailability.

METHODS

Three increasing doses of inhaled esketamine (dose escalation from 25 to 100 mg) were applied followed by a single intravenous dose (20 mg) in 19 healthy volunteers using a nebulizer system and arterial concentrations of esketamine and esnorketamine were obtained. A multicompartmental pharmacokinetic model was developed using population nonlinear mixed-effects analyses.

RESULTS

The pharmacokinetic model consisted of three esketamine, two esnorketamine disposition and three metabolism compartments. The inhalation data were best described by adding two absorption pathways, an immediate and a slower pathway, with rate constant 0.05 ± 0.01 min (median ± SE of the estimate). The amount of esketamine inhaled was reduced due to dose-independent and dose-dependent reduced bioavailability. The former was 70% ± 5%, and the latter was described by a sigmoid EMAX model characterized by the plasma concentration at which absorption was impaired by 50% (406 ± 46 ng/ml). Over the concentration range tested, up to 50% of inhaled esketamine is lost due to the reduced dose-independent and dose-dependent bioavailability.

CONCLUSIONS

We successfully modeled the inhalation of nebulized esketamine in healthy volunteers. Nebulized esketamine is inhaled with a substantial reduction in bioavailability. Although the reduction in dose-independent bioavailability is best explained by retention of drug and particle exhalation, the reduction in dose-dependent bioavailability is probably due to sedation-related loss of drug into the air.

Stochastic Pharmacokinetic-Pharmacodynamic Analysis of the Effect of Transdermal Buprenorphine on Electroencephalogram and Analgesia

BACKGROUND

The analgesic effect of opioids is often based on subjective one dimensional measurements. Electroencephalography (EEG) offers a possibility to objectively quantify the brain's activity before and after the administration of opioids. The aim of this study was to investigate the pharmacokinetic-pharmacodynamic (PKPD) properties of the buprenorphine transdermal patch on resting EEG and pain tolerance.

METHOD

Twenty-two healthy male subjects (mean age 23.1 ± 3.8 years) were studied. They received a 144-hour buprenorphine (20 μg/h) or placebo transdermal patch in this experimental, randomized, crossover, double-blind study. Skin heat pain tolerance was measured on the arm before the recordings of resting EEG. From the EEG, the ratio of slow and fast oscillations was calculated for further analysis. A population PKPD model with a stochastic differential equation for drug absorption from the patch was used to analyze the PK and PD data simultaneously by use of the statistical analysis package NONMEM.

RESULTS

Buprenorphine increased EEG ratio (P = 0.0006) and skin pain tolerance (P = 0.0008) compared with placebo. The stochastic model adequately characterized the concentration-time and effect-time courses for both the skin heat stimulation and the resting EEG outcomes with variations in the drug's absorption rate during the 144-hour treatment period. As measured by the potency parameter, the EEG effect was 10 ± 3 (median ± SE) times more sensitive to buprenorphine than the skin pain test.

CONCLUSIONS

Using a stochastic PKPD analysis, the effect of a 144-hour buprenorphine patch application on resting EEG and skin pain tolerance was quantified successfully. Both end points were affected by buprenorphine, although the resting EEG was more sensitive to buprenorphine. The stochastic PKPD analysis allowed the computation of a time-dependent variability in drug absorption from patch to blood. The data suggest that the resting EEG is an attractive and objective alternative for assessing opioid effect.

Enantioselective inhibition of d-serine transport by (S)-ketamine

BACKGROUND AND PURPOSE

Patients with major depressive disorder receiving racemic ketamine, (R,S)-ketamine, experience transient increases in Clinician-Administered Dissociative States Scale scores and a coincident drop in plasma d-serine levels. The results suggest that (R,S)-ketamine produces an immediate, concentration-dependent pharmacological effect on d-serine plasma concentrations. One potential source of this effect is (R,S)-ketamine-induced inhibition of the transporter ASCT2, which regulates intracellular d-serine concentrations. In this study, we tested this hypothesis by examining the effect of (S)- and (R)-ketamine on ASCT2-mediated transport of d-serine in PC-12 and 1321N1 cells and primary neuronal cells in culture.

EXPERIMENTAL APPROACH

Intracellular and extracellular d-serine levels were determined using capillary electrophoresis-laser-induced fluorescence and liquid chromatography-mass spectrometry respectively. Expression of ASCT2, Asc-1 and serine racemase was determined utilizing Western blotting.

KEY RESULTS

(S)-Ketamine produced a concentration-dependent increase in intracellular d-serine and reduced extracellular d-serine accumulation. In contrast, (R)-ketamine decreased both intracellular and extracellular d-serine levels. The ASCT2 inhibitor, benzyl-d-serine (BDS), and ASCT2 gene knockdown mimicked the action of (S)-ketamine on d-serine in PC-12 cells, while the Asc-1 agonist d-isoleucine reduced intracellular d-serine and increased extracellular d-serine accumulation. This response to d-isoleucine was not affected by BDS or (S)-ketamine. Primary cultures of rat neuronal cells expressed ASCT2 and were responsive to (S)-ketamine and BDS. (S)- and (R)-ketamine increased the expression of monomeric serine racemase in all the cells studied, with (S)-ketamine having the greatest effect.

CONCLUSIONS AND IMPLICATIONS

(S)-Ketamine decreased cellular export of d-serine via selective inhibition of ASCT2, and this could represent a possible source of dissociative effects observed with (R,S)-ketamine.

The effect of ketamine on hypoventilation during deep sedation with midazolam and propofol: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Hypoventilation is a major cause of morbidity and mortality in patients having procedures under sedation. Few clinical strategies have been evaluated to reduce intraoperative hypoventilation during surgical procedures under deep sedation.

OBJECTIVE

The primary objective of this investigation was to examine the effect of ketamine on hypoventilation in patients receiving deep sedation for surgery with midazolam and propofol.

DESIGN

The study was a randomised, placebo-controlled, double-blind clinical trial.

SETTING

Intraoperative.

PATIENTS

Healthy women undergoing breast surgery.

INTERVENTION

Randomised to receive ketamine (0.5 mg kg bolus, followed by an infusion of 1.5 μg kg min) or isotonic saline.

MAIN OUTCOME MEASURE

Duration of hypercapnia measured continuously with a transcutaneous carbon dioxide (TCO2) monitor.

RESULTS

Fifty-four participants were recruited. Patient and surgical characteristics were similar between the study groups. The median percentage of the sedation time with TCO2 more than 6.7 kPa in participants in the ketamine group, 1.2% (95% confidence interval, CI, 0 to 83), was less than that in the isotonic saline group (65%, 95% CI, 0 to 88; P = 0.01). Severe hypoventilation (TCO2 >8.0 kPa) was also less in the ketamine group, median 0% (95% CI, 0 to 11.7) compared with 28% (95% CI, 0 to 79.3; P = 0.0002) for the isotonic saline group. The ketamine group required less airway manoeuvres (chin lift) to keep the SaO2 greater than 95% median (95% CI) [0 (0 to 3) compared with 3 (0 to 16) in the isotonic saline group] (P = 0.004).

CONCLUSION

Ketamine decreased the duration and severity of hypercapnia in patients undergoing deep sedation with propofol. The addition of ketamine may reduce hypoventilation and adverse effects in patients having procedures under sedation.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT01535976.