Melatonin and anesthesia: a clinical perspective

Combining melatonin with dexmedetomidine improves anesthesia in rats

Melatonin (ML) and dexmedetomidine (DM) are used separately as anesthetic premedication or as an anesthetic in humans and laboratory animals. In this study, we aimed to investigate the anesthetic properties of both drugs combined. The anesthetic effects of several combinations of ML (50 and 100 mg/kg) and DM (50 and 100 μg/kg) were evaluated in rats by observing behavioral manifestations and recording the duration and depth of anesthesia. Five anesthetic intervals were established according to the loss and recovery of reflexes. While each individual drug did not induce an appropriate anesthetic effect at the tested doses, ML50 + DM100, ML100 + DM50 and ML100 + DM100 combinations resulted in surgical anesthesia intervals of 60 to 360 min. Together, our results point that the use of ML allows to decrease the dose of DM, reducing the unwanted anesthetic effects of this α2-agonist.

Assessing the Premedication Properties of Sublingual Melatonin in Young Women Undergoing Cesarean Section With Spinal Anesthesia: A Double-Blind Randomized Study

INTRODUCTION

Preoperative anxiety can negatively impact patient outcomes by influencing the intraoperative requirements for anesthetics and analgesics, increasing postoperative pain intensity, and augmenting the need for analgesia. Moreover, it may contribute to higher rates of postoperative morbidity and mortality following certain types of surgery. This study investigates the anxiolytic and sedative properties of sublingual melatonin as a premedication agent in young females undergoing cesarean section under spinal anesthesia.

METHODS

A double-blind, randomized, placebo-controlled trial was conducted in Nasiriyah, Iraq. Eighty females were included, 40 in each group, based on specific inclusion and exclusion criteria. Premedication was administered in the morning, 60 minutes before the procedure. In the melatonin group (M), patients received 10 mg of sublingual melatonin, while the placebo group (P) received placebo premedication. Anxiety and sedation levels were evaluated three times: before taking premedication, five minutes before the insertion of the spinal needle, and one hour postoperatively, using the visual analog scale and Richmond Sedation Scale.

RESULTS

The results show a highly significant P-value regarding anxiety levels between the M Group and P Group (p-value < 0.001). There was a significant difference in the median sedation scores between the studied groups at pre-spinal insertion and postoperatively (p-value < 0.001). The mean heart rate in the M Group was significantly lower than in the P Group (p-value = 0.0019). Significant differences were noted in systolic and diastolic blood pressures between the two groups, measured five minutes before and after spinal needle insertion (p-value < 0.001).

CONCLUSION

These findings contribute to understanding the impact of sublingual melatonin as an anxiolytic and sedative premedication agent on patients undergoing elective cesarean sections under spinal anesthesia. Further research is warranted to fully elucidate the benefits and implications of melatonin administration in such procedures.

Comparison of the Effects of Desflurane and Sevoflurane on Variations in Salivary Melatonin and Sleep Disturbance After Total Knee Arthroplasty: A Single-center, Prospective, Randomized, Controlled, Open-label Study

PURPOSE

Anesthesia has been shown to disrupt the circadian rhythm. Recovery of the circadian rhythm after general anesthesia might help alleviate symptoms of insomnia and postoperative delirium. We hypothesized that recovery of the circadian rhythm is faster after total knee arthroplasty (TKA) with desflurane than with sevoflurane. This study compared the influence of sevoflurane versus desflurane anesthesia on the postoperative circadian rhythm of melatonin in adults undergoing TKA.

DESIGN

Single-center, prospective, randomized, controlled, open-label study.

METHODS

This study involved adult patients undergoing TKA at a university hospital in Japan from May 1, 2018 to December 31, 2019. The primary outcome of the study was the comparison of the effect of sevoflurane and desflurane on the circadian rhythm of salivary melatonin for 3 days postoperatively. The secondary outcomes were postoperative fatigue and sleep quality for 3 days postoperatively.

FINDINGS

Twenty-eight patients (American Society of Anesthesiologists physical status of I or II) were scheduled for TKA and randomized to receive sevoflurane (n = 14) or desflurane (n = 14) anesthesia. There was no significant difference in the melatonin concentration between the sevoflurane and desflurane groups. The salivary melatonin concentration after sevoflurane or desflurane anesthesia was significantly higher at 9:00 p.m. on a postoperative day (POD)0 and POD1 than on POD3 (P < .05). Patients in the desflurane group had significantly greater fatigue than those in the sevoflurane group at 7:00 a.m. and 12:00 p.m. on POD3 (P < .05). Patients in the sevoflurane group had a deeper sleep than those in the desflurane group on POD0 (P < .05). In the sevoflurane group, the sleep time during the night of POD2 was longer than that on POD0 (6.1 vs 4.2 hours, P < .05).

CONCLUSIONS

Under the current study conditions, desflurane was equivalent to sevoflurane in terms of the postoperative salivary melatonin concentration and sleep disturbance after TKA but not in terms of recovering the postoperative circadian rhythm.

The Effect of Melatonin on Analgesia, Anxiety, and Intraocular Pressure (IOP) in Cataract Surgery Under Topical Anesthesia

PURPOSE

This study investigated the effect of oral melatonin as a premedication before cataract surgery on pain score, anxiety, surgical conditions, and intraocular pressure (IOP) during cataract surgery with phacoemulsification under topical anesthesia.

DESIGN

This randomized, double-blind prospective study was conducted among 120 patients aged 50 to 80.

METHODS

Patients were randomly assigned to receive either sublingual melatonin 3 mg or placebo 60 min before surgery. Verbal anxiety and pain scores, heart rate, systolic and diastolic blood pressure, intraocular pressure, and quality of surgical conditions were recorded. The results were analyzed using SPSS 23 software, and statistical analysis consisted of χ² test and t-test, and a P value less than .05 was considered significant.

FINDINGS

There was a significant difference between the two groups regarding pain after the surgery before being discharged from the recovery room. The mean pain score in the melatonin group was lower than the placebo group in T4 (in the postoperative ward) (P < .05). The anxiety score of patients was lower in the melatonin group in T3 and T4 (during surgery and in the postoperative ward, respectively) (P < .05). IOP was significantly lower in the case group at the end of the surgery after receiving premedication (P = .021).

CONCLUSIONS

This study showed that 3 mg Sublingual melatonin premedication for patients undergoing cataract surgery under topical anesthesia reduced patients' anxiety scores, pain score, and IOP.

Melatonin suppresses sympathetic vasomotor tone through enhancing GABAA receptor activity in the hypothalamus

Introduction: Melatonin (5-methoxy-N-acetyl-tryptamine) is a circadian hormone synthesized and secreted by the pineal gland. In addition to regulating circadian rhythms of many physiological functions, melatonin is involved in regulating autonomic nervous function and blood pressure. Hypothalamus paraventricular nucleus (PVN), receiving melatonin projections from the superchiasmatic nucleus, is a critical brain region to regulate neuroendocrine and cardiovascular function. Here, we determined the synaptic mechanisms involved in the effect of melatonin on the sympathetic outflow and blood pressure.

Methods and Results: Microinjection of melatonin into the PVN produced a depressor effect and decreased renal sympathetic nerve activity (RSNA). While microinjection of luzindole, a non-selective melatonin receptor antagonist, into the PVN did not change melatonin-induced sympathoinhibition, GABAA receptor antagonist bicuculline eliminated melatonin-induced sympathoinhibition. Furthermore, melatonin decreased firing rate of retrogradely labeled PVN neurons which project to the rostral ventrolateral medulla (RVLM), an effect was not altered by luzindole but eliminated by bicuculline. Melatonin significantly increased the amplitude of spontaneous and evoked GABAergic inhibitory synaptic currents, as well as GABA-induced currents.

Conclusion: These data suggest that melatonin in the PVN suppresses sympathetic vasomotor tone through enhancing GABAA receptor activity. This study provides novel information for understanding the cellular mechanisms involved in the effect of melatonin on regulating blood pressure and sympathetic output.

The effects of melatonin on the concentrations of inflammatory cytokines and proteins, serotonin, cortisol and melatonin in ovariohysterectomised female dogs

BACKGROUND

Ovariohysterectomy (OHE) induces inflammation and stress in female dogs. The anti-inflammatory effects of melatonin have been reported in several studies.

OBJECTIVES

The goal of this study was to assess the effects of melatonin on the concentrations of melatonin, cortisol, serotonin, α-1-acid glycoprotein (AGP), serum amyloid A (SAA), c-reactive protein (CRP), interleukin-10 (IL-10), interleukin-8 (IL-8), interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) before and after OHE.

METHODS

The total number of animals was 25 and aligned in 5 groups. Fifteen dogs were divided into three groups (n = 5): melatonin, melatonin+anaesthesia and melatonin+OHE and received melatonin (0.3 mg/kg, p.o.) on days -1, 0, 1, 2 and 3. Ten dogs were assigned to the control and OHE groups (n = 5) without melatonin treatment. OHE and anaesthesia were performed on day 0. Blood samples were obtained via jugular vein on days -1, 1, 3 and 5.

RESULTS

Melatonin and serotonin concentrations significantly increased in the melatonin, melatonin+OHE and melatonin+anaesthesia groups compared with the control group, while cortisol concentration decreased in the melatonin+OHE group compared with the OHE group. The concentrations of acute-phase proteins (APPs) and inflammatory cytokines significantly increased after OHE. The CRP, SAA and IL-10 concentrations decreased significantly in the melatonin+OHE group compared with the OHE group. The concentrations of cortisol, APPs and proinflammatory cytokines increased significantly in the melatonin+anaesthesia group compared with the melatonin group.

CONCLUSIONS

The oral administration of melatonin before and after OHE help controlling the high levels of inflammatory APPs, cytokines and cortisol induced by OHE in female dogs.

Melatonin as a Potential Approach to Anxiety Treatment

Anxiety disorders are the most common mental diseases. Anxiety and the associated physical symptoms may disturb social and occupational life and increase the risk of somatic diseases. The pathophysiology of anxiety development is complex and involves alterations in stress hormone production, neurosignaling pathways or free radical production. The various manifestations of anxiety, its complex pathophysiological background and the side effects of available treatments underlie the quest for constantly seeking therapies for these conditions. Melatonin, an indolamine produced in the pineal gland and released into the blood on a nightly basis, has been demonstrated to exert anxiolytic action in animal experiments and different clinical conditions. This hormone influences a number of physiological actions either via specific melatonin receptors or by receptor-independent pleiotropic effects. The underlying pathomechanism of melatonin's benefit in anxiety may reside in its sympatholytic action, interaction with the renin-angiotensin and glucocorticoid systems, modulation of interneuronal signaling and its extraordinary antioxidant and radical scavenging nature. Of importance, the concentration of this indolamine is significantly higher in cerebrospinal fluid than in the blood. Thus, ensuring sufficient melatonin production by reducing light pollution, which suppresses melatonin levels, may represent an endogenous neuroprotective and anxiolytic treatment. Since melatonin is freely available, economically undemanding and has limited side effects, it may be considered an additional or alternative treatment for various conditions associated with anxiety.

Comparison of different sedatives in children before general anaesthesia for selective surgery: A network meta-analysis

WHAT IS KNOWN AND OBJECTIVE

It is estimated that 60% of children undergoing anaesthesia develop severe preoperative anxiety. The anxiety is associated with adverse reactions. Sedatives such as dexmedetomidine, midazolam, clonidine, ketamine, and melatonin can be used as premedication against preoperative anxiety. However, no consensus has been reached on the choice of pre-anaesthetic sedatives in children before selective surgery. Therefore, the current network meta-analysis (NMA) was carried out to evaluate different sedatives in children aged between 1 and 7 before general anaesthesia for selective surgery.

METHODS

Randomized clinical trials (RCTs) were retrieved from Pubmed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science databases from inception to October 22, 2021. Primary outcomes showed satisfactory sedation at parent separation and also at induction or mask acceptance. Secondary outcomes were those related to added benefits and side effects. The present NMA was conducted using the R software. Results of the study were reported as Relative Risk (RR) or Mean Difference (MD) at a 95% credible intervals (CrIs).

RESULTS AND DISCUSSION

A total of 48 trials were included in the present study. It was found that the effectiveness of dexmedetomidine, midazolam, clonidine, and ketamine were superior to that of placebo in satisfactory sedation at parent separation and induction or mask acceptance. There was no significant difference between melatonin and placebo in satisfactory sedation at induction or mask acceptance. Dexmedetomidine, ketamine, clonidine, and melatonin were superior to placebo in reducing emergence delirium (ED). In addition, midazolam prolonged the length of stay in the post anaesthesia care unit (PACU) as compared with placebo. Dexmedetomidine caused a significant reduction in systolic blood pressure (SBP) and heart rate (HR). Nevertheless, it was noted that the hemodynamic changes were roughly within safety limits.

WHAT IS NEW AND CONCLUSION

It was evident that the studied drugs can provide effective sedation with exception of melatonin and placebo. However, it was found that midazolam, ketamine, and clonidine lead to several side effects. The findings of the present study supported that dexmedetomidine, especially intranasal administration, has potential in the optimal selection of the sedatives for premedication in children. This is because the drug has effective sedation, reduced incidence of ED, side effects, and onset time.

The glutamate/GABA system in the retina of male rats: effects of aging, neurodegeneration, and supplementation with melatonin and antioxidant SkQ1

Glutamate and -aminobutyric acid (GABA) are the most abundant amino acids in the retina. An imbalance of the glutamate/GABA system is involved in the pathogenesis of various neurodegenerative disorders. Here we for the first time analyzed alterations of expression of glutamate- and GABA-synthesizing enzymes, transporters, and relevant receptors in the retina with age in Wistar rats and in senescence-accelerated OXYS rats who develop AMD-like retinopathy. We noted consistent age-dependent expression changes of GABAergic-system proteins (GAD67, GABA-T, and GAT1) in OXYS and Wistar rats: upregulation by age 3 months and downregulation at age 18 months. At a late stage of AMD-like retinopathy in OXYS rats (18 months), there was significant upregulation of glutaminase and downregulation of glutamine synthetase, possibly indicating an increasing level of glutamate in the retina. AMD-like-retinopathy development in the OXYS strain was accompanied by underexpression of glutamate transporter GLAST. Prolonged supplementation with both melatonin and SkQ1 (separately) suppressed the progression of the AMD-like pathology in OXYS rats without affecting the glutamate/GABA system but worsened the condition of the Wistar rat's retina during normal aging. We observed decreasing protein levels of glutamine synthetase, GLAST, and GABAAR1 and an increasing level of glutaminase in Wistar rats. In summary, both melatonin and mitochondrial antioxidant SkQ1 had different effect on the retinal glutamate / GABA in healthy Wistar and senescence-accelerated OXYS rats.

Effects of short-term administration of melatonin before gonadectomy on oxidative stress, cortisol and sex hormones in male dogs

The aim of this study was to investigate gonadectomy stress, steroid hormones and serotonin in male dogs treated with melatonin before gonadectomy. Twenty-five mixed breed adult dogs were divided into five equal groups. The melatonin and melatonin + gonadectomized groups received melatonin treatment (3 mg/10 Kg, PO, TID) the day before gonadectomy; the gonadectomized and anaesthesia groups did not receive melatonin; and the control group just received the melatonin vehicle. Blood sampling was performed before melatonin administration (day -1) and on days 0 (gonadectomy), 1, 3 and 6 after gonadectomy. Superoxide dismutase and glutathione peroxidase concentrations decreased significantly in gonadectomized dogs compared with dogs treated with melatonin before gonadectomy and intact dogs. Gonadectomy led to a significant decrease in catalase concentration in gonadectomized dogs compared with other study groups. Malondialdehyde levels increased significantly in gonadectomized dogs compared with other groups. Melatonin administration before gonadectomy led to decreased malondialdehyde concentration in gonadectomized and intact dogs compared to the control group. Cortisol concentration increased significantly in gonadectomized dogs compared to the control dogs. Serotonin levels decreased in gonadectomized dogs, but melatonin treatment increased serotonin concentration in gonadectomized and intact dogs. Melatonin treatment before gonadectomy suppressed oxidative stress and the cortisol but increased serotonin level.

Effects of exogenous melatonin on sleep quality and menopausal symptoms in menopausal women: a systematic review and meta-analysis of randomized controlled trials

IMPORTANCE

Because of the bothersome symptoms during women's menopausal period and the severe side effects of hormone therapy, it is meaningful to find new breakthroughs in improving menopausal women's quality of life.

OBJECTIVE

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating melatonin intake on the improvement of sleep quality, general menopausal symptom, mood states, as well as interaction of estradiol levels and body mass index (BMI) in menopausal women.

EVIDENCE REVIEW

We used the search terms "melatonin" together with "menopause" or "post-menopause" or "peri-menopause" in multiple databases online including PubMed, Web of Science, Embase, Clinical trial, Cochrane Library, and China National Knowledge Infrastructure from the first publication year to October 2020. Interesting data included characteristics of the study design, study participants, intervention, and outcome measures. Risk of biases in RCTs was evaluated with the Cochrane tool. Fixed-effect models and random-effect models were used for meta-analysis according to heterogeneity. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in our study.

FINDINGS

Eight cohorts (n = 812) evaluating the effects of melatonin in menopausal women were included. Melatonin was used in every study with differences existing in dose (1 mg - 5 mg) and duration (3 to 12 mo). Improved physical symptoms (standard mean difference [SMD] -0.376; 95% CI, -0.599 to -0.153, P = 0.001) merged in four RCTs. Melatonin treatment resulted in no benefits to sleep quality (SMD -0.659; 95% CI, -1.535 to 0.217, P = 0.141) and general menopause symptoms (SMD -0.625; 95% CI, -1.354 to 0.105, P = 0.093) in four and three RCTs, respectively. More specifically, melatonin did not solve the psychological (SMD -0.026; 95% CI, -0.372 to 0.321, P = 0.884, I2 = 70.3%), sexual (SMD -0.661; 95% CI, -1.416 to 0.093, P = 0.086) and vasomotor (SMD -0.256; 95% CI, -0.701 to 0.188, P = 0.258) issues. No significant changes were observed in anxiety (SMD 0.018; 95% CI, -0.519 to 0.556, P = 0.946), depression (SMD 0.133; 95% CI, -0.435 to 0.702, P = 0.646), BMI (weighted mean difference 0.029 kg/m2; 95% CI, -0.183 to 0.240, P = 0.790) or estradiol levels (weighted mean difference 0.016 pg/mL; 95% CI, -1.220 to 1.252, P = 0.980).

CONCLUSIONS

Melatonin seems to improve physical symptoms in menopausal women, but the general menopausal symptoms, sleep quality, mood state, estradiol levels, and BMI did not improve under melatonin intervention. However, multiple large-scale clinical randomized trials are needed to validate our conclusions.

[Effect of general anesthesia on postoperative melatonin secretion in 4-to 6-year-old children with snoring]

OBJECTIVE

To evaluate the effect of general anesthesia on postoperative melatonin secretion in 4-to 6-year-old children with snoring.

METHODS

Twenty children with snoring aged 4-6 years of either gender (ASA grade Ⅰ and Ⅱ) were selected for adenoidectomy.Before, during and 3 days after the operation, salivary melatonin levels of the children were measured at 11 selected time points (T1-T11).The illumination intensity and body temperature of the children were recorded at each time point of measurement.The sleep time of the children in 3 days after the operation was recorded, and postoperative pain scores (FLACC) and Riker and Rehabilitation Quality Rating Scale-15(QoR-15) scores were assessed.Sleep Apnea Life Quality Evaluation Questionnaire (OSA-18) was used to evaluate postoperative recovery of the children at 28 days after the operation.The incidence of major adverse events of the children during hospitalization was recorded.

RESULTS

No significant difference was found in baseline salivary melatonin level among the 20 children before the operation.Salivary melatonin level at 7 am after the operation (T8) was significantly lowered as compared with that before the surgery (T4)(P < 0.05) but recovered at 7 am on the second day after the surgery (T11);salivary melatonin levels at T4, T8, and T11 exceeded 3 pg/mL on the third day.No significant difference was found in illumination intensity or body temperature across the time points when melatonin level was measured.The children showed no significant changes in FLACC score, Riker score or QOR- 15 score after the operation, but the OSA-18 score was significantly lowered after the operation (P < 0.05).None of the 20 children had such adverse events as respiratory depression, sinus bradycardia, sinus tachycardia, hypertension, hypotension, nausea or vomiting during hospitalization.

CONCLUSIONS

In preschool children with snoring, general anesthesia affects but does not inhibit melatonin secretion on the first night after surgery, and minor surgeries under general anesthesia in the morning do not cause significant changes in melatonin secretion to cause disturbance of the circadian rhythm in these children.

The Role of Perioperative Sleep Disturbance in Postoperative Neurocognitive Disorders

Postoperative neurocognitive disorder (PND) increases the length of hospital stay, mortality, and risk of long-term cognitive impairment. Perioperative sleep disturbance is prevalent and commonly ignored and may increase the risk of PND. However, the role of perioperative sleep disturbances in PND remains unclear. Nocturnal sleep plays an indispensable role in learning, memory, and maintenance of cerebral microenvironmental homeostasis. Hospitalized sleep disturbances also increase the incidence of postoperative delirium and cognitive dysfunction. This review summarizes the role of perioperative sleep disturbances in PND and elucidates the potential mechanisms underlying sleep-deprivation-mediated PND. Activated neuroinflammation and oxidative stress; impaired function of the blood-brain barrier and glymphatic pathway; decreased hippocampal brain-derived neurotrophic factor, adult neurogenesis, and sirtuin1 expression; and accumulated amyloid-beta proteins are associated with PND in individuals with perioperative sleep disorders. These findings suggest that the improvement of perioperative sleep might reduce the incidence of postoperative delirium and postoperative cognitive dysfunction. Future studies should further investigate the role of perioperative sleep disturbance in PND.

Melatonin for preoperative and postoperative anxiety in adults

BACKGROUND

Anxiety in relation to surgery is a well-known problem. Melatonin offers an alternative treatment to benzodiazepines for ameliorating this condition in the preoperative and postoperative periods.

OBJECTIVES

To assess the effects of melatonin on preoperative and postoperative anxiety compared to placebo or benzodiazepines.

SEARCH METHODS

We searched the following databases on 10 July 2020: CENTRAL, MEDLINE, Embase, CINAHL, and Web of Science. For ongoing trials and protocols, we searched clinicaltrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform.

SELECTION CRITERIA

We included randomized, placebo-controlled or standard treatment-controlled (or both) studies that evaluated the effects of preoperatively administered melatonin on preoperative or postoperative anxiety. We included adult patients of both sexes (15 to 90 years of age) undergoing any kind of surgical procedure for which it was necessary to use general, regional, or topical anaesthesia.

DATA COLLECTION AND ANALYSIS

One review author conducted data extraction in duplicate. Data extracted included information about study design, country of origin, number of participants and demographic details, type of surgery, type of anaesthesia, intervention and dosing regimens, preoperative anxiety outcome measures, and postoperative anxiety outcome measures.

MAIN RESULTS

We included 27 randomized controlled trials (RCTs), involving 2319 participants, that assessed melatonin for treating preoperative anxiety, postoperative anxiety, or both. Twenty-four studies compared melatonin with placebo. Eleven studies compared melatonin to a benzodiazepine (seven studies with midazolam, three studies with alprazolam, and one study with oxazepam). Other comparators in a small number of studies were gabapentin, clonidine, and pregabalin. No studies were judged to be at low risk of bias for all domains. Most studies were judged to be at unclear risk of bias overall. Eight studies were judged to be at high risk of bias in one or more domain, and thus, to be at high risk of bias overall. Melatonin versus placebo Melatonin probably results in a reduction in preoperative anxiety measured by a visual analogue scale (VAS, 0 to 100 mm) compared to placebo (mean difference (MD) -11.69, 95% confidence interval (CI) -13.80 to -9.59; 18 studies, 1264 participants; moderate-certainty evidence), based on a meta-analysis of 18 studies. Melatonin may reduce immediate postoperative anxiety measured on a 0 to 100 mm VAS compared to placebo (MD -5.04, 95% CI -9.52 to -0.55; 7 studies, 524 participants; low-certainty evidence), and may reduce delayed postoperative anxiety measured six hours after surgery using the State-Trait Anxiety Inventory (STAI) (MD -5.31, 95% CI -8.78 to -1.84; 2 studies; 73 participants; low-certainty evidence). Melatonin versus benzodiazepines (midazolam and alprazolam) Melatonin probably results in little or no difference in preoperative anxiety measured on a 0 to 100 mm VAS (MD 0.78, 95% CI -2.02 to 3.58; 7 studies, 409 participants; moderate-certainty evidence) and there may be little or no difference in immediate postoperative anxiety (MD -2.12, 95% CI -4.61 to 0.36; 3 studies, 176 participants; low-certainty evidence). Adverse events Fourteen studies did not report on adverse events. Six studies specifically reported that no side effects were observed, and the remaining seven studies reported cases of nausea, sleepiness, dizziness, and headache; however, no serious adverse events were reported. Eleven studies measured psychomotor and cognitive function, or both, and in general, these studies found that benzodiazepines impaired psychomotor and cognitive function more than placebo and melatonin. Fourteen studies evaluated sedation and generally found that benzodiazepine caused the highest degree of sedation, but melatonin also showed sedative properties compared to placebo. Several studies did not report on adverse events; therefore, it is not possible to conclude with certainty, from the data on adverse effects collected in this review, that melatonin is better tolerated than benzodiazepines.

AUTHORS' CONCLUSIONS

When compared with placebo, melatonin given as premedication (as tablets or sublingually) probably reduces preoperative anxiety in adults (measured 50 to 120 minutes after administration), which is potentially clinically relevant. The effect of melatonin on postoperative anxiety compared to placebo (measured in the recovery room and six hours after surgery) was also evident but was much smaller, and the clinical relevance of this finding is uncertain. There was little or no difference in anxiety when melatonin was compared with benzodiazepines. Thus, melatonin may have a similar effect to benzodiazepines in reducing preoperative and postoperative anxiety in adults.

Desflurane anesthesia shifts the circadian rhythm phase depending on the time of day of anesthesia

Desflurane is one of the most frequently used inhalational anesthetics in clinical practice. A circadian rhythm phase-shift after general anesthesia with sevoflurane or isoflurane has been reported in mice, but few studies have reported this effect with desflurane. In the present study, we examined the rest/activity rhythm of mice by counting the number of running wheel rotations, and we found that desflurane anesthesia caused a phase shift in the circadian rhythm that was dependent on the time of day of anesthesia. We also found that desflurane anesthesia altered the relative mRNA expression of four major clock genes (Per2, Bmal, Clock, and Cry1) in the suprachiasmatic nucleus (SCN). These results are important for elucidating the effects of desflurane on the SCN, which is the master clock for the mammalian circadian rhythm. Further studies on the relationship between anesthesia and circadian rhythm may lead to the prevention and treatment of postoperative complications related to circadian rhythms.

Melatonin for anaesthetic indications in paediatric patients: a systematic review

The favourable safety profile and ubiquitous nature of melatonin has led to an increase in its use in various clinical settings in adults and children. We performed a systematic review of published studies on the use of melatonin for anaesthetic indications in paediatric patients. To identify relevant articles, PubMed, EMBASE, Cumulative Index to Nursing and Allied Health Literature, Web of Science and Scopus databases were searched. Study title and abstract screening, and full text review were performed by two reviewers. Twenty-seven eligible studies investigating melatonin use for anaesthetic indications were identified. Due to significant heterogeneity in study methodology, a quantitative synthesis of the published findings was not possible. The identified studies were therefore categorised by the indication for melatonin: analgesia, diagnostic sedation and as an anaesthetic adjunct. Melatonin use for anaesthetic-related indications is safe; may provide analgesia for inflammatory-associated pain in neonates and children before venepuncture; may decrease the need for, or replace, general anaesthesia for diagnostic procedures; and may serve as an anaesthesia adjunct before induction in paediatric patients.

Comparative evaluation of oral melatonin and oral clonidine for the attenuation of haemodynamic response to laryngoscopy and tracheal intubation-A prospective randomised double blind study

BACKGROUND AND AIMS

Laryngoscopy and endotracheal intubation cause significant derangement of the haemodynamic parameters proving detrimental for some patients. Clonidine, an α-2 adrenoreceptor agonist, and melatonin, the pineal hormone, have been used for the attenuation of these haemodynamic responses. This study was designed to evaluate the effect of oral melatonin and clonidine in attenuating the haemodynamic responses to laryngoscopy and intubation.

MATERIALS AND METHODS

In this prospective randomised double-blind study, 60 American Society of Anaesthesiologists (ASA) grade I and II patients aged 20-60 years of either gender scheduled to undergo elective surgery under general anaesthesia were randomly divided into Group M and Group C and orally received 6 mg of melatonin and 0.2 mg of clonidine, respectively, 120 min before the induction of anaesthesia. The haemodynamic parameters-heart rate (HR), systolic blood pressure, diastolic blood pressure, mean arterial pressure and rate -pressure product(RPP) were recorded before and 120 min after the administration of the study drug, before induction, immediately after intubation and at 1, 3, 5 and 10 min following intubation. Sedation was assessed using the Ramsay Sedation Scale. The qualitative and quantitative variables were analysed using Chi square test and unpaired student t test, respectively. For intragroup comparison of quantitative data, paired t test was applied. A P value <0.05 was considered as statistically significant.

RESULTS

A significant difference was noted between the groups regarding HR and RPP 0, 1, 3 and 5 min after intubation. The Ramsay sedation score ranged between 2 and 3 at all time intervals.

CONCLUSION

Although both the drugs are effective, oral melatonin proved superior to oral clonidine in attenuating the haemodynamic response to laryngoscopy and tracheal intubation without any side effects.

A Comparative Evaluation of Oral Clonidine, Dexmedetomidine, and Melatonin As Premedicants in Pediatric Patients Undergoing Subumbilical Surgeries

INTRODUCTION

Sedative premedication is the mainstay of pharmacological therapy in children undergoing surgeries. This study compares preoperative melatonin, clonidine, and dexmedetomidine on sedation, ease of anesthesia induction, emergence delirium, and analgesia.

MATERIALS AND METHODS

One hundred and five children, 3-8 years, either sex, ASA I/II, posted for infraumbilical surgery, randomized to receive clonidine 5 mcg/kg (Group C), dexmedetomidine 3 mcg/kg (Group D), and melatonin 0.2 mg/kg (Group M) 45 minutes before surgery. Preoperative Sedation/Anxiety and Child-Parent Separation Score (CPSS) were assessed. Identical anesthesia technique was utilized. Emergence delirium (Watcha score) and postoperative pain (Objective Pain Scale score) were monitored postoperatively.

RESULTS

Patients were demographically comparable. Sedation score >Grade 3 was absent. Grades 1/2/3 were present in 10/19/6 (Group C), 2/26/7 (Group D), and 7/26/2 (Group M). Grade 1 CPSS was present in 42.6% (Group C), 37.1% (Group D), and 28.6% (Group M). Pediatric Anesthesia Behavior Score (PABS) was comparable between Groups C and D (p = 0.224; 95% CI -0.090 to 0.604) and Groups C and M (p = 0.144; 95% CI -0.633 to 0.061) while PABS was better in Group D compared to Group M (p = 0.0007; 95% CI -0.890 to -0.195). Watcha scores were 33/2/0/0 (Group C), 34/1/0/0 (Group D), and 32/2/1/0 (Group M) immediately after extubation. Scores were 31/4/0/0 (Group C), 33/2/0/0 (Group D), and 31/4/0/0 (Group M) at 30 minutes and 28/7/0/0 (Group C), 29/6/0/0 (Group D), and 24/11/0/0 (Group M) at 1 hour. The scores were comparable (p > 0.05). Objective Pain Scale scores were comparable between Groups C and D and Groups C and M (p > 0.05). Lower scores were present in Group D compared to M (p = 0.023).

CONCLUSION

Melatonin, clonidine, and dexmedetomidine are efficacious for producing preoperative sedation, reducing anxiety, postoperative pain, and emergence delirium.

Comparison of Morning and Evening Operation Under General Anesthesia on Intraoperative Anesthetic Requirement, Postoperative Sleep Quality, and Pain: A Randomized Controlled Trial

OBJECTIVE

Postoperative sleep disorders can cause serious adverse effects on postoperative outcomes. The purpose of our study was to compare the effects of the timing of surgery under general anesthesia on intraoperative anesthetic drug requirements, postoperative sleep quality and pain in patients.

MATERIALS AND METHODS

Eighty-four patients who underwent selective laparoscopic abdominal surgeries under general anesthesia were randomly assigned to the Day Group (8:00-12:00) or the Night Group (18:00-22:00). The portable sleep monitor (PSM) was used to determine sleep quality on the night before surgery (Sleep-preop), the first night after surgery (Sleep POD 1), and the third night after surgery (Sleep POD 3). The visual analog scale (VAS) was used to evaluate postoperative pain scores and the Athens Insomnia Scale (AIS) was used for assessing insomnia symptoms. The total dose of general anesthetics required and adverse effects after surgery were also assessed.

RESULTS

Compared to Sleep-preop, patients presented with a lower sleep efficiency and a higher AIS score during Sleep POD 1 and Sleep POD 3. Furthermore, the Night Group had a significantly lower proportion of rapid eye movement sleep, stable sleep, and unstable sleep than did the Day Group at Sleep POD 1 and Sleep POD 3. The dosage of propofol and remifentanil required in the Day Group was significantly higher than that in the Night Group. Furthermore, patients in the Day Group had better pain relief, with a lower VAS score at 1, 6, 12, and 24 hours after surgery. The incidences of postoperative nausea and vomiting and dizziness were significantly higher in the Night Group than those in the Day Group.

CONCLUSION

Morning operations required a higher dose of anesthetic drugs than did evening operations, which may be related to the circadian rhythm. The degree of postoperative sleep disorders was greater when the operation was performed in the evening than in the morning, which was also associated with increased pain perception and increased incidence of postoperative adverse effects. Thus, our results suggest that patients with hyperalgesia and sleep disorders may benefit from operations performed in the morning.

The Effect of Melatonin on Anxiety and Pain of Tourniquet in Intravenous Regional Anesthesia

Background:

Melatonin has anxiolytic and potential analgesic effects. Several studies have indicated the sedative and anti-anxiety effects of melatonin when used as premedication before surgery. Hence, we assessed the efficacy of melatonin premedication in tourniquet-related pain and analgesia in patients receiving intravenous regional anesthesia (IVRA).

Materials and Methods:

Fifty patients undergoing elective hand surgery under IVRA were randomly divided into two groups (25 patients each) to receive either melatonin 6 mg (melatonin group) or placebo (control group) as oral premedication. IVRA was achieved with lidocaine, 3 mg/kg, diluted with saline to a total volume of 40 mL. Anxiety scores, sensory and motor block onset and recovery times, tourniquet pain, and 24-h analgesic requirements were recorded.

Results:

The onset of motor and sensory block was statistically significantly shorter in Group M (P < 0.001), and recovery of motor and sensory block was statistically significantly longer in Group M (P < 0.001). The time of starting tourniquet pain was longer in Group M (P < 0.001). The mean anxiety score in the study group was 3 ± 0.81 and in the control group was 4.20 ± 1.04 (P = 0.001). There was a statistically significant difference in the need for opioids between the two groups (P < 0.05).

Conclusions:

Melatonin is an effective premedication before IVRA because it reduces patient anxiety, decreases tourniquet-related pain, and improves perioperative analgesia.

Preoperative calming effect of melatonin and its influence on propofol dose for anesthesia induction in healthy dogs

OBJECTIVE

To investigate the preoperative calming effect of melatonin and its influence on propofol dose for anesthesia induction in dogs.

STUDY DESIGN

Prospective, randomized, blinded, placebo-controlled clinical study.

ANIMALS

A total of 50 healthy, adult, client-owned dogs scheduled for elective surgery.

METHODS

Dogs were equally divided into treatment group M, which received 5 mg kg^-1 melatonin, and placebo-control group P (sucrose), both administered orally 2 hours prior to induction of anesthesia. Dogs were subjectively characterized and further designated as skeptical (group S; n = 18) or trustful (group T; n = 32). Behavior, calming effect and vital parameters (pulse rate, respiratory rate, blood pressure, rectal temperature) were evaluated before and after treatment. Propofol dose [mg kg^-1 intravenously (IV)] to allow endotracheal intubation and anesthesia induction quality was documented. Data were analyzed using a general linear model and Mann-Whitney U tests.

RESULTS

Dogs in group MS (n = 10) were calmer than those in group PS (n = 8) at 90 minutes after drug administration (p = 0.047). Group MT (n = 15) required less propofol (5.98 ± 0.96 mg kg^-1) than group PT (n = 17; 7.04 ± 1.82 mg kg^-1 IV; p = 0.048) and group MS (9.48 ± 3.22 mg kg^-1 IV; p = 0.007). Group PS required 7.69 ± 2.71 mg kg^-1 IV. Skeptical dogs showed more reactions during induction (p = 0.013). Vital parameters were within physiological ranges before and after treatment.

CONCLUSION AND CLINICAL RELEVANCE

Results showed that melatonin may be used to reduce propofol dose for anesthesia induction in trustful dogs. Skeptical dogs benefitted from the calming properties. Potentially, melatonin could be used to minimize the level of excitement before general anesthesia and to reduce the required propofol dose for induction.

Transmucosal delivery of melatonin-encapsulated niosomes in a mucoadhesive gel

AIM

A transmucosal niosome gel was developed to improve the pharmacokinetics of exogenous melatonin.

MATERIALS & METHODS

The melatonin niosomes (MN) gel was characterized and melatonin levels were determined in healthy volunteers.

RESULTS

Micron-sized MN in a gel, mean ex vivo residence time of more than 3 h with maximum adhesiveness at 25 and 37°C showed similar in vitro release but different in vitro permeation to melatonin gel. Oral transmucosal MN gels, at 2.5, 5 and 10 mg, topically applied in 14 healthy volunteers in a randomized double-blinded crossover design with 7-day washout, gave dose-proportional pharmacokinetics, with improved absorption and prolonged systemic circulation.

CONCLUSION

The transmucosal MN gel provides a topical option for melatonin administration with substantial prolonged systemic delivery.

Comparison of the anesthetic effects of 2,2,2-tribromoethanol on ICR mice derived from three different sources

This study was conducted to compare the anesthetic effects of 2,2,2-tribromoethanol (TBE, Avertin®) in ICR mice obtained from three different sources. TBE (2.5%) was intraperitoneally injected at three doses: high-dose group (500 mg/kg), intermediate-dose group (250 mg/kg), and low-dose group (125 mg/kg). Anesthesia time, recovery time, end-tidal peak CO₂ (ETCO₂), mean arterial blood pressure, heart rate, oxygen saturation (SpO₂), body temperature, pH, PCO₂, and PO₂ of the arterial blood were measured. Stable anesthesia was induced by all doses of TBE and the anesthesia time was maintained exhibited dose dependency. No significant differences in anesthetic duration were found among the three different strains. However, the anesthesia time was longer in female than in male mice, and the duration of anesthesia was significantly longer in female than in male mice in the high-dose group. The recovery time was significantly longer for female than male mice in the intermediate- and high-dose groups. In the ICR strains tested, there were no significant differences in the mean arterial blood pressure, SPO₂, arterial blood PCO₂, and PO₂, which decreased after TBE anesthesia, or in heart rate and ETCO₂, which increased after TBE anesthesia. In addition, body temperature, blood biochemical markers, and histopathological changes of the liver, kidney, and lung were not significantly changed by TBE anesthesia. These results suggested that ICR mice from different sources exhibited similar overall responses to a single exposure to TBE anesthesia. In conclusion, TBE is a useful drug that can induce similar anesthetic effects in three different strains of ICR mice.

The Timing of Melatonin Administration Is Crucial for Its Antidepressant-Like Effect in Mice

Melatonin is synthesized by the pineal gland with a circadian rhythm in synchrony with the environmental light/dark cycle. A gradual increase in circulating levels of melatonin occur after lights off, reaching its maximum around the middle of the dark phase. Agonists of melatonin receptors have proved effectiveness as antidepressants in clinical trials. However, there is contradictory evidence about the potential antidepressant effect of melatonin itself. Herein we studied melatonin administration in mice at two zeitgeber times (ZT; ZT = 0 lights on; 12:12 L/D), one hour before the beginning (ZT11) and at the middle (ZT18) of the dark phase after either a single or a three-dose protocol. Behavioral despair was assessed through a forced-swimming test (FST) or a tail suspension test (TST), at ZT18.5. A single dose of 4 mg/kg melatonin at ZT11 was effective to reduce the immobility time in both tests. However, acute administration of melatonin at ZT18 was not effective in mice subjected to FST, and a higher dose (16 mg/kg) was required to reduce immobility time in the TST. A three-dose administration protocol of 16 mg/kg melatonin (ZT18, ZT11, and ZT18) significantly reduced immobility time in FST. Data indicate that the timely administration of melatonin could improve its antidepressant-like effect.

Comparison of Effects of Oral Melatonin with Oral Alprazolam used as a Premedicant in Adult Patients Undergoing Various Surgical Procedures under General Anesthesia: A Prospective Randomized Placebo-Controlled Study

BACKGROUND AND AIMS

Preoperative anxiety is a major concern in patients undergoing any surgical procedure. Various drugs have been used to alleviate it. This study aims to compare the effects of oral melatonin versus oral alprazolam on preoperative anxiety, sedation, orientation, and cognitive function.

MATERIALS AND METHODS

A total of 90 adult patients were randomly allocated into three groups. Group M (n = 30) received oral melatonin 3 mg (2 tablets); Group A (n = 30) received oral alprazolam 0.25 mg (2 tablets), and Group P (n = 30) received placebo, multivitamin tablet (2 tablets) as premedication. The objectives of our study were to compare anxiety, sedation, orientation, and cognitive function using visual analog scale (VAS) anxiety score, Ramsay Sedation Score (RSS), orientation score, and Digit symbol substitution test (DSST) score before and after 120 min of giving premedication. For statistical analysis, paired t-test, Chi-square test, analysis of variance, and post hoc bonferroni test were used.

RESULTS

Mean VAS scores for anxiety (after 120 min) were significantly reduced in Group M (3.9 ± 1.53) and Group A (4.43 ± 1.67) when compared to Group P (4.73 ± 0.82) (P < 0.05). RSS was higher in Group A as compared to Group M and Group P (P < 0.05). No significant difference in orientation score was observed in all the three groups before and after premedication (P > 0.05). DSST score (cognitive function) was better in Group M when compared to both Group A and Group P (P < 0.05).

CONCLUSION

Oral melatonin (6 mg) when used as a premedicant is an effective alternative to alprazolam regarding providing better anxiolysis, lesser sedation along with maintenance of cognitive, and psychomotor function.

Melatonin premedication versus placebo in wisdom teeth extraction: a randomised controlled trial

INTRODUCTION

Pain after wisdom teeth surgery can be moderate in severity and is compounded by preoperative anxiety in young patients. We studied the effect of melatonin premedication on postoperative pain and preoperative anxiety in patients undergoing wisdom teeth extractions.

METHODS

This randomised controlled trial recruited 76 patients at Khoo Teck Puat Hospital who were American Society of Anesthesiologists physical status I and II, aged 21 to 65 and scheduled to undergo elective extraction of all four wisdom teeth under general anaesthesia. Patients with a history of long-term use or allergy to melatonin were excluded. The patients received either 6 mg melatonin or a placebo 90 minutes before surgery. Visual analogue scale (VAS) scores at multiple time intervals for postoperative pain and preoperative anxiety, patient satisfaction and first-night sleep quality scores were obtained. Mixed-effects regression models were used for longitudinal analysis of VAS pain, anxiety and satisfaction scores.

RESULTS

Maximum VAS scores for pain and anxiety were 18.6 ± 19.1 mm at 60 minutes postoperatively and 26.2 ± 23.4 mm at 90 minutes preoperatively, respectively. After adjusting for gender, female patients who received melatonin had a faster rate of reduction of VAS pain (p = 0.020) and anxiety scores (p = 0.003) over time compared to the placebo group. No such effect was demonstrated in male patients. There was no significant difference in sleep quality or satisfaction scores.

CONCLUSION

Melatonin use did not consistently contribute to pain and anxiety amelioration in all patients. Our study demonstrated a positive effect in female patients, suggestive of sexual dimorphism.

Comparing the Effect of Preoperative Administration of Melatonin and Passiflora incarnata on Postoperative Cognitive Disorders in Adult Patients Undergoing Elective Surgery

Background

Anxiety is a preoperative complication, which most patients encounter. The use of a premedication to reduce preoperative anxiety with minimal cognitive impairment is crucial.

Objectives

This study was conducted to compare the sedative effect of preoperative melatonin and Passiflora incarnata in patients undergoing elective surgery regarding their potential for postoperative cognitive disorders.

Methods

In this clinical trial, 52 patients American society of anesthesiologists grade (ASA) I and II of both genders were selected to receive either Passiflora incarnata (1000 mg nature made) (n = 26) or melatonin (6 mg) (n = 26) as premedication one hour before surgery. Post-operative pain was evaluated using the visual analogue scale (VAS). Patient’s anxiety and cognitive dysfunction was evaluated with the Ramsey score and the digital symbol substitution test (DSST), respectively. All tests were carried out and evaluated at arrival in the operating room, before induction and before discharge from the post anesthesia care unit (PACU).

Results

There were no statistically differences between groups in VAS (P > 0.05). However, the mean score of pain was higher in the melatonin group compared to the Pssiflora incarnata group when discharged from the PACU (27.63 vs. 25.37). The anxiety scores were statistically significant in both drugs (P = 0.001), however higher sedation scores was caused by premedication with melatonin (P = 0.003 vs. 0.008). Regarding the DSST, there was a significant difference between the two groups one hour before the surgery (P = 0.04) and at the time of discharge from the PACU (P = 0.007). When evaluating each group, the Passiflora incarnata group revealed a significant difference (P = 0.003).

Conclusions

Our findings show that premedication with Passiflora incarnata reduces anxiety as well as Melatonin. However, Melatonin causes less cognitive impairment compared to Passiflora incarnata.

The Efficacy of Oral Melatonin in Improving Sleep in Cancer Patients with Insomnia: A Randomized Double-Blind Placebo-Controlled Study

Background:

The natural hormone melatonin has sleep inducing properties. Insomnia in cancer patients is common. So far, melatonin has been seldom tried for the improvement of sleep in patients with malignancies. Keeping this in mind, we planned and conducted a double-blind study to test the efficacy of melatonin in promoting sleep in patients with malignancies suffering from insomnia.

Objective:

To assess the hypnotic efficacy of oral melatonin in cancer patients with insomnia.

Materials and Methods:

After Ethical Committee approval, 50 patients (age range 20-65 years) from our pain clinic NIVARANE who met the Diagnostic and Statistical Manual of Mental Disorders 4^th edition criteria for primary insomnia were randomized to receive melatonin 3 mg or placebo at 7 pm orally every day for 14 days from our pharmacist. After 1, 7, 14 days, the patients were reviewed with the Athens insomnia scale oral questionnaire to document the subjective sleep quality. The patients and we, the investigators were blinded to the study drug.

Results:

There were 2 drop outs (one from each group) as they failed to complete visit on day 14. Significant differences in favor of melatonin treatment were found in clinically relevant improvements in insomnia (46.53%; P = 0.00001 vs. 11.30%; P = 0.1026) There was improvement in sleep from 1 to 7 days (19.91%; P = 0.00001 vs. 0.98%; P = 0.2563). More significant improvements were seen between 7 and 14 days (33.24%; P = 0.00001 vs. 10.42%; P = 0.1469).

Conclusion:

We conclude that daily intake of oral melatonin 2 h before bedtime improves sleep induction and quality in cancer patients with insomnia.

Effect of Day and Night Desflurane Anaesthesia on Melatonin Levels in Rats

OBJECTIVE

The aim of this study is to investigate the effect of day and night administration of desflurane anaesthesia on melatonin levels in rats.

METHODS

Twenty-four 15-day-old rats were included in the study and were divided into four groups. The rats were anaesthetised between 19:00-01:00 (night group) and 07:00-13:00 (day group) with 5.7% desflurane concentration in 6 L min^-1 100% oxygen. 6 L min^-1 oxygen was administered to the control groups. At the end of 6 h of anaesthesia, blood samples were taken, and rats were sacrificed. Blood samples were centrifuged and melatonin levels from plasma samples were measured with radioimmunoassay.

RESULTS

There was a statistically significant difference between the groups (p=0.007). Between group day control and group night control there was a statistically significant difference (p=0.042). Further, there was a significant difference between group day control and night desfluran as well (p=0.024). We could not find any difference between other groups.

CONCLUSION

This study showed that 6 hours of 5.7% desflurane anaesthesia during day and night hours did not significantly change melatonin levels.

Effect of day/night administration of three different inhalational anesthetics on melatonin levels in rats

The nocturnal peak of melatonin can be altered after anesthesia and surgery. We aimed to examine the melatonin levels during the day and night after anesthesia with three commonly used inhalational anesthetics. Forty-eight male Wistar albino rats were randomized into eight groups. Rats were administered anesthesia between 7:00 am and 1:00 pm (day groups) or 7:00 pm and 1:00 am (night groups) for 6 hours. At the end of the anesthesia, blood samples were collected for assessing melatonin levels. Mean values of melatonin levels after 6 hours of anesthesia during daytime were 43.17±12.95 for control, 59.79±27.83 for isoflurane, 50.75±34.28 for sevoflurane and 212.20±49.56 pg/mL for desflurane groups. The night groups' mean melatonin levels were 136.12±33.20 for control, 139.85±56.29 for isoflurane, 117.48±82.39 for sevoflurane and 128.70±44.63 pg/mL for desflurane groups. Desflurane anesthesia between 7:00 am and 1:00 pm significantly increased melatonin levels (p<0.001). Sevoflurane and desflurane anesthesia between 7:00 pm and 1:00 am decreased the melatonin levels but there were no significant differences (p=0.904 and p>0.99, respectively). Isoflurane anesthesia did not significantly change melatonin levels during day or night (p=0.718 and p>0.99, respectively). Our results demonstrate that during daytime desflurane anesthesia can alter melatonin levels. Altered melatonin rhythm following inhalational anesthesia can be related to sleep disorders observed after anesthesia.

Melatonin versus midazolam premedication in children undergoing surgery: A pilot study

AIM

Melatonin has been proposed as a premedication alternative to midazolam, preceding anaesthesia induction. However, to our knowledge, data concerning interaction between melatonin and intravenous anaesthetic drugs in children are not available. The aim of this prospective, randomized, double-blind pilot study was to investigate the possible effect of melatonin premedication, in comparison to midazolam, on the required infusion of propofol in children undergoing surgery. As a secondary outcome, the effect of oral melatonin on the preoperative sedation level and on the post anaesthesia recovery score was evaluated.

METHODS

Children between the age of 5 and 14 years, scheduled for elective surgery, were prospectively enrolled between January 2012 and December 2013, and randomly assigned to two groups based on whether they received oral melatonin (0.5 mg/kg) or oral midazolam (0.5 mg/kg) premedication before induction of anaesthesia with propofol. Degree of sedation before and after anaesthesia was also evaluated.

RESULTS

Ninety-two patients were studied, 46 for each group. We found that oral administration of melatonin significantly reduced doses of propofol required for induction of anaesthesia in paediatric patients, more than midazolam (P < 0.001). No statistically significant differences were found in the pre- and post-anaesthesia sedation score (P = 0.387 and P = 0.525, respectively) between the two groups.

CONCLUSIONS

The present study demonstrates that melatonin enhances the potency of propofol also in paediatric patients. Moreover, considering the paediatric level of sedation, melatonin was equally as effective as midazolam. These data support the use of melatonin as a premedicant in paediatric surgical patients.

Use of melatonin in oral health and as dental premedication

Anxiety is a common problem in dentistry which could affect the correct treatment and involve failure. Oral premedication is needed to treat several anxious patients. Many people are so highly anxious that oral sedation is not effective and need to be under deep sedation or even general anaesthesia in order to receive dental care. In these patients, due to a high level of anxiety, even the insertion of an intravenous catheter can be difficult. Benzodiazepines have been the most commonly used anxiolytic in these cases, but many may be associated with paradoxical reactions. Melatonin has a good potential to be used in this field as alternative to benzodiazepines because it may induce a natural sleepiness and improve sedation. The purpose of this paper was to summarize what is known about the use of melatonin in oral health and as dental premedication in anxious dental patients. Databases were searched for the relevant published literature to 30 April 2015. The following search items were used in various combinations: melatonin, premedication, anxiety, dental, sedation and anaesthesia. Few articles were found about this aspect, and the use of melatonin is still a controversial aspect in dental field. More detailed/specific studies are necessary to extend the therapeutic possibilities of melatonin as premedication in dentistry.

The potential role of melatonin on sleep deprivation-induced cognitive impairments: implication of FMRP on cognitive function

While prolonged sleep deprivation (SD) could lead to profound negative health consequences, such as impairments in vital biological functions of immunity and cognition, melatonin possesses powerful ameliorating effects against those harmful insults. Melatonin has strong antioxidant and anti-inflammatory effects that help to restore body's immune and cognitive functions. In this study, we investigated the possible role of melatonin in reversing cognitive dysfunction induced by SD in rats. Our experimental results revealed that sleep-deprived animals exhibited spatial memory impairment in the Morris water maze tasks compared with the control groups. Furthermore, there was an increased glial activation most prominent in the hippocampal region of the SD group compared to the normal control (NC) group. Additionally, markers of oxidative stress such as 4-hydroxynonenal (4-HNE) and 7,8-dihydro-8-oxo-deoxyguanine (8-oxo-dG) were significantly increased, while fragile X-mental retardation protein (FMRP) expression was decreased in the SD group. Interestingly, melatonin treatment normalized these events to control levels following SD. Our data demonstrate that SD induces oxidative stress through glial activation and decreases FMRP expression in the neurons. Furthermore, our results suggest the efficacy of melatonin for the treatment of sleep-related neuronal dysfunction, which occurs in neurological disorders such as Alzheimer's disease and autism.

Melatonin for pre- and postoperative anxiety in adults

BACKGROUND

Anxiety in relation to surgery is a well-known problem. Melatonin offers an atoxic alternative to benzodiazepines in ameliorating this condition in the pre- and postoperative period.

OBJECTIVES

To assess the effect of melatonin on pre- and postoperative anxiety in adults when comparing melatonin with placebo or when comparing melatonin with benzodiazepines.

SEARCH METHODS

The following databases were searched on 19 April 2013: CENTRAL, MEDLINE, EMBASE, CINAHL and Web of Science. For ongoing trials and protocols we searched clinicaltrials.gov, Current Controlled Trials and the World Health Organization (WHO) International Clinical Trials Registry Platform. We reran the search in October 2014. We will deal with any studies of interest when we update the review.

SELECTION CRITERIA

Randomized, placebo-controlled or standard treatment-controlled, or both, studies that evaluated the effect of preoperatively administered melatonin on preoperative or postoperative anxiety. We included adult patients of both genders (15 to 90 years of age) undergoing any kind of surgical procedure in which it was necessary to use general, regional or topical anaesthesia.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two review authors. Data extracted included information about study design, country of origin, number of participants and demographic details, type of surgery, type of anaesthesia, intervention and dosing regimen, preoperative anxiety outcome measures and postoperative anxiety outcome measures.

MAIN RESULTS

This systematic review identified 12 randomized controlled trials (RCTs) including 774 patients that assessed melatonin for treating preoperative anxiety, postoperative anxiety or both. Four of the 12 studies compared melatonin, placebo and midazolam, whereas the remaining eight studies compared melatonin and placebo only.The quality of the evidence for our primary outcome (melatonin versus placebo for preoperative anxiety) was high. More than half of the included studies had a low risk of selection bias and at least 75% of the included studies had a low risk of attrition, performance and detection bias. Most of the included studies had an unclear risk of reporting bias.Eight out the 10 studies that assessed the effect of melatonin on preoperative anxiety using a visual analogue scale (VAS) (ranging from 0 to 100 mm, higher scores indicate greater anxiety) showed a reduction compared to placebo. The reported estimate of effect (relative effect -13.36, 95% confidence interval (CI) -16.13 to -10.58; high quality evidence) was based on a meta-analysis of seven studies. Two studies did not show any difference between melatonin and placebo. Two studies comparing melatonin with midazolam using a VAS found no evidence of a difference in preoperative anxiety between the two groups (relative effect -1.18, 95% CI -2.59 to 0.23; low quality evidence).Eight studies assessed the effect of melatonin on postoperative anxiety. Four of these studies measuring postoperative anxiety 90 minutes postoperatively using a VAS did not find any evidence of a difference between melatonin and placebo (relative effect -3.71, 95% CI -9.26 to 1.84). Conversely, two studies showed a reduction of postoperative anxiety measured six hours after surgery using the State-Trait Anxiety Inventory (STAI) when comparing melatonin with placebo (relative effect -5.31, 95% CI -8.78 to -1.84; moderate quality evidence). Two studies comparing melatonin with midazolam using a VAS did not find any evidence of a difference between the two groups in postoperative anxiety (relative effect -2.02, 95% CI -5.82 to 1.78).

AUTHORS' CONCLUSIONS

When compared to placebo, melatonin given as premedication (tablets or sublingually) can reduce preoperative anxiety in adults (measured 50 to 100 minutes after administration). Melatonin may be equally as effective as standard treatment with midazolam in reducing preoperative anxiety in adults (measured 50 to 100 minutes after administration). The effect of melatonin on postoperative anxiety (measured 90 minutes and 6 hours after surgery) in adults is mixed but suggests an overall attenuation of the effect compared to preoperatively.

Analgesic, anxiolytic and anaesthetic effects of melatonin: new potential uses in pediatrics

Exogenous melatonin is used in a number of situations, first and foremost in the treatment of sleep disorders and jet leg. However, the hypnotic, antinociceptive, and anticonvulsant properties of melatonin endow this neurohormone with the profile of a drug that modulates effects of anesthetic agents, supporting its potential use at different stages during anesthetic procedures, in both adults and children. In light of these properties, melatonin has been administered to children undergoing diagnostic procedures requiring sedation or general anesthesia, such as magnetic resonance imaging, auditory brainstem response tests and electroencephalogram. Controversial data support the use of melatonin as anxiolytic and antinociceptive agents in pediatric patients undergoing surgery. The aim of this review was to evaluate available evidence relating to efficacy and safety of melatonin as an analgesic and as a sedative agent in children. Melatonin and its analogs may have a role in antinociceptive therapies and as an alternative to midazolam in premedication of adults and children, although its effectiveness is still controversial and available data are clearly incomplete.

A comparative study between oral melatonin and oral midazolam on preoperative anxiety, cognitive, and psychomotor functions

BACKGROUND & AIMS

Melatonin, a naturally occurring hormone in the human body, has been reported to cause preoperative anxiolysis and sedation without impairing orientation. The aim of the following study was to evaluate and to compare the effects of oral melatonin and oral midazolam on preoperative anxiety, sedation, psychomotor, and cognitive function.

MATERIALS AND METHODS

A study conducted on 120 patients aged 16-55 years, of American Society of Anesthesiologists Grade 1 and 2 posted for elective surgery, with each group of melatonin, midazolam, and placebo comprising 40 patients. Patients were given either 0.4 mg/kg oral melatonin or 0.2 mg/kg oral midazolam or a placebo 60-90 min before induction. Preoperative anxiety was studied before and 60-90 min after giving medications using visual analog scale (VAS) anxiety score, orientation score, and sedation score. Psychomotor and cognitive functions were studied using the digit symbol substitution test (DSST) and trail making test (TMT) tests. Data were analyzed using Chi-square test or Kruskal-Wallis analysis of variance and the value of P < 0.05 was considered as statistically significant.

RESULTS

Changes in VAS anxiety scores were significant when melatonin was compared with placebo (P = 0.0124) and when midazolam was compared with placebo (P = 0.0003). When melatonin was compared with midazolam, no significant difference (P = 0.49) in VAS anxiety scores was observed. Intergroup comparison of sedation scores showed melatonin (P = 0.0258) and midazolam (P = 0.0000) to be statistically significant when compared with placebo. No changes in orientation scores occurred in melatonin and placebo group. Change in DSST scores and TMT scores were seen to be significant only in midazolam group.

CONCLUSION

Oral melatonin 0.4 mg/kg provides adequate anxiolysis comparable to that of oral midazolam. Unlike midazolam, oral melatonin 0.4 mg/kg does not impair the general cognitive and psychomotor function especially cognitive aspects such as working memory, memory retrieval, sustained attention, and flexibility of thinking.

Effect of melatonin and gabapentin on anxiety and pain associated with retrobulbar eye block for cataract surgery: a randomized double-blind study

Objectives:

To compare the effect of melatonin and gabapentin on anxiety, pain, sedation scores, and satisfaction of surgeon in patients of cataract surgery.

Materials and Methods:

One hundred thirty patients aged between 35 and 85 years scheduled for cataract surgery were randomly allocated to three study groups to receive melatonin (6 mg), gabapentin (600 mg) or placebo 90 min before arrival in the operating room. Pain, anxiety, and sedation scores during block and surgery as well as the surgeon's satisfaction with the surgery were assessed.

Results:

Anxiety scores decreased significantly in melatonin and gabapentin groups compared to the placebo group after premedication and extended to early postoperative period. The level of anxiety showed no statistically significant difference between melatonin and gabapentin groups at any time of measurement. There were significant differences between the pain scores during retrobulbar placement in gabapentin versus placebo (95% CI 3 to 4; P = 0.001) and melatonin (95% CI 3 to 4; P = 0.040) groups. Also, there were significant differences between the sedation scores during retrobulbar placement in gabapentin and placebo groups (95% CI 2 to 2.5; P = 0.046). The difference in sedation scores during retrobulbar placement in melatonin versus gabapentin and placebo groups was not significant. Neither the intraoperative pain scores nor the postoperative pain scores were different between the three groups. The surgeon reported similar quality of operation conditions during surgery for the three study groups.

Conclusion:

The level of anxiety was significantly lower with both anxiolytic drugs compared to placebo. Furthermore, gabapentin decreased the pain and improved the sedation scores only during retrobulbar placement compared to the placebo.

The effects of melatonin on anxiety and pain scores of patients, intraocular pressure, and operating conditions during cataract surgery under topical anesthesia

Aims:

To evaluate the effects of melatonin premedication on anxiety and pain scores of patients, operating conditions, and intraocular pressure during cataract surgery under topical anesthesia.

Materials and Methods:

Sixty patients were randomly assigned to receive either sublingual melatonin 3 mg or placebo 60 min before surgery. Verbal anxiety scores and verbal pain scores, heart rate, systolic and diastolic blood pressure, intraocular pressure, and quality of operating conditions were recorded.

Results:

Melatonin significantly reduced the anxiety scores (median, interquartile range) from 5 and 5–3 to 3 and 2–4 after premedication and to 3 and 2–3 during surgery and to 0 and 0–1 postoperatively before discharge from the recovery room. There were significant differences between two groups in anxiety scores after premedication (95% CI 3–3.5; P = 0.023), intraoperatively (95% CI 2.5–3.5; P = 0.007), and postoperatively (95% CI 0.5–1; P = 0.007). The surgeon reported better quality of operating conditions in the melatonin group (P = 0.001). No significant difference in intraoperative and postoperative pain scores, intraocular pressure, heart rate, and systolic and diastolic blood pressure between two groups was recorded.

Conclusion:

Sublingual melatonin premedication for patients undergoing cataract surgery under topical anesthesia reduced the anxiety scores in patients and provided excellent operating conditions.

Premedication with oral alprazolam and melatonin combination: a comparison with either alone--a randomized controlled factorial trial

We assessed if the addition of melatonin to alprazolam has superior premedication effects compared to either drug alone. A prospective, double blind placebo controlled trial randomly assigned 80 adult patients (ASA 1&2) with a Visual Analogue Score (VAS) for anxiety ≥3 to receive a tablet containing a combination of alprazolam 0.5 mg and melatonin 3 mg, alprazolam 0.5 mg, melatonin 3 mg, or placebo orally 90 min before a standard anesthetic. Primary end points were change in anxiety and sedation score at 15, 30, and 60 min after premedication, and number of patients with loss of memory for the five pictures shown at various time points when assessed after 24 h. One-way ANOVA, Friedman repeated measures analysis of variance, Kruskal Wallis and chi square tests were used as relevant. Combination drug produced the maximum reduction in anxiety VAS (3 (1.0–4.3)) from baseline at 60 min (P < 0.05). Sedation scores at various time points and number of patients not recognizing the picture shown at 60 min after premedication were comparable between combination drug and alprazolam alone. Addition of melatonin to alprazolam had superior anxiolysis compared with either drugs alone or placebo. Adding melatonin neither worsened sedation score nor the amnesic effect of alprazolam alone. This study was registered, approved, and released from ClinicalTrials.gov. Identifier number: NCT01486615.

The role of melatonin in anaesthesia and critical care

Melatonin is a neurohormone secreted by the pineal gland. It is widely present in both plant and animal sources. In several countries, it is sold over the counter as tablets and as food supplement or additive. Currently, it is most often used to prevent jet lag and to induce sleep. It has been and is being used in several clinical trials with different therapeutic approaches. It has sedative, analgesic, anti-inflammatory, anti-oxidative and chronobiotic effects. In the present review, the potential therapeutic benefits of melatonin in anaesthesia and critical care are presented. This article aims to review the physiological properties of melatonin and how these could prove useful for several clinical applications in perioperative management, critical care and pain medicine. The topic was handsearched from textbooks and journals and electronically from PubMed, and Google scholar using text words.

Perioperative plasma melatonin concentration in postoperative critically ill patients: its association with delirium

PURPOSE

Delirium is a common complication in postoperative critically ill patients. Although abnormal melatonin metabolism is thought to be one of the mechanisms of delirium, there have been few studies in which the association between alteration of perioperative plasma melatonin concentration and postoperative delirium was assessed.

MATERIALS

We conducted a prospective observational study to assess the association of perioperative alteration of plasma melatonin concentration with delirium in 40 postoperative patients who required intensive care for more than 48 hours. We diagnosed postoperative delirium using Confusion Assessment Method for the intensive care unit and measured melatonin concentration 4 times (before the operation as the preoperative value, 1 hour after the operation, postoperative day 1, and postoperative day 2).

RESULTS

Postoperative delirium occurred in 13 (33%) of the patients. Although there was no significant difference in preoperative melatonin concentration, Δ melatonin concentration at 1 hour after the operation was significantly lower in patients with delirium than in those without delirium (-1.1 vs 0 pg/mL, P = .036). After adjustment of relevant confounders, Δ melatonin concentration was independently associated with risk of delirium (odds ratio, 0.50; P = .047).

CONCLUSIONS

Delta melatonin concentration at 1 hour after the operation has a significant independent association with risk of postoperative delirium.

Role of melatonin in the prevention of morphine-induced hyperalgesia and spinal glial activation in rats: protein kinase C pathway involved

PURPOSES

Morphine can induce tolerance and hyperalgesia after long-term administration. Glial activation is believed to cause and maintain a state of morphine-induced pain hypersensitivity. The present study examines the effect of melatonin on tolerance, hyperalgesia, and reactive gliosis induced by morphine in rats.

METHODS

The study examines the effect of melatonin on morphine-induced hyperalgesia using tail-flick test. Immunohistochemistry and Western blot was performed to investigate the expression of glial fibrillary acidic protein (GFAP) indicative of spinal glial activity. This study also measures protein kinase C (PKC) activity and cyclic adenosine monophosphate (cAMP) levels in spinal cords to investigate the mechanisms which melatonin involved.

RESULTS

When coadministered intragastrically (i.g.) with morphine, melatonin in doses of 50 or 100 mg/kg significantly prevented hyperalgesia after termination of morphine. Immunohistochemistry and Western blot with GFAP revealed that melatonin significantly decreased morphine-induced over-expression of GFAP in spinal cord (p < .05). By measuring PKC activity and cAMP levels, the upregulated PKC activity and cAMP levels induced by morphine were significantly inhibited by melatonin.

CONCLUSIONS

Melatonin can prevent morphine-withdrawal-induced hyperalgesia and glial reactivity. This effect of melatonin after morphine administration may mediated by inhibiting PKC activity and cAMP upregulation.

Clinical uses of melatonin in pediatrics

This study analyzes the results of clinical trials of treatments with melatonin conducted in children, mostly focused on sleep disorders of different origin. Melatonin is beneficial not only in the treatment of dyssomnias, especially delayed sleep phase syndrome, but also on sleep disorders present in children with attention-deficit hyperactivity, autism spectrum disorders, and, in general, in all sleep disturbances associated with mental, neurologic, or other medical disorders. Sedative properties of melatonin have been used in diagnostic situations requiring sedation or as a premedicant in children undergoing anesthetic procedures. Epilepsy and febrile seizures are also susceptible to treatment with melatonin, alone or associated with conventional antiepileptic drugs. Melatonin has been also used to prevent the progression in some cases of adolescent idiopathic scoliosis. In newborns, and particularly those delivered preterm, melatonin has been used to reduce oxidative stress associated with sepsis, asphyxia, respiratory distress, or surgical stress. Finally, the administration of melatonin, melatonin analogues, or melatonin precursors to the infants through the breast-feeding, or by milk formula adapted for day and night, improves their nocturnal sleep. Side effects of melatonin treatments in children have not been reported. Although the above-described results are promising, specific studies to resolve the problem of dosage, formulations, and length of treatment are necessary.

Perioperative melatonin use

Melatonin is a substance chiefly produced by the pineal gland and has a key role in the sleep-wake cycle. It also has an important antioxidant role. Exogenous melatonin has a short half-life and is available in a range of preparations. Newer analogues targeted for the recently discovered melatonin MT1 and MT2 receptors have also been developed. Exogenous melatonin is used as a resynchronisation agent in jet lag and for other sleep disturbances. Perioperatively, melatonin has been used as a premedicant, sedative and analgesic. It decreases paediatric emergence delirium. The antioxidant properties of melatonin are being investigated for use in sepsis and reperfusion injuries. It would appear that patients on melatonin supplements should continue taking them perioperatively because there may be benefits. Melatonin and its analogues will be increasingly encountered in the perioperative setting.