The Hypothalamic–Pituitary–Adrenal Axis and Anesthetics

The Application and Pharmaceutical Development of Etomidate: Challenges and Strategies

Etomidate is a synthetic imidazole anesthetic that exerts hypnotic effects by potentiating the action of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) or directly activating the anionic GABA (GABAA) receptor. It stands out among many anesthetics because of its multiple advantages, such as good hemodynamic stability and minimal inhibition of spontaneous respiration. However, its low water solubility and side effects, such as adrenal cortex inhibition and myoclonus, have limited the clinical application of this drug. To address these issues, extensive research has been conducted on the drug delivery of etomidate in recent decades, which has led to the emergence of different etomidate preparations. Despite so many etomidate preparations, so far some of the toxic side effects have not yet been effectively addressed. Herein we discuss the pharmaceutical design of etomidate that may resolve the above problem. We also propose targeted strategies for future research on etomidate preparations and discuss the feasibility of different administration routes and dosage forms to expand the application of this drug. Through this review, we hope to draw more attention to the potential of etomidate and its application challenges and provide valuable insights into the development of new etomidate preparations.

Hypothalamic corticotropin-releasing hormone neurons modulate sevoflurane anesthesia and the post-anesthesia stress responses

General anesthesia (GA) is an indispensable procedure necessary for safely and compassionately administering a significant number of surgical procedures and invasive diagnostic tests. However, the undesired stress response associated with GA causes delayed recovery and even increased morbidity in the clinic. Here, a core hypothalamic ensemble, corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus (PVHCRH neurons), is discovered to play a role in regulating sevoflurane GA. Chemogenetic activation of these neurons delay the induction of and accelerated emergence from sevoflurane GA, whereas chemogenetic inhibition of PVHCRH neurons accelerates induction and delays awakening. Moreover, optogenetic stimulation of PVHCRH neurons induce rapid cortical activation during both the steady and deep sevoflurane GA state with burst-suppression oscillations. Interestingly, chemogenetic inhibition of PVHCRH neurons relieve the sevoflurane GA-elicited stress response (e.g., excessive self-grooming and elevated corticosterone level). These findings identify PVHCRH neurons modulate states of anesthesia in sevoflurane GA, being a part of anesthesia regulatory network of sevoflurane.

Androgens Suppress Corticosteroid Binding Globulin in Male Mice, Affecting the Endocrine Stress Response

Biological sex affects the activity of the hypothalamus-pituitary-adrenal (HPA) axis. However, how androgen deprivation affects this axis remains largely unknown. In this study, we investigated the effect of androgen status on different components of the HPA axis in male mice. Two weeks of androgen deprivation did not affect total plasma corticosterone levels but led to increased pituitary ACTH levels. Stress-induced total plasma corticosterone levels were increased, whereas the suppression of corticosterone after dexamethasone treatment under basal conditions was attenuated. Androgen-deprived mice displayed a 2-fold increase in plasma levels of corticosteroid binding globulin (CBG). A similar increase in CBG was observed in global androgen receptor knock-out animals, compared to wild-type littermates. Androgen deprivation was associated with a 6-fold increase in CBG mRNA in the liver and enhanced transcriptional activity at CBG regulatory regions, as evidenced by increased H3K27 acetylation. We propose that the induction of CBG as a consequence of androgen deprivation, together with the unaltered total corticosterone levels, results in lower free corticosterone levels in plasma. This is further supported by mRNA levels of androgen-independent GR target genes in the liver. The reduction in negative feedback on the HPA axis under basal condition would suffice to explain the enhanced stress reactivity after androgen deprivation. Overall, our data demonstrate that, in mice, tonic androgen receptor activation affects CBG levels in conjunction with effects on gene expression and HPA-axis reactivity.

Comparison of the efficacy and safety of ciprofol and propofol in sedating patients in the operating room and outside the operating room: a meta-analysis and systematic review

BACKGROUND

As a new type of intravenous anesthetic, ciprofol has the advantages of fast onset of action, fast recovery and high clearance rate. This study aimed to investigate the effectiveness and safety of ciprofol versus traditional propofol for anesthesia and sedation in and out of the operating room.

METHODS

We searched the literature in PubMed, Web of Science, Cochrane Library, and Embase databases from January 2021 to December 2023. All clinical studies comparing the sedative effects of propofol and ciprofol, both inside and outside the operating room, were included in our trial. The main outcome measures were induction time and incidence of injection-site pain. Data are merged using risk ratio and standardized mean difference with 95% confidence interval. Subgroup analysis, meta-regression, sensitivity analysis, and publication bias were performed. The study protocol was prospectively registered with PROSPERO (CRD42023447747).

RESULTS

A total of 15 randomized, controlled trials involving 2002 patients were included in this study. Compared with propofol, ciprofol has a longer induction time in the operating room but a shorter induction time in non-operating room settings. Ciprofol can effectively reduce the risk of injection-site pain and respiratory depression both inside and outside the operating room. In addition, the risk of drug-related hypotension induced with ciprofol in the operating room is lower, but the awakening time is also longer. Meta-regression analysis showed that neither age nor BMI were potential sources of heterogeneity. Funnel plot, egger and begg tests showed no significant publication bias. Sensitivity analyzes indicate that our results are robust and reliable.

CONCLUSION

Ciprofol has absolute advantages in reducing the risk of injection-site pain and respiratory depression, both in and outside operating room. Intraoperative use of ciprofol reduces the risk of drug-related hypotension and may also reduce the risk of intraoperative physical movements. However, ciprofol may have longer induction and awakening time than propofol.

Spanish Society of Anesthesiology, Reanimation and Pain Therapy (SEDAR), Spanish Society of Emergency and Emergency Medicine (SEMES) and Spanish Society of Otolaryngology, Head and Neck Surgery (SEORL-CCC) Guideline for difficult airway management. Part I

The Airway Management section of the Spanish Society of Anesthesiology, Resuscitation, and Pain Therapy (SEDAR), the Spanish Society of Emergency Medicine (SEMES), and the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) present the Guide for the comprehensive management of difficult airway in adult patients. Its principles are focused on the human factors, cognitive processes for decision-making in critical situations, and optimization in the progression of strategies application to preserve adequate alveolar oxygenation in order to enhance safety and the quality of care. The document provides evidence-based recommendations, theoretical-educational tools, and implementation tools, mainly cognitive aids, applicable to airway management in the fields of anesthesiology, critical care, emergencies, and prehospital medicine. For this purpose, an extensive literature search was conducted following PRISMA-R guidelines and was analyzed using the GRADE methodology. Recommendations were formulated according to the GRADE methodology. Recommendations for sections with low-quality evidence were based on expert opinion through consensus reached via a Delphi questionnaire.

Sepsis and Adrenal Insufficiency

In sepsis, dysregulation of the hypothalamic-pituitary-adrenal axis, alterations in cortisol metabolism, and tissue resistance to glucocorticoids can all result in relative adrenal insufficiency or critical illness-related corticosteroid insufficiency (CIRCI). The symptoms and signs of CIRCI during sepsis are nonspecific, generally including decreased mental status, unexplained fever, or hypotension refractory to fluids, and the requirement of vasopressor therapy to maintain adequate blood pressure. While we have been aware of this syndrome for over a decade, it remains a poorly understood condition, challenging to diagnose, and associated with significantly diverging practices among clinicians, particularly regarding the optimal dosing and duration of corticosteroid therapy. The existing literature on corticosteroid use in patients with sepsis and septic shock is vast with dozens of randomized controlled trials conducted across the past 4 decades. These studies have universally demonstrated reduced duration of shock, though the effects of corticosteroids on mortality have been inconsistent, and their use has been associated with adverse effects including hyperglycemia, neuromuscular weakness, and an increased risk of infection. In this article, we aim to provide a thorough, evidence-based, and practical review of the current recommendations for the diagnosis and management of patients with sepsis who develop CIRCI, explore the controversies surrounding this topic, and highlight what lies on the horizon as new evidence continues to shape our practice.

Electroacupuncture Ameliorates Hypothalamic‒Pituitary‒Adrenal Axis Dysfunction Induced by Surgical Trauma in Mice Through the Hypothalamic Oxytocin System

Electroacupuncture (EA) can effectively reduce surgical stress reactions and promote postoperative recovery, but the mechanisms remain unclear. The present study aims to examine the effects of EA on the hyperactivity of the hypothalamic‒pituitary‒adrenal (HPA) axis and investigate its potential mechanisms. Male C57BL/6 mice were subjected to partial hepatectomy (HT). The results showed that HT increased the concentrations of corticotrophin-releasing hormone (CRH), corticosterone (CORT), and adrenocorticotropic hormone (ACTH) in the peripheral blood and upregulated the expression of CRH and glucocorticoid receptors (GR) proteins in the hypothalamus. EA treatment significantly inhibited the hyperactivity of the HPA axis by decreasing the concentration of CRH, CORT, and ACTH in peripheral blood and downregulating the expression of CRH and GR in the hypothalamus. Moreover, EA treatment reversed the HT-induced downregulation of oxytocin (OXT) and oxytocin receptor (OXTR) in the hypothalamus. Furthermore, intracerebroventricular injection of the OXTR antagonist atosiban blocked the effects of EA. Thus, our findings implied that EA mitigated surgical stress-induced HPA axis dysfunction by activating the OXT/OXTR signaling pathway.

Rapid sequence intubation and the role of the emergency medicine pharmacist: 2022 update

PURPOSE

The dosing, potential adverse effects, and clinical outcomes of the most commonly utilized pharmacologic agents for rapid sequence intubation (RSI) are reviewed for the practicing emergency medicine pharmacist (EMP).

SUMMARY

RSI is the process of establishing a safe, functional respiratory system in patients unable to effectively breathe on their own. Various medications are chosen to sedate and even paralyze the patient to facilitate an efficient endotracheal intubation. The mechanism of action and pharmacokinetic/pharmacodynamic profiles of these agents were described in a 2011 review. Since then, the role of the EMP as well as the published evidence regarding RSI agents, including dosing, adverse effects, and clinical outcomes, has grown. It is necessary for the practicing EMP to update previous practice patterns in order to continue to provide optimal patient care.

CONCLUSION

While the agents used in RSI have changed little, knowledge regarding optimal dosing, appropriate patient selection, and possible adverse effects continues to be gained. The EMP is a key member of the bedside care team and uniquely positioned to communicate this evolving data.

General anesthesia bullies the gut: a toxic relationship with dysbiosis and cognitive dysfunction

Perioperative neurocognitive disorder (PND) is a common surgery outcome affecting up to a third of the elderly patients, and it is associated with high morbidity and increased risk for Alzheimer's disease development. PND is characterized by cognitive impairment that can manifest acutely in the form of postoperative delirium (POD) or after hospital discharge as postoperative cognitive dysfunction (POCD). Although POD and POCD are clinically distinct, their development seems to be mediated by a systemic inflammatory reaction triggered by surgical trauma that leads to dysfunction of the blood-brain barrier and facilitates the occurrence of neuroinflammation. Recent studies have suggested that the gut microbiota composition may play a pivotal role in the PND development by modulating the risk of neuroinflammation establishment. In fact, modulation of gut microbiome composition with pre- and probiotics seems to be effective for the prevention and treatment of PND in animals. Interestingly, general anesthetics seem to have major responsibility on the gut microbiota composition changes following surgery and, consequently, can be an important element in the process of PND initiation. This concept represents an important milestone for the understanding of PND pathogenesis and may unveil new opportunities for the development of preventive or mitigatory strategies against the development of these conditions. The aim of this review is to discuss how anesthetics used in general anesthesia can interact and alter the gut microbiome composition and contribute to PND development by favoring the emergence of neuroinflammation.

Pharmacodynamics and Pharmacokinetics of HSK3486, a Novel 2,6-Disubstituted Phenol Derivative as a General Anesthetic

Background: The purpose of this study was to characterize the novel sedative/hypnotic agent HSK3486, a 2,6-disubstituted alkylphenol analogue.

Methods: The mechanism of action of HSK3486 was studied in competitive binding assays and whole-cell patch clamp assays. HSK3486 was administered by bolus intravenous injection to dogs and rats, and the loss of righting reflex as well as effects on the cardiovascular and respiratory systems were assessed. The in vitro metabolism of HSK3486 was analyzed by CYP450 genotyping and enzyme inhibition.

Results: HSK3486 competed with t-butylbicycloorthobenzoate (TBOB) and t-butylbicyclophosphorothionate (TBPS) for binding to the gamma-aminobutyric acid type A (GABA_A) receptor. HSK3486 potentiated GABA-evoked chloride currents at lower concentrations while activating GABA_A receptor at higher concentrations. HSK3486 induced hypnosis in rats and dogs, and had a higher therapeutic index than propofol in rats. The hypnotic potency of HSK3486 was approximately 4-5 fold higher than that of propofol. HSK3486 exerted minimal effects on the cardiovascular system.

Conclusions: HSK3486 is a positive allosteric regulator and direct agonist of GABA_A receptor. It has a promising sedative/hypnotic effect and good in vivo pharmacokinetic properties, which justify further studies towards its clinical application.

Intrinsic Connectivity Networks of Glutamate-Mediated Antidepressant Response: A Neuroimaging Review

Conventional monoamine-based pharmacotherapy, considered the first-line treatment for major depressive disorder (MDD), has several challenges, including high rates of non-response. To address these challenges, preclinical and clinical studies have sought to characterize antidepressant response through monoamine-independent mechanisms. One striking example is glutamate, the brain's foremost excitatory neurotransmitter: since the 1990s, studies have consistently reported altered levels of glutamate in MDD, as well as antidepressant effects following molecular targeting of glutamatergic receptors. Therapeutically, this has led to advances in the discovery, testing, and clinical application of a wide array of glutamatergic agents, particularly ketamine. Notably, ketamine has been demonstrated to rapidly improve mood symptoms, unlike monoamine-based interventions, and the neurobiological basis behind this rapid antidepressant response is under active investigation. Advances in brain imaging techniques, including functional magnetic resonance imaging, magnetic resonance spectroscopy, and positron emission tomography, enable the identification of the brain network-based characteristics distinguishing rapid glutamatergic modulation from the effect of slow-acting conventional monoamine-based pharmacology. Here, we review brain imaging studies that examine brain connectivity features associated with rapid antidepressant response in MDD patients treated with glutamatergic pharmacotherapies in contrast with patients treated with slow-acting monoamine-based treatments. Trends in recent brain imaging literature suggest that the activity of brain regions is organized into coherent functionally distinct networks, termed intrinsic connectivity networks (ICNs). We provide an overview of major ICNs implicated in depression and explore how treatment response following glutamatergic modulation alters functional connectivity of limbic, cognitive, and executive nodes within ICNs, with well-characterized anti-anhedonic effects and the enhancement of "top-down" executive control. Alterations within and between the core ICNs could potentially exert downstream effects on the nodes within other brain networks of relevance to MDD that are structurally and functionally interconnected through glutamatergic synapses. Understanding similarities and differences in brain ICNs features underlying treatment response will positively impact the trajectory and outcomes for adults suffering from MDD and will facilitate the development of biomarkers to enable glutamate-based precision therapeutics.

Application of a new serratus anterior plane block in modified radical mastectomy under ultrasound guidance: A prospective, randomized controlled trial

STUDY OBJECTIVES

Post-operative pain is a significant concern following modified radical mastectomy in breast cancer patients. The serratus anterior plane block has recently been described as an effective technique for post-operative analgesia of modified radical mastectomy. The purpose of this study was to evaluate the analgesic efficacy and safety of a new serratus anterior plane (SAP) block for post-operative pain of mastectomy.

DESIGN

A randomized controlled trial.

SETTING

Single university teaching hospital, from October 2019 to April 2020.

PATIENTS

Eighty-seven female breast cancer patients aged 30-81 years scheduled for unilateral modified radical mastectomy.

INTERVENTIONS

Participants were randomly allocated to receive either general anesthesia plus SAP block (SAP block group, n = 43) or general anesthesia alone (Control group, n = 44). A single injection of 20 ml of 0.5% ropivacaine was administered into fascial plane between the pectoralis major and the serratus anterior in SAP block group. In the Control group, no block intervention was applied.

MEASUREMENTS

The primary outcome measure of the study was the VAS pain scores at different time-points (1, 6, 12, 24, 48 h) after modified radical mastectomy whereas the secondary outcome measures were the consumption of opioid analgesics.

MAIN RESULTS

Breast cancer patients in SAP block group had lower VAS pain scores compared with the Control group during the early post-operative period (1 h and 6 h after modified radical mastectomy), both at rest and with movement. In addition, the consumption of propofol was similar in two groups (P = 0.406), and the consumption of sufentanil and remifentanil in SAP block group were significantly lower than that of Control group (P = 0.000 and P = 0.000, respectively).

CONCLUSIONS

SAP block significantly attenuated post-operative pain and decreased opioids consumption in breast cancer patients undergoing modified radical mastectomy.

TRIAL REGISTRATION

This trial is registered in the Chinese Clinical Trial Registry (ChiCTR1900026989).

Mechanistic consideration of the effect of perioperative volatile anesthetics on phagocytes

A growing literature has shown that volatile anesthetics are promiscuous molecules targeting multiple molecules, some of which are critical for immunological functions. We focused on studies that delineated target molecules of volatile anesthetics on immune cells and summarized the effects of volatile anesthetics on immune functions. We also presented the perspectives of studying volatile anesthetics-mediated immunomodulation.

Outpatient breast-conserving surgery for breast cancer: Use of local and intravenous anesthesia and/or sedation may reduce recurrence and improve survival

The use of general anesthesia (GA) with inhalational anesthetics for breast cancer surgery may be associated with breast cancer recurrence and increased mortality due to the immunosuppressive effects of these drugs. Less-immunosuppressive anesthetic techniques may reduce breast cancer recurrence. We evaluated the feasibility, safety, and efficacy of outpatient breast-conserving surgery (BCS) for breast cancer in a breast clinic in terms of the anesthetic technique used, complications occurring, recurrence, and survival. Methods: The sample comprised 456 consecutive patients with stage 0–III breast cancer who underwent BCS/axillary lymph node (ALN) management using local and intravenous anesthesia and/or sedation between May 2008 and January 2020. Most patients received adjuvant chemotherapy and/or endocrine therapy and radiotherapy after surgery. Patient outcomes were evaluated retrospectively. Results: All patients recovered and were discharged after resting for 3–4 h postoperatively. No procedure-related severe complication or death occurred. Sixty-four complications (14.0%) were observed: 14 wound infections, 17 hematomas, and 33 axillary lymphoceles. The median follow-up period was 2259 days (range, 9–4190 days), during which disease recurrence was observed in 25 (5.4%) patients. The overall survival and breast cancer–specific survival rates were 92.3% and 94.7%, respectively. Conclusions: Outpatient surgery for breast cancer involving BCS and ALN management under local and intravenous anesthesia and/or sedation can be performed safely, without serious complication or death. Less-immunosuppressive anesthetic techniques with spontaneous breathing may reduce the recurrence of breast cancer and improve survival relative to GA.

•

Outpatient surgery for breast cancer involving breast-conserving surgery (BCS) and axillary lymph node (ALN) management under local and intravenous anesthesia and/or sedation can be performed safely.

•

Less-immunosuppressive anesthetic techniques with spontaneous breathing may reduce the recurrence of breast cancer and improve survival compared with general anesthesia.

Dynamics and prognostic value of the hypothalamus-pituitary-adrenal axis responses to pediatric critical illness and association with corticosteroid treatment: a prospective observational study

PURPOSE

Increased systemic cortisol availability during adult critical illness is determined by reduced binding-proteins and suppressed breakdown rather than elevated ACTH. Dynamics, drivers and prognostic value of hypercortisolism during pediatric critical illness remain scarcely investigated.

METHODS

This preplanned secondary analysis of the PEPaNIC-RCT (N = 1440), after excluding 420 children treated with corticosteroids before PICU-admission, documented (a) plasma ACTH, (free)cortisol and cortisol-metabolism at PICU-admission, day-3 and last PICU-day, their prognostic value, and impact of withholding early parenteral nutrition (PN), (b) the association between corticosteroid-treatment and these hormones, and (c) the association between corticosteroid-treatment and outcome.

RESULTS

ACTH was normal upon PICU-admission and low thereafter (p ≤ 0.0004). Total and free cortisol were only elevated upon PICU-admission (p ≤ 0.0003) and thereafter became normal despite low binding-proteins (p < 0.0001) and persistently suppressed cortisol-metabolism (p ≤ 0.03). Withholding early-PN did not affect this phenotype. On PICU-day-3, high free cortisol and low ACTH independently predicted worse outcome (p ≤ 0.003). Also, corticosteroid-treatment initiated in PICU, which further suppressed ACTH (p < 0.0001), was independently associated with poor outcomes (earlier live PICU-discharge: p < 0.0001, 90-day mortality: p = 0.02).

CONCLUSION

In critically ill children, systemic cortisol availability is elevated only transiently, much lower than in adults, and not driven by elevated ACTH. Further ACTH lowering by corticosteroid-treatment indicates active feedback inhibition at pituitary level. Beyond PICU-admission-day, low ACTH and high cortisol, and corticosteroid-treatment, predicted poor outcome. This suggests that exogenously increasing cortisol availability during acute critical illness in children may be inappropriate. Future studies on corticosteroid-treatment in critically ill children should plan safety analyses, as harm may be possible.

Perioperative serum cortisol levels in ACTH sufficient and ACTH deficient patients during transsphenoidal surgery of pituitary adenoma

PURPOSE

No previous study has analyzed serum cortisol levels during transsphenoidal endoscopic pituitary surgery in patients with and without hydrocortisone (HC) substitution.

METHODS

A total of 15 patients undergoing surgery for a pituitary adenoma were studied. Those with normal ACTH function were either not given HC (n = 7) or received 50 mg intravenous HC at the start of surgery (n = 4). Patients with ACTH deficiency received intravenous HC of 100 mg in the morning before surgery (n = 4) with the additional 50 mg for an afternoon operation (n = 2). Propofol and remifentanil were used as anesthetics. Serum cortisol was measured at the start of and every 30 min during surgery.

RESULTS

Among 7 patients with normal ACTH function without HC substitution, cortisol levels before surgery were 126-244 nmol/L, among the 4 patients undergoing surgery in the morning, whereas the 3 who underwent surgery in the afternoon had lower levels, 38-76 nmol/L. During nose/sinus surgery cortisol levels decreased to 79-139 and 24-54 nmol/L, respectively. At intrasellar manipulation a distinct rise was noted. Also, in the 4 ACTH sufficient patients receiving HC, cortisol levels decreased during nose/sinus surgery, but only with a slight increase during intrasellar surgery. In the 4 ACTH deficient patients cortisol peaked at 1914-2582 nmol/L.

CONCLUSIONS

Patients with normal ACTH function without HC substitution had very low cortisol levels during the first part of surgery, likely suppressed by the anesthetics. After mechanical impact in the sella, a marked increase in cortisol was noted. Supraphysiological cortisol levels were achieved with our routine HC substitution, advising us to reduce the supplementation.