The neurologic basis of fever

A review on targeted temperature management for cardiac arrest and traumatic brain injury

Therapeutic hypothermia inhibits organ damage by suppressing metabolism, which makes it a therapy of choice for treating various diseases. Specifically, it is often used to treat conditions involving central nervous system disorders where it is expected to positively impact functional prognosis. Although keeping the body temperature at a hypothermic level has been conventionally used, how to manage the body temperature correctly remains a topic of debate. Recently, the concept of temperature management has been proposed to improve the quality of body temperature control and avoid hyperthermia. This review focuses on the effect of temperature on the central nervous system in conditions involving central nervous system disorders and the practice of temperature management in clinical situations.

Recognizing the roles of fever in host survival and in medical intervention in infectious diseases

Fever has roles both in host defense against infectious challenges and in guidance of medical intervention. These roles remain insufficiently acknowledged and considered by both health care providers and patients and their families. This review cites reports in support of both roles and provides recommendations regarding the clinician's approach to fever, as well as points relevant for education of patients and their families.

Antipyretic Use in Noncritically Ill Patients With Fever: A Review

Antipyretics are one of the most frequently used agents in medicine. Numerous pharmacological agents, such as acetaminophen, non-steroidal anti-inflammatory agents (NSAIDs), salicylates, and selective cyclooxygenase 2 (COX-2) inhibitors, and nonpharmacological treatment modalities, such as tepid sponging and cooling blankets, are available for temperature reduction. There is a scarcity of definitive clinical guidelines on the choice of various agents in noncritically ill febrile patients. Our review examined the various modalities available for antipyresis and compared their safety and efficacy. The rationale for the choice of a particular pharmacological agent and route of administration were scrutinized. Our review also envisaged the perceived beneficial effects of antipyretics against the harmful side effects, including the evaluation of morbidity or mortality advantage conferred by antipyretics. The various toxicities associated with these agents were also highlighted.

Brain evolution and the meaning of catatonia - An update

Back in 2004, in a chapter titled "Brain Evolution and the Meaning of Catatonia", a case was made that the syndrome's core meaning is embedded in millions of years of vertebrate brain evolution. (Fricchione, 2004) In this update, advances over the last almost 20 years, in catatonia theory and research in particular, and pertinent neuropsychiatry in general, will be applied to this question of meaning. The approach will rely heavily on a number of thought leaders, including Nicos Tinbergen, Paul MacLean, John Bowlby, M. Marsel Mesulam, Bruce McEwen and Karl Friston. Their guidance will be supplemented with a selected survey of 21sty century neuropsychiatry, neurophysiology, molecular biology, neuroimaging and neurotherapeutics as applied to the catatonic syndrome. In an attempt to address the question of the meaning of the catatonic syndrome in human life, we will employ two conceptual networks representing the intersubjectivity of the quantitative conceptual network of physical terms and the subjectivity of the qualitative conceptual network of mental and spiritual terms. In the process, a common referent providing extensional identity may emerge (Goodman, 1991). The goal of this exercise is to enhance our attunement with the experience of patients suffering with catatonia. A deeper understanding of catatonia's origins in brain evolution and of the challenges of individual epigenetic development in the setting of environmental events coupled with appreciation of what has been described as the most painful mammalian condition, that of separation, has the potential to foster greater efforts on the part of clinicians to diagnose and treat patients who present with catatonia. In addition, in this ancient and extreme tactic, evolved to provide safety from extreme survival threat, one can speculate what is at the core of human fear and the challenge it presents to all of us. And when the biology, psychology and sociology of catatonia are examined, the nature of solutions to the challenge may emerge.

Parallel neural pathways control sodium consumption and taste valence

The hedonic value of salt fundamentally changes depending on the internal state. High concentrations of salt induce innate aversion under sated states, whereas such aversive stimuli transform into appetitive ones under sodium depletion. Neural mechanisms underlying this state-dependent salt valence switch are poorly understood. Using transcriptomics state-to-cell-type mapping and neural manipulations, we show that positive and negative valences of salt are controlled by anatomically distinct neural circuits in the mammalian brain. The hindbrain interoceptive circuit regulates sodium-specific appetitive drive , whereas behavioral tolerance of aversive salts is encoded by a dedicated class of neurons in the forebrain lamina terminalis (LT) expressing prostaglandin E2 (PGE2) receptor, Ptger3. We show that these LT neurons regulate salt tolerance by selectively modulating aversive taste sensitivity, partly through a PGE2-Ptger3 axis. These results reveal the bimodal regulation of appetitive and tolerance signals toward salt, which together dictate the amount of sodium consumption under different internal states.

Antipyretic Efficacy of Bromocriptine in Central Fever: an Exploratory Analysis

BACKGROUND

'Central' fevers are thought to result from disruption of hypothalamic thermoregulatory pathways following severe brain injuries. Bromocriptine, due to its central dopamine receptor agonism, has been hypothesized to have antipyretic effect in this setting. However, clinical evidence for this off-label use is limited to a few case reports. In this retrospective cohort study, we analyzed the effect of bromocriptine administration on body temperature in acute brain injury patients with suspected central fever.

METHODS

We screened a cohort of adult patients that received bromocriptine in the neurologic-intensive care unit of a tertiary care hospital between January 2018 and December 2021. Indication of central fever was ascertained by review of clinical documentation. A generalized additive mixed model (GAMM) was used to model temperature as a function of time relative to bromocriptine initiation. We adjusted for potential confounding due to the following covariates: temperature recording method (invasive vs surface), concurrent antipyretic administration within 8 h, and surface cooling device use within 4 h of temperature measurement. Temperature-time function was modeled using a cubic spline with k = 10 knots.

RESULTS

A total of 33 patients were included in the analysis (14 women; mean age: 50 y, standard deviation 14 y). Median dose of bromocriptine was 7.5 mg (range 2.5-40) for a median of 13 d (range 5-160). Age and sex did not impact the function of temperature over time. Predicted temperatures were significantly (p < 0.05) higher by 0.4 °C with invasive compared to surface recording methods, lower by 0.2 °C in the presence of cooling device use and lower by 0.1 °C with concurrent antipyretic use. On adjusted analysis with the GAMM, there was decline (p < 0.05) in temperature following bromocriptine initiation by - 0.3 °C at 24 h, - 0.5 °C at 48 h, and - 0.7 °C at 72 h.

CONCLUSIONS

Bromocriptine use was associated with modest but statistically significant decline in temperature, with nadir at 72 h post initiation. The findings provide a data driven basis for prospective evaluation.

Increased LPS-Induced Fever and Sickness Behavior in Adult Male and Female Rats Perinatally Exposed to Morphine

As a result of the current opioid crisis, the rate of children born exposed to opioids has skyrocketed. Later in life, these children have an increased risk for hospitalization and infection, raising concerns about potential immunocompromise, as is common with chronic opioid use. Opioids can act directly on immune cells or indirectly via the central nervous system to decrease immune system activity, leading to increased susceptibility, morbidity, and mortality to infection. However, it is currently unknown how perinatal opioid exposure (POE) alters immune function. Using a clinically relevant and translatable model of POE, we have investigated how baseline immune function and the reaction to an immune stimulator, lipopolysaccharide, is influenced by in utero opioid exposure in adult male and female rats. We report here that POE potentiates the febrile and neuroinflammatory response to lipopolysaccharide, likely as a consequence of suppressed immune function at baseline (including reduced antibody production). This suggests that POE increases susceptibility to infection by manipulating immune system development, consistent with the clinical literature. Investigation of the mechanisms whereby POE increases susceptibility to pathogens is critical for the development of potential interventions for immunosuppressed children exposed to opioids in utero.

Duration of Device-Based Fever Prevention after Cardiac Arrest

BACKGROUND

Guidelines recommend active fever prevention for 72 hours after cardiac arrest. Data from randomized clinical trials of this intervention have been lacking.

METHODS

We randomly assigned comatose patients who had been resuscitated after an out-of-hospital cardiac arrest of presumed cardiac cause to device-based temperature control targeting 36°C for 24 hours followed by targeting of 37°C for either 12 or 48 hours (for total intervention times of 36 and 72 hours, respectively) or until the patient regained consciousness. The primary outcome was a composite of death from any cause or hospital discharge with a Cerebral Performance Category of 3 or 4 (range, 1 to 5, with higher scores indicating more severe disability; a category of 3 or 4 indicates severe cerebral disability or coma) within 90 days after randomization. Secondary outcomes included death from any cause and the Montreal Cognitive Assessment score (range, 0 to 30, with higher scores indicating better cognitive ability) at 3 months.

RESULTS

A total of 393 patients were randomly assigned to temperature control for 36 hours, and 396 patients were assigned to temperature control for 72 hours. At 90 days after randomization, a primary end-point event had occurred in 127 of 393 patients (32.3%) in the 36-hour group and in 133 of 396 patients (33.6%) in the 72-hour group (hazard ratio, 0.99; 95% confidence interval, 0.77 to 1.26; P = 0.70) and mortality was 29.5% in the 36-hour group and 30.3% in the 72-hour group. At 3 months, the median Montreal Cognitive Assessment score was 26 (interquartile range, 24 to 29) and 27 (interquartile range, 24 to 28), respectively. There was no significant between-group difference in the incidence of adverse events.

CONCLUSIONS

Active device-based fever prevention for 36 or 72 hours after cardiac arrest did not result in significantly different percentages of patients dying or having severe disability or coma. (Funded by the Novo Nordisk Foundation; BOX ClinicalTrials.gov number, NCT03141099.).

Effects of temperature control on hyperthermia-related cardiac dysfunction in a porcine model of cardiac arrest

The outcome of cardiac arrest is worse when there is fever after spontaneous circulation is restored (ROSC). The purpose of this study was to investigate the mechanism of post-ROSC cardiac dysfunction after hyperthermia treatment and the effects of temperature control. Twenty-four male Bama minipigs were randomized into 3 groups (8 per group): CPR + controlled normothermia (CN), CPR + hyperthermia (HT), and CPR + therapeutic mild hypothermia (TMH). Defibrillation was given to pigs with ventricular fibrillation after 8 min of untreated fibrillation. Subsequently, these animals received the post-ROSC treatments of hyperthermia (38 °C), controlled normothermia (37 °C) or hypothermia (33 °C) according to the groups. Hemodynamic parameters, left ventricular ejection fraction, blood samples and myocardial tissues were assessed. At 24 h after the post-ROSC treatments, the pigs treated with hyperthermia showed increments in heart rate and plasma cardiac troponin I, and decreases in mean arterial pressure, cardiac index, and left ventricular ejection fraction, compared to those with the controlled normothermia pigs. However, the deterioration of the above parameters can be attenuated by TMH. The pigs in the TMH group also had a reduced percentage of apoptotic cardiomyocytes, an increased anti-apoptotic Bcl-2/Bax ratio and a decreased caspase-3 activity in myocardium, as compared with both controlled normothermia and hyperthermia pigs. In conclusion, hyperthermia is associated with a worse myocardial dysfunction. TMH improves hyperthermia-induced myocardial dysfunction by attenuating apoptosis in a porcine model of cardiac arrest.

A Link Between Inflammatory Mechanisms and Fibromyalgia

Fibromyalgia (FM) is a condition characterized by chronic widespread pain, which has traditionally been considered psychogenic in nature due to lack of known underlying organic pathophysiology. In more recent years, inflammation of the nervous system has become increasingly recognized as a sign of neuropsychiatric conditions, and this association may enhance our knowledge of conditions such as FM. Emerging evidence has suggested inflammation, particularly neuroinflammation, as a potential contributor underlying the etiology of FM. Studies have searched for linked biomarkers with mixed results, though the literature is beginning to point to increased systemic levels of pro-inflammatory cytokines such as IL-6 and IL-8 in patients with FM relative to healthy controls. A multicenter imaging study has also reported results suggestive of microglial activation related to the presence of FM. Given the consistency in neuroinflammatory effects implicated in "sickness behavior" characteristic of chronic systemic inflammatory conditions such as cancer or rheumatic diseases, therein springs the hypothesis for a connection between FM and neuroinflammation as discussed in this chapter.

Fever therapy in febrile adults: systematic review with meta-analyses and trial sequential analyses

OBJECTIVE

To investigate the effects of fever therapy compared with no fever therapy in a wide population of febrile adults.

DESIGN

Systematic review with meta-analyses and trial sequential analyses of randomised clinical trials.

DATA SOURCES

CENTRAL, BIOSIS, CINAHL, MEDLINE, Embase, LILACS, Scopus, and Web of Science Core Collection, searched from their inception to 2 July 2021.

ELIGIBILITY CRITERIA

Randomised clinical trials in adults diagnosed as having fever of any origin. Included experimental interventions were any fever therapy, and the control intervention had to be no fever therapy (with or without placebo/sham).

DATA EXTRACTION AND SYNTHESIS

Two authors independently selected studies, extracted data, and assessed the risk of bias. Primary outcomes were all cause mortality and serious adverse events. Secondary outcomes were quality of life and non-serious adverse events. Aggregate data were synthesised with meta-analyses, subgroup analyses, and trial sequential analyses, and the evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Forty two trials assessing 5140 participants were included. Twenty three trials assessed 11 different antipyretic drugs, 11 trials assessed physical cooling, and eight trials assessed a combination of antipyretic drugs and physical cooling. Of the participants, 3007 were critically ill, 1892 were non-critically ill, 3277 had infectious fever, and 1139 had non-infectious fever. All trials were assessed as being at high risk of bias. Meta-analysis and trial sequential analysis showed that the hypothesis that fever therapy reduces the risk of death (risk ratio 1.04, 95% confidence interval 0.90 to 1.19; I²=0%; P=0.62; 16 trials; high certainty evidence) and the risk of serious adverse events (risk ratio 1.02, 0.89 to 1.17; I²=0%; P=0.78; 16 trials; high certainty evidence) could be rejected. One trial assessing quality of life was included, showing no difference between fever therapy and control. Meta-analysis and trial sequential analysis showed that the hypothesis that fever therapy reduces the risk of non-serious adverse events could be neither confirmed nor rejected (risk ratio 0.92, 0.67 to 1.25; I²=66.5%; P=0.58; four trials; very low certainty evidence).

CONCLUSIONS

Fever therapy does not seem to affect the risk of death and serious adverse events.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019134006.

Identification of Virulence Associated Region during Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus during Attenuation In Vitro: Complex Question with Different Strain Backgrounds

Highly pathogenic porcine reproductive and respiratory syndrome virus PRRSV (HP-PRRSV) was one of the most devastating diseases of the pig industry, among various strategies, vaccination was one of the most useful tools for PRRS control. Attenuated live vaccine was used worldwide, however, the genetic basis of HP-PRRSV virulence change during attenuation remain to be determined. Here, to identify virulence associated regions of HP-PRRSV during attenuation in vitro, six full-length infectious cDNA clones with interchanges of 5′UTR + ORF1a, ORF1b, and ORF2-7 + 3′UTR regions between HP-PRRSV strain HuN4-F5 and its attenuated vaccine strain HuN4-F112 were generated, and chimeric viruses were rescued. Piglets were inoculated with chimeric viruses and their parental viruses, and rectal temperature were recorded daily, and serum were collected for future experiments. Our results showed that ORF1a played an important role on virus replication, cytokine response and lung damage, the exchange of ORF1b and ORF2-7 in different backbone led to different exhibition on virus replication in vivo/vitro and cytokine response. Among 9 PRRSV attenuated series, consistent amino acid changes during PRRSV attenuation were found in NSP4, NSP9, GP2, E, GP3 and GP4. Our study provides a fundamental data for the investigation of PRRSV attenuation, the different results of the virulence change among different studies indicated that different mechanisms might be used during PRRSV virulence enhancement in vivo and attenuation in vitro.

Respiratory Drive in Patients with Sepsis and Septic Shock: Modulation by High-flow Nasal Cannula

BACKGROUND

Experimental and pilot clinical data suggest that spontaneously breathing patients with sepsis and septic shock may present increased respiratory drive and effort, even in the absence of pulmonary infection. The study hypothesis was that respiratory drive and effort may be increased in septic patients and correlated with extrapulmonary determinant and that high-flow nasal cannula may modulate drive and effort.

METHODS

Twenty-five nonintubated patients with extrapulmonary sepsis or septic shock were enrolled. Each patient underwent three consecutive steps: low-flow oxygen at baseline, high-flow nasal cannula, and then low-flow oxygen again. Arterial blood gases, esophageal pressure, and electrical impedance tomography data were recorded toward the end of each step. Respiratory effort was measured as the negative swing of esophageal pressure (ΔPes); drive was quantified as the change in esophageal pressure during the first 500 ms from start of inspiration (P0.5). Dynamic lung compliance was calculated as the tidal volume measured by electrical impedance tomography, divided by ΔPes. The results are presented as medians [25th to 75th percentile].

RESULTS

Thirteen patients (52%) were in septic shock. The Sequential Organ Failure Assessment score was 5 [4 to 9]. During low-flow oxygen at baseline, respiratory drive and effort were elevated and significantly correlated with arterial lactate (r = 0.46, P = 0.034) and inversely with dynamic lung compliance (r = -0.735, P < 0.001). Noninvasive support by high-flow nasal cannula induced a significant decrease of respiratory drive (P0.5: 6.0 [4.4 to 9.0] vs. 4.3 [3.5 to 6.6] vs. 6.6 [4.9 to 10.7] cm H2O, P < 0.001) and effort (ΔPes: 8.0 [6.0 to 11.5] vs. 5.5 [4.5 to 8.0] vs. 7.5 [6.0 to 12.6] cm H2O, P < 0.001). Oxygenation and arterial carbon dioxide levels remained stable during all study phases.

CONCLUSIONS

Patients with sepsis and septic shock of extrapulmonary origin present elevated respiratory drive and effort, which can be effectively reduced by high-flow nasal cannula.

EDITOR’S PERSPECTIVE

Role of the Preoptic Area in Sleep and Thermoregulation

Sleep and body temperature are tightly interconnected in mammals: warming up our body helps to fall asleep and the body temperature in turn drops while falling asleep. The preoptic area of the hypothalamus (POA) serves as an essential brain region to coordinate sleep and body temperature. Understanding how these two behaviors are controlled within the POA requires the molecular identification of the involved circuits and mapping their local and brain-wide connectivity. Here, we review our current understanding of how sleep and body temperature are regulated with a focus on recently discovered sleep- and thermo-regulatory POA neurons. We further discuss unresolved key questions including the anatomical and functional overlap of sleep- and thermo-regulatory neurons, their pathways and the role of various signaling molecules. We suggest that analysis of genetically defined circuits will provide novel insights into the mechanisms underlying the coordinated regulation of sleep and body temperature in health and disease.

Septic Arthritis of the Knee in Children: A Critical Analysis Review

» Septic arthritis of the knee is the most common type of septic arthritis in children, and it may result in irreversible joint damage. » Staphylococcus aureus is the most common pathogen associated with septic arthritis, but other causative pathogens are possible in children with certain risk factors. » The diagnosis of septic arthritis of the knee is based on history and physical examination, blood tests, and arthrocentesis. » Empiric treatment with anti-staphylococcal penicillin or a first-generation cephalosporin is usually recommended but may be tailored according to local resistance patterns and clinical culture data. » Open or arthroscopic surgical debridement including extensive lavage is effective in eradicating infection, and most patients do not require additional surgical intervention.

The Potential Role of Exercise-Induced Muscle Damage in Exertional Heat Stroke

Exertional heat stroke (EHS) is a life-threatening condition that affects mainly athletes, military personnel, firefighters, and occupational workers. EHS is frequently observed in non-compensable conditions (where the body is unable to maintain a steady thermal balance) as a result of heavy heat stress and muscle contraction associated with prolonged and strenuous physical and occupational activities, resulting in central nervous system dysfunction followed by multi-organ damage and failure. Since the pathophysiology of EHS is complex and involves multiple organs and systems, any condition that changes the interrelated systems may increase the risk for EHS. It has been suggested that exercise-induced muscle damage (EIMD) can lead to thermoregulatory impairment and systemic inflammation, which could be a potential predisposing factor for EHS. In this review article, we aim to (1) address the evidence of EIMD as a predisposing factor for EHS and (2) propose a possible mechanism of how performing muscle-damaging exercise in the heat may aggravate muscle damage and subsequent risk of EHS and acute kidney injury (AKI). Such an understanding could be meaningful to minimize the risks of EHS and AKI for individuals with muscle damage due to engaging in physical work in hot environments.

Neuronal hyperexcitability is a DLK-dependent trigger of herpes simplex virus reactivation that can be induced by IL-1

Herpes simplex virus-1 (HSV-1) establishes a latent infection in neurons and periodically reactivates to cause disease. The stimuli that trigger HSV-1 reactivation have not been fully elucidated. We demonstrate HSV-1 reactivation from latently infected mouse neurons induced by forskolin requires neuronal excitation. Stimuli that directly induce neurons to become hyperexcitable also induced HSV-1 reactivation. Forskolin-induced reactivation was dependent on the neuronal pathway of DLK/JNK activation and included an initial wave of viral gene expression that was independent of histone demethylase activity and linked to histone phosphorylation. IL-1β is released under conditions of stress, fever and UV exposure of the epidermis; all known triggers of clinical HSV reactivation. We found that IL-1β induced histone phosphorylation and increased the excitation in sympathetic neurons. Importantly, IL-1β triggered HSV-1 reactivation, which was dependent on DLK and neuronal excitability. Thus, HSV-1 co-opts an innate immune pathway resulting from IL-1 stimulation of neurons to induce reactivation.

Delirium in COVID-19: A case series and exploration of potential mechanisms for central nervous system involvement

INTRODUCTION

Neuropsychiatric manifestations of the coronavirus disease 2019 (COVID-19) have been described, including anosmia, ageusia, headache, paresthesia, encephalitis and encephalopathy. Little is known about the mechanisms by which the virus causes central nervous system (CNS) symptoms, and therefore little guidance is available regarding potential workup or management options.

CASES

We present a series of four consecutive cases, seen by our psychiatry consultation service over a one-week period, each of which manifested delirium as a result of infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

DISCUSSION

The four cases highlighted here all occurred in older patients with premorbid evidence of cognitive decline. Unique features seen in multiple cases included rigidity, alogia, abulia, and elevated inflammatory markers. In all four cases, a change in mental status was the presenting symptom, and three of the four cases lacked significant respiratory symptoms. In addition to discussing unique features of the cases, we discuss possible pathophysiologic explanations for COVID-19 delirium.

CONCLUSIONS

Delirium should be recognized as a potential feature of infection with SARS-CoV-2 and may be the only presenting symptom. Based on the high rates of delirium demonstrated in prior studies, hospitals should consider adding mental status changes to the list of testing criteria. Further research is needed to determine if delirium in COVID-19 represents a primary encephalopathy heralding invasion of the CNS by the virus, or a secondary encephalopathy related to systemic inflammatory response or other factors.

EP3R-Expressing Glutamatergic Preoptic Neurons Mediate Inflammatory Fever

Fever is a common phenomenon during infection or inflammatory conditions. This stereotypic rise in body temperature (Tb) in response to inflammatory stimuli is a result of autonomic responses triggered by prostaglandin E2 action on EP3 receptors expressed by neurons in the median preoptic nucleus (MnPO^EP3R neurons). To investigate the identity of MnPO^EP3R neurons, we first used in situ hybridization to show coexpression of EP3R and the VGluT2 transporter in MnPO neurons. Retrograde tracing showed extensive direct projections from MnPO^VGluT2 but few from MnPO^Vgat neurons to a key site for fever production, the raphe pallidus. Ablation of MnPO^VGluT2 but not MnPO^Vgat neurons abolished fever responses but not changes in Tb induced by behavioral stress or thermal challenges. Finally, we crossed EP3R conditional knock-out mice with either VGluT2-IRES-cre or Vgat-IRES-cre mice and used both male and female mice to confirm that the neurons that express EP3R and mediate fever are glutamatergic, not GABAergic. This finding will require rethinking current concepts concerning the central thermoregulatory pathways based on the MnPO^EP3R neurons being GABAergic.SIGNIFICANCE STATEMENT Body temperature is regulated by the CNS. The rise of the body temperature, or fever, is an important brain-orchestrated mechanism for fighting against infectious or inflammatory disease, and is tightly regulated by the neurons located in the median preoptic nucleus (MnPO). Here we demonstrate that excitatory MnPO neurons mediate fever and examine a potential central circuit underlying the development of fever responses.

Pharmacological evidence for the use of Cissus assamica as a medicinal plant in the management of pain and pyrexia

The existing therapeutic agents for the management of pain and pyrexia are not very efficient and accompanied by numerous side effects. Thus, new effective agents are the most needed. The present study investigates bioactivities and phytochemical screening of different parts of Cissus assamica (Vitaceae), a Bangladeshi tribal medicinal plant. Three plant parts stems, leaves and roots were collected, washed, dried, powdered and then prepared for cold extraction. The methanolic stems and leaves extracts were fractioned with four and two solvents respectively. Different plant extracts were then investigated for in vivo antinociceptive activity and only methanolic leaves extract was investigated for in vivo antipyretic activity. In Swiss-albino mice, 200 and 400 mg/kg body weight doses were used for all extracts. In the peripheral antinociceptive activity, the methanolic stem extract and its dichloromethane, chloroform, pet ether fractions and methanolic roots extract at their both doses showed significant antinociceptive responses when compared to standard diclofenac sodium (60.49% inhibition). In the central antinociceptive activity, the response was found significant for methanolic stem and methanolic roots extract in their both doses compared to standard morphine. In antipyretic activity, methanolic leaves extract significantly reduced pyrexia level at 400 and 200 mg/kg body weight doses after two, three and 4 h of administration when compared to standard. So our findings indicate that this plant possesses noteworthy pharmacological activities which may be a basis for further researches to establish a possible mode of action of its different parts.

Fever control interventions versus placebo, sham or no intervention in adults: a protocol for a systematic review with meta-analysis and Trial Sequential Analysis

INTRODUCTION

Fever is an integral part of the inflammatory response and has therefore likely a physiological role in fighting infections. Nevertheless, whether fever in itself is beneficial or harmful in adults is unknown. This protocol for a systematic review aims at identifying the beneficial and harmful effects of fever control interventions in adults.

METHODS AND ANALYSIS

This protocol for a systematic review was conducted following the recommendations of Cochrane, GRADE and the eight-step assessment suggested by Jakobsen and colleagues for better validation of meta-analytical results in systematic reviews. We plan to include all relevant randomised clinical trials comparing any fever control intervention with placebo, sham or no intervention in adults. We plan to search CENTRAL, MEDLINE, Embase, LILACS, BIOSIS, CINAHL, Scopus and Web of Science Core Collection to identify relevant trials. Any eligible trial will be assessed and classified as either at high risk of bias or low risk of bias, and our primary conclusions will be based on trials at low risk of bias. We will perform our meta-analyses of the extracted data using Review Manager 5.3 and Trial Sequential Analysis. For all our outcomes, we will create a 'Summary of Findings' table based on GRADE assessments of the certainty of the evidence.

ETHICS AND DISSEMINATION

No formal approval or review of ethics is required for this systematic review as individual patient data will not be included. This systematic review has the potential to highlight (1) whether one should believe fever to be beneficial, harmful or neither in adults; (2) the existing knowledge gaps on this topic; and (3) whether the recommendations from guidelines and daily clinical practice are correct. These results will be disseminated through publication in a leading peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42019134006.

Constituents of the Edible Leaves of Melicope pteleifolia with Potential Analgesic Activity

Melicope pteleifolia has long been consumed as a popular vegetable and tea in Southeast Asian countries, including Malaysia and southern mainland China, and is effective in the treatment of colds and inflammation. In the search for active metabolites that can explain its traditional use as an antipyretic, six new phloroacetophenone derivatives (3-8) along with seven known compounds (1, 2, and 9-13) were isolated from the leaves of M. pteleifolia. Their chemical structures were confirmed by extensive spectroscopic analysis including NMR, IR, ECD, and HRMS. All compounds isolated from the leaves of M. pteleifolia (1-13) have a phloroacetophenone skeleton. Notably, the new compound 8 contains an additional cyclobutane moiety in its structure. The bioactivities of the isolated compounds were evaluated, and compounds 1, 6, and 7 inhibited tumor necrosis factor-α-induced prostaglandin E₂. Moreover, the major constituent, 3,5-di-C-β-d-glucopyranosyl phloroacetophenone (1), was found to be responsible for the antipyretic activity of M. pteleifolia based on in vivo experiments.

Fibromyalgia and its New Lessons for Neuropsychiatry

Background

Fibromyalgia (FM) is a centralized pain state that until recently has been shrouded in mystery and questionable as a disease entity in the eyes of many physicians, who considered it purely psychogenic. Fibromyalgia is now thought of as a discrete diagnosis with a clustering of symptoms characterized by central nervous system pain amplification along with anergia, memory loss, disturbances of mood, and sleep disruption. The condition is present in approximately 2% to 8% of the population.

Material/Methods

We review the link between inflammatory mechanisms and FM from a neuropsychiatric perspective.

Results

Recent studies are pointing to a neuroinflammatory etiology that may open up more effective treatment strategies in the future.

Conclusions

Better conceptualization of FM may also elucidate a neuropsychiatric understanding of how nociception, dysthymia, and suicidality co-develop and feed off one another.

Pyrogenic and neuroinflammatory properties of zymosan and its potential as an alternative to live yeast in antipyretic drug testing

Zymosan, an immunogenic cell wall extract of Saccharomyces cerevisiae has potential for use as an experimental pyrogen. However, the short-lived sickness responses noted with intraperitoneal and intra-articular administration of zymosan limits investigations on the long-term effectiveness of antipyretic drugs. Thus, there remains a need to establish an alternative route of zymosan administration that could induce long-lived fevers and inflammation. We injected male Sprague Dawley rats (250–300 g) subcutaneously with zymosan (30 or 300 mg/kg) or saline; n = 7–8. We measured core body temperature, cage activity, food intake and body mass for 24 h after injection. Blood and brain samples were collected at 2, 8, and 18 h after injection. Zymosan (300 mg/kg) induced fever, lethargy, and anorexia, which lasted for 24 h. Zymosan-induced sickness responses were accompanied by increased blood plasma levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α; activation of inflammatory transcription factors (nuclear factor (NF) for IL-6, signal transducer and activator of transcription (STAT)-3, and NF-κB) in the hypothalamus and circumventricular organs; and increased hypothalamic mRNA expression of TNF-α, IL-1β, and IL-6 and rate-limiting enzymes for prostaglandin synthesis. Our results confirm the suitability of subcutaneous administration of zymosan for screening antipyretic and anti-inflammatory drugs in rats.

Postictal syndrome: The forgotten continent. An overview of the clinical, biochemical and imaging features

Postictal syndrome (PIS) encompasses the clinical, biological, electroencephalographic (EEG) and magnetic resonance imaging (MRI) signs that follow the termination of a seizure. These signs occur as soon as the epileptic discharge ends, but might remain for a substantially long period of time, making them amenable to clinical observation. As a direct consequence, neurologists and intensivists are more frequently attending patients with PIS than during their seizure. Moreover, careful PIS documentation may help physicians to diagnose epileptic seizure from other non-epileptic disorders. Careful analysis of PIS could also be helpful to better characterize the seizure (seizure subtypes, and to some extent, the localization and/or lateralization of the seizure). This article aims to review the main clinical, biological, EEG and MRI components of PIS, discuss differential diagnoses and propose a general clinical attitude, based on the acronym "WAITTT": W for "Watch", to monitor and investigate PIS in order to provide relevant information on seizure, AIT for "Avoid Inappropriate Treatment", to underscore the risk carrying out unnecessary drug injections and intensive care procedures in the setting of a self-limited symptomatology, and TT for "Take Time", to keep in mind that time remains the clinician's best ally for treating patients with PIS.

Can neuroimmune mechanisms explain the link between ultraviolet light (UV) exposure and addictive behavior?

High ultraviolet (UV) light exposure on the skin acts as a reinforcing stimulus, increasing sun-seeking behavior and even addiction-like sun seeking behavior. However, the physiological mechanisms that underlie this process remain to be defined. Here, we propose a novel hypothesis that neuroimmune signaling, arising from inflammatory responses in UV-damaged skin cells, causes potentiated signaling within the cortico-mesolimbic pathway, leading to increased sun-seeking behaviors. This hypothesized UV-induced, skin-to-brain signaling depends upon cell stress signals, termed alarmins, reaching the circulation, thereby triggering the activation of innate immune receptors, such as toll-like receptors (TLRs). This innate immune response is hypothesized to occur both peripherally and centrally, with the downstream signaling from TLR activation affecting both the endogenous opioid system and the mesolimbic dopamine pathway. As both neurotransmitter systems play a key role in the development of addiction behaviors through their actions at key brain regions, such as the nucleus accumbens (NAc), we hypothesize a novel connection between UV-induced inflammation and the activation of pathways that contribute to the development of addiction. This paper is a review of the existing literature to examine the evidence which suggests that chronic sun tanning resembles a behavioral addiction and proposes a novel pathway by which persistent sun-seeking behavior could affect brain neurochemistry in a manner similar to that of repeated drug use.

Cytokine profiling and post-transfusion haemoglobin increment in patients with haematological diseases

BACKGROUND AND OBJECTIVES

In a previous pilot study, we demonstrated significantly lower haemoglobin (Hb) increment after red-blood-cell (RBC) transfusions in febrile patients compared to patients without fever. The aim of this study was to examine associations between inflammatory mediators and post-transfusion haemoglobin increment in patients with haematological diseases.

MATERIALS AND METHODS

Twenty-seven patients (eight women, 19 men), median age 56 years receiving RBC transfusion, were included in the study. Hb increment per unit transfused was corrected for estimated patient blood volume and the amount of Hb transfused. A wide spectrum of inflammatory mediators was determined by multiplex technology. Association between post-transfusion haemoglobin increment, plasma inflammatory mediators and patient characteristics was analysed using a mixed linear regression model.

RESULTS

Febrile patients had significantly lower corrected Hb increment, significantly increased values of IL-6, IL-8, IL-10 and G-CSF, significantly reduced levels of CCL5 and CXCL10, and significantly higher pretransfusion levels of CRP. There was a significant association between pretransfusion CRP levels and corrected Hb increment for the whole patient cohort, but not within each of the two groups. Results demonstrated an association between haemoglobin increment, fever and inflammatory mediators. Febrile patients had a significantly lower corrected Hb increment compared to nonfebrile patients, when adjusting for mediators. When fever was kept constant, a significant negative association between haemoglobin increment and the proinflammatory mediators IL-6 and IL-8 was observed.

CONCLUSION

Both fever and the inflammatory mediators IL-6 and IL-8 were negatively associated with post-transfusion haemoglobin increment.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Neural Mechanisms of Inflammation-Induced Fever

Fever is a common symptom of infectious and inflammatory disease. It is well-established that prostaglandin E2 is the final mediator of fever, which by binding to its EP3 receptor subtype in the preoptic hypothalamus initiates thermogenesis. Here, we review the different hypotheses on how the presence of peripherally released pyrogenic substances can be signaled to the brain to elicit fever. We conclude that there is unequivocal evidence for a humoral signaling pathway by which proinflammatory cytokines, through their binding to receptors on brain endothelial cells, evoke fever by eliciting prostaglandin E2 synthesis in these cells. The evidence for a role for other signaling routes for fever, such as signaling via circumventricular organs and peripheral nerves, as well as transfer into the brain of peripherally synthesized prostaglandin E2 are yet far from conclusive. We also review the efferent limb of the pyrogenic pathways. We conclude that it is well established that prostaglandin E2 binding in the preoptic hypothalamus produces fever by disinhibition of presympathetic neurons in the brain stem, but there is yet little understanding of the mechanisms by which factors such as nutritional status and ambient temperature shape the response to the peripheral immune challenge.

Targeted Temperature Management in Brain Injured Patients

Evidence from animal models indicates that lowering temperature by a few degrees can produce substantial neuroprotection. In humans, hypothermia has been found to be neuroprotective with a significant impact on mortality and long-term functional outcome only in cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Clinical trials have explored the potential role of maintaining normothermia and treating fever in critically ill brain injured patients. This review concentrates on basic concepts to understand the physiologic interactions of thermoregulation, effects of thermal modulation in critically ill patients, proposed mechanisms of action of temperature modulation, and practical aspects of targeted temperature management.

Neurogenic inflammation and its role in migraine

The etiology of migraine pain involves sensitized meningeal afferents that densely innervate the dural vasculature. These afferents, with their cell bodies located in the trigeminal ganglion, project to the nucleus caudalis, which in turn transmits signals to higher brain centers. Factors such as chronic stress, diet, hormonal fluctuations, or events like cortical spreading depression can generate a state of "sterile inflammation" in the intracranial meninges resulting in the sensitization and activation of trigeminal meningeal nociceptors. This sterile inflammatory phenotype also referred to as neurogenic inflammation is characterized by the release of neuropeptides (such as substance P, calcitonin gene related peptide) from the trigeminal innervation. This release leads to vasodilation, plasma extravasation secondary to capillary leakage, edema, and mast cell degranulation. Although neurogenic inflammation has been observed and extensively studied in peripheral tissues, its role has been primarily investigated in the genesis and maintenance of migraine pain. While some aspects of neurogenic inflammation has been disregarded in the occurrence of migraine pain, targeted analysis of factors have opened up the possibilities of a dialogue between the neurons and immune cells in driving such a sterile neuroinflammatory state in migraine pathophysiology.

Are infectious diseases and microbiology new fields for thermal therapy research?

Antimicrobial chemotherapy and surgery are classical methods for treating infectious diseases. However, there is a need for alternative methods to cure infections caused by antibiotic-resistant pathogens, recurrent or chronic infections, and unreachable local infections in which the use of drugs or surgery is anatomically and physically restricted. Several micro-organisms are known to be sensitive to mild hyperthermia, and this sensitivity is one of the potential benefits proposed for the host during an episode of fever. Additionally, some immunological or biophysical changes occur during hyperthermia. These changes may be useful for eliminating thermo-susceptible microbial pathogens using local heat therapy. There are several experimental studies proposing the use of hyperthermia to treat local infections. The infected organs or tissues may be heated up to a temperature that can inhibit invading microorganisms. Here, it is hypothesised that local heat therapy may become an alternative or adjuvant method for curing local infections. Here, we highlight the potential for local hyperthermia in the treatment of bacterial infections caused by thermo-susceptible pathogens in a systematic plan. If the proposed thermal-microbiology concepts and local thermal therapies can be adapted to clinical microbiology and infectiology, new medical fields, such as thermo-microbiology and thermo-infectiology, may be created in the future.

Fevers in Adult Lupus Patients

Variability in systemic lupus erythematosus (SLE) disease manifestations is well recognized. Lupus disease activity can range from mild to severe. Fever is a common manifestation of SLE and occurs in 36%-86% of patients. In the Modified Systemic Lupus Erythematosus Disease Activity Index (M-SLEDAI), fever is taken into account as disease activity scoring. Assessment of lupus patients with fever is an important diagnostic challenge, since the initial clinical presentation of a patient with lupus is very similar to the acute febrile phase of an infection. The attribution of fever to SLE holds only after other causes are excluded.

In vivo evaluation of antipyretic effects of some homeopathic ultra-high dilutions on Baker's yeast-induced fever on Similia principle

BACKGROUND

Homeopathy is a controversial alternative system of medicine. The action of homeopathic medicines is considered slow and it is assumed that homeopathic medicines are ineffective in acute conditions such as fever.

OBJECTIVE

In the present study, effects of 3 homeopathic medicines on baker's yeast induced fever were investigated.

MATERIALS AND METHODS

42 local strain rabbits were equally divided into 7 groups. Normal saline was orally administered to group 1 (normal control) rabbits without fever induction. Group 2 underwent baker's yeast-induced fever (negative control). Groups 3, 4, 5, 6 and 7 underwent baker's yeast-induced fever and were thereafter treated orally with paracetamol, Nux vomica 200C and 1M, Calcarea phos 200C and Belladonna 200C respectively. Rectal temperature was checked hourly. The abdominal writhing and frequency of loose stools were also monitored. ANOVA was applied for checking statistical significance. p ≤ 0.05 was considered significant.

RESULTS

The rectal temperature increased significantly (p < 0.05) in the negative control group when compared to the normal control. Abdominal writhing and loose stools monitoring showed increased writhing and loose stools frequency of group 2, 3, 6 and 7 rabbits. However, treatment of paracetamol significantly reduced rectal temperature. Group 4 & 5 showed significant reduction of rectal temperature together with abatement of abdominal writhing and loose stools.

CONCLUSION

N. vomica ultra-high dilutions have normalized rectal temperature and prevented the abdominal writhing and loose stools in baker's yeast-induced fever model of rabbits. It could be due to antidotal activity of N. vomica ultra-high dilutions. Therefore, N. vomica ultra-high dilutions can be useful antipyretic agents and can treat conditions associated with gastrointestinal symptoms. However, fixed conclusion can't be asserted due to caveat of small sample size.

Design of a Remote System for Monitoring Children’s Body Temperature

More and more health-monitoring devices are appearing on the market for both anticipating and preventing crucial health conditions. We describe a minimally invasive device for monitoring children’s body temperature easily and effectively. Development of the device was divided into two stages: (1) a product specification process, which included detailed analysis of the problem, competitive analysis, and consumer surveys; and (2) development and optimization of the product, which included testing the product prototype with target users. Usability and safety were central considerations for developing the product to ensure successful use by children. User feedback testing showed that the final version of the product was well received by the target user group.

Effects of homoeopathic ultrahigh dilutions of Aconitum napellus on Baker's yeast-induced fever in rabbits

OBJECTIVE

To evaluate the effects of homoeopathic ultrahigh dilutions of Aconitum napellus in Baker's yeast-induced fever in rabbits.

METHODS

Rabbits were divided into 4 groups and each group contained 6 rabbits. Baker's yeast suspension (20%) was injected subcutaneously. After fever induction, paracetamol and homoeopathic ultrahigh dilutions (A. napellus 200c and 1 000c) were given orally. Rectal temperature was measured with digital thermometer hourly.

RESULTS

Fever was induced in all the rabbits after 4 hours of Baker's yeast administration. A. napellus 200c and 1000c significantly reduced the temperature (P < 0.05). In positive control, temperature decrease was more significant (P < 0.001).

CONCLUSION

The above findings indicate the effectiveness of ultrahigh dilutions of A. napellus in Baker's yeast-induced fever in rabbits. However, the effects were slower and less significant than standard medicine. Moreover, future research is required to know their mechanism of reducing temperature.

Tolerance of infection: A role for animal behavior, potential immune mechanisms, and consequences for parasite transmission

Infected organisms can resist or tolerate infection, with tolerance of infection defined as minimizing per-parasite reductions in fitness. Although tolerance is well studied in plants, researchers have only begun to probe the mechanisms and transmission consequences of tolerance in animals. Here we suggest that research on tolerance in animals would benefit from explicitly incorporating behavior as a component of tolerance, given the importance of behavior for host fitness and parasite transmission. We propose two distinct manifestations of tolerance in animals: tissue-specific tolerance, which minimizes fitness losses due to tissue damage during infection, and behavioral tolerance, which minimizes fitness losses by maintaining normal, fitness-enhancing behaviors during infection. Here we briefly review one set of potential immune mechanisms underlying both responses in vertebrate animals: inflammation and its associated signaling molecules. Inflammatory responses, including broadly effective resistance mechanisms like the production of reactive oxygen species, can incur severe costs in terms of damage to a host's own tissues, thereby reducing tissue-specific tolerance. In addition, signaling molecules involved in these responses facilitate stereotypical behavioral changes during infection, which include lethargy and anorexia, reducing normal behaviors and behavioral tolerance. We consider how tissue-specific and behavioral tolerance may vary independently or in conjunction and outline potential consequences of such covariation for the transmission of infectious diseases. We put forward the distinction between tissue-specific and behavioral tolerance not as a definitive framework, but to help stimulate and broaden future research by considering animal behavior as intimately linked to the mechanisms and consequences of tolerance in animals.

Magnitude of temperature elevation is associated with neurologic and survival outcomes in resuscitated cardiac arrest patients with postrewarming pyrexia

PURPOSE

Avoidance of pyrexia is recommended in resuscitation guidelines, including after treatment with targeted temperature management (TTM). Which aspects of postresuscitation pyrexia are harmful and modifiable have not been conclusively determined.

MATERIALS AND METHODS

This retrospective multicenter registry study collected serial temperatures during 72 hours postrewarming to assess the relationship between 3 aspects of pyrexia (maximum temperature, pyrexia duration, timing of first pyrexia) and neurologic outcome (primary) and survival (secondary) at hospital discharge. Adult TTM-treated patients from 13 US hospitals between 2005 and 2015 were included.

RESULTS

One hundred seventy-nine of 465 patients had at least 1 temperature greater than or equal to 38°C. Pyrexic temperatures were associated with better survival than nonpyrexic temperatures (adjusted odds ratio [aOR], 1.54; 95% confidence interval [CI], 1.00-2.35). Higher maximum temperature was associated with worse outcome (neurologic aOR, 0.30 [95% CI, 0.10-0.84]; survival aOR, 0.25 [95% CI, 0.10-0.59]) in pyrexic patients. There was no significant relationship between pyrexia duration and outcomes unless duration was calculated as hours greater than or equal to 38.8°C, when longer duration was associated with worse outcomes (neurologic aOR, 0.86 [95% CI, 0.75-1.00]; survival aOR, 0.82 [95% CI, 0.72-0.93]).

CONCLUSIONS

In postarrest TTM-treated patients, pyrexia was associated with increased survival. Patients experiencing postrewarming pyrexia had worse outcomes at higher temperatures. Longer pyrexia duration was associated with worse outcomes at higher temperatures.

Review: Infection, fever, and exogenous and endogenous pyrogens: some concepts have changed

For many years, it was thought that bacterial products caused fever via the intermediate production of a host-derived, fever-producing molecule, called endogenous pyrogen (EP). Bacterial products and other fever-producing substances were termed exogenous pyrogens. It was considered highly unlikely that exogenous pyrogens caused fever by acting directly on the hypothalamic thermoregulatory center since there were countless fever-producing microbial products, mostly large molecules, with no common physical structure. In vivo and in vitro, lipopolysaccharides (LPSs) and other microbial products induced EP, subsequently shown to be interleukin-1 (IL-1). The concept of the `endogenous pyrogen' cause of fever gained considerable support when pure, recombinant IL-1 produced fever in humans and in animals at subnanomolar concentrations. Subsequently, recombinant tumor necrosis factor-α (TNF-α), IL-6 and other cytokines were also shown to cause fever and EPs are now termed pyrogenic cytokines. However, the concept was challenged when specific blockade of either IL-1 or TNF activity did not diminish the febrile response to LPS, to other microbial products or to natural infections in animals and in humans. During infection, fever could occur independently of IL-1 or TNF activity. The cytokine-like property of Toll-like receptor (TLR) signal transduction provides an explanation by which any microbial product can cause fever by engaging its specific TLR on the vascular network supplying the thermoregulatory center in the anterior hypothalamus. Since fever induced by IL-1, TNF-α, IL-6 or TLR ligands requires cyclooxygenase-2, production of prostaglandin E2 (PGE 2) and activation of hypothalamic PGE2 receptors provides a unifying mechanism for fever by endogenous and exogenous pyrogens. Thus, fever is the result of either cytokine receptor or TLR triggering; in autoimmune diseases, fever is mostly cytokine mediated whereas both cytokine and TLR account for fever during infection.

Antipyretic Effect of Clonidine in Intensive Care Unit Patients: A Nested Observational Study

Fever in the intensive care unit (ICU) is usually an adaptive response to infection or inflammation. Pharmacological intervention is often required in addition to addressing the underlying causes of fever. Animal studies have examined the antipyretic effect of clonidine; however, to our knowledge there are no clinical data available in humans. The observation of an antipyretic effect of clonidine was made during a single-center randomized control trial that was designed to study the effect of clonidine addition to the commonly used sedative agents in mechanically ventilated ICU patients. Forty patients 18 years or older on mechanical ventilation for 3 days or longer were randomized into 2 groups receiving clonidine and placebo. In addition to the usual sedation/analgesia, patients in the clonidine arm received enteral clonidine in doses of 0.1 mg 3 times a day (TID), which was increased to 0.2 mg TID if the hemodynamics remained stable. Vital signs, laboratory data, all cultures, and daily ICU events were recorded. The odds ratio of temperature higher than 38.3°C was 3.96 times higher in the placebo group, after adjustment for the illness severity and the time of follow-up (P = .049). A lower temperature (0.52°C) was observed in the clonidine group after adjustment for the time of follow-up (P = .006). Our report is the first of its kind in humans that demonstrates possible antipyretic properties of enteral clonidine in the critically ill intensive care unit patient.

Central neural control of thermoregulation and brown adipose tissue

Central neural circuits orchestrate the homeostatic repertoire that maintains body temperature during environmental temperature challenges and alters body temperature during the inflammatory response. This review summarizes the experimental underpinnings of our current model of the CNS pathways controlling the principal thermoeffectors for body temperature regulation: cutaneous vasoconstriction controlling heat loss, and shivering and brown adipose tissue for thermogenesis. The activation of these effectors is regulated by parallel but distinct, effector-specific, core efferent pathways within the CNS that share a common peripheral thermal sensory input. Via the lateral parabrachial nucleus, skin thermal afferent input reaches the hypothalamic preoptic area to inhibit warm-sensitive, inhibitory output neurons which control heat production by inhibiting thermogenesis-promoting neurons in the dorsomedial hypothalamus that project to thermogenesis-controlling premotor neurons in the rostral ventromedial medulla, including the raphe pallidus, that descend to provide the excitation of spinal circuits necessary to drive thermogenic thermal effectors. A distinct population of warm-sensitive preoptic neurons controls heat loss through an inhibitory input to raphe pallidus sympathetic premotor neurons controlling cutaneous vasoconstriction. The model proposed for central thermoregulatory control provides a useful platform for further understanding of the functional organization of central thermoregulation and elucidating the hypothalamic circuitry and neurotransmitters involved in body temperature regulation.