Hypothesis: Fever control, a niche for alpha-2 agonists in the setting of septic shock and severe acute respiratory distress syndrome?

Dexmedetomidine for Reducing Mortality in Patients With Septic Shock A Randomized Controlled Trial (DecatSepsis)

BACKGROUND

Sepsis, especially septic shock, and its complications have been linked to the hyperadrenergic stress response.

RESEARCH QUESTION

Does decatecholaminization with dexmedetomidine lower the in-hospital mortality in patients with septic shock?

STUDY DESIGN AND METHODS

This open-label randomized controlled trial assessed the effects of a heart rate (HR)-calibrated dexmedetomidine infusion on in-hospital mortality in patients with septic shock and HR of > 90 beats/min, regardless of whether they are receiving mechanical ventilation. Dexmedetomidine was infused for 48 h to maintain the HR at 60 to 90 beats/min. Mechanically ventilated patients received conventional sedation in both groups. Other outcomes were the norepinephrine equivalent dose, the need for additional vasopressor, Acute Physiology and Chronic Health Evaluation (APACHE) II score, persistent atrial fibrillation (AF), and C-reactive protein (CRP) level.

RESULTS

In 90 patients of either sex, dexmedetomidine reduced the mean HR over the first 3 days in the ICU by 11.2 beats/min (95% CI, -17 to -5 beats/min; P < .001). The in-hospital mortality risk ratio (RR) was 0.68 (95% CI, 0.43-1.07; P = .091). The dexmedetomidine group received a norepinephrine equivalent dose of 0.55 μm/kg/min (interquartile range [IQR], 0.37-0.82 μm/kg/min) vs 0.61 μm/kg/min (IQR, 0.47-0.89 μm/kg/min; P = .121). Dexmedetomidine reduced the epinephrine infusion rescue (relative risk reduction, 0.6; 95% CI, 0.06-0.93; P = .025). The RR of persistent AF was 0.47 (95% CI, 0.21-0.99; P = .05). Dexmedetomidine reduced the median APACHE II score on the third day by -6 (95% CI, -10 to -2; P = .003) and the mean CRP concentration by -40 mg/dL (95% CI, -78 to -3.4 mg/dL; P = .033).

INTERPRETATION

The study was underpowered to detect a reduction in in-hospital mortality or norepinephrine equivalent dose in patients with septic shock with dexmedetomidine. However, dexmedetomidine may reduce epinephrine infusion rescue, persistent AF, the APACHE II score, and CRP.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT05283083; URL: www.

CLINICALTRIALS

gov.

Alpha-2-adrenergic agonists reduce resting energy expenditure in humans during external cooling

Intravenous alpha-2-adrenergic receptor agonists reduce energy expenditure and lower the temperature when shivering begins in humans, allowing a decrease in core body temperature. Because there are few data about similar effects from oral drugs, we tested whether single oral doses of the sedative dexmedetomidine (1 µg/kg sublingual or 4 µg/kg swallowed) or the muscle relaxant tizanidine (8 mg or 16 mg), combined with surface cooling, reduce energy expenditure and core body temperature in humans. A total of 26 healthy participants completed 41 one-day laboratory studies measuring core body temperature using an ingested telemetry capsule and measuring energy expenditure using indirect calorimetry for up to 6 hours after drug ingestion. Dexmedetomidine induced a median 13% - 19% peak reduction and tizanidine induced a median 15% - 22% peak reduction in energy expenditure relative to baseline. Core body temperature decreased a median of 0.5°C - 0.6°C and 0.5°C - 0.7°C respectively. Decreases in temperature occurred after peak reductions in energy expenditure. Energy expenditure increased with a decrease in core temperature in control participants but did not occur after 4 µg/kg dexmedetomidine or 16 mg tizanidine. Plasma levels of dexmedetomidine but not tizanidine were related to mean temperature change. Decreases in heart rate, blood pressure, respiratory rate, cardiac stroke volume index, and cardiac index were associated with the change in metabolic rate after higher drug doses. We conclude that both oral dexmedetomidine and oral tizanidine reduce energy expenditure and allow decrease in core temperature in humans.

Dexmedetomidine Combined with Low-Dose Norepinephrine Continuous Pumping to Prevent Hypotension after Cesaresan Section: A Randomized Controlled Trial

Objective

The aim of the study is to explore the clinical effect of dexmedetomidine combined with low-dose norepinephrine (NE) continuous pumping in preventing supine hypotension.

Methods

A total of 160 puerperaes who underwent elective cesarean section were selected. The puerperaes were equally divided into S group (saline), D group (dexmedetomidine), N group (norepinephrine), and DN group (dexmedetomidine combined with norepinephrine) by a random number table method. Apgar scores and umbilical cord venous blood gas values were recorded at 1 and 5 minutes.

Results

There were no statistically significant differences in the age, gestational age, body mass index, bleeding volume, fluid supplement volume, Apgar scores of new borns at the 1st and 5th minute, the blood gas values of umbilical cord arterial and venous in the four groups (P > 0.05). Compared with the S group, the incidence of supine hypotension, the number of NE supplements, the supplementary doses of NE, and the incidence of adverse reactions were significantly reduced in the D, N, and DN groups after spinal anesthesia (P < 0.05). Compared with group D, the incidence of supine hypotension, the number of additional NE, additional dose of NE, and the incidence of adverse reactions in the DN group after spinal anesthesia were significantly reduced (P < 0.05). Compared with the N group, the incidence of supine hypotension, the number of additional NE, the additional dose of NE, and the incidence of adverse reactions in the DN group after spinal anesthesia were significantly reduced (P < 0.05).

Conclusion

Dexmedetomidine combined with continuous pumping of low-dose norepinephrine can effectively prevent the occurrence of supine hypotension, reduce the occurrence of other adverse reactions, and have no obvious adverse effects on neonates. Registration. Chinese Clinical Trial Registry (https://www.chictr.org.cn/enIndex.aspx; ChiCTR2000040979).

Potential for Further Mismanagement of Fever During COVID-19 Pandemic: Possible Causes and Impacts

Fever remains an integral part of acute infectious diseases management, especially for those without effective therapeutics, but the widespread myths about "fevers" and the presence of confusing guidelines from different agencies, which have heightened during the coronavirus disease 2019 (COVID-19) pandemic and are open to alternate interpretation, could deny whole populations the benefits of fever. Guidelines suggesting antipyresis for 37.8-39°C fever are concerning as 39°C boosts the protective heat-shock and immune response (humoral, cell-mediated, and nutritional) whereas ≥40°C initiates/enhances the antiviral responses and restricts high-temperature adapted pathogens, e.g., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), strains of influenza, and measles. Urgent attention is accordingly needed to address the situation because of the potential public health consequences of the existence of conflicting guidelines in the public domain. We have in this article attempted to restate the benefits of fever in disease resolution, dispel myths, and underline the need for alignment of national treatment guidelines with that of the WHO, to promote appropriate practices and reduce the morbidity and mortality from infectious diseases, such as COVID-19.

How should dexmedetomidine and clonidine be prescribed in the critical care setting?

Cardiac, ventilatory and kidney management in the critical care setting has been optimized over the past decades. Cognition and sedation represent one of the last remaning challenges. As conventional sedation is suboptimal and as the sedation evoked by alpha-2 adrenergic agonists ("cooperative" sedation with dexmedetomidine, clonidine or guanfacine) represents a valuable alternative, this manuscript covers three practical topics for which evidence-based medicine is lacking: a) Switching from conventional to cooperative sedation ("switching"): the short answer is the abrupt withdrawal of conventional sedation, immediate implementation of alpha-2 agonist infusion and the use of "rescue sedation" (midazolam bolus[es]) or "breakthrough sedation" (haloperidol bolus[es]) to stabilize cooperative sedation. b) Switching from conventional to cooperative sedation in unstable patients (e.g., refractory delirium tremens, septic shock, acute respiratory distress syndrome, etc.): to avoid hypotension and bradycardia evoked by sympathetic deactivation, the short answer is to maintain the stroke volume through volume loading, vasopressors and inotropes. c) To avoid these switches and associated difficulties, alpha-2 agonists may be considered first-line sedatives. The short answer is to administer alpha-2 agonists slowly from admission or endotracheal intubation up to stabilized cooperative sedation. The "take home" message is as follows: a) alpha-2 agonists are jointly sympathetic deactivators and sedative agents; b) sympathetic deactivation implies maintaining the stroke volume and iterative assessment of volemia. Evidence-based medicine should document our propositions.

Is the Sympathetic System Detrimental in the Setting of Septic Shock, with Antihypertensive Agents as a Counterintuitive Approach? A Clinical Proposition

Mortality in the setting of septic shock varies between 20% and 100%. Refractory septic shock leads to early circulatory failure and carries the worst prognosis. The pathophysiology is poorly understood despite studies of the microcirculatory defects and the immuno-paralysis. The acute circulatory distress is treated with volume expansion, administration of vasopressors (usually noradrenaline: NA), and inotropes. Ventilation and anti-infectious strategy shall not be discussed here. When circulation is considered, the literature is segregated between interventions directed to the systemic circulation vs. interventions directed to the micro-circulation. Our thesis is that, after stabilization of the acute cardioventilatory distress, the prolonged sympathetic hyperactivity is detrimental in the setting of septic shock. Our hypothesis is that the sympathetic hyperactivity observed in septic shock being normalized towards baseline activity will improve the microcirculation by recoupling the capillaries and the systemic circulation. Therefore, counterintuitively, antihypertensive agents such as beta-blockers or alpha-2 adrenergic agonists (clonidine, dexmedetomidine) are useful. They would reduce the noradrenaline requirements. Adjuncts (vitamins, steroids, NO donors/inhibitors, etc.) proposed to normalize the sepsis-evoked vasodilation are not reviewed. This itemized approach (systemic vs. microcirculation) requires physiological and epidemiological studies to look for reduced mortality.

Mortality prediction for patients with acute respiratory distress syndrome based on machine learning: a population-based study

Background

Traditional scoring systems for patients' outcome prediction in intensive care units such as Oxygenation Saturation Index (OSI) and Oxygenation Index (OI) may not reliably predict the clinical prognosis of patients with acute respiratory distress syndrome (ARDS). Thus, none of them have been widely accepted for mortality prediction in ARDS. This study aimed to develop and validate a mortality prediction method for patients with ARDS based on machine learning using the Medical Information Mart for Intensive Care (MIMIC-III) and Telehealth Intensive Care Unit (eICU) Collaborative Research Database (eICU-CRD) databases.

Methods

Patients with ARDS were selected based on the Berlin definition in MIMIC-III and eICU-CRD databases. The APPS score (using age, PaO₂/FiO₂, and plateau pressure), Simplified Acute Physiology Score II (SAPS-II), Sepsis-related Organ Failure Assessment (SOFA), OSI, and OI were calculated. With MIMIC-III data, a mortality prediction model was built based on the random forest (RF) algorithm, and the performance was compared to those of existing scoring systems based on logistic regression. The performance of the proposed RF method was also validated with the combined MIMIC-III and eICU-CRD data. The performance of mortality prediction was evaluated by using the area under the receiver operating characteristics curve (AUROC) and performing calibration using the Hosmer-Lemeshow test.

Results

With the MIMIC-III dataset (308 patients, for comparisons with the existing scoring systems), the RF model predicted the in-hospital mortality, 30-day mortality, and 1-year mortality with an AUROC of 0.891, 0.883, and 0.892, respectively, which were significantly higher than those of the SAPS-II, APPS, OSI, and OI (all P<0.001). In the multi-source validation (the combined dataset of 2,235 patients in MIMIC-III and 331 patients in eICU-CRD), the RF model achieved an AUROC of 0.905 and 0.736 for predicting in-hospital mortality for the MIMIC-III and eICU-CRD datasets, respectively. The calibration plots suggested good fits for our RF model and these scoring systems for predicting mortality. The platelet count and lactate level were the strongest predictive variables for predicting in-hospital mortality.

Conclusions

Compared to the existing scoring systems, machine learning significantly improved performance for predicting ARDS mortality. Validation with multi-source datasets showed a relatively robust generalisation ability of our prediction model.

Fever Associated With Dexmedetomidine in Adult Acute Care Patients: A Systematic Review of the Literature

Dexmedetomidine-associated fever has been reported in the literature and can lead to lengthy workups and unnecessary antibiotic exposure. We conducted a systematic review to evaluate and describe the evidence of fever or hyperthermia caused by dexmedetomidine in adult patients. Data sources included PubMed/MEDLINE, EMBASE, CINAHL, and Web of Sciences. English-language studies of any design published from inception through April 2020 including conference abstracts were included. The target population was hospitalized adult patients. Quality of evidence was determined based on GRADE recommendations and risk of bias assessed using the Evidence Project Risk of Bias tool. Naranjo scores were assessed to determine the likeliness of adverse event being caused by dexmedetomidine. All data were extracted independently and with the guidance of a medical librarian. Four hundred and eighty-eight total citations were found on formal search, with 329 left after removal of duplicates. Independent record screening was performed, leaving 17 citations including 4 retrospective cohort studies, 1 case series, and 12 case reports. Quality of evidence ranged from very low to low for identified analyses. Evidence with patient-level data (case reports and series) were combined to establish a cohort for descriptive results. The median Naranjo score was 4 (range, 3 to 8), and dexmedetomidine doses ranged from 0.1 to 2 μg·h/kg. Obesity and cardiac surgery appear to be significant risk factors. Dexmedetomidine-associated fever appears uncommon, but the true incidence is unknown. Clinicians should keep dexmedetomidine-associated fever in their differential, and stewardship programs should consider assessing for this adverse effect in their patient monitoring.

Clinical Practice: Should we Radically Alter our Sedation of Critical Care Patients, Especially Given the COVID-19 Pandemics?

The high number of patients infected with the SARS-CoV-2 virus requiring care for ARDS puts sedation in the critical care unit (CCU) to the edge. Depth of sedation has evolved over the last 40 years (no-sedation, deep sedation, daily emergence, minimal sedation, etc.). Most guidelines now recommend determining the depth of sedation and minimizing the use of benzodiazepines and opioids. The broader use of alpha-2 adrenergic agonists ('alpha-2 agonists') led to sedation regimens beginning at admission to the CCU that contrast with hypnotics+opioids ("conventional" sedation), with major consequences for cognition, ventilation and circulatory performance. The same doses of alpha-2 agonists used for 'cooperative' sedation (ataraxia, analgognosia) elicit no respiratory depression but modify the autonomic nervous system (cardiac parasympathetic activation, attenuation of excessive cardiac and vasomotor sympathetic activity). Alpha-2 agonists should be selected only in patients who benefit from their effects ('personalized' indications, as opposed to a 'one size fits all' approach). Then, titration to effect is required, especially in the setting of systemic hypotension and/or hypovolemia. Since no general guidelines exist for the use of alpha-2 agonists for CCU sedation, our clinical experience is summarized for the benefit of physicians in clinical situations in which a recommendation might never exist (refractory delirium tremens; unstable, hypovolemic, hypotensive patients, etc.). Because the physiology of alpha-2 receptors and the pharmacology of alpha-2 agonists lead to personalized indications, some details are offered. Since interactions between conventional sedatives and alpha-2 agonists have received little attention, these interactions are addressed. Within the existing guidelines for CCU sedation, this article could facilitate the use of alpha-2 agonists as effective and safe sedation while awaiting large, multicentre trials and more evidence-based medicine.

Moderate Fever Cycles as a Potential Mechanism to Protect the Respiratory System in COVID-19 Patients

Mortality in COVID-19 patients predominantly results from an acute respiratory distress syndrome (ARDS), in which lungs alveolar cells undergo programmed cell death. Mortality in a sepsis-induced ARDS rat model is reduced by adenovirus over-expression of the HSP70 chaperone. A natural rise of body temperature during mild fever can naturally accumulate high cellular levels of HSP70 that can arrest apoptosis and protect alveolar lung cells from inflammatory damages. However, beyond 1-2 h of fever, no HSP70 is being further produced and a decreased in body temperature required to the restore cell's ability to produce more HSP70 in a subsequent fever cycle. We suggest that antipyretics may be beneficial in COVID-19 patients subsequent to several hours of mild (<38.8°C) advantageous fever, allowing lung cells to accumulate protective HSP70 against damages from the inflammatory response to the virus SARS-CoV-2. With age, the ability to develop fever and accumulate HSP70 decreases. This could be ameliorated, when advisable to do so, by thermotherapies and/or physical training.

Alpha2-adrenergic receptor agonists prevent emotional hyperthermia

Emotionally significant stimuli, including potential threats from the external environment, trigger an increase in body temperature, a response known as emotional hyperthermia. Sympathetically-mediated brown adipose tissue (BAT) thermogenesis contributes substantially to this hyperthermic response. The systemic administration of α₂-adrenergic agonists is known to inhibit both febrile and shivering responses. In the present study, we investigated whether systemic administration of clonidine, a α₂-adrenoceptor agonist, attenuates the emotional hyperthermia evoked in conscious unrestrained rats suddenly confronted with a second (intruder) rat, itself confined to a small cage. Pre-implanted thermistors were used to measure BAT and body temperature in conscious, freely moving, male Sprague-Dawley rats. The rats were pre-treated with intraperitoneally administered vehicle (Ringer solution) or clonidine (1, 10 and 100 µg/kg). Clonidine, in a dose-dependent manner, reduced the intruder-elicited increases in BAT (log-dose linear regression F(1,16) = 9.52, R² = 0.37, P < 0.01) and body temperature (F(1,16) = 6.48, R² = 0.29, P < 0.05). We also investigated, in anesthetized rats, whether systemic clonidine administration inhibits BAT sympathetic nerve discharge evoked via activation of neurons in the lateral habenula (LHb) - a nucleus involved in the regulation of emotional hyperthermia. In anesthetized rats, clonidine abolished the BAT sympathetic nerve discharges elicited via bicuculline-mediated disinhibition of the LHb. These results suggest that activation of central α₂-adrenergic receptors attenuates the process of emotional hyperthermia by reduction of BAT thermogenesis.