Respiratory, metabolic and hemodynamic effects of clonidine in ventilated patients presenting with withdrawal syndrome

Incidence and clinical manifestation of iatrogenic opioid withdrawal syndrome in mechanically ventilated patients

OBJECTIVE

The incidence of iatrogenic opioid withdrawal syndrome (IOWS) in mechanically ventilated adults has been questioned in settings driven by analgosedation strategies. This study aimed to describe the incidence, risk factors and clinical impact of IOWS in mechanically ventilated adults.

METHODS

This prospective, observational study was performed between 1 January and 31 August 2018. IOWS was identified based on the presence of at least three signs or symptoms according to the Diagnostic and Statistical Manual 5th edition (DSM-5) criteria after opioid discontinuation or rate reduction. Incidence of IOWS, patient characteristics, opioid administration, and the impact of IOWS on the duration of mechanical ventilator and length of stay in the intensive care unit (ICU) were collected.

RESULTS

Thirteen out of 55 patients (23.6%) manifested withdrawal symptoms. Two patients in the non-withdrawal group also developed hypertensive urgency after opioid discontinuation. Patients who received rapid once-daily weaning, especially rate reduction more than 50 µg as fentanyl equivalent per hour, were associated with IOWS. However, there was no statistically significant difference in ventilator-free days and ICU-free days.

CONCLUSIONS

These findings showed that approximately one-fourth of mechanically ventilated patients who received opioid infusion experienced IOWS. Monitoring for IOWS is recommended especially in patients who received rapid weaning rate of opioids. Future studies to develop IOWS assessment tools with the change of hemodynamic parameters should be performed.

TRIAL REGISTRATION

This trial was registered in ClinicalTrials.gov: identifier NCT03374722, date of registration 15 December 2018.

Strategies for the Prevention and Treatment of Iatrogenic Withdrawal from Opioids and Benzodiazepines in Critically Ill Neonates, Children and Adults: A Systematic Review of Clinical Studies

BACKGROUND

Critically ill patients are at high risk of iatrogenic withdrawal syndrome (IWS), due to exposure to high doses or prolonged periods of opioids and benzodiazepines.

PURPOSE

To examine pharmacological management strategies designed to prevent and/or treat IWS from opioids and/or benzodiazepines in critically ill neonates, children and adults.

METHODS

We included non-randomised studies of interventions (NRSI) and randomised controlled trials (RCTs), reporting on interventions to prevent or manage IWS in critically ill neonatal, paediatric and adult patients. Database searching included: PubMed, CINAHL, Embase, Cochrane databases, TRIP, CMA Infobase and NICE evidence. Additional grey literature was examined. Study selection and data extraction were performed in duplicate. Data collected included: population, definition of opioid, benzodiazepine or mixed IWS, its assessment and management (drug or strategy, route of administration, dosage and titration), previous drug exposures and outcomes measures. Methodological quality assessment was performed by two independent reviewers using the Cochrane risk of bias tool for RCTs and the ROBINS-I tool for NRSI. A qualitative synthesis of the results is provided. For the subset of studies evaluating multifaceted protocolised care, we meta-analysed results for 4 outcomes and examined the quality of evidence using GRADE post hoc.

RESULTS

Thirteen studies were eligible, including 10 NRSI and 3 RCTs; 11 of these included neonatal and paediatric patients exclusively. Eight studies evaluated multifaceted protocolised interventions, while 5 evaluated individual components of IWS management (e.g. clonidine or methadone at varying dosages, routes of administration and duration of tapering). IWS was measured using an appropriate tool in 6 studies. Ten studies reported upon occurrence of IWS, showing significant reductions (n = 4) or no differences (n = 6). Interventions failed to impact duration of mechanical ventilation, ICU length of stay, and adverse effects. Impact on opioid and/or benzodiazepine total doses and duration showed no differences in 4 studies, while 3 showed opioid and benzodiazepine cumulative doses were significantly reduced by 20-35% and 32-66%, and treatment durations by 1.5-11 and 19 days, respectively. Variable effects on intervention drug exposures were found. Weaning durations were reduced by 6-12 days (n = 4) for opioids and/or methadone and by 13 days (n = 1) for benzodiazepines. In contrast, two studies using interventions centred on transition to enteral routes or longer tapering durations found significant increases in intervention drug exposures. Interventions had overall non-significant effects on additional drug requirements (except for one study). Included studies were at high risk of bias, relating to selection, detection and reporting bias.

CONCLUSION

Interventions for IWS management fail to impact duration of mechanical ventilation or ICU length of stay, while effect on occurrence of IWS and drug exposures is inconsistent. Heterogeneity in the interventions used and methodological issues, including inappropriate and/or subjective identification of IWS and bias due to study design, limited the conclusions.

Prolonged Weaning: S2k Guideline Published by the German Respiratory Society

Mechanical ventilation (MV) is an essential part of modern intensive care medicine. MV is performed in patients with severe respiratory failure caused by respiratory muscle insufficiency and/or lung parenchymal disease; that is, when other treatments such as medication, oxygen administration, secretion management, continuous positive airway pressure (CPAP), or nasal high-flow therapy have failed. MV is required for maintaining gas exchange and allows more time to curatively treat the underlying cause of respiratory failure. In the majority of ventilated patients, liberation or "weaning" from MV is routine, without the occurrence of any major problems. However, approximately 20% of patients require ongoing MV, despite amelioration of the conditions that precipitated the need for it in the first place. Approximately 40-50% of the time spent on MV is required to liberate the patient from the ventilator, a process called "weaning". In addition to acute respiratory failure, numerous factors can influence the duration and success rate of the weaning process; these include age, comorbidities, and conditions and complications acquired during the ICU stay. According to international consensus, "prolonged weaning" is defined as the weaning process in patients who have failed at least 3 weaning attempts, or require more than 7 days of weaning after the first spontaneous breathing trial (SBT). Given that prolonged weaning is a complex process, an interdisciplinary approach is essential for it to be successful. In specialised weaning centres, approximately 50% of patients with initial weaning failure can be liberated from MV after prolonged weaning. However, the heterogeneity of patients undergoing prolonged weaning precludes the direct comparison of individual centres. Patients with persistent weaning failure either die during the weaning process, or are discharged back to their home or to a long-term care facility with ongoing MV. Urged by the growing importance of prolonged weaning, this Sk2 Guideline was first published in 2014 as an initiative of the German Respiratory Society (DGP), in conjunction with other scientific societies involved in prolonged weaning. The emergence of new research, clinical study findings and registry data, as well as the accumulation of experience in daily practice, have made the revision of this guideline necessary. The following topics are dealt with in the present guideline: Definitions, epidemiology, weaning categories, underlying pathophysiology, prevention of prolonged weaning, treatment strategies in prolonged weaning, the weaning unit, discharge from hospital on MV, and recommendations for end-of-life decisions. Special emphasis was placed on the following themes: (1) A new classification of patient sub-groups in prolonged weaning. (2) Important aspects of pulmonary rehabilitation and neurorehabilitation in prolonged weaning. (3) Infrastructure and process organisation in the care of patients in prolonged weaning based on a continuous treatment concept. (4) Changes in therapeutic goals and communication with relatives. Aspects of paediatric weaning are addressed separately within individual chapters. The main aim of the revised guideline was to summarize both current evidence and expert-based knowledge on the topic of "prolonged weaning", and to use this information as a foundation for formulating recommendations related to "prolonged weaning", not only in acute medicine but also in the field of chronic intensive care medicine. The following professionals served as important addressees for this guideline: intensivists, pulmonary medicine specialists, anaesthesiologists, internists, cardiologists, surgeons, neurologists, paediatricians, geriatricians, palliative care clinicians, rehabilitation physicians, intensive/chronic care nurses, physiotherapists, respiratory therapists, speech therapists, medical service of health insurance, and associated ventilator manufacturers.

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.

Therapeutic options for agitation in the intensive care unit

Agitation is common in the intensive care unit (ICU). There are numerous contributing factors, including pain, underlying disease, withdrawal syndrome, delirium and some medication. Agitation can compromise patient safety through accidental removal of tubes and catheters, prolong the duration of stay in the ICU, and may be related to various complications. This review aims to analyse evidence-based medical literature to improve management of agitation and to consider pharmacological strategies. The non-pharmacological approach is considered to reduce the risk of agitation. Pharmacological treatment of agitated patients is detailed and is based on a judicious choice of neuroleptics, benzodiazepines and α2 agonists, and on whether a withdrawal syndrome is identified. Specific management of agitation in elderly patients, brain-injured patients and patients with sleep deprivation are also discussed. This review proposes a practical approach for managing agitation in the ICU.

Opioid and Benzodiazepine Withdrawal Syndromes in Trauma ICU Patients: A Prospective Exploratory Study

Supplemental Digital Content is available in the text.

Trauma ICU patients may require high and/or prolonged doses of opioids and/or benzodiazepines as part of their treatment. These medications may contribute to drug physical dependence, a response manifested by withdrawal syndrome. We aimed to identify risk factors, symptoms, and clinical variables associated with probable withdrawal syndrome.

Optimising the dose of clonidine to achieve sedation in intensive care unit patients with population pharmacokinetics

Aims

The aim of this study was to investigate the population pharmacokinetics (PK) of clonidine in intensive care unit (ICU) patients in order to develop a dosing regimen for sedation.

Methods

We included 24 adult mechanically ventilated, sedated patients from a mixed medical and surgical ICU. Intravenous clonidine was added to standard sedation in doses of 600, 1200 or 1800 μg/d. Within each treatment group, 4 patients received a loading dose of half the daily dose administered in 4 hours. Patients gave an average of 12 samples per individual. In total, 286 samples were available for analysis. Model development was conducted with NONMEM and various covariates were tested. After modelling, doses to achieve a target steady‐state plasma concentration of >1.5 μg/L were explored using stochastic Monte Carlo simulations for 1000 virtual patients.

Results

A 2‐compartment model was the best fit for the concentration‐time data. Clearance (CL) increased linearly with 0.213%/h; using allometric scaling, body weight was a significant covariate on the central volume of distribution (V1). Population PK parameters were: CL 17.1 (L/h), V1 124 (L/70 kg), intercompartmental CL 83.7 (L/h), and peripheral volume of distribution 178 (L), with 33.3% CV interindividual variability on CL and 66.8% CV interindividual variability on V1. Simulations revealed that a maintenance dose of 1200 μg/d provides target sedation concentrations of >1.5 μg/L in 95% of the patients.

Conclusion

A population PK model for clonidine was developed in an adult ICU. A dosing regimen of 1200 μg/d provided a target sedation concentration of >1.5 μg/L.

Opioid and Benzodiazepine Iatrogenic Withdrawal Syndrome in Patients in the Intensive Care Unit

Iatrogenic withdrawal syndrome is an increasingly recognized issue among adult patients in the intensive care unit. The prolonged use of opioids and benzodiazepines during the intensive care unit stay and preexisting disorders associated with their use put patients at risk of developing iatrogenic withdrawal syndrome. Although research to date is scant regarding iatrogenic withdrawal syndrome in adult patients in the intensive care unit, it is important to recognize and adequately manage iatrogenic withdrawal syndrome in order to prevent possible negative outcomes during and after a patient's intensive care unit stay. This article discusses in depth 8 studies of iatrogenic withdrawal syndrome among adult patients in the intensive care unit. It also addresses important aspects of opioid and benzodiazepine iatrogenic withdrawal syndrome, including prevalence, risk factors, and assessment and considers its prevention and management.

Critical Care Pain Management in Patients Affected by the Opioid Epidemic: A Review

The rapid rise in the opioid epidemic has had a deleterious impact across the United States. This increase has drawn the attention of the critical care community not only because of the surge in acute opioid overdose-related admissions, but also due to the increase in the number of opioid-dependent and opioid-tolerant patients being treated in the intensive care unit (ICU). Opioid-related issues relevant to the critical care physician include direct care of patients with opioid overdoses, the provision of sufficient analgesia to patients with opioid dependence and tolerance, and the task of preventing long-term opioid dependence in patients who survive ICU care. This review identifies the challenges facing the ICU physician working with patients presenting with opioid-related complications, discusses current solutions, and suggests future areas of research and heightened ICU clinician attention.

Systematic review of factors associated with energy expenditure in the critically ill

BACKGROUND AND AIMS

Indirect calorimetry is the reference standard for energy expenditure measurement. Predictive formulae that replace it are inaccurate. Our aim was to review the patient and clinical factors associated with energy expenditure in critically ill patients.

METHODS

We conducted a systematic review of the literature. Eligible studies were those reporting an evaluation of factors and energy expenditure. Energy expenditure and factor associations with p-values were extracted from each study, and each factor was classified as either significantly, indeterminantly, or not associated with energy expenditure. Regression coefficients were summarized as measures of central tendency and spread. Metanalysis was performed on correlations.

RESULTS

The search strategy yielded 8521 unique articles, 307 underwent full text review, and 103 articles were included. Most studies were in adults. There were 95 factors with 352 evaluations. Minute volume, weight, age, % body surface area burn, sedation, post burn day, and caloric intake were significantly associated with energy expenditure. Heart rate, fraction of inspired oxygen, respiratory rate, respiratory disease diagnosis, positive end expiratory pressure, intensive care unit days, C- reactive protein, and size were not associated with energy expenditure. Multiple factors (n = 37) were identified with an unclear relationship with energy expenditure and require further evaluation.

CONCLUSIONS

An important interval step in the development of accurate formulae for energy expenditure estimation is a better understanding of relationships between patient and clinical factors and energy expenditure. The review highlights the limitations of currently available data, and identifies important factors that are not included in current prediction formulae of the critically ill.

Psychotropic drug therapy in patients in the intensive care unit - usage, adverse effects, and drug interactions: a review

Managing psychological problems in patients admitted to intensive care unit (ICU) is a big challenge, requiring pharmacological interventions. On the other hand, these patients are more prone to side effects and drug interactions associated with psychotropic drugs use. Benzodiazepines (BZDs), antidepressants, and antipsychotics are commonly used in critically ill patients. Therefore, their therapeutic effects and adverse events are discussed in this study. Different studies have shown that non-BZD drugs are preferred to BZDs for agitation and pain management, but antipsychotic agents are not recommended. Also, it is better not to start antidepressants until the patient has fully recovered. However, further investigations are required for the use of psychotropic drugs in ICUs.

Building on the Shoulders of Giants: Is the use of Early Spontaneous Ventilation in the Setting of Severe Diffuse Acute Respiratory Distress Syndrome Actually Heretical?

Acute respiratory distress syndrome (ARDS) is not a failure of the neurological command of the ventilatory muscles or of the ventilatory muscles; it is an oxygenation defect. As positive pressure ventilation impedes the cardiac function, paralysis under general anaesthesia and controlled mandatory ventilation should be restricted to the interval needed to control the acute cardio-ventilatory distress observed upon admission into the critical care unit (CCU; "salvage therapy" during "shock state"). Current management of early severe diffuse ARDS rests on a prolonged interval of controlled mechanical ventilation with low driving pressure, paralysis (48 h, too often overextended), early proning and positive end-expiratory pressure (PEEP). Therefore, the time interval between arrival to the CCU and switching to spontaneous ventilation (SV) is not focused on normalizing the different factors involved in the pathophysiology of ARDS: fever, low cardiac output, systemic acidosis, peripheral shutdown (local acidosis), supine position, hypocapnia (generated by hyperpnea and tachypnea), sympathetic activation, inflammation and agitation. Then, the extended period of controlled mechanical ventilation with paralysis under general anaesthesia leads to CCU-acquired pathology, including low cardiac output, myoneuropathy, emergence delirium and nosocomial infection. The stabilization of the acute cardio-ventilatory distress should primarily itemize the pathophysiological conditions: fever control, improved micro-circulation and normalized local acidosis, 'upright' position, minimized hypercapnia, sympathetic de-activation (normalized sympathetic activity toward baseline levels resulting in improved micro-circulation with alpha-2 agonists administered immediately following optimized circulation and endotracheal intubation), lowered inflammation and 'cooperative' sedation without respiratory depression evoked by alpha-2 agonists. Normalised metabolic, circulatory and ventilatory demands will allow one to single out the oxygenation defect managed with high PEEP (diffuse recruitable ARDS) under early spontaneous ventilation (airway pressure release ventilation+SV or low-pressure support). Assuming an improved overall status, PaO₂/FiO₂≥150-200 allows for extubation and continuous non-invasive ventilation. Such fast-tracking may avoid most of the CCU-acquired pathologies. Evidence-based demonstration is required.

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

During severe septic shock and/or severe acute respiratory distress syndrome (ARDS) patients present with a limited cardio-ventilatory reserve (low cardiac output and blood pressure, low mixed venous saturation, increased lactate, low PaO2/FiO2 ratio, etc.), especially when elderly patients or co-morbidities are considered. Rescue therapies (low dose steroids, adding vasopressin to noradrenaline, proning, almitrine, NO, extracorporeal membrane oxygenation, etc.) are complex. Fever, above 38.5-39.5°C, increases both the ventilatory (high respiratory drive: large tidal volume, high respiratory rate) and the metabolic (increased O2 consumption) demands, further limiting the cardio-ventilatory reserve. Some data (case reports, uncontrolled trial, small randomized prospective trials) suggest that control of elevated body temperature ("fever control") leading to normothermia (35.5-37°C) will lower both the ventilatory and metabolic demands: fever control should simplify critical care management when limited cardio-ventilatory reserve is at stake. Usually fever control is generated by a combination of general anesthesia ("analgo-sedation", light total intravenous anesthesia), antipyretics and cooling. However general anesthesia suppresses spontaneous ventilation, making the management more complex. At variance, alpha-2 agonists (clonidine, dexmedetomidine) administered immediately following tracheal intubation and controlled mandatory ventilation, with prior optimization of volemia and atrio-ventricular conduction, will reduce metabolic demand and facilitate normothermia. Furthermore, after a rigorous control of systemic acidosis, alpha-2 agonists will allow for accelerated emergence without delirium, early spontaneous ventilation, improved cardiac output and micro-circulation, lowered vasopressor requirements and inflammation. Rigorous prospective randomized trials are needed in subsets of patients with a high fever and spiraling toward refractory septic shock and/or presenting with severe ARDS.

Alpha-2 agonists for sedation of mechanically ventilated adults in intensive care units: a systematic review

BACKGROUND

Care of critically ill patients in intensive care units (ICUs) often requires potentially invasive or uncomfortable procedures, such as mechanical ventilation (MV). Sedation can alleviate pain and discomfort, provide protection from stressful or harmful events, prevent anxiety and promote sleep. Various sedative agents are available for use in ICUs. In the UK, the most commonly used sedatives are propofol (Diprivan(®), AstraZeneca), benzodiazepines [e.g. midazolam (Hypnovel(®), Roche) and lorazepam (Ativan(®), Pfizer)] and alpha-2 adrenergic receptor agonists [e.g. dexmedetomidine (Dexdor(®), Orion Corporation) and clonidine (Catapres(®), Boehringer Ingelheim)]. Sedative agents vary in onset/duration of effects and in their side effects. The pattern of sedation of alpha-2 agonists is quite different from that of other sedatives in that patients can be aroused readily and their cognitive performance on psychometric tests is usually preserved. Moreover, respiratory depression is less frequent after alpha-2 agonists than after other sedative agents.

OBJECTIVES

To conduct a systematic review to evaluate the comparative effects of alpha-2 agonists (dexmedetomidine and clonidine) and propofol or benzodiazepines (midazolam and lorazepam) in mechanically ventilated adults admitted to ICUs.

DATA SOURCES

We searched major electronic databases (e.g. MEDLINE without revisions, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE and Cochrane Central Register of Controlled Trials) from 1999 to 2014.

METHODS

Evidence was considered from randomised controlled trials (RCTs) comparing dexmedetomidine with clonidine or dexmedetomidine or clonidine with propofol or benzodiazepines such as midazolam, lorazepam and diazepam (Diazemuls(®), Actavis UK Limited). Primary outcomes included mortality, duration of MV, length of ICU stay and adverse events. One reviewer extracted data and assessed the risk of bias of included trials. A second reviewer cross-checked all the data extracted. Random-effects meta-analyses were used for data synthesis.

RESULTS

Eighteen RCTs (2489 adult patients) were included. One trial at unclear risk of bias compared dexmedetomidine with clonidine and found that target sedation was achieved in a higher number of patients treated with dexmedetomidine with lesser need for additional sedation. The remaining 17 trials compared dexmedetomidine with propofol or benzodiazepines (midazolam or lorazepam). Trials varied considerably with regard to clinical population, type of comparators, dose of sedative agents, outcome measures and length of follow-up. Overall, risk of bias was generally high or unclear. In particular, few trials blinded outcome assessors. Compared with propofol or benzodiazepines (midazolam or lorazepam), dexmedetomidine had no significant effects on mortality [risk ratio (RR) 1.03, 95% confidence interval (CI) 0.85 to 1.24, I (2) = 0%; p = 0.78]. Length of ICU stay (mean difference -1.26 days, 95% CI -1.96 to -0.55 days, I (2) = 31%; p = 0.0004) and time to extubation (mean difference -1.85 days, 95% CI -2.61 to -1.09 days, I (2) = 0%; p < 0.00001) were significantly shorter among patients who received dexmedetomidine. No difference in time to target sedation range was observed between sedative interventions (I (2) = 0%; p = 0.14). Dexmedetomidine was associated with a higher risk of bradycardia (RR 1.88, 95% CI 1.28 to 2.77, I (2) = 46%; p = 0.001).

LIMITATIONS

Trials varied considerably with regard to participants, type of comparators, dose of sedative agents, outcome measures and length of follow-up. Overall, risk of bias was generally high or unclear. In particular, few trials blinded assessors.

CONCLUSIONS

Evidence on the use of clonidine in ICUs is very limited. Dexmedetomidine may be effective in reducing ICU length of stay and time to extubation in critically ill ICU patients. Risk of bradycardia but not of overall mortality is higher among patients treated with dexmedetomidine. Well-designed RCTs are needed to assess the use of clonidine in ICUs and identify subgroups of patients that are more likely to benefit from the use of dexmedetomidine.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42014014101.

FUNDING

The National Institute for Health Research Health Technology Assessment programme. The Health Services Research Unit is core funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates.

Influence of clonidine induced sympathicolysis on anaemia tolerance in anaesthetized pigs

Background

Clonidine effectively decreases perioperative mortality by reducing sympathetic tone. However, application of clonidine might also restrict anaemia tolerance due to impairment of compensatory mechanisms. Therefore, the influence of clonidine induced, short-term sympathicolysis on anaemia tolerance was assessed in anaesthetized pigs. We measured the effect of clonidine on anaemia tolerance and of the potential for macrohemodynamic alterations to constrain the acute anaemia compensatory mechanisms.

Methods

After governmental approval, 14 anaesthetized pigs of either gender (Deutsche Landrasse, weight (mean ± SD) 24.1 ± 2.4 kg) were randomly assigned to intravenous saline or clonidine treatment (bolus: 20 μg · kg⁻¹, continuous infusion: 15 μg · kg⁻¹ · h⁻¹). Thereafter, the animals were hemodiluted by exchange of whole blood for 6 % hydroxyethyl starch (MW 130.000/0.4) until the individual critical haemoglobin concentration (Hb_crit) was reached. Primary outcome parameters were Hb_crit and the exchangeable blood volume (EBV) until Hb_crit was reached.

Results

Hb_crit did not differ between both groups (values are median [interquartile range]: saline: 2.2 (2.0–2.5) g · dL⁻¹ vs. clonidine: 2.1 (2.1–2.4) g · dL⁻¹; n.s.). Furthermore, there was no difference in exchangeable blood volume (EBV) between both groups (saline: 88 (76–106) mL · kg⁻¹ vs. clonidine: 92 (85–95) mL · kg⁻¹; n.s.).

Conclusion

Anaemia tolerance was not affected by clonidine induced sympathicolysis. Consequently, perioperative clonidine administration probably has not to be omitted in view of acute anaemia.

Evaluating the transition from dexmedetomidine to clonidine for agitation management in the intensive care unit

OBJECTIVES

Limited literature exists examining the use of enteral clonidine to transition patients from dexmedetomidine for management of agitation. The aim of this study was to evaluate dexmedetomidine discontinuation within 8 h of enteral clonidine administration in addition to the rates of dexmedetomidine re-initiation in patients who failed clonidine transition.

METHODS

A single-center, retrospective analysis evaluated critically ill adult patients from 1 February 2013 to 28 February 2014, who used dexmedetomidine and clonidine for sedation management. Patients were excluded if they received enteral clonidine for reasons other than sedation management. Secondary aims of the study observed time to dexmedetomidine discontinuation, agitation (Richmond Agitation Sedation Scale) and delirium ratings (Confusion Assessment Method for the intensive care unit), clonidine dose, and enteral clonidine discontinuation.

RESULTS

In all, 26 patients were evaluated. Demographics included a mean age of 54.4 (±16.7) years, Acute Physiology and Chronic Health Evaluation II score of 18 (interquartile range = 14-22), and 80.7% of admissions to the cardiac surgery intensive care unit. Dexmedetomidine discontinuation occurred in 17 (65.4%) patients within 8 h of receiving clonidine. The total median clonidine exposure per intensive care unit day was 0.35 mg/ICU day (interquartile range = 0.2-0.5) in patients who discontinued dexmedetomidine within 8 h and 0.5 mg/ICU day (interquartile range = 0.4-1.0) (p = 0.036) in patients who did not. We observed similar Richmond Agitation Sedation Scale and Confusion Assessment Method for the intensive care unit scores and rates of hypotension. Unintentional use of clonidine beyond ICU and hospital stay was observed in 54% and 23% of patients, respectively.

CONCLUSION

Enteral clonidine may be an effective and safe alternative to transition patients off of dexmedetomidine for ongoing sedation management. Clinicians should critically evaluate the need for clonidine at ICU and hospital discharge. More studies comparing the use of clonidine to transition from dexmedetomidine infusions are needed.

A centrally acting antihypertensive, clonidine, combined to a venous dilator, nitroglycerin, to handle severe pulmonary edema

A patient, with known left ventricular failure presented with severe pulmonary edema, an ejection fraction of 10% to 15%, knee mottling, and lactates of 7 mM L⁻¹. He was treated with unusually high-dose nitroglycerin (NTG) intravenously (IV; NTG ≈ 70 mg for 1 hour). To suppress dyspnea, systolic blood pressure had to be lowered from ≈ 150-160 to ≈ 100-120 mm Hg. To lower NTG requirement, an α-2 agonist, clonidine, was administered (300 μg IV for 2 hours). Dyspnea, tachypnea, and tachycardia subsided for 1 to 2 hours, allowing to reduce NTG infusion to 2 to 4 mg h⁻¹. State-of the-art treatment was superimposed: sitting position with leg down, noninvasive ventilation, positive end-expiratory pressure, bolus of furosemide 250 mg, and administration of 1000 mL of crystalloid for 1 hour under echocardiographic guidance. We ascribed the resistance to NTG to the activation of the sympathetic, vasopressin, and renin-angiotensin systems ("neurohormonal activation"). α-2 agonists reduce the sympathetic activation observed during severe left ventricular failure and overall oxygen consumption, evoke systemic and pulmonary arterial dilation, increase diastolic time, and improve diastolic function and diuresis. Because the α-2 agonist, dexmedetomidine, is available as an IV drug on the North American market, a niche may exist in the setting of emergency medicine/coronary care. This awaits evidence-based documentation.

Clonidine withdrawal induced sympathetic surge

A 30-year-old man with a history of epilepsy and substance misuse presented to the hospital with status epilepticus. Difficult seizure control necessitated anaesthetising the patient followed by intubation and ventilation. A clonidine infusion was started as the patient developed withdrawal syndrome and was difficult to wean off mechanical ventilation. Once the withdrawal syndrome was controlled, the clonidine was abruptly stopped. Two hours after stopping the infusion, the patient developed high-grade fever, severe hypertension, tachycardia, profound sweating and lacrimation. The patient then developed respiratory distress syndrome secondary to acute pulmonary oedema. Clonidine withdrawal as a cause of such response was proposed. Reversal of symptoms and successful reweaning was achieved by restarting a low-dose clonidine infusion followed by slow downward titration and use of oral clonidine as a step-down measure. The patient was subsequently discharged from the intensive care unit.

Is there a place for pressure-support ventilation and high positive end-expiratory pressure combined to alpha-2 agonists early in severe diffuse acute respiratory distress syndrome?

Acute respiratory distress syndrome (ARDS) is associated with a high mortality linked primarily to co-morbidities (sepsis, cardiac failure, multiple organ failure, etc.). When the lung is the single failing organ, quick resolution of ARDS should skip some complications arising from a prolonged stay in the critical care unit. In severe ARDS (PaO2/FIO2=P/F<100 with positive end-expiratory pressure (PEEP) ≥ 5 cm H2O), current recommendations are to intubate the trachea of the patient and use mechanical ventilation, low tidal volume, high PEEP, prone positioning and possibly neuromuscular blockade in association with intravenous sedation. Another strategy is possible. Firstly, spontaneous ventilation (SV) coupled with pressure support (PS) ventilation and high PEEP is possible from tracheal intubation onwards, with the possible exception of the short period following immediately tracheal intubation. Secondly, using alpha-2 adrenergic agonists (e.g. clonidine, dexmedetomidine) can provide first-line sedation from the beginning of mechanical ventilation, as they preserve respiratory drive, lower oxygen consumption and pulmonary hypertension and increase diuresis. Alpha-2 agonists are to be supplemented, if appropriate, by drugs devoid of effect on respiratory drive (neuroleptics, etc.). The expected benefits would be to prevent acquired diaphragmatic weakness, accumulation of sedation, cognitive dysfunction, and presumably improved outcome. This hypothesis should be tested in a double blind randomized controlled trial.

Sedation in the intensive care setting

Critically ill patients are routinely provided analgesia and sedation to prevent pain and anxiety, permit invasive procedures, reduce stress and oxygen consumption, and improve synchrony with mechanical ventilation. Regional preferences, patient history, institutional bias, and individual patient and practitioner variability, however, create a wide discrepancy in the approach to sedation of critically ill patients. Untreated pain and agitation increase the sympathetic stress response, potentially leading to negative acute and long-term consequences. Oversedation, however, occurs commonly and is associated with worse clinical outcomes, including longer time on mechanical ventilation, prolonged stay in the intensive care unit, and increased brain dysfunction (delirium and coma). Modifying sedation delivery by incorporating analgesia and sedation protocols, targeted arousal goals, daily interruption of sedation, linked spontaneous awakening and breathing trials, and early mobilization of patients have all been associated with improvements in patient outcomes and should be incorporated into the clinical management of critically ill patients. To improve outcomes, including time on mechanical ventilation and development of acute brain dysfunction, conventional sedation paradigms should be altered by providing necessary analgesia, incorporating propofol or dexmedetomidine to reach arousal targets, and reducing benzodiazepine exposure.

[Dexmedetomidine and clonidine: a review of their pharmacodynamy to define their role for sedation in intensive care patients]

Alpha-2 adrenergic agonists ("alpha-2 agonists") present multiple pharmacodynamic effects: rousable sedation, decreased incidence of delirium in the setting of critical care, preservation of respiratory drive, decreased whole body oxygen consumption, decreased systemic and pulmonary arterial impedance, improved left ventricular systolic and diastolic function, preserved vascular reactivity to exogenous catecholamines, preserved vasomotor baroreflex with lowered set point, preserved kidney function, decreased protein catabolism. These pharmacodynamic effects explain the interest for these drugs in the critical care setting. However, their exact role for sedation in critically ill-patients remains open for further studies. Given the few double-blind randomized multicentric trials available, the present non exhaustive analysis of the literature aims at presenting the utilization of alpha-2 agonists as potential first-line sedative agents, in the critical care setting. Suggestions regarding the use of alpha-2 agonists as sedatives are detailed.

Dexmedetomidine and clonidine induce long-lasting activation of the respiratory rhythm generator of neonatal mice: possible implication for critical care

Dexmedetomidine and clonidine are alpha-2 adrenoceptor agonists increasingly used in the critical care unit as sedative agents for their benzodiazepine-sparing effects and their limited depressing effect on breathing. However adverse effects on breathing have been also reported with alpha-2 adrenoceptor agonists and their central effects on the respiratory rhythm generator are poorly known. We therefore examined the effects of dexmedetomidine, clonidine, the alpha-2 adrenoceptor antagonist yohimbine and the benzodiazepine midazolam on the activity of the isolated respiratory rhythm generator of neonatal mice using medullary preparations where the respiratory rhythm generator continued to function in vitro. For the first time, we showed that 5min bath applications of dexmedetomidine or clonidine activated the respiratory rhythm generator for periods over than 30min. Second, we showed that the long-lasting effect of dexmedetomidine implicated receptors other than alpha-2 adrenoceptors as it persisted after their blockade with yohimbine. Third, we reported that 5min bath applications of the benzodiazepine midazolam significantly depressed the respiratory rhythm generator, and that this depression was prevented by pre-treatment with either dexmedetomidine or clonidine. Although further experiments are still required to identify the mechanisms through which dexmedetomidine and clonidine activate the respiratory rhythm generator, our current in vitro results in neonatal mice support the use of dexmedetomidine and clonidine in the critical care unit.

Beneficial effects of loxapine on agitation and breathing patterns during weaning from mechanical ventilation

INTRODUCTION

Interruption of sedation during weaning from mechanical ventilation often leads to patient agitation because of withdrawal syndrome. We tested the short-term efficacy and tolerance of loxapine in this situation.

METHODS

Nineteen mechanically ventilated patients with marked agitation after sedation withdrawal were included. Three agitation scales, the Richmond Agitation Sedation Scale (RASS), the Motor Activity Assessment Scale (MAAS), and the Ramsay and physiological variables (respiratory rate, airway occlusion pressure during the first 0.1 second of inspiration (P0.1), heart rate and systolic arterial blood pressure) were recorded before and after loxapine administration.

RESULTS

Loxapine dramatically improved all agitation scores (RASS and MASS decreased from 2 +/- 0 to -1.1 +/- 2.3, and 5.4 +/- 0.5 to 2.7 +/- 1.6, respectively; Ramsay increased from 1.0 +/- 0 to 3.5 +/- 1.5, 60 minutes after loxapine administration, P < 0.05 for all scores) as well as P0.1 (6 +/- 4.2 to 1.8 +/- 1.8 cm H2O; P < 0.05) and respiratory rate (from 31.2 +/- 7.2 to 23.4 +/- 7.8; P < 0.05) without hemodynamic adverse events. No side effects occurred. Sixteen (84%) patients were successfully managed with loxapine, sedation was resumed in two others, and one patient self-extubated without having to be reintubated.

CONCLUSIONS

Loxapine was safe and effective in treating agitation in a small group of mechanically ventilated patients and improved respiratory physiologic parameters, enabling the weaning process to be pursued. A multicenter trial is under way to confirm these promising results.

Intensive Care Unit-acquired infection as a side effect of sedation

Introduction

Sedative and analgesic medications are routinely used in mechanically ventilated patients. The aim of this review is to discus epidemiologic data that suggest a relationship between infection and sedation, to review available data for the potential causes and pathophysiology of this relationship, and to identify potential preventive measures.

Methods

Data for this review were identified through searches of PubMed, and from bibliographies of relevant articles.

Results

Several epidemiologic studies suggested a link between sedation and ICU-acquired infection. Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Furthermore, experimental evidence coming from studies both in humans and animals suggest that sedatives and analgesics present immunomodulatory properties that might alter the immunologic response to exogenous stimuli. Clinical studies comparing different sedative agents do not provide evidence to recommend the use of a particular agent to reduce ICU-acquired infection rate. However, sedation strategies aiming to reduce the duration of mechanical ventilation, such as daily interruption of sedatives or nursing-implementing sedation protocol, should be promoted. In addition, the use of short acting opioids, propofol, and dexmedetomidine is associated with shorter duration of mechanical ventilation and ICU stay, and might be helpful in reducing ICU-acquired infection rates.

Conclusions

Prolongation of exposure to risk factors for infection, microaspiration, gastrointestinal motility disturbances, microcirculatory effects, and immunomodulatory effects are main mechanisms by which sedation may favour infection in critically ill patients. Future studies should compare the effect of different sedative agents, and the impact of progressive opioid discontinuation compared with abrupt discontinuation on ICU-acquired infection rates.