A technical review of the history, development and performance of the anaesthetic conserving device "AnaConDa" for delivering volatile anaesthetic in intensive and post-operative critical care

A systematic review on the use of sevoflurane in the management of status asthmaticus in adults

BACKGROUND

To conduct a systematic review looking into the use of sevoflurane in the management of status asthmaticus (SA) in adults.

METHODS

We performed a systematic search on PubMed, EMBASE, and The Cochrane Library - CENTRAL through 23rd August 2023, restricting to studies reported in English. We included studies reporting use of sevoflurane in asthmatics beyond its use as an anaesthetic agent in surgeries i.e. in the emergency department (ED) and critical care setting, and focused on patient's clinical parameters, ventilation pressures and weaning of invasive ventilation.

RESULTS

A total of 13 publications fulfilled the inclusion criteria, comprising of 18 cases. All publications were of case reports/ series and conference abstracts, and no randomised trials were available. Most patients required intubation despite best medical management before sevoflurane administration, and high airway pressures and respiratory acidosis were apparent. There was significant heterogeneity regarding severity of asthma, treatment instituted, and the delivery, duration and concentration of sevoflurane administered. Many of the studies also did not quantify the changes in parameters pre- and post-sevoflurane. Sixteen patients experienced improvements in clinical status with sevoflurane administration-one required escalation to extracorporeal membrane oxygenation (ECMO), and another did not survive.

CONCLUSION

The systematic review suggests sevoflurane can be a valuable treatment option in SA. As these cases are rare and heterogenous, further prospective case series are needed to support this.

Prospective Observational Study of Volatile Sedation with Sevoflurane After Aneurysmal Subarachnoid Hemorrhage Using the Sedaconda Anesthetic Conserving Device

BACKGROUND

Volatile sedation is still used with caution in patients with acute brain injury because of safety concerns. We analyzed the effects of sevoflurane sedation on systemic and cerebral parameters measured by multimodal neuromonitoring in patients after aneurysmal subarachnoid hemorrhage (aSAH) with normal baseline intracranial pressure (ICP).

METHODS

In this prospective observational study, we analyzed a 12-h period before and after the switch from intravenous to volatile sedation with sevoflurane using the Sedaconda Anesthetic Conserving Device with a target Richmond Agitation Sedation Scale score of - 5 to - 4. ICP, cerebral perfusion pressure (CPP), brain tissue oxygenation (PBrO2), metabolic values of cerebral microdialysis, systemic cardiopulmonary parameters, and the administered drugs before and after the sedation switch were analyzed.

RESULTS

We included 19 patients with a median age of 61 years (range 46-78 years), 74% of whom presented with World Federation of Neurosurgical Societies grade 4 or 5 aSAH. We observed no significant changes in the mean ICP (9.3 ± 4.2 vs. 9.7 ± 4.2 mm Hg), PBrO2 (31.0 ± 13.2 vs. 32.2 ± 12.4 mm Hg), cerebral lactate (5.0 ± 2.2 vs. 5.0 ± 1.9 mmol/L), pyruvate (136.6 ± 55.9 vs. 134.1 ± 53.6 µmol/L), and lactate/pyruvate ratio (37.4 ± 8.7 vs. 39.8 ± 9.2) after the sedation switch to sevoflurane. We found a significant decrease in mean arterial pressure (MAP) (88.6 ± 7.6 vs. 86.3 ± 5.8 mm Hg) and CPP (78.8 ± 8.5 vs. 76.6 ± 6.6 mm Hg) after the initiation of sevoflurane, but the decrease was still within the physiological range requiring no additional hemodynamic support.

CONCLUSIONS

Sevoflurane appears to be a feasible alternative to intravenous sedation in patients with aSAH without intracranial hypertension, as our study did not show negative effects on ICP, cerebral oxygenation, or brain metabolism. Nevertheless, the risk of a decrease of MAP leading to a consecutive CPP decrease should be considered.

Volatile anesthetics for lung- and diaphragm-protective sedation

This review explores the complex interactions between sedation and invasive ventilation and examines the potential of volatile anesthetics for lung- and diaphragm-protective sedation. In the early stages of invasive ventilation, many critically ill patients experience insufficient respiratory drive and effort, leading to compromised diaphragm function. Compared with common intravenous agents, inhaled sedation with volatile anesthetics better preserves respiratory drive, potentially helping to maintain diaphragm function during prolonged periods of invasive ventilation. In turn, higher concentrations of volatile anesthetics reduce the size of spontaneously generated tidal volumes, potentially reducing lung stress and strain and with that the risk of self-inflicted lung injury. Taken together, inhaled sedation may allow titration of respiratory drive to maintain inspiratory efforts within lung- and diaphragm-protective ranges. Particularly in patients who are expected to require prolonged invasive ventilation, in whom the restoration of adequate but safe inspiratory effort is crucial for successful weaning, inhaled sedation represents an attractive option for lung- and diaphragm-protective sedation. A technical limitation is ventilatory dead space introduced by volatile anesthetic reflectors, although this impact is minimal and comparable to ventilation with heat and moisture exchangers. Further studies are imperative for a comprehensive understanding of the specific effects of inhaled sedation on respiratory drive and effort and, ultimately, how this translates into patient-centered outcomes in critically ill patients.

Volatile Sedation in Neurointensive Care Patients After Aneurysmal Subarachnoid Hemorrhage: Effects on Delayed Cerebral Ischemia, Cerebral Vasospasm, and Functional Outcome

BACKGROUND

Volatile anesthetics have shown neuroprotective effects in preclinical studies, but clinical data on their use after aneurysmal subarachnoid hemorrhage (aSAH) are limited. This study aimed to analyze whether the use of volatile anesthetics for neurocritical care sedation affects the incidence of delayed cerebral ischemia (DCI), cerebral vasospasm (CVS), DCI-related infarction, or functional outcome.

METHODS

Data were retrospectively collected for ventilated aSAH patients (2016-2022), who received sedation for at least 180 hours. For comparative analysis, patients were assigned to a control and a study group according to the sedation used (intravenous vs. volatile sedation). Logistic regression analysis was performed to identify independent predictors of DCI, CVS, DCI-related infarction, and functional outcome.

RESULTS

Ninety-nine patients with a median age of 58 years (interquartile range: 52-65 years) were included. Forty-seven patients (47%) received intravenous sedation, while 52 patients (53%) received (additional) volatile sedation with isoflurane (n = 30, 58%) or sevoflurane (n = 22, 42%) for a median duration of 169 hours (range: 5-298 hours). There were no significant differences between the 2 groups regarding the occurrence of DCI, angiographic CVS, DCI-related infarction, or functional outcome. In a multivariable logistic regression analysis, the use of volatile anesthetics had no impact on the incidence of DCI-related infarction or the patients' functional outcome.

CONCLUSIONS

Volatile sedation in aSAH patients is not associated with the incidence of DCI, CVS, DCI-related infarction, or functional outcome. Although we could not demonstrate neuroprotective effects of volatile anesthetics, our results suggest that volatile sedation after aSAH has no negative effect on the patient's outcome.

Practical approach to inhaled sedation in the critically ill patient. Sedation, analgesia and Delirium Working Group (GTSAD) of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC)

The use of sedatives in Intensive Care Units (ICU) is essential for relieving anxiety and stress in mechanically ventilated patients, and it is related to clinical outcomes, duration of mechanical ventilation, and length of stay in the ICU. Inhaled sedatives offer benefits such as faster awakening and extubation, decreased total opioid and neuromuscular blocking agents (NMB) doses, as well as bronchodilator, anticonvulsant, and cardiopulmonary and neurological protective effects. Inhaled sedation is administered using a specific vaporizer. Isoflurane is the recommended agent due to its efficacy and safety profile. Inhaled sedation is recommended for moderate and deep sedation, prolonged sedation, difficult sedation, patients with acute respiratory distress syndrome (ARDS), status asthmaticus, and super-refractory status epilepticus. By offering these significant advantages, the use of inhaled sedatives allows for a personalized and controlled approach to optimize sedation in the ICU.

Isoflurane, like sepsis, decreases CYP1A2 liver enzyme activity in intensive care patients: a clinical study and network model

PURPOSE

Liver function of intensive care patients is routinely monitored by static blood pathology. For specific indications, liver specific cytochrome activity may be measured by the commercially available maximum liver function capacity (LiMAx) test via quantification of the cytochrome P450 1A2 (CYP1A2) dependent C-methacetin metabolism. Sedation with the volatile anesthetic isoflurane was suspected to abrogate the correlation of LiMAx test with global liver function. We hypothesized that isoflurane has a CYP1A2-activity and LiMAx test result decreasing effect.

METHODS

In this monocentric, observational clinical study previously liver healthy intensive care patients, scheduled to be changed from propofol to isoflurane sedation, were enrolled. LiMAx testing was done before, during and after termination of isoflurane sedation.

RESULTS

The mean LiMAx value decreased during isoflurane sedation. Septic patients (n = 11) exhibited lower LiMAx values compared to non-septic patients (n = 11) at all time points. LiMAx values decreased with isoflurane from 140 ± 82 to 30 ± 34 µg kg-1 h-1 in the septic group and from 253 ± 92 to 147 ± 131 µg kg-1 h-1 in the non-septic group while laboratory markers did not imply significant hepatic impairment. Lactate increased during isoflurane inhalation without clinical consequence.

CONCLUSION

Sepsis and isoflurane have independently demonstrated an effect on reducing the hepatic CYP1A2-activity. A network model was constructed that could explain the mechanism through the influence of isoflurane on hypoxia inducible factor (HIF-1α) by upregulation of the hypoxia-inducible pathway and the downregulation of CYP1A2-activity via the ligand-inducible pathway. Thus, the increased anaerobic metabolism may result in lactate accumulation. The influence of isoflurane sedation on the validated correlation of global liver function with CYP1A2-activity measured by LiMAx testing needs to be investigated in more detail.

Guidelines for inhaled sedation in the ICU

INTRODUCTION AND OBJECTIVES

Sedation is used in intensive care units (ICU) to improve comfort and tolerance during mechanical ventilation, invasive interventions, and nursing care. In recent years, the use of inhalation anaesthetics for this purpose has increased. Our objective was to obtain and summarise the best evidence on inhaled sedation in adult patients in the ICU, and use this to help physicians choose the most appropriate approach in terms of the impact of sedation on clinical outcomes and the risk-benefit of the chosen strategy.

METHODOLOGY

Given the overall lack of literature and scientific evidence on various aspects of inhaled sedation in the ICU, we decided to use a Delphi method to achieve consensus among a group of 17 expert panellists. The processes was conducted over a 12-month period between 2022 and 2023, and followed the recommendations of the CREDES guidelines.

RESULTS

The results of the Delphi survey form the basis of these 39 recommendations - 23 with a strong consensus and 15 with a weak consensus.

CONCLUSION

The use of inhaled sedation in the ICU is a reliable and appropriate option in a wide variety of clinical scenarios. However, there are numerous aspects of the technique that require further study.

Effects on mechanical power of different devices used for inhaled sedation in a bench model of protective ventilation in ICU

BACKGROUND

Inhaled sedation during invasive mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) has received increasing attention. However, inhaled sedation devices increase dead-space ventilation and an undesirable effect is the increase in minute ventilation needed to maintain CO2 removal. A consequence of raising minute ventilation is an increase in mechanical power (MP) that can promote lung injury. However, the effect of inhaled sedation devices on MP remains unknown.

METHODS

We conducted a bench study to assess and compare the effects of three devices delivering inhaled sevoflurane currently available in ICU (AnaConDa-50 mL (ANA-50), AnaConDa-100 mL (ANA-100), and MIRUS) on MP by using a test lung model set with three compliances (20, 40, and 60 mL/cmH2O). We simulated lung-protective ventilation using a low tidal volume and two levels of positive end-expiratory pressure (5 and 15 cmH2O) under ambient temperature and dry conditions. Following the insertion of the devices, either the respiratory rate or tidal volume was increased in 15%-steps until end-tidal CO2 (EtCO2) returned to the baseline value. MP was calculated at baseline and after EtCO2 correction using a simplified equation.

RESULTS

Following device insertion, the EtCO2 increase was significantly greater with MIRUS (+ 78 ± 13%) and ANA-100 (+ 100 ± 11%) than with ANA-50 (+ 49 ± 7%). After normalizing EtCO2 by adjusting minute ventilation, MP significantly increased by more than 50% with all inhaled sedation devices compared to controls. The lowest increase in MP was observed with ANA-50 (p < 0.05 versus ANA-100 and MIRUS). The Costa index, another parameter assessing the mechanical energy delivered to the lungs, calculated as driving pressure × 4 + respiratory rate, significantly increased by more than 20% in all experimental conditions. Additional experiments performed under body temperature, ambient pressure, and gas saturated with water vapor conditions, confirmed the main results with an increase in MP > 50% with all devices after normalizing EtCO2 by adjusting minute ventilation.

CONCLUSION

Inhaled sedation devices substantially increased MP in this bench model of protective ventilation, which might limit their benefits in ARDS.

The advantages of inhalational sedation using an anesthetic-conserving device versus intravenous sedatives in an intensive care unit setting: A systematic review

BACKGROUND

Sedation is fundamental to the management of patients in the intensive care unit (ICU). Its indications in the ICU are vast, including the facilitating of mechanical ventilation, permitting invasive procedures, and managing anxiety and agitation. Inhaled sedation with halogenated agents, such as isoflurane or sevoflurane, is now feasible in ICU patients using dedicated devices/systems. Its use may reduce adverse events and improve ICU outcomes compared to conventional intravenous (IV) sedation in the ICU. This review examined the effectiveness of inhalational sedation using the anesthetic conserving device (ACD) compared to standard IV sedation for adult patients in ICU and highlights the technical aspects of its functioning.

METHODS

We searched the PubMed, Cochrane Central Register of Controlled Trials, The Cochrane Library, MEDLINE, Web of Science, and Sage Journals databases using the terms "anesthetic conserving device," "Anaconda," "sedation" and "intensive care unit" in randomized clinical studies that were performed between 2012 and 2022 and compared volatile sedation using an ACD with IV sedation in terms of time to extubation, duration of mechanical ventilation, and lengths of ICU and hospital stay.

RESULTS

Nine trials were included. Volatile sedation (sevoflurane or isoflurane) administered through an ACD shortened the awakening time compared to IV sedation (midazolam or propofol).

CONCLUSION

Compared to IV sedation, volatile sedation administered through an ACD in the ICU shortened the awakening and extubation times, ICU length of stay, and duration of mechanical ventilation. More clinical trials that assess additional clinical outcomes on a large scale are needed.

Sevoflurane sedation in COVID-19 acute respiratory distress syndrome: an observational study with a propensity score matching model

Introduction

The management of severe COVID-19-induced acute respiratory distress syndrome (C-ARDS) often involves deep sedation. This study evaluated the efficacy of sevoflurane, a volatile anesthetic, as an alternative to traditional intravenous sedation in this patient population.

Methods

This single-center, retrospective cohort study enrolled 112 patients with C-ARDS requiring invasive mechanical ventilation. A propensity score matching model was utilized to pair 56 patients receiving sevoflurane sedation with 56 patients receiving intravenous sedation. The primary outcome was mortality, with secondary outcomes being changes in oxygenation (PaO2/FiO2 ratio), pulmonary compliance, and levels of D-Dimer, CRP, and creatinine.

Results

The use of sevoflurane was associated with a statistically significant reduction in mortality (OR 0.40, 95% CI 0.18-0.87, beta = -0.9, p = 0.02). In terms of secondary outcomes, an increase in the PaO2/FiO2 ratio and pulmonary static compliance was observed, although the results were not statistically significant. No significant differences were noted in the levels of D-Dimer, CRP, and creatinine between the two groups.

Conclusion

Our findings suggest an association between the use of sevoflurane and improved outcomes in C-ARDS patients requiring invasive mechanical ventilation. However, due to the single-center, retrospective design of the study, caution should be taken in interpreting these results, and further research is needed to corroborate these findings. The study offers promising insights into potential alternative sedation strategies in the management of severe C-ARDS.

Ventilatory Effects of Isoflurane Sedation via the Sedaconda ACD-S versus ACD-L: A Substudy of a Randomized Trial

Devices used to deliver inhaled sedation increase dead space ventilation. We therefore compared ventilatory effects among isoflurane sedation via the Sedaconda ACD-S (internal volume: 50 mL), isoflurane sedation via the Sedaconda ACD-L (100 mL), and propofol sedation with standard mechanical ventilation with heat and moisture exchangers (HME). This is a substudy of a randomized trial that compared inhaled isoflurane sedation via the ACD-S or ACD-L to intravenous propofol sedation in 301 intensive care patients. Data from the first 24 h after study inclusion were analyzed using linear mixed models. Primary outcome was minute ventilation. Secondary outcomes were tidal volume, respiratory rate, arterial carbon dioxide pressure, and isoflurane consumption. In total, 151 patients were randomized to propofol and 150 to isoflurane sedation; 64 patients received isoflurane via the ACD-S and 86 patients via the ACD-L. While use of the ACD-L was associated with higher minute ventilation (average difference (95% confidence interval): 1.3 (0.7, 1.8) L/min, p < 0.001), higher tidal volumes (44 (16, 72) mL, p = 0.002), higher respiratory rates (1.2 (0.1, 2.2) breaths/min, p = 0.025), and higher arterial carbon dioxide pressures (3.4 (1.2, 5.6) mmHg, p = 0.002), use of the ACD-S did not significantly affect ventilation compared to standard mechanical ventilation and sedation. Isoflurane consumption was slightly less with the ACD-L compared to the ACD-S (-0.7 (-1.3, 0.1) mL/h, p = 0.022). The Sedaconda ACD-S compared to the ACD-L is associated with reduced minute ventilation and does not significantly affect ventilation compared to a standard mechanical ventilation and sedation setting. The smaller ACD-S is therefore the device of choice to minimize impact on ventilation, especially in patients with a limited ability to compensate (e.g., COPD patients). Volatile anesthetic consumption is slightly higher with the ACD-S compared to the ACD-L.

Volatile Sedation With Isoflurane in Neurocritical Care Patients After Poor-grade Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Volatile sedation after aneurysmal subarachnoid hemorrhage (aSAH) promises several advantages, but there are still concerns regarding intracranial hypertension due to vasodilatory effects. We prospectively analyzed cerebral parameters during the switch from intravenous to volatile sedation with isoflurane in patients with poor-grade (World Federation of Neurosurgical Societies grade 4-5) aSAH.

METHODS

Eleven patients were included in this prospective observational study. Between day 3 and 5 after admission, intravenous sedation was switched to isoflurane using the Sedaconda Anesthetic Conserving Device (Sedana Medical, Danderyd, Sweden). Intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygenation (PBrO2), cerebral mean flow velocities (MFVs; transcranial Doppler ultrasound) and regional cerebral oxygen saturation (rSO2, near-infrared spectroscopy monitoring), as well as cardiopulmonary parameters were assessed before and after the sedation switch (-12 to +12 hours). Additionally, perfusion computed tomography data during intravenous and volatile sedation were analyzed retrospectively for changes in cerebral blood flow.

RESULTS

There were no significant changes in mean ICP, CPP, and PBrO2 after the sedation switch to isoflurane. Mean rSO2 showed a non-significant trend towards higher values, and mean MFV in the middle cerebral arteries increased significantly after the initiation of volatile sedation. Isoflurane sedation resulted in a significantly increased norepinephrine administration. Despite an increase in mean inspiratory pressure, we observed a significant increase in mean partial arterial pressure of carbon dioxide.

CONCLUSIONS

Isoflurane sedation does not compromise ICP or cerebral oxygenation in poor-grade aSAH patients, but the significant depression of CPP could limit the use of volatiles in case of hemodynamic instability or high vasopressor demand.

Inhaled volatile anesthetic gas for severe bronchospasm in the emergency department

Bronchospasm is caused by reversible constriction of the smooth muscles of the bronchial tree. This causes obstruction of the lower airways, which is commonly seen at the emergency department (ED) in patients with acute exacerbation of asthma or chronic obstructive pulmonary disease. Ventilation may be difficult in mechanically intubated patients with severe bronchospasm due to airflow limitation, air trapping, and high airway resistance. The beneficial effects of volatile inhaled anesthetic gas had been reported due to its bronchodilation properties. In this case series, we would like to share our experience delivering inhaled volatile anesthetic gas via a conserving device for three patients with refractory bronchospasm at the ED. Inhaled anesthetic gas is safe, feasible and should be considered as an alternative rescue therapy for ventilated patients with severe lower airway obstruction.

Usefulness of Inhaled Sedation in Patients With Severe ARDS Due to COVID-19

BACKGROUND

Sedation in intensive care is fundamental for optimizing clinical outcomes. For many years the world has been facing high rates of opioid use, and to combat the increasing opioid addiction plans at both national and international level have been implemented.1 The COVID-19 pandemic posed a major challenge for health systems and also increased the use of sedatives and opioid analgesia for prolonged periods of time, and at high doses, in a significant proportion of patients. In our institutions, the shortage of many drugs for intravenous (IV) analgosedation forces us to alternatives to replace out-of-stock drugs or to seek sedation goals, which are difficult to obtain with traditional drugs at high doses.2 METHODS: This was an analytical retrospective cohort study evaluating the follow-up of subjects with inclusion criteria from ICU admission to discharge (alive or dead). Five end points were measured: need for high-dose opioids (≥ 200 µg/h), comparison of inhaled versus IV sedation of opioid analgesic doses, midazolam dose, need for muscle relaxant, and risk of delirium.

RESULTS

A total of 283 subjects were included in the study, of whom 230 were administered IV sedation and 53 inhaled sedation. In the inhaled sedation group, the relative risks (RRs) were 0.5 (95% CI 0.4-0.8, P = .045) for need of high-dose fentanyl, 0.3 (95% CI 0.20-0.45, P < .001) for need of muscle relaxant, and 0.8 (95% CI 0.61-1.15, P = .25) for risk of delirium. The median difference of fentanyl dose between the inhaled sedation and IV sedation groups was 61 µg/h or 1,200 µg/d (2.2 ampules/d, P < .001), and that of midazolam dose was 5.7 mg/h.

CONCLUSIONS

Inhaled sedation was associated with lower doses of opioids, benzodiazepines, and muscle relaxants compared to IV sedation. This therapy should be considered as an alternative in critically ill patients requiring prolonged ventilatory support and where IV sedation is not possible, always under adequate supervision of ICU staff.

Use of volatile anesthetics for sedation in the ICU during the COVID-19 pandemic: A national survey in France (VOL'ICU 2 study)

BACKGROUND

The COVID-19 pandemic has increased the number of patients in ICUs leading to a worldwide shortage of the intravenous sedative agents obligating physicians to find alternatives including inhaled sedation. Inhaled sedation in French ICU has been previously explored in 2019 (VOL'ICU study). This survey was designed to explore the use of inhaled sedation two years after our first survey and to evaluate how the COVID-19 pandemic has impacted the use of inhaled sedation.

METHODS

We designed a national survey, contacting medical directors of French ICUs between June and October 2021. Over a 50-item questionnaire, the survey covered the characteristics of the ICU, data on inhaled sedation, and practical aspects of inhaled ICU sedation for both COVID-19 and non-COVID-19 patients. Answers were compared with the previous survey, VOL'ICU.

RESULTS

Among the 405 ICUs contacted, 25% of the questionnaires were recorded. Most ICU directors (87%) knew about the use of inhaled ICU sedation and 63% of them have an inhaled sedation's device in their unit. The COVID-19 pandemic increased the use of inhaled sedation in French ICUs. The main reasons said by the respondent were "need for additional sedative" (62%), "shortage of intravenous sedatives" (38%) and "involved in a clinical trial" (30%). The main reasons for not using inhaled ICU sedation were "device not available" (76%), "lack of familiarity" (60%) and "no training for the teams" (58%). More than 70% of respondents were overall satisfied with the use of inhaled sedation. Almost 80% of respondents stated that inhaled sedation was a seducing alternative to intravenous sedation for management of COVID-19 patients.

CONCLUSION

The use of inhaled sedation in ICU has increased fastly in the last 2 years, and is frequently associated with a good satisfaction among the users. Even if the COVID-19 pandemic could have impacted the widespread use of inhaled sedation, it represents an alternative to intravenous sedation for more and more physicians.

The Future of Cardiothoracic Surgical Critical Care Medicine as a Medical Science: A Call to Action

Cardiothoracic surgical critical care medicine (CT-CCM) is a medical discipline centered on the perioperative care of diverse groups of patients. With an aging demographic and an increase in burden of chronic diseases the utilization of cardiothoracic surgical critical care units is likely to escalate in the coming decades. Given these projections, it is important to assess the state of cardiothoracic surgical intensive care, to develop goals and objectives for the future, and to identify knowledge gaps in need of scientific inquiry. This two-part review concentrates on CT-CCM as its own subspeciality of critical care and cardiothoracic surgery and provides aspirational goals for its practitioners and scientists. In part one, a list of guiding principles and a call-to-action agenda geared towards growth and promotion of CT-CCM are offered. In part two, an evaluation of selected scientific data is performed, identifying gaps in CT-CCM knowledge, and recommending direction to future scientific endeavors.

Safety and Feasibility of AnaConDa™ to Deliver Inhaled Isoflurane for Sedation in Patients Undergoing Elective Postoperative Mechanical Ventilation: A Prospective, Open-label, Interventional Trial (INSTINCT I Study)

Aim

Sedation is essential during invasive mechanical ventilation, and conventionally intravenous analgesic and sedative drugs are used. Sedation with inhaled anesthetics using anesthesia conserving device (ACD) is an alternative. There is no data on the safety and ease of use of AnaConDa™ from India.

Materials and methods

After IEC approval and informed consent, we used AnaConDa™-S for Isoflurane sedation in 50 hemodynamically stable (need for <0.5 µg/kg/min of Noradrenaline infusion), ASA I and II patients aged 18-80 years, undergoing elective mechanical ventilation for up to 24 hours after elective oncosurgeries. Patients with mental obtundation (GCS <14), or if pregnant, were excluded. The primary outcome was time spent between RASS scores of -3 and -4, while secondary outcomes were incidence of delirium, technical problems with AnaConDa™, and adverse systemic effects of isoflurane. Bolus doses of isoflurane 0.2-0.5 mL were given if the Richmond agitation sedation scale (RASS) score was not achieved.

Results

Fifty patients received isoflurane infusion for a median of 720 (IQR 630-900) minutes, and all remained in the target sedation range. Median time to awakening [19 (IQR, 5-85) minutes], to follow simple verbal commands [20 (IQR 5-180) minutes], and extubation after stopping the infusion of isoflurane was quick [100 (10-470) minutes]. All patients remained hemodynamically stable. None of the patients had delirium.

Conclusion

Target sedation levels were achieved with initial boluses of isoflurane using AnaConDa™-S. Isoflurane sedation delivery using AnaConDa™-S is safe and feasible.

How to cite this article

Kulkarni AP, Bhosale SJ, Kalvit KR, Sahu TK, Mohanty R, Dhas MM, et al. Safety and Feasibility of AnaConDa™ to Deliver Inhaled Isoflurane for Sedation in Patients Undergoing Elective Postoperative Mechanical Ventilation: A Prospective, Open-label, Interventional Trial (INSTINCT I Study). Indian J Crit Care Med 2022;26(8):906-912.

Evaluation of volatile sedation in the postoperative intensive care of patients recovering from heart valve surgery: protocol for a randomised, controlled, monocentre trial

INTRODUCTION

Patients undergoing heart valve surgery are predominantly transferred postoperatively to the intensive care unit (ICU) under continuous sedation. Volatile anaesthetics are an increasingly used treatment alternative to intravenous substances in the ICU. As subject to inhalational uptake and elimination, the resulting pharmacological benefits have been repeatedly demonstrated. Therefore, volatile anaesthetics appear suitable to meet the growing demands of fast-track cardiac surgery. However, their use requires special preparation at the bedside and trained medical and nursing staff, which might limit the pharmacological benefits. The aim of our work is to assess whether the temporal advantages of recovery under volatile sedation outweigh the higher effort of special preparation.

METHODS AND ANALYSIS

The study is designed to evaluate the differences between intravenous sedatives (n=48) and volatile sedatives (n=48) in continued intensive care sedation. This study will be conducted as a prospective, randomised, controlled, single-blinded, monocentre trial at a German university hospital in consenting adult patients undergoing heart valve surgery at a university hospital. This observational study will examine the necessary preparation time, staff consultation and overall feasibility of the chosen sedation method. For this purpose, the continuation of sedation in the ICU with volatile sedatives is considered as one study arm and with intravenous sedatives as the comparison group. Due to rapid elimination and quick awakening after the termination of sedation, closer consultation between the attending physician and the ICU nursing staff is required, in addition to a prolonged setup time. Study analysis will include the required setup time, time from admission to extubation as primary outcome and neurocognitive assessability. In addition, possible operation-specific (blood loss, complications), treatment parameters (catecholamine dosages, lung function) and laboratory results (acute kidney injury, acid base balance (lactataemia), liver failure) as influencing factors will be collected. The study-relevant data will be extracted from the continuous digital records of the patient data management system after the patient has been discharged from the ICU. For statistical evaluation, 95% CIs will be calculated for the median time to extubation and neurocognitive assessability, and the association will be assessed with a Cox regression model. In addition, secondary binary outcome measures will be evaluated using Fisher's exact tests. Further descriptive and exploratory statistical analyses are also planned.

ETHICS AND DISSEMINATION

The study was approved by the Institutional Ethics Board of the University of Frankfurt, Germany (#20-1050). Informed consent of all individual patients will be obtained before randomisation. Results will be disseminated via publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

Clinical trials registration (NCT04958668) was completed on 1 July 2021.

Intensive care nurses' experiences using volatile anaesthetics in the intensive care unit: An exploratory study

OBJECTIVE

To explore the experiences intensive care nurses have with volatile anaesthetics in the intensive care unit.

RESEARCH METHODOLOGY AND DESIGN

A qualitative exploratory and descriptive design was used. Data were collected in 2019 from individual interviews with nine intensive care nurses, who were recruited using purposive sampling. Data were analysed using systematic text condensation.

SETTING

The study was undertaken in two general intensive care units from different university hospitals in Norway where volatile anaesthetics were utilised.

FINDINGS

Three categories emerged from the data analysis: experiencing the benefits of volatile anaesthetics; coping with unfamiliarity in handling volatile anaesthetics; and meeting challenges related to volatile anaesthetics in practice.

CONCLUSION

The intensive care nurses had positive experiences related to administering volatile anaesthetics in the intensive care unit and responded positively to the prospect of using it more often. Because volatile anaesthetics were rarely used in their units, the participants felt uncertain regarding its use due to unfamiliarity. Collegial support and guidelines were perceived as pivotal in helping them cope with this uncertainty. The participants also experienced several challenges in using volatile anaesthetics in the intensive care unit, with ambient pollution being regarded as the main challenge.

Extracorporeal membrane oxygenation and inhaled sedation in coronavirus disease 2019-related acute respiratory distress syndrome

Coronavirus disease 2019 (COVID-19) related acute respiratory distress syndrome (ARDS) is a severe complication of infection with severe acute respiratory syndrome coronavirus 2, and the primary cause of death in the current pandemic. Critically ill patients often undergo extracorporeal membrane oxygenation (ECMO) therapy as the last resort over an extended period. ECMO therapy requires sedation of the patient, which is usually achieved by intravenous administration of sedatives. The shortage of intravenous sedative drugs due to the ongoing pandemic, and attempts to improve treatment outcome for COVID-19 patients, drove the application of inhaled sedation as a promising alternative for sedation during ECMO therapy. Administration of volatile anesthetics requires an appropriate delivery. Commercially available ones are the anesthetic gas reflection systems AnaConDa^® and MIRUS^TM, and each should be combined with a gas scavenging system. In this review, we describe respiratory management in COVID-19 patients and the procedures for inhaled sedation during ECMO therapy of COVID-19 related ARDS. We focus particularly on the technical details of administration of volatile anesthetics. Furthermore, we describe the advantages of inhaled sedation and volatile anesthetics, and we discuss the limitations as well as the requirements for safe application in the clinical setting.

Profound decrease of liver maximum function capacity test of isoflurane sedated patients: A report of three cases

LiMAx 13C-methacetin breath test results should be interpreted with caution in patients sedated with isoflurane.

TIVA versus Inhalational Agents for Pediatric Cardiac Intensive Care

The field of pediatric intensive care has come a long way, especially with the recognition that adequate sedation and analgesia form an imperative cornerstone of patient management. With various drugs available for the same, the debate continues as to which is the better: total intravenous anesthesia (TIVA) or inhalational agents. While each have their own advantages and disadvantages, in the present era of balance toward the IV agents, we should not forget the edge our volatile agents (VAs) might have in special scenarios. And ultimately as anesthesiologists, let us not forget that be it knob and dial, or syringe and plunger, our aim is to put pain to sleep and awaken a new faith to breathe.

Sevoflurane Exerts Protective Effects in Murine Peritonitis-induced Sepsis via Hypoxia-inducible Factor 1α/Adenosine A2B Receptor Signaling

BACKGROUND

Sepsis is one of the leading causes of mortality in intensive care units, and sedation in the intensive care unit during sepsis is usually performed intravenously. The inhalative anesthetic sevoflurane has been shown to elicit protective effects in various inflammatory studies, but its role in peritonitis-induced sepsis remains elusive. The hypothesis was that sevoflurane controls the neutrophil infiltration by stabilization of hypoxia-inducible factor 1α and elevated adenosine A2B receptor expression.

METHODS

In mouse models of zymosan- and fecal-induced peritonitis, male mice were anesthetized with sevoflurane (2 volume percent, 30 min) after the onset of inflammation. Control animals received the solvent saline. The neutrophil counts and adhesion molecules on neutrophils in the peritoneal lavage of wild-type, adenosine A2B receptor -/-, and chimeric animals were determined by flow cytometry 4 h after stimulation. Cytokines and protein release were determined in the lavage. Further, the adenosine A2B receptor and its transcription factor hypoxia-inducible factor 1α were evaluated by real-time polymerase chain reaction and Western blot analysis 4 h after stimulation.

RESULTS

Sevoflurane reduced the neutrophil counts in the peritoneal lavage (mean ± SD, 25 ± 17 × 105vs. 12 ± 7 × 105 neutrophils; P = 0.004; n = 19/17) by lower expression of various adhesion molecules on neutrophils of wild-type animals but not of adenosine A2B receptor -/- animals. The cytokines concentration (means ± SD, tumor necrosis factor α [pg/ml], 523 ± 227 vs. 281 ± 101; P = 0.002; n = 9/9) and protein extravasation (mean ± SD [mg/ml], 1.4 ± 0.3 vs. 0.8 ± 0.4; P = 0.002; n = 12/11) were also lower after sevoflurane only in the wild-type mice. Chimeric mice showed the required expression of the adenosine A2B receptor on the hematopoietic and nonhematopoietic compartments for the protective effects of the anesthetic. Sevoflurane induced the expression of hypoxia-inducible factor 1α and adenosine A2B receptor in the intestine, liver, and lung.

CONCLUSIONS

Sevoflurane exerts various protective effects in two murine peritonitis-induced sepsis models. These protective effects were linked with a functional adenosine A2B receptor.

EDITOR’S PERSPECTIVE

Reflection efficiencies of AnaConDa-S and AnaConDa-100 for isoflurane under dry laboratory and simulated clinical conditions: a bench study using a test lung

Background: Adequate sedation is important for the treatment of ICU patients. AnaConDa (Anesthetic-Conserving-Device; ACD; Sedana Medical, Sweden), connected between ventilator and the patient, retains isoflurane during expiration, and releases it back during inspiration. The reflection efficiency (Ref_Eff) corresponds to the percentage of expired anesthetic molecules that are re-inspired. We compared Ref_Eff of AnaConDa-S (ACD-50) and AnaConDa-100 (ACD-100) under laboratory (DRY) and simulated clinical conditions (CLIN) using a test lung.Methods: Measurements were made under DRY and CLIN, with different tidal volumes (TV: 300 mL & 500 mL) and infusion rates (0.5-10 mL·h^-1). Ref_Eff was calculated from the isoflurane concentration in the test-lung (C_ISO) and plotted against the anesthetic vapor volume exhaled in one breath (V-exh = C_ISO·TV).Results: DRY: Ref_Eff of both devices was ≈90% over a wide range of V-exh, but decreased when V-exh exceeded 5-7 mL (ACD-50) or 10-15 mL (ACD-100).CLIN: Ref_Eff of ACD-50 was 70-80% (ACD-100: 80-90%), decreasing gradually with increasing V-exh. For 1 Vol.% isoflurane at TV500, the infusion rate with ACD-50 was twofold higher compared to ACD-100 (4 versus 2 mL·h^-1).Conclusion: Under DRY and concentrations <1.5 Vol.%, Ref_Eff of both devices is around 90%. Under CLIN, ACD-100 performs better with Ref_Eff between 80% and 90% (ACD-50:70-80%), decreasing with increased vapor volume exhaled in one breath.

A multimodal sevoflurane-based sedation regimen in combination with targeted temperature management in post-cardiac arrest patients reduces the incidence of delirium: An observational propensity score-matched study

BACKGROUND

Recent studies suggest that volatile anaesthetics are safe, efficient, and reliable alternatives to the use of intravenous anaesthetics for out-of-hospital cardiac arrest (OHCA) patients admitted to the intensive care unit (ICU). We hypothesised that volatile anaesthetics may reduce the incidence of delirium rather than intravenous sedatives. This retrospective study aimed to investigate whether sevoflurane combined with higher targeted temperature management could decrease the incidence of delirium when compared with intravenous anaesthetics with lower targeted temperature management.

METHODS

Using a propensity score-matched analysis, we retrospectively compared a target temperature management (32-34 °C) method along with intravenous sedation (TTM-33/IV) and a modified target temperature management (34-36 °C) method along with sevoflurane sedation (mTTM-36/sevo). We used the confusion assessment method for the ICU to measure the incidence of delirium. We calculated the time-dependent risk on delirium using the multivariate Cox regression model.

RESULTS

The incidence of delirium was significantly lower (p = 0.001) in OHCA patients of the mTTM-36/sevo group (9/56, 16.1%) than in those of the TTM-33/IV group (25/67, 37.3%). Mechanical ventilation and lengths of stay in the ICU (p < 0.001) and hospital stay (p = 0.04) were shorter in the mTTM-36/sevo group. Patients in the TTM-33/IV group required more midazolam, propofol, and fentanyl. We observed no significant difference in mortality.

CONCLUSION

A multimodal sevoflurane-based sedation regimen together with targeted temperature management resulted in a lower incidence of delirium and a shorter duration for mechanical ventilation and ICU length of stay than did the treatment with intravenous sedation combined with the classical cooling protocol.

Inhalation sedation for postoperative patients in the intensive care unit: initial sevoflurane concentration and comparison of opioid use with propofol sedation

Background

Although the use of volatile sedatives in the intensive care unit (ICU) is increasing in Europe, it remains infrequent in Asia. Therefore, there are no clinical guidelines available. This study investigates the proper initial concentration of sevoflurane, a volatile sedative that induces a Richmond agitation-sedation scale (RASS) score of –2 to –3, in patients who underwent head and neck surgery with tracheostomy. We also compared the amount of postoperative opioid consumption between volatile and intravenous (IV) sedation.

Methods

We planned a prospective study to determine the proper initial sevoflurane concentration and a retrospective analysis to compare postoperative opioid consumption between volatile sedation and propofol sedation. Patients scheduled for head and neck surgery with tracheostomy and subsequent postoperative sedation in the ICU were enrolled.

Results

In this prospective study, the effective dose 50 (ED50) of initial end-tidal sevoflurane concentration was 0.36% (95% confidence interval [CI], 0.20 to 0.60%), while the ED 95 was 0.69% (95% CI, 0.60 to 0.75%) based on isotonic regression methods. In this retrospective study, remifentanil consumption during postoperative sedation was significantly lower in the sevoflurane group (2.52±1.00 µg/kg/hr, P=0.001) than it was in the IV propofol group (3.66±1.30 µg/kg/hr).

Conclusions

We determined the proper initial end-tidal concentration setting of sevoflurane for patients with tracheostomy who underwent head and neck surgery. Postoperative sedation with sevoflurane appears to be a valid and safe alternative to IV sedation with propofol.

Posteriores reversibles enzephalopathisches Syndrom und Hyperammonämie: zwei Entitäten für Hirnödem und Status epilepticus bei einer Patientin nach Lungentransplantation

Fünf Wochen nach primär erfolgreicher Lungentransplantation entwickelt eine 58-jährige Patientin rasch progrediente neurologische Symptome mit Vigilanzverlust. Als Ursachen können einerseits ein posteriores reversibles enzephalopathisches Syndrom (PRES) unter Therapie mit Tacrolimus, andererseits eine schwere Hyperammonämie durch Sepsis mit Ureaplasma urealyticum identifiziert werden. Infektionen mit Ureaplasmen, die Ammoniak als Stoffwechselprodukt produzieren, werden durch spezifische „polymerase chain reaction“(PCR, Polymerase Kettenreaktion)-Verfahren zunehmend bei Immunsupprimierten identifiziert und sollten grundsätzlich als Ursache für unklare neurologische Symptome in Betracht gezogen werden.

Advances in vaporisation: A narrative review

The output of inhalational agents from modern vaporisers are both electronically and pneumatically controlled. They are designed to deliver set agent concentrations accurately with low fresh gas flows and possess enhanced safety features. The purpose of this review article is to give an overview of three modern vaporisers, namely, the Aladin cassette vaporiser, injection vaporisers and AnaConDa™. The Aladin cassette is integrated with Datex Ohmeda S/5 ADU and GE Aisys anaesthesia machines. The electronic vapour control unit is incorporated within the anaesthesia machine. The agent specific cassettes act as a detachable vaporising chamber. The system can work as a variable bypass and measured flow vaporiser but requires a power supply to function. Injection vaporisers can achieve the set end-tidal agent concentration very rapidly with even metabolic flow rates. Hence, anaesthetic depth can be rapidly altered with minimal wastage and theatre pollution. The two types of injection vaporisers, namely, Maquet and DIVA™ are customised to function with Maquet FLOW-i and the Drager Zeus anaesthesia machine, respectively. AnaConDa™ is a combination of vaporiser and humidity and moisture exchange filter which can be fitted in the ventilatory circuit. It is primarily designed for use in intensive care for sedation and out of operating room use.

Does volatile sedation with sevoflurane allow spontaneous breathing during prolonged prone positioning in intubated ARDS patients? A retrospective observational feasibility trial

Background

Lung-protective ventilation and prolonged prone positioning (PP) are presented as essential in treating acute respiratory distress syndrome (ARDS). The optimal respirator mode, however, remains controversial. Pressure-supported spontaneous breathing (PS) during ARDS provides several advantages, but is difficult to achieve during PP because of respiratory depression as a side effect of sedative drugs. This study was designed to evaluate the feasibility and safety of PS during PP in ARDS patients sedated with inhaled sevoflurane.

Results

Overall, we have observed 4339 h of prone positioning in 62 patients who had a median of four prone episodes during treatment. Within 3948 h (91%), patients were successfully brought into a pressure-supported spontaneous breathing mode. The median duration of each prone episode was 17 h (IQR 3). Median duration of pressure-supported spontaneous breathing per episode was 16 h (IQR 5). Just one self-extubation occurred during 276 episodes of PP.

Conclusions and implications

Pressure-supported spontaneous breathing during prolonged prone positioning in intubated ARDS patients with or without ECMO can be achieved during volatile sedation with sevoflurane. This finding may provide a basis upon which to question the latest dogma in ARDS treatment. Our concept must be further investigated and compared to controlled ventilation with regard to driving pressure, lung-protective parameters, muscle weakness and mortality before it can be routinely applied.

Comparison of the use of AnaConDa® versus AnaConDa-S® during the post-operative period of cardiac surgery under standard conditions of practice

Changes have been made to the AnaConDa device (Sedana Medical, Stockholm, Sweden), decreasing its size to reduce dead space and carbon dioxide (CO₂) retention. However, this also involves a decrease in the surface area of the activated carbon filter. The CO₂ elimination and sevoflurane (SEV) reflection of the old device (ACD-100) were thus compared with the new version (ACD-50) in patients sedated after coronary artery bypass graft surgery. After ERC approval and written informed consent, 23 patients were sedated with SEV, using first the ACD-100 and then the ACD-50 for 60 min each. With each device, patients were ventilated with tidal volumes (TV) of 5 ml/kg of ideal body weight for the first 30 min, and with 7 ml/kg for the next 30 min. Ventilation parameters, arterial blood gases, Bispectral-Index™ (BIS, Aspect Medical Systems Inc., Newton, MA, USA), SEV concentrations exhaled by the patient (SEV-exhaled) and from the expiratory hose (SEV-lost) were recorded every 30 min. A SEV reflection index was calculated: SRI [%] = 100 × (1 − (SEV-lost/SEV-exhaled)). Data were compared using ANOVA with repeated measurements and Student’s T-tests for pairs. Respiratory rates, tidal and minute volumes were not significantly different between the two devices. End tidal and arterial CO₂ partial pressures were significantly higher with the ACD-100 as compared with the ACD-50. SEV infusion rate remained constant. SEV reflection was higher (SRI: ACD-100 vs. ACD-50, TV 5 ml/kg: 95.29 ± 6.45 vs. 85.54 ± 11.15, p = 0.001; 7 ml/kg: 93.42 ± 6.55 vs. 88.77 ± 12.26, p = 0.003). BIS was significantly lower when using the higher TV (60.91 ± 9.99 vs. 66.57 ± 8.22, p = 0.012), although this difference was not clinically relevant. During postoperative sedation, the use of ACD-50 significantly reduced CO₂ retention. SEV reflection was slightly reduced. However, patients remained sufficiently sedated without increasing SEV infusion.

EOY summary 2018

Clinical monitoring and technology are at the heart of anesthesiology, and new technological developments will help to define how anesthesiology will evolve as a profession. Anesthesia related research published in the JCMC in 2018 mainly pertained to ICU sedation with inhaled agents, anesthesia workstation technology, and monitoring of different aspects of depth of anesthesia.