Use of the AnaConDa anaesthetic delivery system to treat life-threatening asthma

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.

VV-ECMO as bridge and safety net for successful therapeutic polypragmasy in a case of influenza-triggered near-fatal asthma

Key Clinical Message

In near-fatal asthma, the combination of ECMO therapy and isoflurane application via an intensive care ventilator with an anesthetic conservation device represents a therapeutic combination in seemingly hopeless clinical situations.

Abstract

We report a case of an adult patient with near-fatal asthma, who was implanted venovenous extracorporeal membrane oxygenation in an extern hospital before transfer to our tertiary center. After 13 days and various therapeutic approaches, including inhaled isoflurane therapy via an anesthetic-conserving device, the patient was decannulated and extubated 3 days later.

[New technical developments for inhaled sedation]

The circle system has been in use for more than 100 years, whereas the first clinical application of an anaesthetic reflector was reported just 15 years ago. In the circle system, all breathing gas is rebreathed after carbon dioxide absorption. A reflector, on the other hand, with the breathing gas flowing to and fro, specifically retains the anaesthetic during expiration and resupplies it during the next inspiration. A high reflection efficiency (number of molecules resupplied/number of molecules exhaled, RE 80-90%) decreases consumption. In analogy to the fresh gas flow of a circle system, pulmonary clearance ((1-RE) × minute ventilation) defines the opposition between consumption and control of the concentration.It was not until reflection systems became available that volatile anaesthetics were used routinely in some intensive care units. Their advantages, such as easy handling, and better ventilatory capabilities of intensive care versus anaesthesia ventilators, were basic preconditions for this. Apart from AnaConDa™ (Sedana Medical, Uppsala, Sweden), the new MIRUS™ system (Pall Medical, Dreieich, Germany) represents a second, more sophisticated commercially available system.Organ protective effects, excellent control of sedation, and dose-dependent deep sedation while preserving spontaneous breathing with hardly any accumulation or induction of tolerance, make volatile anaesthetics an interesting alternative, especially for patients needing deep sedation or when intravenous drugs are no longer efficacious.But obviously, the outcome is most important. We know that deep intravenous sedation increases mortality, whereas inhalational sedation could prove beneficial. We now need prospective clinical trials examining mortality, but also the psychological outcome of those most critically ill patients sedated by inhalation or intravenously.

Survival after long-term isoflurane sedation as opposed to intravenous sedation in critically ill surgical patients: Retrospective analysis

BACKGROUND

Isoflurane has shown better control of intensive care sedation than propofol or midazolam and seems to be a useful alternative. However, its effect on survival remains unclear.

OBJECTIVE

The objective of this study is to compare mortality after sedation with either isoflurane or propofol/midazolam.

DESIGN

A retrospective analysis of data in a hospital database for a cohort of consecutive patients.

SETTING

Sixteen-bed interdisciplinary surgical ICU of a German university hospital.

PATIENTS

Consecutive cohort of 369 critically ill surgical patients defined within the database of the hospital information system. All patients were continuously ventilated and sedated for more than 96 h between 1 January 2005 and 31 December 2010. After excluding 169 patients (93 >79 years old, 10 <40 years old, 46 mixed sedation, 20 lost to follow-up), 200 patients were studied, 72 after isoflurane and 128 after propofol/midazolam.

INTERVENTIONS

Sedation with isoflurane using the AnaConDa system compared with intravenous sedation with propofol or midazolam.

MAIN OUTCOME MEASURES

Hospital mortality (primary) and 365-day mortality (secondary) were compared with the Kaplan-Meier analysis and a log-rank test. Adjusted odds ratios (ORs) [with 95% confidence interval (95% CI)] were calculated by logistic regression analyses to determine the risk of death after isoflurane sedation.

RESULTS

After sedation with isoflurane, the in-hospital mortality and 365-day mortality were significantly lower than after propofol/midazolam sedation: 40 versus 63% (P = 0.005) and 50 versus 70% (P = 0.013), respectively. After adjustment for potential confounders (coronary heart disease, chronic obstructive pulmonary disease, acute renal failure, creatinine, age and Simplified Acute Physiology Score II), patients after isoflurane were at a lower risk of death during their hospital stay (OR 0.35; 95% CI 0.18 to 0.68, P = 0.002) and within the first 365 days (OR 0.41; 95% CI 0.21 to 0.81, P = 0.010).

CONCLUSION

Compared with propofol/midazolam sedation, long-term sedation with isoflurane seems to be well tolerated in this group of critically ill patients after surgery.

Sevoflurane therapy for life-threatening acute severe asthma: a case report

INTRODUCTION

Acute severe asthma is a life-threatening form of bronchial constriction in which the progressively worsening airway obstruction is unresponsive to the usual appropriate bronchodilator therapy. Pathophysiological changes restrict airflow, which leads to premature closure of the airway on expiration, impaired gas exchange, and dynamic hyperinflation ("air-trapping"). Additionally, patients suffering from asthma for a prolonged period of time usually have serious comorbidities. These conditions constitute a challenge during the treatment of this disease. Therapeutic interventions are designed to reduce airway resistance and improve respiratory status. To achieve therapeutic goals, appropriate bronchodilator treatment is indispensable, and mechanical ventilation under adequate sedation may also be required. The volatile anesthetic agent, sevoflurane, meets both criteria; therefore, its use can be beneficial and should be considered.

CASE PRESENTATION

A 67-yr-old Caucasian male presented with acute life-threatening asthma provoked by an assumed upper airway infection and non-steroidal anti-inflammatory drug antipyretics, complicated by chronic atrial fibrillation and hemodynamic instability. Due to frequent premature ventricular contractions, conventional treatment was considered unsafe and discontinued, and sevoflurane inhalation was initiated via the AnaConDa (Anaesthetic Conserving Device). Symptoms of life-threatening bronchospasm resolved, and the patient's respiratory status improved within hours. Adequate sedation was also achieved without any hemodynamic adverse effects.

CONCLUSION

The volatile anesthetic agent, sevoflurane, is used widely in anesthesia practice. Its utility for treatment of refractory bronchospasm has been appreciated for years; however, its administration was difficult within the environment of the intensive care unit due to the need for an anesthesia machine and a scavenging system. The introduction of the AnaConDa eliminates these obstacles and makes the use of sevoflurane safe and simple. Our case report reveals the potential of sevoflurane as a "two-in-one" (bronchodilator and sedative) drug to treat a severe acute asthma attack.

Delayed cerebral ischaemia after subarachnoid haemorrhage: looking beyond vasospasm

Despite improvements in the clinical management of aneurysmal subarachnoid haemorrhage over the last decade, delayed cerebral ischaemia (DCI) remains the single most important cause of morbidity and mortality in those patients who survive the initial bleed. The pathological mechanisms underlying DCI are still unclear and the calcium channel blocker nimodipine remains the only therapeutic intervention proven to improve functional outcomes after SAH. The recent failure of the drug clazosentan to improve functional outcomes despite reducing vasoconstriction has moved the focus of research into DCI away from cerebral artery constriction towards a more multifactorial aetiology. Novel pathological mechanisms have been suggested, including damage to cerebral tissue in the first 72 h after aneurysm rupture ('early brain injury'), cortical spreading depression, and microthrombosis. A greater understanding of the significance of these pathophysiological mechanisms and potential genetic risk factors is required, if new approaches to the prophylaxis, diagnosis, and treatment of DCI are to be developed. Furthermore, objective and reliable biomarkers are needed for the diagnosis of DCI in poor grade SAH patients requiring sedation and to assess the efficacy of new therapeutic interventions. The purpose of this article is to appraise these recent advances in research into DCI, relate them to current clinical practice, and suggest potential novel avenues for future research.

[Functioning of the anaesthetic conserving device: aspects to consider for use in inhalational sedation]

The new anaesthetic conserving device (ACD) allows the use of isoflurane and sevoflurane without classical anaesthesia workstations. Volatile anaesthetic exhaled by the patient is absorbed by a reflector and released to the patient during the next inspiration. Liquid anaesthetic is delivered via a syringe pump. Currently the use of the ACD is spreading among European intensive care units (ICU). This article focuses on the functioning of the device and on particularities which are important to consider. The ACD constantly reflects 90% of the exhaled anaesthetic back to the patient, but if one exhaled breath contains more than 10 ml of anaesthetic vapour (e.g. >1 vol% in 1,000 ml), the capacity of the reflector will be exceeded and relatively more anaesthetic will be lost to the patient. This spill over decreases efficiency but it also contributes to safety as very high concentrations are averted. Compared to classical anaesthesia systems the ACD used in conjunction with ICU ventilators offers advantages in the ICU setting: investment costs are low, carbon dioxide absorbent is not needed, breathing comfort is higher, anaesthetic consumption is low (equal to an anaesthesia circuit with a fresh gas flow of approximately 1 l/min) and anaesthetic concentrations can be controlled very quickly (increased by small boluses and decreased by removal of the ACD). On the other hand, case costs are higher (single patient use) and a dead space of 100 ml is added. There are pitfalls: by a process called auto-pumping, expansion of bubbles inside the syringe may lead to uncontrolled anaesthetic delivery. Auto-pumping is provoked by high positioning of the syringe pump, heat and prior cooling of the liquid anaesthetic. Inherent to the device is an early inspiratory concentration peak and an end-inspiratory dip which may mislead commonly used gas monitors. Workplace concentrations can be minimized by proper handling, a sufficient turnover of room air is important and gas from the expiration port of the ventilator should be scavenged. Inhalational compared to intravenous ICU sedation offers the advantages of better control of the sedation level, online drug monitoring, no accumulation in patients with renal or hepatic insufficiency and bronchodilation. With a lowered opioid dose spontaneous breathing and intestinal motility are well preserved. A clinical algorithm for the care of patients with respiratory insufficiency including inhalational sedation is proposed. Inhalational sedation with isoflurane has been widely used for more than 20 years in many countries and even for periods of up to several weeks. In the German S3 guidelines for the management of analgesia, sedation and delirium in intensive care (Martin et al. 2010), inhalational sedation is mentioned as an alternative sedation method for patients ventilated via an endotracheal tube or a tracheal cannula. Nevertheless, isoflurane is not officially licensed for ICU sedation and its use is under the responsibility of the prescribing physician.

[Severe acute asthma: isoflurane administration via AnaConDa™, is it safe?]

Standard treatments against severe acute asthma can be insufficient and need salvation treatments, such as isoflurane delivery. These treatments have not been much assessed and could lead to unrecognized side-effects. We report the case of a young man who suffered from intracranial hypertension associated with severe hypercapnia during the delivery of isoflurane via the system AnaConDa™ or Anaesthetic Conserving Device™ (ACD) (Sedama Medical). The rising of PaCO(2) appears to be linked to an ACD-dependent increase in the dead space.

Technical performance and reflection capacity of the anaesthetic conserving device--a bench study with isoflurane and sevoflurane

Objective

The anaesthetic conserving device (AnaConDa^®, Sedana Medical, Sundbyberg, Sweden) facilitates administration of isoflurane or sevoflurane by liquid infusion. An anaesthetic reflector inside the device conserves exhaled anaesthetic and re-supplies it during inspiration. In this bench study, we examined the influence of infusion rates and ventilatory settings on the resulting anaesthetic concentrations on patient (C_pat) and ventilator side of the reflector (C_loss) to describe its technical performance.

Methods

A Puritan Bennett 840 ICU ventilator (Pleasanton, US), AnaConDa^®, and a test lung (3 l-chloroprene-bag) were assembled. Infusion rates (IR, 0.2-50 ml h^-), respiratory rates (RR, 5-40 breaths min^-1), and tidal volumes (V_T, 0.3, 0.5, and 1.0 l) were varied. C_pat was measured via a thin catheter in the middle of the 3 l-bag in steady state (online data storage and averaging over >10 min). C_loss was calculated from IR (to yield the volume of vapour per unit of time), and expired minute volume (in which the vapour is diluted) on the assumption that, in the steady state, input by liquid infusion equals output through the reflector.

Results

At lower concentrations (C_pat< 1 vol%) the ratio C_loss/C_pat was constant (R_C = 0.096 ±±0.012) for all combinations of IR, RR and V_T, both for isoflurane and sevoflurane. The device could efficiently reflect up to 10 ml vapour per breath (e.g. 2 vol% in 0.5 l). When exceeding this capacity, surplus vapour “spilled over” and R_C markedly increased indicating decreased performance.

Conclusions

The triple product minute volume times R_C times C_pat describes anaesthetic losses through the reflector. It can easily be calculated as long as the 10 ml reflection capacity is not exceeded and thus R_C is constant. Increased minute ventilation necessitates increasing the IR to keep C_pat constant. When using large V_T and high C_pat “spill over” occurs. This effect offers some protection against an inadvertent overdose.

[Helium-sevoflurane association: a rescue treatment in case of acute severe asthma]

We report the case of a severe acute asthma, which required, after optimal medical therapy, helium and sevoflurane CO-administration after tracheal intubation. The Anesthetic Conserving Device allowed sevoflurane use with intensive care unit's ventilator. The helium-sevoflurane association was maintained during 9 days to decrease the bronchospasm, waiting for the efficiency of an aetiologic treatment. We discuss the suitability of this association to treat severe acute asthma, and its administration modalities.

Active Gas Scavenging is Unnecessary When Using the AnaConDa Volatile Agent Delivery System

The AnaConDa filter system has been used in intensive care units (ICUs) to deliver low concentrations of volatile anaesthetic agents to treat severe airflow obstruction and for sedation. The manufacturer and a recently published review recommend the use of a scavenging system with the device. It is unclear from the literature what levels of volatile agent staff are exposed to when the device is being used in ICU without a scavenger. We carried out an observational study requested by the local occupational health department to measure the levels of ICU staff exposure to isoflurane when the AnaConDa delivery system was used to treat asthma. This study was carried out using an ambient air analyser while the patient was receiving therapeutic levels of isoflurane via the AnaConDa device. We conclude that gas scavenging may not be necessary when using the AnaConDa device to deliver therapeutic doses of isoflurane.