The effect of isoflurane, halothane, sevoflurane, and thiopental/nitrous oxide on respiratory system resistance after tracheal intubation

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.

Sedation for Patients with Sepsis: Towards a Personalised Approach

This article looks at the challenges of sedoanalgesia for sepsis patients, and argues for a personalised approach. Sedation is a necessary part of treatment for patients in intensive care to reduce stress and anxiety and improve long-term prognoses. Sepsis patients present particular difficulties as they are at increased risk of a wide range of complications, such as multiple organ failure, neurological dysfunction, septic shock, ARDS, abdominal compartment syndrome, vasoplegic syndrome, and myocardial dysfunction. The development of any one of these complications can cause the patient's rapid deterioration, and each has distinct implications in terms of appropriate and safe forms of sedation. In this way, the present article reviews the sedative and analgesic drugs commonly used in the ICU and, placing special emphasis on their strategic administration in sepsis patients, develops a set of proposals for sedoanalgesia aimed at improving outcomes for this group of patients. These proposals represent a move away from simplistic approaches like avoiding benzodiazepines to more "objective-guided sedation" that accounts for a patient's principal pathology, as well as any comorbidities, and takes full advantage of the therapeutic arsenal currently available to achieve personalised, patient-centred treatment goals.

Perioperative Care of the Pediatric Patient and an Algorithm for the Treatment of Intraoperative Bronchospasm

Asthma remains a common comorbid condition in patients presenting for anesthetic care. As a chronic inflammatory disease of the airway, asthma is known to increase the risk of intraoperative bronchospasm. As the incidence and severity of asthma and other chronic respiratory conditions that alter airway reactivity is increasing, a greater number of patients at risk for perioperative bronchospasm are presenting for anesthetic care. As bronchospasm remains one of the more common intraoperative adverse events, recognizing and mitigating preoperative risk factors and having a pre-determined treatment algorithm for acute events are essential to ensuring effective resolution of this intraoperative emergency. The following article reviews the perioperative care of pediatric patients with asthma, discusses modifiable risk factors for intraoperative bronchospasm, and outlines the differential diagnosis of intraoperative wheezing. Additionally, a treatment algorithm for intraoperative bronchospasm is suggested.

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.

Anesthetic considerations in children with asthma

Due to the high prevalence of asthma and general airway reactivity, anesthesiologists frequently encounter children with asthma or asthma-like symptoms. This review focuses on the epidemiology, the underlying pathophysiology, and perioperative management of children with airway reactivity, including controlled and uncontrolled asthma. It spans from preoperative optimization to optimized intraoperative management, airway management, and ventilation strategies. There are three leading causes for bronchospasm (1) mechanical (eg, airway manipulation), (2) non-immunological anaphylaxis (anaphylactoid reaction), and (3) immunological anaphylaxis. Children with increased airway reactivity may benefit from a premedication with beta-2 agonists, non-invasive airway management, and deep removal of airway devices. While desflurane should be avoided in pediatric anesthesia due to an increased risk of bronchospasm, other volatile agents are potent bronchodilators. Propofol is superior in blunting airway reflexes and, therefore, well suited for anesthesia induction in children with increased airway reactivity.

Volatile anesthetic agents for life-threatening pediatric asthma: A multicenter retrospective cohort study and narrative review

BACKGROUND

Volatile anesthetic agents are described as rescue therapy for children invasively ventilated for critical asthma. Yet, data are currently limited to case series.

AIMS

Using the Virtual Pediatric Systems database, we assessed children admitted to a pediatric intensive care unit invasively ventilated for life-threatening asthma and hypothesized ventilation duration and mortality rates would be lower for subjects exposed to volatile anesthetics compared with those without exposure.

METHODS

We performed a multicenter retrospective cohort study among nine institutions including children 5-17 years of age invasively ventilated for asthma from 2013 to 2019 with and without exposure to volatile anesthetics. Primary outcomes were ventilation duration and mortality. Secondary outcomes included patient characteristics, length of stay, and anesthetic-related adverse events. A subgroup analysis was performed evaluating children intubated ≥2 days.

RESULTS

Of 203 children included in study, there were 29 (14.3%) with and 174 (85.7%) without exposure to volatiles. No differences in odds of mortality (1.1, 95% CI: 0.3-3.9, p > .999) were observed. Subjects receiving volatiles experienced greater median difference in length of stay (4.8, 95% CI: 1.9-7.8 days, p < .001), ventilation duration (2.3, 95% CI: 1-3.3 days, p < .001), and odds of extracorporeal life support (9.1, 95% CI: 1.9-43.2, p = .009) than those without volatile exposure. For those ventilated ≥2 days, no differences were detected in mortality, ventilation duration, length of stay, arrhythmias, or acute renal failure. However, the odds of extracorporeal life support remained greater for those receiving volatiles (7.6, 95% CI: 1.3-44.5, p = .027). No children experienced malignant hyperthermia or hepatic failure after volatile exposure.

CONCLUSIONS

For intubated children for asthma, no differences in mechanical ventilation duration or mortality between those with and without volatile anesthetic exposure were observed. Although volatiles may represent a viable rescue therapy for severe cases of asthma, definitive, and prospective trials are still needed.

Perioperative management of patients with asthma during elective surgery: A systematic review

Asthma is one of the commonest respiratory illnesses among elderly patients undergoing surgery. Detailed preoperative assessment, pharmacotherapy and safe anaesthetic measures throughout perioperative period are the keys to decrease complications. Resistance to expiratory airflow results in positive alveolar pressures at the end of expiration, which causes air-trapping and hyperinflation of the lungs and thorax, increased work of breathing, and alteration of respiratory muscle function. This systematic review was conducted according to the Preferred Reporting Items for systematic review and metanalysis (PRISMA) statement. Search engines like PubMed through HINARI, Cochrane database and Google Scholars were used to find evidences. Low-dose IV ketamine, midazolam, IV lidocaine or combined with salbutamol are recommended to be used as premedication before induction. Propofol, ketamine, halothane, isoflurane and sevoflurane are best induction agents and maintenance for asthmatic surgical patients respectively. Among the muscle relaxants, vecuronium is safe for use in asthmatics. In addition, Succinylcholine and pancronium which releases low levels of histamine has been used safely in asthmatics with little morbidity.

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Asthma is one of the commonest respiratory illnesses among patients undergoing surgery.

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This systematic review was conducted according to PRISMA protocol.

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Propofol, ketamine, halothane, isoflurane and sevoflurane are best pharmacologic agents for asthmatic surgical patients.

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Vecuronium is safe for use in asthmatic surgical patients.

The Impact of Sevoflurane and Propofol Anesthetic Induction on Bag Mask Ventilation in Surgical Patients with High Body Mass Index

Background and Aims:

Obesity is associated with restrictive ventilatory pattern which causes rapid oxygen desaturation. Although obesity is considered as a risk factor for difficult airway management, failure to achieve effective bag mask ventilation (BMV) can be catastrophic. This study tried to assess the effect of both propofol and sevoflurane on the efficacy of BMV during anesthetic induction in obese patients.

Patients and Methods:

A total of 200 cases were included, and they were randomly divided into two equal groups; Group S which included 100 cases who underwent sevoflurane induction, and Group P which included the remaining 100 cases who underwent propofol induction.

Results:

No statistically significant difference was detected between the two groups regarding patient and air way characteristics (P > 0.05). Difficult BMV (DBMV) was encountered in 19% and 37% of cases in Groups S and P, respectively. The incidence of DBMV was significantly increased in the P group (P = 0.005). Furthermore, the severity of difficulty was more marked in the P group. Logistic regression analysis revealed that thyromental distance, presence of macroglossia, presence of beard, lack of teeth, history of snoring, as well as propofol induction were risk factors for DBMV.

Conclusion:

Sevoflurane can facilitate BMV and provide better intubation conditions in comparison to propofol during anesthetic induction in morbidly obese patients. Moreover, decreased thyromental distance, presence of macroglossia and beard, lack of teeth, and history of snoring are considered preoperative indicators of DBMV.

Volatile anaesthetic for treatment of respiratory failure from status asthmaticus requiring extracorporeal membrane oxygenation

A 37-year-old male smoker with asthma presented with status asthmaticus refractory to terbutaline, intravenous magnesium, continuous bronchodilators, steroids, heliox and theophylline infusion. He was intubated on hospital day 2 and cannulated for veno-venous extracorporeal membrane oxygenation (V-V ECMO) on hospital day 3 for refractory respiratory acidosis secondary to hypercapnia and hypoxemia despite maximum medical management over 4 days. He was started on inhaled isoflurane with improvement in peak airway pressures and respiratory acidosis, allowing for prompt weaning from V-V ECMO and extubation. Inhaled volatile anaesthetics exert a direct action on bronchiole smooth muscle causing relaxation with significant effect despite severely impaired pulmonary function. This treatment in patients on ECMO may allow for earlier decannulation and decreased risk of coagulopathy, ECMO circuit failure, infection, renal failure, pulmonary haemorrhage and central nervous system haemorrhage. However, major limitations exist in delivering volatile anaesthetics, which may make use inefficient and costly despite efficacy.

Laryngeal Mask Airway Versus Other Airway Devices for Anesthesia in Children With an Upper Respiratory Tract Infection: A Systematic Review and Meta-analysis of Respiratory Complications

There is an association between upper respiratory tract infection (URTI) and an increased incidence of perioperative respiratory adverse events (PRAEs), which is a major risk for morbidity during pediatric anesthesia. The aim of the present study was to compare the risk of PRAEs among different airway devices during anesthesia in children with a URTI. A systematic review according to the Cochrane Handbook and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted. Only randomized clinical trials evaluating anesthesia in children with a URTI and who were submitted to any of the airway devices were included. From 1030 studies identified, 5 randomized clinical trials were included in the final analysis. There were no statistical differences between laryngeal mask airway (LMA®) and endotracheal tube (ETT) regarding breath holding or apnea (risk ratio [RR], 0.82; 95% confidence interval [CI], 0.41-1.65), laryngospasm (RR, 0.74; 95% CI, 0.18-2.95), and arterial oxygen desaturation (RR, 0.44; 95% CI, 0.16-1.17). The quality of evidence was low for the first outcome and very low for the 2 other outcomes, respectively. The LMA use produced a significant reduction of cough (RR, 0.75; 95% CI, 0.58-0.96, low quality of evidence) compared with ETT. The ideal airway management in children with a URTI remains obscure given that there are few data of perioperative respiratory complications during anesthesia. This systematic review demonstrates that LMA use during anesthesia in children with URTI did not result in decrease of the most feared PRAEs. However, LMA was better than ETT in reducing cough. Further research is needed to define the risks more clearly because cough and laryngospasm have similar triggers, and both bronchospasm and laryngospasm trigger cough.

The Effect of Sevoflurane and Dexmedetomidine on Pulmonary Mechanics in ICU Patients

Objective

In intensive care unit (ICU) patients, intravenous (iv) and volatile agents are used for sedation. The aim of the present study was to investigate the effects of dexmedetomidine and sevoflurane on pulmonary mechanics in ICU patients with pulmonary disorders.

Methods

After approval of the ethical committee and informed consent between the ages of 18-65 years were obtained, 30 patients with an American Society of Anesthesiologist status I-III, who were mechanically ventilated, who had pulmonary disorders and who needed sedation were included in the study. Exclusion criteria were severe hepatic, pulmonary and renal failures; pregnancy; convulsion and/or seizure history; haemodynamic instability and no indication for sedation. Patients were divided into two groups by randomised numbers generated by a computer. For sedation, 0.5%^-1% sevoflurane (4-10 mL h^-1) was used by an Anaesthetic Conserving Device in Group S (n=15), and iv dexmedetomidine infusion (1 μg^-1 kg^-1 10 min^-1 loading and 0.2-0.7 μg^-1 kg^-1 h^-1 maintenance) was performed in Group D (n=15). Arterial blood gas analysis, airway resistance, positive end-expiratory pressure (PEEP), frequency, tidal volume (TV), peak airway pressure (Ppeak), static pulmonary compliance and end-tidal CO₂ values were recorded at baseline, 1, 3, 6, 9, 12 and 24 h.

Results

Demographic data, airway resistance, PEEP, frequency, TV, Ppeak and static pulmonary compliance values were similar between the groups. PaCO₂ and end-tidal CO₂ values were higher in Group S than in Group D. Sedation and patient comfort scores were similar between the two groups.

Conclusion

Both sevoflurane and dexmedetomidine are suitable sedative agents in ICU patients with pulmonary diseases.

The effect of tulobuterol patches on the respiratory system after endotracheal intubation

Background

Endotracheal intubation during anesthesia induction may increase airway resistance (R_aw) and decrease dynamic lung compliance (C_dyn). We hypothesized that prophylactic treatment with a transdermal β2-agonist tulobuterol patch (TP) would help to reduce the risk of bronchospasm after placement of the endotracheal tube.

Methods

Eighty-two American Society of Anesthesiologists (ASA) category I or II adult patients showing obstructive patterns were divided randomly into a control and a TP group (n = 41 each). The night before surgery, a 2-mg TP was applied to patients in the TP group. Standard monitors were recorded, and target controlled infusion (TCI) with propofol and remifentanil was used for anesthesia induction and maintenance. Simultaneously, end-tidal carbon dioxide, R_aw, and C_dyn were determined at 5, 10, and 15 min intervals after endotracheal intubation.

Results

There was no significant difference in demographic data between the two groups. The TP group was associated with a lower R_aw and a higher C_dyn, as compared to the control group. R_aw was significantly lower at 10 min (P < 0.05) and 15 min (P < 0.01), and C_dyn was significantly higher at 5 min (P < 0.05) and 15 min (P < 0.01) in the TP group. A trend towards a lower R_aw was observed showing a statistically significant difference 5 min after endotracheal intubation (P < 0.01) in each group.

Conclusions

Prophylactic treatment with TP showed a bronchodilatory effect through suppressing an increase in R_aw and a decrease in C_dyn after anesthesia induction without severe adverse effects.

Sevoflurane Relieves Lung Function Deterioration After Cardiopulmonary Bypass

OBJECTIVE

To investigate sevoflurane's potential to alleviate the detrimental pulmonary changes after cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized clinical investigation.

SETTING

University hospital.

PARTICIPANTS

One hundred ninety patients undergoing elective cardiac surgery.

INTERVENTIONS

Ninety-nine patients under intravenous anesthesia were administered 1 minimal alveolar concentration of sevoflurane for 5 minutes after being weaned from CPB (group SEV); intravenous anesthesia was maintained in the other 91 patients (group CTRL).

MEASUREMENTS AND MAIN RESULTS

Measurements were performed with open chest: before CPB, after CPB, and after intervention. The lungs' mechanical impedance and capnogram traces were recorded, arterial and central venous blood samples were analyzed, and lung compliance was documented. Airway resistance, tissue damping, and elastance were obtained from the impedance spectra. The capnogram phase III slope was determined using linear regression. The partial pressure of oxygen in the arterial blood/fraction of inspired oxygen ratio and shunt fraction were calculated from blood gas parameters. After CPB, sevoflurane induced bronchodilation, reflected in marked drops in airway resistance and smaller improvements in lung tissue viscoelasticity indicated by decreases in tissue damping and elastance. These changes were reflected in a decreased capnogram phase III slope and shunt fraction and increased partial pressure of oxygen in the arterial blood/fraction of inspired oxygen ratio and lung compliance. The more severe deteriorations that occurred after CPB, the greater improvements by sevoflurane were observed.

CONCLUSIONS

Sevoflurane can alleviate CPB-induced bronchoconstriction, compromised lung tissue mechanics, and enhanced intrapulmonary shunt. This benefit has particular importance in patients with severe CPB-induced lung function deterioration.

Relationship between pre-anesthetic and intra-anesthetic airway resistance in patients undergoing general anesthesia: A prospective observational study

Surgery patients in Japan undergo routine spirometry testing prior to general anesthesia. The use of a flow sensor during general anesthesia has recently become common. However, it is not certain whether the information derived from flow-volume curves is being adequately used for mechanical ventilation management during general anesthesia. So far, there have been no attempts to calculate airway resistance using flow-volume curves. Therefore, we performed a prospective, observational study to investigate the relationship between pre-anesthetic and intra-anesthetic airway resistance in patients scheduled for surgery under general anesthesia. We calculated pre-anesthetic and intra-anesthetic airway resistance in each patient, based on the slopes of flow-volume curves obtained prior to and during general anesthesia. We also calculated endotracheal tube resistance to correct the intra-anesthetic airway resistance values calculated. A total of 526 patients were included in the study, and 98 patients had a forced expiratory volume in the first second/forced vital capacity ratio of < 70%. Pre-anesthetic airway resistance was significantly higher in patients with airflow obstruction than in those without airflow obstruction (p < 0.001), whereas no significant difference in intra-anesthetic airway resistance was found between patients with and without airflow obstruction during mechanical ventilation (p = 0.48). Pre-anesthetic and intra-anesthetic airway resistance values were closer to each other in patients without airflow obstruction, with a mean difference < 1.0 cmH2O L-1s-1, than in those with airflow obstruction, although these respiratory parameters were significantly different (p < 0.001). Intra-anesthetic airway resistance was not related to the FEV1/FVC ratio, regardless of the degree to which the FEV1/FVC ratio reflected pre-anesthetic airway resistance. As compared with patients with airflow obstruction, the mean difference between pre-anesthetic and intra-anesthetic airway resistance was small in patients without airflow obstruction.

Contemporary treatment of children with critical and near-fatal asthma

Asthma is the most common chronic illness in childhood. Although the vast majority of children with acute asthma exacerbations do not require critical care, some fail to respond to standard treatment and require escalation of support. Children with critical or near-fatal asthma require close monitoring for deterioration and may require aggressive treatment strategies. This review examines the available evidence supporting therapies for critical and near-fatal asthma and summarizes the contemporary clinical care of these children. Typical treatment includes parenteral corticosteroids and inhaled or intravenous beta-agonist drugs. For children with an inadequate response to standard therapy, inhaled ipratropium bromide, intravenous magnesium sulfate, methylxanthines, helium-oxygen mixtures, and non-invasive mechanical support can be used. Patients with progressive respiratory failure benefit from mechanical ventilation with a strategy that employs large tidal volumes and low ventilator rates to minimize dynamic hyperinflation, barotrauma, and hypotension. Sedatives, analgesics and a neuromuscular blocker are often necessary in the early phase of treatment to facilitate a state of controlled hypoventilation and permissive hypercapnia. Patients who fail to improve with mechanical ventilation may be considered for less common approaches, such as inhaled anesthetics, bronchoscopy, and extracorporeal life support. This contemporary approach has resulted in extremely low mortality rates, even in children requiring mechanical support.

Anaesthesia for children with bronchial asthma and respiratory infections

Asthma represents one of the most common chronic diseases in children with an increasing incidence reported worldwide. The key to successful anaesthetic outcome involves thorough pre-operative assessment and optimisation of the child's pulmonary status. Judicious application of proper anti-inflammatory and bronchodilatory regimes should be instituted as part of pre-operative preparation. Bronchospasm triggering agents should be carefully probed and meticulously avoided. A calm and properly sedated child at the time of induction is ideal, so also is extubation in a deep plane with an unobstructed airway. Wherever possible, regional anaesthesia should be employed. This will avoid airway manipulations, with additional benefit of excellent peri-operative analgesia. Agents with a potential for histamine release and techniques that can increase airway resistance should be diligently avoided. Emphasis must be given to proper post-operative care including respiratory monitoring, analgesia and breathing exercises.

Sevoflurane administration initiated out of the ED for life-threatening status asthmaticus

Status asthmaticus is both a common and dangerous cause of acute dyspnea in the emergency department (ED) setting. Although most cases respond favorably to standard treatment, there are rare cases in which therapy beyond traditional treatment is needed. One of these treatment modalities includes inhalational anesthesia. We present a case in which inhaled sevoflurane was initiated out of the ED for a life-threatening asthma exacerbation refractory to conventional treatment. To our knowledge, this is only the second case to report the use of inhaled anesthetics initiated out of the ED for status asthmaticus and is the first report of its kind to thoroughly detail the respiratory response noted while inhalation anesthesia was being implemented. A brief review of other case reports involving the use of sevoflurane for asthma is included. This case, as well as the others reviewed, illustrates the significant beneficial effect inhaled anesthetics can have on asthma, making this a treatment modality that must be recognized and appreciated by all emergency medicine providers.

Anesthesia and ventilation strategies in children with asthma: part II - intraoperative management

PURPOSE OF REVIEW

As asthma is a frequent disease especially in children, anesthetists are increasingly providing anesthesia for children requiring elective surgery with well controlled asthma but also for those requiring urgent surgery with poorly controlled or undiagnosed asthma. This second part of this two-part review details the medical and ventilatory management throughout the perioperative period in general but also includes the perioperative management of acute bronchospasm and asthma exacerbations in children with asthma.

RECENT FINDINGS

Multiple observational trials assessing perioperative respiratory adverse events in healthy and asthmatic children provide the basis for identifying risk reduction strategies. Mainly, animal experiments and to a small extent clinical data have advanced our understanding of how anesthetic agents effect bronchial smooth muscle tone and blunt reflex bronchoconstriction. Asthma treatment outside anesthesia is well founded on a large body of evidence.Perioperative prevention strategies have increasingly been studied. However, evidence on the perioperative management, including mechanical ventilation strategies of asthmatic children, is still only fair, and further research is required.

SUMMARY

To minimize the considerable risk of perioperative respiratory adverse events in asthmatic children, perioperative management should be based on two main pillars: the preoperative optimization of asthma treatment (please refer to the first part of this two-part review) and - the focus of this second part of this review - the optimization of anesthesia management in order to optimize lung function and minimize bronchial hyperreactivity in the perioperative period.

Impact of the anesthetic conserving device on respiratory parameters and work of breathing in critically ill patients under light sedation with sevoflurane

BACKGROUND

Sevoflurane sedation in the intensive care unit is possible with a special heat and moisture exchanger called the Anesthetic Conserving Device (ACD) (AnaConDa; Sedana Medical AB, Uppsala, Sweden). The ACD, however, may corrupt ventilatory mechanics when used during the weaning process of intensive care unit patients. The authors compared the ventilatory effects of light-sedation with sevoflurane administered with the ACD and those of classic management, consisting of a heated humidifier and intravenous sedation, in intensive care unit patients receiving pressure-support ventilation.

METHODS

Fifteen intensive care unit patients without chronic pulmonary disease were included. A target Richmond Agitation Sedation Scale level of -1/-2 was obtained with intravenous remifentanil (baseline 1-condition). Two successive interventions were tested: replacement of the heated humidifier by the ACD without sedation change (ACD-condition) and sevoflurane with the ACD with an identical target level (ACD-sevoflurane-condition). Patients finally returned to baseline (baseline 2-condition). Work of breathing, ventilatory patterns, blood gases, and tolerance were recorded. A steady state of 30 min was achieved for each experimental condition.

RESULTS

ACD alone worsened ventilatory parameters, with significant increases in work of breathing (from 1.7 ± 1.1 to 2.3 ± 1.2 J/l), minute ventilation, P0,1, intrinsic positive end-expiratory pressure (from 1.3 ± 2.6 to 4.7 ± 4.2 cm H2O), inspiratory pressure swings, and decreased patient comfort. Sevoflurane normalized work of breathing (from 2.3 ± 1.2 to 1.8 ± 1 J/l), intrinsic positive end-expiratory pressure (from 4.7 ± 4.2 to 1.8 ± 2 cm H2O), inspiratory pressure swings, other ventilatory parameters, and patient tolerance.

CONCLUSIONS

ACD increases work of breathing and worsens ventilatory parameters. Sevoflurane use via the ACD (for a light-sedation target) normalizes respiratory parameters. In this patient's population, light-sedation with sevoflurane and the ACD may be possible during the weaning process.

Effects of inhalational anaesthetics in experimental allergic asthma

We evaluated whether isoflurane, halothane and sevoflurane attenuate the inflammatory response and improve lung morphofunction in experimental asthma. Fifty-six BALB/c mice were sensitised and challenged with ovalbumin and anaesthetised with isoflurane, halothane, sevoflurane or pentobarbital sodium for one hour. Lung mechanics and histology were evaluated. Gene expression of pro-inflammatory (tumour necrosis factor-α), pro-fibrogenic (transforming growth factor-β) and pro-angiogenic (vascular endothelial growth factor) mediators, as well as oxidative process modulators, were analysed. These modulators included nuclear factor erythroid-2 related factor 2, sirtuin, catalase and glutathione peroxidase. Isoflurane, halothane and sevoflurane reduced airway resistance, static lung elastance and atelectasis when compared with pentobarbital sodium. Sevoflurane minimised bronchoconstriction and cell infiltration, and decreased tumour necrosis factor-α, transforming growth factor-β, vascular endothelial growth factor, sirtuin, catalase and glutathione peroxidase, while increasing nuclear factor erythroid-2-related factor 2 expression. Sevoflurane down-regulated inflammatory, fibrogenic and angiogenic mediators, and modulated oxidant-antioxidant imbalance, improving lung function in this model of asthma.

Sevoflurane therapy for life-threatening asthma in children

BACKGROUND

Asthma is a common disease in children and often develops early in life. This multicentre retrospective case series describe the use and effectiveness of sevoflurane inhalation therapy in a series of children with severe asthma in the paediatric intensive care unit (PICU).

METHODS

Seven children ranging from 4 to 13 yr of age admitted to the PICU of two tertiary care hospitals in the Netherlands were included. They all were admitted with the diagnosis of severe asthma requiring invasive mechanical ventilation and were treated with sevoflurane inhalation therapy.

RESULTS

The median (range) Pco2 level at the start, after 2 h, and at the end of sevoflurane treatment were 14 (5.1-24.8), 9.8 (5.4-17.0), and 6.2 (4.5-11.4) kPa (P=0.05) while the median (range) pH was 7.02 (6.97-7.36), 7.18 (7.04-7.35), and 7.43 (7.15-7.47) kPa (P=0.01), respectively. The median (range) peak pressure values declined from 30 (23-56) to 20.4 (14-33) cm H2O (P=0.03). No severe adverse effects besides hypotension, with sufficient response to norepinephrine treatment, were seen.

CONCLUSIONS

Sevoflurane inhalation corrects high levels of Pco2 and provides clinical improvement in mechanically ventilated children with life-threatening asthma who fail to respond to conventional treatment.

Volatile anesthetic rescue therapy in children with acute asthma: innovative but costly or just costly?

OBJECTIVES

To describe volatile anesthesia (VA) use for pediatric asthma, including complications and outcomes.

DESIGN

Retrospective cohort study.

SETTING

Children's hospitals contributing to the Pediatric Health Information System between 2004-2008.

PATIENTS

Children 2-18 years old with a primary diagnosis code for asthma supported with mechanical ventilation.

INTERVENTION

Those treated with VA were compared to those not treated with VA or extracorporeal membrane oxygenation. Hospital VA use was grouped as none, <5%, 5-10% and >10% among intubated children.

MEASUREMENTS AND MAIN RESULTS

One thousand five hundred and fifty-eight patients received mechanical ventilation at 40 hospitals for asthma: 47 (3%) received VA treatment at 11 (28%) hospitals. Those receiving a VA were significantly less likely to receive inhaled b-agonists, ipratropium bromide, and heliox, but more likely to receive neuromuscular blocking agents than patients treated without VA. Length of mechanical ventilation, hospital stay (length of stay [LOS]) and charges were significantly greater for those treated with VA. Aspiration was more common but death and air leak did not differ. Patients at hospitals with VA use >10% were significantly less likely to receive inhaled b agonist, ipratropium bromide, methylxanthines, and heliox, but more likely to receive systemic b agonist, neuromuscular blocking agents compared to those treated at hospitals not using VA. LOS, duration of ventilation, and hospital charges were significantly greater for patients treated at centers with high VA use.

CONCLUSIONS

Mortality does not differ between centers that use VA or not. Patients treated at centers with high VA use had significantly increased hospital charges and increased LOS.

Anaesthetic management of the child with co-existing pulmonary disease

Children with co-existing pulmonary disease have a wide range of clinical manifestations with significant implications for anaesthetists. Although there are a number of pulmonary diseases in children, this review focuses on two of the most common pulmonary disorders, asthma and bronchopulmonary dysplasia (BPD). These diseases share the physiology of bronchoconstriction and variably decreased flow in the airways, but also have unique physiological consequences. The anaesthetist can make a difference in outcomes with proper preoperative evaluation and appropriate preparation for surgery in the context of a team approach to perioperative care with implementation of a stepwise approach to disease management. An understanding of the importance of minimizing the risk for bronchoconstriction and having the tools at hand to treat it when necessary is paramount in the care of these patients. Unique challenges exist in the management of pulmonary hypertension in BPD patients. This review covers medical treatment, intraoperative management, and postoperative care for both patient populations.

Inhaled and intravenous treatment in acute severe and life-threatening asthma

Management of life-threatening acute severe asthma in children and adults may require anaesthetic and intensive care. The inhaled route for drug delivery is not appropriate when only small respiratory gas volumes are shifted; the i.v. route may be associated with greater side-effects. Magnesium sulphate i.v. has a place in acute asthma management because it is a mild bronchodilator, and has a stabilizing effect on the atria which may attenuate tachycardia occurring after inhaled and i.v. salbutamol. If intubation and ventilation are required, a reduction in bronchoconstriction by any means before and during these procedures should reduce morbidity. This narrative review aims to show strengths and weakness of the evidence, present controversies, and forward opinions of the author. The review contains a practical guide to the setting up, use and efficiency of nebulizers, metered dose inhalers, and spacers (chambers). It also presents a commonsense approach to the management of severe asthmatics in whom delay in bronchodilatation would cause clinical deterioration. When self-inhaled agents have had no effect, i.v. drugs may help avoid intubation and ventilation. The review includes suggestions for the use of inhaled anaesthetics, anaesthetic induction, and brief notes on subsequent ventilation of the lungs.

Comparison of respiratory mechanics in adult patients undergoing minimally invasive repair of the pectus excavatum and removal of a pectus bar

OBJECTIVE

The objective of this study was to compare the respiratory mechanics and gas exchange in adult patients undergoing minimally invasive repair of the pectus excavatum (MIRPE group) and removal of a pectus bar (bar removal group).

DESIGN

A prospective observational study.

SETTING

A tertiary university hospital.

PARTICIPANTS

Thirty-two patients scheduled for elective MIRPE or removal of a pectus bar.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Spirometry was used to measure the peak inspiratory airway pressure (PIP), static compliance, and respiratory resistance. The measurements were recorded at 1 minute after beginning mechanical ventilation (T0), 15 minutes after beginning sevoflurane inhalation (T1), and after the insertion (or removal) of a pectus bar through the chest wall (T2). Pulmonary gas exchange was assessed by calculating the alveolar arterial oxygen tension difference (AaDO2) before surgical incision and after insertion (or removal) of the pectus bar. In the MIRPE group, static compliance was decreased significantly (p < 0.001), and PIP was increased significantly (p < 0.001) after insertion of the pectus bar (T2) compared with baseline. In contrast, the bar removal group showed the opposite results. There were significant differences in static compliance and PIP at T2 between the groups (p = 0.002 and 0.026, respectively). AaDO2 was increased significantly in the MIRPE group compared with the bar removal group (p = 0.012).

CONCLUSIONS

Insertion of the pectus bar through the chest wall results in significant changes in respiratory mechanics and gas exchange. Therefore, close attention to pulmonary function is required during and after these surgical procedures.

High-resolution computed tomography bronchial lumen to pulmonary artery diameter ratio in anesthetized ventilated cats with normal lungs

High-resolution computed tomography (CT) is the preferred noninvasive tool for diagnosing bronchiectasis in people. A criterion for evaluating dilation of the bronchus is the bronchial lumen to pulmonary artery diameter (bronchoarterial ratio [BA ratio]). A ratio of > 1.0 in humans or > 2.0 in dogs has been suggested as a threshold for identifying bronchiectasis. The purpose of this study was to establish the BA ratio in normal cats. Fourteen specific pathogen-free cats were selected for analysis of thoracic CT images. The BA ratios of the lobar bronchi of the left cranial (cranial and caudal parts), right cranial, right middle, left caudal, and right caudal lung lobes were measured. The mean of the mean BA ratio of all lung lobes was 0.71 +/- 0.05. Individual BA ratios ranged from 0.5 to 1.11. Comparing individual lobes for each cat, there was no significant difference (P = 0.145) in mean BA ratio between lung lobes. A mean BA ratio for these normal cats was 0.71 +/- 0.1, which suggests an upper cut-off normal value > 0.91 (mean +/- 2 standard deviations) between normal and abnormal cats.

Kartagener's syndrome--anaesthetic considerations for ENT surgery

Kartagener's syndrome is a rare autosomal recessive disorder presenting a triad of sinusitis, bronchicetasis and situs inversus with dextrocardia. It occurs in 50% of patients with situs inversus. The most important anesthetic implications of Kartegener's syndrome surgery are assessement of pulmonary and cardiac structure and function. We present a case of 43-year-old woman with chronic rhinosinusitis with polyps and bilateral sectetory otitis media. The chest radiograph and CT scans showed dextrocardia and situs inversus with chronic bronchitis without bronchiectasis. Spirometry showed forced expiratory volume in one second (FEV1) of 2.66 L and forced vital capacity (FVC) of 3.62 L. Electroechography showed no cardiac abnormalities with 55-60% of EF. The anesthetic implications of Kartagener's syndrome are varied. The regional or general anesthesia might be involved with sinus surgery, ear surgery, pulmonary surgery, infertility or abdominal and cardiac surgery. The main anesthetic considerations among patients with Kartagener's syndrome are related to the pulmonary function which include preoperative respiratory infections due to bronchiectasis. We should also monitor potentially occluded congenital heart diseases. Kartagener's syndrome is a rare disease and when the patient need an operation we have to consider surgery with regional or general anesthesia. The general anesthesia would be safe after complete preanaesthetic examination of the patient. The ECG, chest CT scans, spirometry and echocardiography are mandatory before the operation.

Isoflurane for life-threatening bronchospasm: a 15-year single-center experience

BACKGROUND

Children with severe bronchospasm requiring mechanical ventilation may become refractory to conventional therapy. In these critically ill patients, isoflurane is an inhaled anesthetic agent available in some centers to treat bronchospasm. We hypothesized that isoflurane is safe and would lead to improved gas exchange in children with life-threatening bronchospasm refractory to conventional therapy.

METHODS

A retrospective review was conducted and included mechanically ventilated children treated with isoflurane in a quaternary pediatric ICU for life-threatening bronchospasm, from 1993 to 2007. Demographic, blood gas, ventilator, and outcome data were collected.

RESULTS

Thirty-one patients, with a mean age of 9.5 years (range 0.4-23 years) were treated with isoflurane, from 1993 to 2007. Mean time to initiation of isoflurane after intubation was 13 hours (0-120 h), and the mean maximum isoflurane dose was 1.1% (0.3-2.5%). Mean duration of isoflurane administration was 54.5 hours (range 1-181 h), with a total mean duration of mechanical ventilation of 252 hours (range 16-1,444 h). Isoflurane led to significant improvement in pH and P(CO(2)) within 4 hours of initiation (P ≤ .001). Complications during isoflurane administration included hypotension requiring vasoactive infusions in 24 (77%), arrhythmia in 3 (10%), neurologic side effects in 3 (10%), and pneumothorax in 1 (3%) patient.

CONCLUSIONS

Isoflurane led to improvement in pH and P(CO(2)) within 4 hours in this series of mechanically ventilated patients with life-threatening bronchospasm. The majority of patients in this series developed hypotension, but there was a low incidence of other side effects related to isoflurane administration. Isoflurane appears to be an effective therapy in patients with life-threatening bronchospasm refractory to conventional therapy. However, further investigation is warranted, given the uncertain overall impact of isoflurane in this context.

Long-term isoflurane therapy for refractory bronchospasm associated with herpes simplex pneumonia in a heart transplant patient

A 47-year-old man with a history of heart transplant was admitted after severe traumatic brain injury and seizures. During mechanical ventilation, the patient developed bronchospasm that severely compromised respiratory function that led to cardiac arrest. After resuscitation, application of isoflurane through the Anaesthetic Conserving Device (AnaConDa) in the ICU successfully treated bronchospasm, provided adequate sedation, and enabled appropriate ventilation and diagnostic bronchoscopy. A subsequent bronchoalveolar lavage revealed a high amount of Herpes simplex DNA. Herpes simplex pneumonia was diagnosed and treated with acyclovir. Isoflurane treatment was applied for twelve days total without side effects on renal and cerebral function. The patient recovered quickly after the termination of sedation. At discharge, he was fully awake without focal neurological deficiency and his long-term outcome was excellent. This case demonstrates that isoflurane is a treatment option in life-threatening cases of bronchospasm and a safe option for long-term sedation.

Lung function after total intravenous anaesthesia or balanced anaesthesia with sevoflurane

BACKGROUND

We investigated the effects of total i.v. anaesthesia (TIVA) and balanced anaesthesia (BAL) with sevoflurane on postoperative lung function in patients undergoing surgery in the prone position.

METHODS

Sixty patients, aged 21-60 yr, undergoing elective lumbar disc surgery in the prone position were randomly allocated to undergo TIVA (propofol-remifentanil) or BAL (fentanyl-nitrous oxide-sevoflurane). Forced vital capacity (FVC), forced expiratory volume in 1 s, mid-expiratory flow (MEF 25-75), and peak expiratory flow were measured before and after general anaesthesia.

RESULTS

Both groups were similar with respect to patient characteristic data and preoperative lung function parameters. Irrespective of the type of anaesthesia administered, lung function parameters decreased after operation, with the decrease in FVC being greater after TIVA than after BAL with sevoflurane.

CONCLUSIONS

In patients emerging from general anaesthesia, postoperative reduction in FVC is greater after TIVA than after BAL with sevoflurane.

Risk assessment for respiratory complications in paediatric anaesthesia: a prospective cohort study

BACKGROUND

Perioperative respiratory adverse events in children are one of the major causes of morbidity and mortality during paediatric anaesthesia. We aimed to identify associations between family history, anaesthesia management, and occurrence of perioperative respiratory adverse events.

METHODS

We prospectively included all children who had general anaesthesia for surgical or medical interventions, elective or urgent procedures at Princess Margaret Hospital for Children, Perth, Australia, from Feb 1, 2007, to Jan 31, 2008. On the day of surgery, anaesthetists in charge of paediatric patients completed an adapted version of the International Study Group for Asthma and Allergies in Childhood questionnaire. We collected data on family medical history of asthma, atopy, allergy, upper respiratory tract infection, and passive smoking. Anaesthesia management and all perioperative respiratory adverse events were recorded.

FINDINGS

9297 questionnaires were available for analysis. A positive respiratory history (nocturnal dry cough, wheezing during exercise, wheezing more than three times in the past 12 months, or a history of present or past eczema) was associated with an increased risk for bronchospasm (relative risk [RR] 8.46, 95% CI 6.18-11.59; p<0.0001), laryngospasm (4.13, 3.37-5.08; p<0.0001), and perioperative cough, desaturation, or airway obstruction (3.05, 2.76-3.37; p<0.0001). Upper respiratory tract infection was associated with an increased risk for perioperative respiratory adverse events only when symptoms were present (RR 2.05, 95% CI 1.82-2.31; p<0.0001) or less than 2 weeks before the procedure (2.34, 2.07-2.66; p<0.0001), whereas symptoms of upper respiratory tract infection 2-4 weeks before the procedure significantly lowered the incidence of perioperative respiratory adverse events (0.66, 0.53-0.81; p<0.0001). A history of at least two family members having asthma, atopy, or smoking increased the risk for perioperative respiratory adverse events (all p<0.0001). Risk was lower with intravenous induction compared with inhalational induction (all p<0.0001), inhalational compared with intravenous maintenance of anaesthesia (all p<0.0001), airway management by a specialist paediatric anaesthetist compared with a registrar (all p<0.0001), and use of face mask compared with tracheal intubation (all p<0.0001).

INTERPRETATION

Children at high risk for perioperative respiratory adverse events could be systematically identified at the preanaesthetic assessment and thus can benefit from a specifically targeted anaesthesia management.

FUNDING

Department of Anaesthesia, Princess Margaret Hospital for Children, Swiss Foundation for Grants in Biology and Medicine, and the Voluntary Academic Society Basel.

Effects of sevoflurane and desflurane on respiratory mechanics after tracheal intubation in children

BACKGROUND

Tracheal intubation causes a reflex tracheal constriction that leads to increased airway resistance. Inhalation anesthetics can prevent or minimize this response. Therefore, this study was conducted to evaluate the effect of 1 MAC sevoflurane or desflurane on respiratory mechanics in children after anesthetic induction using propofol and tracheal intubation.

METHODS

Sixty children undergoing elective surgery with tracheal intubation were assigned into two groups at random, a 1 MAC concentration of sevoflurane (n = 30) and a desflurane (n = 30) group. Anesthesia was induced using propofol (1.5 mg/kg) and tracheal intubation was facilitated using rocuronium (0.6 mg/kg). A respiratory profile monitor was used to measure the respiratory resistance, dynamic compliance and peak inspiratory airway pressure. The measurements were made at three time points, after three inspirations from the beginning of mechanical ventilation (baseline) and at 5 and 10 min after the administration of inhalation anesthetics.

RESULTS

Sevoflurane and desflurane led to a significant decrease in respiratory resistance and increased dynamic compliance at 5 and 10 min when compared to baseline. There were no significant differences in respiratory resistance and dynamic compliance between the two groups.

CONCLUSIONS

A 1 MAC concentration of sevoflurane and desflurane has a similar bronchodilatory effect after tracheal intubation in children.

Endogenous gamma-aminobutyric acid modulates tonic guinea pig airway tone and propofol-induced airway smooth muscle relaxation

BACKGROUND

Emerging evidence indicates that an endogenous autocrine/paracrine system involving gamma-aminobutyric acid (GABA) is present in airways. GABAA channels, GABAB receptors, and the enzyme that synthesizes GABA have been identified in airway epithelium and smooth muscle. However, the endogenous ligand itself, GABA, has not been measured in airway tissues. The authors sought to demonstrate that GABA is released in response to contractile agonists and tonically contributes a prorelaxant component to contracted airway smooth muscle.

METHODS

The amount and cellular localization of GABA in upper guinea pig airways under resting and contracted tone was determined by high pressure liquid chromatography and immunohistochemistry, respectively. The contribution that endogenous GABA imparts on the maintenance of airway smooth muscle acetylcholine-induced contraction was assessed in intact guinea pig airway tracheal rings using selective GABAA antagonism (gabazine) under resting or acetylcholine-contracted conditions. The ability of an allosteric agent (propofol) to relax a substance P-induced relaxation in an endogenous GABA-dependent manner was assessed.

RESULTS

GABA levels increased and localized to airway smooth muscle after contractile stimuli in guinea pig upper airways. Acetylcholine-contracted guinea pig tracheal rings exhibited an increase in contracted force upon addition of the GABAA antagonist gabazine that was subsequently reversed by the addition of the GABAA agonist muscimol. Propofol dose-dependently relaxed a substance P contraction that was blocked by gabazine.

CONCLUSION

These studies demonstrate that GABA is endogenously present and increases after contractile stimuli in guinea pig upper airways and that endogenous GABA contributes a tonic prorelaxant component in the maintenance of airway smooth muscle tone.

Cholecystectomy of a patient with Churg-Strauss syndrome: A case report

Churg-Strauss syndrome is an allergic granulomatous angitis and the organ most commonly involved in this condition is the lung. However, this syndrome also affects the skin, cardiovascular system, kidney, peripheral nervous system and gastrointestinal system. Cardiac involvement is a rare complication but can lead to rapid-onset heart failure as the result of specific cardiomyopathy. Pericardial effusion may also occur. Acalculous cholecystitis is also a rare complication of Churg-Strauss syndrome. Here, we present a case of a patient with Churg-Strauss syndrome and severe heart failure scheduled for cholecystectomy due to acalculous cholecystitis. The patient had mild asthma symptoms, peripheral neuritis in both legs, and severe heart failure. During the preoperative period, steroids, beta2 agonists, diuretics, and antihypertensive drugs were administered. During anesthesia we attempted to prevent compromising the patient's cardiac and pulmonary functions. The surgery was completed successfully, and the patient was discharged without any complications.

Near-fatal asthma: recognition and management

PURPOSE OF REVIEW

Near-fatal asthma continues to be a significant problem despite the decline in overall asthma mortality. The purpose of this review is to discuss recent advances in our understanding of the pathophysiology, diagnosis and treatment of near-fatal asthma.

RECENT FINDINGS

Two distinctive phenotypes of near-fatal asthma have been identified: one with eosinophilic inflammation associated with a gradual onset and a slow response to therapy and a second phenotype with neutrophilic inflammation that has a rapid onset and rapid response to therapy. Patients who develop sudden-onset near-fatal asthma seem to have massive allergen exposure and emotional distress. In stable condition, near-fatal asthma frequently cannot be distinguished from mild asthma. Diminished perception of dyspnea plays a relevant role in treatment delay, near-fatal events, and death in patients with severe asthma. Reduced compliance with anti-inflammatory therapy and ingestion of medications or drugs (heroin, cocaine) have been associated with fatal or near-fatal asthma.

SUMMARY

Near-fatal asthma is a subtype of asthma with unique risk factors and variable presentation that requires early recognition and aggressive intervention.