Endotracheal intubation, but not laryngeal mask airway insertion, produces reversible bronchoconstriction

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.

Anesthetic management of patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the third most common cause of death worldwide. It has a prevalence of 14% among Koreans aged above 40 years and a prevalence of 31% among those aged above 65 years. However, only 6% of the COPD patients receive treatment. Most of the patients do not seek medical attention, as they think that dyspnea, cough, and productive sputum, which are the common symptoms of COPD, are normal aging phenomena. Smoking is a major risk factor for COPD, but environmental hazards and genetic susceptibility are also involved. With aging, lung injuries due to these risk factors accumulate, leading to increased prevalence of COPD. The major concerns regarding perioperative management of COPD patients include preoperative evaluation of cardiopulmonary risks, optimization of lung function, and evaluation of COPD-related physiological functions that are easily aggravated during anesthesia. These include respiratory muscle dysfunction, dynamic hyperinflation and auto-positive end-expiratory pressure, hypoxia-hypercarbia, and pulmonary hypertension-associated heart failure. Therefore, anesthesia for COPD patients should focus on preoperative evaluation, risk reduction measures, and prevention of postoperative pulmonary complications.

Factors affecting airway compliance and resistance in children receiving general anesthesia during adenotonsillectomy

Airway compliance is an important index in the surgery of pediatric patients. This study aimed to explore factors affecting dynamic airway compliance (Cdyn) and airway resistance (Raw) after general anesthesia endotracheal intubation for adenotonsillectomy of pediatric patients.A prospective study was undertaken of 107 children who underwent adenotonsillectomy in Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine between January and June 2018. The values of Cdyn and Raw were recorded at 5, 10, and 15 minute during general anesthesia endotracheal intubation. Univariate analysis and multiple linear regression analysis were performed for factors that affected Cdyn and Raw.Of the 107 patients aged 56.67 ± 18.28 months, 69 (64%) patients were male, and 26 (24%) and 12 (11%) had an upper respiratory infection in the past week and 1 to 2 weeks, respectively. During anesthesia, Cdyn showed a decreasing trend (P < .001) while Raw showed an increasing trend (P < .001). Multivariate analysis revealed that height (β=0.177-0.193) had the strongest correlation with Cdyn; rales during pulmonary auscultation (β= -2.727 to -1.363) and sputum suction (β= -1.670 to -0.949) were also associated with Cdyn (all P < .05). Height was the factor with the strongest negative correlation with Raw (β= -0.382 to -0.305). Rales during pulmonary auscultation (β=10.063-11.326) and sputum suction (β=3.863-9.003) were also associated with Raw (All P < .05).Height, rales during preoperative auscultation and sputum suction were all associated with intraoperative Cydn and Raw for pediatric patients undergoing adenotonsillectomy and should be considered before the surgery.

Anesthetic Considerations for Patients Undergoing Bronchial Thermoplasty

Bronchial thermoplasty (BT) is a novel, Food and Drug Administration-approved nondrug treatment for patients whose asthma remains uncontrolled despite traditional pharmacotherapy. BT involves application of controlled radiofrequency energy to reduce airway smooth muscle in large- and medium-sized airways. Although BT is often performed under general anesthesia, anesthetic management strategies for BT are poorly described. We describe the anesthetic management of 7 patients who underwent 19 BT treatments in a tertiary academic medical center.

Non-intubated thoracoscopic surgery for lung cancer in patients with impaired pulmonary function

Background

Patients with impaired lung function or chronic obstructive pulmonary disease (COPD) are considered high-risk for intubated general anesthesia, which may preclude them from surgical treatment of their lung cancers. We evaluated the feasibility of non-intubated video-assisted thoracoscopic surgery (VATS) for the surgical management of lung cancer in patients with impaired pulmonary function.

Methods

From August 2009 to June 2015, 28 patients with impaired lung function (preoperative forced expiratory volume in 1 second <70% of the predicted value) underwent non-intubated VATS using a combination of thoracic epidural anesthesia or intercostal nerve block, and intra-thoracic vagal block with target-controlled sedation.

Results

Eighteen patients had primary lung cancers, 4 had metastatic lung cancers, and 6 had non-malignant lung tumors. In the patients with primary lung cancer, lobectomy was performed in 4, segmentectomy in 3 and wedge resection in 11, with lymph node sampling adequate for staging. One patient required conversion to intubated one-lung ventilation because of persistent wheezing and labored breathing. Five patients developed air leaks more than 5 days postoperatively while subcutaneous emphysema occurred in 6 patients. Two patients developed acute exacerbations of pre-existing COPD, and new-onset atrial fibrillation after surgery occurred in 1 patient. The median duration of postoperative chest tube drainage was 3 days while the median hospital stay was 6 days.

Conclusions

Non-intubated VATS resection for pulmonary tumors is technically feasible. It may be applied as an alternative to intubated general anesthesia in managing lung cancer in selected patients with impaired pulmonary function.

Sudden intraoperative pulmonary congestion in a patient with severe anemia transfused 3 days prior to surgery

Preoperative blood transfusion is sometimes controversial. We describe a case of a 43-year-old woman who developed sudden pulmonary congestion during surgery despite a small amount of intravenous crystalloid administration. She had no allergic disorders. Preoperative examination revealed that her hemoglobin was 5.6 g/dl, and she was diagnosed as folate-deficiency anemia although she never felt any symptoms before. Therefore, blood transfusion was performed and her hemoglobin increased to 9.4 g/dl. Amid surgery, airway pressure increased suddenly and pulsed oxygen saturation dropped. Chest roentgenogram revealed that the lungs were congested and her heart was markedly enlarged indicating the state of circulatory overload. We suggest that preoperative transfusion in a patient with chronic anemia should be carefully considered, and strongly recommend the confirmation with chest roentgenogram.

Positive Pressure versus Pressure Support Ventilation at Different Levels of PEEP Using the ProSeal™ Laryngeal Mask Airway

We compared positive pressure ventilation with pressure support ventilation at different levels of positive end expiratory pressure (PEEP) using the ProSeal laryngeal mask airway (PLMA). Forty-two anaesthetized adults (ASA 1-2, aged 19 to 63 years) underwent positive pressure ventilation and then pressure support ventilation each with PEEP set at 0, 5 and 10 cmH2O in random order. Pressure support ventilation was with the inspired tidal volume (VTInsp) set at 7 ml/kg and the respiratory rate adjusted to maintain the end-tidal CO2 (ETCO2) at 40 mmHg. Pressure support ventilation was with pressure support set at 5 cmH2O above PEEP and initiated when inspiration produced a 2 cmH2O reduction in airway pressure. Tidal volumes were similar during positive pressure and pressure support ventilation with PEEP, but were higher for the former without PEEP. Respiratory rate and peak inspiratory flow rate were higher during pressure support than positive pressure ventilation (all P<0.001). Peak airway pressure (Ppaw), mean airway pressure (Mpaw), peak expiratory flow rate, and expired airway resistance were lower during pressure support than positive pressure ventilation (all P<0.001). With PEEP set at 10 cmH2O, ETCO2 was lower for pressure support than positive pressure ventilation. During positive pressure ventilation, there was an increase in Ppaw, Mpaw and dynamic compliance (Cdyn) with increasing levels of PEEP (all P<0.01). During pressure support ventilation, there was an increase in inspired and expired tidal volume, Ppaw, peak inspiratory and expiratory flow rates and Cdyn, and a reduction in ETCO2, work of breathing, and expired airway resistance with increasing levels of PEEP (all P<0.01). There were no differences in SpO2, non-invasive mean arterial pressure, heart rate or leak fraction. We conclude that pressure support ventilation provides equally effective gas exchange as positive pressure ventilation during PLMA anaesthesia with or without PEEP at the tested settings. During pressure support, PEEP increases ventilation and reduces work on breathing without increasing leak fraction.

Do Difficult Airway Techniques Predispose Obese Patients to Bronchospasm?

Objective

The existing evidence separately correlates morbid obesity with difficult intubation and bronchospasm. However, there is a lack of data on whether anaesthesia provider manipulations during difficult intubation contribute to an increased ratio of bronchospasm in these patients.

Methods

This is a retrospective analysis of data prospectively taken from 50 morbidly obese patients involved in a previously published study. A possible difficult intubation was preoperatively investigated by recording the following specific physical examination indices: Mallampati and Cormack-Lehane (CL) classifications, cervical spine mobility (CSM), thyromental distance (Td) and patients' ability to open their mouth (mouth opening). Bronchospasm was clinically detected by auscultation and confirmed by measuring peak airway pressures during mechanical ventilation. The Kruskal-Wallis H test was used for data analysis, followed by the Mann-Whitney U test as applicable.

Results

Different physical examination prognostic indices, including Mallampati and CL scales (p<0.001; the CSM excluded -p=0.790), showed that they are related to difficult intubation. Bronchospasm not attributable to difficult intubation was observed in six obese patients.

Conclusion

Patients with morbid obesity constitute an increased relative risk group as far as difficult intubation is concerned, particularly if preoperative findings support a relationship between the two variables examined. In our study, difficult intubation and the concomitant use of special equipment and manipulations did not contribute to an increased rate of bronchospasm in obese patients, but in view of the lack of data, a large number of more sophisticated studies are required to elucidate such an assumption.

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.

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.

[Survey national professional practice on the use of the laryngeal mask]

BACKGROUND

This survey aimed to describe the current use of laryngeal mask (LM) and to define the difference of use according to a group defined like experts.

METHODS

A self-questionnaire available on Internet was sent by e-mail to French anesthesiologists. Results were compared by a Chi(2) test between anesthesiologists according to their expertise defined by a >750 LM use.

RESULTS

Nine hundred and fifty-three anesthesiologists answered to the survey. Only 19 reported never using LM and 37% of responders were defined as expert. More than half of the MAR used the ideal weight to set the size of the MLA to use. Pressure leak was sought by less than one-third of the MAR. In case of leakage, a mobilization of the ML or the patient's head was performed first. In second intention, nearly a quarter of MAR changed technique for the benefit of oral intubation. Only 50% of responders used LM as a rescue technique in case of difficult intubation and ventilation. Experts had less insertion failure and laryngospasm. Complications and medico-legal suites are few.

CONCLUSIONS

Variability of practice may be explained by low-grade recommendations in the literature. LM insertion in case of difficult intubation/ventilation to provide adequate oxygenation and should be formally reminded to clinicians.

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.

Update on perioperative management of the child with asthma

Asthma represents the leading cause of morbidity from a chronic disease among children. Dealing with this disease during the perioperative period of pediatric surgical procedures is, therefore, quite common for the anesthesiologist and other professionalities involved. Preoperative assessment has a key role in detecting children at increased risk of perioperative respiratory complications. For children without an optimal control of symptoms or with a recent respiratory tract infection elective surgery should be postponed, if possible, after the optimization of therapy. According to clinical setting, loco-regional anesthesia represents the desirable option since it allows to avoid airway instrumentation. Airway management goals are preventing the increase of airflow resistance during general anesthesia along with avoiding triggers of bronchospasm. When their use is possible, face mask ventilation and laringeal mask are considered more reliable than tracheal intubation for children with asthma. Sevoflurane is the most commonly used anesthetic for induction and manteinance. Salbutamol seems to be useful in preventing airflow resistance rise after endotracheal intubation. Mechanical ventilation should be tailored according to pathophysiology of asthma: an adequate expiratory time should be setted in order to avoid a positive end-expiratory pressure due to expiratory airflow obstruction. Pain should be prevented and promptly controlled with a loco-regional anesthesia technique when it is possible. Potential allergic reactions to drugs or latex should always be considered during the whole perioperative period. Creating a serene atmosphere should be adopted as an important component of interventions in order to guarantee the best care to the asthmatic child.

Laryngeal mask airways have a lower risk of airway complications compared with endotracheal intubation: a systematic review

PURPOSE

The purpose of the present study was to determine whether, in patients undergoing general anesthesia, those provided with a laryngeal mask airway (LMA) have a lower risk of airway-related complications than those undergoing endotracheal intubation.

MATERIALS AND METHODS

A systematic review of randomized prospective controlled trials was done to compare the risk of airway complications with an LMA versus an endotracheal tube (ETT) in patients receiving general anesthesia. Two independent reviewers identified 29 randomized prospective controlled trials that met the predetermined inclusion and exclusion criteria. The data for each individual outcome measure were combined to analyze the relative risk ratios (RRs). The Cochrane RevMan software was used for statistical analysis.

RESULTS

When an ETT was used to protect the airway, a statistically significant greater incidence of hoarse voice (RR 2.59, 95% confidence interval [CI] 1.55 to 4.34), a greater incidence of laryngospasm during emergence (RR 3.16, 95% CI 1.38 to 7.21), a greater incidence of coughing (RR 7.12, 95% CI 4.28 to 11.84), and a greater incidence of sore throat (RR 1.67, 95% CI 1.33 to 2.11) was found compared with when an LMA was used to protect the airway. The differences in the risk of regurgitation (RR 0.84, 95% CI 0.27 to 2.59), vomiting (RR 1.56, 95% CI 0.74 to 3.26), nausea (RR 1.59, 95% CI 0.91 to 2.78), and the success of insertion on the first attempt (RR 1.08, 95% CI 0.99 to 1.18) were not statistically significant between the 2 groups.

CONCLUSIONS

For the patients receiving general anesthesia, the use of the LMA resulted in a statistically and clinically significant lower incidence of laryngospasm during emergence, postoperative hoarse voice, and coughing than when using an ETT. The risk of aspiration could not be determined because only 1 study reported a single case of aspiration, which was in the group using the ETT.

Control of asthma for reducing the risk of bronchospasm in asthmatics undergoing general anesthesia and/or intravascular administration of radiographic contrast media

BACKGROUND

It is well known that patients suffering from bronchial asthma undergoing surgical procedures requiring general anesthesia (GA) or the administration of water soluble radiographic contrast media (RCM) have an increased risk of potentially severe bronchospasm. Nevertheless, little attention has been devoted to the possible preventive measures to reduce the occurrence of this potentially life-threatening event. It has been shown that the most important risk factor for bronchospasm during GA induction and/or the use of RCM is represented by a high degree of bronchial hyperreactivity with airway instability not adequately controlled by long-term anti-inflammatory treatment.

AIMS

The aim of this commentary is to underline the need for an accurate clinical and functional evaluation of asthmatics undergoing surgical procedures requiring GA or radiological procedures requiring the administration of RCM, as well as to suggest a stepwise preventive pharmacological approach for reducing the risk of bronchospasm.

METHODS

The authors' suggestions represent clinical experience of the respiratory section of an internal hospital-based working group whose aim is the prevention of asthmatic/anaphylactic/anaphylactoid reactions during the administration of anesthetics and/or RCM. The MEDLINE database was searched with a combination of keywords: general anesthesia, radio contrast media [and] bronchial asthma. The main limitation of this commentary is the scarcity of available literature on this topic.

FINDINGS

The authors suggest a therapeutic approach before surgical procedures requiring GA and/or RCM administration based on the degree of asthma control as assessed by clinical/functional criteria. In this setting, in addition to the necessity of obtaining the best control of airway reactivity, the authors suggest that an optimal control of asthma symptoms in 'real life' conditions might likely constitute a safety issue in asthmatic patients in the case of emergency procedures.

Comparison between intubation and the laryngeal mask airway in moderately obese adults

BACKGROUND

Obesity is a well-established risk factor for perioperative pulmonary complications. Anaesthetic drugs and the effect of obesity on respiratory mechanics are responsible for these pathophysiological changes, but tracheal intubation with muscle relaxation may also contribute. This study evaluates the influence of airway management, i.e. intubation vs. laryngeal mask airway (LMA), on postoperative lung volumes and arterial oxygen saturation in the early postoperative period.

METHODS

We prospectively studied 134 moderately obese patients (BMI 30) undergoing minor peripheral surgery. They were randomly assigned to orotracheal intubation or LMA during general anaesthesia with mechanical ventilation. Premedication, general anaesthesia and respiratory settings were standardized. While breathing air, we measured arterial oxygen saturation by pulse oximetry. Inspiratory and expiratory lung function was measured preoperatively (baseline) and at 10 min, 0.5, 2 and 24 h after extubation, with the patient supine, in a 30 degrees head-up position. The two groups were compared using repeated-measure analysis of variance (ANOVA) and t-test analysis. Statistical significance was considered to be P<0.05.

RESULTS

Postoperative pulmonary mechanical function was significantly reduced in both groups compared with preoperative values. However, within the first 24 h, lung function tests and oxygen saturation were significantly better in the LMA group (P<0.001; ANOVA).

CONCLUSIONS

In moderately obese patients undergoing minor surgery, use of the LMA may be preferable to orotracheal intubation with respect to postoperative saturation and lung function.

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.

Guideline-oriented perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease

Increased airway hyperresponsiveness is a major concern in the perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease. Guidelines using evidence-based medicine are continually being updated and published regarding the diagnosis, treatment, and prevention of these respiratory disorders. Perioperative management in these patients involves: (1) adequate control of airway hyperresponsiveness, including detection of purulent sputum and infection before surgery; (2) evidence-based control of anesthesia; and (3) the aggressive use of beta-2 adrenergic stimulants and the systemic administration of steroids for the treatment of acute attacks. Good preoperative control, including the use of leukotriene antagonists, can reduce the incidence of life-threatening perioperative complications. Awareness of recent guidelines is thus important in the management of patients with airway hyperresponsiveness. This review covers the most recent guidelines for the perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease.

Postoperative nausea, vomiting, airway morbidity, and analgesic requirements are lower for the ProSeal laryngeal mask airway than the tracheal tube in females undergoing breast and gynaecological surgery

BACKGROUND

We test the hypothesis that the frequency of postoperative nausea and vomiting is similar for the ProSeal laryngeal mask airway (LMA) and the tracheal tube.

METHODS

Two hundred consecutive female patients (ASA I-II, 18-75 yr) undergoing routine breast and gynaecological surgery were divided into two equal-sized groups for airway management with the ProSeal LMA or tracheal tube.

RESULTS

Ventilation was better and airway trauma less frequent for the ProSeal LMA. For the ProSeal group, the time spent in the post-anaesthesia care unit was shorter (69 vs 88 min, P < 0.0001); fewer doses of tropisetron were required in the post-anaesthesia care unit (P < or = 0.001) and ward (P = 0.004); morphine requirements were lower in the post-anaesthesia care unit (6.0 vs 8.1 mg, P = 0.005) and ward (6.1 vs 8.9, P = 0.004); nausea was less frequent at all times (overall: 13% vs 53%, P < 0.0001); vomiting was less frequent at 2 h (4% vs 18%, P = 0.003) and 24 h (5% vs 19%, P = 0.004); and sore throat was less frequent at all times (overall: 12% vs 38%, P < 0.0001).

CONCLUSIONS

The ProSeal LMA reduced the absolute risk of postoperative nausea and vomiting by 40% (53-13%). In patients without the need for morphine, the ProSeal LMA reduced the absolute risk of postoperative nausea and vomiting by 23% (37-14%). We conclude that the frequency of postoperative nausea, vomiting, airway morbidity, and analgesic requirements is lower for the ProSeal LMA than the tracheal tube in females undergoing breast and gynaecological surgery.

Postoperative pulmonary complications

PURPOSE OF REVIEW

Postoperative pulmonary complications, including pneumonia, bronchospasm, respiratory failure and prolonged mechanical ventilation, occur commonly and are a significant source of morbidity and mortality. This review will discuss the etiology of postoperative pulmonary complications and the interventions that reduce their risk.

RECENT FINDINGS

General anesthesia and surgery produce changes in the respiratory system and are responsible, along with underlying conditions, for postoperative pulmonary complications. Risk factors include upper abdominal or thoracic surgery, cigarette smoking, chronic respiratory disease, emergency surgery, anesthetic time of 180 min or more, age greater than 70 years, renal failure, poor nutritional status, and significant intraoperative blood loss. The inhibition of phrenic nerve output results in postoperative diaphragmatic dysfunction. Sleep-disordered breathing occurs after surgery even in patients without obstructive sleep apnea, but patients with obstructive sleep apnea may have a worsening of their disease after surgery. A clear advantage of one anesthetic technique over another in reducing postoperative pulmonary complications has not been demonstrated. Conflicting results have been obtained regarding the value of epidural analgesia in preventing postoperative pulmonary complications. Incentive spirometry decreases rates of postoperative pulmonary complications and hospital lengths of stay.

SUMMARY

Understanding risk factors for the development of postoperative pulmonary complications allows targeted interventions aimed at reducing their frequency and severity. Further research is needed to define the role of regional analgesic and anesthetic techniques in reducing postoperative pulmonary complications, and also to define the nature of risk factors and develop better predictive models of patients at risk of developing postoperative pulmonary complications.

Guided Insertion of the ProSeal Laryngeal Mask Airway Is Superior to Conventional Tracheal Intubation by First-Month Anesthesia Residents After Brief Manikin-Only Training

In the following pilot study, we compared conventional laryngoscope-guided tracheal intubation (tracheal intubation) and laryngoscope-guided, gum elastic bougie-guided ProSeal laryngeal mask airway insertion (guided ProSeal) for airway management by first-month anesthesia residents after brief manikin-only training. Five first-month residents with no practical experience of airway management were observed performing these techniques in 200 ASA I-II anesthetized, paralyzed adults. Each resident managed 40 patients, 20 in each group, in random order. The number of insertion attempts, effective airway time, ventilatory capability during pressure-controlled ventilation set at 15 cm H2O, airway trauma, and skill acquisition were studied. Data were collected by unblinded observers. Insertion was more frequently successful (100% versus 65%) and effective airway time was shorter (41 +/- 24 s versus 89 +/- 62 s) in the guided ProSeal group (both P < 0.0001). Expired tidal volume was larger (730 +/- 170 mL versus 560 +/- 140 mL) and end-tidal CO(2) lower (33 +/- 4 mm Hg versus 37 +/- 5 mm Hg) in the guided ProSeal group during pressure controlled ventilation (both P < 0.0001). Blood staining was more frequent on the laryngoscope (24% versus 2%; P < 0.0001) in the tracheal intubation group. There was evidence for skill acquisition in both groups. We conclude that laryngoscope-guided, gum elastic bougie-guided insertion of the ProSeal laryngeal mask airway is superior to conventional laryngoscope-guided tracheal intubation for airway management in terms of insertion success, expired tidal volume, and airway trauma by first-month anesthesia residents after brief manikin-only training. The guided ProSeal technique has potential for cardiopulmonary resuscitation by novices when conventional intubation fails.

Effect of prophylactic bronchodilator treatment with i.v. carperitide on airway resistance and lung compliance after tracheal intubation

BACKGROUND

Lung resistance increases after induction of anaesthesia. We hypothesized that prophylactic bronchodilation with i.v. carperitide before tracheal intubation would decrease airway resistance and increase lung compliance after placement of the tracheal tube in both smokers and nonsmokers.

METHODS

Ninety-seven adults aged between 24 and 59 yr were randomized to receive i.v. normal saline (0.9% saline) (control) or carperitide, 0.2 microg kg(-1) min(-1) throughout the study. The 97 patients included smokers and nonsmokers. Thus the patients were allocated to one of the four groups: smokers who received normal saline (n=21), nonsmokers who received normal saline (n=27), smokers who received carperitide (n=19) or nonsmokers who received carperitide (n=30). Thirty minutes after starting normal saline or carperitide infusion, we administered thiamylal 5 mg kg(-1) and fentanyl 5 microg kg(-1) to induce general anaesthesia and vecuronium 0.3 mg kg(-1) for muscle relaxation. Continuous infusion of thiamylal 15 mg kg(-1) h(-1) followed anaesthetic induction. Mean airway resistance (R(awm)), expiratory airway resistance (R(awe)) and dynamic lung compliance (C(dyn)) were determined 4, 8, 12 and 16 min after tracheal intubation and compared between the four groups.

RESULTS

At 4 min after intubation, R(awm) and R(awe) were higher and C(dyn) lower in smokers than in nonsmokers in the control group. R(awm) and R(awe) were lower and C(dyn) higher in smokers in the carperitide group than in smokers in the control group. R(awm) and R(awe) were lower in nonsmokers in the carperitide group than in nonsmokers in the control group.

CONCLUSIONS

Marked bronchoconstriction occurred in the control groups (smokers and nonsmokers) 4 min after tracheal intubation. Prophylactic treatment with carperitide before induction of anaesthesia and tracheal intubation was advantageous, particularly in smokers.

Strategies in the patient with compromised respiratory function

Respiratory diseases are commonly divided into restrictive or obstructive lung diseases. For anaesthesiological considerations restrictive lung diseases appear as a static condition with minimal short-term development. Overall, restrictive lung diseases don't lead to acute exacerbations due to the choice of anaesthetic techniques or the choice of anaesthesia-specific agents. Compared to restrictive lung diseases, obstructive lung diseases such as asthma or chronic obstructive lung diseases have a high prevalence and are one of the four most frequent causes of death. Obstructive lung diseases can be significantly influenced by the choice of anaesthetic technique and anaesthetic agent. Basically, the severity of the chronic obstructive pulmonary disease (COPD) and the degree of bronchial hyperreactivity will determine the perioperative anaesthetic risk. This risk has to be assessed by a thorough preoperative evaluation and will provide the rationale on which to decide the adequate anaesthetic technique. In particular, airway instrumentation can cause severe reflex bronchoconstriction. The use of regional anaesthesia alone or in combination with general anaesthesia can help to avoid airway irritation and even leads to reduced postoperative complications. Prophylactic anti-obstructive treatment, volatile anaesthetics, propofol, opioids, and an adequate choice of muscle relaxants minimize the anaesthetic risk when general anaesthesia is required. If intraoperative bronchospasm occurs, despite all precautions, deepening of anaesthesia, repeated administration of beta2-adrenergic agents and parasympatholytics, and a single systemic dose of corticosteroids are the main treatment options.

Preoperative assessment: pulmonary

Understanding the risk factors for the development of PPCs allows targeted interventions aimed at reducing the frequency and severity of PPCs. The broad categories of what increases the likelihood of developing a PPC are understood but specific understanding of how individual risk factors act to cause PPCs is lacking,and there is little information regarding the interaction or synergy between risk factors. Further research is needed to define the nature of risk factors and develop better predictive models of patients at risk for developing PPCs. It is clear that anesthetic agents produce significant changes in the respiratory system but further information is needed to define how such changes contribute, if at all, to the subsequent development of PPCs. The ongoing controversy regarding the value of regional analgesia or anesthetic techniques, especially epidural analgesia and anesthesia, in reducing or preventing PPCs requires well-done randomized clinical trials. Further research is also needed in the area of postoperative care such as interventions in patients with OSA or the use of inventive spirometric techniques.

Assessment and monitoring of flow limitation and other parameters from flow/volume loops

Flow/volume (F/V) spirometry is routinely used for assessing the type and severity of lung disease. Forced vital capacity (FVC) and timed vital capacity (FEV1) provide the best estimates of airflow obstruction in patients with asthma, chronic obstructive pulmonary disease (COPD) and emphysema. Computerized spirometers are now available for early home recognition of asthma exacerbation in high risk patients with severe persistent disease, and for recognition of either infection or rejection in lung transplant patients. Patients with severe COPD may exhibit expiratory flow limitation (EFL) on tidal volume (VT) expiratory F/V (VTF/V) curves, either with or without applying negative expiratory pressure (NEP). EFL results in dynamic hyperinflation and persistently raised alveolar pressure or intrinsic PEEP (PEEPi). Hyperinflation and raised PEEPi greatly enhance dyspnea with exertion through the added work of the threshold load needed to overcome raised pleural pressure. Esophageal (pleural) pressure monitoring may be added to VTF/V loops for assessing the severity of PEEPi: 1) to optimize assisted ventilation by mask or via endotracheal tube with high inspiratory flow rates to lower I:E ratio, and 2) to assess the efficacy of either pressure support ventilation (PSV) or low level extrinsic PEEP in reducing the threshold load of PEEPi. Intraoperative tidal volume F/V loops can also be used to document the efficacy of emphysema lung volume reduction surgery (LVRS) via disappearance of EFL. Finally, the mechanism of ventilatory constraint can be identified with the use of exercise tidal volume F/V loops referenced to maximum F/V loops and static lung volumes. Patients with severe COPD show inspiratory F/V loops approaching 95% of total lung capacity, and flow limitation over the entire expiratory F/V curve during light levels of exercise. Surprisingly, patients with a history of congestive heart failure may lower lung volume towards residual volume during exercise, thereby reducing airway diameter and inducing expiratory flow limitation.

The ProSeal laryngeal mask in myasthenia gravis

This case describes the anaesthesia management of a patient with myasthenia gravis who required mastectomy with axillary lymph node clearance. After withholding medical therapy for the myasthenia preoperatively on the day of surgery, anaesthesia was maintained with halothane, nitrous oxide and a remifentanil infusion. Muscle relaxants were avoided, facilitated by the use of a ProSeal (Intravent, Orthofix, Maidenhead, United Kingdom) laryngeal mask airway for positive pressure ventilation. The ProSeal laryngeal mask airway is a new laryngeal mask device with a modified cuff and a drainage tube which has been shown to have advantages over older designs for use during positive pressure ventilation. The rationale for the management of this patient with myasthenia is discussed.

Impact of laryngeal mask airway and tracheal tube on pulmonary function during the early postoperative period

BACKGROUND

The tracheal tube (TT) produces reversible bronchoconstriction and increases pulmonary airway resistance compared to the laryngeal mask airway (LMA). The possible persistence of this effect in the postoperative period has not been studied. The aim of this study was to compare the early postoperative pulmonary function in healthy patients undergoing minor surgical procedures with the LMA or with the TT.

METHODS

Sixty patients scheduled for saphenous vein stripping under general anaesthesia were randomised to receive the LMA or the TT. Before anaesthesia and 20 min after LMA or TT removal, pulse oxymetry values (SpO(2)) were recorded and patients performed forced spirometry in the supine position.

RESULTS

Preoperative pulmonary function was normal in both groups. There were no differences between groups in the preoperative respiratory function test and SpO(2). Following surgery SpO(2), forced expiratory volume in the first second (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF) decreased in both groups. The FEV1/FVC did not change in either of the groups. In the TT group, compared to patients using the LMA, there was a greater relative decrease of SpO(2) (2.7 +/- 2.7% vs. 1.3 +/- 2.2%, P=0.017), FEV1 (17.6 +/- 12.2% vs. 8 +/- 17.4%, P=0.008), FVC (15.8 +/- 12.4% vs. 9 +/- 13.4%, P=0.023) and PEF (20.6% +/- 15.3% vs. 8.1 +/- 33.3%, P=0.033).

CONCLUSIONS

This study demonstrates greater early postoperative respiratory restrictive syndrome and lower arterial oxygen saturation following tracheal intubation compared to LMA use in patients without respiratory disease.

Newer neuromuscular blocking agents: how do they compare with established agents?

Rapacuronium bromide (rapacuronium; ORG-9487) is a nondepolarising muscle relaxant (NMBA) with a low potency [90% effective dose (ED90) 1 mg/kg], which to some extent is responsible for its rapid onset of action. Because of the high plasma clearance (5.3 to 11.1 mg/kg/min) of rapacuronium, its clinical duration of action following single bolus doses up to 2 mg/kg in adults is short (i.e. <20 minutes). Rapacuronium forms a pharmacologically active 3-desacetyl metabolite, ORG-9488, which may contribute to a delay in spontaneous recovery after repeat bolus doses or infusions. After rapacuronium 1.5 mg/kg clinically acceptable intubating conditions are achieved within 60 to 90 seconds in the majority of adult and elderly patients undergoing elective anaesthesia. However, in a rapid-sequence setting. intubating conditions are less favourable after rapacuronium 1.5 to 2.5 mg/kg than after succinylcholine. The most prominent adverse effects of rapacuronium (tachycardia, hypotension and bronchospasm) are dose-related, and in particular pulmonary adverse effects are observed more frequently under conditions of a rapid-sequence induction in adults. Therefore, it seems worthwhile to consider only doses of rapacuronium < or = 1.5 mg/kg to facilitate rapid tracheal intubation, and to use succinylcholine or rocuronium rather than rapacuronium in a rapid-sequence setting. Rapacuronium, however, is a suitable alternative to mivacurium chloride (mivacurium) and succinylcholine for short procedures (e.g. ambulatory anaesthesia). Rocuronium bromide (rocuronium) is a relatively low-potent, intermediateacting NMBA. Its main advantage is the rapid onset of neuromuscular block whereby good or excellent intubating conditions are achieved within 60 to 90 seconds after rocuronium 0.6 mg/kg (2 x ED95), and within 60 to 180 seconds after smaller doses (1 to 1.5 x ED95). Larger doses of rocuronium (> or = 1 mg/kg) seem to be suitable for rapid-sequence induction under relatively light anaesthesia. However, it is still a matter of controversy whether, in the case of an unanticipated difficult intubation, the long duration of rocuronium administered in such large doses outweighs the many adverse effects of succinylcholine. Rocuronium has mild vagolytic effects and does not release histamine, even when administered in large doses. Rocuronium is primarily eliminated via the liver and its pharmacokinetic profile is similar to that of vecuronium bromide (vecuronium). Unlike vecuronium, rocuronium has no metabolite. Cisatracurium besilate (cisatracurium), the IR-cis, 1'R-cis isomer of atracurium besilate (atracurium) is approximately 4 times more potent than atracurium. The onset time of cisatracurium is significantly slower than after equipotent doses of atracurium. The recommended intubating dose is 0.15 to 0.2 mg/kg (3 to 4 times ED95). Over a wide range of clinically relevant doses the recovery properties of cisatracurium are affected by neither the size of the bolus dose nor by the duration of infusion. Unlike atracurium, cisatracurium does not trigger histamine release. Like atracurium, cisatracurium undergoes Hofmann elimination. In contrast to atracurium, cisatracurium does not undergo hydrolysis by nonspecific plasma esterases. Moreover, about 77% of the drug is cleared by organ-dependent mechanisms.

Sevoflurane EC50 and EC95 values for laryngeal mask insertion and tracheal intubation in children

The laryngeal mask airway (LMA) is a simple, easy to use and safe method for airway control in children. Its insertion needs less anaesthetic, and haemodynamic responses and postoperative sequelae are less than with laryngoscopy and tracheal intubation. This study was designed to determine the end-tidal concentrations of sevoflurane where 50% (EC50) and 95% (EC95) of the attempts to secure the airway would be successful. We randomly assigned 40 children aged 4-12 yr undergoing general surgery to either LMA insertion (n=20) or to laryngoscopy and tracheal intubation (n=20) under sevoflurane anaesthesia. The initial end-tidal concentration of sevoflurane for each child was determined according to the response of the previous child in the same group. Up to three attempts to secure the airway with increasing sevoflurane end-tidal concentrations in 0.3% steps were allowed for each child. The logistic regression model was used to calculate the EC50 and EC95 values. Sevoflurane provided good conditions for both LMA insertion, and laryngoscopy and tracheal intubation without serious adverse effects. The EC50 and the EC95 of sevoflurane were 1.57 (SD 0.33)% and 2.22% for LMA insertion and 2.20 (SD 0.31)% and 2.62% for laryngoscopy and tracheal intubation. Thus, less sevoflurane is required for LMA insertion in children than for laryngoscopy and tracheal intubation.

The laryngeal mask airway: a comprehensive review for the Emergency Physician

The Laryngeal Mask Airway (LMA) was developed in the 1980s, but has only recently begun to be used in Emergency Medicine. The LMA affords effective assisted ventilation without requiring endotracheal intubation or visualization of the glottis. In doing so, it is more efficacious than a bag-valve-mask apparatus, although the risk of aspiration of gastric contents persists, particularly if the device is not properly placed. The LMA also has significant potential utility in management of the difficult airway. Most reported clinical experience with the LMA has come from the operating room. This article provides an overview of the extensive potential utility of the LMA in the Emergency Department and prehospital settings as well as a comprehensive review of the pertinent advantages, disadvantages, and complications associated with its use.

Airway management

The last decade of the millennium has witnessed the introduction of new extratracheal airway devices for use in fasted patients undergoing ambulatory anaesthesia. A growing awareness of the potential of such devices in the difficult airway has contributed to their increasing use.