Adverse Airway Events Research Articles

Insufflation vs intubation during esophagogastroduodenoscopy in children

We compared adverse airway events during esophagogastroduodenoscopy (EGD) in children managed with insufflation vs intubation. Optimum airway management during EGD in children remains undecided. Following IRB approval and written informed parental consent, children between 1 and 12 years of age presenting for EGD were randomized to airway management with insufflation (Group I), intubation/awake extubation (Group A), or intubation/deep extubation (Group D). All subjects received a standardized anesthetic with sevoflurane in oxygen. Using uniform definitions, airway adverse events during and after EGD recovery were recorded. Categorical data were analysed with Chi-square contingency tables or Fisher's exact test as appropriate. Analyzable data were available for 415 subjects (Group I: 209; Group A: 101; Group D: 105). Desaturation, laryngospasm, any airway adverse event, and multiple airway adverse events during EGD were significantly more common in subjects in Group I compared to those in Groups A and D. Complaints of sore throat, hoarseness, stridor, and/or dysphagia were more common in subjects in Groups A and D. Analysis of confounders suggested that younger age, obesity, and midazolam premedication were independent predictors of airway adverse events during EGD. Insufflation during EGD was associated with a higher incidence of airway adverse events, including desaturation and laryngospasm; intubation during EGD was associated with more frequent complaints related to sore throat. As our results show that insufflation during EGD offers no advantage in terms of operational efficiency and is associated with more airway adverse events, we recommend endotracheal intubation during EGD, especially in patients who are younger, obese, or have received midazolam premedication.

The use of capnography and the availability of airway equipment on Intensive Care Units in the UK and the Republic of Ireland*

At least 20% of reported major adverse airway events occur on the intensive care unit. This study surveyed 315 (96%) of all general, satellite, hepatobiliary, cardiac and neuro-intensive care units in the UK and the Republic of Ireland, finding that only 100 (32%) units always use capnography for tracheal intubation while only 80 (25%) always use capnography for continuous monitoring of patients requiring controlled ventilation. Three hundred and ten (98%) units utilise a checklist of airway equipment, 311 (99%) check its functionality on a daily basis and 296 (94%) units have access to a bronchoscope. Whilst 297 (94%) ICUs have an airway trolley, sufficient equipment for unanticipated difficult intubation was only seen on 33 (10%) of units. Guidelines addressing minimum standards for monitoring and airway safety on ICU are not being met and remain below the standard expected.

Simulation training at the point of care to decrease the incidence of airway complications on the intensive care unit

A recent analysis of critical incidents reported to the National Patient Safety Agency (NPSA) by ICUs in the UK revealed a significant number of airway incidents in critical care [1]. We recently performed an online survey with responses from 305 trainees from across the UK regarding airway management and complications on the ICU. The results revealed a high number of adverse airway events including 27 deaths. A large number of junior trainees (many of whom cover the ICU alone at night) expressed low confidence levels with airway management in critical care, and the majority of all trainees felt inexperienced with tracheostomy care and emergencies. Simulation has been recommended as a suitable way of providing critical incident training [2], and simulation at the point of care has been shown to be especially powerful and effective [3].

Predictors of Emesis and Recovery Agitation With Emergency Department Ketamine Sedation: An Individual-Patient Data Meta-Analysis of 8,282 Children

Ketamine is widely used in emergency departments (EDs) to facilitate painful procedures; however, existing descriptors of predictors of emesis and recovery agitation are derived from relatively small studies. We pooled individual-patient data from 32 ED studies and performed multiple logistic regression to determine which clinical variables would predict emesis and recovery agitation. The first phase of this study similarly identified predictors of airway and respiratory adverse events. In 8,282 pediatric ketamine sedations, the overall incidence of emesis, any recovery agitation, and clinically important recovery agitation was 8.4%, 7.6%, and 1.4%, respectively. The most important independent predictors of emesis are unusually high intravenous (IV) dose (initial dose of > or =2.5 mg/kg or a total dose of > or =5.0 mg/kg), intramuscular (IM) route, and increasing age (peak at 12 years). Similar risk factors for any recovery agitation are low IM dose (<3.0 mg/kg) and unusually high IV dose, with no such important risk factors for clinically important recovery agitation. Early adolescence is the peak age for ketamine-associated emesis, and its rate is higher with IM administration and with unusually high IV doses. Recovery agitation is not age related to a clinically important degree. When we interpreted it in conjunction with the separate airway adverse event phase of this analysis, we found no apparent clinically important benefit or harm from coadministered anticholinergics and benzodiazepines and no increase in adverse events with either oropharyngeal procedures or the presence of substantial underlying illness. These and other results herein challenge many widely held views about ED ketamine administration.

Desflurane requirements for laryngeal mask airway insertion during inhalation induction

We hypothesized that the simultaneous use of low concentrations (<6%) of desflurane, nitrous oxide (N(2)O), and fentanyl would allow a laryngeal mask airway (LMA) to be inserted safely with inhalation induction of desflurane, even in nonparalyzed patients. This prospective, observational study was performed to determine the 50% effective concentration (EC(50)) of desflurane for LMA insertion in such patients. Twenty-two adult patients undergoing ambulatory surgical procedures under general anesthesia using an LMA were included in the study. Fentanyl was administered intravenously at 1.5 microg x kg(-1), and anesthesia was induced with desflurane in 50% N(2)O and oxygen, using a normal tidal volume breathing technique. Subsequently, a preselected steady-state end-tidal desflurane concentration was maintained for 10 min before insertion of the LMA. Successful LMA insertion was defined as the absence of adverse airway responses until cuff inflation. Target concentrations of desflurane for LMA insertion were determined using a modified Dixon's up-and-down method (starting dose, 5%; step size, 0.5%). All 22 patients completed the study without adverse events related to airway irritation. The EC(50) of desflurane for insertion of the LMA was determined to be 3.61 +/- 0.31%, and the 95% confidence interval (CI) of the EC(50) obtained using probit analysis was 3.13-3.90. We demonstrated that N(2)O-desflurane inhalation induction with a normal tidal breathing technique after premedication with fentanyl can be used safely without any adverse airway events in nonparalyzed patients. In such patients, the EC(50) of desflurane for successful LMA insertion was 3.61 +/- 0.31% (95% CI, 3.13-3.90).

Commentary: Bouza C et al. (2007). Unplanned extubation in orally intubated medical patients in the ICU: a prospective cohort study

AbstractBackground: Unplanned endotracheal extubation (UE) is recognized as the most common airway adverse event in the intensive care unit (ICU).Objectives: We examined the incidence, circumstances, and outcome of UE in orally intubated medical patients in the ICU.Methods: We performed a 12‐month prospective cohort study in a tertiary‐care medical ICU.Results: A total of 344 consecutive adults who were orally intubated and mechanically ventilated for 3710 days were included. The overall incidence density of UE was 0·92 of 100 days of ventilation. Eight episodes (24%) occurred in patients receiving mechanical ventilation (MV) and not in the weaning process versus 26 episodes (76%) in patients scheduled for weaning. UE was reported as intentional in 71% of cases and as accidental in 29% of cases. In 59% of UE cases, patients were without caregivers at the bedside when the episode took place, and 46% of cases occurred during the night shift. Reintubation was required in 41% of patients and was strongly associated with the accidental nature of the episode [odds ratio (95% confidence interval): 4.3 (1.9–9.6)]. Compared with patients without UE, patients with UE had a lower mortality rate [odds ratio (95% confidence interval): 0·21 (0·6–0·8)] but longer days on MV (11.5 versus 5, P _ 0·09) and ICU stay (13.5 versus 6, P _ 0·08).Conclusions: This study does not confirm the highest rates of UE previously reported in orally intubated medical patients in the ICU or the association with mortality in this scenario. However, UE increased the need for MV and ICU care. We found a moderate to high prevalence of potentially modifiable risk factors for UE, suggesting unsatisfactory ICU practices. Abstract reprinted from Heart &amp; Lung, volume 36, Bouza C et al., ‘Unplanned extubation in orally intubated medical patients in the ICU: a prospective cohort study.’, pages 270–276. ©2007, reproduced with permission from Elsevier Limited.

Part Task and Variable Priority Training in First-year Anesthesia Resident Education

Part task training (PTT) focuses on dividing complex tasks into components followed by intensive concentrated training on individual components. Variable priority training (VPT) focuses on optimal distribution of attention when performing multiple tasks simultaneously with the goal of flexible allocation of attention. This study explored how principles of PTT and VPT adapted to anesthesia training would improve first-year anesthesiology residents' management of simulated adverse airway and respiratory events. The authors hypothesized that participants with PTT and VPT would perform better than those with standard training. Twenty-two first-year anesthesia residents were randomly divided into two groups and trained over 12 months. The control group received standard didactic and simulation-based training. The experimental group received similar training but with emphasis on PTT and VPT techniques. Participant ability to manage seven adverse airway and respiratory events were assessed before and after the training period. Performance was measured by the number of correct tasks, making a correct diagnosis, assessment of perceived workload, and an assessment of scenario comprehension. Participants in both groups exhibited significant improvement in all metrics after a year of training. Participants in the experimental group were able to complete more tasks and answered more comprehension questions correctly. There was no difference in perceived workload or the number of correct diagnoses between groups. This study in part confirmed the study hypotheses. The results suggest that VPT and PTT are promising adjuncts to didactic and simulation-based training for management of adverse airway and respiratory events.

Obesity Does Not Increase Airway Adverse Events

Obesity Does Not Increase Airway Adverse Events

Unplanned extubation in orally intubated medical patients in the intensive care unit: A prospective cohort study

Unplanned endotracheal extubation (UE) is recognized as the most common airway adverse event in the intensive care unit (ICU). We examined the incidence, circumstances, and outcome of UE in orally intubated medical patients in the ICU. We performed a 12-month prospective cohort study in a tertiary-care medical ICU. A total of 344 consecutive adults who were orally intubated and mechanically ventilated for 3710 days were included. The overall incidence density of UE was .92 of 100 days of ventilation. Eight episodes (24%) occurred in patients receiving mechanical ventilation (MV) and not in the weaning process versus 26 episodes (76%) in patients scheduled for weaning. UE was reported as intentional in 71% of cases and as accidental in 29% of cases. In 59% of UE cases, patients were without caregivers at the bedside when the episode took place, and 46% of cases occurred during the night shift. Reintubation was required in 41% of patients and was strongly associated with the accidental nature of the episode (odds ratio [95% confidence interval]: 4.3 [1.9-9.6]). Compared with patients without UE, patients with UE had a lower mortality rate (odds ratio [95% confidence interval]: .21 [.6-.8]) but longer days on MV (11.5 vs 5, P = .09) and ICU stay (13.5 vs 6, P = .08). This study does not confirm the highest rates of UE previously reported in orally intubated medical patients in the ICU or the association with mortality in this scenario. However, UE increased the need for MV and ICU care. We found a moderate to high prevalence of potentially modifiable risk factors for UE, suggesting unsatisfactory ICU practices.

Capnography and Depth of Sedation During Propofol Sedation in Children

To evaluate the relationship between continuous capnography and observed airway and respiratory adverse effects and the depth of sedation when using propofol for pediatric orthopedic procedures. We administered propofol after opioid premedication in a prospective convenience sample of children undergoing orthopedic reduction in our emergency department (ED). All children received supplemental oxygen (1 L/minute by nasal cannula) and continuous capnography and had depth of sedation assessed every 2 minutes. Adverse airway or respiratory events and any associated interventions were recorded. Adverse airway or respiratory events with intervention occurred in 14 of the 125 enrolled children (11%; 95% confidence interval 4.0% to 14%): jaw thrust in 4, supplemental oxygen in 6, and bag-valve-mask ventilation in 4. All interventions required were brief (<30 seconds). Capnography detected apnea before clinical examination or pulse oximetry in all 5 occurrences and similarly first detected airway obstruction in 6 of the 10 occurrences. The median maximal modified Ramsay score was 6 (range 3 to 8), ie, deep sedation. When propofol is administered for ED deep sedation to facilitate pediatric orthopedic reduction, continuous capnography detects most airway and respiratory events leading to intervention before clinical examination or pulse oximetry.

The safety of preoperative sedation in children with sleep-disordered breathing

To prospectively monitor children who received preoperative sedation with midazolam hydrochloride prior to adenotonsillectomy (T&A) for treatment of sleep-disordered breathing with continuous pulse-oximetry to detect potential respiratory compromise. Prospective, observational study. Hospital-based pediatric otolaryngology practice. Seventy children, aged 1-12 years, diagnosed with sleep-disordered breathing by clinical evaluation or polysomnography (PSG), with a median RDI of 14.25, undergoing T&A. Children underwent a standardized anesthesia protocol including preoperative oral midazolam hydrochloride 0.5mg/kg, standard American Society of Anesthesiologists (ASA) monitoring, mask induction with sevoflurane, muscle relaxant with reversal if indicated, and intravenous dexamethasone sodium phosphate 0.5mg/kg. Children were monitored in the hospital until discharge criteria were met. Selected children with severe OSA were monitored overnight on the pediatric floor or the pediatric intensive care unit. Adverse respiratory events were defined as upper airway obstruction, hypoventilation, desaturation, bradycardia, or sustained lethargy. Incidence of pre and postoperative obstructive complications. During the study period only two patients (2.9%) had a measurable adverse event directly related to the administration of the sedation. Based on sporadic reports of adverse airway events in children with obstructive sleep apnea receiving sedation, these children frequently do not receive preoperative sedation. Given the low morbidity of preoperative sedation in our population, many children with sleep-disordered breathing may safely be pre-medicated.

Passive smoke exposure as a risk factor for airway complications during outpatient pediatric procedures

Determine if passive smoke exposure (PSE) increases airway complications during outpatient mask anesthesia procedures in children. A prospective cohort of children who underwent surgical procedures under mask anesthesia was studied with the American Thoracic Society children's questionnaire on environmental and respiratory factors. Double-blinded outcomes with respect to adverse airway events were recorded both intraoperatively and in the recovery room for patients with and without passive smoke exposure. Multivariate comparisons assessing the likelihood of these airway complications were conducted between the PSE and nonexposed groups. Of 405 children, 168 (41.5%) had PSE. The incidence of airway complications during anesthesia or postanesthetic recovery was higher for all outcome measures for PSE children (all P </= 0.005), except for recovery room breath holding (P = 0.086). Intraoperative laryngospasm and airway obstruction were 4.9 and 2.8 times more likely with PSE, respectively. PSE significantly increases the risk of anesthesia-related airway complications during outpatient pediatric procedures. A-1b.

Can Bispectral Index aid laryngeal mask placement in children?

Laryngeal mask airway (LMA) placement requires an adequate depth of anesthesia to prevent patient movement and adverse airway responses. Patient movement, coughing, stridor or laryngospasm at LMA placement may result in transient hypoxia, injury to the patient and prolong time spent in the anesthetic room. The Bispectral Index Score (BIS) is a relatively new tool that has not yet established its place in routine clinical pediatric anesthesia practice. One potential use may be to predict an adequate depth of anesthesia for successful intraoperative interventions such as LMA placement in children. A total of 116 children aged between 1 and 16 years due to have an LMA placed under general anesthesia were enrolled into this prospective, blinded observational study. Complication or success of LMA placement was then analyzed in relation to the BIS value at the time of placement. Other clinical variables were also considered. The difference in BIS values in children with complicated compared with successful LMA placement was small and BIS therefore appears not to be a reliable predictor for either. Inexperience of the anesthetist and a history of recent upper respiratory tract infection (URTI) may be better indicators for complications. Bispectral Index Score appears, from this study, not to be a useful tool to help predict complications of LMA placement or to help reduce airway complications during LMA placement. Other markers may be more useful predictors of adverse airway events.

To BIS or Not to BIS? That Is the Question

T his editorial accompanies two papers (1,2) on the use of the Bispectral Index (BIS) as a sedation index in children. Before discussing the salient elements and findings of these papers, it is instructive to consider what processed electroencephalogram (EEG) monitors actually measure. As an analogy, consider the dark days before the introduction of pulse oximetry into clinical practice, when clinicians generally used something that might approximate to a four-point scale (pink/slightly blue/ dark blue/black) to assess oxygenation. The introduction of pulse oximetry gave a continuous measure of oxygen saturation as a percentage of saturated hemoglobin and quickly became the gold standard for measuring oxygenation, despite the lack of prospective randomized trial evidence of improved outcomes (3). Similarly, we have multiple discontinuous clinical scales for describing sedation levels in adults, including the Observer’s Assessment of Alertness and Sedation (OAAS) and the Ramsay scales. The purpose of processed EEG monitors is to provide a continuous measure that encompasses the full range of sedation levels measured by the discontinuous scales. Pulse oximetry measures a physiological parameter that most physicians can readily understand (oxygen saturation). In contrast, processed EEG monitors calculate a mathematical abstraction of the electroencephalogram, a concept less familiar and less accessible to the practicing clinician. BIS was derived by empirically estimating the EEG parameters that best predicted OAAS measurements in a large patient and volunteer database of subjects receiving hypnotics and opioids. As a continuous measure that correlates to OAAS measures obtained from subjects receiving hypnotic drugs, BIS may be described as a “probability of state” measure, reflecting the complex nature of consciousness (4). Being derived from the OAAS, BIS should be expected to correlate well with the OAAS. The correlation would probably be less strong with other rating scales, such as the Ramsay scale, the modified maintenance of wakefulness test (MMWT) scale used in pediatrics, or the University of Michigan sedation scale (UMSS). These latter scales were not part of the database used to develop the BIS monitor, and the original database was entirely constructed from adult EEG data. Normal pediatric EEG differs markedly from adult EEG, displaying more variation than adult EEG (5,6). This may make processed EEG parameters less reliable in children. In general, the electrical activity of the brain changes during growth and development, warranting age-specific considerations and cautious interpretation of EEG data in the pediatric population. Despite such theoretical concerns, studies suggest that the performance of BIS in pediatric patients older than 6 months of age may be similar to that of adults (7–9). In younger infants, brain maturation and development may render processed EEG measures unreliable. However, McDermott et al. (8) still found a significant correlation between BIS and the UMSS in patients younger than 6 months of age in a small group of patients. In this issue of Anesthesia & Analgesia, Malviya et al. (1) report on the observed relationship between BIS and two observational measures, the UMSS and MMWT, in children 1 month to 17 years conceptual age. In lieu of clinical guidelines that call for delineation of sedation states, the investigators were particularly interested in the ability of different measures to discriminate conscious from deep sedation. Data from 39 patients were included, comprising repeated measurements (about 8 per individual on average) of sedation indices after unspecified procedures that required sedation/analgesia or general anesthesia. The authors report good correlation between UMSS and BIS ( 0.73), indicating reasonable concordance between these discontinuous and continuous scales. This supports the validity of BIS as a pediatric sedation monitor and complements similar reports by this group (10) and others (8). MMWT scores, by contrast, correlated weakly (0.36) with BIS, in contrast to earlier Dr. Peter S. Sebel is a paid consultant to Aspect Medical Systems. Accepted for publication November 16, 2005. Address correspondence and reprint requests to Peter S. Sebel, MB BS, PhD, MBA, Department of Anesthesiology, Emory University School of Medicine, 49 Jesse Hill Jr. Drive, SE, Atlanta, GA 30303. Address e-mail to peter_sebel@emoryhealthcare.org.

A PROSPECTIVE AUDIT OF DESFLURANE ANAESTHESIA IN THE UNIVERSITY OF MALAYA MEDICAL CENTRE DAY SURGERY UNIT

We evaluated the use of Desflurane anaesthesia in this prospectiveobservational audit in the University of Malaya Medical Centre Day Surgery Unit. Fifty ASA I-II unpremedicated day surgery patients received fentanyl and propofol induction after preoxygenation. Desflurane was introduced initially at 2% and the concentration was increased gradually to 4%, then 6%, 8% and 10% in nitrous oxideand oxygen. Patients breathed spontaneously throughout the surgery. Desflurane was switched off at the end of surgery and patients breathed 100% oxygen. The haemodynamic effect, perioperative complications and recovery profiles were recorded. Systolic arterial pressure and heart rate decreased after induction of anaesthesia butreturned to baseline value at discharge. Adverse airway event such as coughing and postoperative nausea and vomiting are two unwanted complications.

Effect of breathing low concentrations of volatile anaesthetic agents on incidence of adverse airway events

The effect of breathing 0.1 minimum alveolar concentrations (MAC) of desflurane or isoflurane for three minutes on the incidence of adverse airway events on a subsequent breath of 2 MAC was investigated. Twenty-five volunteers known to develop an adverse airway event to desflurane or isoflurane took part in the study. Each volunteer was exposed to isoflurane and desflurane at least 24 h apart. Volunteers were assessed for adverse airway events while breathing 2 MAC inhalational anaesthetic following breathing 100% O(2) for 3 min. This was repeated with 0.1 MAC inhalational anaesthetic in oxygen instead of 100% O(2). Adverse airway events decreased from 88% to 40% when tests were conducted with desflurane (p = 0.002). With isoflurane, the reduction from 60% to 52% was not statistically significant (p = 0.774). Breathing low concentrations of desflurane decreases the incidence of adverse airway events on subsequent inhalation of higher concentration of desflurane.

Minimum inspired oxygen concentration alarm

EDITOR: The use of anaesthetic machine and patient monitor alarms, in addition to clinical observation, can enhance patient safety, but it is very important that these limits are accurately set. The importance of these settings is highlighted by a critical incident which occurred recently in one of our theatres. Case report: An 8-yr-old, American Society of Anesthesiologists (ASA) I patient was scheduled for an elective ear, nose and throat procedure. Induction was uneventful and general anaesthesia was maintained with spontaneous ventilation via a laryngeal mask. The patient's head was draped and surgery commenced. An unobserved disconnection occurred at the junction of the circle-system breathing circuit tubing and the filter to which the gas analyser sampling line was attached (Fig. 1). The reduced movement of the reservoir bag was not initially noticed and the capnography trace continued as per normal. The inspired oxygen concentration decreased but the alarm did not sound as its setting had not been changed from the factory default of 18% for oxygen. Had it been set to above 21% it would have been activated. Fortunately the disconnection was discovered and the circuit reconnected before the patient sustained any harm.Figure 1.: Site of disconnection between circle breathing system and filter.The case prompted an audit at two hospitals in our region which demonstrated that the minimum inspired oxygen concentration alarm was changed from the factory reset by less than 10% of anaesthetists. Personal communication with a colleague from a neighbouring region revealed that two identical incidents had recently occurred in their hospital, and the same audit is at present being conducted in their hospital. Fortunately no patient suffered any harm as a result of the disconnections but the potential for patient awareness, movement, adverse airway events and hypoxia is evident. The use of an oxygen analyser is mandatory in accordance with the checklist for anaesthetic apparatus as set out by the Association of Anaesthetists of Great Britain and Ireland and is recommended in many other countries [1]. The Association guidelines however give no advice regarding the values to which the analyser's alarm limits should be set [2]. Oxygen concentrations are usually measured at either the fresh gas outlet or via the end-expired gas sampling line attached to, or near to, the filter. In addition to guarding against the delivery of hypoxic mixtures, the analyser (sampling end-tidal gases) can also help to detect problems with breathing circuit and ventilator integrity, and with alveolar hypoventilation [3,4]. A study by Knaack-Steinegger showed that disconnections were evident within 30 s using expired oxygen concentration alarms [5]. Disconnections are evident within a few breaths when using end-tidal gas monitoring with oxygen concentration alarms set to above 21%. Capnography alarms and the waveform are used by anaesthetists as a monitor for early detection of problems with patients' ventilation, including disconnections in the breathing system. In spontaneously breathing patients, where there is a disconnection proximal to the capnography sampling point, the capnography trace may well continue as per normal and hence this alarm would not detect the disconnection. An anaesthetic agent analyser is also useful to detect disconnections in a breathing system and guard against patient awareness, but factory default settings of 0% would need to be reset to minimum alveolar concentration (MAC) awake or above. The audit performed in our hospital also investigated the alarm settings of the agent analyser and found that in no theatres were the limits changed to above 0%. The oxygen alarms are often not set above 21% as doing so results in the alarm sounding when there is no (enriched) oxygen flowing through the circuit. This can be overcome by leaving the sampling line in continuity with the circuit and allowing a small quantity of oxygen to flow (most modern anaesthetic machines have a minimum oxygen flow preset). An alternate solution is to cap the circuit off at the end of the case. This also helps to prevent wastage of anaesthetic gases and stops the anaesthetic agent analyser alarm sounding (if set above 0%). Ventilator pressure alarms can detect leaks during mechanical ventilation, but they are not foolproof [6]. The minimum inspired oxygen alarm is a useful monitor but should be set above 21%, especially for spontaneously breathing patients and when the circuit is covered. Setting the anaesthetic agent alarm to above 0% further adds to patient safety. M. T. Dale D. Jadhav *Department of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, Leicester, England

Adverse airway events during brief nasal inhalations of volatile anaesthetics: the effect of humidity and repeated exposure on incidence in volunteers preselected by response to desflurane.

Twelve volunteers known to have airways that responded adversely to 2.0 MAC desflurane were recruited. Each volunteer inhaled three single breaths of each of 0.5, 1.0 and 2.0 MAC of sevoflurane, halothane, isoflurane, desflurane and balance air, with breaths of air between, whilst breathing nasally through a face mask attached to one of three filters that provided three different levels of humidification. The incidence of any adverse airway events was recorded. The anaesthetic inhaled significantly affected the incidence of adverse airway events (p < 0.001), with the least to most irritant being sevoflurane, halothane, isoflurane and desflurane. Increasing the concentration of anaesthetic also significantly increased the incidence of adverse airway events (p < 0.001). The filter used, and hence the level of humidification, did not affect the incidence of adverse airway events (p = 0.09), but repeated exposure caused a significant reduction in the incidence of adverse airway events (p < 0.001).

Cuffed oropharyngeal airway as a suitable alternative to the laryngeal mask airway for minor outpatient surgery

Background and objective: To compare the application of the cuffed oropharyngeal airway and the laryngeal mask airway on anaesthetized adult patients undergoing minor outpatient surgery. Methods: One hundred patients received intravenous fentanyl, propofol and N2O for the induction and maintenance of anaesthesia. The patients were randomly divided into two groups: a cuffed oropharyngeal airway group (n = 50) and a laryngeal mask airway group (n = 50). After insertion of the device, fibreoptic laryngoscopy was attempted and the degree of success scored. We then compared the first application success rate of both procedures while judging airway intervention requirement, fibreoptic scores, adverse airway events and haemodynamic tolerance. Results: Both devices had an almost similar first-time placement rate (cuffed oropharyngeal airway 84% versus laryngeal mask airway 96%). The cuffed oropharyngeal airway required a higher number of airway interventions (P < 0.001). The laryngeal mask airway had a significantly better fibreoptic view compared with the cuffed oropharyngeal airway (P < 0.001). However, the number of adverse airway events was lower in the cuffed oropharyngeal airway group; there were no significant differences in adverse events and haemodynamic variables between the said two groups. Conclusions: The results suggest that the cuffed oropharyngeal airway was an effective alternative airway in spontaneously breathing patients during short procedures.

Severity of airway hyperreactivity associated with laryngeal mask airway removal: correlation with volatile anesthetic choice and depth of anesthesia

Study Objective: To compare the influence of anesthetic depth and choice of volatile anesthetic drug on the incidence and severity of airway hyperreactivity associated with Laryngeal Mask Airway™ (LMA) removal. Design: Randomized observer-blinded study. Setting: Ambulatory Surgical Center at a University Medical Center. Patients: 123 ASA physical status I and II children undergoing infraumbilical procedures. Interventions: Patients were randomly assigned to one of four treatment groups: Group 1 = anesthetic induction with halothane, maintenance with isoflurane, nitrous oxide (N 2O), and oxygen (O 2), LMA removed when child awakened; Group 2 =anesthetic induction and maintenance as in Group 1, LMA removed while child anesthetized with age adjusted 2 minimum alveolar concentration (MAC) end-tidal concentration of isoflurane; Group 3 = anesthetic induction and maintenance with sevoflurane, N 2O, and O 2, LMA removed when child awakened; Group 4 = anesthetic induction and maintenance as in Group 3, but LMA removed while child anesthetized with age-adjusted 2 MAC end-tidal concentration of sevoflurane. Measurements and Main Results: Severity of airway hyperreactivity was graded as mild, moderate, or severe. A significant difference was not found amongst the four groups with respect to mild and moderate airway hyperreactivity. Severe airway hyperreactivity leading to a critical event [partial or complete laryngospasm with oxygen saturation (SPO 2) < 85%] was only encountered in Group 1 patients (incidence 13%). Adverse airway events (SPO 2 < 90%, vomiting and bronchospasm) were also significantly higher in Group 1 ( p < 0.05). Isoflurane use was independently associated with significantly higher airway hyperreactivity when compared with sevoflurane (p < 0.05). Conclusions: Depth of anesthesia during LMA removal does not appear to affect the incidence or severity of airway hyperreactivity when sevoflurane is the maintenance anesthetic. However, awake LMA removal during isoflurane anesthesia results in a higher incidence of adverse airway events and carries the risk of severe airway hyperreactivity.