Deep or awake removal of laryngeal mask airway in children at risk of respiratory adverse events undergoing tonsillectomy-a randomised controlled trial.

BACKGROUND: Laryngeal mask airways (LMA) are widely used during tonsillectomies. Contrasting evidence exists regarding the timing of the removal and the risk of perioperative respiratory adverse events. We assessed whether the likelihood of perioperative respiratory adverse events is influenced by the timing of LMA removal in children with at least one risk factor for these events. METHODS: Participants (n=290, 0-16 yr) were randomised to have their LMA removed either deep (in theatre by anaesthetist at end-tidal sevoflurane >1 minimum alveolar concentration) or awake (in theatre by anaesthetist or in postanaesthesia care unit by anaesthetist or trained nurse). The primary outcome was the occurrence of perioperative respiratory adverse events over the whole emergence and postanaesthesia care unit phases of anaesthesia. The secondary outcome was the occurrence of perioperative respiratory adverse events over the distinct phases of emergence and postanaesthesia care unit. RESULTS: Data from 283 participants were analysed. PRIMARY OUTCOME: even though a higher occurrence of adverse events was observed in the awake group, no evidence for a difference was found [45% vs 35%, odds ratio (OR): 1.5, 95% confidence interval (CI): 0.9-2.5, P=0.09]. Secondary outcome: there was no evidence for a difference between the groups during emergence [19 (14%) deep vs 25 (18%) awake, OR: 0.74, 95%CI: 0.39-1.42, P=0.37]. However, in the postanaesthesia care unit, children with an awake rather than deep removal experienced significantly more adverse events [55 (39%) vs 37 (26%); OR: 1.85, 95%CI: 1.12-3.07, P=0.02]. CONCLUSION: We found no evidence for a difference in the timing of the LMA removal on the incidence of respiratory adverse events over the whole emergence and postanaesthesia care unit phases. However, in the postanaesthesia care unit solely, awake removal was associated with significantly more respiratory adverse events than deep removal. TRIAL REGISTRATION NUMBER: ACTRN12609000387224 (www.anzctr.org.au).

Cuffed vs. uncuffed tracheal tubes in children: a randomised controlled trial comparing leak, tidal volume and complications.

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0-16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time-points: during volume-controlled ventilation 6 ml.kg-1 , PEEP 5 cmH2 O and during pressure-controlled ventilation 10 cmH2 O / PEEP 5 cmH2 O. The pressure-controlled ventilation measurement time-points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume-controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg-1 , median (IQR [range]) 0.20 (0.13-0.39 [0.04-0.60]) vs. 0.82 (0.58-1.38 [0.24-4.85]), respectively, p < 0.001. With pressure-controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30-min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30-min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short-term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long-term follow-up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

Premedication with salbutamol prior to surgery does not decrease the risk of perioperative respiratory adverse events in school-aged children.

BACKGROUND: Perioperative respiratory adverse events (PRAE) remain the leading cause of morbidity and mortality in the paediatric population. This double-blinded randomized control trial investigated whether inhaled salbutamol premedication decreased the occurrence of PRAE in children identified as being at high risk of PRAE. METHODS: Children with at least two parentally reported risk factors for PRAE undergoing elective surgery were eligible for recruitment. They were randomized to receive either salbutamol (200 µg) or placebo prior to their surgery and PRAE (bronchospasm, laryngospasm, airway obstruction, desaturation, coughing and stridor) were recorded. RESULTS: Out of 470 children (6-16 yr, 277 males, 59%) recruited, 462 were available for an intention-to-treat analysis. Thirty-two (14%) and 27 (12%) children from the placebo and salbutamol groups experienced PRAE. This difference was not significant [odds ratio (OR): 0.83, 95% confidence interval (CI): 0.48-1.44, P : 0.51]. Oxygen desaturation [14/232 (6%) vs 14/230 (6%), OR: 1.01, 95% CI: 0.47-2.17, P : 0.98] and severe coughing [12/232 (5%) vs 10/230 (4%), OR: 0.83, 95% CI: 0.35-1.97, P : 0.68] were the most common PRAE, but did not significantly differ between the groups. The occurrence of PRAE was slightly lower in children with respiratory symptoms who received salbutamol compared with placebo [16/134 (12%) vs 21/142 (15%), OR: 0.93, 95% CI: 0.38-2.26, P : 0.87], but was not significantly different. CONCLUSIONS: Premedication with salbutamol to children aged between 6 and 16 years and at high risk of PRAE prior to their surgery did not reduce their risk of PRAE. TRIAL REGISTRATION NUMBER: ACTRN12612000626864 ( www.anzctr.org.au ).

Prediction of peri-operative adverse respiratory events in children: the role of exhaled nitric oxide.

Increased levels of exhaled nitric oxide (eNO) may be a more objective predictor in identifying children at higher risk of peri-operative adverse respiratory events than the presence of risk factors such as recent cold or wheeze. Children with either none or ≥ 2 risk factors had eNO measured before surgery and any peri-operative adverse respiratory events were recorded. We found that an elevated eNO level was only predictive of adverse respiratory events in children with ≥ 2 risk factors (OR 2.96 (95% CI 1.48-5.93), p = 0.002). The presence of risk factors had a better predictive capability than a raised eNO level (OR 3.83 (95% CI 1.85-7.95), p < 0.001). The combination of both predictors did not improve the predictive capability for adverse respiratory events (OR 1.93 (95% CI 1.44-2.59), p < 0.001). We conclude that measuring eNO levels does not lead to improved prediction of adverse respiratory events and that, in routine clinical practice, an accurate history of risk factors remains the most appropriate tool for successfully identifying children at risk of peri-operative adverse respiratory events.

Peri-operative adverse respiratory events in children.

Three quarters of all critical incidents and a third of all peri-operative cardiac arrests in paediatric anaesthesia are caused by adverse respiratory events. We screened for risk factors from children's and their families' histories, and assessed the usefulness of common markers of allergic sensitisation of the airway as surrogates for airway inflammation and increased risk for adverse respiratory events. One hundred children aged up to 16 years with two or more risk factors undergoing elective surgery were included in the study. Eosinophil counts, IgE level, specific IgE for D. pteronyssinus, cat epithelia and Gx2 (grass pollen) were measured for each child and adverse respiratory events (bronchospasm, laryngospasm, oxygen desaturation < 95%, severe persistent coughing, airway obstruction and postoperative stridor) were recorded. Twenty-one patients had an adverse respiratory event but allergic markers were poor predictors. Binary logistic regression showed a lack of predictive value of the eosinophil range and adverse respiratory events (p = 0.249). Receiver operating characteristic (ROC) curves for the presence of adverse respiratory events vs level of specific IgE antibody (to Gx2 (AUC 0.614), cat epithelia (0.564) and D. pteronyssinus (0.520)) demonstrated poor predictive values. However, the presence of risk factors was strongly associated with adverse respiratory events (p < 0.001) and a ROC-curve analysis indicated a fair capacity to predict adverse respiratory events (AUC 0.788). There was a significant difference (p = 0.001) between the presence of adverse respiratory events in patients with more than four (p = 0.006), compared with less than four (p = 0.001), risk factors. We conclude that while risk factors taken from the child's (or family) history proved good predictors of adverse respiratory events, immunological markers of allergic sensitisation demonstrated low predictive values. Pre-operative identification of children at high risk for an adverse respiratory event should rely on clinical, rather than immunological, assessment.

Difficult airway equipment: a survey of standards across metropolitan Perth.

The importance of appropriate equipment to manage the difficult airway has been highlighted by the publication of the Australian and New Zealand College of Anaesthetists (ANZCA) guidelines in 2012. We set out to audit compliance with these guidelines in all public and private sites providing general anaesthesia in metropolitan Perth. Public and private health care websites identified 39 sites of which 37 were studied. Institutional and ethics approval was obtained. A tick-box design audit tool, based on the ANZCA guidelines, was used to collect information regarding the dedicated difficult airway container (DDAC) at each site. As recommended in the guidelines, only equipment within the DDAC was considered. Further data about each site, including the number of theatre suites, satellite anaesthetic areas, use of capnography and categories of patients treated (adult, obstetric and paediatric) were collected. An adult DDAC was found at 92% of all sites, but none of the sites had all the essential equipment listed in the ANZCA guidelines. There was limited provision of adult difficult airway equipment within private sites compared to public, and less provision of paediatric difficult airway equipment across all sites treating paediatric patients in metropolitan Perth. Capnography was available in 76% of post anaesthesia care units and used regularly in 27%. Adherence to the ANZCA guidelines regarding the DDAC could be improved. Standardised equipment across a metropolitan region would be of value in the management of the difficult airway.

An optical fiber-based gating device for prospective mouse cardiac MRI.

Prospective synchronization of MRI acquisitions on living organisms involves the monitoring of respiratory and heart motions. The electrocardiogram (ECG) signal is conventionally used to measure the cardiac cycle. However, in some circumstances, obtaining an uncorrupted ECG signal recorded on small animals with radio frequency (RF) pulses and gradient switching is challenging. To monitor respiratory motion, an air cushion associated with a pressure sensor is commonly used but the system suffers from bulkiness. For many applications, the physiological gating information can also be derived from an MR navigated signal. However, a compact device that can simultaneously provide respiratory and cardiac information, for both prospective gating and physiological monitoring, is desirable. This is particularly valid since small volume coils or dedicated cardiac RF coil arrays placed directly against the chest wall are required to maximize measurement sensitivity. An optic-based device designed to synchronize MRI acquisitions on small animal's respiratory and heart motion was developed using a transmit-receive pair of optical fibers. The suitability of the developed device was assessed on mice ( n = 10) and was based on two sets of experiments with dual cardiac and respiratory synchronization. Images acquired with prospective triggering using the optical-based signal, ECG, and the pressure sensor during the same experiment were compared between themselves in the first set. The second set compared prospective technique using optical-based device and ECG to a retrospective technique. The optical signal that was correlated to both respiratory and heart motion was totally unaffected by radiofrequency pulses or currents induced by the magnetic field gradients used for imaging. Mice heart MR images depict low-visible motion artifacts with all sensors or techniques used. No significant SNR differences were found between each series of image. Full fiber-optic-based signal derived from heart and respiratory motion was suitable for prospective triggering of heart MR imaging. The fiber optic device performed similarly to the ECG and air pressure sensors, while providing an advantage for imaging with dedicated cardiac array coils by reducing bulk. It can be an attractive alternative for small animal MRI in difficult environments such as limited space and strong gradient switching.