Waste gas exposure during desflurane and isoflurane anaesthesia

Background : Currently, there are no data available concerning the occupational exposure to desflurane during general anaesthesia. This prospective, randomized study reports on occupational exposure to desflurane, compared to isoflurane, in a modern operation theatre (OT).
Methods : The study was performed in an OT equipped with a modern air-conditioning system and with a low-leakage anaesthesia machine connected to a central scavenging system. Trace concentrations of the anaesthetics were measured continuously by means of a photoacoustic infrared spectrometer during general anaesthesia in 30 patients undergoing eye surgery. Values were obtained within the breathing zone of the anaesthetist, the surgeon, the auxiliary nurse and at the mouth of the patient.
Results : Desflurane and isoflurane were administered with median (range) endtidal concentrations of 4.7 (3.8–10.3) vol% and 0.9 (0.6–1.4) vol%, respectively. The personnel-related median values of the average trace concentrations of desflurane and isoflurane were 0.5 (0.01–7.5) ppm and 0.2 (0.01–1.6) ppm, respectively.
Conclusions : Occupational exposure to desflurane is low in the environment of a modern OT, even though it has to be administered in approximately 5-fold higher concentrations compared to isoflurane.     

Comparison of endtidal CO2 and arterial blood gas analysis in paediatric patients undergoing controlled ventilation with a laryngeal mask or a face mask

Endtidal CO2 (PECO2) and arterial blood gas tensions were compared between laryngeal mask (LMA) and face mask (FM) ventilation in paediatric outpatients. Following premedication with midazolam, anaesthesia was induced with either thiopentone or isoflurane and atracurium. Anaesthesia was maintained with N2O, O2 and isoflurane. Manually controlled ventilation was applied with a nonrebreathing system. Both PECO2 and arterial blood gas tensions were measured at 5 and 15 min after skin incision. The mean PaCO2 values in the LMA group were 36.6+/-7.4 and 37.5+/-6.4 mmHg and PaCO2 -PECO2 were 1. 8+/-2.4 and 2.5+/-3.3 mmHg, respectively. The mean PaCO2 values in the FM group were 41.3+/-8.1 and 43.4+/-8.9 mmHg; and PaCO2 -PECO2 were 5.3+/-3.6 and 8.8+/-7.0 mmHg, respectively. These values were lower in the LMA group (P< 0.05). We have concluded that monitoring of PECO2 is more reliable for estimating blood gas values during controlled ventilation with a LMA than a face mask.     

A study of airway management using the ProSeal LMA laryngeal mask airway compared with the tracheal tube on postoperative analgesia requirements following gynaecological laparoscopic surgery

In a randomised double blind prospective study, we tested the hypothesis that postoperative pain is lower in patients who receive an ProSeal LMA laryngeal mask airway compared with a tracheal tube. One hundred consecutive female patients (ASA I-II, 18-75 years) undergoing laparoscopic gynaecological surgery were divided into two equal-sized groups for airway management with the ProSeal LMA or tracheal tube. Anaesthesia management was identical for both groups and included induction of anaesthesia using propofol/fentanyl, and maintenance with propofol/remifentanil, muscle relaxation with rocuronium, positive pressure ventilation, gastric tube insertion, dexamethasone/tropisetron for anti-emetic prophylaxis, and diclofenac for pain prophylaxis. All types of postoperative pain were treated using intravenous patient-controlled analgesia (PCA) morphine. Patients and postoperative staff were unaware of the airway device used. Data were collected by a single blinded observer. We found that pain scores were lower for the ProSeal LMA at 2 h and 6 h but not at 24 h. Morphine requirements were lower for the ProSeal LMA by 30.4%, 30.6% and 23.3% at 2, 6 and 24 h, respectively. Nausea was less common with the ProSeal LMA than with the tracheal tube at 2 h and 6 h but not at 24 h. There were no differences in the frequency of vomiting, sore throat, dysphonia or dysphagia. We conclude that postoperative pain is lower for the ProSeal LMA than the tracheal tube in females undergoing gynaecological laparoscopic surgery.     

Intubation via LMA in pediatric patients with difficult airways

PURPOSE: To report two cases of successful tracheal intubation in difficult pediatric airways using a conventional laryngeal mask airway (LMA) with an extended polyvinyl chloride (PVC) tube after laryngeal assessment with a fibreoptic device. CLINICAL FEATURES: Two cases, Dandy-Walker and Pierre Robin syndromes, were scheduled for surgery. They were premedicated with 0.5 mg x kg(-1) promethazine p.o. 90 min before surgery. Both patients arrived in the operating room sedated, with dry mouth, and without evidence of increased intracranial tension or airway obstruction. Inhalational induction with isoflurane 0.5-3% was commenced. Conventional tracheal intubation was impossible in both cases. In each an LMA was inserted to maintain ventilation, anesthesia, and to facilitate intubation. Fibreoptic bronchoscopy was used to assess the larynx, followed by blind intubation via the LMA using extended PVC tracheal tube (TT). Anesthesia was maintained during intubation using Mapleson F anesthesia circuit attached to a connector with fibreoptic bronchoscope adapter. CONCLUSION: This report describes the assessment of the airway with fibreoptic bronchoscopy after LMA insertion facilitated blind tracheal intubation in two children with difficult airways.     

Total i.v. anaesthesia with propofol and the laryngeal mask for orthopaedic surgery

One hundred ASA I orthopaedic surgical patients (four randomizedgroups) were anaesthetized using continuous propofol and intermittentfentanyl (TIVA), with controlled ventilation via a trachealtube in groups 1 and 2, and a laryngeal mask airway (LMA) ingroups 3 and 4. Neuromuscular blockers were used in groups 1and 3 only. There were no significant differences between groupsin total anaesthetic requirements, as assessed by cardio vascularvariables and movement. Coughing interfered with surgery andmade controlled ventilation difficult to manage. In contrast,movement not associated with coughing did not impair surgeryor ventilation. Patients in group 2 (tracheal tube, no neuromuscularblocker) required more interventions for coughing than the othergroups, while patients in group 4 (LMA, no neuromuscular blocker)needed more boluses for movement than groups 1 and 3. Groups1 and 2 (tracheal tube) had significantly higher heart ratesand mean arterial pressures than groups 3 and 4 for varyingperiods up to 5 mm after insertion of the airway managementdevice. There was no correlation between mean arterial pressureand plasma concentrations of catecholamines related to insertionof either the tracheal tube or LMA. The LMA was found to bea highly effective device for controlled ventilation in TIVAand easier to manage than the tracheal tube in the absence ofneuromuscular blockers.     

Narkosegasbelastung des Personals in der Kinderanästhesie

Methods. To assess the occupational exposure of the anaesthetist to anaesthetic gases, a total of 1 German and 25 Swiss hospitals were investigated. A Brüel & Kjær Type 1302 multi-gas monitor was used to measure concentrations of nitrous oxide and halogenated anaesthetic agents in the anaesthetist's breathing zone. Measurements were performed during 114 general anaesthetic, 55 of which were in patients under 11 years of age. In these 55 patients, the influence of various factors on the exposure (time-weighted average concentrations) was estimated by comparing different data groups. The efficiency of the applied scavenging equipment was examined by surveying the exhalation valve with a leak detector (type TIF 5600, TIF Instruments, Miami). Results. Sessions with patients under 11 years of age revealed much higher anaesthetic gas exposures compared to older patients. The concentrations of nitrous oxide were on average threefold (Fig. 1), those of the halogenated anaesthetics fivefold higher (Fig. 2) for the younger patients. In 11- to 16-year-old patients the exposure level was the same as in adult patients. The measurements showed a reduction of 85% in exposure if an efficient scavenging system (i.e., no waste gas discharge to room air through the exhalation valve) or lower fresh gas flow were used (Fig. 4); 42% of the inspected scavengers were inefficient, and reduced the exposure on average by only 30%. In operating theatres with a ventilation rate of at least ten air changes per h, the measured concentrations of anaesthetic gases in the inhalation zone of the anaesthetists were reduced more than 50% compared to poorly ventilated rooms (Figs. 4 and 5). The use of tracheal intubation or laryngeal mask airway (LMA) anaesthesia resulted in a reduction of 80% in exposure compared to standard face masks if efficient scavenging was used. The exposures during sessions with inefficiently scavenged Bain coaxial systems or unscavenged semi-open delivery systems of the Jackson-Rees type were tenfold higher than with scavenged rebreathing circuit systems (Fig. 6). During anaesthesia with IV or double-mask induction, the average levels of inhalation anaesthetics were reduced by about 80% compared to inhalational induction with standard masks (Fig. 7). The anaesthetist's working technique is a very important factor that strongly influences the concentrations. Poor work practices, like lifting off the face mask with anaesthetic gas flow turned on, increased the exposure of the anaesthetist and other operating room personnel drastically, even if the other conditions (scavenger and room ventilation) were good. Discussion. The exposure levels of anaesthetic gases are generally higher during anaesthesia in children up to 10 years of age than in older patients. Nevertheless, the measurements showed that exposure during paediatric anaesthesia can be kept below the recommended limit (8-h TWA in Switzerland) of 100 ppm nitrous oxide and 5 ppm halothane or 10 ppm enflurane or isoflurane. Causes of high exposures were particularly high fresh gas flows often applied without scavenging or together with inefficient scavenging devices and the high part of mask anaesthesia and inhalation induction with a loosely held mask. To achieve an effective reduction of occupational exposure, well-adjusted and maintained scavenging systems and low-leakage work practices are of primary importance. As leakage can never be completely avoided, a ventilation rate of at least ten air changes per h should be maintained in operating rooms and rooms where anaesthesia is induced to keep down concentrations of waste anaesthetic gases. High exposure during mask anaesthesia and inhalation induction can be prevented by further measures. Using a LMA instead of a standard mask reduces the exposure to the same level as endotracheal intubation. The exposure during induction can be reduced remarkably by the use of the double-mask system or IV induction. Applying low fresh gas flows reduces not only the exposure concentrations in the theatres, but also the contribution to the environmental burden (`?greenhouse effect?' and ozone layer destruction).     

Use of the laryngeal mask for airway control in difficult intubations in children]

LMA was introduced in clinical practice by Arthur Brain in 1983 as a valuable substitute of tracheal tube in adult who underwent general anaesthesia; since then its applications have been extensively studied. LMA is a relatively new non-invasive ventilatory device which has allowed a radical change in the management of modern general anaesthesia. In this study, the application of LMA is assessed during induction and maintenance of general anaesthesia in children affected by severe facial deformities that could render the placement of the tracheal tube difficult. Three patients were affected by complex malformative syndromes involving the maxillo-facial skeleton and one patient presented a massive teratoma, originating from the orbit. In all these cases, LMA provided a patient airway and a satisfactory ventilation during both induction and the repeated attempts of inserting the tracheal tube; in one case, since the orotracheal intubation failed, LMA has proved to be as effective as the tracheal tube during the maintenance of general anaesthesia. Therefore, LMA is recommended as an essential ventilatory device in the hands of paediatric anaesthesiologists.     

Craniodiaphyseal dysplasia; another cause of difficult intubation

A nine-year-old boy with craniodiaphyseal dysplasia (CDD) presented for mandibular reduction. Patients with CDD present problems to the anaesthetist, specifically difficulties with airway management and tracheal intubation. This child was managed using laryngeal mask airway (LMA) guided fibreoptic intubation. Spontaneous respiration was maintained throughout intubation, following which ventilation was controlled and anaesthesia was provided using nitrous oxide, isoflurane and fentanyl. The perioperative management is described.     

Use of the laryngeal mask airway after oesophageal intubation

We have compared insertion of a tracheal tube and laryngealmask airway (LMA) both with and without the presence of a tubein the oesophagus in 20 ASA I and II patients undergoing electivelaparoscopy. After induction of anaesthesia and neuromuscularblock, we measured the times for an experienced anaesthetistto correctly position both an LMA and a tracheal tube with andwithout a tube in the oesophagus. The time to intubation wassignificantly less with the LMA than with the tracheal tube,both with and without an oesophageal tube in place (P<0.05).We conclude that if a tracheal tube is placed unintentionallyin the oesophagus, an LMA may be used subsequently to providerapid and effective oxygenation of the patient.     

Environmental monitoring of sevoflurane and nitrous oxide using the cuffed oropharyngeal airway

We compared exposure to sevoflurane (SEV) and nitrous oxide (N(2)O) during ventilation using the cuffed oropharyngeal airway (COPA) with waste gas exposure using a conventional face mask (FM) without any additional airways or face straps and with the laryngeal mask airway (LMA). Trace concentrations of SEV and N(2)O were assessed by using a direct reading spectrometer during 33 surgical procedures under general anesthesia. Measurements were made at the patients' mouths and in the anesthesiologists' breathing zones. Mean +/- SD concentrations of SEV and N(2)O measured at the patients' mouths were comparable in the COPA (SEV, 8.1 +/- 12.2 ppm; N(2)O, 213.3 +/- 289.2 ppm) and LMA (SEV, 18.5 +/- 25.8 ppm; N(2)O, 283.4 +/- 361.0 ppm) groups but differed significantly from the FM group (SEV, 46.5 +/- 19.6 ppm; N(2)O, 750.7 +/- 308.3 ppm). These values resulted in a comparable contamination of the anesthesiologists' breathing zones (SEV, 0.5 +/- 0.2 ppm; N(2)O, 5.7 +/- 4.8 ppm) for the COPA group, compared with the LMA group (SEV, 1.0 +/- 0.9 ppm; N(2)O, 12.2 +/- 14.3 ppm). This differed significantly from the FM group (SEV, 2.2 +/- 0.9 ppm; N(2)O, 37.5 +/- 14.3 ppm). We conclude that the use of the COPA during short surgical interventions has an occupational safety comparable to that of the LMA and that both resulted in less contamination through waste anesthetic gases. Therefore, the COPA may be a valuable alternative to the conventional FM. IMPLICATIONS: In this study, we have shown that the occupational exposure to waste anesthetic gases is comparable when using the cuffed oropharyngeal airway (COPA) and the laryngeal mask airway and is increased when using the face mask. Therefore, the COPA may be a valuable alternative to the conventional face mask during short surgical procedures.     

Surgeons' exposure to sevoflurane during paediatric adenoidectomy: a comparison of three airway devices

Although sevoflurane is commonly used in anaesthesia, a threshold value for maximum exposure to personnel does not exist and although anaesthetists are aware of the problem, surgeons rarely focus on it. We used a photo‐acoustic infrared device to measure the exposure of surgeons to sevoflurane during paediatric adenoidectomies. Sixty children were randomly allocated to laryngeal mask, cuffed tracheal tube or uncuffed tracheal tube. The average mean (maximum) sevoflurane concentrations within the surgeons' operating area were 1.05 (10.05) ppm in the laryngeal mask group, 0.33 (1.44) ppm in the cuffed tracheal tube group and 1.79 (18.02) ppm in the uncuffed tracheal tube group, (p < 0.001), laryngeal mask and cuffed tracheal tube groups vs. uncuffed tube group. The presence of sevoflurane was noticed by surgeons in 20% of cases but there were no differences between the groups (p = 0.193). Surgical and anaesthetic complications were similar in all three groups. We conclude that sevoflurane can be safely used during adenoidectomies with all three airway devices, but in order to minimise sevoflurane peak concentrations, cuffed tracheal tubes are preferred.     

Comparison of the anesthetic requirement for tolerance of laryngeal mask airway and endotracheal tube.

We tested the hypothesis that the laryngeal mask airway (LMA) is tolerated at lighter levels of anesthesia than an endotracheal tube (ET). We studied 20 unpremedicated, nonsmoking ASA physical status I or II patients aged 18-40 yr whose surgery lasted > 1 h. Subjects were randomly assigned to receive either an ET or LMA. Anesthesia was induced with intravenous propofol and the LMA or ET was inserted. The ET-group patients received 1.5 mg/kg of succinylcholine, preceded by vecuronium (0.015 mg/kg IV). Maintenance of anesthesia was with only isoflurane and approximately 66% N2O in O2 by spontaneous ventilation. All gas concentrations were measured by a Raman spectrometer sampling from the breathing circuit end of the LMA or ET. Toward the end of the procedure, the end-tidal N2O and isoflurane concentrations were allowed to decrease to < 3 vol% and 0.8 +/- 0.05 vol%, respectively. The end-tidal isoflurane concentration was then decreased in 0.1% +/- 0.05% decrements, each stable value being held for 5 min. The patient was observed for signs of reaction to the presence of the LMA or ET. The mean (range) end-tidal isoflurane concentrations for reaction to ET and LMA were 0.55% (0.4-0.7) and 0.35% (0.2-0.51), respectively (P < 0.001). These data confirm the original hypothesis of the study.     

The laryngeal mask airway in obstetrical anaesthesia

The laryngeal mask airway (LMA) has been used extensively to provide a safe airway in spontaneously breathing patients who are not at risk from aspiration of gastric contents. The role of the LMA in the event of a failed intubation in an obstetrical patient, and its place in a failed intubation drill remains unclear. Two hundred and fifty consultant obstetric anaesthetists in the United Kingdom were asked to complete an anonymous questionnaire regarding their views about using the laryngeal mask airway (LMA) in obstetrical anaesthesia. The LMA was available in 91.4% of obstetric units. Seventy-two per cent of anaesthetists were in favour of using the LMA to maintain oxygenation when tracheal intubation had failed and ventilation using a face mask was inadequate. Twenty-four respondents had had personal experience with the LMA in obstetrical anaesthesia, eight of whom stated that the LMA had proved to be a lifesaver. We believe that the LMA has a role in obstetrical anaesthesia when tracheal intubation has failed and ventilation using a face mask proves to be impossible, and it should be inserted before attempting cricothyroidectomy.     

Distal oesophageal pH measurement in children during general anaesthesia using the laryngeal mask airwayTM, tracheal tube and face mask

BACKGROUND: Distal oesophageal pH was measured during controlled ventilation in children with the laryngeal mask airway (LMATM), tracheal tube (TT) and face mask (FM). METHODS: Fifty-six children scheduled for inguinal surgery with a standardized general anaesthetic technique were randomly allocated to receive LMA (n=21), TT (n=18) or FM (n=19). A 14 Fr pH probe was placed into the distal oesophagus and pH values were measured over 1 min at 2-min intervals during the first 20 min of anaesthesia. RESULTS: The median values of pH were 4.4 (3.5-5.5), 4.2 (3.3-4.9), 4.1 (3.2-5.1), 4.1 (3.3-5.0), 4.0 (3.3-4.9), 4.0 (3.4-5.1); 4.2 (3.3-5.1), 4.2 (3.6-5.0), 4.2 (3.5-5.0), 4.2 (3.5-5.2), 4.2 (3.5-5.0), 4.1 (3.5-5.0) and 4.2 (3.6-5.0), 4.2 (3.8-5.8), 4.1 (2.8-5.2), 4.2 (3.3-5.1), 4.2 (3.4-5.1), 4.3 (3.4-5.1) for LMA, TT and FM groups, respectively. CONCLUSION: There was no difference in the median pH values, within and between the groups (P > 0.05). We conclude that there is no difference in gastro-oesophageal reflux, when using a LMA, TT or FM during controlled ventilation in anaesthetized children.     

RETRACTED ARTICLE: Circulatory responses to laryngeal mask airway insertion or tracheal intubation in normotensive and hypertensive patients

The effects of laryngeal mask airway (LMA) insertion and tracheal intubation on circulatory responses were studied in normotensive (n = 24) and hypertensive (n = 22) patients. In a randomized, double-blind manner, LMA insertion or tracheal intubation was performed after induction of anaesthesia with thiopentone and muscle relaxation with succinylcholine. In both normotensive and hypertensive patients, heart rate (HR), mean arterial pressure (MAP) and rate-pressure product increased after tracheal intubation or LMA insertion compared with base-line (P < 0.05). The haemodynamic changes were greater after intubation than after LMA insertion (P < 0.05). Following intubation of the trachea or insertion of the LMA, HR increased more markedly in hypertensive patients than in normotensive patients (P < 0.05). Plasma adrenaline and noradrenaline concentrations after tracheal intubation or LMA insertion increased compared with baseline values (P < 0.05) in normotensive and hypertensive patients. The increase in noradrenaline concentration after tracheal intubation was greater than that after LMA insertion (P < 0.05). No patient revealed ECG evidence of myocardial ischaemia. We conclude that insertion of LMA is associated with less circulatory responses than tracheal intubation in both normotensive and hypertensive patients.     

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.     

A prospective randomised controlled trial of the LMA Supreme vs cuffed tracheal tube as the airway device during percutaneous tracheostomy

We studied the performance of the LMA Supreme against a cuffed tracheal tube, our standard method of airway control during percutaneous tracheostomy, in 50 consecutive patients from three general critical care units. The primary outcome measure was adequacy of ventilation calculated as the difference in arterial carbon dioxide tension before and after tracheostomy. On an intention‐to‐treat analysis, there was no difference in the increase in arterial carbon dioxide tension between groups, with a median (IQR [range]) for the LMA Supreme of 0.9 (0.3–1.6 [0–2.8]) kPa, and for the tracheal tube of 0.8 (0.4–1.2 [0–2.5]) kPa, p = 0.82. Eight patients out of 25 (32%) crossed over from the LMA Supreme group to the tracheal tube group before commencement of tracheostomy due to airway or ventilation problems, compared with none out of 25 in the tracheal tube group, p = 0.01, and tracheostomy was postponed in two patients in the LMA Supreme group due to poor oxygenation. There were more clinically important complications in the LMA Supreme group compared with the tracheal tube group.     

Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia Waste gas exposure during paediatric anaesthesia

We report the findings of a study on exposure of operating room staff to sevoflurane, halothane and nitrous oxide during induction and maintenance of anaesthesia in children. Concentrations of anaesthetic agents in the operating theatre were measured directly by highly sensitive, photoacoustic infrared spectrometer during 20 anaesthetics. Samples were taken from the breathing zones of the anaesthetist and the circulating nurse. The operating theatre was of modern design with an air conditioning system providing 20 changes of air each hour. The threshold values of 100 ppm N₂O, 50 ppm isoflurane and 10 ppm halothane recommended by the United Kingdom Committee for Occupational Safety and Health (COSH) were exceeded in several cases for a short time during mask induction. After tracheal intubation, trace concentrations of sevoflurane, halothane and N₂O were mostly under the recommended levels and comparable to levels measured during adult anaesthesia.     

Laryngeal mask airway and uncuffed tracheal tubes are equally effective for low flow or closed system anaesthesia in children

Low flow and closed system anaesthesia have considerable advantages in economy, limited atmospheric pollution, and maintenance of humidification and temperature. To benefit from these techniques leakage from the breathing system should be as low as possible. The sealing of the airway is crucial to ensure this. Therefore, we have investigated in 30 children, aged 2-6 yr, the effectiveness of the laryngeal mask airway (LMA) and the uncuffed tracheal tube (TT) for closed system paediatric anaesthesia, during positive pressure ventilation, in a prospective, randomized study. Ventilation was adequate in all cases with both devices. Loss of gas from the breathing system was less than 100 ml min-1 in 13 (87%) patients in the LMA and in 12 (80%) patients in the TT group, with a maximum of approximately 700 ml min-1 in the TT and approximately 350 ml min-1 in the LMA group. We conclude that the airway sealing with both devices was tight enough to perform low flow or closed system anaesthesia in paediatric patients aged 2-6 yr.      

The pressor response after laryngeal mask or cuffed oropharyngeal airway insertion

BACKGROUND: Since the cuffed oropharyngeal airway (COPA) has been suggested to cause less pharyngeal trauma than the laryngeal mask airway (LMA), we conducted a prospective, randomised study to compare haemodynamic changes after placing either the COPA or LMA in healthy anaesthetised adults. METHODS: After standard midazolam premedication (0.05 mg kg(-1) IV), general anaesthesia (IV propofol 2 mg kg(-1)) was induced in 60 ASA physical status I-II, 18-65-yr-old patients, who were randomly allocated to receive COPA (n=30) or LMA (n= 30) placement and then mechanically ventilated using a 60% nitrous oxide and 1% isoflurane in oxygen mixture (TV=8 ml kg(-1), RR=12 b.p.m., I/E=1/2). Haemodynamic variables were recorded 20 min after the midazolam premedication (baseline), and then every 1 min until 10 min after general anaesthesia induction. RESULTS: Nine patients of group COPA (30%) required chin lift, jaw thrust or head tilt to maintain adequate ventilation, while no problems were observed in the LMA group (P<0.0005); however, in no case did the designed extratracheal airway have to be removed due to unsuccessful mechanical ventilation, and no signs of gastric insufflation or regurgitation were reported. The maximum mean changes in haemodynamic variables were more marked after LMA placement (SAP: 12%+/-13%; DAP: 11%+/-18%; HR: 13%+/-16%) than COPA placement (SAP: -3%+/-18%; DAP: -5%+/-16%; HR: 4%+/-13%) (P<0.005, P<0.005, and P<0.01 for SAP, DAP and HR, respectively). Group LMA showed higher SAP and DAP values than group COPA only during the first 3 min after airway insertion. CONCLUSION: In healthy, anaesthetised patients, placing a cuffed oropharyngeal airway is associated with smaller cardiovascular changes after airway insertion compared with the laryngeal mask airway.