Positive pressure ventilation with the laryngeal mask airway in non-paralysed patients: comparison of sevoflurane and propofol maintenance techniques

Transcription

1 British Journal of Anaesthesia 1998; 80: Positive pressure ventilation with the laryngeal mask airway in non-paralysed patients: comparison of sevoflurane and propofol maintenance techniques C. KELLER, H. J. SPARR AND J. R. BRIMACOMBE Summary We have compared anaesthetic maintenance and emergence characteristics of propofol and sevoflurane with the laryngeal mask airway (LMA) at commonly used doses in 185 ASA I II patients, in a randomized, prospective study. Anaesthesia was induced with propofol mg kg 1 and fentanyl 1 3 g kg 1. Neuromuscular blocking agents were not used. All patients underwent positive pressure ventilation (PPV) with tidal volumes of 6 8 ml kg 1 to maintain normal end-tidal carbon dioxide concentration. Anaesthesia was maintained with 66% nitrous oxide in oxygen and infusion of propofol 6 or 8 mg kg 1 h 1, or 1% or end-tidal sevoflurane. There were no failed insertion attempts and adequate ventilation was achieved in all patients. During emergence, there was a greater incidence of excitatory phenomena with 1% and sevoflurane (95% confidence intervals (Cl) 4 19%) compared with propofol (95% Cl 0 4%). (95% Cl 37 71%) was associated with the greatest overall incidence of respiratory and haemodynamic problems. This was significantly higher compared with propofol (95% Cl 19 36%). Shorter times to LMA removal were observed with 1% and sevoflurane compared with propofol (P 0.000). Postoperative problems did not differ between groups. We conclude that propofol 6 and sevoflurane were suitable for maintenance of anaesthesia for musculoskeletal surgery in nonparalysed ASA I II patients undergoing PPV with the LMA. Emergence was more rapid with sevoflurane, but was associated with more excitatory phenomena. (Br. J. Anaesth. 1998; 80: ) Keywords: equipment, masks anaesthesia; ventilation, positive pressure; anaesthetics volatile, sevoflurane; anaesthetics i.v., propofol is becoming increasingly popular for maintenance of anaesthesia, particularly for ambulatory surgery, 1 and sevoflurane is an acceptable alternative. 4 Both agents allow rapid changes in anaesthetic depth, a favourable emergence profile and minimal postoperative morbidity. Studies have compared propofol with sevoflurane anaesthesia in paralysed patients with the trachea intubated, and shown them to be similar in terms of cardiorespiratory effects, emergence times and adverse events. 4 The laryngeal mask airway (LMA) has gained widespread acceptance as a general purpose airway, with usage rates of up to 30%. 5 Large scale studies (total patients) suggest it is safe and effective for spontaneous ventilation (8139 patients) and positive pressure ventilation (10 71 patients). 5 7 The LMA offers several advantages over the tracheal tube, including improved haemodynamic stability, reduced anaesthetic requirements for airway tolerance, lower frequency of coughing, improved oxygen saturation during emergence and less sore throat, 8 and does not require neuromuscular block. Although both propofol 9 and sevoflurane 10 have been used for maintenance of anaesthesia with the LMA, there have been no comparative studies evaluating their clinical efficacy. In this randomized study, we have compared maintenance and emergence characteristics of sevoflurane nitrous oxide with propofol nitrous oxide anaesthesia at commonly used doses in non-paralysed patients undergoing ventilation with the LMA. Patients and methods This study was approved by the Research and Ethics Committees of the University Hospital of Innsbruck and written informed consent was obtained from all patients. We studied 185 consecutive patients undergoing musculoskeletal surgery expected to last more than 30 min in the supine position, allocated randomly to one of four treatment groups. In groups I and II anaesthesia was maintained with 66% nitrous oxide in oxygen and infusion of propofol 6 or, respectively. In groups III and IV anaesthesia was maintained with 66% nitrous oxide in oxygen and either 1% or end-tidal sevoflurane, respectively. Sample size was based on the need to show a 0% difference in orientation time between groups, with a type I error of 0.05 and a power of 0.8. Patients were excluded if they were less than 19 or more than 65 yr of age, ASA III V, had a history of malignant hyperthermia, respiratory tract pathology, a sore throat within 10 days, known difficult airway, C. KELLER*, MD, H. J. SPARR, PHD, MD, Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University, 600, Innsbruck, Austria. J. BRIMACOMBE, MB, CHB, FRCA, MD, University of Queensland, Cairns Base Hospital, Cairns 4870, Australia. Accepted for publication: October 4, *Address for correspondence: Department of Anaesthesia and Intensive Care Medicine, Anichstrasse 35, 600, Innsbruck, Austria.

2 vs propofol with the laryngeal mask 333 body mass index greater than 30 kg m or were at risk of regurgitation/aspiration (previous upper gastrointestinal tract surgery, known or symptomatic hiatus hernia, oesophageal reflux, peptic ulceration or not fasted). Patients were allocated randomly to treatment groups by opening sealed envelopes, 1 h before operation. Anaesthesia was standardized. Premedication comprised midazolam 7.5 mg orally approximately 1 h before induction. Monitoring was started before induction of anaesthesia and included ECG, pulse oximetry, capnography and non-invasive arterial pressure. Oxygen was given by face mask and then fentanyl 1 3 g kg 1 was given followed 1 min later by propofol mg kg 1 over 30 s. Immediately before insertion, the LMA was lubricated with saline. No attempt was made to ventilate the patient s lungs via a face mask or to instrument the airway with suction catheters at any time during anaesthesia. The LMA was inserted 30 s after completion of the bolus dose of propofol using the standard recommended insertion technique, 11 with the cuff deflated and the rim facing posteriorly when the eyelash reflex was lost and the jaw relaxed. A size 3 LMA was used for patients weighing kg and a size 4 for patients more than 60 kg (size 5 LMA was unavailable during the study). Additional bolus doses of propofol 0.5 mg kg 1 were given as required until an adequate level of anaesthesia was achieved for placement. All LMA were inserted by a single experienced user (C. K.) (more than 800 previous placements). The cuff was initially inflated with 0 ml of air in the size 3 and 30 ml in the size 4. Successful placement was judged by chest wall movement and capnography during manually assisted ventilation. After successful placement, the LMA was fixed in place in the midline with the tube following its natural caudal curve using adhesive tape. 11 A wad of gauze swabs rolled into a cylindrical shape was placed alongside the LMA to function as a bite block. 11 Cuff pressures were monitored throughout the procedure using a calibrated aneroid manometer (Mallinckrodt Medical, Athlone, Ireland) which was attached to the pilot balloon. Cuff pressures were maintained at less than 60 cm H O by intermittently withdrawing gas from the cuff. Patients underwent positive pressure ventilation (PPV) with tidal volumes of 6 8 ml kg 1 and peak airway pressures were limited to 15 cm H O. Ventilatory frequency was adjusted to maintain end-tidal carbon dioxide in the normal range ( kpa). Anaesthesia was maintained with 66% nitrous oxide in oxygen and propofol 6 or, or or end-tidal sevoflurane. Airway gases were sampled from the proximal end of the LMA. A circle anaesthetic breathing system was used and there was no active humidification in the anaesthesia system. Fresh gas flows were litre min 1 of oxygen and 4 litre min 1 of nitrous oxide. Depth of anaesthesia was assessed by observing ventilatory frequency, patient movement, heart rate and arterial pressure and, if considered inadequate, fentanyl 1 g kg 1 was given. If coughing, retching or laryngospasm occurred, propofol 0.5 mg kg 1 was given. The maintenance dose of propofol or sevoflurane was continued until completion of surgery. Emergence took place in the operating room in the supine position with the patient undisturbed and breathing 100% oxygen. LMA removal time was determined by asking the patient in a normal tone of voice to open his or her eyes and mouth. This was repeated every s until both appropriate responses were obtained. The LMA and bite block were removed simultaneously and the time recorded. Orientation time was determined by asking the patient in a normal tone of voice to state his or her name and date of birth. This was repeated every s until a correct response was obtained and the time recorded. Patient data, including sex, age, weight, smoking history and duration of surgery were recorded for each patient. In addition to the standard anaesthetic record, mean arterial pressure (MAP) and heart rate (HR) were recorded before induction, every minute from induction to incision, every 5 min after incision, and every minute after anaesthesia was discontinued until the LMA was removed. Problems during induction and surgery were documented by the anaesthetist (C. K.) not blinded to the type of anaesthetic. Problems during emergence and in the postoperative period were recorded by an anaesthetist (H. S.) blinded to the type of anaesthetic. Problems were classified as respiratory, haemodynamic or excitatory phenomena. Respiratory problems included failed insertion attempt (failed placement within 0 s), failed ventilation (failure to maintain Pa CO within the normal range or Sp O 95% with FI O 33%), cough- ing, retching, hiccup, laryngospasm (a sudden increase in peak airway pressure greater than 5 cm H O), bronchospasm, regurgitation, aspiration, gastric insufflation (air heard entering the stomach on auscultation over the epigastrium), increased salivation, biting and any other untoward airway event. Haemodynamic problems included hypertension/ hypotension, tachycardia/bradycardia and other arrhythmias. Hypertension or hypotension was defined as MAP 0% of preinduction baseline values, respectively. Tachycardia or bradycardia was defined as heart rate greater that 100 beat min 1 or less than 60 beat min 1, respectively. Excitatory phenomena included inco-ordinate movement, shivering and straining. Successful induction, maintenance and emergence were defined as the absence of any respiratory or cardiovascular problems during that time. Anaesthesia was divided into three phases: induction (start of anaesthesia until successful placement of the LMA); maintenance (successful placement of the LMA until anaesthesia discontinued) and emergence (anaesthesia discontinued until patient orientated). Time intervals recorded included anaesthesia time (start of anaesthesia until anaesthesia discontinued), LMA removal time (anaesthesia discontinued until LMA removed) and orientation time (anaesthesia discontinued until patient orientated). Each patient underwent a structured interview (H. S.) 18 4 h after surgery during which they were asked about postoperative hoarseness (yes/no), nausea (yes/no) and vomiting (yes/no). Sore throat was graded by the patient as none (no sore throat at any time since the operation), mild (sore throat disappeared within 6 h), moderate (sore throat disappeared within 1 h) and severe (sore throat lasted 1 h or more). Data were analysed with the Student s t test and chi-square test using the software package SPSS

3 334 British Journal of Anaesthesia Table 1 Patient and anaesthetic characteristics in the four groups (mean (SD or range) or number) V Age (yr) 39 (19 64) 37 (0 60) 37 ( 61) 39 (19 63) Height (cm) 171 (9) 173 (9) 17 (9) 171 (9) Weight (kg) 69 (1) 71 (13) 70 (1) 7 (1) Body mass index (kg m ) 3 (3) 4 (3) 4 (3) 4 (3) Sex M/F (n) 6/1 8/0 4/1 5/0 ASA I/II (n) 40/7 38/10 40/5 38/7 Smoking history (n) Anaesthesia time (min) 48 () 53 (7) 51 (5) 54 (1) Min. to max. anaesthesia time (min) 30/90 30/110 35/10 35/105 Procedures (n) Knee Foot and ankle Hand and shoulder induction dose (mg kg 1 ) 3.0 (0.3) 3.0 (0.4) 3.0 (0.4) 3.0 (0.3) Fentanyl induction dose ( g kg 1 ) 1.8 (0.5) 1.9 (0.6) 1.9 (0.4) 1.9 (0.4) Additional intraoperative drugs (n) Fentanyl (1 g kg 1 ) (0.5 mg kg 1 ) Atropine (0.5 mg) Emergence times (min) LMA removal 8.0 (.4) 9.1 (.8) 6.1 (.4) 6.5 (.1) Orientation 14.5 (4.8) 15.3 (5.0) 9.7 (3.3) 9.1 (3.67) Table Respiratory, haemodynamic and postoperative problems during each phase of anaesthesia (number (%)) V Minimal S p O (%) Induction Hiccup 1 (%) (4%) 0 (0%) 0 (0%) Hypotension (4%) 1 (%) (4%) (4%) Bradycardia (4%) 1 (%) 1 (%) 1 (%) Maintenance Laryngospasm 0 (0%) 0 (0%) 4 (9%) 0 (0%) Hypotension 0 (0%) 3 (6%) 0 (0%) 1 (%) Hypertension (4%) 3 (6%) 4 (9%) 1 (%) Bradycardia 9 (19%) 10 (1%) 1 (7%) 10 (%) Emergence Cough 0 (0%) (4%) 4 (9%) 0 (0%) Retching 0 (0%) 0 (0%) 1 (%) 0 (0%) Increased salivation 1 (%) 0 (0%) 0 (0%) 0 (0%) Biting 4 (9%) 5 (10%) 7 (16%) 8 (18%) Hypertension 1 (%) 0 (0%) (4%) (4%) Excitement 0 (0%) 0 (0%) 4 (9%) 5 (11%) Postoperative Mild sore throat (4%) 1 (%) 1 (%) 1 (%) Hoarseness 0 (0%) 0 (0%) 0 (0%) 0 (0%) Nausea 1 (%) 0 (0%) 1 (%) 3 (7%) Vomiting 0 (0%) 0 (0%) 0 (0%) 1 (%) (version 6.0 for Windows, SPSS Inc., Chicago, IL, USA). Significance was taken as P Results There were no significant differences between the four groups in age, weight, height, body mass index, ASA status, sex distribution, smoking history, type of surgical procedure, anaesthesia time, administration of adjunctive drugs and induction doses of fentanyl and propofol (table 1). Problems occurring during the three phases of anaesthesia are given in table. There were no failed insertion attempts and adequate ventilation was achieved in all patients. The lowest oxygen saturation recorded during the study was 95%. There were no episodes of gastric distension, regurgitation, aspiration or bronchospasm. The incidence of problems at induction was similar in all groups. During maintenance, the incidence of laryngospasm and requirements for additional propofol were greater with 1% sevoflurane (95% confidence intervals (CI) 3%) compared with sevoflurane (95% CI 0 8%) or the propofol groups (95% CI 0 7%). During emergence, there was a greater incidence of excitatory phenomena with 1% and sevoflurane (95% CI 4 9%) compared with propofol (95% CI 0 4%). HR (fig. 1) and MAP (fig. ) for each group were similar during induction and maintenance of anaesthesia. There was no haemodynamic stress response to placement of the LMA. During emergence, HR was greater with sevoflurane at 3 7 min after discontinuation of anaesthesia (P 0.05). MAP was similar.

4 vs propofol with the laryngeal mask 335 there were no other significant differences between groups. Significantly shorter times to LMA removal and orientation were observed with 1% and sevoflurane compared with propofol 6 and 8 mg kg 1 h 1 (P 0.000). Removal and orientation times were similar for 1% sevoflurane compared with sevoflurane, and similar for propofol 6 and 8 mg kg 1 h 1. Postoperative problems did not differ between groups. The incidence of sore throat was.7% and hoarseness 0%. The number of patients who received postoperative analgesia was similar between groups. Figure 1 Heart rate (HR) before induction of anaesthesia, at the indicated times after induction, at skin incision, at the indicated times after skin incision, at the end of administration of anaesthesia and at the indicated times after anaesthesia in the four treatment groups (mean (SD)). HR was significantly greater with sevoflurane at 3 7 min after discontinuation of anaesthesia. Figure Mean arterial pressure (MAP) before induction of anaesthesia, at the indicated times after induction, at skin incision, at the indicated times after skin incision, at the end of administration of anaesthesia and at the indicated times after anaesthesia in the four treatment groups (mean (SD)). There were no significant differences between groups. The total number of patients with respiratory and haemodynamic problems during each phase of anaesthesia is given in table 3. (95% CI 37 71%) was associated with the greatest overall incidence of respiratory and haemodynamic problems. This was significantly higher compared with propofol (95% CI 19 36%), but Discussion Our data suggest that maintenance of anaesthesia with propofol 6 or sevoflurane in nitrous oxide provides satisfactory anaesthetic conditions in non-paralysed patients undergoing ventilation with an LMA. provided less satisfactory conditions and this was probably related to inadequate depth of anaesthesia. The overall incidence of problem-free maintenance and emergence was similar to that reported in paralysed patients whose tracheas were intubated, 3 but randomized controlled studies are required to determine if either technique offers an advantage. During induction and maintenance of anaesthesia, haemodynamic variables were similar. This contrasts with the results of Fredman and colleagues who showed slower heart rates in the immediate postinduction period in paralysed patients whose tracheas were intubated. The reason for this difference is not clear. During emergence, heart rate was greater with sevoflurane. MAP was similar in all groups during emergence. The high incidence of bradycardia in all groups may reflect the lack of cardiovascular stimulation resulting from the LMA. The efficacy of the LMA technique for PPV is already established, but most controlled studies involve paralysed patients Our data suggest that the technique is also suitable for non-paralysed patients. It is interesting that, despite cuff pressure limitation to 60 cm H O, in all patients ventilation was adequate using tidal volumes of 6 8 ml kg 1 and peak airway pressures of 15 cm H O. This may be related to the relatively low body mass index of the study population (BMI 30 kg m ) and accurate placement of the device. Dyer, Llewellyn and James have shown the LMA to be an effective device for PPV using total i.v. anaesthesia with propofol and easier to manage than the tracheal tube in the absence of neuromuscular blockers. 9 The times required for LMA removal and orientation were shorter with sevoflurane. These times Table 3 Incidence of respiratory and haemodynamic problems during each phase of anaesthesia (number (%)) V Induction 3 (6%) 3 (6%) (4%) (4%) Maintenance 10 (1%) 1 (5%) 16 (36%) 11 (4%) Emergence 5 (11%) 8 (17%) 13 (9%) 11 (4%) Total 14 (30%) 18 (37%) 5 (56%) 19 (4%)

5 336 British Journal of Anaesthesia were similar to those reported for sevoflurane and propofol in paralysed patients whose tracheas were intubated. 3 The highest incidence of nausea (7%) and vomiting (%) was in the sevoflurane group, but this was not significantly different from the other groups. The incidence of nausea and vomiting was 10 times less than previously reported for paralysed patients whose tracheas were intubated 3 and may reflect different methods of data collection, different types of surgery or antiemetic therapy. It would seem unlikely that this was related to the LMA as previous studies have reported a similar incidence of postoperative nausea and vomiting when comparing the LMA with the tracheal tube No routine intraoperative antiemetic was given in our study and there was no case of gastric insufflation. The incidence of sore throat with the LMA is approximately 10%, but varies between 0 and 50%, 18 3 and the incidence of hoarseness is approximately 4%. 1 4 The incidence of sore throat and hoarseness in our study was low (.7% and 0%, respectively). This probably reflects the high first time placement rate, use of standard insertion technique and adoption of low intra-cuff pressures. All LMA were inserted by an experienced user with more than 800 previous placements. It has been shown that there are short-term ( 75 uses) 5 and long-term ( 750 uses) 6 learning curves with the LMA. Burgard, Mollhoff and Prien demonstrated that reducing cuff pressure to the minimum required for an adequate seal produced a reduction in sore throat from 8 to 0%. The 13% incidence of biting during emergence highlights the importance of using a bite block with the LMA. We conclude that propofol 6 and end-tidal sevoflurane were suitable for maintenance of anaesthesia for musculoskeletal surgery in non-paralysed ASA I II patients undergoing PPV with the LMA. Emergence was more rapid with sevoflurane, but was associated with more excitatory phenomena and tachycardia. References 1. Smith I, White PF, Nathanson M, Gouidson R. : an update on its clinical uses. Anesthesiology 1994; 81: Fredman B, Nathanson MH, Smith I, Wang J, Klein K, White PF. for outpatient anesthesia: a comparison with propofol. Anesthesia and Analgesia 1995; 81: Jellish WS, Lien CA, Fontenot HJ, Hall R. The comparative effects of sevoflurane versus propofol in the induction and maintenance of anesthesia in adult patients. Anesthesia and Analgesia 1996; 8: Smith I, Ding Y, White PF. Comparison of induction, maintenance, and recovery characteristics of sevoflurane N O and propofol N O with propofol isoflurane N O anesthesia. Anesthesia and Analgesia 199; 74: Verghese C, Brimacombe J. Survey of laryngeal mask usage in patients safety and efficacy for conventional and nonconventional usage. Anesthesia and Analgesia 1996; 8: Brimacombe J. Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia. Anaesthesia 1996; 51: Van Damme E. Die Kehlkopfmaske in der ambulanten Anaesthesie-Eine Auswertung von 5000 ambulanten Narkosen. Anasthesiologie, Intensivmedizin, Notfallmedizin, Schmerztherapie 1994; 9: Brimacombe J. The advantages of the LMA over the tracheal tube or facemask: a meta-analysis. Canadian Journal of Anaesthesia 1995; 4: Dyer RA, Llewellyn RL, James MFM. Total i.v. anaesthesia with propofol and the laryngeal mask for orthopaedic surgery. British Journal of Anaesthesia 1995; 74: Taguchi M, Watanabe S, Asakura N, Inomata S. End-tidal sevoflurane concentrations for laryngeal mask airway insertion and for tracheal intubation in children. Anesthesiology 1994; 81: Brimacombe J, Brain AIJ, Berry A. The Laryngeal Mask Airway Instruction Manual. Henley-on-Thames: Intavent Research, Devitt JH, Wenstone R, Noel AG, O Donnell RRT. The laryngeal mask airway and positive-pressure ventilation. Anesthesiology 1994; 80: Graziotti PJ. Intermittent positive pressure ventilation through a laryngeal mask airway is a nasogastric tube useful? Anaesthesia 199; 47: Epstein RH. Maintenance of airway sealing pressures of the laryngeal mask airway in children. Anesthesiology 1994; 81: A Heinrichs W, Weiler N, Latorre F, Eberie B. Respiratory mechanics, gastric insufflation pressure and air leakage of the laryngeal mask airway. Anesthesiology 1995; 83: A Swann DG, Spens H, Edwards SA, Chestnut RJ. Anaesthesia for gynaecological laparoscopy a comparison between the laryngeal mask airway and tracheal intubation. Anaesthesia 1993; 48: Cork RC, Depa RM, Standen JR. Prospective comparison of use of the laryngeal mask and endotracheal tube for ambulatory surgery. Anesthesia and Analgesia 1994; 79: Brimacombe J, Berry A. Insertion of the laryngeal mask airway a prospective study of four techniques. Anaesthesia and Intensive Care 1993; 1: McCrirrick A, Ramage DT, Pracilio JA, Hickman JA. Experience with the laryngeal mask airway in two hundred patients. Anaesthesia and Intensive Care 1991; 19: Reddy SVG, Win N. Brain laryngeal mask study in 50 spontaneously breathing patients. Singapore Medical Journal 1990; 31: O Neill BL, Foley EP, Chang A. Effects of humidification of inspired gases with the laryngeal mask airway. Anesthesiology 1994; 81: A5.. Burgard G, Mollhoff T, Prien T. The effect of laryngeal mask cuff pressure on postoperative sore throat incidence. Journal of Clinical Anesthesia 1996; 8: Splinter WM, Smallman B, Rhine EJ, Komocar L. Postoperative sore throat in children and the laryngeal mask airway. Canadian Journal of Anaesthesia 1994; 41: Fujii Y, Tanaka H, Toyooka H. Effects of laryngeal mask airway on circulation and on incidence of postoperative sore throat and hoarseness. Masui 1993; 4: Lopez-Gil M, Brimacombe J, Cebrian J, Arranz J. The laryngeal mask airway in pediatric practice a prospective study of skill acquisition by resident anesthesiologists. Anesthesiology 1996; 84: