256

Clinical Experience Experience with the Laryngeal Mask Airway in Two Hundred Patients A. MCCRIRRICK,* D. T. O. RAMAGEt, J. A. PRACILIOt AND J. A. HICKMAN§ Department of Anaesthesia, Fremantle Hospital, Fremantle, Western Australia SUMMARY

Observations were recorded from two hundred consecutive insertions of the laryngeal mask airway (LMA). They were undertaken by 27 anaesthetists most of whom had no previous experience ofits use. A clinically patent airway was obtained in 94% ofpatients and in the majority of these (76%) the LMA was positioned correctly at the first attempt. There were twelve cases offailed insertion. Nine ofthese were as a result ofan inability to pass the LMA correctly into the hypopharynx while in the remaining three cases complete airway obstruction was reported. The insertion technique was easily acquired and trainee anaesthetists achieved a success rate of84%for their firstfive attempts. Success with the LMA was related to experience: anaesthetists who had used the LMA over 15 times had no failures in 67 insertions. Twenty-two patients coughed and six developed mild laryngospasm at insertion. The incidence of postoperative sore throat was 8%.

Key Words: ANAESTHESIA: laryngeal mask, difficult intubation, uvula trauma; COMPLICATIONS: laryngospasm, regurgitation

The laryngeal mask airway (LMA) is a relatively new type of airway designed to be passed into the hypopharynx without the aid of a laryngoscope I (Figure 1). It is commercially available in four sizes and is suitable for adult or paediatric use. The LMA may be used in preference to either facemask or endotracheal tube and will permit positive pressure ventilation to a maximum airway pressure of approximately 2 kPa. I ,2 Its use in the non-fasted patient or in patients who are otherwise at particular risk of aspiration of gastric contents is not recommended. 3,4 The LMA has been of value in cases of difficult intubation,5,6 emergency resuscitation 7 and in failed intubation at emergency caesarian section. 8 It has also been used as part of an awake intubation procedure (unpublished observations). In normal clinical practice the outstanding advantage of the LMA is its ability, once positioned, to maintain a patent airway without any further manual intervention from the anaesthetist. Previously this "F.C.Anaes., Senior Registrar. tF.C.Anaes., Senior Registrar. :j:F.F.A.R.A.C.S., Consultant Anaesthetist. §F.F.A.R.A.C.S., Director of Anaesthesia. Address for Reprints: Dr. A. McCrirrick, Department of Anaesthesia, Fremantle Hospital, P.O. Box 480, Fremantle, Western Australia 6160. Accepted for publication November 19, 1990

could only be achieved reliably by endotracheal intubation. There have been only two published independent assessments of the LMA in clinical practice. 9,10 The first of these studies, by Broderick et al., was undertaken using a single-sized prototype corresponding to a size three. 9 We present a study in which we examined the effectiveness and ease of insertion of the LMA when used by anaesthetists previously unfamiliar with it. METHOD Laryngeal mask airways (sizes three and four) were available to all grades of anaesthetists for use in adult patients presenting for routine elective surgery. Anaesthetists were encouraged to use the LMA whenever they considered it appropriate, but actual patient selection was left to the individual. The only exclusion criterion was a perceived incr~ase in the risk of aspiration of gastric contents. A training videotape on the use of the LMA, supplied by the manufacturer (lntavent Ltd, Theale, Reading, U.K.), was shown to all anaesthetists prior to the commencement of this study. No other formal education regarding insertion of the LMA was provided although all junior staff were closely supervised when using the device. Only two anaesthetists had had previous Anaesthesia and Intensive Care, Vol. 19, No. 2, May, 1991

CLINICAL EXPERIENCE

-

150

257

First Attempt

~ Second/Third Attempt

. i. c 0

D

Difficult

100 ~ Failure to Pass

D

.5

No Airway

'0 III .c

E

z"

50

FIGURE

Successful

Failed

Insertions

Insertions

2.-Successes and failures with the LMA. RESULTS

Observations were recorded from two hundred consecutive insertions of the LMA. It provided a clinically patent airway in 94% of all attempted insertions. Of these successful insertions 76.6% were achieved easily at the first attempt and 22.4% required either two or three attempts. The remaining two successful insertions required more than three attempts and were described as being FIGURE I.-The laryngeal mask airway. 'difficult'. These results are shown in Figure 2. There were twelve failed insertions. In nine of experience with the LMA. Premedication and these the LMA could not be passed correctly into anaesthetic technique were left to personal the hypopharynx. In the remaining three cases, preference. However, it should be noted that the although appearing to be in the correct position, the videotape clearly recommends propofol as the LMA did not provide a patent airway. The quality of the airway obtained in the induction agent of choice. Data was collected on a standard questionnaire successful cases were described as 'good' in 94% completed each time an LMA was used. and 'adequate' in the remainder (none was Anaesthetists identified only their grade and the classified as 'poor'). An LMA that required two or number of times they had previously used a three attempts to insert was as likely to provide a laryngeal mask. The ease of insertion of the LMA, good airway as one that was inserted first time. Twenty-seven out of twenty-eight anaesthetists the quality of the airway obtained, the type of ventilation (lPPV or spontaneous) and the in the department chose to use the LMA to varying induction agent used were all recorded. The TABLE I anaesthetist was asked which alternative method of Experience with the LMA by grade of anaesthetist airway management would have been employed in the absence of an LMA. Coughing or laryngospasm Mean No. of insertions at induction was recorded as was any documented Grade of anaesthetist (range in brackets) history of airway problems or difficulty with intubation. Consultants 5.0 ( 1-20) All patients were visited between 12 and 24 hours (n= 13) postoperatively except for day-case patients who Senior registrars 15.5 (3-22) were visited just prior to discharge. Any (n=4) postoperative complications which may have been Registrars/residents 7.3 (3-17) related to the LMA were noted and patients were (n= 10) specifically asked if they had a sore throat. Anaesthesia and Intensive Care. Vol. 19. No. 2. May. /99/

A. MCCRIRRICK ET AL.

258

extents. The LMA was used most by the senior registrars but some individual consultants also became very experienced in its use (Table 1). There was no statistical correlation between grade of anaesthetist and success with the LMA when comparing groups of equal experience (Table 2). Anaesthetists with experience of over fifteen insertions were clearly more successful than those with less. (P< 0.05 Chi-squared test with Yates' correction.) Propofol was used as the induction agent in all but one insertion. Eleven per cent of patients coughed and 3% developed mild laryngospasm (Table 3). Seventeen patients were ventilated with the Ohmeda 7000 ventilator and there were no reports of problems caused by excessive leaks at high airway pressures. In most cases (68.5%) the anaesthetist chose to remove the LMA in theatre. The remainder (31. 5%) were removed by recovery staff without apparent difficulty, following defined guidelines. Four per cent (eight patients) coughed markedly at removal. The LMA was inserted easily at the first attempt in four patients who had a documented history of difficult intubation. Anaesthetists stated that, had an LMA not been available, their alternative method of airway management would have been endotracheal intubation in 42% of cases. The two hundred cases described here represent 21 % of all the general anaesthetics administered by the department during the period of this study. The incidence of postoperative sore throat was 8% overall. This was described as mild in all but one case (Table 3). In one other patient significant oedema and bruising of the uvula was noted. The incidence and severity of postoperative sequelae to the upper airway did not appear to be related to the difficulty of insertion of the LMA. DISCUSSION

The LMA proved very successful and was liked by all grades of anaesthetist. It was generally easy to insert and in most cases provided a good airway at the first attempted insertion. The insertion

TABLE 3 The incidence of complications

11 %

Coughing at induction Laryngospasm Excessive coughing on removal Sore throat Uvula trauma

3% 4%

8% 0.5%

technique is straightforward and can be adopted by the inexperienced operator following minimal instruction. Trainees in their first year of anaesthetics achieved an overall success rate of 84% for their first five insertions. Initial inability to position the LMA correctly in those cases which required a second or third attempt was usually a result of an inadequate dose of induction agent. This occurred especially in unpremedicated patients and could usually be overcome by administering more propofol. The training videotape recording supplied by the manufacturers is useful in demonstrating the insertion technique, particularly in a department where no previous experience with the LMA exists. Broderick et al., in a previous study using only a size 3 LMA prototype, reported a 10% incidence of airway obstruction at initial insertion when the LMA had otherwise appeared to be correctly located. 9 The authors related this problem to downfolding of the epiglottis, necessitating the use of an introducer. In our study, of the twelve complete failures reported, only three were the result of airway obstruction. This represents an overall incidence of under 2%. Brain suggested that a low incidence of airway obstruction might be expected if propofol was used for induction 9 as was almost exclusively the case here. An alternative explanation is that using a size 4 LMA where appropriate may have helped prevent the epiglottis becoming downfolded over the laryngeal inlet. The LMA could not be passed into the hypopharynx without excessive force in the remaining nine failed cases. This was almost certainly due to inadequate depth of anaesthesia coupled with poor positioning

TABLE 2 Success and cumulative experience with the LMA

% of successes

Cumulative experience Fewer than 15 insertions

Consultants (n = 55) Senior registrars (n = 10) Registrars/residents (n = 68)

15 insertions or more

Consultants (n = 20) Senior registrars (n = 40) Registrars/residents (n = 7)

94%

90% 88%

100% 100% 100%

Anaesthesia and Intensive Care. Vol. 19. No. 2. May. 1991

CLINICAL EXPERIENCE

of the head. All cases of failed insertion occurred with anaesthetists who were relatively inexperienced with the LMA (Table 2). The LMA was used for one in five of all general anaesthetics administered during the period of study. As experience with the LMA increases this figure may be expected to increase significantly. The LMA offers some clear advantages over conventional techniques of airway management. Unlike a face mask and oropharyngeal airway, the LMA requires no manual support to maintain its position or to enable it to provide a patent airway. The anaesthetist's hands are free for note keeping and drug administration. The problem of the airway deteriorating because of the fatigue associated with manually maintaining the correct position of the jaw is eliminated. The LMA appears very suitable for patients in whom airway maintenance might be expected to be particularly difficult, such as the edentulous and those with awkward jaws. The LMA does not seem to be any more difficult to insert in these patients although further work is required to confirm this. The LMA may be used in place of endotracheal intubation in many elective cases. Insertion of the LMA does not require the use of muscle relaxants,2.ll is less invasive 1and may elicit a lesser haemodynamic response than intubation. 11,12 Insertion is also easier and quicker than intubation in patients in whom laryngoscopy is difficult. 5-7 The incidence of sore throat is certainly much lower than that associated with intubation 13-l5 and is similar to that recorded in non-intubated postsurgical patients. 14,15 Cronin et al. noted that 6% of all surgical patients found soreness of the throat the most unpleasant part of their recovery.16 Our experience suggests that the LMA may be removed by recovery staff without difficulty, although Wilkinson has documented one case of severe laryngeal stridor on removal. 17 Our study indicated that a significant number of patients (42%) would have been intubated had an LMA not been available. The LMA may be re-used and autoclaved up to one hundred times and, if used in place of disposable single-use endotracheal tubes, may represent a considerable financial saving. More detailed work on the financial implications of using the LMA is in progress. The incidence of coughing and laryngospasm was low (11 % and 3% respectively) but comparable with other studies. Dasey and Mansour advocated the routine use of a superior laryngeal nerve block to overcome this problem 18 but we would not consider this necessary in most instances. There were no reports of regurgitation of gastric contents during anaesthesia in our study. This is in contrast to the eight cases reported by Cyna and McLeod among Anaesthesia and Intensive Care. Vol. 19. No. 2. May, 1991

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546 fasted patients in whom the laryngeal mask was inserted. 4 The overall incidence of regurgitation with the LMA is unclear but may be less than the 5% incidence recorded by Blitt et al. in patients given general anaesthetic by facemask alone. 19 Turndorf et al. in 1974 reported similar figures. 20 The LMA remains contraindicated in non-fasted patients and patients otherwise at particular risk of regurgitation of gastric contents, We report one instance of significant trauma to the uvula. This has been documented on only one previous occasion 2l and was probably related to the application of undue force during an awkward insertion of the LMA. The bruising to the uvula subsided after 48 hours and there were no sequelae. CONCLUSION The LMA represents an important advance in airway management. It may be used in preference to either facemask or endotracheal tube and provides hands-free airway control through to the recovery room. The LMA is particularly suitable for minor, peripheral surgery to the limbs or face, especially in daycase surgery where intubation may be best avoided. The LMA cannot, however, always be considered a substitute for intubation, particularly as it may not protect against aspiration of gastric contents.

ACKNOWLEDGEMENTS We would like to thank Jane Wheatley and Margaret Cotter for their typing services and Or J. Watson for his help with the preparation of the manuscript. REFERENCES I. Brain AI1. The laryngeal mask -

2.

3. 4. 5. 6. 7.

8.

a new concept in airway management. Br J Anaesth 1983; 55:801-5. Brain AI1, McGhee TO, McAteer EJ, Abu Alsaad MAW, Thomas A, Bushman JA. The laryngeal mask airway. Development and preliminary trials of a new type of airway. Anaesthesia 1985; 40:356-61. Payne J. The use of the fibreoptic laryngoscope to confirm the position of the laryngeal mask. Anaesthesia 1989; 44:865. Cyna AM, MacLeod M. The laryngeal mask: cautionary tales. Anaesthesia 1990; 45:167. Brain AI1. The laryngeal mask airway - a possible new solution to airway problems in the emergency situation. Arch Emerg Med 1984; 1:229-32. Brain AI1. Three cases of difficult intubation overcome by the laryngeal mask airway. Anaesthesia 1985; 40:353-5. Calder I, Ordman AJ, Jackowski A, Crockard HA. The Brain laryngeal mask airway. An altemtive to emergency tracheal intubation. Anaesthesia 1990; 45: 137-9. McClune S, Regan M, Moore J. Laryngeal mask airway for caesarean section. Anaesthesia 1990; 45:227-8.

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9. Brodrick PM, Webster NR, Nunn JF. The laryngeal mask airway: A study of 100 patients during spontaneous breathing. Anaesthesia 1989; 44:238-41. 10. Maltby JR, Loken RG, Watson Ne. The laryngeal mask airway: clinical appraisal in 250 patients. Can Anaes Soc J 1990; 37:509-13. 11. Alexander CA, Leach AB, Thompson AR, Lister JB. Use your Brain! Anaesthesia 1988; 43:893-4. 12. Braude N, Clements EA, Hodges UM, Andrew BP. The pressor response and laryngeal mask insertion. A comparison with tracheal intubation. Anaesthesia 1989; 44:551-4. 13. Hartsell CJ, Stephen CR. Incidence of sore throat following endotracheal intubation. Can Anaesth Soc J 1964; 11:307-12. 14. Edmonds-Seal J, Eve NH. Minor sequelae of anaesthesia: a pilot study. Br J Anaesth 1962; 34:44-8.

15. Alexander CA, Leach AB. Incidence of sore throat with the laryngeal mask. Anaesthesia 1989; 44:791. 16. Cronin M, Redfem PA, UttingJE. Psychometry and postoperative complaints in surgical patients. Br J Anaesth 1973; 45:879-86. 17. Wilkinson PA. The laryngeal mask: cautionary tales. Anaesthesia 1990; 45:167. 18. Dasey N, Mansour N. Coughing and laryngospasm with the laryngeal mask. Anaesthesia 1989; 44:865. 19. Blitt CD, Gutman HL, Cohen DD, Weisman H, Dillon JB. 'Silent' regurgitation and aspiration during general anaesthesia. Anesth Analg 1970; 49:707-13. 20. Turndorf H, Rodis ID, Clark TS. 'Silent' regurgitation during anaesthesia. Anesth Analg 1974; 53:700-3. 21. Lee n. Laryngeal mask and trauma to uvula. Anaesthesia 1989; 44: 10 14.

Anaesthesia and Intensive Care, Vo!. 19, No. 2, May, 1991

Experience with the laryngeal mask airway in two hundred patients.

Observations were recorded from two hundred consecutive insertions of the laryngeal mask airway (LMA). They were undertaken by 27 anaesthetists most o...
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