910
Correspondence Airway obstruction and the laryngeal mask airway in paediatric radiotherapy
We note the understandable enthusiasm for the use of the laryngeal mask airway (LMA) in conjunction with inhalational anaesthesia for the treatment of chidren undergoing radiotherapy. Indeed, this has formed the basis of our technique for the past 3 years. However, we would like to highlight the airway problems that can occur, even with an apparently well-positioned LMA, when the patient is in the prone position with the head immobilised in a shell [I]. On 11 (3.5%) of the 313 occasions on which we have used this technique, serious airway obstruction has occurred, just after the patient had been positioned and thus at a time when the anaesthetist was still at hand to correct the obstruction. Five instances involved one child, in whom X ray eventually demonstrated marked kinking of the LMA in the oropharynx. In this child, the problem was solved by using an armoured LMA, which was on trial in the hospital. It is interesting to compare this with our previous technique, in which we used a Guedel-type airway, adapted for insufflation [2]. During 525 such anaesthetics, we encountered airway obstruction on 1 1 (2.1 YO)occasions. Overall, therefore, using the LMA has not reduced the
incidence of airway obstruction. However, in the Guedel airway group, two episodes of obstruction (detected by capnography) occurred during treatment, necessitating interruption of irradiation. This has not so far occurred using the LMA. Furthermore, it has proved much easier to undertake capnography with the LMA. We wish to emphasise that, even using the LMA, the airway is still at special risk in children anaesthetised in the prone position. We look forward to the general availability of the smaller sizes of armoured LMA, which we hope will further reduce the incidence of airway obstruction.
Department of Anaesthetics , Addenbrooke 's Hospital, Cambridge CB2 2QQ
M.J. HERRICK D.J. KENNEDY
References [ I ] WILSONIG, EASTLEY R. A modification of the laryngeal mask airway. Anesrhesiology 1991; 7 4 1157. [2] CASEY WF, PRICEV, SMITHHS.Anaesthesia and monitoring for paediatric radiotherapy. Journal of the Rqval Society of Medicine 1986; 7 9 4 5 4 6 .
Laryngomalacia-a specific indication for the laryngeal mask? A 5-month-old male infant was scheduled for laryngoscopy and bronchoscopy under general anaesthesia. He had presented with mild intermittent stridor but was otherwise healthy. There had been no apnoeic or cyanotic episodes and he had gained weight normally. Pre-operative examination was unremarkable except for a mild inspiratory stridor. Apropine 0.15 mg was given intramuscularly 1 h before anaesthesia. It was proposed to induce and maintain anaesthesia with spontaneous respiration of halothane in oxygen, to spray the vocal cords with local anaesthetic and then proceed to microlaryngoscopy and rigid bronchoscopy. On arrival in the anaesthetic room the child was alert and breathing normally with minimal stridor. Venous access was established and induction commenced with halothane in oxygen. However, as soon as consciousness was lost, the stridor worsened. It became difficult to deepen anaesthesia and the patient's oxygen saturation fell from 95 to 80%. A steady state of light anaesthesia was reached but with an oxygen saturation of only 75-80%. A Guedel airway was tolerated but did not improve the situation. Anaesthesia could not be deepended further, nor was it possible to demonstrate chest movement on gentle manual ventilation. At this stage it was considered expedient to abandon the plan to perform rigid endoscopy and instead undertake flexible endoscopy via a laryngeal mask airway. A size 2 laryngeal mask was inserted with immediate improvement in the airway. The stridor disappeared, the oxygen saturation increased to 98% and it became possible to demonstrate movement of the chest wall on manual ventilation. Anaesthesia was deepened easily and the
surgeon proceeded to insert a fibreoptic nasendoscope (Olympus E N F type P3) through the laryngeal mask. An excellent view was obtained and the classical features of laryngomalacia could be demonstrated. Recovery from anaesthesia was uneventful. This case illustrates the fact that infants with laryngomalacia can be difficult to anaesthetise. Severe cases are clearly a challenge, but even mild cases, such as our own, can cause problems. In our patient the use of the laryngeal mask was dramatically successful. It helped presumably by supporting the lax supraglottic tissues to prevent them from being drawn into the glottic opening. The laryngeal mask has been advocated for diagnostic flexible bronchoscopy in children [ 1, 21 because it provides a clear airway and allows dynamic assessment of the airway and vocal cord movement during lightening of anaesthesia. We would suggest that it is of specific value in cases where laryngomalacia is a possibility.
Royal Berkshire Hospital, Reading RGl 5AN
T.G.C. SMITH H. WHITTET T. HEYWORTH
References [I] WALKERRWM, MURRELL D. Yet another use for the laryngeal mask. Anaesthesia 1991; 46: 591. [2] MAEKAWA N, MIKAWAK, TANAKA 0, GOTOR, OBARA H. The laryngeal mask may be a useful device for fibreoptic airway endoscopy in pediatric anesthesia. Anesthesiology 1991; 7 5 169-70.
Spurious end-tidal CO, diagnosed by capnogram We wish to report an atypical capnogram noted during an elective cranioplasty in a 15-year-old girl. Anaesthesia was induced with propofol, fentanyl and atracurium. The lungs were ventilated with nitrous oxide 70% and isoflurane
0.5% in oxygen using a circle CO, absorber system driven
by a Manley Servovent ventilator. End-tidal CO, was measured from a connector attached to the tracheal tube using a Capnomac (Datex), a sidestream carbon dioxide
Correspondence Airway obstruction and the laryngeal mask airway in paediatric radiotherapy
We note the understandable enthusiasm for the use of the laryngeal mask airway (LMA) in conjunction with inhalational anaesthesia for the treatment of chidren undergoing radiotherapy. Indeed, this has formed the basis of our technique for the past 3 years. However, we would like to highlight the airway problems that can occur, even with an apparently well-positioned LMA, when the patient is in the prone position with the head immobilised in a shell [I]. On 11 (3.5%) of the 313 occasions on which we have used this technique, serious airway obstruction has occurred, just after the patient had been positioned and thus at a time when the anaesthetist was still at hand to correct the obstruction. Five instances involved one child, in whom X ray eventually demonstrated marked kinking of the LMA in the oropharynx. In this child, the problem was solved by using an armoured LMA, which was on trial in the hospital. It is interesting to compare this with our previous technique, in which we used a Guedel-type airway, adapted for insufflation [2]. During 525 such anaesthetics, we encountered airway obstruction on 1 1 (2.1 YO)occasions. Overall, therefore, using the LMA has not reduced the
incidence of airway obstruction. However, in the Guedel airway group, two episodes of obstruction (detected by capnography) occurred during treatment, necessitating interruption of irradiation. This has not so far occurred using the LMA. Furthermore, it has proved much easier to undertake capnography with the LMA. We wish to emphasise that, even using the LMA, the airway is still at special risk in children anaesthetised in the prone position. We look forward to the general availability of the smaller sizes of armoured LMA, which we hope will further reduce the incidence of airway obstruction.
Department of Anaesthetics , Addenbrooke 's Hospital, Cambridge CB2 2QQ
M.J. HERRICK D.J. KENNEDY
References [ I ] WILSONIG, EASTLEY R. A modification of the laryngeal mask airway. Anesrhesiology 1991; 7 4 1157. [2] CASEY WF, PRICEV, SMITHHS.Anaesthesia and monitoring for paediatric radiotherapy. Journal of the Rqval Society of Medicine 1986; 7 9 4 5 4 6 .
Laryngomalacia-a specific indication for the laryngeal mask? A 5-month-old male infant was scheduled for laryngoscopy and bronchoscopy under general anaesthesia. He had presented with mild intermittent stridor but was otherwise healthy. There had been no apnoeic or cyanotic episodes and he had gained weight normally. Pre-operative examination was unremarkable except for a mild inspiratory stridor. Apropine 0.15 mg was given intramuscularly 1 h before anaesthesia. It was proposed to induce and maintain anaesthesia with spontaneous respiration of halothane in oxygen, to spray the vocal cords with local anaesthetic and then proceed to microlaryngoscopy and rigid bronchoscopy. On arrival in the anaesthetic room the child was alert and breathing normally with minimal stridor. Venous access was established and induction commenced with halothane in oxygen. However, as soon as consciousness was lost, the stridor worsened. It became difficult to deepen anaesthesia and the patient's oxygen saturation fell from 95 to 80%. A steady state of light anaesthesia was reached but with an oxygen saturation of only 75-80%. A Guedel airway was tolerated but did not improve the situation. Anaesthesia could not be deepended further, nor was it possible to demonstrate chest movement on gentle manual ventilation. At this stage it was considered expedient to abandon the plan to perform rigid endoscopy and instead undertake flexible endoscopy via a laryngeal mask airway. A size 2 laryngeal mask was inserted with immediate improvement in the airway. The stridor disappeared, the oxygen saturation increased to 98% and it became possible to demonstrate movement of the chest wall on manual ventilation. Anaesthesia was deepened easily and the
surgeon proceeded to insert a fibreoptic nasendoscope (Olympus E N F type P3) through the laryngeal mask. An excellent view was obtained and the classical features of laryngomalacia could be demonstrated. Recovery from anaesthesia was uneventful. This case illustrates the fact that infants with laryngomalacia can be difficult to anaesthetise. Severe cases are clearly a challenge, but even mild cases, such as our own, can cause problems. In our patient the use of the laryngeal mask was dramatically successful. It helped presumably by supporting the lax supraglottic tissues to prevent them from being drawn into the glottic opening. The laryngeal mask has been advocated for diagnostic flexible bronchoscopy in children [ 1, 21 because it provides a clear airway and allows dynamic assessment of the airway and vocal cord movement during lightening of anaesthesia. We would suggest that it is of specific value in cases where laryngomalacia is a possibility.
Royal Berkshire Hospital, Reading RGl 5AN
T.G.C. SMITH H. WHITTET T. HEYWORTH
References [I] WALKERRWM, MURRELL D. Yet another use for the laryngeal mask. Anaesthesia 1991; 46: 591. [2] MAEKAWA N, MIKAWAK, TANAKA 0, GOTOR, OBARA H. The laryngeal mask may be a useful device for fibreoptic airway endoscopy in pediatric anesthesia. Anesthesiology 1991; 7 5 169-70.
Spurious end-tidal CO, diagnosed by capnogram We wish to report an atypical capnogram noted during an elective cranioplasty in a 15-year-old girl. Anaesthesia was induced with propofol, fentanyl and atracurium. The lungs were ventilated with nitrous oxide 70% and isoflurane
0.5% in oxygen using a circle CO, absorber system driven
by a Manley Servovent ventilator. End-tidal CO, was measured from a connector attached to the tracheal tube using a Capnomac (Datex), a sidestream carbon dioxide
