|Year : 2008 | Volume
| Issue : 6 | Page : 813
Use of Classic Laryngeal Mask Airway Inserted in Prone Position for Controlled Ventilation: A Feasibility Study
Vijay Kumar1, K Lalitha1, Talib Lone2
1 Senior Consultant, Department of Anaesthesiology and Critical Care, Indraprastha Apollo Hospital, Sarita Vihar, New Delhi 110076, India
2 P.G.Student, Department of Anaesthesiology and Critical Care, Indraprastha Apollo Hospital, Sarita Vihar, New Delhi 110076, India
|Date of Acceptance||18-Aug-2008|
|Date of Web Publication||19-Mar-2010|
Department of Anaesthesiology and Critical Care, Indraprastha Apollo Hospital, Sarita Vihar, New Delhi 110076
Source of Support: None, Conflict of Interest: None
Traditionally, general anaesthesia for surgical procedures requiring prone position consists of induction and tracheal intubation in supine position on a trolley, and then patient is turned prone on the operation table and positioned carefully. Even though this approach is familiar to most anaesthesiologists, it is time consuming and requires shift of manpower from other tasks to properly position the patient.
In the present study as an alternative to the traditional approach, classic laryngeal mask airway has been used successfully in patients who need controlled ventilation during short, moderate and even long duration surgeries in prone position. In this feasibility study involving 100 patients it was found that insertion of laryngeal mask airway in prone position, considerably simplify the management of this group of patients, without compromising the safety.
Keywords: Laryngeal mask airway, Prone position, Controlled ventilation, Elective surgery, Muscle relaxant
|How to cite this article:|
Kumar V, Lalitha K, Lone T. Use of Classic Laryngeal Mask Airway Inserted in Prone Position for Controlled Ventilation: A Feasibility Study. Indian J Anaesth 2008;52:813
|How to cite this URL:|
Kumar V, Lalitha K, Lone T. Use of Classic Laryngeal Mask Airway Inserted in Prone Position for Controlled Ventilation: A Feasibility Study. Indian J Anaesth [serial online] 2008 [cited 2020 Apr 6];52:813. Available from: http://www.ijaweb.org/text.asp?2008/52/6/813/60693
| Introduction|| |
The prone position is commonly used to provide surgical access to variety of surgeries including microdiscectomy, varicose vein avulsions, excision of pilonidal sinus etc. Conventionally, the patients are anaesthetized in the supine position on a trolley and after tracheal intubation using non-kinking reinforced endotracheal tube, they are turned over to prone position on operation table. Even though this method is familiar to most anaesthesiologists, this is an invasive procedure that may sometimes be unnecessary for short surgical procedures and is not without its own inherent risk of intubation. Operations performed in the prone position may be potential cause of delay in surgery schedules in busy operation theaters and may necessitate a shift of manpower from other tasks to properly position the patient. This becomes especially important if patients are obese. Alternative to this technique is inducing patient in prone position and inserting laryngeal mask airway (LMA). Laryngeal mask airway is less invasive than endotracheal intubation. Also, there is less chance of peripheral nerve damage as patients can take comfortable position themselves before induction of anaesthesia. Previous studies have used LMA in prone position during several surgical procedures ,, however use of intermittent positive pressure ventilation (IPPV) and LMA has not been reported. Hence, this study was done to see how feasible was it to use classic LMA for controlled ventilation in patients whom the anaesthesia is induced and maintained in prone position.
| Methods|| |
After proper approval from the hospital ethics committee and explaining to the patients this study was conducted in 100 consenting adult patients of ASA physical status I and II who required general anaesthesia in the prone position. All the patients were scheduled for elective surgery in which the use of laryngeal mask airway was deemed appropriate. Patients with suspected difficult airway, poor dentition, skeletal diseases and history of gastro esophageal reflux were excluded from the study.
After securing a venous access the patients were asked to position themselves comfortably in the prone position with the head turned laterally at a comfortable angle on a soft pillow. Pillows were put under the thorax and the pelvis to allow adequate movement of anterior abdominal wall during ventilation. Both arms were abducted and extended above the patients head. All prospective pressure points were adequately protected using cotton or gel protective padding. While patient was comfortable, standard monitors were applied. [Figure 1]
Haemodynamic and ventilatory variables were continuously monitored during the procedure and recorded at every five minutes interval. Pre-oxygenation with oxygen at 6 liters per minute by a loosely applied facemask was done until SpO2 became 100% and then anaesthesia was induced intravenously with fentanyl 1 mcg.kg -1 and Propofol 2-3 mg.kg -1 . After loss of consciousness, facemask was applied firmly allowing manual ventilation of lungs with 100% oxygen [Figure 2]. Then the head was extended by operating department assistant holding it with both hands and mouth opened by pulling the tip of patient's chin by anaesthetist and LMA was inserted as shown in [Figure 3] with its cuff in deflated position. Size of LMA was selected according to the patient weight and manufacturer's recommendation. The longitudinal black line present on the classic LMA was always kept facing towards the tip of patient's nose. As the LMA passed the incisors, the patient's chin was released, allowing the tongue to fall forwards, thereby opening up the posterior oropharyngeal space for the LMA. After inflation of the cuff the patient head was carefully laid to the left or right on to the soft pillow. Muscle relaxant atracurium was given only after confirming the position of LMA by checking the adequacy of manual ventilation for no obstruction and then properly fixing it to the patients face [Figure 4]. At this stage and throughout the whole perioperative period it was made sure that the longitudinal black line present on LMA was facing towards patient's nose to avoid any rotation of LMA inside mouth and consequently producing any gas leak during IPPV. All patients were mechanically ventilated and anaesthesia was maintained with nitrous oxide and isoflurane in oxygen. Morphine and atracurium supplements were administered for adequate pain relief and muscle relaxation. At the end of procedure muscle relaxation was reversed with neostigmine and glycopyrrolate mixture and patients were transferred to recovery bed in supine position. Patients had their spontaneous ventilation restored and LMA was taken out once they were awake.
All LMAs were inserted by two of the authors (Sr.Consultant grade) having experience of using LMA of more than 18 years each.
Demographic data, haemodynamic, ventilatory, anaesthetic variables and recovery characteristics were recorded. Problems encountered before induction, at induction, during the maintenance period and recovery were noted. Arterial desaturation and bradycardia requiring intervention were defined as pulse oximetry saturation less than 94% and heart rate of less than 40 beats per minute, respectively.
| Results|| |
One hundred patients who underwent general anaesthesia were studied and it took nearly 2.5 years to complete the study. The average age distribution was 45.1±15.2, the youngest being 18 and the oldest 75 years. The average body weight in kilograms was 71.0±14.9, the least being 26 and maximum 103. There was a preponderance of males (71%) as compared to females (29%). ASA physical status II (54%) was in abundance to ASA physical status I (46%). The average duration of surgery in minutes was 136±30.1. The details of the various surgical procedures performed are given in the [Table 1].
[Table 2] summarizes the different haemodynamic and respiratory variables recorded at different time intervals after induction that shows that these variables have been very stable perioperatively. There were two cases of difficulty of insertion of LMA, which were inserted in the second attempt. In one case there occurred folding of LMA cuff on itself making LMA difficult to be pushed inside. In the other case patient started closing the mouth just when the LMA had passed halfway inside the oral cavity. These problems were attributed to inadequate depth of anaesthesia and responded to deepening of anaesthesia. A single case of malpositioning of LMA was resolved immediately by reinserting the laryngeal mask without any supplementation of anaesthesia. There was one case of sore throat, which responded to adequate hydration and steam inhalation. One of the patients experienced postoperative vomiting in the recovery room. This was attributed to the administration of narcotics post operatively, and responded to anti-emetics. Dental trauma in one case in the form of coming out of a loose upper incisor was observed. [Table 3] summarizes the expected and observed complications.
| Discussion|| |
Procedures requiring prone position are traditionally induced, paralyzed and intubated in the supine position and then turned face down. This technique has several disadvantages like additional theatre personnel and anaesthesia time required, the risk of neurological trauma to the patient's neck and peripheral nerves, risk of dislodgment of endotracheal tube during the turning and positioning besides the associated risk of intubation such as trauma to teeth, pharynx and larynx. Alternative to this approach is asking patients to place themselves prone comfortably before anaesthesia is induced. This enables optimal positioning because patients know their most comfortable position, so the whole process is simplified, induction time is shortened and chances of any neurological trauma to patient's neck or peripheral nerves is lessened. The major disadvantage of induction in prone position is that direct laryngoscopy is usually not possible for tracheal intubation. However, this problem may be overcome by the use of classic laryngeal mask airway. Laryngeal mask airway use has been shown to provide an excellent airway in the adults  and children  for surgery in supine positions with either spontaneous or controlled ventilation. Rasanen (2000) recommended the use of LMA for surgeries in the lateral decubitus or the trendelenburg positions.  However, when prone position is needed for surgical access, some authors (Poltronieri, 1990) rule out the use of LMA for airway control.  Despite the advantages most anaesthesiologists do not use LMA in the prone position. In 1992 Kee WD, reported use of laryngeal mask airway in prone position for radiotherapy.  Mc Caughey  (1993) and Milligan KA  (1994) reported use of LMA in prone position for elective surgical procedures. Alexander Ng et al (2002) published his experiences of over 73 cases, allowed to breathe spontaneously without significant complications.  However, these studies were done on spontaneously breathing patients, which has one major disadvantage and that is that of hypoventilation which is mainly due to the respiratory depression effects of inhalational agents and opiates. In various published reports LMA has been used for airway rescue following accidental extubation in patients placed prone for surgery. Valero et al (2004) managed a patient in prone position with a drill bit penetrating the spinal canal at C1-C2, using a laryngeal mask.  Raphael et al (2004) described a case of accidental extubation of the trachea during spine surgery in a patient placed in the prone position, who was managed successfully by inserting a LMA while maintaining the patient in the same position.  Dingeman et al (2005) managed a five year old girl with Arnold Chiari malformation More Details who was accidentally tracheally extubated while positioned prone during a decompressive craniotomy and cervical laminectomy using LMA without difficulty.  Brimacombe et al (2005) reported the unusual case of airway rescue in the prone position with the proseal laryngeal mask airway.  Recently Weksler et al (2007) published a study comparing laryngeal mask airway in prone position with conventional endotracheal tube anaesthesia and concluded that prone induction and insertion of LMA is a valid technique. 
In our study the feasibility of classic LMA as an alternative for providing controlled ventilation anaesthesia in prone position was evaluated along with haemodynamic, ventilatory, and recovery characteristics. The undesirable side effects and problems in performing this technique were also looked into.
After the anaesthesia was induced, the lungs of all the patients were easily ventilated manually via a face mask. Gravity appears to help by causing the jaw and tongue to fall anteriorly. Mechanical ventilation was easily performed in all patients and sealing was adequate after using maximum cuff inflating volumes, allowing low flow technique of fresh gas flow less than a liter. Probably the cephalic displacement of larynx facilitates the sealing. Once LMA position was secured and confirmed that manual controlled ventilation was possible smoothly without any obstruction then only muscle relaxant was given and ventilator switched on for controlled ventilation. This practice proved quite safe as no patient went into muscle relaxant induced apnoea where they could not be ventilated manually or with ventilator.
There was no significant change in systolic, diastolic and mean blood pressures as compared to preinduction levels in most of the patients. However, blood pressures tend to be lower than the pre induction values at the end of surgery. This can be attributed to the cardiovascular depressant effects of inhalational agent and prone positioning. There was increase of heart rate after induction in most of the patients observed. Gradually heart rate stabilized at pre induction values or slightly less and heamodynamic stability was maintained throughout the procedure [Table 2]. The recovery in most of the patients was quite rapid and very smooth.
Our study confirmed the earlier published reports which demonstrated a clear advantage while providing anaesthesia after placing patients first in prone position with the use of LMA, with minor complications amenable to routine management. The study also confirmed the feasibility of using classic LMA in prone position using controlled ventilation without any major problems. We concluded the successful performance of controlled ventilation in these prone patients, the safety of which lies in the fact that muscle relaxants are only to be administered when laryngeal mask airway's proper position has been confirmed and secured for smooth and unobstructed manual ventilation. On the basis of our experience with this feasibility study we recommend the technique as an alternative method of airway management for surgeries in prone position needing controlled ventilation for anaesthesiologists who will practice it on a regular basis. However, randomized controlled trials would be needed for comparative evaluation of this technique with conventional endotracheal intubation and controlled ventilation.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]