Use of Laryngeal Mask Airway in Prone Position

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USE OF LARYNGEAL MASK AIRWAY IN PRONE POSITION Vijay Kumar*, K. Lalitha* and Talib Lone** *Senior Consultant Anaesthesiologist, **Post Graduate Resident, Department of Anaesthesiology and Critical Care, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi 110 076, India. Correspondence to: Dr. Vijay Kumar, Senior Consultant Anaesthesiologist, Department of Anaesthesiology and Critical Care, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi 110 076, India. e-mail: [email protected] Laryngeal mask airway (LMA) has been used widely since 1988 for spontaneous and controlled ventilation anaesthesia for variety of surgical procedures. Usually its use is limited to patients undergoing surgery in supine position. 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 anesthesiologist, it is time consuming and requires shift of manpower from other tasks to properly position the patient. As an alternative to the traditional approach we have used classic laryngeal mask airway in different patients needing prone position for surgery. Though few studies have been published in the literature where use of laryngeal mask airway in prone position was reported, but they have been used mostly in spontaneously breathing patients for short duration surgeries. We have used classic laryngeal mask airway successfully in patients who need controlled ventilation during short, moderate and even long duration surgeries in prone position. In the prospective audit of 100 patients we have found prone insertion of laryngeal mask airway to considerably simplify the management of this group of patients, without compromising the safety. Key words: Laryngeal mask airway, Prone position, Controlled ventilation.

padding must be applied at pressure points, and preventive care must be applied to the eyes. All these can further delay the initiation of surgery and the operating theatre workflow.

THE prone position is commonly used to provide surgical access to variety of surgeries including microdiscectomy, reconstructive surgeries of the spine, varicose vein avulsions, excision of pilonidal sinus, percutaneous nephrolithotomy, repair of Achilles tendon, posterior calf surgeries and various plastic surgery procedures. Traditionally general anesthesia carried out in prone position should always be administered with the patients being paralyzed, intubated and ventilated. Conventionally, the patients are anaesthetized in the spine position on a trolley and after tracheal intubation using nonkinking endotracheal tube, they are turned over to prone position on operation table. Even though this method is familiar to most anesthesiologists nevertheless this is an invasive procedure which may sometimes be unnecessary for short surgical procedures and is not without its own inherent risk of intubation. Operations performed in the prone position are 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. In addition, special care is required to avoid respiratory impairment, adequate 29

Since the laryngeal mask airway became commercially available in 1988, it is used widely in different situations which previously required tracheal intubation. It has been used for anesthesia in prone position during several surgical procedures. Over the past several years we have made it a frequent practice to induce anesthesia and introduce the classic laryngeal mask airway after the patient has assumed a comfortable and stable prone posture while still conscious. This is done to improve rapid tracking of patients during anesthesia by decreasing time required for induction, patient positioning and recovery. We have used the laryngeal mask airway in this way in a group of over hundred patients. The aim of this communication is to report a prospective audit of 100 patients anaesthetized with this technique in confirmation of earlier published conclusions with the modifications of using muscle relaxation and controlled ventilation. Apollo Medicine, Vol. 5, No. 1, March 2008

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METHODS

recommendation. As the laryngeal mask airway passed the incisors, the patient chin was released, allowing the tongue to fall forwards, thereby opening up the posterior oropharyngeal space for the laryngeal mask airway (Fig. 3). 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 laryngeal mask airway by checking the adequacy of manual ventilation with no obstruction and then properly fixing it to the patients face (Fig. 4). All patients were mechanically ventilated and anesthesia 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 turned supine and transferred to recovery bed. Patients had their spontaneous ventilation restored and laryngeal mask airway was taken out when they were fully conscious.

We conducted a prospective audit of 100 adult consenting patients of ASA physical status I and II who required general anesthesia in the prone position. All the patients were scheduled for the elective surgery in which the use of laryngeal mask airway was deemed appropriate. Patients with suspected difficult airway, poor dentation, skeletal diseases, history of gastroesophageal reflux and lack of patient cooperation 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. This position consists of two pillows under the thorax and one pillow under 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 (Fig. 1). Following adequate preoxygenation with oxygen delivered at 6 liters per minute by a loosely applied facemask, anesthesia was induced intravenously with 1 mcg/kg body weight of fentanyl and 2-3 mg/kg body weight of propofol. After loss of consciousness facemask was applied firmly allowing manual ventilation of lungs with 100% oxygen (Fig. 2). Then the head was extended using a hand on forehead and mouth opened by holding the tip of patients chin by operating assistant and laryngeal mask airway was inserted with its cuff deflated. Size of laryngeal mask airway was selected according to the patient weight and manufacturer

Demographic data, heamodynamic, ventilatory, anesthetic variables and recovery characteristics were recorded. Problems encountered before induction, at induction, during the maintenance period and recovery was noted. Arterial desaturation and bradycardia requiring intervention were defined as pulse oxymetry 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 for practical aspects and safety of inducing and insertion of laryngeal mask airway in

Fig. 2. Application of face mask and manual ventilation

Fig. 1. Patient obtains comfortable prone position before Apollo Medicine, Vol. 5, No. 1, March 2008

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Table 1. Demographic characteristics Demographic data

n=100

Age (year, mean±SD)

45.1±15.2

Body weight (kg, mean±SD)

71.0±14.9

Sex (Male: Female)

71:29

ASA Physical status (I:II)

46:54

Table 2. Operative details n = 100

Fig. 3. Pulling of chin forward to facilitate insertion of laryngeal mask airway

Type of surgery

41

Spine (%) Microdiscectomy Laminectomy Excision of spinal tumors Plastic (%)

8

Burns debridement Back tumors excision Liposuction Orthopedic (%)

15

Achilles tendon repair Calf muscle surgeries Shoulder surgeries Calcanenal surgeries Surgeries around elbow Vascular (%)

11

Varicose veins surgery General (%)

Fig. 4. Final position of patients head with laryngeal mask in situ.

25

Excision of pilonidal sinus Gluteal surgeries Perineal reconstruction

prone position. 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 was in abundance to ASA physical status I (Table 1). The average duration of surgery in minutes was 136±30.1. The details of the various surgical procedures performed are given in the Table 2.

Duration of anesthesia (min)

136 + 30.1

one case of malpositioning of laryngeal mask airway. One patient had soreness and in one case vomiting was observed post operatively. In one case dental trauma was observed on insertion of laryngeal mask airway while one patient complained of swelling of left side of tongue on third post operative day. Table 4 summarizes the expected and observed complications. DISCUSSION

Table 3 summarizes the different heamodynamic and respiratory variables recorded at different time intervals after induction.

Procedures requiring prone position are traditionally induced, paralyzed and intubated in the supine position and then turned face down. This technique has several

There were two cases of difficulty in inserting and 31

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Table 3. Cardiorespiratory characteristics At induction

10 min

30 min

60 min

84.1±13.5

75.6±14.7

74.2± 3.9

75.5± 4.l

SBP (mmHg, mean ± SD)

131.9±19.5

103.8±14.7

106.4±12.5

111.2±15.l

DBP (mmHg, mean ± SD )

75.8±11.2

60.9±12.4

63.0±11.4

65.7± 4.5

MBP (mmHg, mean ± SD)

94.5±12.5

75.2±12.0

77.4±10.5

79.0±18.3

SpO2 (%, mean ± SD)

98.1± 2.1

98.5± 2.2

98.7± 1.4

98.7± 1.1

EtCO2 (Kpa, mean ± SD )

6.47± 0.7

5.15± 0.6

5.10± 0.5

5.04± 0.5

HR (bpm, mean ± SD)

surgeries in the lateral decubitus or the trendelenburg positions. However, when prone positions are needed for surgical access, some authors rule out the use of laryngeal mask airway for airway control. Despite the advantages most anesthesiologists do not use laryngeal mask airway in the prone position, perhaps out of the fear of difficult laryngoscopy if airway problem should occur.

Table 4. Complications Problem

n = 100

Insufficient anaesthetic depth

2

LMA malpositioning

1

Laryngospasm

0

Arterial desaturation

0

Hypoventilation

0

Blood on LMA

0

Sore throat

1

Hoarseness

0

Postoperative nausea vomiting

1

Dental trauma

1

Bradycardia

0

In 1992 Kee WD, reported use of laryngeal mask airway in prone position for radiotherapy, McCaughey in 1993 and Milligan KA in 1994 reported laryngeal mask airway use in prone position for elective surgical procedures. Alexander Ng, et al., in 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 laryngeal mask airway was also used for air way rescue following accidental extubation in a patient placed prone for surgery. Valero, et al. managed a patient in prone position with a drill bit penetrating the spinal canal at C1-C2, using a laryngeal mask. Raphael, et al. 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 laryngeal mask airway while maintaining the patient in the same position. Dingeman, et al. managed a five year girl with Arnold-Chiari malformation who was accidentally tracheally extubated while positioned prone during a decompressive craniectomy and cervical laminectomy with laryngeal mask airway without difficulty. Brimacombe, et al. reported the unusual case of airway rescue in the prone position with the proseal laryngeal mask airway. Recently, Weksler, et al. published a study comparing laryngeal mask airway in prone position with conventional endotracheal tube anesthesia and concluded that prone induction and insertation of

disadvantages like additional theatre personnel and anesthesia time required, the risk of neurological trauma to the patients 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 before anaesthesia induction. This enables optimal positioning because patients know their most comfortable position, so the whole process is simplified, the induction time is shortened and the operative track is quickened. The major disadvantage of this approach is that direct laryngoscopy is usually not possible in the prone position and airway management may be difficult. However, this problem may be overcome by the use of laryngeal mask airway. With the advent of laryngeal mask airway, its 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 recommended the use of laryngeal mask airway for Apollo Medicine, Vol. 5, No. 1, March 2008

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laryngeal mask airway is a valid technique. In our study we evaluated the classic laryngeal mask airway as an alternative for providing controlled ventilation anesthesia in prone position. We observed the practical aspects of performing the anesthesia in prone position with laryngeal mask airway. Hemodynamic, ventilatory, anesthetic and recovery characteristics were evaluated. We looked into the undesirable side effects and problems in performing this technique.

operative vomiting in the recovery room. This was attributed to the administration of narcotics post operatively, and responded to antiemitics. Dental trauma in one case in the form of coming out of upper incisor was observed. The tooth involved was previously very loose and hence venerable in case of any airway management. CONCLUSION Our study confirmed the earlier published reports which demonstrated a clear advantage while providing anaesthesia after placing patients in prone position with the use of laryngeal mask airway, with minor complications amenable to routine management. We concluded the successful performance of muscle relaxation and controlled ventilation in these patients, the safety of which lies in the fact that muscle relaxants are only to be administered when laryngeal mask airways proper position has been confirmed for smooth and unobstructed controlled ventilation. The success of the technique described not only requires expertise that comes from practice but also confidence and knowledge. On the basis of our experience and published reports we recommend the technique as an alternative method of airway management for surgeries in prone position for anesthesiologists who will practice it on a regular basis.

After the anesthesia 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. There were two cases of difficulty of insertion of laryngeal mask airway, which were inserted in the second attempt. In one case there occurred folding of laryngeal mask airway. These problems were attributed to inadequate depth of anaesthesia and responded to deepening of anesthesia. A single case of malpositioning of laryngeal mask airway was resolved immediately by reinserting the laryngeal mask. 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 litre. Probably the cephalic displacement of larynx facilitates the sealing. As our patients were supported with two pillows under the chest, which minimized the restriction of anterior abdominal wall movement, hence ventilation was not adversely affected as would be expected due to reduction of compliance in the prone position.

BIBLIOGRAPHY 1. Davies M. Spontaneous ventilation: The controversies. In: Kerr DR. Australian Anaesthesia, Faculty of Anaesthetist, RACS Melbourne 1998; 57-61. 2. Ng A, Raitt DG, Smith G. Induction of anesthesia and insertion of a laryngeal mask airway in the prone position for minor surgery. Anesth Analg 2002; 94: 1194-1198.

As anticipated from the previous studies, we observed that cardiovascular stability was maintained in our series of patients. There was no significant change in systolic, diastolic and mean blood pressures as compared to pre-induction 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. By ten minutes heart rate stabilized at pre induction values or slightly less. The cause was probably the most common cardiovascular response to insertion of laryngeal mask airway.

3. Milligan KA. Laryngeal mask in the prone position. Anaesthesia 1994; 49: 449. 4. McCaughey W, Bhanumurthy S. Laryngeal mask placement in the prone position. Anaesthesia 1993,48: 1104-1105. 5. Weksler N, Klein M, Rozentsveig V, Weksler D, Sidelnik C, Lottan M, Gurman GM.Laryngeal mask in prone position: Pure exhibitionism or a valid technique. Minerva Anestesiol. 2007 Jan-Feb; 73(1-2): 33-37. 6. Posner A, Brody D, Ravin M. Effect of prone position with constant volume ventilation on PaCO2 in man. Anesth Analg 1965; 44: 435. 7. Brodrick PM, Webster NR, Nunn JF. The laryngeal mask airway: A study of 100 patients during spontaneous breathing. Anaesthesia 1989; 44(3): 238-241.

The recovery in most of the patients was quite rapid and very smooth. There was one case of sore throat which responded to post operative oral fluids and steam inhalation. One of the patients experienced post

8. Johnston DF, Wrigley SR, Robb PJ, Jones HE. The laryngeal mask airway in pediatric anesthesia. Anaesthesia. 1990; 45(11): 924-927. 33

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Personal Practice 9. Rasanen J. The laryngeal mask airway - first class on difftcult airways. Finnanest 2000; 33: 302-305.

13. Raphael J, Rosenthal-Ganon T, Gozal Y. Emergency airway management with a laryngeal mask airway in a patient placed in the prone position. J Clin Anesth 2004; 16(7): 560-561.

10. Poltronieri J. The laryngeal mask. Ann Fr Anesth Reanim 1990; 9: 362-366.

14. Dingeman RS, Goumerova LC, Goobie SM. The use of a laryngeal mask airway for emergent airway management in a prone child. Anesth Analg 2005; 100(3): 670671.

11. Kee WD. Laryngeal mask airway for radiotherapy in the prone position. Anaesthesia 1992; 47: 446-447. I2. Valero R, Serrano S, Adalia R, Tercero J, Blasi A, Sanchez-Etayo G, Martinez G, Caral L, Ibáñez G. Anesthetic management of a patient in prone position with a drill bit penetrating the spinal canal at C1-C2, using a laryngeal mask. Anesth Analg 2004; 98(5):1447-1450.

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15. Brimacombe J, Keller C. An unusual case of airway rescue in the prone position with the ProSeal laryngeal mask airway. Can J Anaesth 2005; 52(8): 884.

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