Comparison of the insertion of LMA classic^TM by the standard insertion technique Vs the 90-degree rotational technique - A prospective randomised comparative study

 

 

Abstract               Background and Aims: The Laryngeal Mask Airway has become an integral component of anaesthesia practice, airway management and management of the difficult airway. The standard insertion technique of the LMA as described by Dr. Archie Brain has found to have a varying degree of successful insertion on the first attempt. An alternative to the standard technique of insertion is the insertion of the LMA by the 90 degree rotational technique. The rotational technique has been proposed to improve the success rate of insertion of the LMA and decrease the time taken for its insertion. The objective of our study was to compare the success rate, number of attempts, time taken, haemodynamic changes and post-operative complications between the insertion of the LMA by the standard technique vs the 90 degree rotational technique. Methods: 78 patients were divided into 2 equal groups – In group ST the LMA was inserted by Standard Technique and in Group RT the LMA was inserted by the 90 degree Rotational Technique. Results: The number of attempts taken was higher in the standard technique as compared to the 90 degree rotational technique, but this difference was not statistically significant (5 multiple attempts vs 2 multiple attempts, P = 0.45), the mean time taken to insert the LMA was significantly shorter with rotational technique (25.26 by ST vs 3.63 by RT, P <0.0001), the success rate was higher by the rotational technique but this was not statistically significant (97.44% by ST vs 100% by RT, P=0.93). The incidence of blood staining is higher in patients with the standard technique as compared to the rotational technique. (7 in ST vs 2 in RT, P-0.025). No significant difference between the hemodynamic changes was seen. Conclusion: The rotational technique provided faster insertion of the LMA. Thus, it may be considered as an alternative to the standard technique for insertion.

Key Word: LMA.

 

 

INTRODUCTION

The LMA Classic™ was introduced into clinical practice in 1988.¹ The LMA has an established role in modern anaesthetic practice. It is used to maintain the airway in elective short surgical procedures with spontaneous ventilation as well as in controlled ventilation.². The practice guidelines for management of the difficult airway by ASA also emphasize the role of supraglottic airway devices and recommends to always consider its use in the management of difficult airway³ Positioning of the LMA is of utmost importance. If the LMA is not inserted correctly, problems such as anaesthetic gas leakage, obstruction and gastric insufflation may occur.⁴ There are various methods of LMA insertion. The most commonly used is the index finger insertion technique (standard technique) as described by Dr.Archie Brain. Various other techniques have also been described of which the 90 degree rotation technique is found to have a good success rate. The 90° rotation technique was first described by Hwang et al. and involves the following steps: the entire cuff of the LMA is inserted inside the mouth, rotated counter-clockwise through 90° and advanced until the resistance of the hypopharynx is felt ⁵. The use of this method is known to increase the success rate of insertion and decrease the incidence of blood staining of the LMA and sore throat compared to standard technique. The purpose of this study was to compare the clinical efficacy of the rotational technique vs the standard technique for inserting the LMA ClassicTM.

 

MATERIALS AND METHODS

After obtaining approval from the ethical committee board of Dr. D. Y. Patil Medical university, we included 78 patients in prospective randomised controlled study. All these patients were undergoing general anaesthesia. These patients were divided into two random groups equally. Inclusion criteria for the study was fulfilled which included patient age between 18-60 years, ASA-I-II fit patients and for short surgical procedure of less than 1 hr requiring general anaesthesia. Exclusion criteria for the study were patients with BMI>30, anticipated difficult intubation, and Mouth opening less than 2 fingers. After confirming NBM status, standard monitors like ECG, Pulse oximeter, NIBP were attached. Preoxygenation was done with 100% oxygen for 3 minutes. Patient was premedicated with Inj. Glycopyrrolate 0.004 mg/kg, Inj. Midazolam 0.05 mg/kg and Inj. Fentanyl 2mcg/kg intravenously 10 minutes prior to induction. Anaesthesia was induced with Inj. Propofol 2mg/kg. Loss of eyelash reflex and apnoea was taken as end point of induction. After ensuring proper jaw relaxation LMA classic was inserted either by standard technique or rotation technique by randomisation. The correct size of LMA was selected according to weight of the patient. The cuff was deflated and posterior part of the LMA will be lubricated with water soluble jelly. In the standard technique group, LMA was held like a pen and inserted along the palatopharyngeal curve using the index finger until definite resistance was felt. In the rotation technique, the cuff was inserted into the mouth and rotated counter clockwise or clockwise through 90 degree until the resistance of hypopharynx was felt. The cuff was inflated and effective airway was assessed by looking at the capnograph trace, adequate chest expansion and available leak with peak airway pressure of less than 15 cm H2O.

In both the groups, 2 attempts of 90 seconds each was allowed. If both the attempts failed, patient was either mask ventilated or intubated and excluded from the study.

We studied the following aspects during LMA insertion:

1. The number of attempts for successful insertion of LMA was noted.
2. The time taken to insert the LMA: The time between the insertion of LMA into the mouth to correct placement of the LMA and inflation of the cuff.
3. The haemodynamic paramenters will be recorded Heart Rate (HR), Systolic blood pressure (SBP), Diastolic Blood Pressure (DBP) and mean arterial pressure (MAP).
4. Complications such as sore throat, trauma, blood staining of LMA.

 

RESULTS

A total of 78 patients were considered for the study, 39 each in standard and 90 degree rotational technique respectively. The two groups were similar with respect to age and gender. Most of the patients were between 30 and 40 years of age. (Table 1 and 2).

Table 1: Age distribution

 

Table 2: Sex distribution

The number of attempts taken for successful insertion of Laryngeal Mask Airway was more in standard technique when compared to 90 degree rotational technique. Five patients in the standard technique group required two attempts whereas in 90 degree rotational technique group, 3 patients required 2 attempts for successful insertion (Table 3)

Table 3: Comparison of no. of attempts required

The time taken for successful insertion of classic laryngeal mask airway by rotation technique was 16.5 ± 3.5 seconds whereas in the standard technique it was 25.2 seconds ± 5.37. There is significant statistical difference between both the groups. (Table 4)

 

Table 4: Mean time taken to insert LMA

The success rate of insertion of LMA by the Rotational technique was (100%) as compared to the Standard technique 97.44%. This was not statistically significant. (Table 5)

 

Table 5: Success rate comparison

The change in haemodynamic parameters like heart rate, systolic blood pressure, diastolic blood pressure and mean arterial pressure in both groups were statistically comparable (Table 6,7,8,9).

 

Table 6: Comparison of mean heart rate

 

Table 7: Comparison of SBP

 

Table 8: Comparison of DBP

Table 9: Comparison of Mean of MAP

Complications such as blood staining was seen in both techniques but it was significantly higher in the Standard Technique. Post operative sore throat was seen in both the techniques but comparable. (Table 10 and 11)