Similar efficacy of Ambu Laryngeal Mask® and LMA
Unique® during anaesthesia in children less than 30 kg
Torsten Lauritsen1, Renée Krivosic-Horber2, Bruno Marciniak2, Mark Thomas3,Søren Walther-Larsen1 and Steen W. Henneberg1
1Department of Anaesthesiology, Rigshospitalet, Copenhagen, Denmark, 2 Clinique d’anesthésie reanimation

Hôpital Jeanne de Flandre, LILLE Cedex, France, 3Great Ormond ST Childrens Hospital, London, UK
Aim
In order to compare the efficacy of the Ambu
Laryngeal Mask® (Ambu) with the LMA
Unique® (Unique), we aimed to investigate
non-paralysed infants/children with a weightof less than 30 kg in terms of insertion timein first attempt, insertion success rates,efficacy of seal, adequate positioning andintra- and postoperative complications.

BackgroundThe use of laryngeal masks inchildren has increased during thelast decade and therefore there
are demands for safe and reliabledisposable products.

LMAUnique(n = 27)

Table 1AMBU LM(n = 32)

Male (n)76.9%

Female (n)

23.1%

21.7%

Age (y)3.0 (2.6)

2.6 (2.3)

Weight (kg)14.0 (6.8)

13.0 (5.8)

Premedication

11.5%

8.7%

Analgesic before LM

80.8%

91.3%

Sevoflurane before LM

38.5%

39.1%

Size of mask # 1

15.5%

8.8%

Size of mask # 1

11.5%

30.4%

Size of mask # 2

53.8%

39.1%

Size of mask # 2

19.2%

21.7%

LMA Unique®

Ambu Laryngeal Mask®

% or mean (SD)No significant difference between the groups

Materials and Methods
Patients (n = 59) were randomized and included in the study. Thirty twopatients (54%) were randomized to Ambu and 27 patients (46%) to Unique. For
patient characteristics refer to Table 1. A randomized, single-blinded, multicentre, international study design was used, including children scheduled toundergo elective short surgical/anaesthetic procedures. The size of the mask
was determined by the weight of the child according to manufacturers
recommendations. Insertion time was from picking up the laryngeal mask tofirst recording of expiratory carbon dioxide. A failed attempt was defined as
removal of the device from the mouth. The intra cuff pressure was measured
and adjusted to 60 cm H2O where after oropharyngeal leak pressure wasdetermined. Final position of the laryngeal mask was determined fiber optically.

Results
Insertion time at first attempt (mean±SD) was 12.9±5.0 sec vs.
17.4±6.2 sec (Ambu vs. Unique) (p = 0.004, Figure 1). All 32 Ambu
were inserted in first attempt, whereas 6 (22%) of the Uniquerequired a second insertion attempt (p = 0.005). Vocal cords werefiber optically visualized in 93.7% of the patients in the Ambu
group and in 66.7% in the Unique group (Figure 2) (p < 0.05). On ascale from 1 (vocal cords not seen) to 4 (only vocal cords seen) themean score was 3.0 vs. 2.2 (p = 0.004, Mann-Whitney t-test). Endtidal CO2 after laryngeal mask placement was 5.2±0.8 kPa (Ambu)
vs. 5.9±1.0 kPa (Unique) (p = 0.01, Student t-test). No significant
differences was found regarding oropharyngeal leak, leak overstomach and per- or postoperative complications.

Insertion time in first attempt (mean+SD)
252015sec

78.3%

1050Ambu LM

LMA UniqueFigure 1Discussion
Mean insertion time for the LMA Unique® at first attempt was 34%
longer than the Ambu LM®, furthermore, 22% of the patientsrequired a second insertion to obtain adequate position. However,for the majority the difference of 5 sec in insertion time is without
significant clinical importance. On the other hand, more than one
insertion of a laryngeal masks could potentially be harmful,resulting in laryngospasms, coughing, edema and injury to theoropharyngeal region. No differences in complications were seen
when comparing the two masks. Together both masks provided
adequate ventilation with few side effects. The designs of the masks
may account for the significant differences when position of themask in relation to the trachea was assessed fiber optically.
Although, the vocal cords (trachea) were not visible in 6% (Ambu)
and 33% (Unique) of the patients, it did not seem to influence theefficacy of the seal, nor the ventilation.

Fiber optic position of LM
100%
80%
60%
40%
20%
0%
AMBU LM
Only voc al c ords seen
Vocal cords + anterior epiglottis

LMA Unique
Vocal cords + posterior epiglottis
Vocal cords not seen

Figure 2Conclusion
Significantly shorter insertion time, more successful insertion and better positioning was seen withthe Ambu Laryngeal Mask®. However, the clinical relevance of these differences when comparing
Ambu Laryngeal Mask® to LMA Unique® is limited. Therefore, personal preferences and priceremain the most important factors when choosing between the two.
Correspondence: torsten.lauritsen@rh.hosp.dk