Introduction and Background:
A
variety of devices are available for securing the airway during conduct of
general anaesthesia, the gold standard being the endotracheal tube. However, it
may be replaced with less invasive devices to reduces complications such as
glottis trauma, ischemia of the tracheal mucosa with subsequent stenosis to
list a few; provided this does not compromise the patient safety.Baska mask is
a novel airway device with a self sealing variable pressure cuff which
increases proportionately with increasing airway pressure during positive
pressure ventilation. It has an insertion tab for manually curving the mask for
easy insertion. The large distal aperture locates at the upper oesophagus and
opens into the sump cavity for easy drainage of gastric fluid thus minimising
the risk of aspiration. The advanced airway opening provides superior patency
of seal and increased protection against gastric overflow.
Dr.
Archie Bain developed the laryngeal mask airway in 1982 at royal London
hospital as a modification of the Goldman dental mask. Supraglottic airway
devices in comparison to endotracheal tube reduce the stress response which
occurs with laryngoscopy and intubation reduces requirement of anaesthetic
agents for airway tolerance, neuromuscular blockade not always necessary for
insertion, easier to insert, have a lower incidence of sore throat, it can be
easily inserted in patient with cervical spine injury.
Baska
mask is a novel airway device which has a self sealing variable pressure cuff
which increases proportionately with increasing airway pressure during positive
pressure ventilation. The cuff is continuous with the airway channel and gets
inflated with positive pressure ventilation. It has an insertion tab for
manually curving the mask for easy insertion. It has a large distal aperture
which locates at the upper oesophagus and has a sump cavity for easy drainage
of gastric fluid thus minimizing aspiration risk. The dorsal surface is made in
a way that it directs the oropharyngeal secretions towards the side channel to
which suction can be attached. The tube also has a built in bite block. The proximal end has loops which help in
fixation of the mask.
Aim:
The aim of this study is to see the utility of
Baska mask with regards to management of airway during general anaesthesia.
Study design:
It will be
a Prospective
observational study
Patients and methods:
Patients undergoing
surgeries in Tata Memorial Centre over duration of one year will be enrolled in
the study. All patients fulfilling the inclusion criteria and after obtaining
informed written consent, posted for elective surgery under anaesthesia will be
included in the study.
Inclusion criteria: Participating
patients should satisfy the following:
1.
ASA status I-II
2.
>18 years of age
3.
Mallampati class I-II
4.
Having a mouth opening > 3 cm
5.
BMI < 30 kg/m2
6.
Elective surface surgery of short duration
requiring general anaesthesia.
Exclusion criteria:
1.
Patients with anticipated difficult airway
2.
Current or recent sore throat
3.
Gastro-oesophageal reflux disease
4.
Cervical spine disease
5.
Pregnancy
6.
Dysphonia or dysphagia.
Sample
size:
The literature regarding the use of Baska mask is
scarce with first attempt success rates ranging from 72-88%. To detect a first
attempt success rate of 80% with 8% precision (range 72% to 88%) at 95%
confidence, we will need to study 97 patients. Therefore, we will include 100
patients to allow for protocol violation, lack of data, etc. This study will be
done over a period of 12 months.
Methodology:
This will
be a prospective observational. After obtaining Ethics committee approval and
written informed consent, 100
patients will be enrolled.
Participating patients should satisfy
following criteria:
1.
ASA status I-II
2.
>18 years of age
3.
Mallampati class I-II
4.
Having a mouth opening > 3 cm
5.
BMI < 30 kg/m2
6.
Elective surface surgery of short duration
requiring general anaesthesia.
Following patients will be excluded:
1.
Patients with anticipated difficult airway
2.
Current or recent sore throat
3.
Gastro-esophagealreflux disease
4.
Cervical spine disease
5.
Pregnancy
6.
Dysphonia or dysphagia.
After obtaining informed consent from the
patients, an appropriate sized Baska mask will be used according to the
recommendation of the manufacturer.
Anaesthesia
will be induced with fentanyl 2mcg/kg and propofol 2 mg/kg. Intermediate acting
muscle relaxant will be used for muscle paralysis. Hemodynamic parameters- HR,
SBP, DBP, MAP, will be measured non-invasively at following intervals: before
induction of anaesthesia and every minute up to 5 minutes after induction of
anaesthesia. Anaesthesia will be maintained with Sevoflurane/Isoflurane and N2O
in 40% oxygen. Tidal volume will be adjusted to keep end-tidal-CO2
concentration between 30-35 mm Hg. The primary end point of the study will be first attempt success rate
of insertion of baska mask.
Variables measured will be:
1. First attempt success rate of insertion of Baska
mask.
2. Overall success rate of insertion of Baska mask.
3.
Number of attempts needed for insertion.
4.
Time required to secure the airway.
5.
Magnitude of hemodynamic response from
baseline to up to 5 minutes after insertion.
6.
Adequacy of airway sealing pressure (no leak
at 20 cm H2O airway peak pressure or tidal volume 8 ml/kg).
7.
Stability of device intra-operatively. Any
displacement or need to reinsert the device intra-operatively.
8.
Need to change over to endotracheal
intubation.
9.
Presence of sore throat 1 h our after removal
of device.
10.
Presence of dysphagia (after giving a few
sips of water) 1 hour after removal of device.
11.
Any adverse events such as bronchospasm, Laryngospasm
or desaturation (<92%) aspiration, regurgitation of gastric contents.
Insertion and positioning: A single
operator after achieving the competency in insertion of the airway device will
insert the airway in all patients. Airway insertion time will be recorded using
a stop watch. Recording will start when the device will be inserted in the patient’s
mouth and stop when an adequate airway (as described above) is obtained. The
number of attempts required to correctly position the device will be recorded,
along with the size used. Once the device is optimally positioned, its position
will not be altered unless clinically indicated.
Laryngospasm,
if occurs will be recorded.
Airway sealing pressure: After
optimally positioning the device, airway sealing pressure will be measured by
closing the expiratory valve of the circle system at a fixed gas flow and
noting the airway pressure at which the dial on the aneroid manometer reaches
equilibrium.
Degree of irritation: One hour
post-operatively, patients will be asked about presence of sore throat or
dysphagia.
Ethical Considerations:
The study
will be initiated after obtaining the approval of The Institutional Ethics
Committee. Written informed consent will be taken from all participating
patients.
Statistical analysis:
Since this
is an observational study, we will use descriptive analysis to describe success
rate. A student’s t test and Chi square test will be used for describing
adverse events. |