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Effect of cricoid pressure on the laryngoscopic view by Airtraq in elective caesarean section: a pilot study

Riad, Waleeda; Ansari, Tarekb

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European Journal of Anaesthesiology: November 2009 - Volume 26 - Issue 11 - p 981-982
doi: 10.1097/EJA.0b013e32832e9a32

Editor,

Airtraq is a disposable battery-operated optical laryngoscope that was developed to facilitate tracheal intubation in patients with normal as well as patients with difficult airways. The device has a short learning curve and its ease of use in both experienced and inexperienced hands was reported recently [1]. It is introduced into the mouth over the dorsum of the tongue to provide an indirect view of the glottis without the need to achieve a direct line of vision required by conventional Macintosh laryngoscopy [2]. The Airtraq has several advantages when used for adult patients, it produces less alteration to the haemodynamic parameters, and reduces the duration of endotracheal intubation, airway trauma and need for additional assistance [3].

Physiological changes during pregnancy place the parturient at increased risk for regurgitation of gastric contents and pulmonary aspiration if general anaesthesia is required. Tracheal intubation after rapid-sequence induction with cricoid pressure remains the standard approach to airway management during general anaesthesia for caesarean section, as it minimizes the risk of pulmonary aspiration [4]. However, application of cricoid pressure may produce airway obstruction at the level of the cricoid cartilage or vocal cords, and interfere with the ease of tracheal intubation due to anatomical distortion. It was documented in the literature that time to successful intubation was prolonged in randomized studies of fibre-optic as well as lightwand-assisted tracheal intubation [5].

The purpose of this observational study was to assess the effect of cricoid pressure on the ease and time for successful intubation using the Airtraq optical laryngoscope.

After approval of the hospital research committee and informed patient consent, 10 consecutive pregnant patients undergoing elective caesarean section under general anaesthesia were enrolled in the study. Patients were pre-medicated with 150 mg ranitidine orally the night before and the morning of surgery and 0.3 mol/l sodium citrate 30 ml before induction of anaesthesia. On arrival in the operating theatre, a large-bore intravenous catheter was inserted and an intravenous infusion of Hartmann's solution was started. The standard monitoring with continuous electrocardiography, noninvasive arterial blood pressure monitoring, pulse oximetry and capnography were used for all parturient. Patients were positioned supine with left uterine displacement and preoxygenated with breathing 100% oxygen for 3 min before the induction of anaesthesia. Anaesthesia was induced with 3–4 mg kg-1 thiopental based on pregnant body weight and injected over 30 s until loss of consciousness was confirmed clinically by loss of eyelash reflex, this was followed by induction of succinylcholine 1.5 mg kg-1. Once consciousness was lost, double-handed cricoid pressure was applied by another anaesthesiologist with the head and neck in the optimal intubating position and maintained until the airway was secured using a tracheal tube.

The Airtraq conduit channel was loaded with a size 7.5 mm cuffed endotracheal tube (ETT) and the blade was advanced through the mouth in the midline over the centre of the tongue to visualize the airway. When the tip of the scope was positioned in the vallecula, as recommended by the manufacturer, with centralization of the glottic view in the viewfinder, the ETT was advanced under direct vision between the vocal cords, held in place and the device was removed. Cricoid pressure was released only after confirmed correct placement of the ETT by capnography.

Preoperative airway assessment was done by the researchers, which included modified Mallampati score, interincisors and thyromental distances. Time taken to intubate the trachea, number of intubations, overall success rate and airway trauma were recorded by an independent observer. The duration of intubation was calculated from insertion of the scope and ended by connection of the ETT to the anaesthesia machine and confirmed by the appearance of capnography.

Patients' characteristics and intubation data are shown in Table 1. The trachea for all parturients was successfully intubated at the first attempt without the need for any external manipulation. Airway trauma as indicated by blood on the device was reported in two patients. In the presence of cricoid pressure using the Airtraq, the mean duration of intubation was 25.8 s, which is markedly shorter than using Macintoch laryngoscopy in our previous report [6]. From our point of view, it is unethical to conduct a randomized controlled trial for patients undergoing caesarean section to test the study hypothesis; this is considered a limitation of the current work.

Table 1
Table 1:
Patients' and intubation characteristics

In conclusion, application of cricoid pressure during induction of anaesthesia for elective caesarean section neither prolongs the time nor interferes with ease of endotracheal intubation using Airtraq.

References

1 Maharaj CH, Costello JF, Higgins BD, et al. Learning and performance of tracheal intubation by novice personnel: a comparison of the Airtraq and Macintosh laryngoscope. Anaesthesia 2006; 61:671–677.
2 Suzuki A, Toyama Y, Iwasaki H, Henderson J. Airtraq for awake tracheal intubation. Anaesthesia 2007; 62:746–747.
3 Maharaj CH, Costello JF, Harte BH, Laffey JG. Evaluation of the Airtraq and Macintosh laryngoscopes in patients at increased risk for difficult tracheal intubation. Anaesthesia 2008; 63:182–188.
4 Rosen MA. Management of anesthesia for the pregnant surgical patient. Anesthesiology 1999; 91:1159–1163.
5 Smith CE, Boyer D. Cricoid pressure decreases ease of tracheal intubation using fibreoptic laryngoscopy (WuScope System). Can J Anesth 2002; 49:614–619.
6 Riad W, Moussa A. Lornoxicam attenuates the haemodynamic response to laryngoscopy and tracheal intubation in elderly. Eur J Anaesthesiol 2008; 25:732–736.
© 2009 European Society of Anaesthesiology