Ease of insertion of nasogastric tube, before or after endotracheal intubation under general anaesthesia

Editor, Insertion of a nasogastric tube (NGT) in anaesthetised, paralysed and intubated patients can be difficult; hence many manoeuvres like forward displacement of the larynx, neck flexion with lateral neck pressure and endotracheal cuff deflation have been described.1–4 Whether the difficulty is produced by the tongue (due to loss of tone under anaesthesia) or by change in anatomy by endotracheal tube or cuff is not well studied. There are no randomised studies to assess the ease of insertion of NGT in presence or absence of endotracheal tube in anaesthetised patients. This study was conducted to determine the success rate of NGT insertion in anaesthetised patients before or after endotracheal intubation. Methods After obtaining the approval from ethical committee and written informed consent, 124 patients were enrolled in the study (Ethical committee: SDMCMSH Hospital ethics committee, Reference No: SDMIEC: 222/2012, 29 December 2012, Secretary Dr Kamdod). The trial was registered with Clinical Trial Registry of India (CTRI/2013/05/003652). Patients aged 18 to 70 years, requiring general anaesthesia with endotracheal intubation, and NGT for various surgical procedures were included in the study. Patients with a full stomach and predicted difficult airway were excluded. The patients were randomised into NGT after intubation or NGT before intubation groups by using sealed envelopes. All the NGT insertions were performed by two senior anesthesiologists to avoid observation bias. For all patients, general anaesthesia was induced with fentanyl, propofol and vecuronium, and maintained by infusing propofol until NGT insertion and tracheal intubation were completed. In after intubation group, patients were intubated 3 min after giving muscle relaxant and endotracheal tube cuff was inflated, so that there was minimal leak at 20 cm H2O of pressure. Male patients were intubated with internal diameter 8.5 mm and female with 7.5 mm cuffed endotracheal tubes. After tracheal intubation, NGT insertion was attempted first with the neck in neutral position. On failure of first attempt, NGT insertion was done in following sequence: second attempt with neck neutral position; third attempt by turning patient's head to right, neck flexed and lateral neck pressure; and fourth attempt after deflating the endotracheal cuff (maintaining neck flexion and lateral neck pressure). If the fourth attempt also failed, then NGT was guided under direct laryngoscopic vision using Magill's forceps. In the before intubation group, after induction of anaesthesia positive pressure ventilation via a facemask was undertaken using 100% O2 for 3 min. NGT insertion was then attempted using the same method as that described for the after intubation group. After insertion of NGT, the patients were again mask ventilated and then intubated. Any time during the procedure, if the SpO2 fell below 90%, then NGT insertion was abandoned and mask ventilation was done. NGT insertion was confirmed by auscultation of gurgling sound over the epigastrium, when injecting air through the NGT. The procedure duration was measured with a stopwatch. Considering the first attempt success rate for NGT insertion after intubation as 45%, for an additional 25% change in the success rate, with an α error of 5 and 80% power, the sample size needed was 61 patients in each group. Primary endpoint was success rate of first attempt of NGT insertion. The secondary endpoints were number of attempts required and time taken for successful NGT insertion. Categorical data were compared using χ2 test and continuous data compared using independent sample t test. Results All 124 patients completed the study and were included in the analysis. There were no significant differences in the age, sex and weight of the patients between the groups. First attempt success rate was significantly higher in before intubation group (40/62) compared with the after intubation group (25/62) (Table 1). Total numbers of attempts needed and time taken for NGT insertion were also significantly lower in before intubation group compared with the after intubation group (Tables 1 and 2). Only 35% patients in the before intubation group needed second manoeuvres for NGT insertion, whereas 60% of the after intubation group needed the same. In one patient in the before intubation group, SpO2 dropped to 90%, hence the patient was mask ventilated and NGT was inserted again before intubation. None of the patients had significant bleeding from the nose.Table 1: Nasogastric tube insertion success before and after intubationTable 2: Number of attempts neededOur study shows that NGT insertion is easier in anaesthetised patients (with loss of muscle tone) before endotracheal intubation rather than after intubation. This suggests that it is the distortion caused by endotracheal tube and not the loss of airway tone as the possible cause for difficulty in NGT insertion. Previous studies have endoscopically visualised the site of NGT impaction in anaesthetised intubated patients and have demonstrated arytenoid cartilage and piriform sinus as the common sites of impaction.5 In the presence of an endotracheal tube, the arytenoid cartilages and piriform sinus may be displaced posteriorly thereby making them common sites of impaction. It is a normal practice to ventilate for 3 min after giving muscle relaxant with 100% O2. The 60 s of apnoea required for NGT insertion would not cause hypoxia or aspiration in normal cases, but could increase the ease of NGT insertion. We excluded cases of anticipated difficult airway. Delay caused by for NGT insertion may lead to hypoxia in cases of unanticipated difficult intubation. It is safe to avoid prior NGT insertion in cases in which airway difficulty is even remotely possible. The main limitation of this study is that it is not blinded, hence observer bias are possible. Second, patients in the after intubation group had one extra attempt of NGT insertion after deflation of the endotracheal cuff, which was not used in before intubation group. This manoeuvre was used to rule out cuff as cause of obstruction for NGT insertion. It is unlikely to affect results, as this manoeuvre was used last. We conclude that in anaesthetised patients, NGT insertion before endotracheal intubation requires fewer attempts, manoeuvres and takes less time than NGT insertion after endotracheal intubation. Acknowledgements relating to this article Assistance with the study: none. Financial support and sponsorship: none. Conflicts of interest none.