Self-knotting of a nasogastric tube passed through i-gel™.

Sir,

A 55 kg, 35-year-old lady, was anaesthetised for laparoscopic cholecystectomy. A no. 3 i-gel™ (Intersurgical Ltd., Wokingham, Berkshire, UK) supraglottic airway device was used to maintain airway and a 12FG nasogastric tube (NGT) (Romsons, Agra, Uttar Pradesh, India) passed through its gastric channel, for decompression of the stomach, in one attempt without encountering any resistance. On completion of the surgery, the NGT could not be pulled out of the channel. The i-gel™ and the NGT were removed en masse. The NGT was found to have a lariat loop knot at its gastric end [Figure 1].

Figure 1

Knotted gastric end of the nasogastric tube removed along with the i-gel™

i-gel™ is a supraglottic airway device made of medical grade thermoplastic elastomer, which has an integrated gastric channel to facilitate venting of stomach gas and allowing passage of NGT to empty the stomach contents. Although there are reports of self-knotting of NGT,[1] there are no reports of such an occurrence in NGT passed through i-gel™, possibly because its channel prevents the bending of the NGT and facilitates its entry into the oesophagus.

The incidence of self-knotting of NGT appears to be low.[1] Risk factors include smaller diameter NGT, insertion deep into the stomach, and repetitive advancement of the NGT, pushing or pulling of NGT after it has been placed and interference with an endotracheal tube in the intubated patient.[2345] The diameter of the NGT in the case was small due to restrictions of the i-gel channel dimension. Once knotted, the traction during retrieval tightens the knot.[1] NGTs are generally made up of polyvinyl chloride, which tends to soften when exposed to body temperature. The soft tubes tend to roll up and this may promote knot formation. Mechanism of knot formation is similar to that of supercoiling. Knotting of NGT during both insertion and removal can lead to serious complications, which include respiratory distress,[5] severe laryngeal injury,[5] and tracheoesophageal puncture,[6] in both intubated and non-intubated patients.

Knotting of NGT can be prevented by using large bore tubes, avoiding repeated insertion attempts, using NGT made of stiffer material and avoiding NGT insertion deeper than that optimum for that size.