An unusual complication of reinforced tube reuse.

Sir,

A variety of surgical procedures such as head and neck, craniotomy and back surgeries involve positioning the patient in a way that precludes the anesthesiologist's access to the airway. In these cases it is common to intubate the trachea with a reinforced endotracheal tube (ETT) that is designed to allow bending and not get obstructed.[1] However, certain problems may also be associated with them, which include collapse of the ETT inside the inflated cuff, obstruction caused by folding of the inner wall around the connector or double layering of the cuff preventing deflation, they usually require stylet for insertion, nasotracheal intubation is difficult and these ETT cannot be shortened.[23] We report an unusual complication after reuse of a reinforced tube.

A 65-kg, 45-year-old man, in American Society of Anesthesiologists grade I with intervertebral disc prolapse (L4-5) was scheduled for discetomy. He was administered general anesthesia as per the standard protocol of our institute. Endotracheal intubation was done using 8.5 mm internal diameter (ID) reinforced ETT (Safety Flex, Mallinkrodt Medical, Athlone, Ireland). Normal breath sounds were confirmed equally in both lungs after putting the patient in prone position and connected to ventilator with the following settings tidal volume of 600ml,respiratory rate of 12 breaths/min and I:E ratio of 1:2. Peak inspiratory pressure reached 20 cm H2O. Approximately 45 min after insertion of ETT, peak airway pressure gradually increased to 50 cm H2O and the tidal volume decreased. On auscultation equal and decreased bilateral breath sounds were heard. Ventilation with self-inflating bag experienced high airway resistance. Tube blockade by mucus was suspected. A16F suction catheter was passed through the ETT but it did not pass beyond a distance of 8 cm and there was no mucus on suction. We suspected compromise in the patency of the ETT. The ETT was removed and the trachea reintubated with another new 8.5 mm ID-reinforced ETT (Safety Flex, Mallinkrodt Medical, Athlone, Ireland). All the ventilator variables returned to the basal level. Rest of the operative course was uneventful. Inspection of the tube showed a longitudinal transparent halo along the length of the tube on the outer surface [Figure 1]. The inner view showed a detachment of the inner layer and a bleb was formed which partially occluded the lumen. The 5-cm long bleb was located 8 cm from the proximal end. A fiberscope was used to obtain a picture of the bleb from the inside of the tube [Figure 2].

Figure 1

Longitudinal transparent halo on the external surface of the flexometallic tube

Figure 2

Endoscopic view of the flexometallic tube showing the bleb formation

We routinely reuse the armored ETT in our hospital after autoclaving or ethylene oxide (ETO) sterilization, although the manufacturer recommends them as single-use tubes. We noticed increase in inspiratory pressure and decrease in tidal volume after 45 min of procedure which made us suspect obstruction. Obstruction of ETT by mucus, blood or a kink is not uncommon, whereas obstruction by a foreign body is a rare event.[45] The recommended maneuvers for a suspected obstruction of ETT include passing a suction catheter through the tube and performing a fiberoptic examination.[5] Fiberoptic inspection of the tube would have revealed the cause of obstruction immediately.

Nitrous oxide exposure and diffusion was the probable cause of the expansion of the tube defect in this case,[67] as during the initial 45 min of the procedure no problems were noted. Munson et al., described the expansion of the bubble by directing nitrous oxide (70%) in oxygen through the lumen at a rate of 4 L/min.[8] It takes 45 min for the expansion, however, it disappears gradually after exposure to room air. In our case, dissection of the ETT was probably due to two factors. Re-sterilization by autoclaving resulted in the formation of bubble between the two layers. Storage of ETT close to a warm source, such as the autoclave, may have been an additional factor.[7] Cutting costs by re-using ETT which are not meant to be re-autoclaved is likely to be at the expense of patient safety and therefore cannot be justified.[5]

We conclude that the presence of a reinforced tube is not a guarantee of a patent airway. Before reusing armored ETT after autoclaving, their internal and external surface must be inspected meticulously, for detachment and transparent halo respectively, to prevent such complications.