Studies on live neonates concerning proper tube feeding placement are lacking, probably due to the difficulty to offer ethical ways to analyze tube placement and their complications. Therefore, we used dead neonates in order to give new insights on tube feeding management. This study shows that appropriate placement of the tube can be performed under ultrasonography control: stomach wall deformation and stomach volume could be visualized accurately. Furthermore no difference was found between frozen and fresh puppies, however further validation is required in live animals.
The description of tube placement using BENT ¾, STRAIGHT, BENT or NEMU is aimed to assess potential risks on the integrity of the gastric wall and to determine whether the tube is placed in the oesophagus, in the stomach or further. It is not known whether oesophageal or gastric feeding have a relationship with increased regurgitation risks. Both techniques are used in adults (28) and no statistical difference in regurgitation rates was found in adult dogs (29). The tips of feeding tubes are mostly presented with lateral openings. Using a tube with the flared end trimmed may reduce regurgitation risks, as previously suggested (7). Reduced contractility of the gastrointestinal tract was observed in human preterm neonates (46, 47), and in canine neonates, with a progressive increase of contractility 3–7 days after birth (48). Canine gastrointestinal maturation is a quick process implying that significant changes in the gastrointestinal tract may occur within the first days of life, which is why this study was limited to less than one day old neonates.
BENT was the only measurement allowing gastric intubation in 100% of cases; therefore, this length should be used for the indication of stomach emptying to reduce diaphragmatic pressure during neonatal resuscitation. However, concerning injury risks, tube placement with BENT is not always harmless since BENT exceeded the MAX US1, MAX US2, and MAX VISUAL in 19, 8 and 2 neonates respectively (Table 1). Using rigid tubes such as 8 Fr adult feeding tubes may induce stomach damage to the neonates (Fig. 3d). It should be self-evident that forcing the tube to go further than MAX VISUAL breakpoint should be avoided. It induced stomach perforation in 4 kittens and looping in 8 kittens (Fig. 3c) as previously described as complications (2, 6). The authors do not recommend using rigid tubes such as adult 8 Fr adult feeding tubes with BENT on neonates, although the incidence of gastric perforations in this study may be overestimates due to autolysis: prevalence of perforations is considered to be 1.1% in low birth weight human neonates (21). Using softer tubes (2, 7) may reduce the risks for complications such as stomach injuries, although looping, regurgitation or kinking of the tube remain possible other risk factors (2, 6). For the feeding of the neonates STRAIGHT seems more suitable. It is mainly found close to the area of the cardia with 32/53 cases found in the stomach (60%). BENT ¾ might be used, even if it is found most often in the oesophagus with 45/53 cases (85%). Concerning risks for injuries, STRAIGHT exceeded MAX US1 in three cases, while BENT ¾ never exceeded MAX US1. The authors conclude gastric injuries are minimized using either of these two measurement techniques, although prevalence of regurgitations should be assessed in live animals. Measurements with NEMU are not appropriate in puppies or kittens compared to human babies, because of an excessive length of intubation (Table 1). Concerning the diameter to be used for tube feeding, some recommend 5 Fr diameter for < 300 g neonates and 8 Fr for > 300 g animals (22–24). Others discourage the use of small size catheters due to the increased risks for looping (2) some recommend to use the largest tube that passes easily (5). Further studies are needed on that subject in order to reach a consensus.
During measurements performed in this study, it became clear that without ultrasound control, a residual risk always remains with tube insertion. Since the position of the cardia can be predicted very well using the bodyweight, as shown by the strong correlation rate in cats (r2 = 65%) (Fig. 6) and in dogs (r2 = 81%) (Fig. 7), we would recommend to use weight-based formulas to determine the tube length. Whenever this formula is used in puppies and kittens, values exceeding maximum measurements are reduced compared to BENT (Table 1), which shows that this formula may avoid extreme measurements, which are precisely the ones that might induce trauma.
Maximal stomach volume was found to be 1.2% and 1.9% of the bodyweight of feline and canine neonates. This is in apparent contradiction to most the guidelines indicating a maximal amount of milk given per single feeding of 4 to 5 ml / 100 g of bodyweight (6, 7, 12, 22, 23), but is in agreement with data found on 4 newborns in the original study of Andersen (49). Maximal stomach size in neonates is more than half smaller than older ones. Safety rules should be adapted according to age, in order to avoid overfeeding and regurgitation. Nevertheless, our model has several limitations. The loss of tonicity of the pyloric sphincter, the flaccid oesophagus, the changes of compliance and autolysis are parameters different to live animals. Many morphologic variations may be observed among canine breeds, the findings may not be representative to all the canine breeds. BENT and STRAIGHT measurements were performed on dead neonates, while BENT ¾ was calculated based off the values of BENT. The variations found in this study are therefore underestimated compared to live, moving animals, increasing potential discussed risks for injuries in vivo. Using the herein presented formula, the probability of being at the preferred position is increased, thus reducing the risks to the neonate.