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Original Research |
Geriatric Research Education and Clinical Center, Central Arkansas Veterans Healthcare System and Donald W. Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas (B.O., M.F., D.H.S.)
Abbott Laboratories, Ross Products Division, Columbus, Ohio (J.H.)
Address reprint requests to: Dennis H. Sullivan, MD, Geriatric Research Education and Clinical Center (182/LR), Central Arkansas Veterans Healthcare System, 4300 West 7th Street, Little Rock, AR 72205. E-mail: SullivanDennisH{at}exchange.uams.edu.
| ABSTRACT |
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Methods: The study was performed in medical and surgical wards of a university-affiliated Department of Veterans Affairs hospital on 42 patients referred by their attending physicians for tube placement. The newly designed feeding tube was inserted per nares into the stomach using traditional technique. As the tube was advanced, movement of the hand-held steering magnet was designed to guide the tip of the magnetic nasoenteral tube along the lesser curvature of the stomach, through the pyloric sphincter, and into the duodenum. Portable abdominal radiography confirmed the anatomic location of the tube tip.
Results: Fifty-one intubations were performed on 42 subjects. In 45 intubations (88%), tubes passed into the duodenum. Twenty-seven (53%) met criteria for optimal placement in the second portion of the duodenum or distally. Six of 11 tubes (55%) that were not optimally placed were advanced to the distal duodenum on repositioning. Median procedure time for the initial intubations was 30 minutes (interquartile range 1540). Median procedure time for last 10 intubations improved to 13 minutes (interquartile range 520). No complications were related to the procedure.
Conclusions: Enteral feeding tube placement using external magnetic guidance is a promising, novel technique which is deserving of further study.
Key words: enteral nutrition, intubation, gastrointestinal, nutritional support, duodenum
| INTRODUCTION |
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| MATERIALS AND METHODS |
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Equipment used for this study was provided by Ross Products Division (Abbott Laboratories, Columbus, OH) and included specially designed 115 cm long, small-bore (10 and 12 Fr) weighted-tip polyurethane nasoenteral tubes and an external hand-held steering magnet. The tubes were modeled after commercially available weighted-tip nasoenteral feeding tubes, except that each tube contained a small rare earth magnet (37MGOe, Neodymium-Iron-Boron-Dysprosium) in the distal tip instead of a tungsten weight (Fig. 1). The tubes also had markings 54 cm and 80 cm from the tip, which represented the approximate length of tube needed to reach the stomach and then the duodenum in an average adult. Designed for external use to guide tube placement inside the subject, the cylindrical steering magnet (45MGOe, Neodymium-Iron-Boron, Dysprosium) measured four inches in diameter by two inches thick and was encased in a vinyl-coated aluminum frame with an attached handle. The entire apparatus weighed approximately eight pounds.
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After the tube was secured, portable abdominal radiographs were obtained to confirm the tubes position. A tube was considered to be in the small bowel if the tube crossed the midline, then followed the expected curvature of the duodenum, and the outline of the stomach was visible to the left of the tube. In four cases, the anatomical location of the tip could not be determined with certainty from the plain radiographs. In these cases, 20 cc of half-strength gastrografin was injected into the tube and a bedside radiograph was repeated. In all four cases, the exact location of the tube was clearly evident after the use of the contrast.
Based on the original study objectives, the procedure was deemed successful if the weighted tip and the ports (i.e., the distal 4 cm) of the tube were positioned past the pylorus. However, placement of the tube in the second portion of the duodenum or distally was considered optimal. If the x-ray film demonstrated that optimal placement of the tube was not obtained, up to two additional attempts at repositioning the tube were made contingent upon approval of both the subject and the attending physician. Not all subjects agreed to tube repositioning.
The first step in repositioning was to withdraw the tube to the point where the tip was estimated to be just distal to the gastroesophageal junction. The estimated distance the tube was withdrawn was based on measurements taken from the abdominal x-ray film. After the tube was withdrawn the appropriate distance, the external magnet was applied again and the tube was advanced as before.
No prokinetic agents were used during the initial intubations. Because x-ray film showed that four subjects had large dilated stomachs, they were given intravenous erythromycin (3 mg/kg over 10 to 15 minutes) immediately prior to the second or third attempt to intubate the small bowel. The data from these four intubations are presented separately.
The historical control group consisted of subjects recruited into a second intervention trial. Each subject had been randomized to the treatment group and had a nasoenteral feeding tube placed by one of the authors (DHS) on one or more occasions as described previously [2]. Tube placement was accomplished at the bedside without the use of either promotility agents or fluoroscopy. During the placement procedure, the authors attempted to facilitate small bowel intubation using various bedside techniques including patient positioning and spinning the tubes as they were advanced. The tubes utilized were also provided by Ross Products Division of Abbott Laboratories and were identical to the tubes used in the present study except they featured tungsten weights and not magnets in the tips. Aspirates were not checked for pH, but tube position was confirmed using the same radiographic techniques as in the present study.
| RESULTS |
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A total of 51 intubations was performed on the 42 subjects (nine subjects had additional tubes inserted after the prior tube had been inadvertently removed). In 45 (88%) of the insertions, tube passage beyond the pylorus was confirmed by plain radiography (Table 1). However, only 27 cases (53%) met our criteria for optimal placement in the second portion of the duodenum or distally. For those cases in which optimal tube placement was not obtained, an offer was made to reposition the tube. In 13 of these cases, the subject and attending physician consented to the repositioning. In 11 cases, the tube was repositioned without the use of a promotility agent. Six (55%) of these attempts were successful in advancing the tube beyond the first portion of the duodenum (Table 1). For two subjects, whose small bowel could not be intubated after the tube was repositioned, erythromycin was administered prior to an additional attempt at tube repositioning.
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Overall, 41 subjects (98%) met the original study criteria of success (advancement of feeding tube beyond the pyloris without the use of a promotility agent) at least once. The one remaining subject was delirious and became agitated during the initial attempt to pass a feeding tube. The procedure was aborted, and the family declined further attempts at tube passage. The feeding tube was optimally placed (advanced to the second portion of the duodenum or beyond) in 29 subjects (71%).
The median [mean ± SD] procedure time for the initial procedure (prior to any tube repositioning) was 30 [30 ± 18] minutes (interquartile range 15 to 40 minutes) (Table 2). As the research team gained experience, the time needed to complete the procedure decreased considerably. The last 10 intubations performed were completed in a median [mean ± SD] of 13 [16±14] minutes (interquartile range 5 to 20 minutes). Throughout the study, cognitively impaired patients tended to require extra procedure times. It was usually necessary to talk these subjects through the first part of the procedure which involved passing the tube through the nose into the stomach. There were no complications related to the procedure.
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There were 21 subjects (20 males) in the historical control group. Compared with the intervention group, the control subjects were of comparable age (69±12 vs. 74±7, p=.07) and BMI (23±6 vs. 22±4, p=.31). The intervention group differed from the controls in that only one was post-surgical whereas all the controls were recuperating from surgical repair of an acute hip fracture (2% vs. 100% post-surgical, p<.01). Subjects in the intervention group were also more likely to be diabetic (40% vs. 10%, p=.01) or to be on a ventilator (48% vs. 0%, p<.01).
Of the 30 tubes placed in the control group, x-rays obtained at the end of the procedure revealed 27 (90%) to be curled in the stomach, one (3%) to be in the first portion of the duodenum and two (7%) to be in the third portion of the duodenum. Four tubes were repositioned once, and two were repositioned twice. In all cases, the tubes remained in the stomach.
| DISCUSSION |
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To avoid the high cost of tube placement and the need to transport sick patients to procedure rooms, several specially designed nasoenteral tubes and newer bedside techniques of placing the tubes have recently been developed. High rates of success have been reported with several of these techniques [1316]. Marian et al. achieved 15% spontaneous transpyloric passage after 72 hours by using a lateral decubitis positioning technique with subjects on mechanical ventilation [10]. In a study by Stern et al. using weighted-tip tubes, erythromycin administration resulted in 75% passage within one day versus 14% with placebo [15]. Other studies have reported similar results with weighted tip tubes and motility agents [14,17]. Some studies have described bedside techniques with success rates up to 92%; however, such high rates of success have not been confirmed, suggesting that they are probably dependent on the skills of the provider [13].
This study confirms the effectiveness with which the small bowel can be intubated using a magnetically-guided feeding tube. In the original evaluation of this system, Gabriel et al. reported that magnetically-guided tubes were successfully positioned beyond the pylorus on the first attempt in 88% of the cases (37 of 42 insertions) [1]. Nearly half of the tubes (48%) were optimally placed in the second portion of the duodenum or beyond. In this study, an identical rate of post-pyloric tube passage was attained, and 53% of tubes were distal to the first portion of the duodenum. This rate of success was attained with only limited experience using the system. Prior to the start of this study, the investigative team had not utilized the magnetically-guided tube system.
Although not an optimal study design, the inclusion of the historical controls provides additional evidence of the effectiveness of the magnetically-guided feeding tube for intubating the small bowel. Utilizing similar, but non-magnetically guided nasoenteral feeding tubes, the same investigative team had placed only three of 30 tubes (10%) into the small bowel on the initial attempt in a prior study. Despite an unrecorded number of hours dedicated to the task, multiple attempts at repositioning the tubes were uniformly unsuccessful. Factors other than the magnetically-guided tube could have contributed to the difference in the rates of success between the two studies, including the increased experience of the investigative team and differences in the patient populations studied. This possibility will need to be excluded in a subsequent, randomized, controlled trial. There is also a need to examine the length of time that the tubes remain in the small bowel because this was not evaluated in the current study.
In the current study, the median time spent on each procedure was approximately 30 minutes, an acceptable time for bedside manipulation. In their study, Gabriel et al. reported an average length of time for tube placement to be 15 minutes [1]. Two factors may have contributed to the differences in procedure time between the two studies. First, our goal was to maneuver the tip of the tube to the jejunum in all subjects, whereas the initial goal of the earlier study was to achieve postpyloric placement. Secondly, in the beginning of our study, we aggressively attempted to obtain aspirates, only to find that the procedure is extremely time-consuming, especially at the level of the duodenum. Other investigators have noted the same problem. In a study by Harrison et al., the inability to aspirate insufflated air confirmed the transpyloric position of a feeding tube [18]. After we terminated efforts to aspirate, procedure time decreased from 30 minutes to 13 minutes.
During our study, the ultimate goal for each procedure was advancement of the tip of the tube to the distal duodenum or beyond. In several subjects, the tip did not advance further than the first portion of the duodenum on the first attempt at tube placement. This inability to advance the tube was probably due to anatomical differences in the subjects gastrointestinal systems and design limitations of the tube. Some people, especially the elderly, may have large stomachs and a duodenum angling 90 degrees posteriorly [19]. This was possibly the case in four of the subjects with large stomachs on x-ray. In these subjects, intubation of the distal duodenum and jejunal was successful only after erythromycin (3 mg/kg) was administered intravenously over 10 to 15 minutes immediately prior to the procedure. The erythromycin apparently altered the angle within the duodenum or some other anatomic feature of the stomach or proximal small bowel allowing the tube to pass distally. A tube designed with a newer, smaller tip might traverse the corner between the first and second portion of the duodenum more easily and may eliminate the need for administering erythromycin.
| CONCLUSION |
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| ACKNOWLEDGMENTS |
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Received February 7, 2000. Accepted May 26, 2000.
| REFERENCES |
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This article has been cited by other articles:
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S. Roberts, P. Echeverria, and S. A. Gabriel Devices and Techniques for Bedside Enteral Feeding Tube Placement Nutr Clin Pract, August 1, 2007; 22(4): 412 - 420. [Abstract] [Full Text] [PDF] |
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S. Lenart and N. L. Polissar Comparison of 2 Methods for Postpyloric Placement of Enteral Feeding Tubes Am. J. Crit. Care., July 1, 2003; 12(4): 357 - 360. [Abstract] [Full Text] [PDF] |
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