Examination of an aspirate from a gastrointestinal feeding tube can help identify the location of the tip. This can help reduce the need for a radiographic examination to confirm placement. The authors are from the Childrens' Hospital Michigan, Wayne State University and the St Louis University.
Parameters analyzed:
(1) appearance of aspirate and color
(2) pH
(3) bilirubin
(4) pepsin
(5) trypsin
Comparison of parameters in gastric and duodenal aspirates:
(1) color: Bile is a golden yellow as if flows into the duodenum, but turns green on exposure to gastric acid. Ideally duodenal fluid is clear and yellowish. Gastric fluid may show a variety of colors (colorless, white, tan, green, bloody or brown) and range from clear to turbid in appearance.
(2) pH: Gastric fluid is usually acidic but a proportion of the population may have a gastric pH > 6 due to a variety of factors, including medications and the presence of enteral feeding formula.
(3) bilirubin: Normally bilirubin should be absent from the gastric aspirate.
(4) pepsin: Pepsin is higher in gastric aspirates than in duodenal aspirates.
(5) trypsin: Trypsin is present in pancreatic secretions.
Factors affecting parameters:
(1) Feeding affects each of the parameters, with efficiency for each parameter reduced when the aspirate is obtained within 4 hours of a feeding.
(2) Gastroduodenal reflux may introduce duodenal fluid into the stomach, causing bile and trypsin to appear in the gastric aspirate.
Performance of Parameters for Identifying Duodenal Fluid
|
Parameter |
Sensitivity (when unfed) |
Specificity (when unfed) |
|
clear yellow color |
96% (91 - 100) |
93% (87 – 99) |
|
pH >= 6 |
96% (91 – 100) |
81% (72 – 90) |
|
bilirubin >= 5 mg/dL |
84% (74 – 94) |
97% (92 – 100) |
|
pepsin <= 20 µg/mL |
100% |
97% (93 – 100) |
|
trypsin >= 50 µg/mL |
96% (91 – 100) |
97% (93 – 100) |
from Table 2, page 2964
|
Parameter |
Positive Predictive Value (unfed) |
Negative Predictive Value (unfed) |
Efficiency (when unfed) |
|
clear yellow color |
89% (82 – 96) |
98% (94 – 100) |
94% (88 – 100) |
|
pH >= 6 |
75% (65 – 85) |
97% (93 – 100) |
87% (79 – 95) |
|
bilirubin >= 5 mg/dL |
94% (87 – 100) |
90% (81 – 100) |
92% (86 – 100) |
|
pepsin <= 20 µg/mL |
96% (91 – 100) |
100% |
98% (94 – 100) |
|
trypsin >= 50 µg/mL |
96% (91 – 100) |
97% (91 – 100) |
97% (91 – 100) |
Best overall efficiency for a postpyloric placement is:
(1) clear yellow fluid
(2) pepsin <= 20 µg/mL
(3) trypsin>= 50 µg/mL
Specialty: Nutrition, Gastroenterology, Critical Care
ICD-10: ,
