Search PubMed⌕ Search

Biomedical subjects

N A Metheny

Publications and source records attributed to N A Metheny.

At least 19 recordsLinked to original sources
PubMed2000

Indicators of postpyloric feeding tube placement in children.

OBJECTIVE: To determine the validity of five indicators (color, pH, and concentrations of bilirubin, pepsin, and trypsin in aspirated gastrointestinal secretions) in predicting postpyloric placement of feeding tubes in critically ill children. DESIGN: Prospective, observational study. SETTING: University teaching hospital. PATIENTS: A total of 96 gastrointestinal aspirates were obtained from 53 children requiring placement of a nasoenteric feeding tube. INTERVENTIONS: Feeding tubes were aspirated by applying suction with a 20-mL syringe. Repeat aspirates from the same patient were obtained on different days. All aspirations were performed within 30 mins of obtaining a radiograph to assess tube position. MEASUREMENTS AND MAIN RESULTS: Aspirates were inspected visually for color. pH and bilirubin concentrations were determined at the bedside by using reagent strips. Pepsin and trypsin concentrations were measured spectrophotometrically in a research laboratory. The sensitivity, specificity, predictive values, and efficiency for each indicator and their 95% confidence intervals were determined based on the position of the feeding tube on the radiograph. Aspirate pH > or =6 had the lowest positive predictive value (76%, range 67% to 85%) but high negative predictive value (94%, range 89% to 99%) for determining postpyloric positioning of the feeding tube. Bilirubin concentration > or =5 mg/dL (> or =86 micromol/L) had the highest positive predictive value (96%, range 91% to 100%) and lowest negative predictive value (88%, range 81% to 95%). Overall efficiency was best for the appearance of a clear yellow aspirate color (93%, range 88% to 98%), pepsin concentration < or =20 microg/mL (94%, range 89% to 99%), and trypsin concentration > or =50 microg/mL (94%, range 89% to 99%). CONCLUSIONS: Simple bedside assessment of gastrointestinal aspirate color, pH, and bilirubin concentration is useful for predicting feeding tube position. Use of these tests may reduce the number of radiographic studies needed to confirm postpyloric positioning. Laboratory-determined pepsin and trypsin concentrations predict tube position with a high degree of accuracy. Development of simple and inexpensive bedside tests for the detection of gastrointestinal enzymes may be useful.

Adolescent↗
PubMed2000

Measurement of gastric residual volume: state of the science.

This literature review substantiates that there is confusion regarding what constitutes excessive gastric residual volume in adult tube-fed patients. Only one research study regarding gastric residuals was located; it indicated that 200 ml for a nasogastric tube and 100 ml for a gastrostomy tube should cause concern. The implications of these findings for adult-health nurses are discussed.

Adult↗
PubMed1999

A survey of bedside methods used to detect pulmonary aspiration of enteral formula in intubated tube-fed patients.

BACKGROUND: The most frequently recommended methods to assess for pulmonary aspiration of enteral formula in intubated, tube-fed patients are (1) adding dye to enteral formulas and observing for dye-stained tracheal secretions and (2) testing tracheal secretions with glucose oxidase reagent strips to detect the presence of glucose-rich formula. Reportedly, the glucose method is more sensitive than the dye method, and the dye method may have greater potential for harm. It is not known if this information has resulted in wider use of the glucose method in practice settings. OBJECTIVES: To describe the frequency with which nurses in intensive care units use the dye and glucose methods to detect pulmonary aspiration of enteral formula in tube-fed, intubated patients. METHODS: One registered nurse in the medical intensive care unit at 285 acute-care facilities was contacted by telephone and asked about the methods used to detect pulmonary aspiration of enteral formula in tube-fed, intubated adult patients. RESULTS: Responses were obtained from 281 facilities. More than 73% of the respondents reported using only the dye method; about 1% reported using only the glucose method. Approximately 13% used both methods; another 13% did not use either method. CONCLUSIONS: The dye method is used far more often than is the glucose method. Two probable reasons are that the dye method is easier to implement, and it is recommended in commonly used basic nursing textbooks.

Adult↗
PubMed1998

Detection of improperly positioned feeding tubes.

This article describes potentially disastrous outcomes associated with failure to determine when nasally inserted feeding tubes are improperly positioned. It also presents information that is important for risk managers to consider when developing protocols for testing placement of newly inserted feeding tubes.

Clinical Protocols↗
PubMed1997

Bedside methods for detecting aspiration in tube-fed patients.

This literature review compares the efficacy of the two most commonly recommended bedside tests for detecting aspiration in tube-fed patients: (1) adding dye to the formula and observing for its appearance in tracheobronchial secretions, and (2) using glucose oxidase reagent strips to test tracheobronchial secretions for glucose-containing enteral formula. The review also describes potential problems and cost associated with each test. Several studies indicate that the dye method is far less sensitive than the glucose reagent method; further, there are anecdotal reports of potential harm to patients when dye is added to tube feedings. Specificity of the glucose method has been challenged by several authors; also, cost is probably greater with this method.

Bronchi↗
PubMed1994

pH testing of feeding-tube aspirates to determine placement.

Although radiologic confirmation of tube placement remains the "gold standard," there is growing evidence that pH testing of feeding-tube aspirates can reduce (although not totally eliminate) reliance on x-rays used for this purpose. This article describes that evidence and tells how it was obtained. Reducing the number of x-rays needed to confirm tube position can have far-reaching financial benefits.

Adolescent↗
PubMed1986

Frequency of nasoenteral tube displacement and associated risk factors.

A pilot study was conducted to describe the frequency with which spontaneous tube displacement occurred in 105 tube-fed patients followed on a prospective basis. In addition, risk factors thought to be associated with tube displacement were studied. Since only about one-third of the tubes were monitored by followup radiographs, the actual occurrence of tube displacement is unknown. On those days when tube position was documented, a comparison of risk factors for spontaneous tube displacement was made with chi-square statistics. Two risk factors, coughing and decreased level of consciousness, were found to occur with significantly greater frequency in patients with displaced weighted nasogastric tubes, while coughing, tracheal suctioning, and upper airway intubation were significant in the dislodgement of unweighted nasointestinal tubes. None of the risk factors were significant in patients with weighted nasointestinal tubes.

Consciousness↗
PubMedDate not supplied

Measurement of glucose in tracheobronchial secretions to detect aspiration of enteral feedings.

OBJECTIVES: To determine (1) the relationship between results from 2 methods to measure glucose in tracheobronchial aspirates, (2) the effect of blood glucose levels on tracheobronchial glucose levels, and (3) the relationship between results from 2 methods to measure glucose in selected enteral formulas. DESIGN: Descriptive. SETTING: Two midwestern acute-care hospitals, a research laboratory, and a clinical laboratory. PATIENTS: Sixty-two acutely ill adult subjects with artificial airways whose secretions required frequent suctioning for therapeutic purposes; 53 of these 62 patients also required capillary blood glucose measurements for therapeutic purposes. OUTCOME MEASURES: Glucose concentrations in tracheobronchial secretions, capillary blood, and selected enteral formulas. INTERVENTION: None. RESULTS: Measures of glucose content made on 75 split samples of tracheobronchial secretions by 2 methods (glucose oxidase reagent strips and a laboratory assay) were highly correlated (ri = 0.94; P < .001) and mean readings were not statistically different (P = .17). Sixty-six capillary blood glucose readings made within 5 minutes of tracheobronchal suctioning correlated poorly with the glucose content in the tracheobronchial aspirates (r = 0.12; P = .36). Glucose concentrations in 22 enteral formulas determined by 2 methods correlated highly (r = 0.95; P < .001). Glucose concentrations were higher with the laboratory assay (259.6 +/- 206.3 mg/dL) than with glucose oxidase reagent strips (188.6 +/- 157.5 mg/dL). CONCLUSION: It appears appropriate to use glucose oxidase reagent strips to estimate glucose concentrations in tracheobronchial fluid. Elevated blood glucose levels apparently do not have a major effect on the glucose content in tracheobronchial fluid. Although mean glucose concentrations in the 22 formulas were higher with the laboratory assay, the readings were sufficiently similar to allow using glucose oxidase reagent strips to give a good estimation of the formulas' glucose content.

Adult↗
PubMedDate not supplied

pH and concentration of bilirubin in feeding tube aspirates as predictors of tube placement.

BACKGROUND: Currently available bedside methods for determining feeding tube placement often provide inconclusive results. Therefore, additional data are needed to assist nurses in making decisions regarding tube location. OBJECTIVES: To describe the usual concentration of bilirubin in aspirates from newly inserted feeding tubes and to determine the extent to which these measures can contribute to pH alone in correctly predicting feeding tube location. METHODS: Gastrointestinal samples for concurrent pH and bilirubin testing were obtained from adult, acutely ill patients with newly inserted small-bore feeding tubes (nasogastric, n = 209; nasointestinal, n = 228) within 5 minutes of radiographs taken to determine tube location. Respiratory samples were tested (tracheobronchial, n = 126; pleural, n = 24). pH was measured with a pH meter, and bilirubin content was assayed spectrophotometrically. Results from the pH and bilirubin tests were compared with tube location as determined by radiography. RESULTS: Mean pH levels in the lung (7.73) and intestine (7.35) were significantly higher than the mean pH level in the stomach (3.90; p < .001 for each comparison). Mean bilirubin levels in the lung (.08 mg/dl) and stomach (1.28 mg/dl) were significantly lower than the mean bilirubin level in the intestine (12.73 mg/dl; p < .001 for each). By visually inspecting distribution overlap and mean differences by tube site, results were dichotomized so that a combination of pH and bilirubin values could be used to develop a predictive algorithm. A pH of >5 and a bilirubin value of <5 mg/dl correctly identified all respiratory cases, whereas a pH >5 coupled with a bilirubin level of > or =5 mg/dl correctly identified three fourths of the intestinal cases. A pH of < or =5 coupled with a bilirubin value of <5 correctly identified more than two thirds of the gastric cases. CONCLUSIONS: Preliminary laboratory-based data indicate that appropriate use of the proposed algorithm could significantly reduce the number of x-rays needed to exclude respiratory placement and to distinguish between gastric and intestinal placement.

Adolescent↗
PubMedDate not supplied

Development of a reliable and valid bedside test for bilirubin and its utility for improving prediction of feeding tube location.

BACKGROUND: The addition of laboratory bilirubin readings to an algorithm based on pH alone improves prediction of feeding tube location; although reliable pH-teststrips are available, there is no bedside test to measure bilirubin in feeding tube aspirates. OBJECTIVES: This study was designed to test the efficacy of a bilirubin teststrip with a newly developed scale in measuring the bilirubin content in feeding tube aspirates, and to determine the effectiveness of a combination of readings from pH and bilirubin teststrips in predicting feeding tube location. METHODS: A total of 631 gastrointestinal specimens for concurrent pH and bilirubin testing were obtained from adult, acutely ill patients with newly inserted feeding tubes (nasogastric, n = 328; nasointestinal, n = 303) within 5 minutes of radiographs taken to determine tube location. In addition, 225 respiratory specimens were tested. Bilirubin was measured with a teststrip incorporating a newly developed colorimetric visual bilirubin (VBIL) scale, and by a laboratory assay. pH was measured with a teststrip and a pH-meter. Results from the bilirubin and pH tests were read by research assistants and staff nurses and compared with tube location as determined by radiography. RESULTS: The correlation between readings made from the 5-point VBIL scale and the trimmed laboratory bilirubin was 0.93, with dichotomized readings correlating 0.87 and kappa equal to 0.86. A pH greater than 5 and a bilirubin less than 5 mg/dL successfully identified 100% of the 225 respiratory cases. In the category of pH 5 or less and bilirubin less than 5 mg/dL, 98% of the cases were gastric cases. In the category of pH greater than 5 and bilirubin 5 or higher mg/dL, nearly 88% of the cases were intestinal cases. CONCLUSIONS: The newly developed VBIL scale is effective in determining the bilirubin content in feeding tube aspirates. Furthermore, compared with predicting tube location from pH-paper alone, dichotomized readings from the VBIL scale/bilirubin teststrip used in combination with a pH-teststrip improved the ability to differentiate between respiratory and gastrointestinal tube placement, as well as between gastric and intestinal tube placement. Refinement of the VBIL scale is indicated to increase its accuracy.

Adolescent↗
PubMedDate not supplied

pH and concentrations of pepsin and trypsin in feeding tube aspirates as predictors of tube placement.

BACKGROUND: The purpose of this study was to determine the extent to which pepsin and trypsin concentrations in feeding tube aspirates, in addition to pH, contribute to predicting feeding tube position. METHODS: Aspirates from 742 feeding tubes (nasogastric, n = 343; nasointestinal, n = 399) were tested for pH and enzyme concentrations. Also tested were aspirates from two feeding tubes inadvertently positioned into the lung (one in the pleural space and one in the tracheobronchial tree) and 146 samples of tracheobronchial and pleural fluids collected by other methods. Enzyme assays were conducted in a research laboratory. Results of the pH and enzyme tests were compared with radiologic reports of tube location. RESULTS: Gastric fluid had a mean low pH (4.06), a high mean pepsin concentration (349.1 micrograms/mL), and a low mean trypsin concentration (19.3 micrograms/mL). In contrast, intestinal fluid had a mean high pH (7.40), a high mean trypsin concentration (143.0 micrograms/mL), and a low mean pepsin concentration (24.2 micrograms/mL). Respiratory samples also had a high mean pH (7.89) but contained little or no pepsin or trypsin. Using a logistic regression equation with all three variables to differentiate between respiratory and gastrointestinal placement, it was possible to correctly classify 100% of the respiratory cases and 93.4% of the gastrointestinal cases. Another equation used to differentiate between gastric and intestinal sites was able to classify correctly 91.2% of the gastric cases and 91.5% of the intestinal cases. CONCLUSIONS: The results clearly indicate that laboratory-determined enzyme concentrations in feeding tube aspirates are helpful in predicting tube location. Thus, it is desirable that inexpensive, simple bedside tests be developed so that they can be used in conjunction with pH measurements to help predict tube position.

Enteral Nutrition↗