Verification of inefficacy of the glucose method in detecting aspiration associated with tube feedings.

While some authors believe that testing for glucose in suctioned tracheal secretions can be used to detect aspiration of glucose-containing formula, others disagree. Previous evaluative studies of the glucose method's efficacy have lacked adequate statistical power and a gold standard for aspiration. In this animal study, a gold standard for aspiration was used and possessed sufficient statistical power to address the glucose method's sensitivity and specificity. As such, the results from the study provide the clinician with useful data to decide if the glucose method is appropriate for use in clinical settings.

Detection of pepsin in tracheal secretions after forced small-volume aspirations of gastric juice.

BACKGROUND: Detecting small-volume aspirations of gastric contents is an important but difficult task. A potentially useful method for this purpose is assaying tracheal secretions for pepsin, an expected constituent of gastric juice. METHODS: A 2-group experimental design was used. The primary subjects were 161 experimental and 21 control New Zealand white rabbits; 161 acutely ill humans provided the gastric juice used in the project. The animals were anesthetized before being intubated and mechanically ventilated. Three separate boluses of human gastric juice mixed with dye-stained enteral formula were instilled into the experimental animals' tracheas; the 21 control animals received only 0.9% sodium chloride solution. At the beginning of each experiment, 0.4 mL/kg of the substance was infused over a 30-minute period; the infusion was then stopped and 90 minutes were allowed to elapse before endotracheal suctioning was performed. This procedure was repeated at hour 2 and hour 4. After completion of the multiple aspiration portion of the study, 23 additional animals were subjected to a single aspiration of 0.4 mL/kg of a mixture of human gastric juice and dye-stained enteral formula; secretions were obtained at 2 hours, 4 hours, and 6 hours. An immunoassay was used to test for pepsin in all of the tracheal secretions. RESULTS: In the 3-aspiration group, pepsin was found in all of the secretions from 92.5% (149/161) of the experimental animals; in contrast, no pepsin was found in any of the secretions from the 20 control animals. In the single-aspiration group, pepsin was found in all of the tracheal secretions from the 23 animals at 2 hours and 4 hours and 21 of the 23 animals at 6 hours. CONCLUSIONS: The immunoassay used in this animal model study was able to detect pepsin in >90% of the experimental animals' tracheal secretions after multiple or single forced aspirations of gastric juice. The extent to which pepsin can be detected in the tracheal secretions of acutely ill tube-fed humans requires investigation, as does the extent to which clinical outcomes are affected by pepsin-positive tracheal secretions.

Effects of hemoglobin concentration and temperature on the in vitro release of cyanide from sodium nitroprusside.

PURPOSE: This in vitro study was performed to determine whether changes in hemoglobin (Hb) concentration and temperature influenced the amount of cyanide (CN-) released from sodium nitroprusside (SNP). METHODS: Canine whole blood with a Hb concentration of 8.5 to 18.9 g·dl (5.3 to 18.9 mM) was equilibrated with SNP at either 37°C or 25°C, and CN- levels in plasma and red blood cells (RBC) were measured using the microdiffusion method. RESULTS: Changes in Hb concentration and temperature did not have any statistically significant effect on the CN- released from SNP in plasma. On the other hand, CN- levels in RBC decreased with increasing Hb concentrations. CN- levels in RBC were significantly lower at 25°C than at 37°C. CONCLUSION: Though the Hb concentration and temperature changed the amount of CN- released from SNP in RBC, the change observed was not clinically significant.