Middle-molecule clearance at 20 and 35 ml/kg/h in continuous venovenous hemodiafiltration.

BACKGROUND: Of 5 clinical trials testing dose response of continuous renal replacement therapy (CRRT) in acute kidney injury, 2 showed a benefit, 2 showed none, and 1 appeared equivocal. However, blood-membrane interactions may dominate macromolecule transport in continuous venovenous hemodiafiltration, reducing the impact of dose adjustment. The dosing arms in the Acute Renal Failure Trial Network (ATN) study may have delivered similar clearances for middle molecules. METHODS: We simulated the 2 CRRT doses in the ATN study using a synthetic polydisperse macromolecular probe in bovine blood. Clearance of tracers between 10 and 100 kDa molecular weight was measured during 6 h of therapy. RESULTS: Middle-molecule clearance differed by less than 2 ml/min between the 2 dosing arms. CONCLUSION: The CRRT prescription used in the ATN study appears to have achieved dose separation for small molecules while holding middle-molecule clearance nearly constant. This may explain the outcome difference between the ATN study and earlier studies, and suggests subsequent trial designs.

Feasibility and safety of endoscopic evaluation of gastric emptying.

BACKGROUND AND STUDY AIMS: Scintigraphy is the currently accepted method for evaluation of gastric emptying. Although quantitative, this method is complicated, time-consuming, and costly. If a simple endoscopic technique was available for those instances when quantification of an emptying abnormality is not needed, the same clinical information could be obtained in less time and with resource savings. Our aims in this study were therefore to assess the technical feasibility, tolerability, and safety of unsedated transnasal esophagogastroscopy (T-EG) as a technique for qualitative assessment of gastric emptying. METHODS: The study was done in two phases. In the first phase, 18 volunteers (ten men, eight women) underwent T-EG at 4 hours, 5 hours, or 6 hours after ingestion of a standard meal used for scintigraphic evaluation of gastric emptying without radiolabeling. In the second phase, ten volunteers underwent T-EG after scintigraphic imaging had demonstrated complete gastric emptying. RESULTS: Subjects in both phases tolerated the procedure well and completed the study. In the first phase, 13 of 15 volunteers exhibited complete gastric emptying at 6 hours (87%), while two (13%) revealed some particulate matter in the stomach at that time. In the second phase, one of the ten volunteers exhibited a small amount of solid food residue in the stomach despite documentation of scintigraphic complete emptying. CONCLUSIONS: Evaluation of gastric emptying by unsedated T-EG is both feasible and safe. In healthy, asymptomatic individuals, complete gastric emptying of solid food may take as long as 6 hours.

Kinematic and dynamic characteristics of solid pellet movement during the pharyngeal phase of swallowing.

Information on solid particle movement through the pharynx, in addition to its physiologic importance, has relevance to the swallowing of medications in pill form. The purpose of this study was to determine the kinematics of a solid particle during the oral-pharyngeal phase of swallowing. We used a concurrent manometric-videofluoroscopic technique and identified two distinct zones of increasing bolus velocity, one at the tongue base and the other at the pharyngo-upper esophageal sphincter (UES) region. Velocity decreased significantly (p < .05), to 9.0 +/- 1.0 cm/s, while the bolus traversed the area located between the tip of the horizontal epiglottis and the pharyngeal wall. The velocity of the liquid barium bolus head was similar to that of the solid barium pellet. The average bolus tail velocity was relatively constant. The acceleration of the barium pellet was temporally associated with development of an incrementally decreasing pressure distal to the location of the pellet in the hypopharynx and across the UES. In conclusion, the kinematics of a solid particle are similar to those of the head of a liquid bolus, but both are different from bolus tail kinematics. During the pharyngeal phase of swallowing, the area located ahead of the bolus exhibits an incrementally decreasing pressure, caudally. This may facilitate bolus transport and contribute to airway protection.

Esophagopharyngeal distribution of refluxed gastric acid in patients with reflux laryngitis.

BACKGROUND & AIMS: A variety of otolaryngological abnormalities have been attributed to the contact of gastroesophageal refluxate with respective structures of the aerodigestive tract. The aim of this study was to determine and compare the pharyngoesophageal distribution of gastric acid refluxate between patients with proven laryngitis attributed clinically to gastroesophageal reflux and three control groups. METHODS: An ambulatory 24-hour simultaneous three-site pharyngoesophageal pH monitoring technique was used to measure reflux parameters in the pharynx, proximal esophagus, and distal esophagus. RESULTS: Between-group comparison showed no significant difference in the reflux parameters in the distal esophagus between the studied groups. A significantly higher percentage of distal reflux episodes reached the proximal esophagus in the laryngitis group than in the control groups (P < 0.01), and the number of pharyngeal reflux episodes and time of acid exposure were significantly higher in the laryngitis group than in the control groups (P < 0.001). CONCLUSIONS: Compared with normal controls and patients with gastroesophageal reflux disease, pharyngeal reflux of gastric acid is significantly more prevalent and the ratio of proximal to distal esophageal acid reflux episodes is significantly increased in patients with posterior laryngitis. Simultaneous three-site ambulatory pharyngoesophageal pH monitoring may provide supporting evidence when the diagnosis of reflux-induced aerodigestive tract lesions is considered.