Video-rate terahertz digital holographic imaging system.

Terahertz (THz) imaging has been demonstrated in numerous applications from medical to non-destructive evaluation (NDE), but current systems require expensive components, provide slow frame-rates and low resolutions. THz holography offers a potentially low-cost, high-performance alternative. Here we demonstrate the first full video-rate THz digital holography system at 2.52 THz (118.8 µm) using low-cost optical components. 2D digital reconstructions of samples are performed at frame-rates of 50 Hz - an order of magnitude higher than previous systems, whilst imaging of samples concealed in common packaging types demonstrates suitability for NDE applications. A lateral resolution of 250 µm was determined using a 1951 USAF target.

VersaStep trocar hernia rate in unclosed fascial defects in bariatric patients.

OBJECTIVE: Use of the VersaStep trocar system (US Surgical, Norwalk, CT) has the perceived advantage of minimal trocar-related hernias in patients undergoing Roux-en-Y gastric bypass surgery (RYGB). We performed a retrospective review of our last 747 consecutive operative procedures using these trocars. METHODS AND PROCEDURES: The patient population was 747 consecutive patients who underwent laparoscopic RYGB at Duke University Health System Weight Loss Surgery Center from January 2002 through April 2005. A total of 3735 radially expanded trocar sites were used. VersaStep trocars were used in all cases. The port configuration included one supraumbilical Hasson port, two 12-mm ports, and three 5-mm ports. The Hasson port was closed with a figure-of-eight number 1 Polysorb suture. All other trocar sites had no fascial closure. Intestinal anastomoses were created with a linear stapler in all of the laparoscopic cases, with hand suturing of the residual enterotomy. The fascial incisions were therefore not extended to accommodate an EEA stapler. The charts were reviewed for occurrence of subsequent trocar site hernias. RESULTS: There were no hernias at any of the VersaStep trocar sites-an incidence of 0%. There were nine incisional hernias at the Hasson port site which later required surgical repair-an incidence of 1.20%. CONCLUSIONS: There were no hernias detected at any of the 1494 12-mm or 2241 5-mm VersaStep trocar sites, despite lack of suture closure. At the Hasson port site, there was a hernia incidence of 1.20%. In the bariatric RYGB population, routine suture closure of the fascia or muscle is not necessary when using radially expanding VersaStep trocars.

The effects of bone density and disc degeneration on the structural property distributions in the lower lumbar vertebral endplates.

In this study, we hypothesized that vertebral bone density and disc degeneration would affect the structural property distributions of the lower lumbar vertebral endplates (L3-L5). The results may have implications for improving interbody implant designs to better resist subsidence. A 3 mm diameter hemispherical indenter was used to perform indentation tests at 0.2 mm/s to a depth of 3 mm at 27 standardized locations in 55 bony endplates of intact human lumbar vertebrae (L3-L5). The resulting load-displacement curves were used to extract the failure load and stiffness of each test site. Bone density was measured using lateral DEXA scans. Disc condition was determined using a four-point grading scale. Three-way analyses of variance were used to analyze the relationships between the data. The overall failure load decreased with bone mineral density (BMD) in the superior (p < 0.0001) and inferior (p = 0.011) lumbar endplates. In both endplates, the posterolateral regions were significantly stronger than more central regions. With increasing BMD, this difference became more pronounced in the superior endplates only (p = 0.005). Increased disc degeneration was associated with an overall failure load decrease in the inferior lumbar endplates (p = 0.002). The strength in the central regions of the superior endplates was reduced with increasing degeneration, but this was not observed peripherally (p = 0.001). Stiffness magnitude or distribution was not significantly affected by BMD or disc degeneration. The locations of the strongest regions of the endplate did not change with either bone density or disc degeneration. This implies that implant shapes designed using the basic structural property maps for the L3-L5 endplates are appropriate for use in patients with a wide range of pathologies, even though overall failure loads are generally lower in patients with reduced bone density and greater degrees of disc degeneration.

Mapping the structural properties of the lumbosacral vertebral endplates.

STUDY DESIGN: A biomechanical investigation using indentation tests in a human cadaveric model to seek variation in the structural properties across the lower lumbar and sacral endplates. OBJECTIVES: To determine 1) if there are regional differences in endplate strength and 2) whether any differences identified are affected by spinal level (lumbar spine vs. sacrum) or endplate (superior vs. inferior). SUMMARY OF BACKGROUND DATA: It has been postulated that some regions of the vertebral body may be stronger than others. Conclusive data, either supporting or disproving this theory, would be valuable for both spine surgeons and implant designers because one mode of failure of interbody implants is subsidence into one or both adjacent vertebrae. METHODS: Indentation tests were performed at 27 standardized test sites in 62 bony endplates of intact human vertebrae (L3-S1) using a 3-mm-diameter, hemispherical indenter with a test rate of 0.2 mm/sec to a depth of 3 mm. The failure load and stiffness at each test site were determined using the load-displacement curves. Three-way analyses of variance were used to analyze the resulting data. RESULTS: Both the failure load and stiffness varied significantly across the endplate surfaces (P < 0.0001), with posterolateral regions being stronger and stiffer than the central regions. Characteristic distributions were identified in the lumbar superior, lumbar inferior, and sacral endplates. The failure load distributions were found to differ in 1) the superior lumbar and sacral endplates (P = 0.0077), 2) the inferior lumbar and sacral endplates (P = 0.0014), and 3) the superior and inferior lumbar endplates (P < 0.0001). The sacral and inferior lumbar endplates were both found to be stronger than the superior lumbar endplates (sacrum, P = 0.054; inferior, P = 0.008) but were not themselves significantly different (P = 0.89). CONCLUSIONS: Highly significant regional strength and stiffness variations were identified in the lumbar and sacral endplates. The center of the bone, where implants are currently placed, is the weakest part of the lumbar endplates and is not the strongest region of the sacral endplate.

Use of electrocardiogram to position right atrial catheters during surgery.

OBJECTIVE: This study evaluated the accuracy of placing right atrial catheters using an electrocardiographic (ECG) technique. SUMMARY BACKGROUND DATA: Placement of right atrial catheters for vascular access is a common operative procedure. Accurate placement is essential for proper function. Previous placement techniques have used fluoroscopy, which is both time consuming and hazardous. METHODS: The accuracy of placement of 1236 right atrial catheters using an ECG technique was compared to placement of 586 catheters using fluoroscopy between March 1991 and November 1995. In the ECG technique, the catheter was flushed with sodium bicarbonate. A sterile left-leg ECG lead was attached to the catheter with the other ECG leads applied normally. On advancing the catheter through the superior vena cava, the P-wave amplitude (lead II) increased in negative deflection until greater than the QRS complex. Passing the sinoatrial node, the P-wave developed an initial positive then negative deflection. The catheter was positioned so the P-wave was biphasic, representing a position midway between the sinoatrial and atrioventricular nodes. For the fluoroscopic technique, catheters were positioned under direct observation just within the atrium estimated from cardiac contour. Use of contrast was optional if atrial anatomy was unclear. RESULTS: Postoperative portable chest x-rays showed the ECG method to position the catheter tip within the right atrium just as accurately (average, 1.9 +/- 1.3 cm) as with the use of fluoroscopy (average, 1.1 +/- 1.6 cm). The ECG method eliminated an average of 20 seconds of radiation exposure, an average of 3.0 minutes operating room time (p < 0.04), avoided all risks of contrast dye, and saved $279.10 per case. CONCLUSIONS: The ECG method is a satisfactory alternative to that of fluoroscopy for placement of long-term central venous catheters into the right atrium.

Total parenteral nutrition alters NPY/PYY receptor levels in the rat brain.

The regulation of appetite and satiety is complex and may involve peptide mediators such as cholecystokinin (CCK) and neuropeptide Y (NPY). Studies have indicated that calories administered enterally and parenterally impact on feeding, and possibly via the release of such mediators. Recent data from our laboratory have shown that total parenteral nutrition (TPN) reduces sham feeding in dogs by 50%. We hypothesized that TPN may alter feeding via an NPY-mediated mechanism. To test our hypothesis, we examined the effect of continuous administration of TPN on NPY receptor levels in the rat brain. Rats were surgically prepared with intravenous catheters. After 72 h of TPN infusion, the rats were anesthesized with sodium pentobarbital and their brains were removed. Neuropeptide Y receptor density was assessed by autoradiography in the paraventricular nucleus, olfactory cortex, dentate gyrus, and thalamus. These results were compared to the control group receiving intravenous saline. A third group receiving enteral nutrition was examined as well. Neuropeptide Y receptor numbers were significantly increased in the paraventricular nucleus of rats receiving TPN compared to the groups receiving intravenous saline or enteral nutrition. We conclude that continuous parenteral nutrition significantly increases NPY receptor density in the rat brain suggesting that TPN may impact feeding via the regulation of NPY receptor-mediated effects.

Malabsorption associated with surgical procedures and its treatment.

Signs and symptoms of malabsorption after surgical procedures can be subtle and recognized late. This article reviews some of the more common surgical procedures potentially associated with malabsorption and suggests techniques of nutrition intervention. Early recognition, and preferably preventative care, should result in improved patient outcome.

Prospective evaluation of the safety and efficacy of laparoscopic jejunostomy.

We prospectively assessed the safety and efficacy of laparoscopic jejunostomy done by 11 surgeons in 8 medical centers using the T-fastener technique. In all, 23 men and 13 women aged 19 to 84 (mean, 59) years required enteral feeding, but could not undergo gastrostomy and had no contraindication to laparoscopy. Of these patients, 12 had head and neck cancer and 11 had neurologic swallowing dysfunction. The procedure took 25 to 180 minutes (mean, 75). Three (8%) early cases were converted to open jejunostomy because of accidental enterotomies caused by inappropriate techniques that were avoided in later cases. Minor technical problems, such as passing a needle through the back wall of the jejunum, occurred in 7 patients, but they were easily corrected and produced no complications. Feedings were routinely begun within 24 hours of the surgical procedure. All jejunostomy catheters functioned well. This is a safe and effective technique when done by experienced laparoscopic surgeons, and serious complications are rare.

Nutritional support in critically ill patients.

OBJECTIVE: The author reviews the newer nutritional substrates in use or under investigation for enteral and parenteral nutrition. Management of the critically ill patient remains a significant challenge to clinicians, and it is hoped that dietary manipulations, such as those outlined, may augment host barriers and immune function and improve survival. SUMMARY BACKGROUND DATA: The role of nutrition in patient well-being has long been recognized, but until the past 25 years, the technology to artificially provide nutrients when patients could not eat was not developed. With current, new methods for enteral and vascular access, patients can be fed nonvolitionally with little difficulty. Continued efforts have been directed toward identifying optimal feeding formulations, which have resulted in a multitude of commercially available products. In the past several years, attention has been turned to evaluation of four specialized nutrients and the use of other substrates as pharmacologic agents. METHODS: Pertinent laboratory and clinical data were reviewed to present the pros and cons for each nutritive substrate. CONCLUSIONS: Medium-chain fatty acids, branched-chain amino acids, and glutamine have been shown to be of clinical benefit and should be in common use in the near future. Short-chain fatty acids still are under investigation. Albumin, vitamins E and C, arginine, glutamine, and omega-3 fatty acids show great promise as pharmacologic agents to manipulate the stress response. Nucleotides remain investigational. CONTENTS SUMMARY: The application of some new nutritional substrates for use in critically ill patients, both as caloric sources and as pharmacologic agents, are reviewed.

Effects of enteral feeding products on survival from Escherichia coli peritonitis.

Male Fischer 344 rats were orally fed one of four diets (Osmolite HN, Alitraq, Impact, and Purina rodent chow). After 6 days, jejunal mucosal nitrogen content and thickness were normal in all groups. After 7 days, challenge with Escherichia coli intraperitoneally demonstrated no difference in survival for any dietary group. In a second study, acute protein-calorie malnutrition was induced by administering 5% dextrose orally for 10 days. Animals were refed for 7 days with one of the four diets. Serum albumin concentrations and intestinal mucosal nitrogen content and thickness returned to normal with each refeeding program. Challenge with E. coli after 7 days of refeeding, however, again demonstrated no difference in survival for any dietary group. Specialized enteral feeding products, containing additional amounts of arginine, glutamine, glutamate, RNA, and omega-3 fatty acids, are no more effective than a standard enteral feeding product or rat chow in maintaining intestinal anatomy or restoring anatomy following fasting. Furthermore, we found no survival advantage for the specialized products following E. coli peritonitis.

Duke procedure for super obesity: preliminary report with 3.5-year follow-up.

BACKGROUND: Super obese patients pose a major health care problem because their obesity is associated with high risks of morbidity and even death. Neither dietary programs nor surgery results in significant or lasting weight loss. Presented here is a new surgical approach, combined with home infusion therapy, that offers effective weight loss with maintenance for 3.5 years. METHODS: Eight super obese patients (252% +/- 19% ideal body weight; 62.7 +/- 5.6 kg/m2 body mass index) underwent near total intestinal bypass anastomosing the proximal 25 to 30 cm of jejunum to the transverse colon. A right atrial catheter was placed for home infusion of necessary fluids, minerals, vitamins, and protein. After desired weight loss was achieved, the jejunocolostomy was taken down with construction of a vertical banded gastroplasty to assist in weight maintenance. RESULTS: An average of 1.5 kg/week was lost. Seven patients lost to an average of 114% +/- 14% ideal body weight (29.0 +/- 2.9 kg/m2 body mass index) after 333 to 556 days. An eighth patient is still losing weight. Weight loss was due mainly to loss of body fat and water. After takedown of the jejunocolostomy and construction of a vertical banded gastroplasty in seven patients, weight loss has been maintained for up to 1218 days. CONCLUSIONS: A new operative approach for super obese patients offers safe and effective weight loss to any desired goal. Subsequent conversion to a vertical banded gastroplasty has so far afforded maintenance of the weight for up to 3.5 years.

A case of retrograde jejunoduodenal intussusception caused by a feeding gastrostomy tube.

A case is presented of migration of a gastrostomy feeding tube (Foley type) through the pylorus with duodenal obstruction and subsequent retrograde intussusception. Although feeding tube migration is not uncommon, retrograde intussusception of the jejunum into the duodenum is rare. In this case, surgery was required with resection of a segment of necrotic bowel. Recommendations are given for treatment of this unusual complication with emphasis on its avoidance through use of a retaining bar or disc at the tube's skin exit site.

Nutrition care of patients with acute and chronic respiratory failure.

Nutrition is intimately linked to pulmonary function and an understanding of these relationships have therapeutic utility. Malnutrition is known to be associated with impaired mechanical function of the lung in both chronic and acute respiratory insufficiency. Refeeding results in improvement in functional characteristics and may be critical in the weaning of patients from mechanical ventilation. In contrast, overfeeding may result in an increased ventilatory demand resulting in the inability to wean from respiratory support. This article considers the background as well as recommendations for the nutritional care of patients with acute and chronic respiratory failure.

Effect of glutamine-supplemented total parenteral nutrition on recovery of the small intestine after starvation atrophy.

Intestinal atrophy was induced in rats by infusion of 5% dextrose for 7 days with only oral water allowed. Compared with control animals fed standard rat chow (Purina Mills, St. Louis), the starved animals lost 30.5% of their initial body weight, 34.7% mucosal wet weight, 68.3% mucosal nitrogen content, 36.7% mucosal thickness, and 38.6% villous height and had variable losses of mucosal disaccharidase activities. Three groups of depleted rats were then refed with different regimens. One group was refed with standard Purina rodent chow (n = 15); a second group with a standard total parenteral nutrition (TPN) solution containing 16% glucose, 2.8% fat, and 4.25% standard amino acids (Travasol 8.5%, Baxter Healthcare Corporation, Deerfield, IL) (n = 15); and the third group with a TPN solution of 16% glucose, 2.8% fat, 2.75% standard amino acids, and 1.5% glutamine (n = 15). After 7 days of refeeding, rats were killed to determine the degree of intestinal recovery. Animals refed with standard TPN solution showed no significant recovery of intestinal mucosal weight, mucosal nitrogen content, villous height, mucosal thickness, or mucosal disaccharidase activities. Animals refed with glutamine-supplemented TPN solution demonstrated significant recovery of all parameters but not back to normal. Oral rodent chow completely restored intestinal anatomy and function. The addition of glutamine to TPN solutions significantly improved recovery of the intestine from starvation atrophy, and additional efforts to make it commercially available are indicated. This study again confirms the preferable use of a regular oral diet when clinically feasible and safe.

Percutaneous endoscopic gastrostomy. Initial placement by single endoscopic technique and long-term follow-up.

Of 598 patients, 595 underwent placement of a percutaneous endoscopic gastrostomy (PEG) tube using a single endoscopy technique and a polyurethane gastrostomy tube. Primary indications were altered mental status and dysphagia. All procedures were performed in the operating room, with 74 patients receiving general anesthesia and 524 intravenous sedatives with or without topical anesthesia. Average operating room time was 34 minutes. Of 208 patients with prior intra-abdominal surgery, 207 underwent successful placement. The overall complication rate was 4.9%, with a major complication rate of 1.3%. One death occurred from presumed leakage at the gastrostomy site with peritonitis. One hundred twenty patients subsequently died of causes unrelated to the gastrostomy tube after 75 +/- 164 days (range, 1 to 972). One hundred fifty-four patients recovered an adequate oral diet and had the PEG removed after 169 +/- 244 days (range, 6 to 1337). The remaining 319 patients continued to use their gastrostomy tube for 1532 +/- 411 days (range, 134 to 2251). The polyurethane gastrostomy tube has been very durable; none has required replacement because of deterioration.