Pinch-off syndrome: a complication of implantable subclavian venous access devices

Implantable central venous access devices placed via the subclavian vein may become obstructed by thrombosis, impingement against a vein wall, or compression between the clavicle and first rib. The latter has been termed pinch-off syndrome (POS). Eleven patients with POS were studied, including one whose catheter had fractured and one whose catheter had fragmented. They were compared with 22 matched control patients and 100 consecutive routine clinic patients. Each catheter was graded: 0 = normal, 1 = abrupt change in course with no luminal narrowing, 2 = luminal narrowing, and 3 = complete catheter fracture. POS was present in most (eight of 11) cases within 3 weeks after placement. A grade 1 catheter was common (33%) among control subjects, but grades 2 and 3 were uncommon (1%). Catheter fracture or fragmentation was seen in two of five cases with long-term (greater than 3 weeks) pinching (grade 2 catheter). The following conclusions were reached: Grade 2 represents significant catheter compression and the potential for serious complications. Grade 1 is of uncertain clinical significance, due to its high prevalence in control subjects.

Perioperative antibiotic prophylaxis in the gastric bypass patient: Do we achieve therapeutic levels?

BACKGROUND

Perioperative surgical antibiotic prophylaxis requires that therapeutically effective drug concentrations be present in the tissues.

METHODS

Patients undergoing Roux-en-Y gastric bypass for morbid obesity were given 2 g cefazolin preoperatively, followed by a second dose at 3 hours. Thirty-eight patients were each assigned to 1 of 3 body mass index (BMI) groups: (A) BMI=40-49 (N = 17); (B) BMI=50-59 (N=11); (C) BMI > or= 60 (N=10). Multiple timed serum (baseline; incision, 15, 30, 60 minutes; prior to second prophylactic dose; and closure) and tissue (skin, subcutaneous fat, and omentum) specimens were collected and cefazolin concentration analyzed by microbiological assay.

RESULTS

No significant difference was observed in intraoperative fluid replacement or blood loss among BMI groups. Serum antimicrobial concentrations exceeded resistance breakpoint (32 microg/mL) in 73%, 68%, and 52% of BMI groups A, B, and C, respectively. No significant difference in cefazolin concentration was observed in mean incisional skin and closure tissue specimens in groups A, B, and C. A significant decrease in cefazolin concentration was noted in closure adipose (p=.04), initial (p=.03) and closure omentum (p=.05) tissues in groups B and C compared with A. Over 90% of serum samples exhibited therapeutic concentrations covering 53.8% of gram-positive and 78.6% of gram-negative surgical pathogens. However, therapeutic tissue levels were achieved in only 48.1%, 28.6%, and 10.2% of groups A, B, and C, respectively.

CONCLUSIONS

Pharmacokinetic analysis suggests that present dosing strategies may fail to provide adequate perioperative prophylaxis in gastric bypass patients.

Anemia after bariatric surgery: more than just iron deficiency

Bariatric surgery for morbid obesity is rapidly gaining popularity. Restrictive and/or malabsorptive surgical interventions result in dramatic weight loss with significantly decreased obesity-related morbidity and mortality. Anemia, which may affect as many as two-thirds of these patients, is of concern and generally thought to be caused by iron deficiency. Although iron deficiency in this population may be frequent given pouch hypoacidity, defunctionalized small bowel, and red meat intolerance, it may not account for all anemias seen. First, there is increasing evidence that obesity creates a state of chronic inflammation. Both iron deficiency anemia and anemia of chronic inflammation present with low serum iron levels. Most studies reporting anemia after bariatric surgery lack serum ferritin determinations so that the relative contribution of inflammation to anemia cannot be assessed. Second, a significant number of anemias after bariatric surgery remain unexplained and may be attributable to less frequently seen micronutrient deficiencies such as copper, fatsoluble vitamins A and E, or an imbalance in zinc intake. Third, although deficiencies of folate and vitamin B(12) are infrequent, study observation periods may be too short to detect anemia attributable to vitamin B(12) deficiency because vitamin B(12) storage depletion takes many years. This review is intended to increase awareness of the mechanisms of anemia above and beyond iron deficiency in the bariatric patient and provide healthcare providers with tools for a more thoughtful approach to anemia in this patient population.

Pinch-off syndrome: a rare etiology for central venous catheter occlusion

BACKGROUND

Catheter pinch-off syndrome is a rare and often misdiagnosed complication of tunneled Silastic central venous catheters. Pinch-off syndrome occurs when the catheter is compressed between the first rib and the clavicle, causing an intermittent mechanical occlusion for both infusion and withdrawal. We report its incidence in a large series of catheter insertions and describe the clinical presentation, radiographic findings, and recommended treatment.

METHODS

A total of 1457 tunneled Silastic central venous catheters that were inserted using the percutaneous subclavian approach were prospectively studied. Indications for catheter placement included bone marrow transplant, continuous or intermittent chemotherapy, long-term antibiotics, and parenteral nutrition. Catheters were evaluated for clinical presentation of an occlusion relieved by postural changes and radiographic findings of luminal narrowing.

RESULTS

Pinch-off syndrome was identified in 16 (1.1%) catheters. Radiographic findings were present in all catheters; clinical findings were present in 15 catheters. Clinical symptoms presented within a median of 2 days after placement (range, 0 to 167 days). Partial or complete catheter transection, a serious sequela of catheter pinch-off syndrome, occurred in 19% of the identified catheters.

CONCLUSIONS

(1) Catheter pinch-off syndrome presents clinically as a catheter occlusion related to postural changes; (2) clinical symptomatology should be confirmed radiographically; and (3) catheter removal with a more lateral replacement in the subclavian vein or in the internal jugular vein will avoid a recurrent complication.

Maladaptive eating patterns after weight-loss surgery

Weight-loss surgery has been shown to contribute to the improved health and well-being of the clinically severe obese, and for many has been seen as their "last resort." Although the majority of patients who choose this option as a means to achieve a healthier weight are successful, for some patients it is not beneficial. Bariatric surgery is not a panacea, and its immediate and long-term success depends on the patient's ability to incorporate lifestyle and behavioral changes. Patients who are not successful in achieving and maintaining their anticipated weight loss struggle to comply with diet, exercise, and vitamin regimens. Not only do these patients exhibit diminished weight loss, they have put themselves at risk for vitamin and mineral deficiencies and protein malnutrition. Their problematic response to weight-loss surgery may or may not be due to a worsening of presurgical depression, binge eating, emotion-triggered eating, body image, or eating behaviors associated with specific situations such as social events. This paper describes clinical responses we have observed in our bariatric practice. Several case studies are presented to highlight problems we have encountered when following bariatric surgery patients in the early postoperative period, as well as in a long-term setting. Recommendations are made for screening and follow-up of at-risk patients.

Elimination of intraluminal colonization by antibiotic lock in silicone vascular catheters

An in vitro model was designed to evaluate the efficacy of instilled antimicrobials to reduce or eliminate intraluminal microbial colonization. Minimal inhibitory concentration and minimal bactericidal concentration activity of appropriate test anti-infectives were determined using standard methodology against clinically derived and reference test strains commonly associated with catheter-related infection. Drug activity was validated by bioassay for the test anti-infectives. Reference and clinical test strains were inoculated to the intraluminal surface of silicone catheter segments and incubated for 30 min, after which the inoculum was replaced with total parenteral nutrition (TPN) solution and reincubated for 12 h. For 7 d, instillation of antibiotic and TPN solution was alternated every 12 h to simulate clinical conditions. On days 1, 4, and 7, catheter segments were rinsed, bisected, and sonicated for quantitative plate count to determine mean microbial counts per centimeter of catheter surface. Catheter segments were also prepared for scanning electron microscopy. A significant decrease in staphylococcal intraluminal colonization after instillation of nafcillin, ceftriaxone, gentamicin, and vancomycin was demonstrated (P < 0.001). Aztreonam, ceftriaxone, and gentamicin completely eliminated gram-negative catheter colonization (P < 0.001). Yeast was eradicated from the internal catheter surface after treatment with amphoteracin B, and fluconazole significantly decreased intraluminal colonization (P < 0.001). Results show a significant decrease in staphylococcal, gram-negative, and fungal intraluminal colonization after instillation of appropriate antimicrobial. In vitro results support early clinical success using this technique. Future studies are warranted to identify optimal drug concentrations and dosing intervals.

In vitro and in vivo evaluation of a somatostatin analogue released from PLGA microspheres

The purpose of this study was to design poly(lactide-co-glycolide) (PLGA) microspheres for the continuous delivery of the somatostatin analogue, vapreotide, over 2-4 weeks. The microspheres were produced by spray-drying and the desired characteristics, i.e. high encapsulation efficiency and controlled release over 2-4 weeks, achieved through optimizing the type of polymer, processing solvent, and co-encapsulated additive. The in vitro release was tested in fetal bovine serum preserved with 0.02% of thiomersal. Furthermore, formulations were injected intramuscularly into rats to obtain pharmacokinetic profiles. Encapsulation efficiency was between 34 and 91%, depending on the particular formulation. The initial peptide release (within 6 h) was lowest, i.e. <20%, when acetic acid was used as processing solvent and highest, i.e. 57%, with dichloromethane. The various co-encapsulated additives generally lowered the encapsulation efficiency by 15-30%. The best formulation in terms of low burst and effective drug serum levels (>1 ng/ml) over 21-28 days in rats was the one made with end-group uncapped PLGA 50:50, the solvent acetic acid and the additive polyethyleneglycol. In conclusion, the optimization of formulation parameters allowed us to produce vapreotide-loaded PLGA microspheres of suitable characteristics for therapeutic use.

Treatment of Hickman catheter sepsis using antibiotic lock technique

Antibiotic lock therapy, an alternative treatment for Hickman catheter sepsis, was evaluated in six recipients of prolonged outpatient intravenous therapy. Twenty-two episodes of catheter sepsis were identified, involving coagulase-negative staphylococci (11), gram-negative bacilli (3), gram-positive bacilli (1), yeast (4), and mixed bacteria or fungi (3). In a select group of patients, treatment was successful 92% of the time.

Glucose response to abrupt initiation and discontinuation of total parenteral nutrition

Plasma glucose was studied during the initiation of total parenteral nutrition (TPN) and the discontinuation of TPN without a tapering schedule. Blood was sampled every 5 minutes for 2 hours after the start of TPN and 1 week later as TPN was discontinued. A total of 14 initiations and 14 discontinuations were studied in 18 patients. Severity of illness in patients ranged from stable condition postoperatively to multiple-system failure; six patients had diabetes mellitus. The TPN solution was a 3:1 admixture that provided a caloric intake equal to 1.2 times the resting energy expenditure, with 40% fat and 60% carbohydrate calories. An average of 1963 kcal was provided per day (340 g of glucose, 79 g of fat). During the initiation phase, the mean increase in plasma glucose was 60 mg/dL. The increase for diabetic patients was 79 +/- 14 mg/dL compared with 52 +/- 23 mg/dL for the nondiabetics. During the discontinuation phase, the mean plasma glucose decreased 40 +/- 20 mg/dL; two patients with high concentrations of regular insulin (50 and 100 units) showed an increase in plasma glucose when the TPN was stopped. Plasma glucose returned to the preinfusion baseline after discontinuation. During both initiation and discontinuation, plasma glucose showed little change after the first 60 minutes. No clinical symptoms of hypoglycemia were observed. In conclusion, TPN as a 3:1 admixture can be safely started as full nutrition support and stopped abruptly without a tapering schedule. Plasma glucose response is rapid, predictable, and mostly complete within 60 minutes.

The malfunctioning silastic catheter--radiologic assessment and treatment

Occlusion of silastic catheters is attributed to several documented causes. One factor not yet adequately documented is fibrin sleeve formation. In this instance, the catheter functions for infusion purposes, but blood withdrawal is no longer feasible. This is a troublesome occurrence when encountered in the clinical setting. This report reviews the assessment of fibrin sleeve formation, the use of catheter phlebography and treatment with low-dose streptokinase. Seventeen instances of the inability to aspirate blood from silastic catheters are evaluated with restoration of full catheter function in all cases after streptokinase administration.

Hepatic gene networks in morbidly obese patients with nonalcoholic fatty liver disease

BACKGROUND

Genetic factors alter the risk for nonalcoholic fatty liver disease (NAFLD). We sought to identify NAFLD-associated genes and elucidate gene networks and pathways involved in the pathogenesis of NAFLD.

METHODS

Quantitative global hepatic gene expression analysis was performed on 53 morbidly obese Caucasian subjects undergoing bariatric surgery (27 with NAFLD and 26 controls). After standardization of data, gene expression profiles were compared between patients with NAFLD and controls. The set of genes that significantly correlated with NAFLD was further analyzed by hierarchical clustering and ingenuity pathways analyses.

RESULTS

There were 25,643 quantitative transcripts, of which 108 were significantly associated with NAFLD (p < 0.001). Canonical pathway analysis in the NAFLD-associated gene clusters showed that the hepatic fibrosis signaling was the most significant pathway in the up-regulated NAFLD gene cluster containing three (COL1A1, IL10, IGFBP3) significantly altered genes, whereas the endoplasmic reticulum stress and protein ubiquitination pathways were the most significant pathways in the down-regulated NAFLD gene cluster, with the first pathway containing one (HSPA5) and the second containing two (HSPA5, USP25) significantly altered genes. The four primary gene networks associated with NAFLD were involved in cell death, immunological disease, cellular movement, and lipid metabolism with several significantly altered "hub" genes in these networks.

CONCLUSIONS

This study reveals the canonical pathways and gene networks associated with NAFLD in morbidly obese Caucasians. The application of gene network analysis highlights the transcriptional relationships among NAFLD-associated genes and allows identification of hub genes that may represent high-priority candidates for NAFLD.

Surgical treatment for obesity: ensuring success

In the United States, obesity has reached epidemic proportions. Serious medical complications, impaired quality of life, and premature mortality are all associated with obesity. Medical conditions such as type 2 diabetes mellitus, hypertension, hyperlipidemia, or sleep apnea can improve or be cured with weight loss. Medical treatment programs focused on diet, behavior modification, and/or pharmacologic intervention have met with limited long-term success. Although surgical treatments for obesity have become popular in recent years, they should only be used as a last resort for weight loss. Not all patients can be considered appropriate candidates for surgery; therefore, guidelines based on criteria from the National Institutes of Health should be used preoperatively to help identify suitable persons. Most individuals who opt for weight-loss surgery have usually struggled for many years with losing weight and keeping it off, but surgery alone will not ensure successful weight loss. Patient education is imperative for long-term success. Moreover, any such educational regimen should include information on diet, vitamin and mineral supplementation, and lifestyle changes, as well as expected weight-loss results and improvements in comorbid conditions. Patients must be willing to commit to a long-term follow-up program intended to promote successful weight loss and weight maintenance and to prevent metabolic and nutritional complications.

Twenty-five Years of Advances in Vascular Access: Bridging Research to Clinical Practice

Vascular access has become a key component for a multitude of IV therapies, including parenteral nutrition. Access of the central venous system has been long recognized for its associated complications of infection, thrombosis, and occlusion. Over the past 25 years, clinical practice based on research and innovation has attempted to decrease complication rates and therefore improve the safety of vascular access. This article highlights the research and its influence on catheter care procedures, technology, and education that has led to advances in vascular access. An improved understanding of the pathophysiology associated with catheter-related complications and an ongoing evaluation of new treatment modalities has provided clinicians today with new options for improved patient care and the ability to preserve vascular access options for patients.

Nutrition support in specific diseases: back to basics

The nutrition care of a patient is complicated by the recent proliferation of commercially available specialty products. Rational and objective guidelines are necessary to direct formula selection for use in specific diseases. Consideration of the patient's nutritional status, functioning of major organ systems, and alterations in nutrient metabolism are essential. The diagnosis of a specific disease does not necessitate the use of a specialty product in all instances. Many times modification of a standard formula can result in safe and effective nutrition. Basic nutrition principles should continue to guide the clinician as the definitive answers to the issues surrounding metabolic support in patients with specific disease states become available.

The substance abuser and home intravenous therapy: above all else, do no harm

Home care therapy is being challenged by changes in patient populations and technologic advances. The selection of appropriate candidates for home intravenous therapy is a critical issue faced by health care professionals. This process is more complex when the patient has a history of intravenous drug abuse. The issues concern patient compliance, safety, ethics, and legal responsibilities. Safe care depends on the ability of the patient to demonstrate a predetermined level of competence with catheter use. The potential use of illicit drugs may influence the ability of the patient to be compliant. Ethical principles of the patient's autonomy and free choice are weighed against the health professional's sense of beneficence. Legal guidelines stress informed consent, standards of care, and adequate documentation. An exploration of each of these factors outlines the potential risks and benefits and provides a basis for making clinical judgments.

Central venous access. Clinical practice issues

Central venous catheterization has facilitated the delivery of parenteral nutrition for over 20 years. Current practice in the care of central venous catheters and management of associated complications reflects past clinical experience and innovative research study. The article highlights key issues associated with central venous access from a clinical perspective.

Central venous catheter occlusion: successful management strategies

Catheter occlusion is the most common noninfectious complication seen with longterm central venous access devices. Medical-surgical nurses frequently encounter these devices both in the hospital and home and are in a key position to recognize catheter occlusions and institute appropriate treatments. The etiology of catheter occlusion, its clinical evaluation, prevention, and treatment strategies will be reviewed.

Catheter pinch-off syndrome: recognition and management

Catheter pinch-off syndrome is an uncommon and often unrecognized complication of central venous catheters. The cause, clinical diagnosis, and management of this unique catheter occlusion are reviewed. Nurses can play a key role in the early detection of catheter pinch-off syndrome as well as the prevention of subsequent catheter fracture and embolization.