Catheter tips

Catheter tip should not be extended into the right atrium ° Maximum rate is 40 mEq/h... 

Impingement of the catheter tip on visceral organs Instillation pain... 

Central PN refers to the administration of PN via a large central vein, and the catheter tip must be positioned in the vena cava. Central PN allows the infusion of a highly concentrated, hypertonic nutrient admixture. The typical osmolarity of a central PN admixture is about 1500 to 2000 mOsm/L. Central veins have much higher blood flow, and the PN admixture is diluted rapidly on infusion, so phlebitis is usually not a concern. Patients who require PN administration for longer periods of time (greater than 7 days) should receive central PN. One limitation of central PN is the need for placement of a central venous catheter and an x-ray to confirm placement of the catheter tip. Central venous catheter placement may be associated with complications, including pneumothorax, arterial injury, air embolus, venous thrombosis, infection, chylothorax, and brachial plexus injury.1,20... 

Despite the limitations of the animal model, this preclinical experience has translated well into clinical trials. However, it is very important to note that the clinical safety profile of transendocardial delivery so far has entailed precise preinjection measurements of needle extension with the injection catheter tip deflected (to 90 degrees) and not deflected, arbitrary insistence on a maximal needle-to-wall ratio of 0.6, and a conscious decision not to inject stem cells into cardiac walls that are less than 8 mm thick or into the true apical segment. 

Hywel Davies reported of temporarily treatment of aortic regurgitation with a parachute valve mounted onto a catheter tip in 1965 (34). Twenty-seven years later Andersen and his colleagues described the first experience with a bioprosthetic valve attached to a wire-based stent and mounted on a balloon valvuloplasty catheter (35). In 2002, Alain Cribier performed the first transcatheter valve implantation in an elderly patient with inoperable aortic stenosis using a prototype of a stent-mounted, pericardial, tricuspid aortic valve (36). 

Bergveld, P., Bedside clinical chemistry from catheter tip sensor chips towards micro total analysis systems. Biomed. Microdevices 2000, 2(3), 185-195. 

In a typical design the transducer head, illustrated in Fig. 6.36(b), comprises an array of 64 PZT bars (approximate dimensions 500x30x70 /mi) arranged around the catheter tip. 

To form the array a 70 /un thick poled sheet (5x0.6 mm) of PZT is bonded between two metallized polymer sheets. The PZT is sliced into the 64 elements by diamond-cutting, the cut just penetrating the bottom polymer layer so allowing the whole to be wrapped around the catheter tip. The outer polymer film, about 20 /nn thick, serves as a 2/4 acoustic matching layers and also carries the thin copper tracks to electrically address each element. 

TIA, stroke or death as a result of dislodgement of atheromatous plaque by the catheter tip dissection of the arterial wall thrombus formation on the catheter tip air embolism... 

The 1980s saw the development of a competing technology, that of electrosurgical or radio frequency (rf) catheters that destroy tissue by heating them to temperatures above about 42 °C. These rf catheters are simpler and easy to control. However, they are limited to the amount of tissue they can destroy at one location because the temperature difference between the 42 °C destruction temperature and the catheter tip is limited by the 100 °C boiling point of the water in the tissue. The rf catheters have become quite widely accepted by the medical community at this time. The later development of cryogenic catheters has hindered their use in place of the rf catheters... 

Figure Ic. With catheter in place balloon is inflated to block blood flow and catheter tip freezes damaged tissue.

Figure 3. Cutaway schematic of catheter tip and ice ball showing two different temperature profiles and the location destroyed tissue. With the steeper gradient less healthy tissue is destroyed with temperamres below -20 C.

Typical operating conditions were 140 K with about 3 W of additional heat added to the cold end. A few experiments were performed with the cold end inserted into a room temperature gelatin to simulate biological heat loads. Catheter tip temperatures of 160 to 175 K were achieved and ice balls with diameters of about 26 mm and a mass of 11 g were created. 

The authors speculated that the catheter tip had spontaneously migrated because the ulcer on the left shoulder had eroded deeply to form a venocutaneous fistula with the left cephaUc vein. Continuous leakage of parenteral nutrition fluid through the fistula was soaked up by the gauze pads used to cover the ulcer, preventing early recognition of the problem. 

A major complication of intravenous infusion is thrombophlebitis, which is a principle limitation of peripheral parenteral nutrition. Its precise pathogenesis is unclear, but venospasm has been proposed as the most likely cause. However, in a study with ultrasound techniques to monitor vein caliber, there was no evidence to support this hypothesis, although thrombophlebitis was observed (10). The author suggested that the initiating event may be venous endothelial trauma, caused by the venepuncture itself, abrasion at the catheter tip, or the delivery of the feeding solution. 

Horner s syndrome (miosis, ptosis, anhidrosis, and vasodilatation, with increased temperature of the affected side) can result from epidural anesthesia. A report of Horner s syndrome due to a thoracic epidural catheter has highlighted the fact that small doses of local anesthetic can block the sympathetic fibers to the face, particularly when the catheter tip is close to T2 (142). The same symptoms have been reported after obstetric epidural anesthesia (143). 

An 84-year-old man with diabetic nephropathy and end-stage renal disease began continuous ambulatory peritoneal dialysis and over the next year had four episodes of exit-site infection and peritonitis and used mupirocin ointment. The exit-site catheter became dilated and during an episode of infection for which he used mupirocin on 6 successive days, a longitudinal rupture developed in the peritoneal catheter, which was removed. The peritoneal liquid contained Escherichia coli and Proteus mirabilis and the catheter tip contained E. coli and Enterobacter cloacae. He was treated with ciprofloxacin, without complications, and after 1 month a new peritoneal catheter was inserted. 

Thrombosis of the vascular access is a major problem in chronic HD. Although thrombosis occurs in grafts, and to a lesser extent Hs-tulas, thrombosis associated with catheters is the most problematic and will be the focus of discussion here. Early dysfunction (less than 5 days after placement) of an HD catheter is usually associated with an intracatheter or catheter-tip thrombosis, or a malpositioned catheter. Thrombi that occur after approximately 1 week can be outside the catheter (extrinsic) or within the catheter (intrinsic). Intrinsic throm-... 

Mechanical, medical, and infectious problems complicate peritoneal dialysis therapy. Mechanical comphcations include kinking of the catheter and inflow and outflow obstruction excessive catheter motion at the exit site, leading to induration and possible infection and aggravation of tissues pain from impingement of the catheter tip on the viscera or inflow pain resulting from a jet effect of too rapid dialysate inflow. 

Complications from IP therapy may be related to catheter fnnc-tion, infection, or bowel problems. Mechanical obstrnction to flnid inflow has been reported in approximately 5% of patients. Most commonly, this results from fibrin sheath formation around the catheter tip. In some cases, peritoneal adhesions obstruct fluid entry into the abdominal cavity, causing uneven distribution of the chemotherapentic agent. Infections complications, such as superficial cellulitis around the catheter entry site, deep tissue infections, and peritonitis, are the most prevalent IP-related comphcations and are reported in approximately 10% of patients. Bowel-related comphcations (approximately 3% incidence) inclnde obstruction. Ecus, and perforation. IP administration may also resnlt in a false CA-125 elevation. ... 

---