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At least 127 records · Page 7Linked to original sources
PubMed1990

In-vitro evaluation of neonatal ECMO cannulae with regard to flow characteristics.

One of the crucial points in a neonatal ECMO circuit is to obtain adequate venous drainage from the cannula in the right jugular vein, as the vessel diameter limits the size of cannula that can be used. For this reason the design of the cannula is of utmost importance. The aim of this paper was to compare different commercially available ECMO cannulae, and to try to find the cannula which had the best flow characteristics. Venous cannulae were evaluated with regard to maximum drainage capacity at different hydrostatic levels. For arterial use, pressure drop over the cannulae at different flow rates was measured. Of the cannulae studied, those from Biomedicus and Elecath had the best flow characteristics for both venous and arterial use.

Catheters, Indwelling↗
PubMed1999

Laboratory testing of femoral venous cannulae: effect of size, position and negative pressure on flow.

Femoral venous cannulae (17-28 French) were tested to compare flows obtained by their placement in a simulated inferior vena cava (IVC) or right atrium (RA) and by varying drainage pressures using gravity siphon drainage or a centrifugal pump in the venous line. The circuit consisted of conventional tubing and equipment including a segment of thin-walled latex tubing to simulate the IVC connected to a flexible reservoir to simulate the RA. The test fluid was a 40% glycerin solution. Flow was measured at height differentials of 30-60 cm (cannula-to-inlet of hard-shell venous reservoir) and with a -10 to -80 mmHg negative pressure created by the centrifugal pump. A roller pump returned the test fluid to a flexible bag to maintain a filling pressure of 0-1 mmHg. Flow increased modestly with an increasing height differential. When negative pressure was applied with the centrifugal pump, flow increased 10% and 18% (IVC and RA positions, respectively) compared to gravity siphon drainage conditions. There also was a tendency for flow to plateau or cease when the centrifugal pump was used at higher levels of negative pressure or when larger cannulae were used. We conclude: (1) position of smaller cannulae in the RA yield better flows than when the cannulae are larger and placed in the IVC; (2) smaller-sized cannulae are capable of achieving higher flows when the centrifugal pump is used; (3) cannulae must be properly positioned to achieve maximum flow; (4) the centrifugal pump will augment flow, but should be regulated to avoid extreme negative pressures; and (5) cannula design has no demonstrable effect on flow.

Catheterization↗
PubMed2002

Hydrodynamics of the new Medos aortic cannula.

BACKGROUND: Postoperative neurologic complications in cardiac surgery patients are considered to be associated with the design of an aortic cannula and its hydrodynamic profile. To gain knowledge about the hydrodynamics of a new cannula type, based on the integration of a helical stator in its tip, was the aim of the present study. METHODS: Pressure gradients and back pressures of the new Medos aortic cannula were measured and compared with a commonly used single-stream cannula at varying flow rates in a mock circulation. Additionally, flow visualization was performed by ink injection. RESULTS: Pressure gradients across the Medos cannula were 25.5-31.8% lower at all flow rates measured when compared to the reference cannula. Back pressures of the Medos cannula were 64.1-67.9% lower than reference back pressures. CONCLUSIONS: The Medos cannula provides improved hydrodynamic characteristics, probably reducing the risk of atherosclerotic embolism and cerebral malperfusion by avoidance of high back pressures and sandblasting effect.

Aorta↗
PubMed2004

Improved hydrodynamics of a new aortic cannula with a novel tip design.

BACKGROUND: Reduction of atheroembolic complications during cardiopulmonary bypass remains a major challenge in cardiac surgery. New cannula tip designs may help to attenuate this problem by improved hydrodynamics. METHODS: Pressure gradients and back pressures of a new aortic cannula tip design were measured and compared with the Medos X-Flow, Sarns Soft-Flow and Argyle THI cannulae at various flow rates in a mock circulation followed by flow visualization. RESULTS: Pressure gradients were the lowest for the new cannula. Back pressures of the new cannula were up to 84% lower than for the Argyle cannula. The back pressure profile and flow visualization of the new cannula showed broad centric flow dispersion with a transcannula increase of flow area from 38 mm2 to 139 mm2. CONCLUSIONS: The new design of an aortic cannula tip provides improved hydrodynamics, with low pressure gradients, low back pressures and a uniform central dispersion of flow, reducing the sandblasting effect.

Aorta↗
PubMed1990

Use of a chronic ureter cannula in the pig for the determination of renal clearance.

The surgical implantation of chronic ureter cannula to determine the renal clearance was evaluated using 24 pigs. The silicon tubing was surgically implanted into both ureters of each pigs. Two types of thick tubing (the inside diameter 1.0 or 2.5 mm and the outside diameter 4.0 mm) were used for these cannulas. The tubing was exposed out of the pig's body on the flank, on the hypogastric zone near the umbilicus, or near the groin. The following steps were effective to minimize the opportunity of a bacterial infection in the kidney and to maintain the functional integrity of the chronic ureter cannula for as longer period as possible: 1) to use the tubing of larger opening as the ureter cannula, 2) to expose the tubing from the hypogastric zone near the groin, and 3) to apply the disinfectant frequently to the incision sites, cannula outlets and pig's metabolic cage. The oral ingestion of the GGES solution increased the urinary volume, which might in turn have resulted in the effective rinsing of the kidney and the chronic ureter cannula. The cannula served satisfactorily for more than 3 weeks in 13 of the pigs, up to a maximum of 7 weeks. The PSP clearances values were low during the first week of the postoperative period, which may be attributed to surgical stress. The chronic ureter cannula, associated with the postoperative period of more than 1 week, can be recommended for the evaluation of the renal clearance of drugs in the pig.

Animals↗
PubMed2005

Reflux-free cannula for convection-enhanced high-speed delivery of therapeutic agents.

OBJECT: Clinical application of the convection-enhanced delivery (CED) technique is currently limited by low infusion speed and reflux of the delivered agent. The authors developed and evaluated a new step-design cannula to overcome present limitations and to introduce a rapid, reflux-free CED method for future clinical trials. METHODS: The CED of 0.4% trypan blue dye was performed in agarose gel to test cannula needles for distribution and reflux. Infusion rates ranging from 0.5 to 50 microl/minute were used. Agarose gel findings were translated into a study in rats and then in cynomolgus monkeys (Macacafascicularis) by using trypan blue and liposomes to confirm the efficacy of the reflux-free step-design cannula in vivo. Results of agarose gel studies showed reflux-free infusion with high flow rates using the step-design cannula. Data from the study in rats confirmed the agarose gel findings and also revealed increasing tissue damage at a flow rate above 5-microl/minute. Robust reflux-free delivery and distribution of liposomes was achieved using the step-design cannula in brains in both rats and nonhuman primates. CONCLUSIONS: The authors developed a new step-design cannula for CED that effectively prevents reflux in vivo and maximizes the distribution of agents delivered in the brain. Data in the present study show reflux-free infusion with a constant volume of distribution in the rat brain over a broad range of flow rates. Reflux-free delivery of liposomes into nonhuman primate brain was also established using the cannula. This step-design cannula may allow reflux-free distribution and shorten the duration of infusion in future clinical applications of CED in humans.

Animals↗
PubMed2000

[A new cardiovascular surgical instrument: cannula stabilizer].

A new instrument has been developed to safely keep the venous cannula out of the operative field during open heart surgery. This instrument is designed for holding the venous cannula in a curved state at a desired angle. It consists of four semicircular claws mounted on a bar. The size of the claws is tailored so that they comfortably accommodate the standard-size two-stage venous cannula. The bar is flexible enough to be bent manually to form the required curvature, and at the same time it is strong enough to resist the self-uncoiling force of the cannula. When in use, the bar is bent to form the desired curvature and then it is placed on the required portion of the venous cannula. The angle of its curvature and its location on the cannula can be adjusted easily as required during the course of the operative procedure. With this instrument the venous cannula can be easily held in a curved state without disturbing venous return so that the cannula does not come into the way of the surgeon's hands.

Cardiovascular Surgical Procedures↗
PubMed1990

Single-cannula venovenous bypass for respiratory membrane lung support.

Clinical use of a single cannula would make extracorporeal membrane oxygenation simpler and less aggressive. It would probably limit the occurrence of the complications of currently used techniques (double-cannula, venoarterial, or venovenous bypass). In this experimental study an original system is described that is composed of a single cannula, an alternating clamp, and a nonocclusive roller pump, the characteristics of which permit its use as a venous reservoir. To overcome the limitations of the oxygenation in any venovenous bypass, we used the method of "apneic oxygenation" through the natural lungs, which we previously proved efficient in infants and children. The optimal setting of the alternative clamp was first tested in vitro to obtain the maximal flow in the circuit and the minimal amount of recirculation. The single-cannula bypass then was compared with a two-cannula circuit regarding the efficiency of carbon dioxide removal and the hemodynamic consequences. At less than 50% of the maximal speed of the pump, flows were equivalent in both types of circuits. The efficiency of carbon dioxide removal was only slightly decreased by the use of a single cannula (30 +/- 2 ml/min versus 36 +/- 2 ml/min with two cannulas). This could easily be offset by increasing the gas flow/blood flow ratio in the oxygenator. Arterial carbon dioxide tension was maintained at normal levels in both types of circuits. Hemodynamic condition was only slightly affected by the alternative flow of the bypass. This system of single-cannula membrane lung support thus seems to be adequate for clinical use.

Animals↗
PubMed1990

[The attaching of bypass cannulas to the duodenum of dairy cows].

Described in this paper is a bypass cannula for the small intestine (duodenum, ileum) of dairy cows, with reference being also made to the surgical method used on the duodenum. The bypass cannula is made up to flexible, curved single cannulas, 25 mm in diameter, which by a new design are safely connected to each other in a jointless, non-angular manner. The cannulas are manufactured of Type B 400/40 K PVC paste by means of a casting technique. The connecting link consists of a PVC or piacryl tube, about 45 mm in length, which is pressed by means of sleeve nuts against the collars of the two cannula openings. The bypass cannula weights 160 g and is tightly attached to the body of the animal, so that neither grazing nor calving are obstructed. Bypass problems of the past (leakage from proximal cannula, clogging, accidental opening of cannula connection) have not even occurred to high-performance cows with feed uptake rates between 3.0 and 3.5 kg of dry matter to 100 kg of live weight and corresponding digestion passages up to 400 l daily.

Animals↗
PubMed1967

Three years' experience with bypass cannulae for chronic hemodialysis.

In 14 patients over the past three years, "bypass" cannulae have been inserted to relieve obstruction in cannulae used for chronic hemodialyses. Experience with these patients has prompted changes resulting in improved technique.Clotting was the major cause of cannulae failure and infection was the second most important cause. Other causes of failure included: venous atheroma, cannulae extrusion, aneurysms of the vessel at the cannulae tips, obstructive vegetation on the vessel wall, calcium deposits on the vessel wall, and thrombi on the vein walls.The mean survival time was improved from 1.9 months in 1963-1964 to over 9.0 months in 1965-1966. The longest surviving cannula set was two years and the shortest one week.It is considered that the most important factors contributing to increased cannula survival are improved cannula care by patients and staff, the use of angiography for accurate diagnosis, and prompt anticoagulation if atheromatous stenosis of the venous component is encountered.

Adult↗
PubMedDate not supplied

Use of two-dimensional and contrast echocardiography for venous cannula placement in venovenous extracorporeal life support.

The objective of this study was to determine the efficacy of two-dimensional and contrast echocardiograms to identify venous cannula position. Sequential sampling of 20 infants was evaluated by contrast echocardiography after meeting institutional criteria for extracorporeal life support. Each infant was placed on venovenous extracorporeal life support using a double-lumen cannula. After surgical placement was thought to be satisfactory, optimal two-dimensional images of the cannula were obtained via a subxiphoid or apical view and 2 ml agitated normal saline were injected rapidly into the nearest infusion port. Patient demographics and mixed venous saturations were noted. Distance of the venovenous cannula to tricuspid valve and distance of the venovenous cannula from the intra-atrial septum was recorded. Echocardiograms were available for review on 18 of the 20 patients. Position of the venovenous cannula in relationship to the tricuspid valve was as follows: < 5 mm (8); 5-10 mm (5); > 10 mm (5). Mixed venous saturations decreased, which indicated less recirculation when the orientation of the tip of the cannula was toward the lateral wall in those who required repositioning. The authors conclude that two-dimensional and contrast echocardiography aid in the positioning of the venovenous cannula. Satisfactory position is approximately 5 mm from the tricuspid valve, with orientation toward the lateral wall of the right atrium.

Catheterization, Central Venous↗
PubMed1997

Blood trauma in plastic haemodialysis cannulae.

To investigate the haemolysis in haemodialysis cannulae, an in-vitro set up is built, using a unipuncture dialysis system. This system is connected to a bag with fresh calf's blood, by the cannula under test, mounted in a large bloodline (5 mm diameter). The blood characteristics are kept constant by means of a bicarbonate dialysate in the dialyser. During a 6 h period, haematological parameters are regularly samples. Flow through the cannulae is recorded, which is about 500 mL/min. Four different cannulae are tested and compared to the results obtained without any cannula in the circuit. In all cases a linear increase in plasma free haemoglobin levels is found after 6 h. The cannulae can be ranked from 8F catheter over 13G, 14G to 16G cannula, the latter producing the highest degree of haemolysis. When using plastic cannulae at high blood flows, their haemolytic effect may not be neglected.

Animals↗
PubMed1985

Intraocular cannula for continuous, chronic drug delivery. Histopathologic observations and function.

An indwelling cannula for drug delivery was implanted in rabbit eyes. Rabbits were followed up for as long as 1 1/2 years after surgery. They showed almost no adverse effects as a result of the implantation, and cannula patency was demonstrated by the injection of fluorescein sodium through the cannula at various times following surgery. Histopathologic studies using light and electron microscopy were performed at various times to determine the effect of cannula implantation on the eye. Cellular proliferation along the cannula after 1 1/2 years was limited to the region immediately adjacent to the wound and rarely extended to the surrounding retina or ciliary body. The proliferative tissue at the wound site originated mainly from the episclera; the retina and the choroid at the posterior fundus remained intact. Photoreceptor cell metabolism was studied by light microscopic autoradiography following intraocular injection of tritiated leucine to assess photoreceptor outer-segment renewal. Autoradiography showed normal receptor uptake of leucine. A broad band of radioactive labeling of the outer segments resulted from continuous, chronic drug delivery, while a narrow band of labeling resulted from a single intravitreous injection. These data indicate that the cannula system continuously delivered tritiated leucine into the vitreous cavity. We believe that the implanted intraocular cannula, which allows continuous drug delivery on a relatively long-term basis, will be a valuable technique for research and possibly clinical studies.

Animals↗
PubMed1995

Bypass cannulas utilized in extracorporeal membrane oxygenation in neonates: radiographic findings.

ECMO, as applied to neonates with severe respiratory failure, involves either a single or dual cannula system for removal of desaturated blood from and return of oxygenated blood to the patient. ECMO cannulas have undergone considerable change and improvement since the early 1980s, and a variety of cannulas are now available commercially for neonatal ECMO. All ECMO cannulas have a characteristic appearance on the chest radiograph, which is important in the assessment of cannula position and some cannula complications. We report the physical characteristics, advantages, disadvantages, and radiographic appearance of the most widely utilized neonatal ECMO cannulas.

Catheterization↗
PubMed1991

An evaluation of cannulae and oxygen sources for pediatric jet ventilation.

The authors evaluated the cannulae and oxygen sources available for pediatric translaryngeal ventilation. Peak flow rates were measured and maximum tidal volumes (MTV) calculated for each combination of cannula and oxygen source. Standard 22, 20, 18, and 16 gauge intravenous catheters and a 14 gauge cannula designed for pediatric jet ventilation were tested. The oxygen sources evaluated included an adult bag-valve device; a continuous flow source regulated between 6 to 15 L/min; and a high pressure jet source regulated between 5 to 50 psi. Mean calculated MTV delivered to the cannula tip (22 g to 14 g) were: 26 to 235 mL with the bag-valve source; 91 to 236 mL with the continuous flow sources; and 58 to 1034 mL with the jet sources. Assuming that in normal subjects approximately 70% of the flow from the tip of a translaryngeal cannula reaches the distal respiratory tree, the authors conclude that bag-valve and continuous flow low pressure sources are unlikely to deliver sufficient tidal volumes to sustain normal ventilation in apneic children when coupled with standard cannulae. Jet oxygen sources with standard cannulae provide a wide range of tidal volumes sufficient to sustain normal ventilation in apneic pediatric patients.

Catheterization↗
PubMed2006

Residual air in the venous cannula increases cerebral embolization at the onset of cardiopulmonary bypass.

OBJECTIVE: When the right atrium (RA) cannula is connected to the venous return line of the cardiopulmonary bypass (CPB) circuit, air is often introduced. Air in the venous cannula may increase cerebral air embolization at initiation of CPB despite the arterial line filter. We measured the volume of air present in the venous cannula after cannulation of the RA. Transcranial Doppler quantified emboli as high-intensity transient-signals (HITS) in both middle-cerebral arteries (MCA) at the beginning of CPB. METHODS: After RA cannulation, the air column in the venous line was measured and the total volume calculated using the known lumen diameter. CPB onset was defined as the instant when the CPB machine started moving the patient's blood from the RA into the venous reservoir. Starting from CPB onset, HITS were counted: (a) until completion of the first minute on CPB (1-min count) and (b) until aortic cross clamping (pre-clamping count). RESULTS: We studied 135 patients during coronary artery bypass surgery operated on by 10 cardiac surgeons. HITS during onset of CPB were detected in 95% of patients. Median counts were 10 HITS (25th, 75th percentiles: 3, 26) at 1-min and 21 HITS (8, 51) during pre-clamping. A significant correlation was found between the volume of air in the venous cannula and the HITS counts (r=0.524, p<0.0001). Absence of retained air was associated with lower HITS counts [3 HITS (1, 11)] compared with any amount of air [13 HITS (4, 29), p=0.002)]. The volume of air in the venous cannula, the MCA mean blood flow velocity and the pre-clamping time were the only independent predictors of the pre-clamping HITS counts (p<0.001). CONCLUSION: Air in the venous cannula can result in HITS in the MCA. Minimizing the volume of air introduced into the venous cannula after cannulation of the RA can decrease cerebral air embolization at the beginning of CPB.

Aged↗
PubMed1999

The intra-aortic cannula pump: A novel assist device for the acutely failing heart.

OBJECTIVE: The intra-aortic cannula pump is a catheter pump designed to support the acutely failing heart. It expels blood from the left ventricle into the ascending aorta in a pulsatile flow pattern. The aim of the study was to analyze the hemodynamic performance of this new intracardiac support system in acute heart failure. METHODS: A 24F cannula was studied in a series of 16 sheep. Hemodynamic changes were assessed in the nonfailing, the moderately failing, and the severely failing heart. Heart failure was induced by an injection of microspheres into the left anterior descending coronary artery. The cannula was inserted through the aortic arch and introduced through the aortic valve into the left ventricle. RESULTS: Cannula insertion was feasible in all animals. Flow through the intra-aortic cannula flow was increased to a maximum of 3 L/min. No hemodynamic changes were observed in the nonfailing heart. A significant increase in cardiac output was observed in the moderately and severely reduced left ventricle (2.67 +/- 0.7 L to 3.51 +/- 0.83 L; P =.001; and 1.18 +/- 0.77 L to 2.43 +/- 0.44 L; P =.001, respectively). A drop in left atrial pressure was achieved in moderate and severe heart failure (14.1 +/- 5.93 mm Hg to 9.71 +/- 2.63 mm Hg; P =.0001; and 23 +/- 7.16 mm Hg to 11.2 +/- 2.55 mm Hg; P = 0.0001, respectively). Systolic and diastolic systemic blood pressures increased in the severely failing heart (57.3 +/- 12.8 mm Hg to 75.4 +/- 11.2 mm Hg; P =.0001; and 35.6 +/- 8.2 mm Hg to 60 +/- 14.3 mm Hg; P =.0006, respectively). CONCLUSIONS: Hemodynamic data demonstrate the beneficial effects of the intra-aortic cannula pump in moderate and severe heart failure. The intra-aortic cannula pump represents a new modality for the treatment of acute heart failure.

Animals↗
PubMed1975

Infusion thrombophlebitis and infection with various cannulas.

A prospective study was carried out of the frequency of thrombophlebitis and bacterial contamination of cannulas associated with four commonly used intravenous cannulas of differing length and chemical composition. For all cannulas the frequency of thrombophlebitis increased significantly with time. Long 'Teflon' cannulas were significantly more likely to be contaminated with bacteria and associated with thrombophlebitis than all other cannulas, while the low frequency of thrombophlebitis with butterfly stainless steel cannulas was shown to be due to their short duration of use. It is suggested that long teflon cannulas should be avoided and that infusion thrombophlebitis could be eliminated as a clinical problem by the use of intermittent short duration intravenous infusions.

Bacteriological Techniques↗