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PubMed1993

Effect of needle changing and intravenous cannula collection on blood culture contamination rates.

STUDY OBJECTIVES: We tested the hypotheses that blood culture positivity and contamination rates were not increased by not changing needles between venipuncture and inoculation of blood culture bottles or by taking blood for culture by freshly inserted IV cannulae. DESIGN: A prospective study of blood cultures collected by venipuncture or IV cannulae taken from an emergency department population. Venipuncture samples were randomized into needle change (standard method) or no needle change before inoculation into blood culture bottles. PARTICIPANTS: Nine hundred forty patients requiring blood cultures after assessment in the ED. INTERVENTIONS: A standard disinfection procedure using 0.5% chlorhexidine in 70% alcohol was used. Blood was collected by venipuncture and inoculated with or without needle change. Blood collected by IV cannula was inoculated with a fresh needle applied to the collection syringe. MEASUREMENTS AND MAIN RESULTS: There was no statistically significant difference in contamination rates for blood collected by venipuncture with no needle change (6.4%) compared with needle change (4.2%, P > .30). No significant difference in contamination rates was noted for blood taken by freshly inserted IV cannulae (4.3%) compared with venipuncture with needle change after sampling (4.2%, P > .90). Some problems with randomization resulted in unequal numbers in the needle-change (286) versus no-needle-change (141) subgroups, and this may have introduced bias. A higher rate of pathogen growth was observed in blood taken by IV cannula (11.4%) compared with the standard method (6.3%) (P < .025). A significantly greater rate of Gram-negative sepsis was noted in the IV cannula group (6.6%) compared with direct venipuncture with needle change (1.1%) and no needle change (4.2%, P < .01). CONCLUSION: The results of this study do not support the practice of changing needles before inoculating blood samples into blood culture bottles. Collection of blood for culture through freshly inserted IV cannulae is associated with a low contamination rate and is an acceptable alternative to direct venipuncture. Sources of bias in this study suggest that further research is needed to determine the optimal technique for collecting blood cultures.

Bacteriological Techniques↗
PubMed2003

Pyrodictium cannulae enter the periplasmic space but do not enter the cytoplasm, as revealed by cryo-electron tomography.

The hyperthermophilic archaeon Pyrodictium grows in the form of a macroscopically visible network. It consists of cells entrapped in an extracellular matrix of hollow tubules, the "cannulae." Here, we present the three-dimensional structure of a single cell in conjunction with two extracellular cannulae, as determined by cryo-electron microscopy. To achieve this, the information from two independent tilt series of the same specimen was combined, with the specimen rotated in the second series. In the three-dimensional tomographic reconstruction, we were able to trace the two cannulae in their full length, in particular, also inside the cell. One cannula enters the periplasmic space, while the other cannula contacts the surface of the cell, the S-layer. This indicates that the cannulae interconnect individual cells with each other on the level of their periplasmic space; we do not, however, have evidence that they enter the cytoplasm of the cells. The implications of these data for possible functions of the cannulae are discussed.

Cryoelectron Microscopy↗
PubMed1998

Left centrifugal pump cardiac assist with transseptal percutaneous left atrial cannula.

Left cardiac support postcardiotomy requires a second operation for removal of the atrial cannula following weaning from assistance. To avoid the risk of this procedure, we used a transseptal cannula prototype. The cannula was introduced percutaneously through the femoral vein and advanced into the left atrium guided by the finger of the surgeon. Optimal positioning of the tip of the cannula was verified by perioperative transesophageal echocardiography. A long arterial cannula was positioned in the descending aorta via the femoral artery and a Carmeda circuit with a centrifugal pump was connected to both cannulas. This procedure was used in 3 patients with low cardiac output who underwent emergency surgery, a 63-year-old patient referred for aortic and mitral valve replacement, a 54-year-old man for aortic valve replacement, and a 64-year-old patient in the acute phase of myocardial infarction after myocardial revascularization. The assistance was used systematically at the end of the operation. The assist flow was 1.2-2.6 L/min. The patients were all weaned from support between 18 h and 8 days later. No complications related to the device occurred. Both cannulas were removed surgically from the femoral vessels without reopening the chest. This new procedure is of interest for 2 reasons: the systematic implantation allows for early assistance, and the use of a percutaneous approach avoids the risk of reopening the chest. More cases are needed to confirm this initial good impression.

Aortic Valve Insufficiency↗
PubMed2002

Flow dynamic comparison of peripheral venous cannulas used with centrifugal pump assistance in vitro.

Because of the risk of vein collapse, the benefits of using a centrifugal pump to assist venous drainage for cardiopulmonary bypass are limited when the tips of peripheral cannulas are maintained within the vena cava. Using a mock circuit including 20 mm diameter latex tubing to mimic a vena cava, we compared the performance of 6 commercially available peripheral venous cannulas and attempted to determine potential factors influencing maximal flow drainage before vein collapse. A close correlation was observed with the total hole area of the cannula. Best performance (5.10 +/- 0.08 L/min) was obtained with an 8 mm internal diameter (ID) cannula and 343 mm2 total hole area. A larger cannula (ID 9.2 mm) with only 209 mm2 total hole area drained 5.03 +/- 0.05 L/min whereas a smaller cannula (ID 6.7 mm) with a total hole area of 586 mm2 also allowed a similar flow of 5.03 +/- 0.12 L/min. Therefore, the total hole area appears to be a critical factor in designing peripheral cannulas used in restricted chambers such as vena cavae.

Cardiopulmonary Bypass↗
PubMed1996

Thrombosis of the arterial cannula during extracorporeal membrane oxygenation in a full-term newborn infant.

The authors report a rare case of cannula thrombosis during extracorporeal membrane oxygenation (ECMO). A full-term newborn infant was successively placed on single-cannula veno-venous extracorporeal lung support and then on veno-arterial ECMO, because of persistent pulmonary hypertension. At 140 hours of ECMO, the infant displayed general cyanosis except in the right arm. Since asymmetric hypoxemia during ECMO may be related either to cannula malposition or to a tip thrombosis, a chest x-ray after contrast injection into the arterial line of the circuit was performed. It showed an opacification of the whole cannula but for the last distal centimeter, and of the vascular bed extending from the right subclavian artery. Cannula thrombosis was suspected and confirmed by removal of the arterial cannula. Demonstration of cannula thrombosis by opacification of the arterial line of the circuit indicates catheter removal.

Catheterization, Peripheral↗
PubMed2006

Ex vivo experiments of a new injection cannula for vertebroplasty.

STUDY DESIGN: An experimental study using cadaveric vertebrae. OBJECTIVES: To measure the injection pressure in an ex vivo model and determine whether the redesigned cannula, featuring 2 distinct sections of different diameters, significantly reduces the injection pressure. SUMMARY OF BACKGROUND DATA: An important limitation of vertebroplasty is the excessive pressure required to inject sufficient cement. The redesigned cannula accounts for the "bottleneck" of the injection previously identified. It has a distal section that is adapted to the pedicles and a proximal section with a larger diameter. METHODS: Two cannulas were tested, a conventional 8-gauge and the redesigned cannula. There were 3 mL of cement injected in small strokes of 0.75 mL into the left and right hemivertebrae. A custom-made injection device monitored the injection pressure and cement volume. RESULTS: Average injection pressure was 2.3 MPa, often approaching the human physical limit and resulting in insufficient filling. The average pressure of the redesigned cannula was 44% lower than that of the conventional cannula, a highly significant result (P < 0.001). CONCLUSION: The new cannula may improve vertebroplasty by significantly easing cement injection. It is cost effective and can be easily integrated into the existing procedure.

Arthroplasty↗
PubMed2003

Reduced rate of microembolism by optimized aortic cannula position does not influence early postoperative cognitive performance in CABG patients.

BACKGROUND AND PURPOSE: The number of microemboli as measured by Doppler ultrasound during coronary artery bypass grafting (CABG) can be reduced by positioning the arterial cannula into the aorta descendens. The aim of this study was to prospectively evaluate whether this alternative aortic cannulation procedure leads to better neuropsychologic outcome early after surgery along with embolus reduction. METHODS: Sixty patients with elective CABG were randomized to either using a short aorta ascendens cannula or an elongated cannula placed in the aorta descendens. All patients were tested by seven neuropsychologic tests preoperatively. Intraoperative embolus detection could be performed by transcranial Doppler in 32 patients. The neuropsychologic tests could be repeated serially until the 9th postoperative day in 54 patients. Patient groups did not differ in terms of preoperative psychometric performance and of the surgical characteristics except cannula positioning. All data were analyzed by a blinded assessor. RESULTS: Neuropsychologic test scores showed in all individual patients a transient decline with subsequent recovery, but did not differ significantly between the groups except for the letter cancellation test at discharge favoring the patients with the longer cannula (102.3 +/- 11.6 vs. 94.5 +/- 11.5 mean +/- SD; p = 0.025). In the subgroup who had Doppler sonography, neuropsychologic test scores did not differ between the groups. However, microembolic signals were markedly reduced in patients with the elongated cannula (median 174.5 vs. 413.0; p = 0.011). CONCLUSIONS: Though reducing brain microembolism, use of an elongated aortic cannula does not appear to influence overall cognitive performance early after CABG in this pilot study.

Aged↗
PubMed2002

Hemodynamic comparison of two different pediatric aortic cannulas.

Any extracorporeal blood treatment requires an adequate and safe connection to the circulation. For cardiopulmonary bypass procedures, aortic and venous cannulas are utilized. However, the performance of these cannulas is not only dependent on their size (diameter), but also on their complete geometric design. In this paper two aortic cannula designs are evaluated hemodynamically for two different sizes (8, 10 Fr) both with aqueous fluids and with blood. Using the novel concept of equivalent diameter, a new performance parameter, and the theory of dynamic similarity the results obtained with different fluids can be compared. Data points of one cannula can be fitted to a parabolic equation. There is a significant performance difference between the two 8 Fr cannulas. The 10 Fr cannulas differ non-significantly except when water is used. Equivalent diameters obtained with water in the turbulent region are significantly higher than those obtained with fluids that have a higher viscosity (blood and aqueous glycerine mixture). The latter fluids have comparable viscosities and render an equal equivalent diameter. The coefficients of their proper parabolic fit lines can easily be recalculated into each other. This provides a simple method to quickly determine pressure drops in cannulas in the operating room.

Aorta↗
PubMed2002

In vitro hydrodynamics of the Embol-X cannula.

BACKGROUND: Prevention of intraoperative plaque dislodgement in patients with atherosclerotic ascending aorta by development of innovative aortic cannula designs gains growing interest in cardiac surgery. To increase knowledge about the hydrodynamics of the innovative Embol-X cannula, which includes an intra-aortic filter device targeting at atheromatous emboli capture, was the aim of the present study. METHODS: Pressure gradients and back pressures of the Embol-X cannula were measured at varying flow rates in a mock circulation and compared with two commonly used single-stream cannulae. RESULTS: At a flow rate of 5.5 l/min, pressure gradients across the Argyle and the RMI cannulae were 48% and 62% and back pressures 25% and 47% lower than the corresponding values across the Embol-X cannula. CONCLUSIONS: The novel concept of integrating a filter device may provide clinical advantages concerning neurologic outcome. Further in vivo studies seem to be desirable to obtain more information concerning the clinical effects of the Embol-X cannula hydrodynamics.

Cardiac Surgical Procedures↗
PubMed2002

A prospective, within-patient comparison between metal butterfly needles and Teflon cannulae in subcutaneous infusion of drugs to terminally ill hospice patients.

We performed a prospective study of hospice in-patients requiring a syringe driver (SD), to determine the site duration and tolerability of metal butterfly needles compared to Teflon cannulae. Using patients as their own control, prescribed medications were divided equally between two SDs (Graseby MS16a), for delivery over 24 h. A butterfly infusion (Flosafer, 25 gauge) was connected to one SD and a Teflon cannula (Abbocath-T, 24 gauge), to the second. These were inserted subcutaneously (s.c.) on opposite sides of the body at comparable sites; oedematous, broken or painful sites were excluded. SD sites were examined at 4-hourly intervals. The study was terminated when both devices had required resiting. Needle and cannula times were compared using the Wilcoxon signed rank test. Thirty patients entered the study, 13 males and 17 females, mean age (standard deviation): 70 (11) years. Thirteen patients completed the study. Nine patients died and eight patients discontinued the study before both needle and cannula had been resited. All 30 patients are included in the analysis. The time from insertion to resiting of the cannula was significantly longer than the needle: P < 0.0002, median (range) 93.5 (22.8-263.5) h versus 42.8 (7.5-162.3) h, respectively. The cost of the needle versus cannula is 1.93 Pounds versus 2.51 Pounds, respectively. Teflon cannulae have a median life span twice that of metal butterfly needles and are a cost-effective alternative for administration of medications by s.c. infusion in terminally ill patients.

Aged↗
PubMed2005

Oxygen delivery through nasal cannulae to preterm infants: can practice be improved?

OBJECTIVE: Oxygen delivery through nasal cannulae to convalescent preterm infants is a common but largely unstudied practice. To learn more about current nasal cannula oxygen delivery practices, we examined the variations in oxygen delivery through nasal cannulae among the centers of the Neonatal Research Network, the frequency of prescription of low levels of oxygen, and the success of weaning to room air. We hypothesized that some infants treated with oxygen through nasal cannulae were receiving oxygen levels equivalent to those of room air. METHODS: This was a descriptive, nested, cohort study of nasal cannula oxygen prescription among 187 infants with birth weights of <1250 g. All infants were studied at a postmenstrual age of 36 weeks, with a timed oxygen reduction challenge to establish their ability to be weaned to room air. The results of this challenge were compared with the fraction of inspired oxygen (FIO2) delivered, calculated as effective FIO2. Infants who maintained oxygen saturation values of > or =90% during oxygen weaning and during a 30-minute period in room air were defined as passing the challenge. RESULTS: Fifty-two infants (27.8%) were receiving oxygen concentrations and flow rates through nasal cannulae that delivered an effective FIO2 of <0.23, of whom 16 were receiving oxygen concentrations and flow rates that delivered an effective FIO2 of 0.21. In addition, 22 infants (11.8%) were prescribed room air through nasal cannulae intentionally. Seventy-two percent of those prescribed an effective FIO2 of <0.23 passed the room air challenge. CONCLUSIONS: Prescription of oxygen with combinations of flow rates and oxygen concentrations that delivered a low effective FIO2 was common. We speculate that some of this, including the inadvertent prescription of an effective FIO2 equivalent to that of room air, is related to lack of knowledge of the effective FIO2. Routine calculation of effective FIO2 values may prompt earlier trials of room air and thus reduce unnecessary days of oxygen therapy.

Humans↗
PubMed1992

Technical note: development of a duodenal cannula for sheep.

A single T-shaped duodenal cannula of silicone rubber with a gutter-type small inner flange was developed for sheep. The barrel of the cannula was 24 mm long with an internal diameter of 12 mm. A polyester surgical mesh (100 mm x 100 mm) was connected to the barrel of the cannula as an anchor. Fibrous tissues grew on the polyester mesh anchor and adhered firmly to the serosa of the intestine, thus leaving no gap and, hence, preventing any leakage of intestinal contents from the side of the fistula. The small (24 mm in diameter) and thin (3 mm in thickness) outer flange of the cannula became buried in the wool and prevented any mechanical disturbance of the cannula by the activity of the animal. The elasticity of the silicone rubber prevented distortion of the duodenum around the barrel of the cannula. No erosion of the tissue between the inner flange of the cannula and the mesh was seen in postmortem observations.

Animals↗
PubMed2005

[The advantage of our original straight cannula for tracheostoma].

Patients with head and neck cancers often require use of a tracheal cannula due to stenosis of the permanent tracheostoma following total laryngectomy. However, a cannula that is designed for a multi-purpose tracheotomy frequently presents a problem, when placed in a permanent tracheostoma. To resolve this difficulty, we developed a straight cannula that fits most permanent tracheostomas. We achieved a straight design by removing the curvature of a cuffed tracheostomy single cannula (size 12: Koken Co., Ltd.). To facilitate installation by the patient without assistance, silicone was used because it is softer than similar conventional products. By making the cannula diameter slightly larger, immobilization with a strap is lomger needed. Our cannula was used in 14 patients following surgery for the laryngeal, hypopharyngel, esophageal carcinomas. The cannula fit well and reduced the respiratory discomfort in all patients.

Aged↗
PubMed2001

Effect of inner cannula removal on the work of breathing imposed by tracheostomy tubes: a bench study.

BACKGROUND: Tracheotomy has been used to assist in weaning patients from mechanical ventilation. Some patients fail to be weaned from the ventilator despite tracheostomy. We hypothesized that removing the inner cannula from the tracheostomy tube would decrease the tube's imposed work of breathing (WOB(IMP)). METHODS: The hypothesis was tested using a lung model, by measuring the change in WOB(IMP) when the inner cannula was removed. A mechanical lung model was developed using a test lung to simulate a spontaneously breathing patient. WOB(IMP) was measured with a commercially available lung mechanics monitor. Shiley size 6, 8, and 10 nonfenestrated tracheostomy tubes were tested with the inner cannula in and out. Breathing conditions were simulated using tidal volumes (V(T)) of 300 and 500 mL matched with breathing frequencies of 12, 24, and 32 breaths per minute, by using a ventilator to simulate spontaneous breathing through one side of the test lung. RESULTS: Under all the tested breathing conditions, WOB(IMP) for each of the 3 tracheostomy tubes was significantly reduced (p < 0.05) when the inner cannula was removed. Also, as simulated spontaneous inspiratory flow demand increased (ie, as V(T) and/or frequency were increased), WOB(IMP) also increased, and vice versa. With the cannula removed, WOB(IMP) was not significantly different between the size 6 and 8 tubes nor between the size 8 and 10 tubes when V(T) was 300 mL and frequency was 12 breaths per minute. CONCLUSIONS: There was a significant decrease in WOB(IMP) with each tube when the inner cannula was removed. WOB(IMP) increased with an increase in inspiratory flow demand (ie, increase in V(T) and/or frequency), as well as when tube size decreased. In weaning a tracheostomized patient from mechanical ventilation, increasing the internal diameter of the tube by removing the inner cannula may be beneficial. Further study is needed to determine if these findings are clinically important.

Analysis of Variance↗
PubMed2002

Laboratory evaluation of the pressure flow characteristics of venous cannulas during vacuum-assisted venous drainage.

Vacuum-assisted venous drainage (VAVD) is frequently used to increase venous return through smaller venous cannula and reduced venous line size. The purpose of this study is to determine the maximal flow rates achieved through various venous cannula with varying amounts of negative pressure applied during VAVD. The first test circuit consisted of 25 different venous cannulae connected to 3/8 inner diameter tubing on the positive side of a centrifugal pump. Flows through the cannula were measured at a line pressure of 20, 40, 60, and 80 mmHg. The second circuit consisted of the test cannula connected to 3/8-in inner diameter tubing, a hard-shell venous reservoir, and flow probe placed on the venous line. Using a vacuum regulator and venous line pressure monitor, flow rates were measured through each cannula at -20, -40, -60, and -80 mmHg of vacuum. The results show a mean correlation of 0.989 between the two methods of flow measurement (p < .001). Mean flow rates were established at 40 and 80 mmHg using both methods. For each 40 mmHg increase using vacuum, blood flow was increased by 42.08 +/- 0.09%. These data have been incorporated into a chart to allow the perfusionist to identify the negative pressure necessary to achieve venous return when using specific venous cannula during VAVD.

Blood Flow Velocity↗
PubMed1990

[Does a cone-shaped cannula needle offer an advantage in spinal anesthesia?].

The so-called atraumatic spinal cannula of Sprotte is a modification of the Whitacre spinal needle. It consists of a conical tip with a lateral opening. This cannula (24 G) is said to cause a very low incidence of postspinal headache. In a prospective study, it was compared to a 25 G cannula with a Quincke tip. PATIENTS AND METHOD. The study was carried out on 500 patients who received spinal anesthesia for operations on the lower extremities. The cannulas were randomly assigned to the patients. Puncture characteristics and number of incomplete blocks were evaluated. Postoperatively patients were interviewed on days 1, 3, 5, and 7. Neither the subjects nor the investigator were aware of the type of cannula used. RESULTS. There were no differences with regard to age and sex; 80% of the patients ranged between 15 and 55 years, with a homogeneous spread. Performance of the block was superior with the Sprotte cannula and the incidence of incomplete blocks was lower (1.6% vs 7.8%, P = 0.0011). There was no significant difference with regard to postspinal headache (8.2% vs 7.8%). CONCLUSIONS. The atraumatic cannula had better puncture characteristics, but there was no statistically significant difference with regard to postspinal headaches.

Adolescent↗
PubMedDate not supplied

Maximum blood flow rates for arterial cannulae used in neonatal ECMO.

The arterial cannulae used in neonatal ECMO cause hemolysis and red blood cell damage at elevated blood flows. Hemolysis in extracorporeal circuits has been found to occur with shear stress greater than 132 dynes/cm2, turbulence as measured by Reynold's number greater than 1,000, and velocity greater than 120 to 200 cm/sec. These parameters need to be considered when sizing the proper arterial cannula for a required flow rate. In-vitro measurements of the pressure drop across six arterial cannulae at varying flow rates were performed using human blood with a hematocrit of 43%. Shear stress, Reynold's number, velocity, and pressure drop were calculated for each catheter at flow rates from 50 to 1,000 cc/min. The maximum mean flow rate to maintain the shear stress, Reynold's number, velocity, and pressure drop within the accepted range, was determined for each cannula. Recommended maximum blood flow rates for each of the six cannulae are given. Internal diameter, length, and cannula geometry appear to be the factors most affecting the flow achievable without causing red blood cell damage and hemolysis. Ten French Biomedicus, 10 French Cook, and 10 French Elecath arterial cannulae appear best suited to deliver the range of blood flow rates used in neonatal ECMO.

Blood Flow Velocity↗
PubMed1994

[Intravenous cannulae: complications arising from their use and analysis of their predisposing factors].

BACKGROUND: The aim of this study was to analyze the complications derived from the use of intravenous cannulae with particular attention being paid to the possible predisposing factors. METHODS: A prospective follow up of 569 intravenous cannulae placed in the emergency department or the medical ward of a county hospital was carried out. 492 of these cannulae were peripheral (PC) and 77 central inserted through peripheral veins (CPVC). RESULTS: Fifty-one percent of the catheters were withdrawn due to complications with the most frequent being phlebitis (35%), followed by extravasation (11.5%). The mean time in situ was 3.61 +/- 3.2 days. The daily risk of complications ranged from 2 to 9% for the CPVC (non significant differences) and between 15% (day 1) and 30% (6 or more days) for the PC. In the latter case there were no differences in the daily specific rate of complications after the first 24 hours. The probability of a catheter remaining in place more than three and six days without complications was 51% and 31%, respectively for the CP and 91% and 87% for the CPVC (p < 0.0001). Of the variables analyzed, age > 65 years, female sex, insertion of the cannula into the back of the hand, the fact of the route being peripheral without the administration of heparin were significantly associated to the development of complications, while the intravenous administration of aminophillin was associated with the appearance of phlebitis. Thirteen percent of the catheters withdrawn due to phlebitis were infected. CONCLUSIONS: The complication most frequent observed in intravenous cannulation was phlebitis, an entity which is generally not of an infectious nature. The risk of unspecific complications every day during catheterization is constant in the case of central peripheral vein cannulae as well as in peripheral cannulae which do show problems during the first 24 hours after placement. Insertion of the cannulae into the veins of the back of the hand, female sex, advanced age and intravenous administration of certain drugs influence in the development of phlebitis.

Actuarial Analysis↗