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PubMed1991

Arthroscopy update #9. Posterior compartment observation and instrumentation in the knee using anteromedial and anterolateral portals and an interchangeable cannula system.

The technique for routine posterior compartment observation in the knee described here uses cannulae that are 75 mm long and either 4.6 mm or 5.6 mm in diameter. Once they have been introduced, they remain in place while instruments and the arthroscope are interchanged within them. The arthroscope is attached to a bridge that connects to either cannula. Anteromedial and anterolateral portals are used with the interchangeable cannulae system. Once the arthroscope has been attached to the cannula in the anterolateral portal, an identical cannula with a blunt obturator is passed from the anteromedial portal into the posterolateral compartment under direct vision. The position of the arthroscope and blunt obturator are then reversed so that the arthroscope views the posterolateral compartment. To view the posteromedial compartment, the maneuver is repeated with the arthroscope in the anteromedial portal. The cannula with the blunt obturator is then advanced from the anterolateral portal under direct vision into the posteromedial compartment, and the position of the arthroscope and obturator are again interchanged. Hypertrophic synovium and osteophytes in the notch can be removed by passing shavers or burrs through the cannulae. Posteromedial and posterolateral portals are established with the 70 degree arthroscope under direct vision; once a cannula has been placed in a posterior portal, instrumentation and observation through the posterior cannula can be performed. The cannula from the opposite anterior portal remains in the posterior compartment. Hand and power instruments can be passed safely across the notch and into the posterior compartments while viewing the procedure through the posteriorly positioned arthroscope. The posterior cruciate ligament is then observed from the posteromedial portal while palpating the ligament with instruments entering the posterior compartment from the anterolateral portal.

Arthroscopes↗
PubMedDate not supplied

Technical and economic feasibility of reusing disposable perfusion cannulae.

The reuse of disposable devices is a potential source of significant cost savings to hospitals. Venous and arterial perfusion cannulae under new and reused conditions were selected to identify the clinical, safety, technical, logistic, and economic issues that must be addressed to realize these savings. Single- and dual-stage venous and arterial cannulae from two manufacturers were tested when new, after initial clinical use, and after a single clinical use plus up to nine simulated reuses. Reuse was simulated by end-to-end bending, coupling and uncoupling the connectors, and by two 1-hour soaks in plasma at 4 degrees C and 40 degrees C, respectively. Cannulae were decontaminated and then sterilized by a peracetic acid based liquid chemical sterilization system following each use/reuse. Sterilization was validated by eliminating Bacillus subtilis spores from the cannulae on each of five consecutive cycles. Cannulae were tested for physical changes, functional integrity, biocompatibility, and in vivo performance in sheep. A cost minimization analysis was also performed. No clinically important differences were found between new and reused cannulae, even after nine simulated reuses. Mechanical changes were less than 20% on all variables studied and were undetectable by experienced cardiac surgeons in selective evaluation. Sterilization was successfully achieved. Reusing cannulae for times would reduce the cost per procedure from $53 to $19 (64%). Perfusion cannulae tested can be safely and efficaciously used five times. This study suggests that reuse would result in a small incremental savings; however, with more expensive devices and higher-volume sterilization procedures, the savings could be exponentially greater. Although this study demonstrates that it may be technically feasible and cost-effective to reuse disposable cannulae, the U.S. Food and Drug Administration does not sanction the reuse of disposable cannulae.

Animals↗
PubMed1998

Fine-bore cannulas for peripheral intravenous nutrition: polyurethane or silicone?

The peripheral intravenous route is being used more frequently for the administration of short- to medium-term parenteral nutritional support. Dedicated fine bore cannulas have significantly reduced the incidence of thrombophlebitis. Currently available cannulas are made of polyurethane or silicone. We present our experience with a 23G silicone cannula and a 22G polyurethane alternative. Fifty-four silicone cannulas were used with a median survival of only 3 days, compared with 7 days for 90 polyurethane cannulas (P < 0.0001). Only 22% of silicone cannulas were removed electively compared with 56% of polyurethane cannulas (P < 0.00005). The most common cause for silicone cannula removal was occlusion (48%), which occurred in only 8% of polyurethane cannulas (P < 0.00001). Polyurethane cannulas develop fewer complications and are more effective in the delivery of peripheral intravenous nutritional support.

Adult↗
PubMed1990

An improved method for bonding heparin to intravascular cannulae.

The patency of chronically implanted intravascular cannulae is usually limited by thrombus formation at the cannula tip. In the present experiments, methods of improving the antithrombotic properties of the cannulae have been examined using a number of different heparin-bonding treatments. These treatments were evaluated by determining cannula patency in the thoracic aorta of a chronically cannulated rat preparation. Cannulae treated with a heparin-bonding procedure remained patent longer than untreated cannulae. Cannulae treated with tridodecylmethylammonium chloride-heparin-glutaraldehyde remained patent longest (mean patency, 13.3 days compared with 4.0 days in rats with untreated cannulae). This technique provides a simple and effective method of improving the antithrombotic properties of intravascular cannulae by bonding heparin to the lumenal and extralumenal surfaces.

Animals↗
PubMed1983

Comparison of flow differences among venous cannulas.

1. Double caval cannulas with snares provide maximum venous decompression, especially of the superior vena cava. Decompression of the right side of the heart is passive and in the heart being perfused requires venting of the right atrium by release of tapes or atrial suction. 2. Double caval cannulas without snares provide good and consistent venous and atrial decompression. The ventricle is decompressed well except when the perfused heart is in the circumflex position. 3. A large single cannula (e.g., USCI 40F) can decompress both the venous system and right side of the heart, although venous and atrial drainage are much less efficient when the heart is in the circumflex position. 4. The Sarns 51F cavoatrial cannula decompressed the venous system as efficiently as the double caval cannulas. In fact, decompression of the atrium and ventricle were consistently much better with the cavoatrial cannula than with any of the other methods. 5. Efficient venous and myocardial decompression using the 51F cavoatrial cannula requires the atrial drainage ports to be positioned in the upper middle section of the atrium. Clinically, the cannula position is correct when both the single and double marking bands on the cannula are outside the atrium.

Animals↗
PubMed2003

Cannula fracture in first trimester abortion: a case report and survey of NAF providers.

Complications in first trimester surgical abortions are uncommon. These include retained products of conception, infection, hemorrhage, perforation and hematometria. We report a case of a plastic cannula fracture. This event prompted further investigation of this issue and the factors that might increase the likelihood of its occurrence. We investigated whether the recycling of disposable cannulas may increase the frequency of cannula fracture. National Abortion Federation Members (NAF) were surveyed by mail. These providers were asked to comment anonymously on their experience with first trimester surgical abortions, resterilization of plastic cannulas and cannula fracture. The response rate was 71% after three mailings. The overall proportion of providers reporting previous cannula fractures was 9%. The rate of resterilization and reuse was 10%. Cannula resterilization did not significantly increase the likelihood of a fracture (p = 0.25). Cannula fracture is a rare complication of first trimester surgical abortion. Cannula fracture was not found to be associated with resterilization.

Abortion, Induced↗
PubMed2002

Computational model of the fluid dynamics of a cannula inserted in a vessel: incidence of the presence of side holes in blood flow.

Vascular access methods, performed by the insertion of cannulae into vessels, may disturb the physiological flow of blood, giving rise to non-physiological pressure variations and shear stresses. To date, the hydrodynamic behaviour of the cannulae has been evaluated comparing their pressure loss-flow rate relationships, as obtained from in vitro experiments using a monodimensional approach; this methodology neither furnish information about the local fluid dynamics nor the established flow field in specific clinical work conditions. Since the shear stress is a critical factor in the design of artificial circulatory devices, more knowledge should be necessary about the local values assumed by the haemodynamic parameters during cannulation. An alternative way to investigate the fluid dynamic as accurately as possible is given by numeric studies. A 3D model of cannula concentrically placed in a rigid wall vessel is presented, with the finite element methodology used to numerically simulate the steady-state flow field in two different venous cannulation case studies, with two cannulae having a central hole and two or four side holes, respectively, with the same boundary conditions. Lower velocity and shear stress peak values have been computed for the model with four side holes upstream of the central hole, in the region of the cannula where the inlet flows meet and towards cannula's outlet, due to the increased flow symmetry and inlet area with respect to the model with two side holes. Starting from the investigation of different cannula designs, numerically assessing the local fluid dynamics, indications can be drawn to support both the design phase and the device optimal clinical use, in order to limit risks of biomechanical origin. Thus the presence of four side holes implied, as a consequence of the greater inlet area and of the increased symmetry, a less disturbed blood flow, together with reduced shear stress values. Furthermore, results show that the numerical simulations furnished useful informations on the interaction between vessel and cannula, e.g. on the fluid dynamics establishing in the free luminal space left, in the vessel, by the inserted cannula.

Blood Flow Velocity↗
PubMed1998

Cervical ECMO cannula placement in infants and children: recommendations for assessment of adequate positioning and function.

BACKGROUND/PURPOSE: Cervical extracorporeal membrane oxygenation (ECMO) cannula position is often difficult to confirm by chest x-ray alone. Malposition requires a second surgery to rectify the problem. Reoperation places the patient at risk for infection, bleeding, or death. This study analyzes indications for cannula repositioning and suggests an alternative standard for intraoperative evaluation of catheter function as it relates to position. METHODS: The authors reviewed charts of 73 patients placed on arterio-venous ECMO through cervical vascular access. Reasons for repositioning of either cannula at the initial surgery or postoperatively were recorded. RESULTS: Of 73 patients, 18 (24.6%) required either arterial cannula or venous cannula repositioning. In 10 (55%) of these patients, cannula malposition was not detected by chest x-ray during the initial cannulation, and they therefore required a second cervical exploration for repositioning. CONCLUSIONS: Chest x-ray is not sensitive in demonstrating malpositioned cervical ECMO cannulae. Two-dimensional ECHO before wound closure, may be a superior, more cost effective means of assessing cannula placement and function than x-ray alone. Confirmation of cannula position and function, before wound closure, would reduce the risks involved with cervical reexploration.

Catheterization↗
PubMed1999

An in-vitro evaluation of aortic arch vessel perfusion characteristics comparing single versus multiple stream aortic cannulae.

OBJECTIVE: During extracorporeal circulation design and orientation of aortic cannulae tips mainly determine flow pattern in the aortic arch and arch vessels which is the objective of this in vitro study, comparing single versus multiple stream cannulae. METHODS: In an aortic arch glass model, jet streams of 21-24 French aortic cannulae which were inserted in the ascending aorta were directed alternatively at the different arch vessels. Flows and pressures in the arch vessels were measured at pump flows of 3-6 l/min. RESULTS: With optimal orientation of the jet stream in the aortic arch, no preferential flow in the arch vessels was seen. In the single jet stream aortic cannulae group a significant parallel increase in flow and pressure in the jet streamed arch vessels compared to the non-jet streamed arch vessels occurred (P < 0.05). With the jet stream directed on vessel 2 (left carotid vessel) there was a significant pressure and flow difference comparing the two non-jet streamed vessels with each other (P < 0.03). In the single stream 24 French cannulae the highest vessel pressure of 168 mmHg and an increase in flow of 186 ml/min was measured in the jet streamed left carotid artery at 6 l/min pump flow. The multiple stream cannulae provoked the highest vessel pressure of 106 mmHg in the corresponding jet streamed vessel and an increase in flow of 20 ml/min. CONCLUSION: Tip design of aortic cannulae and the orientation of its jet stream are potential sources of remarkable imbalance of arch vessel perfusion especially with single jet stream cannulae. These effects are more pronounced with single jet stream cannulae. These results may have important clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Aorta, Thoracic↗
PubMed2006

Modified nasal cannula for simultaneous oxygen delivery and end-tidal CO2 monitoring during spontaneous breathing.

BACKGROUND AND OBJECTIVES: Supplemental oxygen is commonly given via nasal cannulae in spontaneously breathing patients. Our modified nasal cannula with a clamp between the nasal prongs can provide O2 via one nostril and CO2 can be sampled through the other one. We have studied whether this cannula can provide oxygenation similar to a standard cannula without affecting end-tidal CO2 monitoring. METHODS: Eighty-six patients were studied during spinal anaesthesia and sedation. In 15 patients, arterial blood was sampled while O2 was delivered at flow rates of 0, 2 and 4 L min(-1), with or without clamping between the prongs of our modified nasal cannula. In the remaining 71 patients, arterial O2 was measured while using our modified nasal cannula with the clamp applied. End-tidal CO2 was recorded on a capnograph and the correlation between end-tidal and arterial values with our modified nasal cannula was investigated. RESULTS: No end-tidal CO2 waveforms were found with oxygen flow greater than 2L min(-1) without clamping between the prongs. With clamping there was a significant correlation (r = 0.83) between arterial and end-tidal CO2. A Bland-Altman analysis revealed a bias of 0.49 kPa with precision of +/-0.76 kPa. Arterial oxygenation was not affected by our modified nasal prongs with clamp as compared to the standard cannula. CONCLUSION: Our modified nasal cannula can provide continuous monitoring of end-tidal CO2 without affecting oxygen delivery in sedated, spontaneously breathing patients.

Aged↗
PubMed2002

A dedicated intravenous cannula for postoperative use effect on incidence and severity of phlebitis.

A prospective, randomised, controlled clinical study was performed to compare the incidence and severity of postoperative peripheral venous thrombophlebitis associated with a single intravenous cannula used for both intra-operative and postoperative purposes, and two cannulae, one used intra-operatively and the other postoperatively. Sixty American Society of Anaesthesiologists (ASA) physical status I or II patients aged 18-65 years undergoing elective surgery were studied. The technique of cannula insertion was standardised. After surgery, the cannulation sites were examined daily by a blinded investigator for the presence and severity of thrombophlebitis using the Baxter Scale. The two groups were similar in terms of age, gender, weight, type and duration of surgical procedures, and drugs and fluids administered both intra-operatively and postoperatively. The proportion of patients that developed phlebitis was significantly less in the two cannulae group (26.1%) than in the single cannula group (63.3%) (p < 0.0001). The severity of phlebitis was greater in the single cannula group than in the two cannulae group. These results indicate that the use of a dedicated cannula for postoperative use decreases the incidence and severity of postoperative, peripheral, cannula-related phlebitis.

Adult↗
PubMed1997

Split cannula method for accurate placement of an electrode for deep brain stimulation: technical note.

OBJECTIVE: We describe a "split cannula method" for accurate placement of a deep brain stimulation electrode. This method eliminates the risk of displacement of the electrode when withdrawing the outer guide cannula. METHOD: A separate short guide cannula is covered over the distal part of a long cannula for microrecording or macrostimulation. After confirmation of the stimulation point, the short cannula is fixed with an accessory-holding device and the long cannula is pulled out. The electrode for deep brain stimulation is inserted through the short cannula. Because this cannula is much shorter than the electrode, securing the stimulation electrode at any withdrawal stage of the outer guide cannula is always possible. RESULTS AND CONCLUSION: With this simple method, we experienced no displacement of the stimulation point during stereotactic insertion of a deep brain stimulation electrode. This method can be easily adapted to any stereotactic frame.

Brain↗
PubMed2003

Force comparison of air currents produced by a standard and modified infusion cannula.

OBJECTIVE: To develop and characterize an infusion cannula that reduces the intraocular jet forces created during fluid-air exchange. METHODS: A new infusion cannula was manufactured by adding a baffle 1.0 mm perpendicular to the distal opening of a 20-gauge infusion. The forces generated by the modified and standard cannulas were measured at a constant air infusion pressure of 50 mmHg by using a force sensor coupled to a schematic eye with eight radial positions from 0 degrees to 180 degrees along the circumference. Five different orientations relative to the baffle support of the modified cannula were evaluated at each position to assess the turbulent flow. RESULTS: The standard cannula produced a maximum force of 0.14 mmHg at 180 degrees from the sensor. The modified cannula generated a maximum pressure of 0.017 mmHg at 67.5 degrees from the sensor. Overall, the force from the modified cannula was an order of magnitude less than the standard infusion cannula (P < 0.01). CONCLUSIONS: The modifications of the new infusion cannula are passive with respect to its surgical performance. However, the additional baffle transforms laminar air currents into turbulent ones and allows dispersion of the jet forces, which should reduce barotrauma and desiccation of the retina during fluid-air exchange.

Biomechanical Phenomena↗
PubMed2002

Evaluation of different paediatric venous cannulae using gravity drainage and VAVD: an in vitro study.

Six different commercially available paediatric venous cannulae, together with a specially constructed cannula, were tested in vitro for their pressure-flow relationship. With the cannulae placed in an open reservoir, flow increased with larger diameters and higher pressures. At a pressure of 30 cm H2O, flows were 219 +/- 20, 285 +/- 13, 422 +/- 11 and 728 +/- 4 ml/min for the 12, 13.2, 14 and 16 French, respectively. No differences were found between angled and straight cannulae. When the cannulae were tested in a latex model simulating the right atrium and vena cavae, the highest flow obtained by gravity was 164 ml/min using an angled 14-French cannula. When vacuum was applied to augment venous return, a maximum flow of 179 ml/min was measured using an angled 14-French cannula. Collapse can occur when the pressure difference becomes too high in the test system. This is important, since most children are selectively cannulated in both major veins. Monitoring of the intravascular pressure might help to prevent collapse. A larger-diameter venous cannula does not always produce the highest flow when placed in a vein. This is most obvious when augmenting venous return. The design of the cannula tip, in combination with VAVD, can affect the venous return.

Catheterization↗
PubMed1999

Regional blood flow distribution from the proximal arterial cannula during veno-arterial extracorporeal membrane oxygenation in neonatal dog.

Extracorporeal membrane oxygenation (ECMO) is frequently used for treatment of patients with severe hypoxemia due to life-threatening respiratory failure. Due to this hypoxemia, the myocardium of these patients is insufficiently provided with oxygen, and consequently their cardiac function commonly deteriorates. But veno-arterial (V-A) ECMO provides oxygenated blood to the coronary arteries from ECMO circuit insufficiently. To increase the coronary blood flow distributed from ECMO, we placed the arterial cannula 1 cm above the aortic valve and evaluated the regional blood from the proximal arterial cannula in comparison with the distal cannula. Eight neonatal dogs weighting 1.8-2.5 kg were supported by V-A ECMO. The regional blood flow from the arterial cannula was measured by injection of colored microspheres into ECMO circuit. The site of the arterial cannula was changed under fluoroscopy. The bypass flow was maintained at either 50 or 100 ml/min/kg. We found that the coronary blood flow distributed from the proximal arterial cannula was significantly higher than that from the distal cannula. The proximal arterial cannula appears necessary to provide sufficient oxygenated blood to the coronary circulation during V-A ECMO. Therefore, it is expected that the increased cardiac function may improved, and that the survival rate of the patients with retarded cardiac function due to severe hypoxemia may increase by proximal placement of the arterial cannula during V-A ECMO.

Animals↗
PubMed2004

Randomised clinical trial of elective re-siting of intravenous cannulae.

INTRODUCTION: Peripheral venous thrombophlebitis (PVT) represents a considerable source of iatrogenic morbidity, occurring in about 20% of hospital in-patients. The aim of this prospective randomised study was to investigate the effect of elective change of intravenous cannulae on the incidence of PVT in hospital in-patients. PATIENTS AND METHODS: General medical and surgical inpatients requiring intravenous therapy were randomised into control (n = 26) or study (n = 21) groups. Cannulae in the control group were only removed if the site became painful, the cannula dislodged, or there were signs of PVT. Cannulae in the study group were changed electively every 48 h. All patients were examined daily for signs of PVT. RESULTS: Peripheral venous thrombophlebitis developed in 11/26 patients in the control group and 1/21 patients in the study group (P = 0.003). Elective change of cannulae did not significantly increase the total number of cannulae sited (41 cannulae in the control group versus 43 in the study group). CONCLUSIONS: Elective change of cannulae resulted in a significant reduction in the incidence of infusion phlebitis. The authors recommend that elective re-siting of intravenous cannulae becomes standard practice for all patients requiring intravenous therapy.

Adult↗
PubMed1991

Technical note: a double L intestinal cannula for cattle.

A double L-shaped intestinal cannula was developed in an attempt to overcome problems observed previously with simple T-type cannulas. The cannula was constructed from cyclopolyvinyl chloride water pipe fittings. Construction materials were fairly rigid, but by connecting the split cannula pieces with elastic castration bands the cannula had some flexibility. Placing a short cone over the exposed cannula barrel reduced mechanical damage to the intestine. The double L cannula required a much smaller incision in the intestine during surgical insertion than a T-type cannula; it also simplified replacement. Construction is described; use and performance of the cannula has been satisfactory.

Animals↗
PubMed1991

Why flush peripheral intravenous cannulae used for intermittent intravenous injection?

We aimed to investigate whether regular flushing of peripheral intravenous cannulae used for intermittent injections with heparin-saline, in a unit for acute medicine for the elderly, reduced the incidence of complications necessitating cannula removal. We wanted to see if this could also prolong the time that cannulae may remain functional in situ. In a prospective, open study, 50 consecutively inserted cannulae were flushed regularly and a subsequent 50 consecutive cannulae were not flushed. The incidence of complications necessitating removal was not significantly different between the two groups (18% flushed, 22% unflushed). Overall, only 5% of cannulae were removed because of blockage. Heparin-saline flushes did not significantly increase the time that cannulae remained in situ. Antibiotic use was found to be associated with an increased rate of complications necessitating cannula removal. We found no significant advantage in heparin-saline flushing of peripheral intravenous cannulae used for intermittent administration of medications.

Aged↗