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PubMed1989

Comparison of three intestinal cannulas used to obtain repeated biopsy of the jejunal mucosa in the newborn calf.

This project was designed to develop a standardized cannulation technique which would allow repeated jejunal mucosal biopsy. Three intestinal cannulas of various designs were evaluated in a total of 25 neonatal calves. Cannula A, a T-design made of acrylic plastic, was implanted into the jejunum (2) or duodenum (7). Cannula A did not allow proper directional passage of the biopsy instrument. Peritonitis was diagnosed at necropsy in 4 calves. Cannula B, a modification of A with an angled port to facilitate the directional passage of the biopsy instrument, also proved unsatisfactory. This cannula required a larger enterotomy for placement and resulted in the death of 1 calf. Cannula C was made of tygon tubing with a proxplast mesh flange which was sutured to the serosal surface of the intestine. No intestinal leakage was observed in 14 calves fitted with this cannula. This cannula was the least expensive and allowed the biopsy instrument to be easily directed. Surgical implantation of this cannula (C) in the descending duodenum proved to be an excellent method to obtain successive mucosal biopsies of the jejunum in the neonatal calf.

Animals↗
PubMed1985

Quantitative bacteriology of peripheral venous cannulae in neonates.

In a study of 50 peripheral venous cannulae removed from neonates in the special care baby unit, quantitative and qualitative techniques for cannula culture were compared and the results correlated with detailed clinical information. High-density colonization was demonstrated on the external and internal surfaces of nine, and on the external surface alone of four, cannula tips. Internal surface colonization was always associated with heavy external surface growth. In predicting high-density colonization by quantitative methods, qualitative culture in broth was 100% sensitive and 89% specific. There was a significant association between high-density colonization of the cannula tip and hub colonization, surrounding skin colonization, longer duration of cannula insertion, and slower average infusion rate. Similar organisms were isolated more frequently from the cannula tip and the hub than from the cannula tip and surrounding skin. These findings indicate that peripheral venous cannulae are a potential source of infection in neonates, that there is no advantage of techniques that identify internal surface colonization, and that most cannula tip infections have their origin in a colonized hub.

Bacteria↗
PubMed1983

[Rate of contamination of intravenous indwelling cannulae with sideport access].

136 cannulae with valved side injection port were introduced intravenously into patients from the general surgery, urology and dermato-surgical service under clinical routine conditions. The cannulae were used from 1 up to 4 days for anaesthesia purposes as well as peri- and postoperative infusion therapy and injection of drugs through the sideport. After use the cannulae were removed following an aseptic procedure and examined microbiologically. 37 cannulae (27.2%) were found contaminated, 25 of these (18.3%) with more than 25 colonies. The infusion line (border of the conus, the interior of the conus and the lumen of the cannula) was 21 times (15.4%), the side injection port 6 times (4.4%) and the intravasal capillary surface 17 times (12.5%) contaminated. Contamination of the cannula or of parts of the cannula did not correlate well with observed signs of inflammation at the puncture site (45 patients = 33%). If, however, the contamination of the cannula is considered to be an infection risk, the addition of a side injection port to such a cannula does not increase the risk of infection. This risk is much greater via the infusion line.

Antisepsis↗
PubMed1976

A comparison of metal and plastic cannulae for performing vacuum.

A comparative study was conducted to evaluate the efficacy of a metal or flexible plastic 8 mm cannula for artificial abortion by vacuum aspiration for patients at six to 10 weeks' gestation. Complication rates, amounts of retained tissue (obtained with a curette check), frequencies of cannula obstructions and procedure times were used as criteria for determining the efficacy of the two types of cannulae. Two physicians participated in the study: one was responsible for the preliminary examination and performance of the abortion, and the other physician, who was kept unaware of the type of cannula used, was responsible for patient care after completions of the abortion to the time of the follow-up visit. Paracervical block anesthesia was used in all cases. Differences in complication rates (controlled for gestational age) between groups of subjects aborted with either the metal or flexible plastic cannula were not significantly different (p less than .05). For both patient groups shock was the most frequently reported immediate complication (2.7% in the metal cannula group, 4,7% in the flexible plastic cannula group), and leukorrhea was the most frequently reported complication at the time of follow-up (3.3% metal, 5.3% flexible plastic). Amounts of retained tissue and frequency of cannulae obstruction were similar for both groups. Procedure times were also similar for both groups (means of 5.7 minutes and 5.5 minutes, respectively, for procedures performed with the metal and flexible plastic cannulae).

Abortion, Induced↗
PubMed1985

Intraocular cannula for chronic drug delivery. Method and clinical observation.

An intraocular cannula system for chronic drug delivery was designed and tested in rabbits. The cannula was inserted through the pars plana and the tip positioned in the vitreous cavity (distal tip) in a site close to the retinal area of interest. The cannula was stabilized by a silicone plate that was sutured to the sclera. The proximal end of the cannula was attached to a larger diameter silicone tubing which served as a connector to the reservoir for chronic drug delivery. Rabbit eyes with implanted cannulas were followed clinically and electrophysiologically for up to one and a half years. They showed almost no adverse effects as a result of the implantation and cannula patency was demonstrated by the injection of sodium fluorescein through the cannula at various times following surgery. We believe that the implanted intraocular cannula, which allows chronic drug delivery, will be a valuable asset for research and possibly clinical studies.

Animals↗
PubMed2005

A new cannula to ease cement injection during vertebroplasty.

One of the main limitations of vertebroplasty is the excessive pressure required to inject a sufficient amount of cement into a vertebral body. Based on previous work that shows that approximately 95% of the injection pressure is required to deliver the cement through the cannula, we proposed a new cannula design with a larger internal diameter in the proximal section. The objective of this study is to determine whether the new cannula geometry significantly reduces the delivery pressure and eases cement injection during vertebroplasty. Two different methods were employed to examine the delivery pressure in a conventional and two redesigned cannulae: (1) analytical model: Hagen-Poisseuille's flow through a tube was used to predict the pressure drop in the cannulae; (2) experiment: first a Newtonian silicone oil and then an acrylic bone cement was injected through the cannulae at a constant rate of 4 cc/min, and the delivery pressure was recorded. Both the experimental and analytical findings confirmed that the redesigned cannula reduces the delivery pressure significantly. Specifically, when the internal diameter of the proximal section was increased by a factor of two, which is clinically feasible, the delivery pressure dropped by about 63%. The redesigned cannula appears to have the potential to improve vertebroplasty. The key benefits are that (1) it eases cement injection, (2) it can be easily integrated into the existing procedure, and (3) it is cost-effective.

Acrylates↗
PubMed1992

New method for describing the performance of cardiac surgery cannulas.

Cardiac surgery cannulas are characterized by external diameter only, which provides little information about the pressure-flow characteristics of a cannula. A system has been developed to describe pressure-flow characteristics with a single, unitless number, M, which is patterned after a Reynolds friction factor correlation. A cannula with a lower M number has a more favorable pressure-flow relationship. The M number was determined for 16 arterials cannulas ranging in size from 10F to 26F and 27 venous cannulas sized 12F to 36F. Pressure-flow characteristics vary considerably among cannulas from different manufacturers despite having similar French sizes. Clinical decisions regarding choice of cannula can be simplified by using the M number, which gives a more accurate description of the performance characteristics of a cannula than the French size designation.

Cardiac Catheterization↗
PubMed1996

Can nitrous oxide be administered effectively by nasal cannula? A preliminary report.

STUDY OBJECTIVE: To predict the inspired concentrations achieved when nitrous oxide (N2O)/oxygen mixtures are administered to patients by way of a nasal cannula. DESIGN: The method used for estimating the FiN2O is based on one employed to calculate the FiO2 obtained with a nasal cannula. We assume a tidal volume of 500 ml, a respiratory rate of 20 breaths per minute, an inspiratory time of 1 second, an expiratory time of 2 seconds, and an anatomic reservoir volume of 50 ml. The reservoir consists of the nose, the nasopharynx, and the oropharynx. Its volume is assumed to be one-third of the anatomic dead space. It is also assumed that during the last 0.5 second of expiration, there is negligible flow of expired respiratory gases. A 6 L/min flow from the cannula will completely fill the reservoir. The FiO2 or FiN2O is then calculated by assuming that during the 1 second inspiratory time period, the gases in the anatomic reservoir that are provided by the nasal cannula and a volume of air such that the sum of the components of the tidal volume equals 500 ml are inspired. SETTING: Research laboratory of a university-affiliated metropolitan medical center. MEASUREMENTS AND MAIN RESULTS: The calculated FiO2 values for 100% oxygen delivered by nasal cannula agree with those determined by others. The FiN2Os estimated were directly proportional to the cannula flow rate and the fraction of N2O delivered. At the maximum total flow rate considered, 6L/min flow, with 70% N2O (remainder O2) delivered to the nasal cannula, an FiN2O of only 0.21 was estimated due to the large volume of air inspired. The FiO2 under these conditions would only be 0.23. CONCLUSIONS: Our analysis shows that the maximum FiN2O achievable by using a nasal cannula is limited to 0.21 even with a 6 L/min flow of 70% N2O for the defined respiratory parameters.

Administration, Intranasal↗
PubMed2004

Arterial misplacement of large-caliber cannulas during jugular vein catheterization: case for surgical management.

BACKGROUND: Accidental placement of a large sheath or catheter in an artery during central venous cannulation, though rare, is a potentially devastating complication. The present study reviews our 14-year experience with this complication to determine appropriate role of surgical management. STUDY DESIGN: Review was conducted of all cases involving patients treated by the vascular surgery service from July 1989 to June 2003 for accidental placement of a large-caliber cannula (>or= 7 F) in an artery during catheterization of the jugular vein. Two management techniques were used during this period: removal of cannula followed by application of local pressure; and surgical exploration, removal of cannula under direct vision, and repair of artery. RESULTS: Eleven patients (5 men, 6 women) aged 35 to 73 years (mean age 56 years) were treated for cannulas placed accidentally in an artery. In nine patients, the cannula entered the carotid artery, and in two patients it entered the subclavian artery. Three patients had undergone placement of 8.5-F sheaths for monitoring cardiac hemodynamics, and 8 patients had triple-lumen catheters for fluid infusion or parenteral nutrition. Eight patients (three sheath, five catheter) were asymptomatic at the time of cannula removal. In three patients, the correct diagnosis was missed initially and infusion was started. All three developed neurologic symptoms. In two patients, the cannula (sheath) was pulled and pressure applied. One of them developed a stroke and the other developed a pseudoaneurysm that was treated surgically. Nine patients in whom the sheath or catheter was removed by surgical exploration had no new complications related to surgery. CONCLUSIONS: Surgical management seems to be the most effective and safe treatment of arterial misplacement of cannulas during jugular vein catheterization. Further study is needed to determine the optimum management of this potentially devastating complication.

Carotid Arteries↗
PubMed1998

Effect of aortic cannula characteristics and blood velocity on transcranial doppler-detected microemboli during cardiopulmonary bypass.

OBJECTIVES: Cerebral microemboli are responsible to a large extent for the neuropsychiatric deficits after cardiac surgery. Differences in cannula size during cardiopulmonary bypass (CPB) will result in different velocities of blood exiting the aortic cannula. This study determined whether the number of transcranial Doppler (TCD)-detected emboli in the middle cerebral artery (MCA) during CPB correlated with blood speed or the direction of flow as determined by the shape of the aortic cannula. DESIGN: Patients were studied prospectively for evidence of TCD-detected emboli. If patients met the inclusion criteria, the choice of cannula was determined by surgical preference. SETTING: All studies were conducted at a single tertiary care academic cardiac surgery hospital by a single observer. PARTICIPANTS: Thirty-two patients undergoing first-time elective aortocoronary bypass surgery who were free of neurologic dysfunction or peripheral vascular disease and weighed 60 to 85 kg were studied. Patients who had other concurrent cardiac operations or who were in cardiogenic shock were excluded. INTERVENTIONS: Three aortic cannula types for elective aortocoronary bypass surgery were used: 24F curved (n = 19), 24F straight (n = 6), and 22F straight (n = 7), with internal diameters (IDs) of 7.2, 6.6, and 5.9 mm, respectively. TCD-detected emboli were identified in the MCA. MEASUREMENTS AND MAIN RESULTS: The rate of TCD-detected emboli (0.02 to 11.4 emboli per minute) was not related to the velocity of blood (46 to 77 cm/s) and was not affected by the choice of either a straight or curved aortic cannula. CONCLUSIONS: The choice of a straight or curved aortic cannula or of a 24F versus 22F cannula may not be important with respect to the number of cerebral microemboli.

Blood Flow Velocity↗
PubMed1996

A cost-effectiveness evaluation of laparoscopic disposable versus nondisposable infraumbilical cannulas.

STUDY OBJECTIVE: To compare the safety and cost-effectiveness of disposable and nondisposable infraumbilical laparoscopic cannulas. DESIGN: Retrospective review of consecutive laparoscopic procedures performed from July 1, 1988, to June 30, 1994. SETTING: A university-affiliated hospital. Patients. The 10,459 consecutive women who underwent laparoscopies. INTERVENTIONS: A 10-mm disposable cannula was used in 529 laparoscopies and a nondisposable cannula in 9930, based on physician preference. MEASUREMENTS AND MAIN RESULTS: The only intraabdominal injuries associated with insertion of disposable and nondisposable cannulas were bowel injuries in one and three patients, respectively. The injury rates for the instruments were 19 and 3/10,000 cases, respectively, but were not statistically different (P <0.05, Fisher's two-tail exact test). The hospital cost per disposable cannula in 1994 was $63.71; the cost per procedure with the nondisposable cannula was amortized and was less than $1.35, including maintenance. CONCLUSION: Disposable cannulas were not cost effective and were associated with a higher but not statistically significant complication rate. Therefore, the more expensive disposable cannulas are not recommended.

Catheterization↗
PubMed2001

Always flush the sampling port before flushing the arterial cannula in pediatric patients.

BACKGROUND: Blood sampling from arterial lines is a frequent event in anesthesia and critical care. To avoid clot formation, both the stopcock outlet and the cannula must be flushed after sampling. We investigated in a bench experiment whether fluid flow through the cannula is affected by the sequence of flushing procedures. METHODS: Continuity of fluid delivery from a vascular cannula was gravimetrically determined using two different flushing techniques with either a syringe pump flush system or a bag flush system. The procedures comprised first flushing the stopcock towards the cannula and then towards the stopcock sampling outlet or the reverse order. Experiments were repeated in triplicate and two sets for each flushing system at hydrostatic pressures of 37 mm Hg and 74 mm Hg. RESULTS: The main finding of the study was that flushing the stopcock towards the outlet after flushing the cannula resulted in considerable retrograde aspiration volumes and zero flow times, in particular in combination with syringe pump flush systems. At a hydrostatic pressure of 74 mm Hg, the observed zero flow time at the cannula tip amounted to (mean+/-SD) 0.1+/-0.01 min with the bag flush system and 7.7+/-0.5 min with the syringe pump flush system. The related retrograde aspiration volumes were 2.2+/-0.7 microl with the bag system and 30.0+/-2.0 microl with the syringe pump system. No backflow was recorded when the stopcock was first flushed to ambient pressure and then afterwards towards the cannula. CONCLUSION: Opening a flush system to ambient pressure affects the continuity of fluid delivery, particularly when using syringe pump flush systems. After blood sampling, the stopcock outlet should be flushed first followed by cannula flushing.

Blood Specimen Collection↗
PubMed1993

The care and handling of peripheral intravenous cannulae on 60 surgery and internal medicine patients: an observation study.

The purpose of this study was to analyse the actual routines surrounding the use of peripheral cannulae and the occurrence of complications. Thirty surgery patients and 30 internal medicine patients were observed daily at a medium-sized hospital. The patients were followed from the time the cannula was inserted until after withdrawal and until both the insertion site and the vein were free from pain. The results showed that most of the cannulae were placed on the upper side of the hand and sizes most frequently used were 1.0 and 1.2 mm. The fixation was unsatisfactory in 23 cases already after the second day. Twenty-three cannulae were removed after 24 hours. Thirty-seven (62%) patients were stated to have thrombophlebitis phlebitis in different degrees. Only seven cannulae fulfilled the criteria for good cannula care and handling. The frequency of complication was especially high when fructose-glucose, antibiotics or anticoagulants were given. There was no documentation in the patient record, according to current laws in Sweden. The complications observed were redness, swelling, haematoma, subcutaneous swelling and suppurating infection. The study showed that the longer the cannula had been in situ, the greater were the complications (very distinct after 24 hours). The care and handling was unsatisfactory to very unsatisfactory in 52% of the cases. Complications can last for a very long time. In this research, pain was noted up to 5 months after the cannulae were removed.

Adult↗
PubMed2000

Transaortic inflow and outflow cannula for centrifugal mechanical assistance.

A specific cannula allowing single site transaortic inflow and outflow cannulation for centrifugal assist devices is described. The cannula is inserted through a straight 18 mm collagen coated Dacron tube anastomosed to the anterior aspect of the ascending aorta. The inflow conduit of the cannula is positioned into the left ventricle through the aortic valve, and the end hole of the outflow conduit is positioned in the ascending aorta. The cannula was evaluated in vivo in 3 adult pigs by the institution of a centrifugal pump for left ventricular support. Optimal flow varied between 5 and 6 L/min and mean aortic pressure between 55 and 70 mm Hg throughout the 3 days of left ventricular support. Recently, we employed this cannula in a patient who was not able to be weaned from cardiopulmonary bypass for the institution of left ventricular support using a centrifugal pump. The cannula provided effective inflow and outflow drainage with an optimal flow of 5.2 L/min throughout the 72 h of support. The patient was successfully weaned from support on the fourth postoperative day. This rational transaortic approach of cannulation using this specific cannula is a refined implantation technique which allows direct left ventricular inflow drainage, reduces the time of implantation, spares left ventricular myocardium, avoids bleeding that is sometimes encountered at other cannulation sites, and avoids compression of the heart by cannulas.

Aged↗
PubMed2003

New infusion cannula for prevention of retinal damage by infusion air during vitrectomy.

PURPOSE: Postoperative visual field defects are sometimes found after macular hole surgery. We have previously shown that damage to the retina by air infusion from an infusion cannula is a causative factor. To minimize such damage, we modified the infusion cannula and examined its effects experimentally. METHODS: An infusion cannula with a closed tip and openings on four sides was created. Experimentally, a vitrectomy was performed in rabbit eyes using this new infusion cannula or a conventional cannula. After fluid-air exchange at an air pressure of 40 mmHg, eyes were removed and processed for histologic examination. The areas of the retinal damage caused by air infusion were evaluated. RESULTS: The area of retinal damage created by the new cannula was reduced significantly when compared with damage from conventional cannula use. CONCLUSION: This new cannula, designed for the purpose of scattering the air infusion, can reduce retinal damage, which leads to less frequent postoperative visual field defects.

Air↗
PubMed1987

A study of the use of intravenous cannulas for medical emergencies in Newham--implications for financial savings.

A study of intravenous (i.v.) cannula usage for medical emergencies admitted to hospitals in the Newham Health District was undertaken during two defined periods (24 and 35 days). Almost half the cannulas inserted (47%) were not flushed following an initial bolus injection of heparinized saline. The duration that cannulas remained in a vein ranged from 24 hours to 8 days (median 2 days) and inflammation around the cannula site was related to the length of time since insertion but unrelated to whether the cannula was flushed regularly or to the type of fluid used. Our findings indicate a substantial wastage of i.v. cannulas due to difficulties with insertion and suggest that isotonic saline, without heparin, is effective in maintaining cannula patency for 48 hours. It is concluded that these findings are not unique to the Newham Health District and worthwhile financial savings should be achieved throughout the NHS if clinicians reconsider the indications and use of i.v. cannulas for their patients.

Adolescent↗
PubMed1991

Simple validation for the hepatic venous cannula implanted chronically in conscious rats.

A method for the detection of vena caval contamination in blood taken from hepatic venous cannulas in conscious rats was described. The procedures included 1) bolus injection of tritiated water (50 microCi) through a cannula into the abdominal inferior vena cava and 2) continuous blood sampling (less than 0.2 ml) from the hepatic venous cannula for 2 min into a 180-cm piece of Tygon tubing, starting concurrently with tracer injection. The washout of tritium was determined from samples in 15-cm sections of Tygon tubing. Because circulation from the inferior vena cava to the hepatic vein is interceded by the systemic circulation, the washout of tritium from a valid hepatic venous cannula should resemble the pattern determined elsewhere in the systemic circulation. In the current study, the reference systemic washout was determined in the superior vena cava of a group of rats similarly injected with tritiated water in the inferior vena cava. The maximum of tritium washout derived from a valid hepatic venous cannula should fall in the range encompassed by one standard deviation of the mean of the maximum of the reference (1,400 to 1,930 cpm/sample). The maximum of the washout pattern derived from the invalid cannula, which lay adjacent to the site of injection, was expected to exceed this range. On the basis of these criteria, hepatic blood flow (HBF) was determined by sulfbromophthalein (BSP) extraction in groups of rats with valid and invalid cannulas. HBF in rats with valid hepatic venous cannulas was 2.58 +/- 0.15 in the conscious state and 2.76 +/- 0.26 ml.min-1.g wet wt-1 in the ketamine-anesthetized state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Use of nasal cannula for detecting sleep apneas and hypopneas in infants and children.

We evaluated tolerance of nasal cannula (NC) by 14 infants (median age, 2.6 months) and 16 children (median age, 5.5 years) with suspected obstructive sleep apnea syndrome and compared the efficacy of the NC with that of a nasobuccal thermistor in detecting obstructive apneas (OA) and obstructive hypopneas (OH) on polysomnography traces. The relationship between cannula flow and esophageal pressure was assessed in six patients. Time spent with an uninterpretable flow signal was longer when using a cannula than when using a thermistor in infants (p < 0.05) and children (p < 0.01), and it was longer in the younger patients (p < 0.05). Among the 650 OA-OH detected by either method, only 38% were detected by both, and 58% were detected by the cannula and missed by the thermistor, so that the apnea-hypopnea index was higher with cannula than with thermistor in each age group (p < 0.01). More hypopneas than apneas were detected by the cannula and missed by the thermistor (p < 0.001). Out-of-phase thoracic and abdominal motions and/or changes in the end-tidal CO(2) signal shape were associated with 86% of OH identified by cannula. In the six patients whose esophageal pressure was measured, all respiratory events identified using a cannula were associated with increased "airway resistance." Thus, the NC is more likely than the thermistor to detect OA and OH in infants and children, and this superiority is particularly marked for hypopneas.

Adolescent↗