In vivo quantitative assessment of catheter patency in rats

Formation of fibrin sleeves around catheter tips is a central factor in catheter failure during chronic implantation, and such tissue growth can occur despite administration of anticoagulants. We developed a novel method for monitoring catheter patency. This method recognizes the progressive nature of catheter occlusion, and tracks this process over time through measurement of changes in catheter resistance to a standardized 1 mL bolus infusion from a pressurized reservoir. Two indirect measures of catheter patency were used: (a) reservoir residual pressure and (b) reservoir discharge time. This method was applied to the study of catheter patency in rats comparing the effect of catheter material (silastic, polyurethane, Microrenathanetrade mark), lock solution (heparin, heparin/dexamethasone) and two different cannulation sites (superior vena cava via the external jugular vein, inferior vena cava via the femoral vein). Our findings reveal that application of flexible smaller-size silastic catheters and a dexamethasone lock solution resulted in prolonged catheter patency. Patency could be maintained over nine weeks with the femoral vein catheters, compared with five weeks with the external jugular vein catheters. The current method for measuring catheter patency provides a useful index for the assessment of tissue growth around the catheter tip. The method also provides an objective and quantitative way of comparing changes in catheter patency for different surgical methods and catheter types. Our method improves on the conventional method of assessing catheter occlusion by judging the ability to aspirate from the catheter.     

Femoral Arterial and Venous Catheterization for Blood Sampling,Drug Administration and Conscious Blood Pressure and Heart Rate Measurements

In multiple fields of study, access to the circulatory system in laboratory studies is necessary. Pharmacological studies in rats using chronically implanted catheters permit a researcher to effectively and humanely administer substances, perform repeated blood sampling and assists in conscious direct measurements of blood pressure and heart rate. Once the catheter is implanted long-term sampling is possible. Patency and catheter life depends on multiple factors including the lock solution used, flushing regimen and catheter material. This video will demonstrate the methodology of femoral artery and venous catheterization of the rat. In addition the video will demonstrate the use of the femoral venous and arterial catheters for blood sampling, drug administration and use of the arterial catheter in taking measurements of blood pressure and heart rate in a conscious freely-moving rat. A tether and harness attached to a swivel system will allow the animal to be housed and have samples taken by the researcher with minimal disruption to the animal. To maintain patency of the catheter, careful daily maintenance of the catheter is required using lock solution (100 U/ml heparinized saline), machine-ground blunt tip syringe needles and the use of syringe filters to minimize potential contamination. With careful aseptic surgical techniques, proper catheter materials and careful catheter maintenance techniques, it is possible to sustain patent catheters and healthy animals for long periods of time (several weeks).     

A self-powered constant infusion device for use in unrestrained rats

We developed a device that delivers fluid through a catheter at a constant rate and can be used in conscious animals to solve a variety of problems. For example, this device can be used for delivering drugs and maintaining intravascular catheter patency. The device provides infusions at low flows (1.0-1.5 ml/day), so that experimental agents may be administered with minimal volume loading of the rat. Arterial and venous catheter patency is maintained by infusion of heparinized saline through indwelling catheters attached to the device. The catheters exit from the rat in the intrascapular area and are routed through a protective spring to the device, which is suspended above the cage. The catheters may be attached to pressure transducers, blood may be sampled, and injections or infusions may be made without disturbing the rat. Because the device is self-contained, it can be suspended by a fluid-free swivel that rotates through 360 degrees, providing minimal restraint. The device has been used successfully to measure arterial and central venous blood pressures in two studies using rats.     

A Retrospective Study of Preferable Alternative Route to Right Internal Jugular Vein for Placing Tunneled Dialysis Catheters: Right External Jugular Vein versus Left Internal Jugular Vein

Background

Right internal jugular vein (IJV) is a preferred access route for tunneled (cuffed) dialysis catheters (TDCs), and both right external jugular vein (EJV) and left IJV are alternative routes for patients in case the right IJV isn’t available for TDC placement. This retrospective study aimed to determine if a disparity exists between the two alternative routes in hemodialysis patients in terms of outcomes of TDCs.

Methods

49 hemodialysis patients who required TDCs through right EJV (n = 21) or left IJV (n = 28) as long-term vascular access were included in this study. The primary end point was cumulative catheter patency. Secondary end points include primary catheter patency, proportion of patients that never required urokinase and incidence of catheter-related bloodstream infections (CRBSI).

Results

A total of 20,870 catheter-days were evaluated and the median was 384 (interquartile range, 262–605) catheter-days. Fewer catheters were removed in the right EJV group than in the left IJV group (P = 0.007). Mean cumulative catheter patency was higher in the right EJV group compared with the left IJV group (P = 0.031). There was no significant difference between the two groups in the incidence of CRBSI, primary catheter patency or proportion of patients that never required urokinase use. Total indwell time of antecedent catheters was identified as an independent risk factor for cumulative catheter patency by Cox regression hazards test with an HR of 2.212 (95% CI, 1.363–3.588; p = 0.001).

Conclusions

Right EJV might be superior to left IJV as an alternative insertion route for TDC placement in hemodialysis patients whose right IJVs are unavailable.     

Pulmonary hypertension induced with an intra-arterial balloon: an alternate mechanism

The Laks catheter is a triple-lumen balloon catheter used to distend the canine main pulmonary artery while recording right ventricular pressure and the arterial pressure distal to the balloon. A rise in arterial pressure reported to occur during distension has been attributed to vasoconstriction rather than passive obstruction by the balloon. We tested this in six anesthetized dogs by inflating the Laks catheter-balloon while recording pressure distal to the balloon from the Laks catheter as well as from additional catheters in right and left pulmonary arteries placed retrogradely through lobar branches following thoracotomy. We found that balloon inflation increased pressures in the arterial port of the Laks catheter and in the left pulmonary artery catheter but reduced it in the right pulmonary artery. Tightening a snare around the right pulmonary artery had the same effects on pressures. Similar results were obtained while cardiac output was controlled by left ventricular bypass perfusion in four dogs. We conclude that the Laks catheter-balloon obstructs flow to the right lung and that the arterial pressure rise recorded in it during balloon inflation cannot be distinguished from that caused by occlusion of the right pulmonary artery.     

Chronic central vein catheterization for intraoperative and long-term venous access in swine

Chronic venous access and repeated blood sampling for research purposes in large swine ideally should be possible without sedation, restraint or direct venipuncture of deep vessels. An operative technique of cranial vena cava catheterization and chronic catheter maintenance methods are described which were used successfully in the placement of 11 silicone rubber catheters in 10 animals. All were used for repeated blood sampling, as well as intraoperative infusion of medications and large fluid volumes. Long term patency was excellent with 10 catheters patent at the end of the study interval, up to 14 weeks after insertion. Serial blood sampling was accomplished easily without restraint. Catheter damage, infection or malfunction was rare. Proper maintenance and careful aseptic blood sampling render the cranial vena cava catheter a safe and reliable alternative to direct venipuncture in swine.     

A technique to study splanchnic metabolism in the unrestrained conscious pig

In recent years similarities recognized between porcine and human anatomy and physiology have made the pig an experimental animal of considerable value in biomedical research. We developed a pig model for unrestrained repeated sampling of portal and arterial blood, and selectively of small and large bowel veins. Catheters were inserted, under halothane anesthesia, in ten female crossbred (Yorkshire x Dutch Landrace) piglets (8 weeks; 20 +/- 2 kg). After recovery for at least 3 days the catheters were used for sampling of blood. Aortic and portal catheters patency rates were 60% at day 24. For the small bowel catheters, a patency rate of 30% was seen at day 24. The large bowel patency rate was 30% at day 10. These results are promising because they allow long-term metabolic splanchnic research in unrestrained piglets.     

Repetitive blood sampling in unrestrained and unstressed mice using a chronic indwelling right atrial catheterization apparatus

A re-usable mobile catheterization apparatus was developed that permits multiple blood samples to be obtained from nonrestrained and unanesthetized mice. The collection end of the catheter is located outside the cage allowing the mouse to remain completely undisturbed prior to and during blood collection. The apparatus was used in adult mice surgically fitted under pentobarbital anesthesia with right atrial silastic catheters. Sample volume and collection frequency are easily controlled without subjecting the animal to repetitive trauma. Low plasma corticosterone concentrations confirmed the nonstressful quality of the technique. Full catheter patency in mice averaged 21.5 days. The tethering apparatus design was easily upscaled to accommodate use in adult rats.     

Catheter lock technique: in vitro efficacy of ethanol for eradication of methicillin-resistant staphylococcal biofilm compared with other agents

Biofilm formation in central venous catheters (CVC) is a prerequisite for catheter-related bloodstream infection (CRBSI). The catheter lock technique has been used to treat biofilm infection, but the ideal agent, concentration and the minimum exposure time necessary to eradicate the biofilms are not clearly known. In this study, biofilm-producing strains of staphylococci were used to find out the minimum biofilm eradication concentration of ethanol compared with three other conventional antibacterial agents. Eight representative methicillin-resistant staphylococci, from colonized CVCs, were studied. The biofilms were exposed to 1, 5 and 10?mg?mL(-1) of gentamicin, ciprofloxacin and vancomycin. The ethanol concentrations used were 20%, 40% and 80%. Biofilms were examined for the presence of live organisms after exposure to these agents from 30?min to 24?h. The three antibiotics were unable to eradicate the biofilms even after 24?h, while ethanol at 40% concentration could do so for all the isolates in 1?h. Our study highlights the efficacy and rationale of using 40% ethanol for a short period as catheter lock solution to eradicate biofilms and thus to prevent CRBSI, instead of using high concentrations of antibiotics for extended periods.     

Laser angioplasty of peripheral arteries after unsuccessful recanalization of the superficial femoral artery

AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average occlusion length of the SFA was 17.5 cm (range 4-36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). After the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA.     

Customized vascular catheters for rodents

Custom arterial and venous catheters were made for rodents from polyurethane tubing. The low thrombogenicity and toxicity index, chemical stability and resiliency of polyurethane made this tubing an ideal catheter material. The tubing is shaped using peanut oil heated to 160 degrees C. Sealing these catheters is accomplished simply by heating the tube end with a hot object and pinching it between the fingers. Chronic catheter patency was maintained using Burr's solution (9:1 mixture of glycerine and heparin). No flushing was necessary.     

Simultaneous sampling of portal, hepatic and systemic blood during intragastric loading and tracer infusion in conscious pigs

A surgical model for catheterization at multiple sites has been developed for use in long-term metabolic studies. For blood sampling, catheters were inserted into the portal and hepatic veins and the common carotid artery. The hepatic vein catheter was inserted from the margin of a liver lobe and led through the venous system, until the tip was close to the bifurcation with the inferior vena cava. A new technique was developed to ensure correct placement of the hepatic vein catheter using the specific extraction of indocyanin-green over the liver during surgery. Gastrostomy was performed using a Pezzer catheter. Catheters in the artery and hepatic and portal veins were patent for blood withdrawal for up to 4 weeks, and thus allowed repeated metabolic studies. Studies were performed in conscious animals familiar with the experimental situation.     

Ultrasound-guided continuous femoral nerve block: a randomized trial on the influence of femoral nerve catheter orifice configuration (six-hole versus end-hole) on post-operative analgesia after total knee arthroplasty

Background

Multiorifice catheters have been shown to provide superior analgesia and significantly reduce local anesthetic consumption compared with end-hole catheters in epidural studies. This prospective, blinded, randomized study tested the hypothesis that, in continuous femoral nerve block (CFNB) under ultrasound guidance, multiorifice catheter would reduce local anesthetic consumption at 24?h compared with end-hole catheter.

Methods

Eighty adult patients (aged ≥18?years) scheduled to undergo primary total knee arthroplasty under a combination of CFNB, sciatic nerve block and general anesthesia were randomized to CFNB using either a 3-pair micro-hole (Contiplex, BRAUN®, 20G - 400?mm) or an end-hole (Silverstim VYGON®, 20G - 500?mm) catheter. Once the femoral catheter was sited, a bolus of 20?mL lidocaine 1% was injected. An electronic pump then delivered an automated 5?mL bolus of ropivacaine 0.2% hourly, with 10?mL self-administered patient controlled analgesia boluses.

Results

There was no inter-group difference in either median number of ropivacaine boluses on demand during the first 24?h (4(2–7) vs. 4(2–8) in six-hole and end-hole groups, respectively; P?=?0.832) or median ropivacaine consumption at 48?h (365(295–418) vs. 387(323–466); P?=?0.452).No significant differences were recorded between the groups at 24?h regarding median average verbal rate pain scale (2(0–3) vs. 2(0–4); P?=?0.486) or morphine consumption (0(0–20) vs. 0(0–20); P?=?0.749). Quadriceps muscle strength declined to 7% (0–20) and 10% (0–28) in the six-hole and end-hole groups, respectively, at 24?h after surgery (P?=?0.733).

Conclusions

In this superiority trial, catheter orifice configuration did not influence the effectiveness of CFNB in this setting: quality of analgesia was similar, with no reduction in either local anesthetic or morphine consumption, and equivalent postoperative quadriceps weakness.

Trial registration

Retrospectively registered at (NCT03376178). Date: 21 November 2017.

     

Prevention of catheter-related infections by a new, catheter-restricted antibiotic filling technique

Catheter-related infections pose a hazard to both humans and laboratory animals. The aim of this study was to develop a technique preventing bacterial colonization of intravascular catheters. In 27 dogs a total of 70 catheters were implanted. On an average catheters were used for 207 days. Three protocols were compared: (1) flushing the catheters with a heparinized solution; (2) filling only the catheter lumen with alpha-chymotrypsin solution (225 units/ml); (3) filling only the catheter lumen with a solution containing a mixture of the aminoglycoside antibiotic gentamicin (20 mg/ml) and chymotrypsin (225 units/ml). Catheter fillings were always withdrawn before catheter use. Catheter exit sites were all treated with povidone iodine ointment once a day. Body temperatures and weights were recorded, bacteriological and electron microscopical examinations of catheters performed. Without gentamicin filling all catheters were colonized after a few weeks. The dogs showed clinical signs of chronic bacteraemia. Gentamicin filling eradicated colonization. No further bacteraemia was observed. We conclude that filling only the catheter lumen with a concentrated solution of chymotrypsin and gentamicin, combined with measures to prevent infections via the subcutaneous catheter tunnel, is an effective and safe technique to prevent catheter-related infections.     

A surgical procedure and tethering system for chronic blood sampling, infusion, and temperature monitoring in caged nonhuman primates

A jacket and tethering system was used to maintain chronic catheters in monkeys, which provided catheter access and manipulability without further restraint. Surgical placement of catheters and a temperature probe allowed for a common cutaneous exit and interface with the jacket and tether. Monkeys were fitted in a sterile leather or denim jacket which was attached to a sterilized flexible stainless steel cable. Through this conduit, an indwelling temperature probe, as well as catheters from the internal jugular and femoral veins, were attached to a swivel unit located on the upper portion of the cage. The internal jugular catheter was used for the continuous infusion of support solution. The catheter from the femoral vein was maintained with a heparin lock and used for serial blood sampling. Using this system, it was possible to obtain frequent blood samples and body temperature readings, and to administer a continuous intravenous infusion without chemical or excessive physical restraint. To date, 367 monkeys, 322 cynomolgus (Macaca fasicularis), 16 rhesus (Macaca mulatta), and 21 African green (Cercopithecus aethiops) have been studied using this procedure.     

Catheter-tract infections in rhesus macaques (Macaca mulatta) with indwelling intravenous catheters

Development of catheter-tract infections in experimental animals can have devastating consequences on animal health and the functional lifespan of surgical implants. To measure the incidence of catheter-tract infections in animals with exteriorized intravenous catheters in this facility and assess the effects of these infections on mean catheter lifespan, health records of 31 Macaca mulatta with catheters were reviewed. Records spanned the interval of January 1, 1996 through October 1, 1997. Catheter-tract infections in 16 of 53 (30.2%) monkeys with catheters were diagnosed based on a combination of clinical signs of infection and results of bacterial culture. Segmental catheter-tract infections reduced mean catheter lifespan to 147 days, compared with 354 days for uninfected catheters. Exit-wound, local tunnel, and surgical-site infections did not significantly reduce catheter lifespan. Bacterial culture reports documented 31 isolates; 41.9% (13 of 31) were coagulase-negative staphylococci, and 22.6% (7 of 31) were Staphylococcus aureus. Of 20 isolates tested, 15 (75%) were resistant to methicillin/oxacillin in vitro. Antimicrobial susceptibility testing of methicillin-resistant and methicillin-susceptible isolates indicated that, compared with methicillin-sensitive isolates, methicillin-resistant isolates had a pattern of multiple antibiotic resistance. Catheter-tract infections were common in this colony of rhesus macaques, and clinically severe infections caused a drastic reduction in catheter lifespan. Approximately half (48%) the bacterial isolates were methicillin-resistant gram-positive bacteria.     

A methodology for numerically analysing the hepatic artery haemodynamics during B-TACE: a proof of concept

Balloon-occluded transarterial chemoembolisation (B-TACE) is an intraarterial transcatheter treatment for liver cancer. In B-TACE, an artery-occluding microballoon catheter occludes an artery and promotes collateral circulation for drug delivery to tumours. This paper presents a methodology for analysing the haemodynamics during B-TACE, by combining zero-dimensional and three-dimensional modelling tools. As a proof of concept, we apply the methodology to a patient-specific hepatic artery geometry and analyse two catheter locations. Results show that the blood flow redistribution can be predicted in this proof-of-concept study, suggesting that this approach could potentially be used to optimise catheter location.     

Xenopsylla cheopis: cellular expression of hypersensitivity in guinea pigs

Guinea pigs multiply exposed to Xenopsylla cheopis adult fleas exhibited marked blood basophil responses to challenge infestation with only minor changes in blood eosinophil levels. Dermal responses to flea feeding were marked by dominant neutrophil (52% of the infiltrate) and eosinophil (32%) accumulations 24 hr after primary feeding, with a weak basophil response (11%). However, after challenge feeding 14 days later, eosinophils dominated, representing 59% of the infiltrate with basophils comprising 30% of the cellular response; neutrophils were rare (7%). Mast cells did not exhibit any increases in density during either the primary or secondary infestation, representing 4-7% of the infiltrate. These results demonstrate that flea feeding induces systemic and local basophil responses as demonstrated for all hematophagous arthropods examined so far. Flea feeding success was not adversely affected by feeding on homologously hypersensitized guinea pigs or guinea pigs sensitized by Ornithodoros parkeri feeding. However, basophil responses at flea feeding sites in heterologous (tick) sensitized animals were more basophilic (26 +/- 4 cells/0.03-mm2 area) than feeding sites in homologous (flea) sensitized hosts (9 +/- 6 cells). Furthermore, primary tick feeding sites become erythematous and indurated after flea feeding on the opposite flank, and were marked histologically by strong basophil abscess (276 +/- 56 cells/0.03-mm2 area); primary flea feeding sites were not activated by tick challenge feeding. These cross-generic challenge feeding experiments suggest antigen cross-reactivity, resulting in activation of feeding sites of a heterologous arthropod.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of bronchovascular downstream blood pressure changes in exercising sheep

The relative roles of neural and pressure gradient factors, causing a fall or maintenance of bronchial blood flow in exercising sheep, are unknown. These were examined in sheep prepared under thiopentone/isoflurane general anaesthesia with a pulsed Doppler probe mounted on the bronchial artery, and aortic pressure (Pa) catheter in superficial cervical artery. After recovery, Swan-Ganz catheters were inserted under local anaesthesia into the pulmonary artery. Bronchial flow and conductance (Qbr, Cbr), and pressure gradients (Pg; i.e. aortic minus right atrial, Pg_RAP; pulmonary artery, Pg_Ppa; and, left atrial (wedge) Pg_LAP) were derived from continuous records, after switching between downstream sites during and after moderately severe treadmill exercise (3.8 km.h(-1), for 1.7 min, 6 min recovery). The protocol was repeated after combined alpha1,alpha2-adrenoceptor/cholinoceptor blockade using phentolamine methanesulfonate and methscopolamine bromide. Bronchial flow fell in both receptor intact (INT) and (BL) blocked state. Pa rose in INT, but downstream pressures rose only 3.7 (RAP), 2.8 (Ppa) and 2.0 (LAP) mmHg (P for each < 0.05) in both INT and BL. Pg_RAP and Pg_Ppa did not rise, but Pg_LAP rose 4.0 mmHg (P < 0.05). In BL, Pa fell, as did Pg_RAP (7.0 mmHg, P < 0.05), Pg_Ppa (8.9 mmHg, P < 0.001), but Pg_LAP did not change. Thus, downstream pressures change by small amounts, and pressure gradients to RAP and Ppa sites do not change during moderately severe exercise in normal sheep. The fall in Qbr in INT is due to neural factors, but in BL is due to a fall in Pg. The relative rise in Pg_LAP in both INT and BL favours redistribution within total Qbr to the pulmonary capillary/vein/left atrium site.     

小口径血液导流管的实验研究

目的:探讨小口径血液导流管在动物离断肢体模型中快速恢复通血的实验基础应用,研究小口径血液导流管实验幼猪离断肢体维持通血效果的评价。方法:20只实验幼猪随机分为A、B两组,制成后肢完全离断模型模型,采用内径为2.0 mm、外径2.5mm的血液导流管,A组长度10 cm;B组长度20 cm,进行血管桥接后定期观察血液导流管通畅性,观察终点为血液导流管完全堵塞,血管超声探测仪无血流信号,远端血管搏动消失,离断肢体以远皮下毛细血管网无渗血。比较两组到达观察终点的时间有无差异。结果:建立临时血管通路后,离断肢体远端股动脉的远端有搏动,血管超声探测仪可检测到血液导流管内有血流信号,随着时间的延长,血液导流管动脉段逐渐由鲜红色变为暗红色,导流管段逐渐形成附壁血栓,远端血管搏动及皮下毛细管网渗血逐渐减弱直至消失,血流信号消失,两组到达观测终点的时间分别为A组365±47.4 min;B组359±31.5 min,两者比较其差异没有统计学意义(P0.05)。说明长度在10 cm-20 cm的小口径血液导流管在实验动物离断肢体血管通血方面无明显差异。结论:小口径血液导流管能够用于动物离断肢体的血管临时桥接,维持通血时间可达6-8小时,有效通血时间长。实验数据说明小口径血液导流管适合于动物离断肢体模型中的血管桥接,在下一步临床应用中在四肢复杂血管损伤中有着较为广阔的临床应用前景。