Biofilms: survival mechanisms of clinically relevant microorganisms

Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation.

Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description

BACKGROUND

The design of a percutaneous implantable prosthetic heart valve has become an important area for investigation. A percutaneously implanted heart valve (PHV) composed of 3 bovine pericardial leaflets mounted within a balloon-expandable stent was developed. After ex vivo testing and animal implantation studies, the first human implantation was performed in a 57-year-old man with calcific aortic stenosis, cardiogenic shock, subacute leg ischemia, and other associated noncardiac diseases. Valve replacement had been declined for this patient, and balloon valvuloplasty had been performed with nonsustained results.

METHODS AND RESULTS

With the use of an antegrade transseptal approach, the PHV was successfully implanted within the diseased native aortic valve, with accurate and stable PHV positioning, no impairment of the coronary artery blood flow or of the mitral valve function, and a mild paravalvular aortic regurgitation. Immediately and at 48 hours after implantation, valve function was excellent, resulting in marked hemodynamic improvement. Over a follow-up period of 4 months, the valvular function remained satisfactory as assessed by sequential transesophageal echocardiography, and there was no recurrence of heart failure. However, severe noncardiac complications occurred, including a progressive worsening of the leg ischemia, leading to leg amputation with lack of healing, infection, and death 17 weeks after PHV implantation.

CONCLUSIONS

Nonsurgical implantation of a prosthetic heart valve can be successfully achieved with immediate and midterm hemodynamic and clinical improvement. After further device modifications, additional durability tests, and confirmatory clinical implantations, PHV might become an important therapeutic alternative for the treatment of selected patients with nonsurgical aortic stenosis.

A semiquantitative culture method for identifying intravenous-catheter-related infection

We evaluated a semiquantitative culture technic for identifying infection due to intravenous catheters: rolling the catheter segment across blood agar. This method was compared to broth culture. Of 250 catheters studied, 225 (90%) had low-density colonization on semiquantitative culture (less than 15 colonies on the plate) although 49 (19.6%) of these grew some organisms in broth or on the plate. None of these catheters led to septicemia. Twenty-five catheters (10%) grew greater than or equal to 15 colonies by the semiquantitative technic; most gave confluent growth. Septicemia originated from four of these catheters (P = 0.008). Of 37 catheters exposed to bacteremias from distant foci of infection, four yielded matching growth in broth, whereas none were concordant with the blood isolate on semiquantitative culture. Local inflammation was associated with high-density colonization semiquantitative culture (P less than 0.001). The semiquantitative technic distinguishes infection (greater than or equal to 15 colonies) from contamination and is more specific in diagnosis of catheter-related septicemia than culture of the catheter in broth.

Adherence of coagulase-negative staphylococci to plastic tissue culture plates: a quantitative model for the adherence of staphylococci to medical devices

The adherence of coagulase-negative staphylococci to smooth surfaces was assayed by measuring the optical densities of stained bacterial films adherent to the floors of plastic tissue culture plates. The optical densities correlated with the weight of the adherent bacterial film (r = 0.906; P less than 0.01). The measurements also agreed with visual assessments of bacterial adherence to culture tubes, microtiter plates, and tissue culture plates. Selected clinical strains were passed through a mouse model for foreign body infections and a rat model for catheter-induced endocarditis. The adherence measurements of animal passed strains remained the same as those of the laboratory-maintained parent strain. Spectrophotometric classification of coagulase-negative staphylococci into nonadherent and adherent categories according to these measurements had a sensitivity, specificity, and accuracy of 90.6, 80.8, and 88.4%, respectively. We examined a previously described collection of 127 strains of coagulase-negative staphylococci isolated from an outbreak of intravascular catheter-associated sepsis; strains associated with sepsis were more adherent than blood culture contaminants and cutaneous strains (P less than 0.001). We also examined a collection of 84 strains isolated from pediatric patients with cerebrospinal fluid (CSF) shunts; once again, pathogenic strains were more adherent than were CSF contaminants (P less than 0.01). Finally, we measured the adherence of seven endocarditis strains. As opposed to strains associated with intravascular catheters and CSF shunts, endocarditis strains were less adherent than were saprophytic strains of coagulase-negative staphylococci. The optical densities of bacterial films adherent to plastic tissue culture plates serve as a quantitative model for the study of the adherence of coagulase-negative staphylococci to medical devices, a process which may be important in the pathogenesis of foreign body infections.

The risk of bloodstream infection in adults with different intravascular devices: a systematic review of 200 published prospective studies

OBJECTIVE

To better understand the absolute and relative risks of bloodstream Infection (BSI) associated with the various types of intravascular devices (IVDs), we analyzed 200 published studies of adults In which every device in the study population was prospectively evaluated for evidence of associated infection and microbiologically based criteria were used to define IVD-related BSI.

METHODS

English-language reports of prospective studies of adults published between January 1, 1966, and July 1, 2005, were identified by MEDLINE search using the following general search strategy: bacteremla [Medical Subject Heading, MeSH] OR septicemia [MeSH] OR bloodstream Infection AND the specific type of intravascular device (e.g., central venous port). Mean rates of IVD-related BSI were calculated from pooled data for each type of device and expressed as BSIs per 100 IVDs (%) and per 1000 IVD days.

RESULTS

Point incidence rates of IVD-related BSI were lowest with peripheral Intravenous catheters (0.1%, 0.5 per 1000 IVD-days) and midline catheters (0.4%, 0.2 per 1000 catheter-days). Far higher rates were seen with short-term noncuffed and nonmedicated central venous catheters (CVCs) (4.4%, 2.7 per 1000 catheter-days). Arterial catheters used for hemodynamic monitoring (0.8%, 1.7 per 1000 catheter-days) and peripherally inserted central catheters used in hospitalized patients (2.4%, 2.1 per 1000 catheter-days) posed risks approaching those seen with short-term conventional CVCs used in the Intensive care unit. Surgically implanted long-term central venous devices--cuffed and tunneled catheters (22.5%, 1.6 per 1000 IVD-days) and central venous ports (3.6%, 0.1 per 1000 IVD-days)--appear to have high rates of Infection when risk Is expressed as BSIs per 100 IVDs but actually pose much lower risk when rates are expressed per 1000 IVD-days. The use of cuffed and tunneled dual lumen CVCs rather than noncuffed, nontunneled catheters for temporary hemodlalysis and novel preventive technologies, such as CVCs with anti-infective surfaces, was associated with considerably lower rates of catheter-related BSI.

CONCLUSIONS

Expressing risk of IVD-related BSI per 1000 IVD-days rather than BSIs per 100 IVDs allows for more meaningful estimates of risk. These data, based on prospective studies In which every IVD in the study cohort was analyzed for evidence of infection by microbiologically based criteria, show that all types of IVDs pose a risk of IVD-related BSI and can be used for benchmarking rates of infection caused by the various types of IVDs In use at the present time. Since almost all the national effort and progress to date to reduce the risk of IVD-related Infection have focused on short-term noncuffed CVCs used in Intensive care units, Infection control programs must now strive to consistently apply essential control measures and preventive technologies with all types of IVDs.

Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria

The history, taxonomy, geographic distribution, clinical disease, and therapy of the pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria (RGM) are reviewed. Community-acquired disease and health care-associated disease are highlighted for each species. The latter grouping includes health care-associated outbreaks and pseudo-outbreaks as well as sporadic disease cases. Treatment recommendations for each species and type of disease are also described. Special emphasis is on the Mycobacterium fortuitum group, including M. fortuitum, M. peregrinum, and the unnamed third biovariant complex with its recent taxonomic changes and newly recognized species (including M. septicum, M. mageritense, and proposed species M. houstonense and M. bonickei). The clinical and taxonomic status of M. chelonae, M. abscessus, and M. mucogenicum is also detailed, along with that of the closely related new species, M. immunogenum. Additionally, newly recognized species, M. wolinskyi and M. goodii, as well as M. smegmatis sensu stricto, are included in a discussion of the M. smegmatis group. Laboratory diagnosis of RGM using phenotypic methods such as biochemical testing and high-performance liquid chromatography and molecular methods of diagnosis are also discussed. The latter includes PCR-restriction fragment length polymorphism analysis, hybridization, ribotyping, and sequence analysis. Susceptibility testing and antibiotic susceptibility patterns of the RGM are also annotated, along with the current recommendations from the National Committee for Clinical Laboratory Standards (NCCLS) for mycobacterial susceptibility testing.

Pneumatic dilation versus laparoscopic Heller's myotomy for idiopathic achalasia

BACKGROUND

Many experts consider laparoscopic Heller's myotomy (LHM) to be superior to pneumatic dilation for the treatment of achalasia, and LHM is increasingly considered to be the treatment of choice for this disorder.

METHODS

We randomly assigned patients with newly diagnosed achalasia to pneumatic dilation or LHM with Dor's fundoplication. Symptoms, including weight loss, dysphagia, retrosternal pain, and regurgitation, were assessed with the use of the Eckardt score (which ranges from 0 to 12, with higher scores indicating more pronounced symptoms). The primary outcome was therapeutic success (a drop in the Eckardt score to ≤3) at the yearly follow-up assessment. The secondary outcomes included the need for retreatment, pressure at the lower esophageal sphincter, esophageal emptying on a timed barium esophagogram, quality of life, and the rate of complications.

RESULTS

A total of 201 patients were randomly assigned to pneumatic dilation (95 patients) or LHM (106). The mean follow-up time was 43 months (95% confidence interval [CI], 40 to 47). In an intention-to-treat analysis, there was no significant difference between the two groups in the primary outcome; the rate of therapeutic success with pneumatic dilation was 90% after 1 year of follow-up and 86% after 2 years, as compared with a rate with LHM of 93% after 1 year and 90% after 2 years (P=0.46). After 2 years of follow-up, there was no significant between-group difference in the pressure at the lower esophageal sphincter (LHM, 10 mm Hg [95% CI, 8.7 to 12]; pneumatic dilation, 12 mm Hg [95% CI, 9.7 to 14]; P=0.27); esophageal emptying, as assessed by the height of barium-contrast column (LHM, 1.9 cm [95% CI, 0 to 6.8]; pneumatic dilation, 3.7 cm [95% CI, 0 to 8.8]; P=0.21); or quality of life. Similar results were obtained in the per-protocol analysis. Perforation of the esophagus occurred in 4% of the patients during pneumatic dilation, whereas mucosal tears occurred in 12% during LHM. Abnormal exposure to esophageal acid was observed in 15% and 23% of the patients in the pneumatic-dilation and LHM groups, respectively (P=0.28).

CONCLUSIONS

After 2 years of follow-up, LHM, as compared with pneumatic dilation, was not associated with superior rates of therapeutic success. (European Achalasia Trial Netherlands Trial Register number, NTR37, and Current Controlled Trials number, ISRCTN56304564.).

Differential Response of Delayed Healing and Persistent Inflammation at Sites of Overlapping Sirolimus- or Paclitaxel-Eluting Stents

Background— Although effective coverage of challenging coronary lesions has warranted the use of overlapping drug-eluting stents, the histopathological response to stent overlap is unknown.

Methods and Results— The arterial reaction to overlapping Cypher or Taxus drug-eluting stents was examined in rabbits with bare metal stents, BxVelocity or Express, serving as controls. Single iliac artery balloon injury was followed by placement of 2 overlapping 3.0-mm-diameter drug-eluting stents or bare metal stents in 60 animals (mean length of overlap, 9.8±3.6 mm). Stented arteries were harvested at 28 and 90 days for histology. Overlapped segments exhibited delayed healing compared with proximal and distal nonoverlapping sites at 28 days. Overlapped segments in Taxus stents induced significantly more luminal heterophils/eosinophils and fibrin deposition than Cypher; peristrut giant cell infiltration, however, was more frequent in the latter. Overlapping bare metal stents also showed mild delayed healing compared with nonoverlapped segments, but not to the same extent as drug-eluting stents. Although neointimal thickness within the overlap was similar in 28- and 90-day Cypher stents, there was a significant increase with Taxus ( P =0.03).

Conclusions— Compared with bare metal stents, drug-eluting stents further delay arterial healing and promote inflammation at sites of overlap. Taxus stents induced greater fibrin deposition, medial cell loss, heterophils/eosinophils, and late neointimal hyperplasia. Patients receiving overlapping drug-eluting stents need more frequent follow-up than patients with nonoverlapping stents.

Nosocomial infections in pediatric intensive care units in the United States. National Nosocomial Infections Surveillance System

OBJECTIVES

To describe the epidemiology of nosocomial infections in pediatric intensive care units (ICUs) in the United States.

BACKGROUND

Patient and ICU characteristics in pediatric ICUs suggest the pattern of nosocomial infections experienced may differ from that seen in adult ICUs.

METHODS

Data were collected between January 1992 and December 1997 from 61 pediatric ICUs in the United States using the standard surveillance protocols and nosocomial infection site definitions of the National Nosocomial Infections Surveillance System's ICU surveillance component.

RESULTS

Data on 110 709 patients with 6290 nosocomial infections were analyzed. Primary bloodstream infections (28%), pneumonia (21%), and urinary tract infections (15%) were most frequent and were almost always associated with use of an invasive device. Primary bloodstream infections and surgical site infections were reported more frequently in infants aged 2 months or less as compared with older children. Urinary tract infections were reported more frequently in children >5 years old compared with younger children. Coagulase-negative staphylococci (38%) were the most common bloodstream isolates, and aerobic Gram-negative bacilli were reported in 25% of primary bloodstream infections. Pseudomonas aeruginosa (22%) was the most common species reported from pneumonia and Escherichia coli (19%), from urinary tract infections. Enterobacter spp. were isolated with increasing frequency from pneumonia and were the most common Gram-negative isolates from bloodstream infections. Device-associated infection rates for bloodstream infections, pneumonia, and urinary tract infections did not correlate with length of stay, the number of hospital beds, or season.

CONCLUSIONS

In pediatric ICUs, bloodstream infections were the most common nosocomial infection. The distribution of infection sites and pathogens differed with age and from that reported from adult ICUs. Device-associated infection rates were the best rates currently available for comparisons between units, because they were not associated with length of stay, the number of beds in the hospital, or season.

Critical role of Bcr1-dependent adhesins in C. albicans biofilm formation in vitro and in vivo

The fungal pathogen Candida albicans is frequently associated with catheter-based infections because of its ability to form resilient biofilms. Prior studies have shown that the transcription factor Bcr1 governs biofilm formation in an in vitro catheter model. However, the mechanistic role of the Bcr1 pathway and its relationship to biofilm formation in vivo are unknown. Our studies of biofilm formation in vitro indicate that the surface protein Als3, a known adhesin, is a key target under Bcr1 control. We show that an als3/als3 mutant is biofilm-defective in vitro, and that ALS3 overexpression rescues the biofilm defect of the bcr1/bcr1 mutant. We extend these findings with an in vivo venous catheter model. The bcr1/bcr1 mutant is unable to populate the catheter surface, though its virulence suggests that it has no growth defect in vivo. ALS3 overexpression rescues the bcr1/bcr1 biofilm defect in vivo, thus arguing that Als3 is a pivotal Bcr1 target in this setting. Surprisingly, the als3/als3 mutant forms a biofilm in vivo, and we suggest that additional Bcr1 targets compensate for the Als3 defect in vivo. Indeed, overexpression of Bcr1 targets ALS1, ECE1, and HWP1 partially restores biofilm formation in a bcr1/bcr1 mutant background in vitro, though these genes are not required for biofilm formation in vitro. Our findings demonstrate that the Bcr1 pathway functions in vivo to promote biofilm formation, and that Als3-mediated adherence is a fundamental property under Bcr1 control. Known adhesins Als1 and Hwp1 also contribute to biofilm formation, as does the novel protein Ece1.

The formation of biofilms (surface-attached microbial communities) on implanted medical devices such as catheters is a major cause of fungal and bacterial infections. Prior studies of the fungal pathogen Candida albicans have shown that the regulator Bcr1 is required for biofilm formation in vitro, but the mechanism through which it promotes biofilm formation and its significance for biofilm formation in vivo was uncertain. The authors demonstrate that Bcr1 is required for biofilm formation in vivo in a rat model of catheter-based infection. Manipulation of Bcr1 target genes through mutation and gene overexpression shows that the known surface adhesin Als3 has a pivotal role in biofilm formation and that adhesins Als1 and Hwp1 also contribute to biofilm formation. The results thus indicate that adherence is the key property regulated by Bcr1 and highlight a group of adhesins as potential therapeutic targets.

Complications of angiography

This study was designed to assess the complications of angiography, including transfemoral, transaxillary, and translumbar approaches. Detailed questionnaires were completed by radiologists at 514 of the 2,066 hospitals surveyed. The radiologists reported on the complications of 118,591 examinations. The overall arteriography complication rates were: transfemoral 1.73%, translumbar 2.89%, and transaxillary 3.29%. Thirty deaths were reported, eight of which were caused by aortic dissection or aneurysm rupture. Among the three techniques, there was no difference in the incidence of cardiac complications. There were significantly more neurologic complications, including seizures, in the transaxillary group than there were in either the transfemoral or translumbar groups. Similarly, hemorrhage, arterial obstruction, and pseudoaneurysms were more common with the transaxillary technique than with either of the other approaches. Vessel perforation and extraluminal contrast material were seen most frequently with the translumbar technique. Overall, between the two selective approaches, the transfemoral route carried a significantly smaller risk of complications than the transaxillary approach. There was an inverse relationship between complication rate and the annual number of arteriograms obtained. This was most striking in hospitals without residency training programs. The complications of adrenal venography, peripheral venography, pedal lymphography, and of studies for suspected pheochromocytoma were also assessed.

Ventriculostomy-related infections. A prospective epidemiologic study

We concluded a prospective epidemiologic study of ventriculostomy-related infections (ventriculitis or meningitis) in 172 consecutive neurosurgical patients over a two-year period to determine the incidence, risk factors, and clinical characteristics of the infections. Ventriculitis or meningitis developed in 19 of 172 patients (11 per cent) undergoing a total of 213 ventriculostomies. When data from all these cases plus five cases of nonventriculostomy-related infection were combined, cerebrospinal-fluid pleocytosis was more significantly associated with the diagnosis of ventriculitis or meningitis (P less than 0.0001) than were fever and leukocytosis (P = 0.07). Risk factors for ventriculostomy-related infections included intracerebral hemorrhage with intraventricular hemorrhage (P = 0.027), neurosurgical operations (P = 0.016), intracranial pressure of 20 mm Hg or more (P = 0.019), ventricular catheterization for more than five days (P = 0.017), and irrigation of the system (P = 0.021). Previous ventriculostomy did not increase the risk of infection with subsequent procedures. We conclude that ventriculostomy-related infections may be prevented by maintenance of a closed drainage system and by early removal of the ventricular catheter. If monitoring is required for more than five days, the catheter should be removed and inserted at a different site.

Endovascular repair of abdominal aortic aneurysms and other arterial lesions

PURPOSE

This report describes our experience with endovascular stented graft repair of abdominal aortic aneurysms and other arterial lesions.

METHODS

Between September 1990 and April 1994, 57 patients were treated with endovascular stented grafts (50 with abdominal aortic aneurysms or iliac aneurysms; five with traumatic arteriovenous fistulas; one with an infected femoral false aneurysm; and one with a false aneurysm of the proximal right common carotid artery). The devices consist of either a Dacron or an autogenous vein graft sutured to a balloon-expandable stent. The stented grafts are placed through remote arteriotomies, advanced under fluoroscopic guidance to their predetermined sites, and secured into position.

RESULTS

Forty of the 50 endovascular stented graft procedures used to treat abdominal aortic aneurysms or iliac aneurysms were considered successful, even though some secondary treatment was required in six patients (two open operations; four secondary endovascular procedures). The 10 failures include four early procedural deaths, one late procedural death, and five leaks. All five arteriovenous fistulas and the two false aneurysms were successfully treated with endovascular stented grafts.

CONCLUSIONS

Although our experience with endovascular stented grafts has been promising, remaining problems require resolution, and further follow-up is needed. However, the potential advantages of these endovascular grafts warrant their continued evaluation.

Nosocomial candidemia: risk factors and attributable mortality

Over the past decade, the incidence of hospital-acquired bloodstream infections caused by Candida species has risen and the species associated with such infections have changed. The incidence of candidemia is dramatically higher in high-risk, critical-care units than in other parts of the hospital. Certain underlying physical conditions including acute leukemia, leukopenia, burns, gastrointestinal disease, and premature birth predispose patients to nosocomial candidemia. Independent risk factors include prior treatment with multiple antibiotics, prior Hickman catheterization, isolation of Candida species from sites other than the blood, and prior hemodialysis. In this article some of the challenges posed by the management of nosocomial candidemia are presented in three case studies. In addition, the results of several investigations of nosocomial candidemia at the University of Iowa Hospitals and Clinics are reviewed.

Nosocomial infection rates in adult and pediatric intensive care units in the United States. National Nosocomial Infections Surveillance System

To determine which intensive care unit (ICU) infection rate may be best for interhospital and intrahospital comparisons and to assess the influence of invasive devices and type of ICU on infection rates, we analyzed data from the National Nosocomial Infections Surveillance System. From October 1986 to December 1990, 79 hospitals reported 2,334 hospital-months of data from 196 hospital units. The median overall infection rate was 9.2 infections per 100 patients. However, this infection rate had a strong positive correlation with average length of ICU stay (r = 0.60, p less than 0.0001). When patient-days was used in the denominator, the median overall nosocomial infection rate was 23.7 infections per 1,000 patient-days. Although there was a marked reduction in the correlation with average length of stay, this rate had a strong positive correlation with device utilization (r = 0.59, p less than 0.0001). To attempt to control for average length of stay and device utilization, we examined device-associated nosocomial infection rates. Central line-associated bloodstream infection rates, catheter-associated urinary tract infection rates, and ventilator-associated pneumonia rates varied by ICU type. The distributions of device-associated infection rates were different between some ICU types and were not different between others (coronary and medical ICUs or medical-surgical and surgical ICUs). Comparison of device-associated infection rates and overall device utilization identified hospital units with outlier infection rates or device utilization. These data show that: (1) choice of denominator is critical when calculating ICU infection rates; (2) device-associated infection rates vary by ICU type; and (3) intrahospital and interhospital comparison of ICU infection rates may best be made by comparing ICU-type specific, device-associated infection rates.

Ultrasound-assisted cannulation of the internal jugular vein. A prospective comparison to the external landmark-guided technique

BACKGROUND

Central venous access is an essential part of patient management in many clinical settings and is usually achieved with a blinded, external landmark-guided technique. The purpose of this study is to evaluate whether an ultrasound technique can improve on the traditional method.

METHODS AND RESULTS

We prospectively evaluated an ultrasound-guided method in 302 patients undergoing internal jugular venous cannulation and compared the results with 302 patients in whom an external landmark-guided technique was used. Ultrasound was used exclusively in an additional 626 patients. Cannulation of the internal jugular vein was achieved in all patients (100%) using ultrasound and in 266 patients (88.1%) using the landmark-guided technique (p < 0.001). The vein was entered on the first attempt in 78% of patients using ultrasound and in 38% using the landmark technique (p < 0.001). Average access time (skin to vein) was 9.8 seconds (2-68 seconds) by the ultrasound approach and 44.5 seconds (2-1,000 seconds) by the landmark approach (p < 0.001). Using ultrasound, puncture of the carotid artery occurred in 1.7% of patients, brachial plexus irritation in 0.4%, and hematoma in 0.2%. In the external landmark group, puncture of the carotid artery occurred in 8.3% of patients (p < 0.001), brachial plexus irritation in 1.7% (p < 0.001), and hematoma in 3.3% (p < 0.001).

CONCLUSIONS

Ultrasound-guided cannulation of the internal jugular vein significantly improves success rate, decreases access time, and reduces complication rate. These results suggest that this technique may be preferred in complicated cases or when access problems are anticipated.

A controlled trial of scheduled replacement of central venous and pulmonary-artery catheters

BACKGROUND

The incidence of infection increases with the prolonged use of central vascular catheters, but it is unclear whether changing catheters every three days, as some recommend, will reduce the rate of infection, It is also unclear whether it is safer to change a catheter over a guide wire or insert it at a new site.

METHODS

We conducted a controlled trial in adult patients in intensive care units who required central venous or pulmonary-artery catheters for more than three days. Patients were assigned randomly to undergo one of four methods of catheter exchange: replacement every three days either by insertion at a new site (group 1) or by exchange over a guide wire (group 2), or replacement when clinically indicated either by insertion at a new site (group 3) or by exchange over a guide wire (group 4).

RESULTS

Of the 160 patients, 5 percent had catheter-related bloodstream infections, 16 percent had catheters that became colonized, and 9 percent had major mechanical complications. The incidence rates (per 1000 days of catheter use) of bloodstream infection were 3 in group 1, 6 in group 2, 2 in group 3, and 3 in group 4; the incidence rates of mechanical complications were 14, 4, 8, and 3, respectively. Patients randomly assigned to guide-wire-assisted exchange were more likely to have bloodstream infection after the first three days of catheterization (6 percent vs. 0, P = 0.06). Insertions at new sites were associated with more mechanical complications (5 percent vs. 1 percent, P = 0.005).

CONCLUSIONS

Routine replacement of central vascular catheters every three days does not prevent infection. Exchanging catheters with the use of a guide wire increases the risk of bloodstream infection, but replacement involving insertion of catheters at new sites increases the risk of mechanical complications.

Pathogenesis of catheter sepsis: a prospective study with quantitative and semiquantitative cultures of catheter hub and segments

Our purpose was to study prospectively the causes, routes of infection, and frequency of catheter-related sepsis in patients on total parenteral nutrition. From January 1981 to January 1984, cultures of 135 subclavian catheters from 135 adult patients were done by quantitative and semiquantitative methods. Twenty patients (14.8%) had catheter-related sepsis. Fourteen episodes (70%) stemmed from an colonized hub. Skin infection (Staphylococcus aureus, 2 cases), total parenteral nutrition mixture contamination (Enterobacter cloacae, 2 cases), and hematogenous seeding of the catheter tip (Yersinia enterocolitica, 1 case, and Streptococcus faecalis, 1 case) accounted for the remaining six septic episodes. The catheter hub is, in our experience, the most common site of origin of organisms causing catheter tip infection and bacteremia.

Upregulation of Nox-based NAD(P)H oxidases in restenosis after carotid injury

Restenosis, a frequent complication of coronary angioplasty, is associated with increased superoxide (O2*(-)) production. Although the molecular identity of the responsible oxidase is unclear, an NAD(P)H oxidase appears to be involved. In smooth muscle, p22phox and 2 homologues of gp91phox, nox1 and nox4, are expressed, whereas fibroblasts contain gp91phox. To begin investigating the possibility that these oxidase components might contribute to the increased O2*(-) that accompanies neointimal formation, we measured their expression after balloon injury of the rat carotid artery. The increase in O2*(-) production 3 to 15 days after surgery was not due to inflammatory cell infiltration but appeared to be derived from medial and neointimal smooth muscle cells and adventitial fibroblasts. Nox1 and p22phox mRNAs were increased 2.7- and 3.6-fold, respectively, at day 3 after injury and remained elevated for 15 days. gp91Phox was increased 7 to 15 days after injury, and nox4 expression was increased 2-fold, but only at day 15 after surgery. These results confirm and extend our previous in vitro data and suggest that in the vasculature, the nox-based NAD(P)H oxidases serve different functions. This dynamic regulation of oxidase components may be critical to smooth muscle phenotypic modulation in restenosis and atherosclerosis.

Biliary sphincterotomy plus dilation with a large balloon for bile duct stones that are difficult to extract

BACKGROUND

Bile duct stones are still present in 10% to 15% of patients after the application of conventional endoscopic extraction techniques and require additional procedures for duct clearance. In the vast majority of these cases, there are 2 main problems: large stone size (>15 mm) and tapering of distal bile duct.

METHODS

Fifty-eight patients in whom endoscopic sphincterotomy and standard basket/balloon extraction were unsuccessful in the removal of bile duct stones underwent dilation with a 10- to 20-mm diameter (esophageal/pyloric type) balloon at the same session. In 18 patients with tapered distal bile ducts (Group 1), 12- to 18-mm diameter balloon catheters were used to enlarge the orifice. In 40 patients with square, barrel shaped and/or large (>15mm) stones (Group 2), the sphincterotomy orifice was enlarged with 15- to 20-mm diameter balloon catheters. After dilatation, standard basket/balloon extraction techniques were used to remove the stone(s).

RESULTS

Stone clearance was successful in 16 patients (89%) in Group 1 and 35 (95%) in Group 2. Complications occurred in 9 (15.5%) patients.

CONCLUSION

Dilation with a large-diameter balloon after endoscopic sphincterotomy is a useful alternative technique in patients with bile duct stones that are difficult to remove with standard methods.

On the safety of radial artery cannulation

The frequency of complications following radial artery cannulation for monitoring purposes was determined in 1,699 cardiovascular surgical patients and in 83 patients in whom cannulation was performed in another artery after failure at the radial site. Patients were examined and radial artery flow determined by a Doppler technique 1 day and 7 days after decannulation. Although partial or complete radial artery occlusion after decannulation occurred in more than 25% of the patients, no ischemic damage to the hand or disability occurred in any patient. Neither duration of cannulation nor the size or material of the cannulas were determinants of abnormal flow. Abnormal flow was significantly related to female sex, the presence of hematoma, and to the use of extracorporeal circulation. The radial arteries of 16 patients whose results of Allen's test were abnormal were cannulated and no abnormal flow or ischemia followed. In 22 patients, the ulnar artery was cannulated after multiple punctures of the ipsilateral radial artery and no ischemia followed. We conclude that in the absence of peripheral vascular disease, the Allen's test is not a predictor of ischemia of the hand during or after radial artery cannulation, that when decreased or absent radial artery flow follows cannulation it is of no clinical consequence, and that radial artery cannulation is a low-risk high-benefit monitoring technique that deserves wide clinical use.

Quantitative culture of intravenous catheters and other intravascular inserts

Quantitative cultures were done on 149 intravenous catheters and 40 additional intravascular inserts. Intradermal and intravascular segments of the insert were cultured separately. The inserts were immersed in broth and flushed. The number of colony-forming units (cfu) per insert was estimated by surface culture of serial dilution of the broth. Nonquantitative culture of undiluted broth was also done. Since all inserts associated with bacteremia had at least 10(3) cfu, inserts greater than 10(3) cfu were considered infected. Staphylococcus epidermidis was more likely than more virulent organisms to colonize an insert without causing bacteremia. The inserts in one bacteremic patient were infected from a distant bloodstream focus; however, in the majority of patients, quantitative intradermal cultures suggested that the insertion site was the portal of entry. In bacteremic patients, either a positive quantitative or a nonquantitative culture identified an infected insert. However, only 33% of positive nonquantitative insert cultures from nonbacteremic patients were confirmed by quantitative insert culture.