Attitudes of Dutch intensive care unit clinicians towards oxygen therapy.

BACKGROUND: Over the last decade, there has been an increasing awareness for the potential harm of the administration of too much oxygen. We aimed to describe self-reported attitudes towards oxygen therapy by clinicians from a large representative sample of intensive care units (ICUs) in the Netherlands. METHODS: In April 2019, 36 ICUs in the Netherlands were approached and asked to send out a questionnaire (59 questions) to their nursing and medical staff (ICU clinicians) eliciting self-reported behaviour and attitudes towards oxygen therapy in general and in specific ICU case scenarios. RESULTS: In total, 1361 ICU clinicians (71% nurses, 24% physicians) from 28 ICUs returned the questionnaire. Of responding ICU clinicians, 64% considered oxygen-induced lung injury to be a major concern. The majority of respondents considered a partial pressure of oxygen (PaO2) of 6-10 kPa (45-75 mmHg) and an arterial saturation (SaO2) of 85-90% as acceptable for 15 minutes, and a PaO2 7-10 kPa (53-75 mmHg) and SaO2 90-95% as acceptable for 24-48 hours in an acute respiratory distress syndrome (ARDS) patient. In most case scenarios, respondents reported not to change the fraction of inspired oxygen (FiO2) if SaO2 was 90-95% or PaO2 was 12 kPa (90 mmHg). CONCLUSION: A representative sample of ICU clinicians from the Netherlands were concerned about oxygen-induced lung injury, and reported that they preferred PaO2 and SaO2 targets in the lower physiological range and would adjust ventilation settings accordingly.

Influenza virus and factors that are associated with ICU admission, pulmonary co-infections and ICU mortality.

PURPOSE: While most influenza patients have a self-limited respiratory illness, 5-10% of hospitalized patients develop severe disease requiring ICU admission. The aim of this study was to identify influenza-specific factors associated with ICU admission and mortality. Furthermore, influenza-specific pulmonary bacterial, fungal and viral co-infections were investigated. METHODS: 199 influenza patients, admitted to two academic hospitals in the Netherlands between 01-10-2015 and 01-04-2016 were investigated of which 45/199 were admitted to the ICU. RESULTS: A history of Obstructive/Central Sleep Apnea Syndrome, myocardial infarction, dyspnea, influenza type A, BMI > 30, the development of renal failure and bacterial and fungal co-infections, were observed more frequently in patients who were admitted to the ICU, compared with patients at the normal ward. Co-infections were evident in 55.6% of ICU-admitted patients, compared with 20.1% of patients at the normal ward, mainly caused by Staphylococcus aureus, Streptococcus pneumoniae, and Aspergillus fumigatus. Non-survivors suffered from diabetes mellitus and (pre-existent) renal failure more often. CONCLUSIONS: The current study indicates that a history of OSAS/CSAS, myocardial infarction and BMI > 30 might be related to ICU admission in influenza patients. Second, ICU patients develop more pulmonary co-infections. Last, (pre-existent) renal failure and diabetes mellitus are more often observed in non-survivors.

Clinical course and complications following diagnostic bronchoalveolar lavage in critically ill mechanically ventilated patients.

BACKGROUND: Flexible, fibreoptic bronchoscopy (FFB) and bronchoalveolar lavage (BAL) have been used for diagnostic purposes in critically ill ventilated patients. The additional diagnostic value compared to tracheal aspirations in ventilator-associated pneumonia (VAP) has been questioned. Nevertheless, BAL can provide extra information for the differential diagnosis of respiratory disease and good antibiotic stewardship. These benefits should outweigh potential hazards caused by the invasiveness of this diagnostic technique. The focus of the present study was on the clinical course and complications of patients following BAL procedures up to 24 h. METHODS: Hundred sixty-four FFB guided BAL procedures for suspected pneumonia were analysed in an observational study. The clinical course of patients was monitored by respiratory and haemodynamic data before BAL, 1 and 24 h after BAL. Complications were defined and registered. Factors associated with complications were analysed by logistic regression. CLINICAL COURSE: a decrease in average pO2/FiO2 ratio 1 h after BAL from 29 kPa (218 mmHg) to 25 kPa (189 mmHg) (p < 0.05) was observed which fully recovered within 24 h. Respiratory complications: the incidence of procedure related hypo-oxygenation (SaO2 ≤ 88 %) and/or bronchospasm was 9 %; a decrease of >25 % PaO2/FiO2 ratio 1 h after BAL was found in 29 % of patients; no bleeding or pneumothorax were registered. Haemodynamic complications: there were no cases of hypertension and cardiac rhythm disturbances; haemodynamic instability within the first 24 h after BAL was recorded in 22 %; this was correlated with a cardiovascular diagnosis at admission (OR 2.9; 95 % CI 1.2 - 6.7) and the presence of cardiovascular co-morbidity (OR 3.5; 95 % CI 1.5 - 8.3). The incidence of bacteraemia was 7 %. There was no case of procedure related death. DISCUSSION: Frequently occurring haemodynamic and respiratory instability but no cases of cardiac rhythm disturbances, bleeding, pneumothorax or procedure related death were attributable to diagnostic FFB and BAL. The procedures should be conducted under careful supervision by experienced physicians. Only a randomized controlled trial that compares diagnostic FFB and BAL with a non-invasive strategy could ultimately establish the safety profile and clinical utility of these procedures in critically ill ventilated patients.

Electronic nose analysis of exhaled breath to diagnose ventilator-associated pneumonia.

BACKGROUND: Exhaled breath analysis is an emerging technology in respiratory disease and infection. Electronic nose devices (e-nose) are small and portable with a potential for point of care application. Ventilator-associated pneumonia (VAP) is a common nosocomial infection occurring in the intensive care unit (ICU). The current best diagnostic approach is based on clinical criteria combined with bronchoalveolar lavage (BAL) and subsequent bacterial culture analysis. BAL is invasive, laborious and time consuming. Exhaled breath analysis by e-nose is non-invasive, easy to perform and could reduce diagnostic time. Aim of this study was to explore whether an e-nose can be used as a non-invasive in vivo diagnostic tool for VAP. METHODS: Seventy-two patients met the clinical diagnostic criteria of VAP and underwent BAL. In thirty-three patients BAL analysis confirmed the diagnosis of VAP [BAL+(VAP+)], in thirty-nine patients the diagnosis was rejected [BAL-]. Before BAL was performed, exhaled breath was sampled from the expiratory limb of the ventilator into sterile Tedlar bags and subsequently analysed by an e-nose with metal oxide sensors (DiagNose, C-it, Zutphen, The Netherlands). From further fifty-three patients without clinical suspicion of VAP or signs of respiratory disease exhaled breath was collected to serve as a control group [control(VAP-]). The e-nose data from exhaled breath were analysed using logistic regression. RESULTS: The ROC curve comparing [BAL+(VAP+)] and [control(VAP-)] patients had an area under the curve (AUC) of 0.82 (95% CI 0.73-0.9). The sensitivity was 88% with a specificity of 66%. The comparison of [BAL+(VAP+)] and [BAL-] patients revealed an AUC of 0.69; 95% CI 0.57-0.81) with a sensitivity of 76% with a specificity of 56%. CONCLUSION: E-nose lacked sensitivity and specificity in the diagnosis of VAP in the present study for current clinical application. Further investigation into this field is warranted to explore the diagnostic possibilities of this promising new technique.

Mimivirus is not a frequent cause of ventilator-associated pneumonia in critically ill patients.

Acanthamoeba polyphaga mimivirus (APMV) belongs to the amoebae-associated microorganisms. Antibodies to APMV have been found in patients with pneumonia suggesting a potential role as a respiratory pathogen. In addition, positive serology for APMV was associated with an increased duration of mechanical ventilation and intensive care unit stay in patients with ventilator-associated pneumonia. The aim of the present study was to assess the presence of APMV in bronchoalveolar lavage fluid samples of critically ill patients suspected of ventilator-associated pneumonia. The study was conducted in the intensive care unit of the Maastricht University Medical Centre. All consecutive bronchoalveolar lavage fluid samples obtained between January 2005 and October 2009 from patients suspected of ventilator-associated pneumonia were eligible for inclusion. All samples were analyzed by real-time PCR targeting the APMV. A total of 260 bronchoalveolar lavage fluid samples from 214 patients (139 male, 75 female) were included. Bacterial ventilator-associated pneumonia was confirmed microbiologically in 105 out of 260 (40%) suspected episodes of ventilator-associated pneumonia (86 patients). The presence of APMV DNA could not be demonstrated in the bacterial ventilator-associated pneumonia positive or in the bacterial ventilator-associated pneumonia negative bronchoalveolar lavage fluid samples. Although suspected, APMV appeared not to be present in critically ill patients suspected of ventilator-associated pneumonia, and APMV does not seem to be a frequent cause of ventilator-associated pneumonia.

Concurrent Whipple's disease and Giardia lamblia infection in a patient presenting with weight loss.

Whipple's disease is an uncommon systemic disease caused by the recently cultured Tropheryma whippelii, classically presenting with gastrointestinal symptoms. We report a patient with weight loss and malabsorption in which Whipple's disease and concurrent Giardia lamblia infection were diagnosed. Moreover, multiple small bowel polyps were present. The relationship between concurrent Whipple's disease and Giardia lamblia infection is discussed.

Prevention of ventilator-associated pneumonia by oral decontamination: a prospective, randomized, double-blind, placebo-controlled study.

UNLABELLED: Colonization of the intestinal tract has been assumed to be important in the pathogenesis of ventilator-associated pneumonia (VAP), but relative impacts of oropharyngeal, gastric, or intestinal colonization have not been elucidated. Our aim was to prevent VAP by modulation of oropharyngeal colonization, without influencing gastric and intestinal colonization and without systemic prophylaxis. In a prospective, randomized, placebo-controlled, double-blind study, 87 patients received topical antimicrobial prophylaxis (gentamicin/ colistin/vancomycin 2% in Orabase, every 6 h) in the oropharynx and 139 patients, divided over two control groups, received placebo (78 patients were studied in the presence of patients receiving topical prophylaxis [control group A] and 61 patients were studied in an intensive care unit where no topical prophylaxis was used [control group B]). Baseline characteristics were comparable in all three groups. Topical prophylaxis eradicated colonization present on admission in oropharynx (75% in study group versus 0% in control group A [p < 0.00001] and 9% in control group B patients [p < 0.00001]) and in trachea (52% versus 22% in A [p = 0.03] and 7% in B [p = 0.004]). Moreover, topical prophylaxis prevented acquired oropharyngeal colonization (10% versus 59% in A [p < 0.00001] and 63% in B [p < 0.00001]). Colonization rates in stomach and intestine were not affected. Incidences of VAP were 10% in study patients, 31% in Group A, and 23% in Group B patients (p = 0.001 and p = 0.04, respectively). This was not associated with shorter durations of ventilation or ICU stay or better survival. Oropharyngeal colonization is of paramount importance in the pathogenesis of VAP, and a targeted approach to prevent colonization at this site is a very effective method of infection prevention. KEYWORDS: cross infection, prevention and control; respiration, artificial, adverse effects; antibiotics, administration and dosage infection control methods; pneumonia, etiology, prevention and control; intubation, intratracheal, adverse effects

Characteristics of polyclonal endemicity of Pseudomonas aeruginosa colonization in intensive care units. Implications for infection control.

We investigated the endemicity of Pseudomonas aeruginosa in intensive care units (ICUs) through analyses of surveillance cultures (from the rectum, stomach, oropharynx, and trachea; n = 1,089), and clinical cultures (n = 2,393) from 297 consecutive patients. Multiple isolates of P. aeruginosa (n = 353) were genotyped. Variables associated with acquisition of respiratory tract colonization (RTC) were tested in a risk factor analysis. The mean daily prevalence of colonization was 34%. On admission, 22 patients had intestinal colonization and 13 had RTC. Twenty patients acquired colonization in the intestinal and 24 in the respiratory tract. Forty-four different genotypes were found; 38 (86%) were isolated from individual patients only. In all, 37 patients had RTC with a total of 38 genotypes: 13 (34%) were colonized on admission, 9 (24%) acquired RTC with a novel genotype during a stay in the ICU, five (13%) acquired colonization from their intestinal tract and three (8%) were colonized via cross-acquisition. In eight patients (21%), no route could be demonstrated for colonization. Antibiotics providing P. aeruginosa with a selective growth advantage were associated with acquired RTC. Endemicity of colonization with P. aeruginosa is characterized by polyclonality, and seems to be maintained by continuous admittance of colonized patients and selection pressure from antibiotics rather than by cross-acquisition.

[Ventilator-associated pneumonia; controversies with respect to diagnosis, pathogenesis, therapy and prevention]. / Beademingspneumonie; controversen over diagnostiek, pathogenese, therapie en preventie.

Ventilator-associated pneumonia (VAP) is the most frequent nosocomial infection among intensive care patients; it is associated with increased morbidity and mortality. VAP is always preceded by colonization of the upper respiratory tract with potentially pathogenic micro-organisms. Oropharyngeal colonization is pivotal in the pathogenesis of VAP, while gastric and intestinal colonization appear to be less important than generally believed. The diagnosis is difficult and usually relies on a combination of clinical, microbiological and radiographic criteria. This combination of criteria may have a high sensitivity for VAP, but specificity is low. As a result, many patients receive antibiotics unnecessarily. Bronchoscopic sampling of lower airways can increase specificity, but whether these relatively expensive techniques are cost-effective remains to be established. The best antibiotic therapy for VAP is unknown. General infection control measures remain the cornerstone of infection prevention in each intensive care unit (ICU). Selective digestive decontamination (SDD) was associated with a reduction in the incidence of VAP, but mortality rates remained largely unaffected, and selection of antibiotic-resistant pathogens remains a potential disadvantage. Routine SDD in ICU is discouraged. Decontamination of the oropharynx appears to be equally effective.

Ventilator-associated pneumonia: risk factors and patient mortality.

Among critically ill and mechanically ventilated patients, ventilator-associated pneumonia (VAP) is the most common nosocomial infection. Although VAP has a high mortality rate, it is unknown whether patients die from VAP or underlying illness. This article reviews the association between VAP and mortality, and discusses whether prevention of VAP will improve the outcome of mechanically ventilated patients.

Colonization with Pseudomonas aeruginosa in patients developing ventilator-associated pneumonia.

To determine routes of colonization and genotypic variation of Pseudomonas aeruginosa leading to ventilator-associated pneumonia, colonization of the rectum, stomach, oropharynx, and trachea was studied chronologically in 10 patients. Ninety-one isolates of P aeruginosa were genotyped; seven different genotypes were identified. Patients developing ventilator-associated pneumonia caused by P aeruginosa were colonized at multiple body sites and may be colonized with multiple genotypes. The upper respiratory tract is the predominant initial site of colonization with P aeruginosa.

Cross-colonisation with Pseudomonas aeruginosa of patients in an intensive care unit.

BACKGROUND: Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is usually preceded by colonisation of the respiratory tract. During outbreaks, colonisation with P aeruginosa is mainly derived from exogenous sources. The relative importance of different pathways of colonisation of P aeruginosa has rarely been determined in non-epidemic settings. METHODS: In order to determine the importance of exogenous colonisation, all isolates of P aeruginosa obtained by surveillance and clinical cultures from two identical intensive care units (ICUs) were genotyped with pulsed field gel electrophoresis. RESULTS: A total of 100 patients were studied, 44 in ICU 1 and 56 in ICU 2. Twenty three patients were colonised with P aeruginosa, seven at the start of the study or on admission and 16 of the remaining 93 patients became colonised during the study. Eight patients developed VAP due to P aeruginosa. The incidence of respiratory tract colonisation and VAP with P aeruginosa in our ICU was similar to that before and after the study period, and therefore represents an endemic situation. Genotyping of 118 isolates yielded 11 strain types: eight in one patient each, two in three patients each, and one type in eight patients. Based on chronological evaluation and genotypical identity of isolates, eight cases of cross-colonisation were identified. Eight (50%) of 16 episodes of acquired colonisation and two (25%) of eight cases of VAP due to P aeruginosa seemed to be the result of cross-colonisation. CONCLUSIONS: Even in non-epidemic settings cross-colonisation seems to play an important part in the epidemiology of colonisation and infection with P aeruginosa.

Implementation of bronchoscopic techniques in the diagnosis of ventilator-associated pneumonia to reduce antibiotic use.

In intensive care units, a large proportion of antibiotics are prescribed for presumed episodes of ventilator-associated pneumonia (VAP). VAP is usually diagnosed on a combination of clinical, radiographic, and microbiologic criteria with a high sensitivity but low specificity for VAP. As a result, patients may receive antibiotics unnecessarily. Specificity can be increased by the addition of quantitative cultures of samples of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) to the diagnostic criteria. We prospectively analyzed the effects of implementation of PSB and BAL in the diagnosis of VAP on antibiotic prescription. PSB and/or BAL were performed in patients who fulfilled the clinical, radiographic, and microbiologic criteria for VAP. Based on quantitative cultures of PSB and/or BAL, patients were categorized into three groups: VAP microbiologically proven (Group 1; n = 72); clinical suspicion of VAP not confirmed microbiologically (Group 2; n = 66); and patients in whom bronchoscopy could not be performed (Group 3; n = 17). In Group 1, antibiotic therapy was instituted empirically in 40 patients (56%) (Group 1a) and after obtaining culture results in the other 32 patients (Group lb). Adjustment of therapy, based on culture results, occurred in 14 (35%) patients in Group la. In Group 2 empiric therapy was instituted in 34 (52%) patients (Group 2a) and dIscontinued within 48 h in 17 of them (50%). In Group 3, 17 (100%) patients were treated with antibiotics. Among the 66 patients in whom a clinical suspicion of VAP was not confirmed, only 18 (27%) were treated with antibiotics, and antibiotic therapy was withheld in 48 (35%) of 138 patients who underwent bronchoscopy. Withholding of antibiotic therapy had no negative effect on the recurrence of a clinical suspicion of VAP or on mortality rates. We conclude that addition of bronchoscopic techniques to the criteria for VAP may help to reduce antibiotic use. However, the definite benefits and cost-effectiveness of these techniques should be analyzed in a randomized study.

Indications for antibiotic use in ICU patients: a one-year prospective surveillance.

The high prevalence of nosocomial infections in critically ill ICU patients is associated with high antibiotic consumption. Besides its economic impact, there is the constant threat of selection and induction of antibiotic resistance. Surveillance studies recording the incidence of infections, antibiotic use, and antimicrobial susceptibilities of pathogens supply vital information regarding infection control and prevention of antibiotic resistance. In order to analyse antibiotic consumption we recorded antibiotic use in a general ICU during one year by categorizing the indications for antibiotic use into three groups; (i) prophylaxis; (ii) therapy for a bacteriologically proven infection (BPI); (iii) therapy for a non-bacteriologically proven infection (non-BPI). Bronchoscopic techniques were used to diagnose pneumonia. In practice, BPI must be treated, but a proportion of antibiotics prescribed for non-BPI may be unnecessary. The subdivision in BPI and non-BPI may help to identify these cases. In all, 515 patients were admitted to ICU and 36% of these had at least one infection. Of all infections, 53% were ICU-acquired and 99% of these occurred in intubated patients. Antibiotics were prescribed in 61% of admissions. Of all antibiotics prescribed for therapy, 49% were for respiratory tract infections, 19% for abdominal infections and 13% for sepsis eci. Categorized by indication, 59% of all antibiotic prescriptions were for BPI, 28% for non-BPI and 13% for prophylaxis. A theoretical reduction of 25% in the number of non-BPI prescriptions would result only in a 7% decrease of total antibiotic use. We conclude that almost all antibiotics prescribed were for intubated patients and for BPI. Respiratory infections were the single most common infection and accounted for 49% of all antibiotics used. Therefore, in our setting, prevention of respiratory tract infections is probably the most effective mode to reduce antibiotic use.

Reproducibility of quantitative cultures of endotracheal aspirates from mechanically ventilated patients.

Ventilator-associated pneumonia is frequently diagnosed with quantitative cultures of samples obtained by bronchoscopic techniques, a method associated with high costs and potential adverse effects. Quantitative cultures of endotracheal aspirates are easier and cheaper to obtain, and good correlations between the results of this method and those of bronchoscopic methods have been reported. However, the reproducibility of quantitative cultures of endotracheal aspirates has never been determined. We studied the quantitative analysis of endotracheal aspirates from 21 mechanically ventilated patients taken during two study days with 2- and 6-h intervals between samplings. In all, 40 endotracheal aspirates were obtained. For mechanically ventilated patients, the median variation of quantitative culture results was 12.3% (range, 0 to 63%), corresponding to 0.7 log CFU/ml. Furthermore, variation was independent of the interval of time between samplings. Persistence of significant numbers of pathogens in quantitative cultures (> or = 10(5) CFU/ml) of the consecutive endotracheal aspirates occurred in 82% of samples. We conclude that results of quantitative cultures from endotracheal aspirates are reproducible and may be useful in diagnosing ventilator-associated pneumonia.

Risk factors for pneumonia, and colonization of respiratory tract and stomach in mechanically ventilated ICU patients.

Risk factors for the development of ventilator-associated pneumonia (VAP) and colonization of the respiratory tract and stomach with enteric gram-negative bacteria (EGB) and Pseudomonadaceae were determined in 141 ventilated patients using univariate analysis and the Cox proportional hazards model. VAP was caused by EGB in 14 patients (10%), and by Pseudomonadaceae in 19 patients (13%). The duration of ventilation was a significant risk factor for VAP caused by EGB and Pseudomonadaceae, and for acquired colonization in oropharynx, stomach, and trachea with these species. Of 20 other variables, oropharyngeal colonization with EGB on admission (hazard ratio [HR] = 4.5) and an infection on admission (HR = 2.7) were selected as risk factors for VAP caused by EGB. Acquired colonization with Pseudomonadaceae in oropharynx (HR = 5.0) was the most important risk factor for VAP caused by these species. Gastric colonization with EGB or Pseudomonadaceae were no risk factors for VAP. For acquired oropharyngeal colonization with EGB only the duration of ventilation was a risk factor, whereas preceding colonization of the trachea with Pseudomonodaceae and duration of ventilation were risk factors for acquired oropharyngeal colonization with these species. In the Cox model, only the duration of ventilation was significantly related to acquired gastric colonization with EGB. Preceding colonization of the orophayrnx and of the trachea with Pseudomonadaceae were risk factors for acquired colonization with these species in the stomach. Twelve patients with VAP (46%) and 38 without VAP (33%) died (p = 0.21). In conclusion, duration of ventilation and colonization of the upper respiratory tract are the most important risk factors for VAP caused by EGB or Pseudomonadaceae.

Prosthetic arteriovenous fistulas and venous anastomotic stenosis: influence of a high flow velocity on the development of intimal hyperplasia.

Stenotic intimal thickening at the venous end of prosthetic arteriovenous (AV) fistulas for hemodialysis has been associated with perianastomotic mismatch in elastic properties between prosthesis and vein and high flow velocities. In a prospective study, we investigated the role of flow velocity on the occurrence of intimal hyperplasia in prosthetic AV fistulas in hemodialysis patients. In 24 patients, the flow velocities were assessed in the distal graft and the outflow vein postoperatively, with the use of vessel wall Doppler tracking, a noninvasive ultrasound technique. The initial velocity in the venous anastomoses was correlated with the occurrence of stenoses during follow-up (2 years). The detection of a stenosis was performed with both Duplex ultrasound and angiography. In 4 cases a stenosis developed in the venous anastomosis, in 8 cases in the venous outflow segment, and in 4 cases at both sites. Higher flow velocities around the venous anastomosis was observed in fistulas developing a stenosis at this site as compared with the nonstenotic fistulas (p < 0.05). The occurrence of stenoses in prosthetic AV fistulas in or adjacent to the venous anastomosis is not associated with a mismatch in elastic properties, but with high flow velocity.

Anastomotic intimal hyperplasia in prosthetic arteriovenous fistulas for hemodialysis is associated with initial high flow velocity and not with mismatch in elastic properties.

Stenotic intimal thickening at the venous end of prosthetic arteriovenous (AV) fistulas for hemodialysis has been associated with perianastomotic mismatch in elastic properties, and low shear rates. In a prospective way, the role of these factors on the occurrence of intimal hyperplasia in prosthetic AV fistulas in hemodialysis patients was investigated. In 24 hemodialysis patients, the elastic properties were assessed in the distal graft segment and the outflow vein postoperatively with the use of Vessel Wall Doppler Tracking (VWDT), a noninvasive ultrasound technique. In addition, normalized peak systolic velocity (nPSV) was calculated from diameter (VWDT) and peak systolic velocity. The initial mismatch around the venous anastomoses and local nPSV were correlated with the occurrence of stenoses during follow-up (2 yr). The detection of a stenosis was performed with both Duplex ultrasound and angiography. In four cases, a stenosis developed in the venous anastomosis; in eight cases, a stenosis developed in the venous outflow segment; and in four cases, stenoses developed at both sites. A better initial match in elastic properties around the venous anastomosis was observed in the fistulas developing a stenosis at this site as compared with the nonstenotic fistulas (P < 0.05). The initial local nPSV values at the site of the later stenosis were higher in the fistulas developing a stenosis as compared with the nonstenotic fistulas (P < 0.05). It was concluded that the occurrence of stenoses in prosthetic AV fistulas for hemodialysis in or adjacent to the venous anastomoses is associated with a high initial flow velocity but not with a mismatch in elastic properties.

Assessment of inhomogeneities in elastic properties of in situ and reversed saphenous vein grafts in humans.

The elastic properties of newly implanted in situ (IS, n = 11) and reversed (RV, n = 21) saphenous grafts were studied with the use of Vessel Wall Doppler Tracking. From diameter, diameter change and simultaneously recorded pulse pressure, distensibility coefficient (DC) representing the intrinsic elastic properties and compliance coefficient (CC), a parameter of haemodynamic capacity, were calculated. In order to obtain a mechanical profile, the parameters were assessed at defined sites down the graft and native arterial system. In the RV group the reversal of the grafts resulted in a difference in diameter around the proximal anastomoses (7.4 vs. 4.3 mm, p < 0.01) and from proximal to distal (4.3 vs. 5.9 mm, p < 0.01) in the grafts; around the distal anastomoses no differences in diameter were observed. Due to the natural taper of the in situ grafts, diameter decreased from proximal to distal in the grafts (4.5 vs. 3.2 mm, p < 0.05) and no size differences were found around the anastomoses. In the RV group a decrease in DC was observed from proximal to distal in the grafts; whereas in the IS group no change in DC was found from proximal to distal in the grafts but a decrease in DC was observed around the distal anastomoses. In the RV group, a decrease in CC at the proximal anastomoses was observed (0.25 vs. 0.09 mm2/kPa, p < 0.01). In the IS group no change in CC was observed around the proximal anastomoses and distal anastomoses.(ABSTRACT TRUNCATED AT 250 WORDS)