Factors Affecting Perceptual Threshold in Argus II Retinal Prosthesis Subjects.

PURPOSE: The Argus II epiretinal prosthesis has been developed to provide partial restoration of vision to subjects blinded from outer retinal degenerative disease. Participants were surgically implanted with the system in the United States and Europe in a single arm, prospective, multicenter clinical trial. The purpose of this investigation was to determine which factors affect electrical thresholds in order to inform surgical placement of the device. METHODS: Electrode-retina and electrode-fovea distances were determined using SD-OCT and fundus photography, respectively. Perceptual threshold to electrical stimulation of electrodes was measured using custom developed software, in which current amplitude was varied until the threshold was found. Full field stimulus light threshold was measured using the Espion D-FST test. Relationships between electrical threshold and these three explanatory variables (electrode-retina distance, electrode-fovea distance, and monocular light threshold) were quantified using regression. RESULTS: Regression analysis showed a significant correlation between electrical threshold and electrode-retina distance (R2 = 0.50, P = 0.0002; n = 703 electrodes). 90.3% of electrodes in contact with the macula (n = 207) elicited percepts at charge densities less than 1 mC/cm2/phase. These threshold data also correlated well with ganglion cell density profile (P = 0.03). A weaker, but still significant, inverse correlation was found between light threshold and electrical threshold (R2 < 0.52, P = 0.01). Multivariate modeling indicated that electrode-retina distance and light threshold are highly predictive of electrode threshold (R2 = 0.87; P < 0.0005). CONCLUSIONS: Taken together, these results suggest that while light threshold should be used to inform patient selection, macular contact of the array is paramount. TRANSLATIONAL RELEVANCE: Reported Argus II clinical study results are in good agreement with prior in vitro and in vivo studies, and support the development of higher-density systems that employ smaller diameter electrodes. (clinicaltrials.gov identifier: NCT00407602).

Blind subjects implanted with the Argus II retinal prosthesis are able to improve performance in a spatial-motor task.

BACKGROUND/AIMS: To determine to what extent subjects implanted with the Argus II retinal prosthesis can improve performance compared with residual native vision in a spatial-motor task. METHODS: High-contrast square stimuli (5.85 cm sides) were displayed in random locations on a 19″ (48.3 cm) touch screen monitor located 12″ (30.5 cm) in front of the subject. Subjects were instructed to locate and touch the square centre with the system on and then off (40 trials each). The coordinates of the square centre and location touched were recorded. RESULTS: Ninety-six percent (26/27) of subjects showed a significant improvement in accuracy and 93% (25/27) show a significant improvement in repeatability with the system on compared with off (p<0.05, Student t test). A group of five subjects that had both accuracy and repeatability values <250 pixels (7.4 cm) with the system off (ie, using only their residual vision) was significantly more accurate and repeatable than the remainder of the cohort (p<0.01). Of this group, four subjects showed a significant improvement in both accuracy and repeatability with the system on. CONCLUSION: In a study on the largest cohort of visual prosthesis recipients to date, we found that artificial vision augments information from existing vision in a spatial-motor task. Clinical trials registry no NCT00407602.

Retinal prosthesis phosphene shape analysis.

A retinal prosthesis system to restore sight for the blind is under development. The system is analogous to cochlear implants, in which photoreceptor input is bypassed and replaced by direct electrical stimulation of the retinal ganglion cells. Currently, six test subjects have been implanted with a 4x4 electrode array and stimulator. We report here psychophysical clinical data examining how stimulation amplitude affects phosphene shape and repeatability on a single electrode. Phosphene shape data was quantified by a set of numerical descriptors calculated from image moments. Comparison of phosphene descriptors for a single electrode across repeated trials and amplitude levels measured the repeatability within an amplitude group. Our experimental findings show that stimulation of the retina creates repeatable percept shapes and that an increase in stimulation amplitude causes a significant change in size and shape of phosphenes.

Comparison of linear and torsional mode ultrasonic coagulating shears for the sealing of medium- to large-sized arteries.

BACKGROUND: Torsional mode ultrasonic coagulating shears have recently been developed for endoscopic and conventional surgery. The current investigation was conducted to compare the effectiveness of this device with the more established linear mode shears for the sealing of medium- to large-sized arteries. METHODS: Porcine carotid arteries were prepared in vitro. Each vessel was coagulated and cut by both torsional and longitudinal mode devices at different sites. The burst pressure of each seal was then measured by placing a catheter secured with a ligature into the open end of the vessel. The catheter was connected to a pressure transducer and saline was gradually infused until there was leakage from the sealed end. The acute burst pressure was defined as the peak pressure recorded. Statistical differences were evaluated by Mann-Whitney U test. RESULTS: A total of 104 seals were made on 50 vessels, 52 with each device. Median burst pressures for arteries 3.3-4.2 mm and 4.3-5.2 mm in diameter were 321 and 354 mmHg for torsional mode shears compared with 479 and 317 mmHg for linear mode shears (p = 0.193 and 0.579, respectively). For larger arteries (5.3-7.4 mm in diameter), the torsional mode shears achieved significantly higher seal strength than the linear mode shears (median burst pressure = 378 vs. 203 mmHg, p = 0.027). There was no significant correlation between the burst pressure and the vessel size for the torsional mode device (r = -0.109, p = 0.441). However, the burst pressure was adversely affected by increased vessel size for the linear mode device (r = -0.552, p = 0.000). CONCLUSIONS: Both torsional and linear mode ultrasonic shears achieved secure hemostasis on vessels up to 5.2 mm. The torsional mode shears had the extended ability to coagulate larger-sized vessels up to 7.4 mm with the same degree of confidence.

Redefining the R1 resection in pancreatic cancer.

BACKGROUND: Resection margin (RM) status in pancreatic head adenocarcinoma is assessed histologically, but pathological examination is not standardized. The aim of this study was to assess the influence of standardized pathological examination on the reporting of RM status. METHODS: A standardized protocol (SP) for pancreaticoduodenectomy specimen examination, involving multicolour margin staining, axial slicing and extensive tissue sampling, was developed. R1 resection was defined as tumour within 1 mm of the RM. A prospective series reported according to this protocol (SP series, n = 54) was compared with a historical matched series in which a non-standardized protocol was used (NSP series, n = 48). RESULTS: Implementation of the SP resulted in a higher R1 rate overall, and for pancreatic (22 of 26 85 per cent) compared with ampullary (four of 15) and bile duct (six of 13) cancer. Sampling of the circumferential RM was more extensive in the SP series and correlated with RM status. RM involvement was often multifocal (14 of 32), affecting the posterior RM most frequently (21 of 32). Survival correlated with RM status for the entire SP series (P < 0.001), but not for the NSP series. There was a trend towards better median and actuarial 5-year survival after R0 resection in the SP pancreatic cancer subgroup. CONCLUSION: Standardized examination influences the reporting of RM status.

Cyclooxygenase-2 expression associated with severity of PanIN lesions: a possible link between chronic pancreatitis and pancreatic cancer.

BACKGROUND: Cyclooxygenase-2 (COX-2) is a key modulatory molecule in inflammation and neoplasia. Increasing evidence suggests a role for COX-2 in pancreatic cancer (PAC). However, expression of COX-2 in pancreatic intraepithelial neoplasia (PanIN), the precursor lesion of PAC which is often present in chronic pancreatitis (CP), has received little attention. METHOD: COX-2 immunostaining was performed on sections of PAC (n = 26), CP (n = 34), PanIN (n = 68) and normal pancreas (n = 11). Sections were also stained for macrophages (CD68), activated pancreatic stellate cells (alphaSMA), and collagen (Sirius Red) as markers of fibrosis. Semiquantitative scoring was based on the extent and intensity of immunostaining. RESULTS: COX-2 expression was increased in PAC compared to normal (p = 0.02) with 89% of cases exceeding COX-2 immunostaining in normal ducts. In PanIN lesions, COX-2 expression increased with escalating severity of the PanIN change (p < or = 0.01). COX-2 expression was increased in PanIN-2/3 compared to normal pancreas and CP (p < or = 0.001). In ducts of CP, COX-2 expression did not differ from that in normal tissue. There was no association between COX-2 expression and clinicopathological variables. CONCLUSION: The high level of COX-2 expression in PanIN lesions suggests that this enzyme could be a therapeutic target at a non-invasive stage of pancreatic carcinogenesis and feasible for chemoprevention in CP.

In situ endoluminal brushing: a safe technique for the diagnosis of catheter-related bloodstream infection.

We assessed the safety of the endoluminal brush technique for the in situ diagnosis of central-venous-catheter (CVC)-related bloodstream infection (CRBSI). The endoluminal brush was used to investigate patients with suspected CRBSI by sampling the CVC lumen to within 3-5 cm of the catheter tip (the brush was kinked to mark the length required). Quantitative peripheral blood cultures were taken 1 min pre-brushing and 1 min and 1h post-brushing. In addition, a 1 mL sample of through-catheter blood was aspirated immediately pre- and post-brushing, and aliquots were directly plated on to blood agar to determine the load of CVC-associated bacteria. After CVC removal, catheter tips were sent for culture using the Maki roll and modified Cleri flush techniques. Of 139 suspected cases, 61 (45%) had confirmed episodes of CRBSI. No patients experienced fever or rigors, or had evidence of embolic phenomena after CVC endoluminal brushing. There was no difference overall in pre-brushing and 1-min post-brushing peripheral blood bacterial counts (P < 0.702). Peripheral and CVC blood bacterial counts were significantly reduced 1h post-brushing (P < 0.03 and P < 0.001, respectively), possibly due to removal of endoluminal biomass. The endoluminal brush technique can be safely used to diagnose CRBSI without the need for CVC removal, provided that the brush is not allowed to protrude beyond the tip of the catheter.

Prevention of catheter related bloodstream infection by silver iontophoretic central venous catheters: a randomised controlled trial.

AIM: To evaluate the efficacy of silver iontophoretic central venous catheters in preventing catheter related colonisation and bloodstream infection among high risk patients in a tertiary hospital. METHODS: Patients requiring central venous access for a period greater than seven days were stratified into two groups according to systemic inflammatory response syndrome criteria before being randomly assigned to receive either silver iontophoretic or control catheters. The incidence of catheter colonisation and catheter related bloodstream infection (CRBSI) was recorded. RESULTS: Three hundred and four single lumen study catheters were inserted into 268 patients. Total duration of catheterisation was 5449 days (median, 12 days/catheter). Complete data could be evaluated in 270 catheters: 128 silver iontophoretic catheters and 140 untreated catheters. Forty seven silver iontophoretic catheters (36.7%) were colonised compared with 48 control catheters (33.8%). Seven cases (5.5%) of CRBSI occurred in patients who received silver iontophoretic catheters, compared with 11 cases (7.7%) in patients receiving control catheters. There was no significant difference in the incidence of catheter colonisation or CRBSI between silver iontophoretic and control catheters. When the duration of catheter placement was taken into consideration, Kaplan-Meier analysis showed no significant difference in the risk of CRBSI between the silver iontophoretic catheters and the untreated catheters (p = 0.77). CONCLUSION: There was no significant difference in the incidence of catheter colonisation or CRBSI among high risk patients between silver iontophoretic catheters and control catheters. Future prospective, randomised studies with a larger number of catheters are encouraged to confirm or refute these results.

Calcitonin precursors: early markers of gut barrier dysfunction in patients with acute pancreatitis.

BACKGROUND: Severe acute pancreatitis is associated with an early increase in intestinal permeability and endotoxemia. Endotoxin is a potent stimulator for the production and release of procalcitonin and its components (calcitonin precursors; [CTpr]). The aim of this study is to evaluate the role of plasma CTpr as an early marker for gut barrier dysfunction in patients with acute pancreatitis. METHODS: Intestinal permeability to macromolecules (polyethylene glycol 3350), serum endotoxin and antiendotoxin core antibodies, plasma CTpr, and serum C-reactive protein (CRP) were measured on admission in 60 patients with acute pancreatitis. Attacks were classified as mild (n = 48) or severe (n = 12) according to the Atlanta criteria. RESULTS: Compared with mild attacks of acute pancreatitis, severe attacks were significantly associated with an increase in intestinal permeability index (median: 0.02 vs. 0.006, P < 0.001), the frequency of endotoxemia (73% vs. 41%, P = 0.04), and the extent of depletion of serum IgM antiendotoxin antibodies (median: 43 MMU vs. 100 MMU, P = 0.004). Plasma CTpr levels were significantly elevated in patients with severe attacks compared with mild attacks on both the day of admission and on day 3 (median: 64 vs. 22 fmol/mL, P = 0.03; and 90 vs. 29 fmol/mL, P = 0.003 respectively). A positive and significant correlation was observed between the admission serum endotoxin and plasma CTpr levels on admission (r = 0.7, P < 0.0001) and on day 3 (r = 0.96, P < 0.0001), and between plasma CTpr on day 7 and the intestinal permeability index (r = 0.85, P = 0.0001). In contrast, only a weak positive correlation was observed between peak serum levels of CRP and plasma CTpr on admission (r = 0.3, P = 0.017) and on day 7 (r = 0.471, P = 0.049), as well as between CRP and each of the admission serum endotoxin (r = 0.3, P = 0.03) and the intestinal permeability index (r = 0.375, P = 0.007). CONCLUSIONS: In patients with acute pancreatitis, plasma concentrations of CTpr appear to reflect more closely the derangement in gut barrier function rather than the extent of systemic inflammation.

Randomized clinical trials to determine the role of topical glyceryl trinitrate in peripheral intravenous nutrition.

BACKGROUND: The contribution of glyceryl trinitrate (GTN) to prevention of peripheral vein thrombophlebitis (PVT) during peripheral intravenous nutrition delivered by fine-bore midline intravenous catheter is unclear. The aim of this study was to establish its role. METHODS: Two consecutive randomized clinical trials were conducted. In trial 1 patients were randomized to receive standard peripheral intravenous nutrition containing heparin and hydrocortisone with or without the placement of a topical GTN patch (triple therapy or dual therapy). In trial 2 patients were randomized to receive standard peripheral intravenous nutrition with either dual therapy or topical GTN alone (monotherapy). RESULTS: Dual therapy was as effective as triple therapy in preventing PVT (incidence 10 of 37 versus 11 of 39 patients respectively). Dual therapy reduced the incidence and increased the time to onset of PVT compared with monotherapy (14 of 41 versus 22 of 35 patients respectively, P = 0.012; median 17.3 (95 per cent confidence interval (c.i.) 13.4 to 21.1) versus 8.9 (95 per cent c.i. 6.7 to 11.0) days, P = 0.007). CONCLUSION: Use of a topical GTN patch confers no benefit when peripheral intravenous nutrition is delivered via a fine-bore midline intravenous catheter.

Micropuncture cholecystectomy vs conventional laparoscopic cholecystectomy: a randomized controlled trial.

BACKGROUND: The aim of this study was to compare micropuncture laparoscopic cholecystectomy (MPLC), with three 3.3-mm cannulas and one 10-mm cannula with conventional laparoscopic cholecystectomy (CLC). METHODS: Patients were randomized to undergo either CLC or MPLC. The duration of each operative stage and the procedure were recorded. Interleukin-6 (IL-6), adrenocorticotropic hormone (ACTH), and vasopressin were sampled for 24 h. Visual analogue pain scores (VAPS) and analgesic consumption were recorded for 1 week. Pulmonary function and quality of life (EQ-5D) were monitored for 4 weeks. Statistical analysis was performed using the Mann-Whitney test or Fisher's exact test. Results are expressed as median (interquartile range). RESULTS: Forty-four patients entered the study, but four were excluded due to unsuspected choledocholithiasis (n = 3) or the need to reschedule surgery (n = 1). The groups were comparable in terms of age, duration of symptoms, and indications for surgery. Total operative time was similar (CLC, 63 [52-81] min vs MPLC 74 [58-95] min; p = 0.126). However, time to place the cannulas after skin incision (CLC, 5:42 [3:45-6:37] min vs MPLC, 7:38 [5:57-10:15] min; p = 0.015) and to clip the cystic duct after cholangiography (CLC, 1:05 [0:40-1:35] min vs MPLC, 3:45 [2:26-7:49] min; p <0.001) were significantly longer for MPLC. Six CLC patients and one MPLC patient required postoperative parenteral opiates (p = 0.04). Oral analgesic consumption was similar in both groups (p = 0.217). Median VAPS were lower at all time points for MPLC, but this finding was not significant (p = 0.431). There were no significant differences in postoperative stay, IL-6, ACTH or vasopressin responses, pulmonary function, or EQ-5D scores. CONCLUSIONS: The thinner instruments did not significantly increase the total duration of the procedure. MPLC reduced the use of parenteral analgesia postoperatively, which may prove beneficial for day case patients, but it did not have a significant impact on laboratory variables, lung function or quality of life.

Calcitonin precursors in the prediction of severity of acute pancreatitis on the day of admission.

BACKGROUND: Calcitonin precursors are sensitive markers of inflammation and infection. The aim of this study was to evaluate the role of plasma calcitonin precursor levels on the day of admission in the prediction of severity of acute pancreatitis, and to compare this with the Acute Physiology And Chronic Health Evaluation (APACHE) II scoring system. METHODS: Plasma concentrations of calcitonin precursors were determined on admission in 69 patients with acute pancreatitis. APACHE II scores were calculated on admission. Attacks were classified as mild (n = 55) or severe (n = 14) according to the Atlanta criteria. Plasma calcitonin precursor levels were determined with a sensitive radioimmunoassay. RESULTS: On the day of hospital admission, plasma levels of calcitonin precursors were significantly greater in patients with a severe attack compared with levels in those with a mild attack of pancreatitis (median 64 versus 25 fmol/ml; P = 0.014), but the APACHE II scores were no different (median 9 versus 8; P = 0.2). The sensitivity, specificity, positive predictive and negative predictive values, and accuracy for the prediction of severe acute pancreatitis were 67, 89, 57, 93 and 85 per cent respectively for plasma calcitonin precursor levels higher than 48 fmol/ml, and 69, 45, 23, 86 and 50 per cent respectively for an APACHE II score greater than 7. Differences in the specificity and accuracy of the two prognostic indicators were significant (P < 0.001 and P = 0.001 respectively). A plasma calcitonin precursor concentration of more than 160 fmol/ml on admission was highly accurate (94 per cent) in predicting the development of septic complications and death. CONCLUSION: The assay of plasma calcitonin precursors on the day of admission to hospital has the potential to provide a more accurate prediction of the severity of acute pancreatitis than the APACHE II scoring system.

Increased nitric oxide excretion in patients with severe acute pancreatitis: evidence of an endotoxin mediated inflammatory response?

BACKGROUND AND AIMS: Nitric oxide represents a potential key mediator of the local and systemic manifestations of acute pancreatitis (AP) in experimental models but its role in human disease is uncertain. We therefore sought to assess if systemic nitric oxide (NO) production is elevated in severe AP and determine whether this is a reflection of biochemical severity or endotoxin exposure. PATIENTS AND METHODS: Patients were recruited within 72 hours of pain onset. NO derived nitrite excretion determined from a 24 hour sterile urine collection was correlated with intestinal macromolecular permeability (polyethylene glycol excretion ratio), markers of systemic endotoxin exposure (IgG:IgM endotoxin core antibody (EndoCAb) ratio), disease severity, and the magnitude of systemic inflammation (peak C reactive protein (CRP) and Acute Physiology and Chronic Health Evaluation score II (APACHE-II)). RESULTS: In patients with a severe attack (n=20), nitrite excretion was increased significantly compared with patients with a mild attack (n=45, 20.6 micro g v 15.65 micro g; p<0.00) and the latter with healthy controls (n=20, p=0.004). Nitrite excretion correlated strongly with both intestinal permeability (r=0.7, p=0.006) and EndoCAb ratio (r=0.7, p<0.01) but not with CRP or APACHE-II scores (p>0.1). CONCLUSIONS: Total urinary nitrite excretion is increased in patients with severe AP, and may not be simply a reflection of systemic inflammation, but potentially a consequence of endotoxin mediated upregulation of inducible NO synthase activity.

Laparoscopic cholecystectomy: are patients with biliary pancreatitis at increased operative risk?

BACKGROUND: Previous reports of laparoscopic cholecystectomy (LC) in patients with biliary pancreatitis suggested increased operative difficulty, high rates of conversion, and greater morbidity and mortality. METHODS: Between 1990 and 1997, LC was performed for biliary pancreatitis in 63 patients (Group I) and for other causes in 829 patients (Group II). RESULTS: Patients with biliary pancreatitis were significantly older (median age 57 vs 50 years, p = 0.009), with greater co-morbidity (ASA III/IV 24% vs 11%, p = 0.008). The groups were comparable with respect to the frequency of previous abdominal operations, acute inflammation of the gallbladder, and the frequency of bile duct calculi detected by intraoperative cholangiography. Moderate to severe adhesions involving the gallbladder were significantly more frequent in patients with biliary pancreatitis (46% vs 29%, p = 0.004). No significant differences were observed between the two groups with respect to intraoperative (1.5% Group I vs 6.0% Group II, p = 0.109) or postoperative complications (10% vs 8%, p = 0.426), conversion rate (0 vs 2.7%, p = 0.181), or duration of operation (median 92 vs 85 min, p = 0.33). CONCLUSION: Despite increased age and co-morbidity and more frequent adhesions, our data showed no evidence that intraoperative or postoperative complications were more frequent in patients with biliary pancreatitis than in other patients undergoing LC.

Maternal stress and preterm birth.

This study examined a comprehensive array of psychosocial factors, including life events, social support, depression, pregnancy-related anxiety, perceived discrimination, and neighborhood safety in relation to preterm birth (<37 weeks) in a prospective cohort study of 1,962 pregnant women in central North Carolina between 1996 and 2000, in which 12% delivered preterm. There was an increased risk of preterm birth among women with high counts of pregnancy-related anxiety (risk ratio (RR) = 2.1, 95% confidence interval (CI): 1.5, 3.0), with life events to which the respondent assigned a negative impact weight (RR = 1.8, 95% CI: 1.2, 2.7), and with a perception of racial discrimination (RR = 1.4, 95% CI: 1.0, 2.0). Different levels of social support or depression were not associated with preterm birth. Preterm birth initiated by labor or ruptured membranes was associated with pregnancy-related anxiety among women assigning a high level of negative impact weights (RR = 3.0, 95% CI: 1.7, 5.3). The association between high levels of pregnancy-related anxiety and preterm birth was reduced when restricted to women without medical comorbidities, but the association was not eliminated. The prospective collection of multiple psychosocial measures on a large population of women indicates that a subset of these factors is associated with preterm birth.

The early increase in intestinal permeability and systemic endotoxin exposure in patients with severe acute pancreatitis is not associated with systemic bacterial translocation: molecular investigation of microbial DNA in the blood.

INTRODUCTION: Sepsis is the main cause of late mortality in patients with severe acute pancreatitis and is largely attributed to secondary infection of pancreatic necrosis with gram-negative enteric organisms. This is commonly preceded by a significant increase in intestinal colonization with such microbes and with early increases in intestinal permeability, thus suggesting a mechanism of bacterial translocation. Whilst cultures of blood specimens from these patients often remain sterile, it is conceivable that bacteria might translocate in small volumes with detrimental effects but elude detection by standard microbial culture techniques. AIMS: To investigate the incidence and frequency with which bacterial DNA may exist in the systemic circulation of patients with acute pancreatitis and to relate that to disease severity, changes in intestinal permeability, and systemic endotoxin exposure. METHODOLOGY: Blood samples were obtained at admission and on days 3 and 7 from 26 patients with acute pancreatitis (seven with severe cases) and from 10 healthy controls for DNA extraction and standard microbial cultures. Polymerase chain reaction techniques were used to amplify a gene region (16S ribosomal RNA) found in all bacteria. Levels of serum endotoxin and antibodies to endotoxin core (EndoCAb) were measured at admission, and intestinal permeability to the macromolecule polyethylene glycol 3350 was determined within 72 hours of the onset of symptoms. RESULTS: Blood cultures yielded and enterococci for one patient with a severe attack and coagulase-negative staphylococci for another patient with a mild attack. No bacterial DNA was found in any of the samples. Endotoxemia was detected in 20 patients (five with severe cases), and levels of serum IgM EndoCAb were depleted in patients with severe attacks but remained relatively unchanged during mild attacks (p = 0.033). Intestinal permeability was significantly increased in patients with severe attacks of acute pancreatitis but remained unchanged during mild attacks (p < 0.05). CONCLUSIONS: Whilst severe attacks of acute pancreatitis are associated with early derangement in gut barrier function and systemic endotoxin translocation, there is no molecular evidence for associated bacterial "translocation."

DNA fingerprinting analysis of coagulase negative staphylococci implicated in catheter related bloodstream infections.

AIMS: The epidemiological assessment of cases of coagulase negative staphylococcal catheter related bloodstream infection. METHODS: Two hundred and thirty patients with suspected catheter related bloodstream infection were evaluated over a two year period. Central venous catheters were cultured both endoluminally and extraluminally. Peripheral blood, catheter hubs, skin entry, and skin control sites were also cultured. Pulsed field gel electrophoresis (PFGE) was used to DNA fingerprint coagulase negative staphylococci isolated from patients with presumptive catheter related bloodstream infection. RESULTS: Sixty cases of catheter related bloodstream infection were identified, 21 of which were attributed to coagulase negative staphylococci. Two hundred and ninety four separate isolates of coagulase negative staphylococci from the 21 cases of catheter related bloodstream infection were subjected to PFGE (mean of 14 for each case). Catheter related bloodstream infection was only confirmed by PFGE analysis in 16 of the 21 cases because in the remaining five cases peripheral blood and central venous catheter coagulase negative staphylococci isolates were different. Skin entry, control skin, and central venous catheter hub isolates matched peripheral blood isolates in six, four, and seven cases, respectively. Coagulase negative staphylococci isolates could not be cultured from the patients' own skin in seven cases of catheter related bloodstream infection. Central venous catheter lumens were colonised in all cases of catheter related bloodstream infection compared with 44-81% of cases that had positive external surface catheter tip cultures, depending on the threshold used to define significant growth. CONCLUSIONS: Catheter related bloodstream infection as a result of coagulase negative staphylococci may be over stated in about a quarter of cases, unless a discriminatory technique is used to fingerprint isolates. No single, simplistic route of bacterial contamination of central venous catheters was identified, but endoluminal catheter colonisation is invariably present in cases of catheter related bloodstream infection.