Eradication of multi-drug resistant Acinetobacter from an intensive care unit.

BACKGROUND: Acinetobacter baumannii is a gram-negative coccobacillus that causes outbreaks of nosocomial infections in ICUs. Due to resistance to multiple antibiotics, management of clusters of A. baumannii is useful as a model in eradication of multi-drug resistant infections. We outline the evolution of an A. baumannii outbreak, focusing on methods of transmission and multidisciplinary measures aimed at eliminating it from the ICU. METHODS: Patients in an urban, tertiary care medical center from November 1996 to December 1997 having positive cultures for multi-drug resistant A. baumannii are included in this study. A. baumannii was isolated on blood agar and MacConkey cultures and identified by Vitek panel. Disk diffusion including amikacin, imipenem, polymyxin B, and sulbactam were used to determine resistance. RESULTS: An outbreak of 52 patients (27 infected, 25 colonized) with 68 positive sites began with the transfer of a colonized >50% total body surface area burn patient from an outside hospital. Within 3 days, the index patient was in the burn ICU, coronary care unit, and medical ICU. Soon, clusters of patients with A. baumannii infections sensitive only to polymyxin B were seen in those units and, ultimately, the surgical ICU. On typing, 2 strains were found, PFGE B and C. Given the level of antibiotic resistance, patients with colonization or infection were cohorted and placed on contact isolation. Strict antiseptic measures, such as hand-washing, barrier isolation, equipment and room cleaning, sterilization of ventilator equipment, and dedication of medical equipment to each patient were instituted. Still, positive environmental cultures were found in ventilator water traps, sinks, and bedrails. Sporadic cases continued for a total of 13 months, with 10 deaths resulting from the infections. CONCLUSION: A. baumannii is a mildly virulent organism that becomes resistant to antimicrobials. Because of multiple antibiotic resistance, strict contact isolation cohorting and antiseptic technique are the primary modes of containment. This outbreak serves as a model of eradication of multi-drug resistant organisms from ICUs. These measures will become of greater importance as nosocomial organisms develop increasing resistance to antimicrobials.

New epidemiology for postoperative nosocomial infections.

Changes in health care delivery systems over the last decade have resulted in a major increase in outpatient surgery and a higher severity of illness for inpatients. We sought to determine the effects of this change on the epidemiology of postoperative surgical infections. Historical data on incidence and epidemiology of infection were obtained from peer-reviewed articles published between 1960 and 1999 (MEDLINE). All nosocomial infections in 5035 patients admitted to a tertiary-care university hospital surgical intensive care unit between January 1994 and December 1997 were prospectively identified and classified as wound, urinary tract, bloodstream, or pneumonia. Incidence of bacterial isolates at each site was also recorded. From these data we determined infection rates per 100 admissions. We also identified all device-related nosocomial infections and calculated infection rates. Comparisons between time periods were made. In the 1960s wound infections constituted the predominant postoperative infection at 46 per cent. This was replaced by urinary tract infection in the 1970s (44%) and 1980s (32%) and closely followed by bloodstream infections (25%). In the 1990s nosocomial pneumonia became the most common postoperative infection, comprising 43 per cent of surgical intensive care unit infections. Analysis of the bacteriology also revealed changing trends with primarily gram-positive organisms in the 1960s followed by an increase in methicillin-resistant Staphylococcus in the 1970 to 1980s, and currently resistant gram-negative bacteria predominate. The incidence of fungal infections has steadily increased. This survey identified a new epidemiology for postoperative surgical infections. Over the last several decades the reported wound infections have been markedly decreased and there is little change in urinary tract infection. Nosocomial pneumonia with resistant gram-negative bacteria now predominates along with increased incidence of fungal infections. Currently, postoperative infections are now more severe, involve critical organs, and require close monitoring of the changing patterns of pathogens.

Determination of burn depth with noncontact ultrasonography.

Early excision and grafting is the current treatment of choice for deep dermal and full-thickness burn wounds that will not heal spontaneously within 3 weeks. The time needed for the burn wound to heal is estimated with clinical assessment of the burn depth; this is often an inaccurate method. Therefore we have developed a new and unique noncontact ultrasonographic method to estimate burn depth. This study was designed to determine the practical utility and accuracy of noncontact ultrasonography for the assessment of burn depth. Seventy-eight burn sites and 42 normal skin sites (control sites) of 15 patients (age, 18-63 years) with burns of 2% to 35% total body surface area were evaluated. The burn sites were scanned with a prototype noncontact ultrasonographic system 1 and 3 days after the burn injuries. The probe was held 1 inch from the skin, and the time spent on each site was approximately 5 minutes. The ultrasonographic results were interpreted by an investigator who was blinded to the clinical findings. Clinical assessment of the burn wounds was made on the same days by 2 experienced physicians who were blinded to the results of the ultrasonography. The investigators were asked to categorize the burn wounds into those that would heal within 3 weeks and those that would not. With this method, we were able to visualize the epidermis, dermis, and dermal-fat interface in normal skin. The destruction of the dermal-fat interface was interpreted as a deep burn, which would not heal within 3 weeks. The overall accuracy of the noncontact ultrasonography in the prediction of which burn wounds would heal within 3 weeks was 96%. The results of this study show that noncontact ultrasonography will allow for the rapid evaluation of burn depth with high accuracy, without contacting the patient, and without causing pain or discomfort.

Nosocomial infections in the surgical intensive care unit: a difference between trauma and surgical patients.

In 1970, the Centers for Disease Control and Prevention (CDC) established the National Nosocomial Infection Surveillance System to assist institutions with infection surveillance, data collection, and processing. This facilitates interinstitutional comparison for nosocomial infection rates. Nosocomial infection rates in the surgical intensive care unit have been shown to be different from the medical intensive care unit. Whether there exists a difference in infection rates between trauma and surgical patients in the intensive care unit has not been established. Our objective was to determine whether there is a difference in rates of nosocomial infections between trauma and surgical patients in the surgical intensive care unit. From January 1995 through December 1997, we reviewed 3715 admissions to the surgical intensive care unit and separated them into trauma (1272) or surgical (2443) cases. We documented all nosocomial pneumonias, urinary tract infections, bloodstream infections, and surgical site infections. From these data we determined infection rates per 100 admissions. We also identified all device-related nosocomial infections and calculated infection rate by current CDC standards using number of device infections divided by number of device-days times 1000. We found that the overall trauma patient infection rate was 11.64 per cent compared with 6.43 per cent for surgical patients (P<.001). Using conventional infection rate criteria, trauma patients had higher frequency in the rate of ventilator-associated pneumonia (6.13% vs. 2.50%; P<0.001), urinary tract infection (2.36 versus 1.76; P<0.2), and bloodstream infection (2.52% versus 1.27%; P<0.01). However, when using the CDC guidelines, which correct for the number of device-days for infections, only the difference in rate of pneumonia between the two groups reached statistical significance (23.9 rate for trauma patients vs. 16.7 for the surgery group; P<0.005). We conclude that trauma patients are at higher risk for nosocomial infections than routine surgical patients. Because of this difference, centers should collect and report data separately for trauma and surgical patients in the intensive care unit. Specific attention should be focused on the causes and prevention of increased rates of nosocomial pneumonia in trauma patients.

Improved survival following massive transfusion in patients who have undergone trauma.

HYPOTHESIS: Survival following massive transfusion in patients who have undergone trauma has improved during the past 10 years. DESIGN: Retrospective cohort study. SETTING: Academic level I trauma center in an urban community. PATIENTS: All patients who underwent trauma and who received greater than 50 U of packed red blood cells or whole blood in the 48 hours following admission to the emergency department. INTERVENTIONS: Data were obtained from blood bank records, the trauma registry, patient medical records, and hospital purchasing records. Patients were divided into 2 groups for comparison (early [1988-1992] and late [1993-1997] periods). MAIN OUTCOME MEASURES: Survival and changes in trauma care provision. RESULTS: Survival following massive transfusion in patients who have undergone trauma has significantly increased during the past 10 years (16% vs 45%, early vs late period, P = .03). Factors associated with poor outcome included male sex, major vascular injury, high Injury Severity Score, severe acidosis, prolonged hypotension, refractory hypothermia, and decreased use of platelet transfusion (all P<.05). In the later period, there was more aggressive correction of coagulopathy, more efficient use of warming measures, decreased operative times for the initial operation, and increased use of component therapy (all P<.05). CONCLUSIONS: Survival following massive transfusion has significantly (P = .03) increased during the past 10 years. Factors that may have contributed to this include more effective and efficient rewarming procedures, improved application of damage control techniques, more aggressive correction of coagulopathy, and improved blood banking procedures.

Improved imaging of carotid artery bifurcation using helical computed tomographic angiography.

Although duplex scan and magnetic resonance angiography (MRA) provide reliable and noninvasive tests for detecting extracranial carotid artery disease, they sometimes fail to differentiate between high-grade stenosis and total carotid occlusion. Helical computed tomographic angiography (CTA) is a safe, noninvasive technique that allows the rapid acquisition of data that can be reconstructed into two- and three-dimensional images. Axial images can be magnified and provide a cross-sectional view of the carotid vessel and the atherosclerotic plaque. Maximal intensity projection technique allows data to be reconstructed into images that closely resemble conventional arteriograms. Helical CTA has previously been shown to have a diagnostic accuracy approaching 90%. We present two case reports demonstrating the utility of helical CTA in carotid artery imaging when duplex scan and MRA results are ambiguous. These cases illustrate improved carotid imaging with helical CTA. Duplex scan results are unreliable in the presence of thick calcified plaques, and severe stenoses can be misread as occlusion by duplex and MRA due to low blood flow. Thus, helical CT angiography should be considered as a confirmatory test, before arteriography, when duplex scan or MRA results are equivocal.

A prospective evaluation of PTFE graft patency and surveillance techniques in hemodialysis access.

The purpose of this study was to perform a prospective multicenter evaluation of the patency, complications, and predictive factors of patency for 6-mm expanded polytetrafluoroethylene (ePTFE) grafts used in hemodialysis access. Eighty-six patients were evaluated; the mean age was 55.8 years (range 23-90), 46 patients were female. Patency and complications were assessed at the initial dialysis and 1, 3, 6, 9, and 12 months postoperatively. Kaplan-Meier survival curves were calculated to determine primary and secondary patency, and log-rank analysis was used to determine differences between curves. The Student's t-test was used to compare groups. Primary and secondary patency rates at 1 year were 43% and 64%. Venous line pressures tended to rise over time. Recirculation values and blood flow rates during dialysis showed no correlation to graft patency. These results show that ePTFE provides a suitable secondary choice for vascular access for end-stage renal disease patients in whom an autogenous fistula is not possible. Thrombosis and anastomotic stenosis are common and should be aggressively identified and treated to prolong overall graft survival.

New advances in the use of antimicrobial agents in surgery: intra-abdominal infections.

Advances in both technical methods and antimicrobial therapy have significantly reduced morbidity and mortality for secondary (enterogenous) or community-acquired intra-abdominal infections. Presumptive antimicrobial therapy for most community-acquired intra-abdominal infection can be safely initiated with a single broad-spectrum antimicrobial effective against the expected Enterobacteriaceae and anaerobic flora. Beta-lactams and carbapenems are effective against gram-negative rods and anaerobes, achieve therapeutic levels rapidly, and have low toxicity in the absence of penicillin allergy. Second generation cephalosporins (e.g. cefoxitin and cefotetan) remain useful in surgical prophylaxis and treatment of mild community-acquired pneumonia, but limitations in their spectra and antimicrobial resistance restrict their utility in more serious infections. The fourth generation cephalosporins are also effective, but should be combined with other antimicrobials such as metronidazole for adequate anaerobic coverage. Preliminary data on new fluoroquinolones are scant, but promising results were obtained in one clinical trial. We predict the current trend toward the use of broad-spectrum single agent antimicrobials for therapy of intra-abdominal infection will continue.

Helical CT angiography in the preoperative evaluation of carotid artery stenosis.

PURPOSE: To determine the utility and accuracy of helical CT angiography (CTA) in the evaluation of carotid artery stenosis. METHODS: A comparison of CTA and conventional arteriogram was performed in 53 patients undergoing evaluation for carotid artery stenosis. Ninety-six carotid systems were evaluable. CTA stenosis was determined by the percent of area reduction seen on axial images through the level of greatest narrowing. MIP images were used to identify the point of maximal stenosis and to visualize overall vascular anatomy. The percent diameter stenosis was measured on conventional arteriograms using strict North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) criteria. RESULTS: Significant correlation was found between CTA and arteriography (NASCET method R=0.87, ECST method R=0.87, p < 0.001). Using NASCET >60% as an indicator for disease, CTA had a sensitivity of 87%, specificity of 90%, accuracy of 89%, negative predictive value of 88%, and positive predictive value of 89%. CTA identified plaque characteristics such as ulcerations (8), occlusion (10), fatty plaques (22), calcifications (48), and fibrosis (2). CTA underestimated 2 cases of short segment stenoses because of volume averaging, but this discrepancy was detected by duplex scan. No complications or renal dysfunction occurred with CTA; 1 patient became symptomatic during arteriography, necessitating termination of the procedure. CONCLUSION: CTA is a safe, non-invasive technique that precisely measures carotid artery area reduction and highly correlates to conventional arteriography. With this new technology, the current standards for carotid artery imaging may need to be reevaluated, and the precise role for helical CTA more clearly defined.

Ethanol added to resuscitation improves survival in an experimental model of hemorrhagic shock.

Ethyl alcohol induces systemic vasodilation, decreases platelet aggregation, and inhibits neutrophil activation in vivo. Alcohol may thus be of potential benefit in resuscitation from shock by improving microcirculation. The purpose of this study was to test the effects of ethanol (ETOH) in resuscitation from hemorrhagic shock. Blood pressure, tissue pO2, white blood cell (WBC) and platelet adhesiveness, and survival were measured for 60 male Sprague-Dawley rats in a blinded and randomized study. Anesthetized animals were phlebotomized to 60 per cent of their blood volume, and maintained in shock for 45 minutes. Resuscitation was by continuous infusion of Lactated Ringers (LR) at 2 x shed blood volume over 1 hour. The experimental group received LR and ETOH (1.25 mL/kg). Control rats received LR and placebo. Mean arterial pressure was not significantly different, nor was WBC adhesiveness index different. However, postresuscitation platelet adhesiveness index was significantly higher in control rats than in ETOH rats. Postresuscitation total platelet arterial-venous difference was also greater in controls than in ETOH rats. Average tissue pO2 for ETOH rats (47 +/- 8.2 mm Hg) was significantly higher than controls (39.0 +/- 9.8 mm Hg) during resuscitation (P = 0.0001). Survival for ETOH rats (70%) was significantly higher than controls (20%) (P = 0.003). Our data suggests that ETOH added to resuscitation from shock improves survival by inhibiting platelet activation and increasing tissue perfusion.

Soluble cytokine receptors and receptor antagonists are sequentially released after trauma.

Cytokine receptors and receptor antagonists (RAs) have been identified in trauma patients. We hypothesized that after traumatic injury, a sequential release of soluble cytokine receptors and RAs may exist that mirrors the release of the primary cytokines themselves. Twenty-two patients were included in the study: 14 males and 8 females. The mean age was 30.1 +/- 12.5 (range, 19 to 71), and the mean Injury Severity Score was 28.7 +/- 12.6 (range, 4 to 57). There were 15 survivors and 7 nonsurvivors. Samples were collected on arrival to the emergency department and at serial intervals for up to 7 days. Monoclonal antibody enzyme-linked immunosorbent assay kits to tumor necrosis factor (TNF), soluble TNF-receptor (sTNF-R) 55 kd and 75 kd, interleukin (IL)-1 and IL-1 RA, and IL-2 and IL-2r were used. Sera from 22 healthy individuals were used as normal controls. No TNF, IL-1, or IL-2 could be detected in any patient sera after injury. Control levels for the soluble cytokine receptors and RAs were as follows: sTNF-R 55 kd, 607 +/- 89 pg/mL; sTNF-R 75 kd, 2,141 +/- 169 pg/mL; IL-1 RA, 291 +/- 35 pg/mL; and IL-2r, 426 +/- 53 U/mL. In trauma patients, both 55 kd and 75 kd sTNF-R were significantly elevated on arrival to the emergency department, with values of 2,441 +/- 506 pg/mL (p < 0.001) and 4,736 +/- 537 pg/mL (p < 0.001), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Trauma causes sustained elevation of soluble tumor necrosis factor receptors.

BACKGROUND: Soluble tumor necrosis factor receptors (sTNF-R) are thought to modulate the systemic effects of tumor necrosis factor (TNF) by binding to serum TNF and preventing its interaction with target organs. Recently, it has been shown that traumatic injury causes the early release of the soluble forms of the 55 and 75 kDa membrane receptors for TNF. This study was done to determine the magnitude of TNF receptor elevation after trauma, to delineate the duration of this elevation, and to determine if sTNF-R levels correlate with severity of injury and outcome. STUDY DESIGN: One hundred injured patients treated at a Level I Trauma Center were included in the study (74 males, 26 females, mean age of 29.4 years [range of ten to 72 years], mean injury severity score of 16.8 [range of zero to 75]). Serum samples were drawn from these patients beginning within one hour of injury and continuing for as many as 15 days. Samples were analyzed using polyclonal ELISA assays for TNF and sTNF 55 and 75 kDa receptor levels; control levels of receptor were determined from healthy volunteers. RESULTS: Tumor necrosis factor was not measurable, but trauma caused immediate elevation of both receptor levels (within one hour of injury). Receptor levels remained elevated for as many as 15 days after injury. Late variations in levels were related to complications, that is, hypoxia, infection, and sepsis. Levels were significantly more elevated in critically ill patients and nonsurvivors. CONCLUSIONS: We conclude that sTNF-R levels are significantly elevated after trauma, in the absence of measurable TNF. Levels are elevated for variable periods of time, which seem to depend on the severity of injury and complications.

Amrinone improves survival in hemorrhagic shock.

Amrinone is a noncatecholamine inotropic agent used clinically in the management of heart failure. The purpose of this study was to determine if intravenous (i.v.) infusion of amrinone has beneficial effects during resuscitation from experimental hemorrhagic shock. Effectiveness was defined as significantly improved survival rate. Mean arterial pressure (MAP) and tissue oxygen tension (pO2) were measured to assess the physiologic effects of amrinone. Two separate randomized and blinded survival trials were conducted. In each trial, rats were randomly assigned to either a control group (n = 10) or an experimental group (n = 10). All animals were bled 27 ml/kg over 2 minutes and maintained in shock for 45 minutes before resuscitation. Resuscitation in placebo (control) animals was with 54 ml/kg (2 times the hemorrhage volume) Lactated Ringer's solution over 1 hour, whereas resuscitation in drug-treated animals was with a 0.75 mg/kg bolus amrinone over 3 minutes followed by 54 ml/kg Lactated Ringer's solution and 5 ug/kg/min infusion over 1 hour. Results were that resuscitation with amrinone significantly increased MAP, tissue pO2, and survival over resuscitation with Lactated Ringer's alone (P < 0.05). In both trials, survival rates increased by more than 66 per cent in the amrinone groups.

Relationship of Haemophilus influenzae type b pilus structure and adherence to human erythrocytes.

Six strains of Haemophilus influenzae type b, some expressing immunologically different pili, showed identical patterns of binding to erythrocytes that were characterized for 38 blood group antigens. All six strains appeared to bind to the Anton antigen, as they agglutinated all erythrocytes tested except cord erythrocytes and those characterized as Lu(a-b-), dominant type, including Anton-negative cells.