Editor's Choice - Trends in Management and Outcomes of Type B Aortic Dissection: A Report From the International Registry of Aortic Dissection

OBJECTIVE

To describe the trends in management and outcomes of patients with acute type B aortic dissection in the International Registry of Acute Aortic Dissection.

METHODS

From 1996 - 2022, 3 908 patients were divided into similar sized quartiles (T1, T2, T3, and T4). In hospital outcomes were analysed for each quartile. Survival rates following admission were compared using Kaplan-Meier analyses with Mantel-Cox Log rank tests.

RESULTS

Endovascular treatment increased from 19.1% in T1 to 37.2% in T4 (ptrend < .001). Correspondingly, medical therapy decreased from 65.7% in T1 to 54.0% in T4 (ptrend < .001), and open surgery from 14.8% in T1 to 7.0% in T4 (ptrend < .001). In hospital mortality decreased in the overall cohort from 10.7% in T1 to 6.1% in T4 (ptrend < .001), as well as in medically, endovascularly and surgically treated patients (ptrend = .017, .033, and .011, respectively). Overall post-admission survival at three years increased (T1: 74.8% vs. T4: 77.3%; p = .006).

CONCLUSION

Considerable changes in the management of acute type B aortic dissection were observed over time, with a significant increase in the use of endovascular treatment and a corresponding reduction in open surgery and medical management. These changes were associated with a decreased overall in hospital and three year post-admission mortality rate among quartiles.

Cohort study of fever and leukocytosis as diagnostic and prognostic indicators in infected surgical patients

The presence of fever and leukocytosis have traditionally been utilized as important diagnostic markers of infection despite some who question their reliability. To examine this point, the role of fever and leukocytosis as diagnostic and prognostic indicators for surgical infections was evaluated. A prospective observational study was performed on all patients with suspected infection in 1997 on the general surgical services at a university hospital. Fever was defined as maximum temperature (Tmax) > or = 38.5 degrees C, and leukocytosis was defined as a white blood cell (WBC) count > or = 11,000/microl. Among all infections, patients presenting with a Tmax > or = 38.5 degrees C were younger (51.3 +/- 1.1 vs. 53.8 +/- 0.9 years, p = 0.005) and had a higher APACHE II score (15.1 +/- 0.5 vs. 11.4 +/- 0.4; p < 0.001). By logistic regression analysis chronic renal insufficiency was associated with a Tmax < 38.5 degrees C [odds ratio (OR) 0.371, 95% confidence interval (CI) 0.195-0.704], and chronic steroid therapy was associated with a WBC count < 11,000/microl (OR 0.556, 95% CI 0.335-0.921). In addition, infected transplant patients were more likely to present with a Tmax < 38.5 degrees C and a WBC count < 11,000/microl (OR 0.195, 95% CI 0.075-0.502). Mortality rates for infected patients with a Tmax < 38.5 degrees C or > 38.5 degrees C were 11.6% and 12.9%, respectively (p < 0.7), and the lengths of stay were 14 +/- 1 and 18 +/- 1 days, respectively (p < 0.03). Mortality rates for patients with a WBC count < 11,000/microl or > 11,000/microl were 4.7% and 18.6%, respectively (p < 0.001), and the lengths of stay were 14 +/- 1 and 19 +/- 1 days, respectively (p < 0.001). In the setting of infection, chronic renal insufficiency and chronic steroid therapy are associated with suppression of fever and leukocytosis, respectively. Transplantation is an independent predictor of infection in patients presenting without fever or leukocytosis. Leukocytosis, but not fever, may be predictive of hospital mortality in infected surgical patients.

Implications of 2,457 consecutive surgical infections entering year 2000

OBJECTIVE

To assess the demographics and characteristics of infections in surgical patients to define areas that deserve emphasis in surgical education.

SUMMARY BACKGROUND DATA

As a result of evolving technology and diseases, the complexity of diagnosing and treating infections has increased during the past three decades for all patients, including those treated primarily by surgeons. No comprehensive analysis of these conditions in a single surgical cohort has been recently published.

METHODS

The authors conducted a prospective, observational study of all infections occurring on the general and trauma surgery services at a single university hospital during a 3.5-year period.

RESULTS

The authors identified 2,457 infections: 608 community-acquired, 1,053 occurring on the wards, and 796 occurring in the intensive care unit. Although dependent on patient location, the most common sites were abdomen, lung, and wound; the most common isolates were Staphylococcus epidermidis, Staphylococcus aureus, and Candida albicans; and the most commonly used antibiotics were ciprofloxacin, vancomycin, and metronidazole. The overall death rate was 13%, ranging from 5% after community-acquired infections to 25% after infections acquired in the intensive care unit.

CONCLUSIONS

Most infections treated by surgeons are hospital-acquired. Infections with gram-positive cocci and fungi are common, with pulmonary infections becoming more common. Fluoroquinolones have become important therapeutic agents. Depending on the type of practice, these data should be helpful to direct educational efforts so that surgeons can remain knowledgeable and active in the nonsurgical care of their patients.

Impact of a rotating empiric antibiotic schedule on infectious mortality in an intensive care unit

OBJECTIVE

The development of antibiotic-resistant bacteria is associated with significant morbidity and mortality in critically ill patients. We postulated that quarterly rotation of empirical antibiotics could decrease infectious complications from resistant organisms in an intensive care unit (ICU).

DESIGN

Prospective cohort study.

SETTING

An ICU at a university medical center.

SUBJECTS

All patients admitted to the general, transplant, or trauma surgery services who developed pneumonia, peritonitis, or sepsis of unknown origin.

INTERVENTIONS

A 2-yr study consisting of 1 yr of nonprotocol-driven antibiotic use and 1 yr of rotating empirical antibiotic assignment.

MEASUREMENTS AND MAIN RESULTS

Over 100 variables were recorded for each infectious episode, including patient characteristics (e.g., Acute Physiology and Chronic Health Evaluation [APACHE] II score, age, comorbidities), infection characteristics (e.g., site, organism), treatment characteristics (e.g., antibiotic, treatment duration) and outcome measures (e.g., mortality, length of stay, antibiotic cost). Of 1456 consecutive admissions to the ICU, 540 episodes of infection were treated. No differences were noted in age, APACHE II score, race, overall antibiotic utilization or duration of therapy between the 2 yrs of study. Outcome analysis revealed significant reductions in the incidence of antibiotic-resistant Gram-positive coccal infections (7.8 infections/100 admissions vs. 14.6 infections/100 admissions, p <.0001), antibiotic-resistant Gram-negative bacillary infections (2.5 infections/100 admissions vs. 7.7 infections/100 admissions, p <.0001), and mortality associated with infection (2.9 deaths/100 admissions vs. 9.6 deaths/100 admissions, p <.0001) during rotation. Logistic regression identified age (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01-1.06), APACHE II score (OR, 1.06; 95% CI, 1.01-1.13), solid organ transplantation (OR, 9.50; 95% CI, 2.01-52.21), and malignancy (OR, 10.16; 95% CI, 4.11-26.96) as independent predictors of mortality. Antibiotic rotation was an independent predictor of survival (OR 6.27, 95% CI 2.78-14.16).

CONCLUSION

Rotation of empirical antibiotic therapy seems to be a promising method to reduce infectious mortality in an ICU.

Preexposure of murine macrophages to CpG oligonucleotide results in a biphasic tumor necrosis factor alpha response to subsequent lipopolysaccharide challenge

Bacterial DNA and synthetic oligonucleotides containing CpG sequences (CpG-DNA and CpG-ODN) provoke a proinflammatory cytokine response (tumor necrosis factor alpha [TNF-alpha], interleukin-12 [IL-12], and IL-6) and increased mortality in lipopolysaccharide (LPS)-challenged mice via a TNF-alpha-mediated mechanism. It was hypothesized that preexposure of macrophages to CpG-ODN would result in an increased TNF-alpha response to subsequent LPS challenge in vitro. Using the murine macrophage cell line RAW 264.7, we demonstrated both a rapid proinflammatory cytokine response (TNF-alpha) and a delayed inhibitory cytokine response (IL-10) with CpG-ODN. Preexposure of macrophages to CpG-ODN for brief periods (1 to 3 h) augmented TNF-alpha secretion and mRNA accumulation following subsequent LPS challenge (1 microg/ml). However, prolonged preexposure to CpG-ODN (6 to 9 h) resulted in suppression of the TNF-alpha protein and mRNA response to LPS. The addition of anti-IL-10 antibody to CpG-ODN during preexposure resulted in an increase in the LPS-induced TNF-alpha response over that induced by CpG-ODN preexposure alone. Thus, while brief preexposure of macrophages to CpG-ODN augments the proinflammatory cytokine response to subsequent LPS challenge, prolonged preexposure elicits IL-10 production, which inhibits the TNF-alpha response. Although the initial proinflammatory effects of CpG-DNA are well established, the immune response to CpG-DNA may also include autocrine or paracrine feedback mechanisms, leading to a complex interaction of proinflammatory and inhibitory cytokines.

Impact of bloodstream infection on outcomes among infected surgical inpatients

OBJECTIVE

To assess the importance of bloodstream infection (BSI) to outcomes among infected surgical patients.

BACKGROUND

Bloodstream infection complicating infection is thought to connote a more serious condition compared with a primary infection alone. The authors recently reported, however, that BSI does not alter outcomes with central venous catheter colonization in the presence of sepsis. The significance of BSI with other infections has been incompletely evaluated.

METHODS

Data on all episodes of infection among surgical patients were collected prospectively during a 38-month period at a single hospital, then analyzed retrospectively to determine the independent prognostic value of BSI for all infections by logistic regression analysis, and for abdominal infections and pneumonia using matched control groups.

RESULTS

During the study period, 2,076 episodes of infection occurred, including 363 with BSI. Patients with BSI had a greater severity of illness and a greater death rate. After logistic regression, however, BSI did not independently predict death. After matching patients with abdominal infections and pneumonia with BSI to patients without BSI but with a similar site of infection, severity of illness, age, and causative organism, no difference in outcome was seen.

CONCLUSIONS

Bloodstream infection is associated with critical illness and death but appears to be a marker of severe primary disease rather than an independent predictor of outcome.

Extremes of white blood cell count do not independently predict outcome among surgical patients with infection

Historically patients with severely depressed or elevated white blood cell (WBC) counts during infection were felt to have worse outcomes. To test this assumption we prospectively analyzed all infections on the surgical services at the University of Virginia hospital between December 1, 1996 and April 1, 1999. Among 1737 infectious episodes 59 presented with leukopenia (WBC count < or = 3,000 cells/microL) whereas 66 presented with leukemoid responses (WBC count > or = 30,000 cells/microL). Compared with other infected patients leukopenic patients had higher Acute Physiology and Chronic Health Evaluation II (APACHE II) scores (18+/-0.9 vs 12+/-0.2, P < 0.0001) and mortality (23.7% vs 11.4%, P = 0.004). Patients with leukemoid responses also had higher APACHE II scores (21+/-1.0 vs 12+/-0.2, P < 0.0001) and mortality (30.3% vs 11.4%, P < 0.0001). Compared with a control group randomly matched (2:1) by age and APACHE II score, however, there was no significant difference in mortality associated with leukopenia or a leukemoid response. Furthermore logistic regression did not reveal leukopenia or leukemoid responses to be independent predictors of mortality (odds ratio for death with leukopenia = 1.57, 95% confidence interval = 0.63-3.91, P = 0.33; odds ratio for death with leukemoid response = 1.19, 95% confidence interval = 0.70-2.02, P = 0.53). Although very low or very high WBC counts may represent markers of severe illness in infected surgical patients they do not appear to be significant contributors to a worsened outcome.

Characteristics of infectious complications associated with mortality after solid organ transplantation

Infection remains a common source of morbidity and mortality after solid organ transplantation. The purpose of this study was to characterize the continuously changing patterns of post-transplantation infections, analyze early post-transplantation infections, and evaluate characteristics associated with mortality. A secondary analysis was performed on prospectively collected data for all episodes of infection occurring between 10 December 1996 and 28 October 1998 on the surgery services at a university medical center. Post-transplantation infections were compared with those in non-transplantation patients randomly matched by severity of illness. Further analysis was performed on post-transplantation infections occurring during the admission of transplantation compared with those in subsequent admissions. To evaluate factors associated with mortality, episodes occurring in survivors and non-survivors were compared. The results demonstrated that infections in transplantation recipients (n = 303) were associated with a younger age and had significantly lower white blood cell counts (WBC) compared with non-transplantation patients. There was no difference in mortality (15.5 vs. 16.5%, p = 0.74). Post-transplantation infectious complications during the initial hospitalization (n = 105) occurred at 38+/-6 compared with 695+/-66 d (p<0.0001) after transplantation and were associated with a longer length of stay (LOS) and increased mortality (30.5 vs. 7.6%, p<0.0001) compared with those occurring in subsequent admissions (n = 198). Although multiple characteristics of post-transplantation infections were associated with mortality, only the Acute Physiology and Chronic Health Evaluation (APACHE) II score was an independent predictor of mortality. Post-transplantation infections remain a significant source of morbidity and mortality. The leukocyte response to infection was suppressed in the transplantation population. Post-transplantation infections which occur during the admission for transplantation have a markedly increased mortality.

Bacteremia associated with central venous catheter infection is not an independent predictor of outcomes

BACKGROUND

Infection is the leading complication of central venous catheters. In the setting of suspected line infection, the CDC recognizes only catheter-related bloodstream infection but not catheter infection without bacteremia, which is designated "colonization." To evaluate the hypothesis that catheter-related bloodstream infection has worse outcomes than catheter infection without bacteremia, we compared demographics, clinical data, and outcomes.

STUDY DESIGN

Analysis of catheter infections was performed on data collected prospectively for all episodes of infection occurring from December 1996 to September 1999 on the surgical services at a university hospital. Catheter tips were cultured only when infection was suspected. Catheter infection without bacteremia was defined as systemic evidence of infection, the presence of at least 15 colony-forming units on the catheter tip by a semiquantitative technique, and absence of bloodstream infection with the same organism as the catheter. Catheter-related bloodstream infection required the presence of bacteremia with the same organism as the catheter tip.

RESULTS

The 59 patients with catheter-related bloodstream infection had more coexistent infections than the 91 patients with catheter infection without bacteremia (2.9+/-0.1 versus 1.7+/-0.1; p=0.0001), most commonly pneumonia (37.3% versus 16.5%, p = 0.004) and urinary tract infections (28.8% versus 8.8%, p = 0.001). Catheter-related bloodstream infection was associated with an increased proportion of gram-negative organisms compared with catheter infections without bacteremia (29.5% versus 16.9%, p = 0.04) and a trend toward fewer gram-positive organisms (61.5% versus 73.7%, p = 0.07). There were no differences in APACHE II score, WBC, length of hospital stay, time from admission to fever, time from fever to treatment, normalization of WBC, days of antibiotics, defervescence, gender, presence of comorbidities, occurrence of colonization while in an ICU, or mortality rate (18.6% with bacteremia, 24.2% without; p = 0.42).

CONCLUSIONS

The presence of bloodstream infection in addition to catheter infection does not appear to alter outcomes. The definition of catheter infection perhaps should be extended to include catheter infections without bloodstream infection in the presence of systemic illness without another source.

Contribution of Escherichia coli alpha-hemolysin to bacterial virulence and to intraperitoneal alterations in peritonitis

Alpha-hemolysin (Hly) is a common exotoxin produced by Escherichia coli that enhances virulence in a number of clinical infections. The addition of hemolysin production to laboratory bacterial strains is known to increase the lethality of E. coli peritonitis. However, the mechanisms involved have not been determined and the contribution of hemolysin to the alterations in the host intraperitoneal environment and the leukocyte response is not known. Utilizing a rat peritonitis model, we show that wild-type hemolytic E. coli strains have a significant competitive advantage over nonhemolytic strains within the peritoneum. To examine the specific contribution of Hly to E. coli-induced virulence and alterations within the peritoneum, a mixed peritonitis model of E. coli, Bacteroides fragilis, and sterile fecal adjuvant was used. Three transformed E. coli strains were utilized: one strongly secretes active hemolysin (WAF 270), a second secretes active hemolysin but a reduced amount (WAF 260), and the third does not produce hemolysin (WAF 108). After an equal inoculum of each of the three strains, WAF 270 produced a markedly increased lethality and an increased recovery of both E. coli and B. fragilis from the host relative to the other strains. Changes in the intraperitoneal pH, degree of erythrocyte lysis, and recruitment and viability of leukocytes within the peritoneum following the induction of peritonitis differed significantly between the strongly hemolytic and nonhemolytic strains. Induction of peritonitis with WAF 270 caused a pronounced decrease in intraperitoneal pH, lysis of most of the intraperitoneal erythrocytes, and a marked decrease in recoverable viable leukocytes compared to WAF 108. Thus, hemolysin production by E. coli within the peritoneum may alter not only the host's ability to control the hemolytic strain itself but also other organisms.

Gender-dependent differences in outcome after the treatment of infection in hospitalized patients

CONTEXT

While it is established that management strategies and outcomes differ by gender for many diseases, its effect on infection has not been adequately studied.

OBJECTIVE

To investigate the role of gender among hospitalized patients treated for infection.

DESIGN

Observational cohort study conducted during a 26-month period from December 1996 through January 1999.

SETTING

University-affiliated hospital.

PARTICIPANTS

A total of 892 patients in the surgical units of the hospital with 1470 consecutive infectious episodes (782 in men and 688 in women).

MAIN OUTCOME MEASURES

Mortality during hospitalization by gender for infection episodes overall and for specific infectious sites, including lung, peritoneum, bloodstream, catheter, urine, surgical site, and skin/soft tissue.

RESULTS

Among all infections, there was no significant difference in mortality based on gender (men, 11.1% vs women, 14.2%; P = .07). After logistic regression analysis, factors independently associated with mortality included higher APACHE (Acute Physiology and Chronic Health Evaluation) II score, older age, malignancy, blood transfusion, and diagnosis of infection more than 7 days after admission, but not gender (female odds ratio [OR] for death, 1.32; 95% confidence interval [CI], 0.90-1.94; P = .16). Mortality was higher in women for lung (men, 18% vs women, 34%; P = .002) and soft tissue (men, 2% vs women, 10%; P < or = .05) infection; for other infectious sites, mortality did not differ by gender. Factors associated with mortality due to pneumonia by logistic regression included higher APACHE II score, malignancy, diabetes mellitus, diagnosis of infection more than 7 days after admission, older age, transplantation, and female gender (OR for death, 2.25; 95% CI, 1.17-4.32; P = .02).

CONCLUSIONS

Although gender may not be predictive of mortality among all infections, women appear to be at increased risk for death from hospital-acquired pneumonia, even after controlling for other comorbidities.

Analysis of aminoglycosides in the treatment of gram-negative infections in surgical patients

HYPOTHESIS

Antibiotic regimens containing aminoglycosides result in a similar outcome compared with non-aminoglycoside regimens in the treatment of gram-negative infections in surgical patients.

DESIGN

An inception cohort study of hospitalized surgical patients from December 1, 1996, through September 30, 1998. Patients were observed from the time of diagnosis of infection to discharge.

SETTING

University hospital.

PATIENTS

Two hundred fifty-eight consecutive gram-negative infections occurring in general surgical and trauma patients and patients undergoing transplantation. Sixty-six patients received aminoglycosides as a component of their treatment regimen, whereas 192 received other agents.

RESULTS

Patients treated with aminoglycosides were younger (mean +/- SEM age, 48+/-2 vs 53+/-1 years; P = .04 by univariate analysis) and had a similar APACHE II (Acute Physiology and Chronic Health Evaluation II) score (mean +/- SEM, 17+/-1 vs 15+/-1; P = .10), yet had a significantly higher mortality vs patients treated with other agents (29% vs 14%; P = .02). A larger proportion of patients requiring hemodialysis were treated with aminoglycosides (33% vs 13%; P = .001). Although there was no difference in the sites of infection between groups, surgical patients with gram-negative pneumonia had a higher mortality when treated with aminoglycosides (37% vs 18%; P = .04), despite similar APACHE II scores (mean +/- SEM, 20+/-1 vs 18+/-1; P = .40).

CONCLUSIONS

Despite a younger age and similar severity of illness, patients with gram-negative infections treated with aminoglycosides were associated with a higher mortality rate, although this may be related to selection bias in the use of aminoglycoside agents. The mortality rate associated with gram-negative pneumonia was also higher in patients treated with aminoglycosides, despite a similar severity of illness. Future randomized studies are necessary to reanalyze the role of aminoglycosides in treating surgical patients with gram-negative infections, particularly pneumonia.

Waiting for microbiologic data to direct therapy against nosocomial infections in febrile surgical patients: are outcomes worsened?

HYPOTHESIS

Allowing adequate time for laboratory and culture results before initial treatment may be associated with a worse outcome in nosocomial infections.

DESIGN

Cohort study of all episodes of nosocomial infection from December 10, 1996, to October 28, 1998.

SETTING

Surgical services at a university hospital.

PATIENTS AND METHODS

In surgical patients presenting with fever, 372 episodes of nosocomial infection were evaluated. Nosocomial infections were divided by time from fever to intervention (< or =12, 13-24, and >24 hours). These groups were subdivided by Acute Physiology and Chronic Health Evaluation II (APACHE II) scores into low (< or =10 [n = 114]), moderate (11-20 [n = 169]), and high severity of illness (>20 [n = 89]). Pneumonia and bloodstream infections were divided by APACHE II scores into low (< or =15 [n = 55 and n = 56, respectively]) or high severity of illness (>15 [n = 84 and n = 77, respectively]).

MAIN OUTCOME MEASURES

Mortality, length of stay.

RESULTS

No difference in outcome was seen between different time intervals from fever to intervention for nosocomial infections in patients with APACHE II scores of no more than 10. Patients treated more than 24 hours after fever were significantly younger than those treated at no more than 12 and 13 to 24 hours with APACHE II scores of 11 to 20 (P<.05) and more than 20 (P<.05). Mortality and length of stay for patients treated at later time intervals were comparable with those of patients treated earlier with similar APACHE II scores. There was no difference in outcome for patients with pneumonia or bloodstream infection.

CONCLUSIONS

Episodes of infection in which treatment was withheld until initial microbiologic data were available (24 hours) did not have worse outcomes compared with those treated earlier. Waiting for laboratory and culture results to direct antibiotic therapy for nosocomial infections does not appear harmful and may be potentially beneficial.

Prediction of poorer prognosis by infection with antibiotic-resistant gram-positive cocci than by infection with antibiotic-sensitive strains

HYPOTHESES

Surgical patients with antibiotic-resistant gram-positive coccal (GPC) infections have a poorer prognosis than those with antibiotic-sensitive GPC infections, and colonization with resistant GPC predisposes to the development of resistant GPC infections.

DESIGN

All infections among surgical patients from December 1, 1996, to December 1, 1998, were followed up prospectively. Patients with antibiotic-sensitive and antibiotic-resistant GPC infections were compared. Cohorts were also subdivided on the basis of GPC species, colonization status, and immunosuppression.

SETTING

The surgical wards and intensive care units of a tertiary care, university hospital.

MAIN OUTCOME MEASURES

In-hospital mortality, inhospital mortality during antibiotic therapy, length of stay, and length of stay from the time of initiation of antibiotics to discharge.

RESULTS

Antibiotic-resistant GPC infection compared ki4th antibiotic-sensitive GPC infection was associated with a higher mortality and previous colonization rate (25.8% and 31.0% vs 17.6% and 8.8%, respectively; P = .04 and P<.001, respectively) and a markedly longer length of stay (55.0 +/- 3.3 vs 31.0 +/- 2.0 days; P<.001). Length of stay and treatment to discharge times were longer after resistant Staphylococcus aureus infections than after resistant Staphylococcus epidermidis infections. The mortality and length of stay of patients with gentamicin-resistant or vancomycin-resistant enterococcal infections were equivalently higher than those with antibiotic-sensitive enterococcal infections. Transplant recipients with resistant enterococcal infection had the highest mortality (41.9%).

CONCLUSIONS

Surgical patients who develop antibiotic-resistant GPC infections have a significantly higher mortality rate, longer length of stay, and longer treatment to discharge time than patients with antibiotic-sensitive GPC infections. Colonization with resistant GPC predisposes to resistant GPC infection. Gentamicin-resistant enterococcus appears to be as virulent as vancomycin-resistant enterococcus.

Trends in nosocomial pneumonia in surgical patients as we approach the 21st century: a prospective analysis

To compare outcome and prognostic factors of pneumonia in surgical patients, we prospectively studied all episodes of nosocomial infection at all sites in 1997 on the surgical services at a single hospital. Pneumonia accounted for 74 of 287 episodes of infection. The crude mortality for pneumonia was 31.1 versus 12.2 per cent for all other infections (P < 0.001). Pneumonia patients had a higher severity of illness compared with those with infections at other sites (18.7 +/- 0.8 vs 14.0 +/- 0.5; P < 0.001). Crude mortality remained higher in pneumonia patients when compared with an infected control group matched for severity of illness and age (31% vs 15%; P = 0.02). Staphylococcus aureus (15%) was the most common isolate, followed by Pseudomonas aeruginosa (9%). Resistant Gram-positive cocci accounted for 7 per cent of all isolates but was associated with a 60 per cent mortality vs 28 per cent with other organisms (not significant; P = 0.1). The Acute Physiology and Chronic Health Evaluation (APACHE) II score for patients with resistant Gram-positive cocci was 22 +/- 1 versus 18 +/- 1 with other organisms (P = 0.03). Nonsurvivors of pneumonia were older (58 +/- 2 vs 51 +/- 3; P = 0.03), had a higher APACHE II score (23 +/- 1 vs 17 +/-1; P < 0.001), and were diagnosed later in their hospital course (18 +/- 4 days vs 11 +/- 1; P = 0.05) compared with survivors. Pneumonia-associated mortality in surgical patients remains high compared with other infections even when correcting for differences in severity of illness. Although resistant Gram-positive cocci appear to be increasing in frequency, they may represent markers of severe illness rather than true pathogens. Increasing age, severity of illness, and length of stay before diagnosis were all associated with a worse prognosis.

Impact of solid organ transplantation and immunosuppression on fever, leukocytosis, and physiologic response during bacterial and fungal infections

Immunosuppressed solid organ transplant patients may exhibit a blunted response to infection compared to non-transplant patients. To test this hypothesis, we prospectively identified all episodes of bacterial and fungal infection on the in-patient abdominal organ transplant service in our hospital, in 1997, and compared them to infected general surgery and trauma admissions treated simultaneously on the same wards. Eighty-two infections occurred in transplant patients versus 463 in non-transplant patients. Transplant patients demonstrated an overall greater physiologic response [Acute Physiology and Chronic Health Evaluation (APACHE II) and Acute Physiology Scores (APS) at the time of infection of 17.0+/-0.7 and 10.3+/-0.6, respectively, vs. 12.2+/-0.4 and 8.0+/-0.3 for non-transplant patients, p < 0.003], with a similar maximum temperature (38.0+/-0.1 vs. 38.2+/-0.1 degrees C, p = 0.2) and white blood cell (WBC) count (12.1+/-1.0 vs. 13.9+/-0.4 k/mL, p = 0.08). Upon further analysis of subgroups, patients receiving mycophenolate or azathioprine had significantly lower maximum temperatures (37.9+/-0.2 degrees C) and WBC counts (11.0+/-0.9 k/mL) when compared to non-transplant patients, while steroids appeared to have little effect on the systemic inflammatory response. Overall mortality was similar between groups. In general, solid organ transplant recipients exhibit a physiologic response to bacterial or fungal infection (as measured by the APS) at least as great as that seen in non-transplant surgical patients, although mycophenolate and azathioprine appear to slightly depress the ability to respond with fever and leukocytosis. None of these differences appeared to affect overall mortality.

Clinical characteristics and antibiotic utilization in surgical patients with Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) remains a significant problem in surgical patients. To address this, we prospectively studied all episodes of treated CDAD in surgical inpatients at the University of Virginia hospital from December 1996 through March 1998. CDAD accounted for 3.2 per cent (32) of 1000 total infections. Compared with a randomly selected control group with other nosocomial infections, patients with CDAD had a longer period from the time of admission to diagnosis of infection (19 +/- 4 versus 9 +/- 1; P = 0.01), were more likely to be female (66% versus 37%; P = 0.009), and had a higher overall crude mortality (31% versus 11%; P = 0.01), although there were no deaths directly attributable to CDAD. Ciprofloxacin (19%) and cefoxitin (16%) were the most common individual antibiotics prescribed before the diagnosis of CDAD. The average time from completion of antibiotic therapy to diagnosis of CDAD was 7 +/- 2 days (range, 0-58). Sixteen per cent (5 of 32) developed CDAD after administration of prophylactic perioperative antibiotics only. The high crude mortality rate associated with CDAD suggests that this may be a significant predictor of poor outcome among infected surgical patients. Antibiotics used commonly but not classically associated with CDAD frequently precipitate this infection. Finally, the use of prophylactic antibiotics is not without risk, as demonstrated by the significant percentage of CDAD occurring after routine administration of these agents.

Hemolytically active (acylated) alpha-hemolysin elicits interleukin-1beta (IL-1beta) but augments the lethality of Escherichia coli by an IL-1- and tumor necrosis factor-independent mechanism

Many pathogenic Escherichia coli produce the toxin alpha-hemolysin (Hly), and lipopolysaccharide (LPS), interleukin-1 (IL-1), and tumor necrosis factor (TNF) have all been recognized as important effector molecules during infections by gram-negative organisms. Despite the characterization of many in vitro effects of hemolysin, no direct relationship has been established between hemolysin, LPS, proinflammatory cytokine production, and E. coli-induced mortality. Previously, we have shown in vivo that hemolysin elicits a distinct IL-1alpha spike by 4 h into a lethal hemolytic E. coli infection. Using three transformed E. coli strains, WAF108, WAF270, and WAH540 (which produce no Hly [Hlynull], acylated Hly [Hlyactive], or nonacylated Hly [Hlyinactive], respectively), we sought to determine the specific roles of hemolysin acylation, LPS, IL-1, and TNF in mediating the lethality of E. coli infection in mice. WAF270 was 100% lethal in BALB/c, C3H/HeJ, and C57BL/6 mice; in mice pretreated with antibody to the type 1 IL-1 receptor; in type 1 IL-1 receptor-deficient mice; and in dual (type 1 IL-1 receptor-type 1 TNF receptor)-deficient mice at doses which were nonlethal (0%) with both WAF108 and WAH540. At lethal doses, WAF270 killed by 6 +/- 2.3 h while WAF108 and WAH540 killed at 36 +/- 9.4 and 36 +/- 13.8 h, respectively. These differences in mortality were not due to IL-1 or TNF release, and the enhanced expression of LPS, which corresponded to Hly expression, was not likely the primary factor causing mortality. We demonstrate that bacterial fatty acid acylation of hemolysin is required in order for it to elicit IL-1 release by monocytes and to confer its virulence on E. coli.

Bacterially preexposed T cells impair bacterial elimination by non-Th1/Th2 cell mechanisms in a model of intra-abdominal infection

BACKGROUND

Escherichia coli preexposure in mice results in impaired elimination of subsequent intra-abdominal infections by a CD+4 T cell-dependent process. Certain gram-negative infections have been shown to induce T-helper-(Th)2 type CD4+ T-cell differentiation, which correlates with impaired elimination of infection and death. We hypothesized that E coli preexposure impairs subsequent bacterial elimination as a consequence of Th2 differentiation and that interleukin-12 (IL-12) treatment could reverse this differentiation and minimize the effects of E coli preexposure.

METHODS

After preexposure to E coli or other species, BALB/c mice or interferon-gamma (INF-gamma)-deficient mice, treated with or without IL-12, were given a standard intra-abdominal infection (E coli, Bacteroides fragilis, and adjuvant). Cohorts were killed for abscess quantification, in vitro T-cell proliferative responsiveness, and cytokine secretory profiles. Splenic lymphocytes preexposed in vivo to other types of bacteria were transferred to naive mice before intra-abdominal infection to determine whether preexposure, eliciting the lymphocyte-dependent response, was species specific.

RESULTS

E coli preexposure alone caused no Th1 or Th2 shift; increased the proliferative responses of T cells; and, in combination with IL-12 therapy, caused markedly decreased IL-2 and IL-4 responses and an increased IFN-gamma response. IL-12 therapy did not change the response to intra-abdominal infection despite its ability to cause marked Th1 polarization. IFN-gamma-deficient mice responded to E coli preexposure no differently than did wild-type mice. Transfer of lymphocytes preexposed to Pseudomonas aeruginosa, Klebsiella pneumoniae, and hemolytic E coli but not other types of nosocomial pathogens caused the development of more abscesses just as transfer of E coli preexposed lymphocytes had.

CONCLUSIONS

CD4+ T cells responsive to E coli preexposure regulate subsequent intra-abdominal abscess formation by a mechanism not explained by the Th1/Th2 paradigm. Preexposure to hemolytic E coli and other Enterobacteriaceae alters responses to intra-abdominal infection.

Emerging evidence of selection of fluconazole-tolerant fungi in surgical intensive care units

OBJECTIVE

To determine whether increased use of fluconazole has coincided with a shift in the relative proportion of fluconazole-tolerant species isolated from critically ill surgical patients in 2 university hospitals.

DESIGN

Microbiological data and fluconazole administration frequencies were reviewed among patients treated in the surgical intensive care units (SICUs) from January 1, 1990, through December 31, 1995.

SETTING

The SICUs of the University of Virginia Medical Center, Charlottesville, and the Hospital of the University of Pennsylvania, Philadelphia.

MAIN OUTCOME MEASURES

The number and species types of all fungal isolates and the number of patients treated with fluconazole for each of the 6 years were determined.

RESULTS

A sharp increase in the use of fluconazole among critically ill surgical patients has occurred at both medical centers from 1990-1995. The culture results of most patients treated with fluconazole were negative for fungi (73% and 63% at the University of Virginia Medical Center and the Hospital of the University of Pennsylvania, respectively); there was a greater tendency to use fluconazole at the University of Virginia Medical Center compared with the Hospital of the University of Pennsylvania (2.2% vs 1.8% of patients admitted to the SICU received it, respectively; P = .007). There was a significant increase in the proportion of Candida glabrata isolated at the University of Virginia Medical Center (P < .01) from 1990-1995, but a similar change was not detectable at the Hospital of the University of Pennsylvania.

CONCLUSIONS

These data justify concern that the increased use of fluconazole in SICUs may be promoting a shift in the fungal flora that cause nosocomial infections toward species that are more difficult to treat. Prospective studies about the use of fluconazole for prophylaxis and empirical therapy among SICU patients are warranted before its widespread use in these settings continues.

The current role of U tubes for benign and malignant biliary obstruction

OBJECTIVE

The recent experience with U tubes at Rush-Presbyterian-St. Lukes Medical Center was reviewed in order to assess their current role in hepatobiliary surgery.

SUMMARY BACKGROUND DATA

Transhepatic intubation by a variety of methods has been used routinely for biliary decompression and inhibition of anastomotic stricture since the 1960s. U tubes were popularized in the early 1970s. However, little has been written about their use and efficacy in recent years. Because of the apparent benefits associated with the use of U tubes versus other stenting techniques, the authors performed this study.

METHODS

The hospital and office charts of all patients who had U tubes placed between 1980 and 1992 were reviewed retrospectively. Between 1980 and 1992, U tubes were placed intraoperatively in 54 patients for biliary decompression and/or stenting. Twelve patients were operated on for benign causes of obstruction. Forty-two patients with malignant tumors underwent surgery for U tube placement in conjunction with or without tumor resection and anastomotic bypass.

RESULTS

There was a 0% operative mortality rate in the benign group. In six patients, the U tube played a major role in the long-term management of their disease processes. None of these patients has had restricture since removal of the tube. In the malignant group, the 30-day operative mortality rate was 12%. After 3 months, marked clinical improvement and complete biliary decompression were achieved, with mean bilirubin levels dropping from 14.0 mg/dL to 1.3 mg/dL. No patients in the malignant group required reoperation for recurrent biliary obstruction after U tube placement.

CONCLUSIONS

The use of U tubes is advocated for biliary decompression and/or anastomotic stenting in patients with benign stricture or resectable malignancy and in patients with nonresectable, malignant biliary obstruction for adequate palliation of intractable jaundice.