Risk of infection after penetrating abdominal trauma

Surgical site infections: epidemiology and prevention

BACKGROUND

The overall incidence of surgical site infection (SSI) has been estimated to be 2.8% in the United States, according to the U.S. Centers for Disease Control and Prevention, although the data may underrepresent the true incidence of such infections owing to inherent problems with voluntary self-reporting by surgeons of infections that occur in the ambulatory surgical setting. This review analyzes the reasons why patients are at risk and what can be done to minimize the risk.

METHODS

Review of the pertinent English-language literature.

RESULTS

Factors that contribute to the development of SSI include those that arise from the patient's health status, those that relate to the physical environment where surgical care is provided, and those that result from clinical interventions that increase the patient's inherent risk. Careful patient selection and preparation, including the judicious use of antibiotic prophylaxis, can decrease the overall risk of infection, especially following clean-contaminated and contaminated operations. However, antibiotics are not a substitute for attention to detail and meticulous surgical technique, and can increase the risk of nosocomial infection following injudicious use (that is, overuse).

CONCLUSION

Most SSIs can be attributed to risk factors inherent to the patient, rather than to inherently flawed surgical care. Nonetheless, the surgeon can minimize the risk to the patient through careful patient selection and preparation, attention to technical details and awareness of the operating room environment, and the selective use of short-duration, narrow-spectrum antibiotic prophylaxis for appropriate patients.

Microbiology and management of intra-abdominal infections in children

The present review describes the microbiology, diagnosis, and management of intra-abdominal infections in children. Infection generally occurs due to the entry of enteric micro-organisms into the peritoneal cavity through a defect in the wall of the intestine or other viscus as a result of obstruction, infarction, or direct trauma. Mixed aerobic and anaerobic flora can be recovered from the peritoneal cavity of these patients. The predominant aerobic isolates are Escherichia coli, and enterococci; the main anaerobic bacteria are Bacteroides fragilis group, Peptostreptococcus spp. and Clostridium spp. The treatment of abdominal infection includes surgical correction and drainage, and administration of antimicrobials that are effective against both aerobic and anaerobic micro-organisms.

Characteristics of prophylactic antibiotic strategies after penetrating abdominal trauma at a level I urban trauma center: a comparison with the East guidelines

BACKGROUND

Antibiotic prophylaxis, along with surgical intervention, is a key component in reducing infection in patients after penetrating abdominal trauma (PAT). Recent guidelines from the Eastern Association for the Surgery of Trauma (EAST) recommend that prophylaxis for < or = 24 hours is adequate for most patients. We compared antibiotic prophylaxis practices after PAT at our institution with EAST guidelines, quantified the incidence of infection, and identified risk factors for infection.

METHODS

This study was a retrospective review of patients with PAT requiring a therapeutic laparotomy between July 1998 and January 2001.

RESULTS

Antibiotic prophylaxis met EAST guidelines criteria in 21 of 97 patients (22%). There was a trend toward higher infection rates (18 of 76 vs. 3 of 21; = 0.273) when prophylaxis exceeded EAST recommendations. Multivariate analysis revealed blood transfusions to be the only predictor of infection (odds ratio, 6.9; 95% confidence interval, 2.42-19.95).

CONCLUSION

Despite prophylactic antibiotic use often exceeding EAST criteria, many patients still developed infection. Blood transfusion was the only significant risk factor for infection.

Impact of allogenic packed red blood cell transfusion on nosocomial infection rates in the critically ill patient

OBJECTIVE

To determine whether critically ill patients who receive allogenic packed red blood cell transfusions are at increased risk of developing nosocomial infections during hospitalization.

DESIGN

Retrospective database study utilizing Project IMPACT.

SETTING

A 40-bed medical-surgical-trauma intensive care unit in an 825-bed tertiary referral teaching hospital.

PATIENTS

One thousand seven hundred and seventeen patients admitted to the medical-surgical-trauma intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Data were collected by using the Project IMPACT database. Nosocomial infection rates were compared among three groups: the entire cohort, the transfusion group, and the nontransfusion group. We determined the nosocomial infection rates in these groups while adjusting for probability of survival by using Mortality Prediction Model (MPM-0) scores, age, gender, and number of units of packed red blood cells transfused. The average number of units transfused per patient was 4.0. The nosocomial infection rate for the entire cohort was 5.94%. The nosocomial infection rates for the transfusion group (n = 416) and the nontransfusion group (n = 1301) were 15.38% and 2.92%, respectively (p <.005 chi-square). Transfusion of packed red blood cells was related to the occurrence of nosocomial infection, and there was a dose-response pattern (the more units of packed red blood cells transfused, the greater the chance of nosocomial infection; p< 0.0001 chi-square). The transfusion group was six times more likely to develop nosocomial infection compared with the nontransfusion group. In addition, for each unit of packed red blood cells transfused, the odds of developing nosocomial infection were increased by a factor of 1.5. A subgroup analysis of nosocomial infection rates adjusted for probability of survival by using MPM-0 scores showed nosocomial infection to occur at consistently higher rates in transfused patients vs. nontransfused patients. A second subgroup analysis adjusted for patient age showed a statistically significant increase in rates of nosocomial infection for transfused patients regardless of age.

CONCLUSIONS

Transfusion of packed red blood cells is associated with nosocomial infection. This association continues to exist when adjusted for probability of survival and age. In addition, mortality rates and length of intensive care unit and hospital stay are significantly increased in transfused patients.

Infection control: avoiding the inevitable

Infection, while a major cause of morbidity, should not be considered an inevitable consequence of injury. Good aseptic technique, compulsive attention to detail, and thorough understanding of the points addressed in the following list of critical points are the best guarantee that infection will not add avoidable morbidity to misfortune. Critical points regarding infectious problems in care of the injured child: 1. Polymicrobial infection is the rule with 50% of isolates being mixed aerobic and anaerobic bacteria. 2. It is a misnomer to consider antibiotic use in a pediatric trauma victim as prophylactic. Antimicrobials used in this setting are best considered adjunctive. 3. The major indication for anti-infective therapy in pediatric trauma is an injury with a high probability of infection. 4. Antibiotics do not sterilize the wound or body cavity; they limit bacterial proliferation, thereby supplementing effective immune control. 5. Available studies suggest that 24 hours is as efficacious as a longer treatment duration in a purely adjunctive mode. 6. In bites inflicted by dogs and cats, Pasturella species are frequent. 7. Human bites may result in infection by Eikenella corrodens. 8. Based on this bacteriology, adjunctive intravenous ampicillin sulbactam or oral amoxicillin clavulanate are recommended for human and animal bites. 9. Tetanus prophylaxis is indicated in all significant soft tissue injuries. 10. Risk of osteomyelitis correlates directly with the extent of the associated soft tissue injury and vascular compromise. 11. The majority of infectious complications in the injured child are not a consequence of the injury itself, but rather in the treatment thereof. 12. In the injured child the most common nosocomial infection is lower respiratory followed by primary blood stream and the urinary tract. 13. The management of nosocomial pneumonia in the injured child is based on the time of diagnoses. Early evidence of pulmonary infection requires treatment with a third generation cephalosporin with or without an antistaphylococcal penicillin. Late pneumonia is treated with an aminoglycoside with or without an antipseudomonal added. 14. Catheter related infection is, in the injured child, overwhelmingly gram positive with coagulase negative staphlococcal species accounting for 30-60% of isolates. Staphlococcus aureus is responsible for an additional 15-20%. 15. The role of antibiotics in the prevention of catheter related meningitis is controversial. Recent adult studies suggest no advantage to their routine use. If utilized, they should only be employed prophylactically and not continued throughout the monitoring period. 16. Lack of response to treatment of sepsis may represent an inappropriate antimicrobial agent, improper dosage, inability to achieve adequate levels at the site of infection. (eg, CSF) fungal pathogen, and/or ongoing contamination or undrained purulent focus.

The effect of universal leukodepletion of packed red blood cells on postoperative infections in high-risk patients undergoing abdominal aortic surgery

We evaluated, by using a before-and-after study, the influence of leukoreduction by filtration on postoperative infections and adverse outcomes in patients undergoing elective major aortic surgery. From January 1995 to October 2000, all patients who underwent elective abdominal aortic surgery were included in the analysis. Before the introduction of systematic leukodepletion of packed red blood cells (RBCs), on April 1, 1998, 192 patients received standard or buffy-coat-depleted packed RBCs. Then, 195 patients were transfused with exclusively filtered leukodepleted packed RBCs. No major significant difference was observed between the groups of patients with regard to preoperative cardiac and pulmonary status, anesthetic and surgical techniques, or transfusion policy. No significant difference in mortality was observed between the two groups. The incidence of postoperative infections was 31% (95% confidence interval, 25%--38%) in the Control group versus 27% (95% confidence interval, 21%--33%) in the Leukodepleted group; severe infectious complications and pneumonia were not significantly different between the two groups of patients. Cardiovascular and respiratory outcomes were not significantly different between the groups. Data from this study suggest that the effect of using leukodepleted RBC on postoperative infections is not of obvious importance.

IMPLICATIONS

We evaluated the influence of leukocyte reduction by filtration of packed red blood cells (RBC) on postoperative infections and adverse outcomes in patients undergoing elective major aortic surgery by comparing two epochs with and without filtration. Data from this study suggest that the effect of using filtered RBC on postoperative infections is not of obvious importance.

The prognostic importance of trauma scoring systems for morbidity in children with penetrating abdominal wounds: 17 years of experience

BACKGROUND/PURPOSE

Risk factors that may independently predict morbidity in children with penetrating abdominal wounds (PAW) have not been elucidated fully. The aim of this study was to identify not only correlated risk factors for morbidity in children with PAW, but also to evaluate the independent predictive value of 3 different trauma scoring systems: the Injury Severity Score (ISS), the Penetrating Abdominal Trauma Index (PATI), and the Pediatric Trauma Score (PTS).

METHODS

Between January 1983 and November 2000, 119 children (99 boys, 20 girls) presenting with PAW were reevaluated by an analysis of the relationship between overall morbidity and potential risk factors.

RESULTS

Wounds were caused by firearm trauma in 85 children and stabbing in 34. Univariate analysis found that age greater than 10 years, trauma mechanism, number of intraabdominal organs injured (NOI) greater than 2, presence of penetrating injury, and ISS and PATI score were associated with greater than 3-fold increased incidence of morbidity (P <.05). The relative risk of a postoperative septic complication was higher than 2 for the following risk factors: age greater than 10 years, shotgun injury, number of organs injured greater than 2, presence of colon injury, ISS greater than 15, and PATI score greater than 15. Multivariate analysis showed that only ISS (P =.02), and PATI score (P =.03) were independently significant in predicting morbidity.

CONCLUSION

ISS and PATI score were the most important indicators found to be independently associated with morbidity.

Risk factors in surgery

Improved surgical and anesthetic techniques and postoperative care have not significantly changed wound infection rates over the last 30 years. Many risk factors, related both to the host and to the surgical practice, have been identified in different studies. Control of nosocomial infections has become more challenging recently, due to a widespread bacterial resistance to antibiotics and to more frequent surgical indications in elderly patients at increased risk. A change in the microbiology of postoperative infections has also been noticed, characterized by a greater incidence of infections caused by methicillin-resistant Staphylococcus aureus, by polymicrobic flora and by fungi. This paper reviews the most important risk factors encountered in general surgery, that we observed during a 6-year prospective study of wound infection carried out in our Department of Surgery at the University of Insubria in Varese. Furthermore, the epidemiologic data on wound infections recorded in 4,002 patients undergoing general surgical procedures (mostly gastrointestinal operations), are presented and discussed.

Irreversible Shock Is Not Irreversible: A New Model of Massive Hemorrhage and Resuscitation

BACKGROUND

Existing shock models do not address the patient with massive hemorrhage (> 1 blood volume). Such patients often die from irreversible shock. This model simulates the clinical scenario of massive hemorrhage and resuscitation (MHR) to determine if irreversible shock can be reversed.

METHODS

Lewis rats were bled at a rate of 1 estimated blood volume (EBV) per hour for 2 hours with simultaneous infusion of resuscitation mixture (RM) consisting of red blood cells and crystalloid. Blood pressure was maintained at a mean arterial pressure (MAP) of 50 mm Hg during the 2 hours of hemorrhage. Hemorrhage was stopped and resuscitation continued for 1 hour until 6, 8, or 10 x EBV of RM was infused. Control animals were subjected to a traditional fixed pressure hemorrhage to MAP of 50 mm Hg for 2 hours followed by resuscitation to MAP > 90 mm Hg for 1 hour with crystalloid alone. Two-week survival was compared using a chi2 test.

RESULTS

Control animals (n = 13) were hemorrhaged 48% +/- 5% of EBV and had a mortality rate of 23%. MHR animals had severity and duration of hypotension identical to that of controls but were hemorrhaged 214% +/- 8% of EBV. Despite receiving 390 mL/kg of RM and a final hematocrit of 37%, 14 of 15 animals resuscitated with 6 x EBV died from "irreversible" shock (mortality, 93%; p < 0.001 vs. controls). When very large volumes of resuscitation were used, survival rates improved significantly. The 10 x EBV group received 120% of lost red blood cells and 530 mL/kg of crystalloid and had 64% survival at 2 weeks (p < 0.01 vs. 6 x EBV group).

CONCLUSION

This MHR model is much more lethal than a traditional severe hemorrhage model and reproduces the clinical picture of irreversible shock. This irreversible shock can be reversed with very large volumes of resuscitation.

Increased apoptosis in lamina propria B cells during polymicrobial sepsis is FasL but not endotoxin mediated

Recent studies from our laboratory demonstrated that mucosal lymphoid tissue such as Peyer's patch cells and lamina propria (LP) B lymphocytes from mice shows evidence of increased apoptosis after sepsis that is associated with localized inflammation/activation. The mechanism for this is poorly understood. Endotoxin as well as Fas/Fas ligand (FasL) have been shown to augment lymphocyte apoptosis; however, their contribution to the increase of apoptosis in LP B-cells during sepsis is not known. To study this, sepsis was induced by cecal ligation and puncture (CLP) in endotoxin-tolerant C3H/HeJ or FasL-deficient C3H/HeJ-FasL(gld) (FasL(-)) mice and LP lymphocytes were isolated 24 h later. Phenotypic, apoptotic, and functional indexes were assessed. The number of LP B cells decreased markedly in C3H/HeJ mice but not in FasL-deficient animals at 24 h after CLP. This was associated with comparable alteration in apoptosis and Fas antigen expression in the B cells of these mice. Septic LP lymphocytes also showed increased IgA production, which was absent in the FasL-deficient CLP mice. Furthermore, Fas ligand deficiency appeared to improve survival of septic challenge. These data suggest that the increase in B cell apoptosis in septic animals is partially due to a Fas/FasL-mediated process but not endotoxin.

Debate: transfusing to normal haemoglobin levels will not improve outcome

Recent evidence suggests that critically ill patients are able to tolerate lower levels of haemoglobin than was previously believed. It is our goal to show that transfusing to a level of 100 g/l does not improve mortality and other clinically important outcomes in a critical care setting. Although many questions remain, many laboratory and clinical studies, including a recent randomized controlled trial (RCT), have established that transfusing to normal haemoglobin concentrations does not improve organ failure and mortality in the critically ill patient. In addition, a restrictive transfusion strategy will reduce exposure to allogeneic transfusions, result in more efficient use of red blood cells (RBCs), save blood overall, and decrease health care costs.

Reduced blood loss during burn surgery

The purpose of this study was to investigate the use of subcutaneous injection of burn wounds and skin graft donor sites with an adrenaline-saline solution to reduce blood loss during burn surgery. This retrospective study reviewed the requirements of blood products in 30 randomly selected adult patients with more than 10% body area burned, who had at least one burn operation at a university regional burn center, between January 1991 and June 1997. Patients were matched by age and percent body area burned and stratified according to the surgical technique in two groups. In Group 1, 15 patients received the modified tumescent surgical technique: subcutaneous injection of adrenaline (1 part/million in warm saline solution) into the subcutaneous tissue of the donor sites for autologous skin graft and areas of burn eschar to be excised, combined with pneumatic tourniquets in extremities and saline-adrenaline soaked nonadherent pads. In Group 2, 15 patients received the traditional surgical technique: soaked gauze compresses with an adrenaline-thrombin solution (1 ml of 1:1,000 adrenaline, thrombin 10,000 units, and 1 L of normal saline). Outcome measures, transfusion of blood products, operating time and complications between the two patient groups were analyzed using the Wilcoxon 2-sample test. The two patient groups were not different by age (40.4 +/- 19.4 vs 38.9 +/- 17.9), percent total body area burned (27.6 +/- 15.4 vs 32.8 +/- 13.4), or percent full thickness burn (7.0 +/- 8.5 vs 11.5 +/- 8.5). The modified tumescent surgical technique significantly reduced mean total blood units transfused per patient (7.9 +/- 11.5 vs 15.7 +/- 12.9 units; P = .031), and the mean blood units transfused intraoperatively per patient (4.7 +/- 7.8 vs 8.9 +/- 8.0 units; P = .026). The modified tumescent surgical technique significantly reduced the intraoperative and total blood transfusion requirements in our thermally injured patients.

Preventing surgical site infections: a surgeon's perspective

Wound site infections are a major source of postoperative illness, accounting for approximately a quarter of all nosocomial infections. National studies have defined the patients at highest risk for infection in general and in many specific operative procedures. Advances in risk assessment comparison may involve use of the standardized infection ratio, procedure-specific risk factor collection, and logistic regression models. Adherence to recommendations in the 1999 Centers for Disease Control and Prevention guidelines should reduce the incidence of infection in surgical patients.

Perioperative antibiotic use in high-risk penetrating hollow viscus injury: a prospective randomized, double-blind, placebo-control trial of 24 hours versus 5 days

BACKGROUND

The purpose of this study was to compare the safety and therapeutic efficacy of a 24-hour versus 5-day course of ampicillin/sulbactam for the prevention of postoperative infections in high-risk patients sustaining hollow viscus injury from penetrating abdominal trauma.

METHODS

A total of 317 patients from four Level I trauma centers with penetrating abdominal injuries and at least one hollow viscus perforation each received one preoperative and three postoperative doses of ampicillin/sulbactam 3 g intravenously. After receiving 24 hours of unblinded ampicillin/sulbactam, patients were then randomized into one of two groups. Group 1 received 4 additional days of blinded ampicillin/sulbactam (5 days total of antibiotic), and Group 2 received 4 days of placebo (24 hours of antibiotic). Patients were assessed postoperatively for occurrence of deep surgical-site infections (intra-abdominal abscess, fasciitis, and peritonitis) and superficial (wound) surgical-site infections. Development of nonsurgical-site infections (e.g., pneumonia, urinary tract infection, phlebitis, and cellulitis) was also recorded. Continuous variables were analyzed by analysis of variance and discrete variables by the Cochran-Mantel-Haenszel chi2 test. Multivariate logistic regression analyses were also performed to identify independent risk factors for postoperative infection.

RESULTS

A total of 159 patients were randomized into Group 1, and 158 patients were randomized into Group 2. The Injury Severity Score and penetrating abdominal trauma index were 18+/-8 and 21+/-13, respectively, for Group 1 and 18+/-9 and 20+/-15, respectively, for Group 2. A total of 162 (51%) patients sustained one or more colon injuries (82 in Group 1 and 80 in Group 2). There were 16 (10%) surgical-site infections in Group 1 and 13 (8%) surgical-site infections in Group 2 (p = 0.74). Group 1 patients experienced 17 (11%) nonsurgical-site infections, whereas Group 2 had 32 (20%) nonsurgical-site infections. This difference, however, was not statistically significant (p = 0.16). Only the total number of blood units transfused and the presence of a PATI score greater than or equal to 25 were found to be independently associated with the development of a postoperative surgical- and nonsurgical-site infections (p = 0.001 and p = 0.003, respectively). Of note, the presence of a colon injury was not found to be an independent risk factor (p = 0.11) for either surgical or nonsurgical site postoperative infection in our study.

CONCLUSION

High-risk patients with colon or other hollow viscus injuries from penetrating abdominal trauma are at no greater risk for surgical-site or nonsurgical-site infection when treated with only a 24-hour course of a broad-spectrum antibiotic.

Infectious complications in critically injured children

PURPOSE

Infection will complicate the care of a significant number of injured adults. Trauma is the leading cause of mortality in the pediatric population, yet little information is available regarding the incidence of infection in this group. This study evaluates infectious complications in the critically injured child.

METHODS

All children admitted to the pediatric intensive care unit from an urban level-1 trauma center during an 80-consecutive-month period were studied. Infection was defined by Centers for Disease Control criteria and was identified by a retrospective review of the medical records. Demographic and clinical information, including microbiologic data, were compiled for all study patients. Data were analyzed using Student's (t)test or chi2 analysis where appropriate.

RESULTS

Five hundred twenty-three children were at risk for infection during the study period. Seventy-eight infections were documented in 53 children (incidence, 10.1%). Nosocomial infections accounted for 78% of these with a majority (85%) being device associated. Common infections in this group included lower respiratory (n = 35), primary bloodstream (n = 10), and urinary tract (n = 7). Trauma-related infections were primarily wound (n = 9), intraabdominal (n = 3), or central nervous system (n = 3). Bacterial pathogens predominated, and the most frequent microorganisms recovered were Staphylococcus aureus, Pseudomonas sp, and Haemophilus sp. Children with infectious complications were more severely injured (injury severity score [ISS] 24 versus 17, P < .001) and had a longer hospital stay (21 days v 6 days, P < .001) compared with children without infection during the same period. Overall mortality rate for the study group was 5.7% and was not significantly different from children without infection.

CONCLUSIONS

Infection is a significant source of morbidity in the critically injured child. Nosocomial infections predominate, and a majority of these are device related, emphasizing the need for continued vigilance toward prevention in this high-risk group.

Factors affecting mortality and morbidity in patients with abdominal gunshot wounds

Risk factors that may independently predict mortality and morbidity in patients with abdominal gunshot wounds have not been fully elucidated. We prospectively studied the effects of 12 potential risk factors on mortality and morbidity in 82 patients with abdominal gunshot wounds who required laparotomy. Univariate analysis of these factors revealed that shock on admission, presence of penetrating colon injury and number of intra-abdominal organs injured (NOI)>2 were associated with greater than threefold increased incidence of death (p<0.05). Penetrating abdominal trauma index (PATI) score>15 was associated with twentyfold increased incidence of death (P<0.0001). Multivariate analysis showed that only PATI (P=0.001), number of postoperative complications per patient (N(comp)) (P=0.023) and presence of shock on admission (P=0. 028) were independently significant in predicting mortality. PATI was the only risk factor that independently predicted the development of postoperative infectious complications and N(comp) (P<0.0001). The type of gun used was not a significant risk factor (P>0.05). The 15 (18.3%) non-survivors were significantly older than survivors (P=0.02), had longer operations (P=0.004) and their NOI, PATI and N(comp) were significantly higher (P<0.001). The uniformly prolonged injury to surgery time in all patients contributed to the high incidence of infectious complications (62.2%) and mortality. PATI score was the most important factor found to be independently associated with mortality and morbidity in our subset of patients with prolonged injury to surgery time and high rate of colon injury.

Effects of hypoxia on granulocytic-monocytic progenitors in rats. Role of bone marrow stroma

Hemorrhagic shock leads to hypoxia and is associated with bone marrow (BM) failure. Hemorrhagic shock is also a predisposing factor in immune dysregulation. Since the BM is the major organ of immune cells in the adult, its failure following hemorrhagic shock may explain the increased susceptibility to infection. The in vitro evidence indicates that hypoxia mediates altered functions in BM stroma. Since similar hematopoietic alterations are reported in hypoxia and hemorrhagic shock, hypoxia alone could be a representative model to study BM responses during hemorrhagic shock. In this study, we use an animal model to dissect the hematopoietic effects of hypoxia. We subjected rats to hypoxia, and at days 1 and 5 post-hypoxia we determined the numbers of granulocytic-monocytic progenitors (CFU-GM) in the BM. We found significant increase (P < 0.05) in CFU-GM at day 1 and a downward trend by day 5. Enhanced BM cellularity could not explain the increase in CFU-GM by day 1. BM stromal cells mediated most of the stimulatory effects by hypoxia. CFU-GM was inversely proportional to bioactive TGF-beta and directly proportional to IL-1. Compared to normoxic rats, IL-6 production was suppressed in BM cells from hypoxic rats. The results show that hypoxia alone initiate a stimulatory response in CFU-GM progenitors. These effects are at least partially mediated through the BM stroma. In the absence of a second insult, CFU-GM reverts to baseline. The data also suggest that hypoxia mediates complex responses that include cytokine production. These results add to the current understanding of hematopoietic responses by hypoxia and adds to the mechanisms of immune dysfunctions following hemorrhagic shock.

Does the Centers for Disease Control's NNIS system risk index stratify patients undergoing cardiothoracic operations by their risk of surgical-site infection?

BACKGROUND

In 1991, the Centers for Disease Control and Prevention devised the National Nosocomial Infection Surveillance (NNIS) System risk index to stratify populations of surgical patients by the risk of acquiring surgical-site infections (SSIs).

OBJECTIVE

To determine whether the NNIS risk index adequately stratifies a population of cardiothoracic surgery patients by the risk of developing SSI.

DESIGN

Case-control study.

SETTING

The University of Iowa Hospitals and Clinics, a 900-bed, midwestern, tertiary-care hospital.

PATIENTS

201 patients with SSIs identified by prospective infection control surveillance and 398 controls matched by age, gender, type of procedure, and date of procedure. All patients underwent cardiothoracic operative procedures between November 1990 and January 1994.

RESULTS

The SSI rate was 7.8%. Seventy-four percent of cases and 80% of controls had a NNIS risk index score of 1; 24% of cases and 16% of controls had a score of 2 (P=.05). Patients with a NNIS risk score > or =2 were 1.8 times more likely to develop an SSI than those with a NNIS score <2 (odds ratio, 1.83; 95% confidence interval, 1.14-2.94, P=.01). The duration of the procedure was the only component of the index that stratified the population by risk of SSI.

CONCLUSIONS

The risk of SSI after cardiothoracic operations increases as the NNIS risk index score increases. However, this index only dichotomized the patient population on the basis of the procedure duration. More research is needed to develop a risk index that adequately stratifies the risk of SSI after cardiothoracic operations.

Correlação entre o fluxo sangüíneo intestinal e a cicatrização de anastomoses colônicas: estudo experimental em cães

As anastomoses colônicas estão associadas à alta incidência de deiscências e o choque é um dos fatores etiológicos relacionados.O objetivo do presente estudo foi correlacionar as alterações do fluxo sanguíneo intestinal decorrentes do choque hipovolêmico e a cicatrização das anastomoses colônicas. Dezesseis cães foram submetidos à anastomose cólon-colônica, sendo que em oito deles o choque hipovolêmico foi induzido. Excetuando o período de confecção da anastomose, o fluxo sanguíneo intestinal foi continuamente aferido. Registrou-se a freqüência cardíaca e pressão arterial média durante todo o experimento. Coletou-se três amostras de sangue para determinação do volume globular em três momentos diferentes da cirurgia. No 7º dia de pós-operatório os cães foram submetidos novamente à operação para avaliação clínica da anastomose (presença de abscessos, fistulas ou deiscências). Retirou-se uma porção de 15 cm do cólon contendo a anastomose para aferição da pressão de ruptura e estudo anátomo-patológico com as colorações: H-E e picrosírius (densitometria do colágeno). Os parâmetros clínicos avaliados determinaram um índice de complicações infecciosas duas vezes superior no grupo chocado que no grupo controle. Não houve diferença estatisticamente significante com relação à pressão de ruptura, todavia a concentração de colágeno total foi maior no grupo controle do que no grupo submetido ao choque. O estudo anátomo-patológico (H-E) demonstrou parâmetros de cicatrização mais favoráveis no grupo controle. Assim, concluiu-se que a diminuição do fluxo sanguíneo intestinal acarretou deterioração do processo cicatricial das anastomoses, pelo maior número de complicações, menor concentração de colágeno total e comprometimento nos parâmetros histológicos.

Infection in hospitalized trauma patients: incidence, risk factors, and complications

BACKGROUND

Several factors place victims of multiple trauma at increased risk for infection. The purpose of this study was to delineate the frequency of, types of, and risk factors for infection in hospitalized trauma patients.

METHODS

Prospective surveillance for nosocomial infection was conducted for all trauma patients who were admitted for more than 24 hours to a tertiary-care regional trauma center between January 1 and December 31, 1996.

RESULTS

A total of 563 patients (414 males) with a mean age of 40 years (range, 15-97 years) were followed. Most (86%) sustained blunt traumatic injuries. A total of 367 infections occurred in 209 (37%) patients for an incidence of 32.1/1,000 patient-days. The hospital stay of 37% of patients was complicated by at least one infection, involving the following sites: lower respiratory tract (28%), urinary tract (24%), surgical wound (18%), skin/soft tissue (13%), intra-abdominal (5%), primary bloodstream (5%), and other sites (8%). Infection was complicated by septic shock in 36 (10%) cases, acute respiratory distress syndrome in 32 (9%) cases, and multiorgan failure in 13 (4%) cases. Death was attributed to infection in four patients. In a multivariate analysis, infected patients were more likely to have been ventilated (odds ratio [OR] = 2.6; p<0.001), to have had multiple surgical procedures (OR = 2.8; p = 0.02), to have received multiple blood transfusions (OR = 2.3; p = 0.04), and to have had a spinal cord injury (OR = 5.0; p = 0.002). First surgical procedure within 24 hours of admission was protective (OR = 0.4, p = 0.001).

CONCLUSION

Trauma patients are at high risk for developing infection. Identifying patients who are at increased risk for infection may allow for early intervention and subsequent decrease in infectious morbidity.

Protective effects of C5a blockade in sepsis

Sepsis in humans is a difficult condition to treat and is often associated with a high mortality rate. In this study, we induced sepsis in rats using cecal ligation and puncture (CLP). In rats depleted of the complement factor C3, CLP led to very short survival times (about 4 days). Of the rats that underwent CLP ('CLP rats') that were C3-intact and treated with preimmune IgG, most (92%) were dead by 7 days. Blood neutrophils from these rats contained on their surfaces the powerful complement activation product C5a. This group had high levels of bacteremia, and their blood neutrophils when stimulated in vitro had greatly reduced production of H2O2, which is known to be essential for the bactericidal function of neutrophils. In contrast, when companion CLP rats were treated with IgG antibody against C5a, survival rates were significantly improved, levels of bacteremia were considerably reduced, and the H2O2 response of blood neutrophils was preserved. Bacterial colony-forming units in spleen and liver were very high in CLP rats treated with preimmune IgG and very low in CLP rats treated with IgG antibody against C5a, similar to values obtained in rats that underwent 'sham' operations (without CLP). These data indicate that sepsis causes an excessive production of C5a, which compromises the bactericidal function of neutrophils. Thus, C5a may be a useful target for the treatment of sepsis.

Guideline for Prevention of Surgical Site Infection, 1999. Centers for Disease Control and Prevention (CDC) Hospital Infection Control Practices Advisory Committee

EXECUTIVE SUMMARY The "Guideline for Prevention of Surgical Site Infection, 1999" presents the Centers for Disease Control and Prevention (CDC)'s recommendations for the prevention of surgical site infections (SSIs), formerly called surgical wound infections. This two-part guideline updates and replaces previous guidelines.1,2 Part I, "Surgical Site Infection: An Overview," describes the epidemiology, definitions, microbiology, pathogenesis, and surveillance of SSIs. Included is a detailed discussion of the pre-, intra-, and postoperative issues relevant to SSI genesis. Part II, "Recommendations for Prevention of Surgical Site Infection," represents the consensus of the Hospital Infection Control Practices Advisory Committee (HICPAC) regarding strategies for the prevention of SSIs.3 Whenever possible, the recommendations in Part II are based on data from well-designed scientific studies. However, there are a limited number of studies that clearly validate risk factors and prevention measures for SSI. By necessity, available studies have often been conducted in narrowly defined patient populations or for specific kinds of operations, making generalization of their findings to all specialties and types of operations potentially problematic. This is especially true regarding the implementation of SSI prevention measures. Finally, some of the infection control practices routinely used by surgical teams cannot be rigorously studied for ethical or logistical reasons (e.g., wearing vs not wearing gloves). Thus, some of the recommendations in Part II are based on a strong theoretical rationale and suggestive evidence in the absence of confirmatory scientific knowledge.It has been estimated that approximately 75% of all operations in the United States will be performed in "ambulatory," "same-day," or "outpatient" operating rooms by the turn of the century.4 In recommending various SSI prevention methods, this document makes no distinction between surgical care delivered in such settings and that provided in conventional inpatient operating rooms. This document is primarily intended for use by surgeons, operating room nurses, postoperative inpatient and clinic nurses, infection control professionals, anesthesiologists, healthcare epidemiologists, and other personnel directly responsible for the prevention of nosocomial infections. This document does not: Specifically address issues unique to burns, trauma, transplant procedures, or transmission of bloodborne pathogens from healthcare worker to patient, nor does it specifically address details of SSI prevention in pediatric surgical practice. It has been recently shown in a multicenter study of pediatric surgical patients that characteristics related to the operations are more important than those related to the physiologic status of the patients.5 In general, all SSI prevention measures effective in adult surgical care are indicated in pediatric surgical care. Specifically address procedures performed outside of the operating room (e.g., endoscopic procedures), nor does it provide guidance for infection prevention for invasive procedures such as cardiac catheterization or interventional radiology. Nonetheless, it is likely that many SSI prevention strategies also could be applied or adapted to reduce infectious complications associated with these procedures. Specifically recommend SSI prevention methods unique to minimally invasive operations (i.e., laparoscopic surgery). Available SSI surveillance data indicate that laparoscopic operations generally have a lower or comparable SSI risk when contrasted to open operations.6-11 SSI prevention measures applicable in open operations (e.g., open cholecystectomy) are indicated for their laparoscopic counterparts (e.g., laparoscopic cholecystectomy). Recommend specific antiseptic agents for patient preoperative skin preparations or for healthcare worker hand/forearm antisepsis. Hospitals should choose from products recommended for these activitie

Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee

The “Guideline for Prevention of Surgical Site Infection, 1999” presents the Centers for Disease Control and Prevention (CDC)'s recommendations for the prevention of surgical site infections (SSIs), formerly called surgical wound infections. This two-part guideline updates and replaces previous guidelines.

Part I, “Surgical Site Infection: An Overview,” describes the epidemiology, definitions, microbiology, pathogenesis, and surveillance of SSIs. Included is a detailed discussion of the pre-, intra-, and postoperative issues relevant to SSI genesis.

The duration of antibiotic administration in penetrating abdominal trauma

BACKGROUND

The epidemiology of penetrating abdominal trauma is changing to reflect an increasing incidence of multiple injuries. Not only do multiple injuries increase the risk of infection, a very high risk of serious infection is conferred by immunosuppression from hemorrhage and transfusion and the high likelihood of intestinal injury, especially to the colon. Optimal timing and choice of presumptive antibiotic therapy has been established for penetrating trauma, but duration has not been studied extensively in such seriously injured patients. The purpose of this study was to test the hypothesis that 24 hours of antibiotic therapy remains sufficient to reduce the incidence of infection in penetrating abdominal trauma.

METHODS

Three hundred fourteen consecutive patients with penetrating abdominal trauma were prospectively randomized into two groups: Group I received 24 hours of intravenous cefoxitin (1 g q6h) and group II received 5 days of intravenous cefoxitin. The development of a deep surgical site (intra-abdominal) infection as well as any type of nosocomial infection, as defined by the Centers for Disease Control and Prevention, (ie, surgical site infections, catheter-related infections, urinary tract, pneumonia), was recorded. Hospital length of stay was a secondary endpoint. Statistical analysis included chi-square tests for coordinate variables and two-tailed unpaired t tests for continuous variables. The independence of risk factors for the development of infection was assessed by multivariate analysis of variance. Significance was determined when P <0.05.

RESULTS

Three hundred patients were evaluable. There was no postoperative mortality, and no differences in overall length of hospitalization between groups. The duration of antibiotic treatment had no influence on the development of any infection (P = 0.136) or an intraabdominal infection (P = 0.336). Only colon injury was an independent predictor of the development of an intraabdominal infection (P = 0.0031). However, the overall infection incidence was affected by preoperative shock (P = 0.003), colon (P = 0.0004), central nervous system (CNS) injuries (P = 0.031), and the number of injured organs (P = 0.026). Several factors, including intraoperative shock (P = 0.021) and injuries to the colon (P = 0.0008), CNS (P = 0.0001), and chest (P = 0.0006), were independent contributors to prolongation of the hospital stay.

CONCLUSIONS

Twenty-four hours of presumptive intravenous cefoxitin versus 5 days of therapy made no difference in the prevention of postoperative infection or length of hospitalization. Infection was associated with shock on admission to the emergency department, the number of intra-abdominal organs injured, colon injury specifically, and injury to the central nervous system. Intra-abdominal infection was predicted only by colon injury. Prolonged hospitalization was associated with intraoperative shock and injuries to the chest, colon, or central nervous system.

Variation in red cell transfusion practice in the intensive care unit: a multicentre cohort study

OBJECTIVES: To determine the degree of interinstitutional transfusion practice variation and reasons why red cells are administered in critically ill patients. STUDY DESIGN: Multicentre cohort study combined with a cross-sectional survey of physicians requesting red cell transfusions for patients in the cohort. STUDY POPULATION: The cohort included 5298 consecutive patients admitted to six tertiary level intensive care units in addition to administering a survey to 223 physicians requesting red cell transfusions in these units. MEASUREMENTS: Haemoglobin concentrations were collected, along with the number and reasons for red cell transfusions plus demographic, diagnostic, disease severity (APACHE II score), intensive care unit (ICU) mortality and lengths of stay in the ICU. RESULTS: Twenty five per cent of the critically ill patients in the cohort study received red cell transfusions. The overall number of transfusions per patient-day in the ICU averaged 0.95 +/- 1.39 and ranged from 0.82 +/- 1.69 to 1.08 +/- 1.27 between institutions (P < 0.001). Independent predictors of transfusion thresholds (pre-transfusion haemoglobin concentrations) included patient age, admission APACHE II score and the institution (P < 0.0001). A very significant institution effect (P < 0.0001) persisted even after multivariate adjustments for age, APACHE II score and within four diagnostic categories (cardiovascular disease, respiratory failure, major surgery and trauma) (P < 0.0001). The evaluation of transfusion practice using the bedside survey documented that 35% (202 of 576) of pre-transfusion haemoglobin concentrations were in the range of 95-105 g/l and 80% of the orders were for two packed cell units. The most frequent reasons for administering red cells were acute bleeding (35%) and the augmentation of O2 delivery (25%). CONCLUSIONS: There is significant institutional variation in critical care transfusion practice, many intensivists adhering to a 100g/l threshold, and opting to administer multiple units despite published guidelines to the contrary. There is a need for prospective studies to define optimal practice in the critically ill.

Lactated ringer's is superior to normal saline in a model of massive hemorrhage and resuscitation

BACKGROUND

Previous models comparing normal saline (NS) with lactated Ringer's solution (LR) for resuscitation use only mild or moderate hemorrhage and do not address the clinical situation of massive hemorrhage and resuscitation (MHR). This work compares NS and LR by using a new rat model of MHR.

METHODS

NS and LR were compared by using both a traditional model of moderate pressure-controlled hemorrhage and a model of MHR. Moderate hemorrhage animals were bled to mean arterial pressure (MAP) = 60 mm Hg x 2 hour then resuscitated with crystalloid (NS or LR) for 1 hour. MHR animals were bled at a rate of 1 estimated blood volume (EBV) per hour for 2 hours with simultaneous resuscitation by using washed red blood cells (B) and crystalloid (LR+B or NS+B). MAP was kept at 60 mm Hg during the 2 hours of hemorrhage. Bleeding was then stopped, and animals were resuscitated for 1 additional hour with blood and crystalloid to MAP more than 90 mm Hg or until 10x EBV was given. Group means were compared with Student's t test (p < 0.01 significant) and 2-week survival rates were compared by using Fisher's exact test (p < 0.05 significant).

RESULTS

The moderate hemorrhage group was bled 36% of EBV. In this setting, resuscitation with NS and LR was equivalent. The final hematocrit, pH, and base excess were not different, and all animals survived in both groups. MHR animals were bled 218% of EBV. Animals resuscitated with NS+B were significantly more acidotic than animals resuscitated with equal volumes of LR+B (pH 7.14+/-.06 vs. 7.39+/-.04, respectively) and had significantly worse survival (50% vs. 100%, respectively).

CONCLUSION

With moderate hemorrhage, NS and LR are equivalent, but in the setting of massive hemorrhage and resuscitation, significantly more physiologic derangement and mortality occurs with NS than LR. LR is superior to NS for use in massive resuscitation.

Ferimentos penetrantes tóraco-abdominais e de tórax e abdome: análise comparativa da morbidade e mortalidade pós-operatórias

Analisamos 145 doentes portadores de ferimentos penetrantes tóraco-abdominais e de tórax e abdome, operados no Serviço de Emergência da Santa Casa de São Paulo de julho de 1987 a fevereiro de 1996, sendo 72 (49,7%) produzidos por arma branca e 73 (50,3%) por projétil de arma de fogo. Foram estudados fatores relacionados à ocorrência de complicações pós-operatórias (pleuropulmonares, abdominais e sistêmicas), ao prolongamento do tempo de permanência hospitalar e à mortalidade ocorrida durante a internação. Caracterizamos os doentes quanto a sua gravidade, através da aplicação de índices objetivos de trauma, tanto fisiológico (RTS) quanto anatômicos (ISS, PATI, PTTI e PTI). Tanto nos ferimentos tóraco- abdominais quanto de tórax e abdome, o tratamento de escolha foi a drenagem pleural associada à laparotomia exploradora. Os ferimentos tóraco-abdominais apresentaram maior incidência de complicações em geral, em relação aos de tórax e abdome, quando a variável controle foi o ferimento produzido por arma branca. A análise por tipo de complicação mostrou que essa diferença foi dada pelo empiema pleural. Não encontramos diferença significante entre esses ferimentos com relação às demais complicações pleuropulmonares infecciosas, abdominais e sistêmicas. Os fatores que se correlacionaram com a evolução para empiema foram: o tipo de órgão lesado (estômago, esôfago e reto), a presença de fístula digestiva, o ferimento produzido por arma branca e a presença de lesão diafragmática. O prolongamento do tempo de permanência hospitalar foi determinado pela ocorrência de complicações e não pela lesão diafragmática. Houve doze (8,3%) mortes no estudo, sendo que a mortalidade correlacionou-se com maior média de lesões orgânicas por doente, com as lesões de rim, grandes vasos e esôfago, com a ocorrência de complicações especialmente de natureza infecciosa e com o ferimento produzido por projétil de arma de fogo. A análise dos nossos resultados permitiu concluir que os ferimentos penetrantes tóraco-abdominais apresentam maior número de lesões orgânicas por doente quando comparados aos ferimentos de tórax e abdome (sem lesão diafragmática), mas esses ferimentos não diferem quanto à mortalidade pós-operatória. Com relação à morbidade, a lesão diafragmática não foi fator determinante do prolongamento do tempo de permanência hospitalar e, na comparação dos ferimentos tóraco-abdominais e de tórax e abdome, a lesão diafragmática produzida por arma branca foi fator determinante do aparecimento de empiema pleural.

The fate of colonic suture lines in high-risk trauma patients: a prospective analysis

BACKGROUND

Some authors have stated that virtually all patients with penetrating colon injuries can be safely managed with primary repair. The purpose of this study is to test the applicability of this statement to all trauma patients by evaluating a protocol of liberal primary repair applied to a group of patients at high risk of septic complications.

STUDY DESIGN

We performed a prospective analysis of a liberal policy of primary repair applied to patients at high risk of developing postoperative septic complications admitted to a Level I urban trauma center. Inclusion criteria were full-thickness colon injury and at least one of three additional risk factors: 1) Penetrating Abdominal Trauma Index (PATI) of 25 or more; 2) 6 U or more of blood transfused; and 3) 6 hours or longer elapsed between injury and surgery.

RESULTS

Of 56 patients studied (55 male, 1 female, average age 28.8 years, mean PATI 35.3), the vast majority had gunshot wounds as the mechanism of injury (89%), PATI 25 or more (95%), multiple blood transfusions (77%), an Injury Severity Score greater than 15 (66%), and a need for postoperative ventilatory support in the surgical intensive care unit (61%). Of 56 patients, 49 (88%) had at least one colonic suture line, and 25 patients (45%) had destructive colon injuries requiring resection. Intraabdominal infections occurred in 15 (27%) of 56 patients and colon suture line disruption occurred in 3 (6%) of 49. Two of these patients developed multisystem organ failure, and death was directly related to breakdown of their colonic anastomosis.

CONCLUSIONS

On the basis of these data and the relative infrequency of patients in prospective randomized trials with destructive colon injuries, we believe there is still room for consideration of fecal diversion in patients in high-risk categories with destructive colon injuries requiring resection.

Sepsis induces increased apoptosis in lamina propria mononuclear cells which is associated with altered cytokine gene expression

Studies indicate that lymphoid tissue (e.g., thymus, bone marrow, and Peyer's patches) shows evidence of increase apoptosis (Ao, a form of nonnecrotic cell death) during sepsis. However, it is not known if mucosal lymphoid tissue, such as lamina propria (LP), also shows evidence of increased Ao and if so, is this associated with functional changes, i.e., cytokine gene expression in the LP. To examine this, male C3H/HeN mice were subjected to cecal ligation and puncture (CLP) and lamina propria mononuclear cells (LPMC) were harvested at 4 h (early sepsis) or 24 h (late sepsis). Alterations in the cell phenotype as well as Ao (Tunel assay) were determined by three-color flow cytometry. Cytokine gene expression was assessed by multiprobe RNase protection assay. Sham LPMC preparations were found to be 34.4 +/- 2.4% B220(+) (B-cells), while 12.4 +/- 2.1% were CD8(+) (cytotoxic T-cells), 22.0 +/- 0.8% were CD4(+) (helper T-cells), and 6.4 +/- 0.7% were F4/80(+) (macrophages). The frequency of B220(+) (9%* upward arrow) and CD8 (6%* upward arrow) populations increased markedly at 4 h after CLP; however, this increase was not seen at 24 h. The percentage of Ao+ in CD8(+), B220(+), and F4/80(+) cells increased markedly at both 4 and 24 h. CD4(+) cells showed a marked increase in Ao only at 24 h after CLP. When LPMC mRNA expression was examined, a significant increase in IL-2, -10, and -15 gene expression was observed only at 24 h but not 4 h after CLP. Thus, the early phenotypic changes associated with increased Ao may be a reflection of localized immune cell activation in early sepsis contributing to the increased cytokine gene expression seen in late sepsis. This localized activation may contribute to gastrointestinal inflammation and/or immune dysfunction in sepsis.

A Canadian survey of transfusion practices in critically ill patients. Transfusion Requirements in Critical Care Investigators and the Canadian Critical Care Trials Group

OBJECTIVES

To characterize the contemporary red cell transfusion practice in the critically ill and to define clinical factors that influence these practices.

DESIGN

Scenario-based national survey.

STUDY POPULATION

Canadian critical care practitioners.

MEASUREMENTS AND MAIN RESULTS

We evaluated transfusion thresholds before transfusion and the number of red cell units ordered, under the given conditions. Of 254 Canadian critical care physicians, 193 (76%) responded to the survey. The primary specialty of most respondents was internal medicine (56%). Internal medicine respondents were in practice for an average of 8.4 +/- 5.7 (SD) yrs, and worked most often in combined medical/surgical intensive care units. Baseline hemoglobin transfusion thresholds averaged from 8.3 +/- 1.0 g/dL in a scenario involving a young stable trauma victim to 9.5 +/- 1.0 g/dL for an older patient after gastrointestinal bleeding. Transfusion thresholds differed significantly (p< .0001) between all four separate scenarios. With the exception of congestive heart failure (p> .05), all clinical factors (including age, Acute Physiology and Chronic Health Evaluation II score, preoperative status, hypoxemia, shock, lactic acidosis, coronary ischemia, and chronic anemia) significantly (p< .0001) modified the transfusion thresholds. A statistically significant (p< .01) difference in baseline transfusion thresholds was noted across four major regions (with a maximum of five academic centers per region) of the country. Low physician numbers in two of the regions did not allow for further investigation of regional variations.

CONCLUSIONS

There is significant variation in critical care transfusion practice, with many intensivists adhering to a 10.0-g/dL threshold, while other physicians described a much more restrictive approach to red cell transfusion. Also, many physicians opted to administer multiple units, despite published guidelines to the contrary. Additionally, the administration of red cells was strongly influenced by a number of clinical factors, many unique to intensive care unit patients. There is a need for prospective studies to define optimal practice in the critically ill.

Distinct effects of allogeneic blood transfusion on splenocyte cytokine production after hemorrhagic shock

Allogeneic blood transfusion is known to be immunosuppressive in the settings of cancer and transplantation, but the contribution of blood transfusion to immunomodulation after hemorrhage is unknown. Our purpose was to determine the influence of allogeneic blood transfusion upon cytokine profiles following hemorrhagic shock, using a model which approximates the clinical setting.

METHODS

Male C3H/HeN mice were hemorrhaged via femoral arterial catheters to a mean arterial pressure (MAP) of 35 +/- 5 mm Hg, which was maintained for 1 h. Mice were resuscitated with autologous blood (auto BT) or allogeneic blood (allo BT) from Balb/c mice (both equivalent to volume of shed blood), and crystalloid (2X the volume of shed blood)-infused at 0.05 ml/min. Animals were sacrificed at 1, 2, and 5 days postshock, and splenocytes were cultured for 24 h with anti-CD3 antibody. Supernatants were assayed for IL-2, IL-6, IL-10, and gamma-IFN by ELISA.

RESULTS

Regardless of transfusion status, hemorrhagic shock resulted in increased IL-6 and gamma-IFN by Day 2 postshock. Distinct cytokine alterations after allogeneic transfusion were as follows. IL-2: transient elevation of splenocyte IL-2 production in the shock + allo BT group (P < 0.005 vs. shock + auto BT) at Postshock Day 2. IL-6: suppression in IL-6 production in the shock + allo BT group by Postshock Day 5 (P < 0.05 vs. shock + auto BT). IL-10: persistently elevated IL-10 production following shock + allo BT (Day 1, P < 0.001 vs. shock + auto BT; Day 5; P < 0.05 vs. shock + auto BT). gamma-IFN: elevation in gamma-IFN production by Day 5 in the shock + allo BT group (P < 0.0005 vs. shock + auto BT).

CONCLUSIONS

Allogeneic blood transfusion results in distinct alterations in splenocyte production of IL-2, IL-6, IL-10, and gamma-IFN after hemorrhagic shock. This model reflects the clinical usage of blood products and demonstrates some of the immune alterations after transfusion.

Influence of blood transfusion on bactericidal activity of human leukocytes and sera against Yersinia enterocolitica and Salmonella typhimurium

Patients undergoing joint surgery and blood transfusion were studied. Serum and leukocyte bactericidal tests in vitro against Salmonella typhimurium and Yersinia enterocolitica were carried out preoperatively as well as on the 1st, 3rd and 7th days after the operation. The serum complement (C3 and C4) concentrations were determined at the same intervals. It was found that after blood transfusion the bactericidic activity of sera and the serum C3 complement concentrations were increased. In contrast the killing ability of leukocytes was suppressed.

Metronidazole. A therapeutic review and update

The nitroimidazole antibiotic metronidazole has a limited spectrum of activity that encompasses various protozoans and most Gram-negative and Gram-positive anaerobic bacteria. Metronidazole has activity against protozoans like Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis, for which the drug was first approved as an effective treatment. Anaerobic bacteria which are typically sensitive are primarily Gram-negative anaerobes belonging to the Bacteroides and Fusobacterium spp. Gram-positive anaerobes such as peptostreptococci and Clostridia spp. are likely to test sensitive to metronidazole, but resistant isolates are probably encountered with greater frequency than with the Gram-negative anaerobes. Gardnerella vaginalis is a pleomorphic Gram-variable bacterial bacillus that is also susceptible to metronidazole. Helicobacter pylori has been strongly associated with gastritis and duodenal ulcers. Classic regimens for eradicating this pathogen have included metronidazole, usually with acid suppression medication plus bismuth and amoxicillin. The activity of metronidazole against anaerobic bowel flora has been used for prophylaxis and treatment of patients with Crohn's disease who might develop an infectious complication. Treatment of Clostridium difficile-induced pseudomembraneous colitis has usually been with oral metronidazole or vancomycin, but the lower cost and similar efficacy of metronidazole, coupled with the increased concern about imprudent use of vancomycin leading to increased resistance in enterococci, have made metronidazole the preferred agent here. Metronidazole has played an important role in anaerobic-related infections. Advantages to using metronidazole are the percentage of sensitive Gram-negative anaerobes, its availability as oral and intravenous dosage forms, its rapid bacterial killing, its good tissue penetration, its considerably lower chance of inducing C. difficile colitis, and expense. Metronidazole has notable effectiveness in treating anaerobic brain abscesses. Metronidazole is a cost-effective agent due to its low acquisition cost, its pharmacokinetics and pharmacodynamics, an acceptable adverse effect profile, and its undiminished antimicrobial activity. While its role as part of a therapeutic regimen for treating mixed aerobic/anaerobic infections has been reduced by newer, more expensive combination therapies, these new combinations have not been shown to have any therapeutic advantage over metronidazole. Although the use of metronidazole on a global scale has been curtailed by newer agents for various infections, metronidazole still has a role for these and other therapeutic uses. Many clinicians still consider metronidazole to be the 'gold standard' antibiotic against which all other antibiotics with anaerobic activity should be compared.

Basics of surgical-site infection surveillance

Surgical-site infections, the third most common class of nosocomial infections, cause substantial morbidity and mortality and increase hospital costs. Surveillance programs can lead to reductions in surgical-site infection rates of 35% to 50%. Herein, we will discuss the practical aspects of implementing a hospital-based surveillance program for surgical-site infections. We will review surveillance methods, patient populations that should be screened, and interventions that could reduce infection rates.

The immune microenvironment of human fracture/soft-tissue hematomas and its relationship to systemic immunity

The immune environment of human soft-tissue injury is unstudied. We studied fracture soft-tissue hematomas (FxSTH) in 56 patients with high-energy bony fractures. FxSTH serum and mononuclear cells (MNC) as well as fracture patient plasma and blood MNC were studied. Twenty healthy controls donated plasma and MNC. Soluble tumor necrosis factor (TNF)-alpha, interleukin (IL-1 beta, IL-2, 6, 8, 10, 12, and interferon-gamma were studied by enzyme linked immunosorbent assay. Cells were studied by flow cytometry after cell-membrane stains for CD-14, TNF-alpha (mTNF), and human leukocyte antigen-DR, or intracellular stains for TNF (icTNF) and IL-10. Thirty-six patients with Injury Severity Score < 15 were analyzed further to evaluate the effects of isolated fracture on systemic immunity. Cytokines were rarely detectable in control plasma. TNF-alpha, IL-1 beta, IL-2, and interferon-gamma were rarely found in FxSTH serum or fracture patient plasma. All FxSTH sera were rich in IL-6, peaking before 48 hours (12,538 +/- 4,153 vs. 3,494 +/- 909 pg/mL, p = 0.02, U test). In Injury Severity Score < 15, IL-6 was not detectable in most early fracture patient plasma, but rose after 48 hours (p = 0.028). FxSTH serum IL-8 peaked after 48 hours (440 +/- 289 vs. 4,542 +/- 1,219 pg/mL, p = 0.006) and circulating IL-8 appeared after 72 hours. IL-6 and IL-8 showed gradients from FxSTH serum to paired PtS (p < 0.05, Wilcoxon). IL-10 was abundant (884 +/- 229 pg/mL) in FxSTH serum < 24 hours old. FxSTH serum IL-12 peaked late (3,323 +/- 799 pg/mL, day 4-7) then fell (p < 0.001, analysis of variance). Only IL-12 was higher in fracture patient plasma (1,279 +/- 602 pg/mL) than FxSTH serum (591 +/- 327 pg/mL) during the first 48 hours (p = 0.032, U test). On flow cytometry, control monocytes expressed 201 +/- 31 mTNF sites/cell, but icTNF was absent. mTNF was up-regulated after injury more in FxSTH monocytes (3,202 +/- 870 sites/cell) than peripheral blood monocytes (584 +/- 186 sites/cell) (p < 0.05 vs. peripheral blood monocytes by Wilcoxon, p < 0.001 vs. control monocytes by U test). Intracellular IL-10 was abundant in all MNC, but varied widely after injury. Fracture and peripheral blood monocytes expressed far less human leukocyte antigen-DR than control monocytes. Fractures create an inflammatory local environment. Proximal mediators are cell-associated and relatively confined to the wound, but soluble IL-6, IL-8, and IL-10 are abundant and probably exported. Systemic MNC have complex responses to local injuries. These may reflect the combined impact of multiple soluble cytokines initially generated within the wound. FxSTH appear to be a potentially important source of immunomodulatory cytokines in trauma.

Hypertonic saline resuscitation decreases susceptibility to sepsis after hemorrhagic shock

BACKGROUND

We hypothesized that improvements in cellular immune function after hypertonic saline (HTS) resuscitation will alter the outcome of sepsis after hemorrhage.

METHODS

To test this hypothesis, a two-hit model was used. Hemorrhage was induced in BALB/c mice by catheterizing the femoral artery and bleeding until a mean arterial pressure = 35 mm Hg was reached and maintained for 1 hour. Resuscitation was performed with HTS (NaCl 7.5%, 4 mL/kg) or lactated Ringer's (LR, twice the shed blood volume), plus the shed blood. Cecal ligation and puncture (CLP) was performed 24 hours after hemorrhage. Mortality was assessed for 72 hours, comparing HTS (n = 14) and LR (n = 13) resuscitation. Another set of animals (n = 10 in each group at each time point) were killed at 2 and 24 hours after blood collection. Liver and blood were cultured for the presence of bacteria, and lung and liver samples were scored on a scale from 0 (normal) to 4 (most severe) in a blind fashion by a pathologist.

RESULTS

Mortality 72 hours after CLP was 14.3% in HTS and 76.9% in LR treated animals (p < 0.002). At 24 hours after CLP, 44% of HTS, but 77% of LR treated animals had > 1,000 colony forming units/mL of blood. Positive liver cultures (> 100,000 colony forming units/g) also showed the same trend (HTS = 30%, LR = 60%). Autopsies revealed a better containment of the infection (abscess formation) in the HTS group. At 2 hours, lung scores were 1.2 +/- 0.25 and 2.6 +/- 0.31 for HTS and LR, respectively (p < 0.002). At 24 hours, HTS treated animals showed marked improvement of lung injury, while the scores in the LR group remained high. A significant difference was also observed regarding liver injury. At 2 hours, scores were 0.4 +/- 0.22 and 2.3 +/- 0.16 for HTS and LR, respectively (p < 0.002). At 24 hours, HTS treated animals showed normal hepatic architecture, although mild injury was still observed in the LR group.

CONCLUSION

HTS resuscitation leads to increased survival after hemorrhage and CLP. Marked improvements were observed in lung and liver injury compared with isotonic resuscitation. The better containment of the infection observed with HTS resuscitation corresponds to a marked decreased in bacteremia. HTS resuscitation stands as an alternative resuscitation regimen with immunomodulatory potential.

Risk factors leading to clinical failure in the treatment of intra-abdominal or skin/soft tissue infections

A study of determinants of outcome in adult patients with intra-abdominal or skin/soft tissue infections treated with cefotetan, cefoxitin, or ampicillin/sulbactam monotherapy was undertaken. Patients were matched for principal infectious process, surgery performed for the management of the infection, year of hospital admission, age, and sex. The criteria for inclusion, exclusion, and matching of patients and assignment of clinical and microbiological outcome were based on the 1992 Infectious Diseases Society of America/Federal Drug Administration guidelines for the evaluation of anti-infective drug products. One hundred and thirty-seven cases of intra-abdominal or skin and soft tissue infections treated with cefotetan (n = 47), cefoxitin (n = 43), or ampicillin/sulbactam (n = 47) monotherapy were selected without knowledge of outcome and analyzed using a single blinded analysis. The baseline characteristics did not differ between the treatment groups, nor did the rates of clinical or microbiological failure. A multivariate analysis showed that isolation of an organism resistant to the treatment regimen, including Pseudomonas spp., [odds ratio (OR) = 14.9, p = 0.001], being on antibiotic therapy at the time of admission (OR = 4.5, p = 0.007), and diagnosis of a complicated intra-abdominal infection (OR = 3.5, p = 0.014) were independently associated with clinical failure. These data support the assertion that antibiotic resistant organisms in mixed anaerobic/aerobic infections are associated with clinical failure and suggest that the antibiotic regimen should be modified to include Pseudomonas spp. in its spectrum when this organism is isolated from patients with such infections.

A randomized controlled study of the effect of bedside leucocyte depletion on the immunosuppressive effect of whole blood transfusion in patients undergoing elective colorectal surgery

In a randomized study the effect of whole blood transfusion versus bedside leucocyte-depleted blood transfusion on lymphocyte proliferation, CD4+:CD8+ ratio, and levels of soluble interleukin 2 receptor (sIL-2R) and interleukin (IL) 6, as well as on the development of postoperative wound infection and intra-abdominal abscess, was assessed in 60 patients undergoing elective colorectal surgery. Transfusion with whole blood induced a significant decrease in lymphocyte proliferation and CD4+ :CD8+ ratio (P < 0.01) as well as a significant increase in sIL-2R and IL-6 levels (P < 0.01). Furthermore, transfusion with whole blood was accompanied by a significant increase in postoperative infectious complications (P < 0.01). In patients transfused with leucocyte-depleted blood only slight and transient changes were observed, which were not significantly different from those observed in non-transfused patients.

Surgical infections: prevention and treatment--1965 to 1995

During the 30 year period from 1965-1995, significant advances have been made in the prevention, diagnosis, and management of surgical infections. To a great degree these advances have been provided by surgeons who developed a primary interest in this area. The Surgical Infection Society (SIS) was established in 1980 for surgeons and other physicians and scientists in order to better coordinate efforts in education and research concerning the infected surgical patient. The most significant of these advances were initially the accurate microbiologic definition of the human endogenous microflora in health and disease. Improvements in the techniques utilized to isolate and identity anaerobic microorganisms were of paramount importance. These lead to improvements in the choice of antibiotic agents for prophylaxis and treatment which resulted in improved clinical results. Most recently, emphasis has been placed on the perioperative identification of the high-risk patient who is more likely to develop infection in the postoperative period. By separating high-risk from low-risk patients in each operative procedure, rather than assuming their risk based on the traditional classification of surgical procedure, a more rationale plan of prospective alterations of treatment can be offered.