Body mass index and the prevalence of hypertension and dyslipidemia

OBJECTIVE

To describe and evaluate relationships between body mass index (BMI) and blood pressure, cholesterol, high-density lipoprotein-cholesterol (HDL-C), and hypertension and dyslipidemia.

RESEARCH METHODS AND PROCEDURES

A national survey of adults in the United States that included measurement of height, weight, blood pressure, and lipids (National Health and Nutrition Examination Survey III 1988-1994). Crude age-adjusted, age-specific means and proportions, and multivariate odds ratios that quantify the association between hypertension or dyslipidemia and BMI, controlling for race/ethnicity, education, and smoking habits are presented.

RESULTS

More than one-half of the adult population is overweight (BMI of 25 to 29.9) or obese (BMI of > or =30). The prevalence of high blood pressure and mean levels of systolic and diastolic blood pressure increased as BMI increased at ages younger than 60 years. The prevalence of high blood cholesterol and mean levels of cholesterol were higher at BMI levels over 25 rather than below 25 but did not increase consistently with increasing BMI above 25. Rates of low HDL-C increased and mean levels of HDL-C decreased as levels of BMI increased. The associations of BMI with high blood pressure and abnormal lipids were statistically significant after controlling for age, race or ethnicity, education, and smoking; odds ratios were highest at ages 20 to 39 but most trends were apparent at older ages. Within BMI categories, hypertension was more prevalent and HDL-C levels were higher in black than white or Mexican American men and women.

DISCUSSION

These data quantify the strong associations of BMI with hypertension and abnormal lipids. They are consistent with the national emphasis on prevention and control of overweight and obesity and indicate that blood pressure and cholesterol measurement and control are especially important for overweight and obese people.

Clarification of risk factors for abdominal operations in patients with hepatic cirrhosis

Celiotomy in cirrhotic patients is reported to bear a high risk of operative morbidity and mortality. We reviewed 100 consecutive, cirrhotic patients who underwent nonshunt celiotomy. Thirty patients died and major complications occurred in another 30 patients. Hospital mortality rate was 21% in 39 biliary operations, 35% in 26 procedures for peptic ulcer disease, and 55% in nine colectomies . Fifty-two variables were compared between survivors without complication, survivors with complications, and nonsurvivors. A computer-generated, multivariant discriminant analysis yielded an equation predictive of survival. Utilizing coagulation parameters, presence of active infection, and serum albumin, the equation predicted survival with 89% accuracy. In a similar fashion, amount of operative transfusions, absence of postoperative ascites, pulmonary failure, gastrointestinal bleeding, and culture-positive urine predicted survival with 100% accuracy. We conclude that celiotomy in the cirrhotic patient is truly associated with very high morbidity and mortality, and preoperative assessment can predict survival with 89% accuracy.

Regulation of intestinal blood flow

The gastrointestinal system anatomically is positioned to perform two distinct functions: to digest and absorb ingested nutrients and to sustain barrier function to prevent transepithelial migration of bacteria and antigens. Alterations in these basic functions contribute to a variety of clinical scenarios. These primary functions intrinsically require splanchnic blood flow at both the macrovascular and microvascular levels of perfusion. Therefore, a greater understanding of the mechanisms that regulate intestinal vascular perfusion in the normal state and during pathophysiological conditions would be beneficial. The purpose of this review is to summarize the current understanding regarding the regulatory mechanisms of intestinal blood flow in fasted and fed conditions and during pathological stress.

Malignant ascites. Clinical and experimental observations

Malignant ascites formation is a grave prognostic sign, but palliative efforts seem justified in some patients. Lack of knowledge concerning the natural history of this process hinders the choice of therapeutic options. Over 5 years, 107 patients with untreated malignant ascites were reviewed to define their survival. Pancreas (20), ovary (18), and colon (18) were the most frequent tumors, with 52% of patients presenting with ascites at the time of the initial cancer diagnosis. Cytology evaluation of the ascitic fluid was positive for tumor cells in 57% of cases and a high protein content was noted in 65%. Mean survival of the entire series was only 20 weeks from the time of diagnosis of ascites, with tumors of ovarian and lymphatic origin having better mean survivals of 32 and 58 weeks, respectively. Patients with high ascitic protein levels fared better than those with low levels. In an effort to explain this correlation of elevated protein levels and a favorable survival rate, a hypothesis was proposed that certain tumors secrete a factor, which alters vascular permeability and causes fluid accumulation in the absence of lymphatic obstruction. In an experimental rat model of malignant ascites, the intraperitoneal infusion of cell-free malignant ascitic fluid caused an increase in edema formation and a significant increase in capillary permeability to protein in the omentum. This demonstrated change in the leak of protein explains the formation of ascites by some tumors in the absence of tumor obstruction of the draining lymphatics of the peritoneal cavity and suggests another important mechanism in the genesis of malignant ascites.

Organ donor potential and performance: size and nature of the organ donor shortfall

OBJECTIVES

To estimate the potential for solid organ donation; to identify modifiable reasons for nondonation.

DESIGN

Retrospective medical records review.

SETTING

Sixty-nine acute care hospitals in four geographic areas of the United States in 1990, and a stratified random sample of 89 hospitals in three of the same areas and 33 of the same hospitals in 1993.

PATIENTS

PATIENTS < or = 70 yrs of age who were brain dead and medically suitable for donation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Standard forms were used to record patient demographic and hospital information. Reasons for nondonation were coded as "not identified," "family not asked," "consent denied," or "other." The main outcome measures were rate of donation and rates of nonidentification, not asking, and nonconsent. Organ donation occurred among 33% (299/916) of medically suitable cases identified in 1990 (95% confidence interval 30% to 36%). Ninety-four potential donors were not identified, 156 were not asked, 326 families denied consent, and 41 potential donors were categorized as "other," including patients who had suffered a cardiac arrest, and medical examiner prohibition of donation. In the 1993 study, organ donation occurred in an estimated 33% of suitable cases. In 1990, rates of donation were highest among patients <50 yrs of age, patients who died of traumatic causes, and non-Hispanic white patients. Logistic regression showed lower odds of donation for African American patients (odds ratio 0.38, 95% confidence interval 0.23 to 0.63) independent of potentially confounding hospital and patient variables (p=.0001). Donation rates did not vary by hospital size or type.

CONCLUSIONS

Despite legal and policy initiatives, only one third of potential donors became donors in 1990, with similar results in 1993. Extrapolating the 1990 findings to the United States suggests a pool of 13,700 medically suitable donors per year. Prospective identification and requesting donation in all suitable potential donor cases could lead to 1,800 additional donors per year.

Multivariate analysis of factors associated with postoperative pulmonary complications following general elective surgery

OBJECTIVE

To develop a predictive model identifying perioperative conditions associated with postoperative pulmonary complications (PPCs).

DESIGN

A prospective survey of patients whose preoperative history and physical examination, spirometric, PaO2 and PaCO2 analysis, and operative results were recorded. These patients underwent postoperative cardiopulmonary examinations until they were discharged from the hospital; their medical records were also reviewed until they were discharged from the hospital.

SETTING

The Louisville Veterans Administration Medical Center, Louisville, Ky.

PATIENTS

A randomly chosen sample of patients aged 40 years or older who required elective, nonthoracic surgery under general or spinal anesthesia and who were hospitalized at least 24 hours postoperatively.

MAIN OUTCOME MEASURE

An analysis of risk factors associated with the development of 1 or more of the following conditions: acute bronchitis, bronchospasm, atelectasis, pneumonia, adult respiratory distress syndrome, pleural effusion, pneumothorax, prolonged mechanical ventilation, or death secondary to acute respiratory failure.

RESULTS

Postoperative pulmonary complications developed in 16 (11%) of 148 patients. The risk factors found to be higher among those with PPCs compared with those without PPCs were postoperative nasogastric intubation (81% vs 16%, P<.001), preoperative sputum production (56% vs 21%, P=.005), and longer anesthesia duration (480 vs 309 minutes, P<.001). Upper abdominal surgery was performed in 11 (69%) of the 16 patients with PPCs and in 20 (15%) of the 132 patients without PPCs (P<.001); this difference lost significance in multivariate analysis. The final linear logistic model included postoperative nasogastric intubation (odds ratio [OR], 21.8), preoperative sputum production (OR, 4.6), and longer anesthesia duration (OR exp[0.01x] for an increase in x minutes) (1 minute of additional anesthesia time increases the OR to 1.01), resulting in 92% accuracy in predicting PPCs.

CONCLUSIONS

We identified 3 potentially modifiable risk factors for PPCs. If validated, our results may lead to modifications of perioperative care that will further reduce PPCs.

Enterococcal bacteremia: clinical implications and determinants of death

The pathogenicity of the enterococcus remains controversial despite recognition of this organism in inflammatory exudates. A review of 114 patients with 123 bacteremic events with enterococcus from all hospital services was undertaken. A total of 46% were in the perioperative period. The clinical indications for blood culture varied, but only 19 patients had septic shock at the time. Employing three or more associated diseases as a definition, 71 patients were considered chronically ill. The primary sources of bacteremia were commonly urinary tract (22), soft tissue (17), and intra-abdominal (12). An impressive total of 48 patients had no discernible primary focus of infection. Except for the urinary tract, infections tended to be polymicrobial; 51 patients had associated synchronous or metachronous polymicrobial bacteremias. Antibiotic therapy appropriate for enterococcus did not favorably influence outcome. By chi-square analysis, patients with urinary tract and soft tissue infections had significantly better survival rates than the group as a whole, while patients with intra-abdominal sepsis, polymicrobial bacteremia, or an unknown focus of infection did statistically worse. Enterococcal bacteremia results in a high mortality (54%); its frequent identification with other facultative and anaerobic organisms may indicate that it has a synergistic role; the frequency of unexplained bacteremias stimulates speculation that primary bacteremia from the gastrointestinal tract may be a plausible explanation.

Obesity, inflammation, and the potential application of pharmaconutrition

Obesity is an emerging problem worldwide. Hospitalized obese patients often have a worse outcome than patients of normal weight, particularly in the setting of trauma and critical care. Obesity creates a low-grade systemic inflammatory response syndrome (SIRS) that is similar (but on a much smaller scale) to gram-negative sepsis. This process involves up-regulation of systemic immunity, is characterized clinically by insulin resistance and the metabolic syndrome, and puts the patient at increased risk for organ failure, infectious morbidity, and mortality. Through lipotoxicity and cytokine dysregulation, obesity may act to prime the immune system, predisposing to an exaggerated subsequent immune response when a second clinical insult occurs (such as trauma, burns, or myocardial infarction). Specialized nutrition therapy for such patients currently consists of a hypocaloric, high-protein diet. However, this approach does not address the putative pathophysiologic mechanisms of inflammation and altered metabolism associated with obesity. A number of dietary agents such as arginine, fish oil, and carnitine may correct these problems at the molecular level. Pharmaconutrition formulas may provide exciting innovations for the nutrition therapy of the obese patient.

Poor outcome from peritonitis is caused by disease acuity and organ failure, not recurrent peritoneal infection

OBJECTIVE

The purpose of the study is to determine whether organ failure develops in patients despite control of peritoneal infection and whether the process is, in part, neutrophil (polymorphonuclear leukocyte [PMN]) mediated.

SUMMARY BACKGROUND DATA

Peritonitis generally responds to prompt surgical intervention and systemic antibiotics; however, some patients continue a septic course and progress to organ failure and death.

METHODS

One hundred five consecutive patients with peritonitis between 1988 and 1996 who required operation and a postoperative hospital stay greater than 10 days were studied. Mice were injected with a monoclonal anti-PMN antibody 24 hours before cecal ligation and puncture (CLP) to deplete PMNs.

RESULTS

Thirty-eight patients died, and all but 1 had identified organ failure. Seventy-seven patients had either pulmonary failure alone (25 patients) or as a component of multisystem organ failure (52 patients). All but one of these patients showed resolution of their intraperitoneal infection as evident by clinical course, abdominal computed tomographic scan, second-look laparotomy, or autopsy. Recurrent intra-abdominal infection developed in 15 patients, but only 1 had organ failure, and 2 died. At 18 hours after CLP, lung injury, PMN content, interleukin-1 mRNA expression, and liver injury were significantly reduced by anti-PMN treatment, whereas serum endotoxin levels actually increased.

CONCLUSIONS

Disease acuity and organ failure, and not recurrent peritoneal infection, are the major causes of adverse outcome in patients with peritonitis. The authors' experimental data indicate that such organ injury is, in part, PMN mediated but not endotoxin mediated. Attraction of PMNs toward the site of primary infection, and thereby away from remote organs, is a logical future therapeutic approach in such patients who are critically ill with peritonitis.

Alcoholism and occupations: a review and analysis of 104 occupations

A review of the many attempts to establish an association between occupations and alcoholism reveals that most do not deal with data about clinically defined alcoholism but instead use data about cirrhosis mortality, self-reported alcohol problems, and frequent and heavy drinking. The present study establishes an association between occupations and diagnoses of Alcohol Dependence Disorder and Alcohol Abuse Disorder, using data from a large population-based household interview study. Statistical adjustment using logistic methods reveals that apparent associations between occupations and alcohol-related disorders previously reported in the literature are due to characteristics of those employed in various occupations. The prevalence of alcohol dependence and abuse in two high risk industries, construction and transportation, is confirmed. More than one in four construction laborers and one in five skilled construction trades workers received a DIS/DSM-III diagnosis related to alcohol abuse. In the transportation industry one in six heavy truck drivers and material movers received an alcohol diagnosis. Analyses of the data from individuals currently employed and not employed in their occupation reveals reduction in risk for those who leave some occupations and increased risk for those who leave other occupations. Evidence is presented that employment in some occupations may be protective for Alcohol Dependence. The findings support the view that occupation may be associated with Alcohol Dependence and Alcohol Abuse independent of demographic variations. Previously proposed explanatory models for associations between occupations and alcohol problems are called into question because they do not take into account the demographic characteristics and employment status of workers.

Candida sepsis. Implications of polymicrobial blood-borne infection

Eighty-three patients with 117 episodes of candidemia were reviewed to examine the clinically significant variables and the results of treatment for this problem. Mortality was 52%. Patients who had bacteremia either synchronously or metachronously in association with Candida species had poorer survival rates. Staphylococcal and enterococcal species were the most frequently associated bacteria. Patients with Candida parapsilosis had better survival rates than patients with other species. Portals of entry for fungemia were catheters, wounds, the urinary tract, and the peritoneal cavity, but were undefined in 54% of patients. Antifungal chemotherapy could not be identified as affecting the outcome in these patients. It is suggested that candidemia in most patients represents a failure of host defense, and that septicemia of either bacteria or fungi may arise from the gastrointestinal tract in critically ill, immunocompromised patients.

Intensive surveillance of femoropopliteal-tibial autogenous vein bypasses improves long-term graft patency and limb salvage

OBJECTIVE

The authors determined the impact of an intensive surveillance program of autogenous vein bypasses on patency and limb salvage.

SUMMARY BACKGROUND DATA

Surveillance protocols of vein bypasses can identify graft-threatening lesions to permit elective revisions before thrombosis. The authors compared follow-up based on clinically indicated procedures with intensive surveillance.

METHODS

From 1985 to 1994, 615 autogenous vein bypasses (454 in situ, 161 reversed/composite) to popliteal (n = 169) and tibial (n = 446) arteries were performed for critical limb ischemia (n = 507), claudication (n = 88), and popliteal aneurysm (n = 20). Intensive surveillance of autogenous vein bypasses consisted of ankle brachial index and duplex scan with graft velocities measured at 1 month, 3 months, 6 months, and every 6 months subsequently. After surgery 317 bypasses had intensive surveillance, 222 bypasses were clinically indicated for follow-up, and 76 bypasses were excluded because follow-up or patency was less than 31 days.

RESULTS

Primary patency at 5 years was similar for bypasses treated by intensive surveillance (56%) and those treated with clinically indicated procedures (67%). Secondary patency and limb salvage at 5 years was significantly improved (p < 0.02) for bypasses followed by intensive surveillance (80% and 94%) compared with clinically indicated procedures (67% and 73%). Revision of patent bypasses was higher (p < 0.000001) for bypasses treated by intensive surveillance (61 of 70, 87%) compared with those treated with clinically indicated procedures (9 of 34, 26%). Secondary patency at 2 years was significantly higher (p < 0.02) for revision of patent bypasses (79%) compared with thrombosed bypasses (55%).

CONCLUSIONS

Long-term autogenous vein bypass patency and limb salvage is significantly improved by intensive surveillance, permitting identification and correction of graft threatening lesions before thrombosis.

Occupational characteristics and the occurrence of psychotic disorders

This study was undertaken to investigate whether individuals working under various occupational stressors are at increased risk of three forms of psychotic conditions. This paper presents prospective analyses of antecedent occupational stressors in psychotic conditions with interview data from a community sample in five US metropolitan areas--the NIMH Epidemiologic Catchment Area Program. Three non-overlapping conditions were defined using DSM-III definitions as assessed by the Diagnostic Interview Schedule (DIS): (1) DSM-III schizophrenia criterion A; (2) full schizophrenia; and (3) criterion A and affective episode. Artistic (RR = 3.32, 95% CI 1.08-10.14) and construction trades occupations (RR = 2.58, 95% CI 1.15-5.77), "noisome working conditions" occupations (RR = 1.20, 95% CI 0.99-1.47) and physically demanding occupations (RR = 1.39, 95% CI 1.05-1.72) were associated with increased risk of developing DIS/DSM-III schizophrenia criterion A, even after adjustment for sociodemographic and psychopathology factors including alcohol and marijuana use. Psychologically demanding occupations (RR = 0.85, 95% CI 0.75-0.95) were associated with decreased risk of developing DIS/DSM-III schizophrenia. This finding is supported by results from experimental studies on the arousability of pre-schizophrenics. Finally, teachers (RR = 11.35, 95% CI 2.56-50.38), sales occupations (RR = 4.16, 95% CI 1.00-21.30) and occupations characterized by low control over work were associated with increased risk of developing DIS criterion A and affective episode, resembling previous findings on occupational stressors and depression. Overall, our results replicate and extend previous work on occupational stressors and psychotic conditions through use of prospective data, several psychotic conditions, multiple assessment of occupational stressors and adjustment for potential confounders.

Occupations and the prevalence of major depressive disorder

The prevalence of depression has rarely been studied in a manner permitting comparisons across a range of occupations. This analysis reveals considerable range in prevalence in 104 occupations of major depressive disorder as defined by the Diagnostic and Statistical Manual (ed 3), and measured by the National Institute of Mental Health's Diagnostic Interview Schedule. Five occupations had prevalence rates above 10%. When adjusted for sociodemographic factors, three occupations yield prevalences with statistically significant elevations in the rate, compared with employed persons generally. The three are lawyers, with an odds ratio of 3.6; other teachers and counselors, with an odds ratio of 2.8; and secretaries, with an odds ratio of 1.9. Exploration of possible sources of these differences concludes the paper.

Microvascular changes explain the "two-hit" theory of multiple organ failure

OBJECTIVE

The objective was to determine intestinal microvascular endothelial cell control after sequential hemorrhage and bacteremia.

SUMMARY BACKGROUND DATA

Sepsis that follows severe hemorrhagic shock often results in multiple system organ failure (MSOF) and death. The sequential nature of this clinical scenario has led to the idea of a "two-hit" theory for the development of MSOF, the hallmark of which is peripheral vasodilation and acidosis. Acute bacteremia alone results in persistent intestinal vasoconstriction and mucosal hypoperfusion. Little experimental data exist to support the pathogenesis of vascular dysregulation during sequential physiologic insults. We postulate that hemorrhagic shock followed by bacteremia results in altered microvascular endothelial cell control of dilation and blood flow.

METHODS

Rats underwent volume hemorrhage and resuscitation. A sham group underwent the vascular cannulation without hemorrhage and resuscitation, and controls had no surgical manipulation. After 24 and 72 hours, the small intestine microcirculation was visualized by in vivo videomicroscopy. Mean arterial pressure, heart rate, arteriolar diameters, and A1 flow by Doppler velocimetry were measured. Endothelial-dependent dilator function was determined by the topical application of acetylcholine (ACh). After 1 hour of Escherichia coil bacteremia, ACh dose responses were again measured. Topical nitroprusside was then applied to assess direct smooth muscle dilation (endothelial-independent dilator function) in all groups. Vascular reactivity to ACh was compared among the groups.

RESULTS

Acute bacteremia, with or without prior hemorrhage, caused significant large-caliber A1 arteriolar constriction with a concomitant decrease in blood flow. This constriction was blunted at 24 hours after hemorrhage but was restored to control values by 72 hours. There was a reversal of the response to bacteremia in the premucosal A3 vessels, with a marked dilation both at 24 and 72 hours. The sequence of hemorrhage and E. coli resulted in a progressive enhanced reactivity to the endothelial-dependent stimulus of ACh in the A3 vessels at 24 and 72 hours. Reactivity to endothelial-independent smooth muscle relaxation and subsequent vessel dilation was similar for all groups.

CONCLUSIONS

These data indicate that there is altered endothelial control of the intestinal microvasculature after hemorrhage in favor of enhanced dilator mechanisms in premucosal vessels with enhanced constrictor forces in inflow vessels. This enhanced dilator sensitivity is most evident in small premucosal vessels. This experimental finding supports the premise that an initial pathophysiologic stress alters the subsequent microvascular blood flow responses to systemic inflammation. These changes in the intestinal microcirculation are in concert with the "two-hit" theory for MSOF.

Selective microvascular endothelial cell dysfunction in the small intestine following resuscitated hemorrhagic shock

Following resuscitation (RES) from hemorrhagic shock (HEM), intestinal microvessels develop progressive vasoconstriction that impairs mucosal blood flow, despite central hemodynamic RES. These events might have clinical consequences secondary to occult intestinal ischemia. We hypothesized that the microvascular impairments were due to progressive endothelial cell dysfunction and an associated reduction in the dilator, nitric oxide (NO), following HEM/RES. Male Sprague-Dawley rats, were monitored for central hemodynamics and the terminal ileum was studied with in vivo videomicroscopy. HEM was 50% of baseline mean arterial pressure (MAP) for 60 min, and RES was with shed blood + 1 volume of normal saline (NS). Following HEM/RES, acetylcholine (10)(-7), 10(-5) M) was topically applied and ileal inflow (A1) and premucosal arteriolar diameters were measured to assess endothelial-cell function at 60 and 120 min post-RES. Normalization of MAP, cardiac output, and heart rate demonstrated adequate systemic resuscitation. Post-RES vasoconstriction developed in A1 (-25%) and premucosal (-28%) arterioles with an associated reduction in A1 flow (-47%). However, there was a selective impairment of endothelial-dependent dilation that was manifested only in the smaller premucosal arterioles and not in the inflow, A1 arterioles. This suggests that multiple mechanisms are involved in the development of the post-RES vasoconstriction. The premucosal response was likely mediated by endothelial cell dysfunction, while the A1 response was probably the result of enhanced vasoconstrictor forces. This early microvascular dysfunction might contribute to the late sequelae of intestinal ischemia and might alter microvascular responses to subsequent systemic insults.

Nitric oxide synthase inhibition aggravates intestinal microvascular vasoconstriction and hypoperfusion of bacteremia

Nitric oxide (NO) is an important hemodynamic mediator of sepsis; however, its visceral microcirculatory effects are largely unknown. To determine the role of systemic nitric oxide synthase (NO-S) inhibition on the microcirculation of the small intestine (SI), an intact loop of SI was exteriorized from decerebrate rats into a controlled tissue bath. Videomicroscopy was used to measure arteriolar diameters (A1, A3) and optical Doppler velocimetry was used to quantitate flow. In nonbacteremic controls inhibition of NO-S by N omega-nitro-L-arginine methyl ester (L-NAME; 1 mg/kg IV) caused vasoconstriction (A1 = -7%; A3 = -24% baseline values) and reduced A1 flow by 26%. Bacteremic controls received 10(9) Escherichia coli IV, which resulted in arteriolar constriction and hypoperfusion (A1 = -16%; A3 = -21%; A1 flow = -44%), despite increased cardiac output (+33%). Treatment of bacteremic rats with L-NAME corrected the increased cardiac output (-3%), but exacerbated vasoconstriction (A1 = -24%; A3 = -27%) and did not improve A1 flow (-49%). These data indicate that (1) NO mediates basal microvascular tone of the SI; (2) hyperdynamic bacteremia causes arteriolar constriction and hypoperfusion of the SI; and (3) although systemic NO-S inhibition normalizes cardiac output and increases blood pressure, it aggravates vasoconstriction in the SI and does not improve hypoperfusion.

Complement inhibition prevents gut ischemia and endothelial cell dysfunction after hemorrhage/resuscitation

BACKGROUND

Complement, a nonspecific immune response, is activated during hemorrhage/resuscitation (HEM/RES) and is involved in cellular damage. We hypothesized that activated complement injures endothelial cells (ETCs) and is responsible for intestinal microvascular hypoperfusion after HEM/RES.

METHODS

Four groups of rats were studied by in vivo videomicroscopy of the intestine: SHAM, HEM/RES, HEM/RES + sCR1 (complement inhibitor, 15 mg/kg intravenously given before resuscitation), and SHAM + sCR1. Hemorrhage was to 50% of mean arterial pressure for 60 minutes followed by resuscitation with shed blood plus an equal volume of saline. ETC function was assessed by response to acetylcholine.

RESULTS

Resuscitation restored central hemodynamics to baseline after hemorrhage. After resuscitation, inflow A1 and premucosal A3 arterioles progressively constricted (-24% and -29% change from baseline, respectively), mucosal blood flow was reduced, and ETC function was impaired. Complement inhibition prevented postresuscitation vasoconstriction and gut ischemia. This protective effect appeared to involve preservation of ETC function in the A3 vessels (SHAM 76% of maximal dilation, HEM/RES 61%, HEM/RES + sCR1 74%, P < .05).

CONCLUSIONS

Complement inhibition preserved ETC function after HEM/RES and maintained gut perfusion. Inhibition of complement activation before resuscitation may be a useful adjunct in patients experiencing major hemorrhage and might prevent the sequelae of gut ischemia.

Skeletal microcirculatory responses to hyperdynamic Escherichia coli sepsis in unanesthetized rats

To determine the microvascular site of vasodilation during hyperdynamic sepsis, we measured arteriolar and venular responses to live Escherichia coli bacteremia in the rat cremaster muscle by direct in vivo videomicroscopy. Our data indicate that cardiac output (by thermodilution) increased, systemic vascular resistance decreased, and a differential arteriolar response occurred, with constriction of large arterioles and dilation of small terminal arterioles. We conclude that dilation of small terminal arterioles in skeletal muscle could contribute to decreased systemic vascular resistance during hyperdynamic sepsis. This may be an appropriate response to increased oxygen demand or decreased tissue utilization of oxygen. Alternatively, small-arteriole dilation may be an inappropriate response and secondary to release of vasoactive inflammatory mediators. If the latter is true, there is a potential therapeutic role for selective manipulation of the tone of small terminal arterioles in hyperdynamic sepsis.

Intestinal blood flow is restored with glutamine or glucose suffusion after hemorrhage

Intestinal blood flow has been shown to be impaired after resuscitated hemorrhagic shock. Enteral feeding has been proposed as an adjunct for preserving mucosal integrity and decreasing translocation-related morbidities during stress. The purpose of this study was to determine if an ileal mucosal suffusion with an isotonic glucose or glutamine solution begun after resuscitation would prevent development of this blood flow impairment. The distal ileum of anesthetized Sprague-Dawley rats was prepared for in vivo videomicroscopy. Animals were bled to 50% of baseline blood pressure for 60 min and then resuscitated with their shed blood and an equal volume of lactated Ringer's. After resuscitation was complete, the mucosa was suffused with isotonic glucose, glutamine, or saline (control). Resuscitation restored cardiac output and mean arterial pressure to baseline in all groups; however, first-order arteriolar blood flow remained 50% below baseline in the saline group. Glucose-treated animals demonstrated a 34% increase over baseline in first-order arteriolar blood flow 120 min after resuscitation due to submucosal and previllus arteriolar dilation. This effect became evident 30 min after initiating the suffusion, suggesting an effect mediated via locally generated vasodilators. Glutamine suffusion attenuated the flow impairment by dilation of previllus arterioles but to a lesser degree than that observed in glucose-treated animals. These data demonstrate that mucosal suffusion with an isotonic glucose solution overrides the residual effects of hemorrhagic shock on the intestinal microcirculation and suggest a mechanism for preserving mucosal integrity with the addition of glutamine to standard enteral formulations.

Altered intestinal microcirculation is the critical event in the development of necrotizing enterocolitis

PURPOSE

The pathophysiology of necrotizing enterocolitis (NEC) includes prematurity, enteral feeds, hypoxia, and hypothermia. We hypothesized that vasoconstriction of the neonatal intestinal microvasculature is the essential mechanistic event in NEC and that these microvascular changes correlate with alterations in mediators of inflammation.

METHODS

Sprague-Dawley rat pups were separated into groups by litter. Necrotizing enterocolitis was induced in experimental groups, whereas control animals were delivered vaginally and dam fed. Neonatal pups underwent intravital videomicroscopy of the terminal ileum with particular attention to the inflow and premucosal arterioles. Reverse transcriptase-polymerase chain reaction was performed to evaluate for messenger RNA of mediators of inflammation.

RESULTS

Necrotizing enterocolitis animals demonstrated statistically significant smaller inflow and premucosal arterioles than control animals (P < .05). Necrotizing enterocolitis animals had an altered intestinal arteriolar flow with a distinct "stop-and-go" pattern, suggesting severe vascular dysfunction. Reverse transcriptase-polymerase chain reaction confirmed elevation of Toll-like receptor 4 (P = .01) and high-mobility group box protein 1 (P = .001) in the ileum of animals with NEC.

CONCLUSION

Intestinal arterioles were significantly smaller at baseline in animals with NEC compared with controls, and expression of inflammatory mediators was increased in animals with NEC. This represents a novel method of defining the pathophysiology of NEC and allows real-time evaluation of novel vasoactive strategies to treat NEC.

Pedal or peroneal bypass: which is better when both are patent?

PURPOSE

We compared autogenous vein pedal and peroneal bypasses, focusing on extremities that could have a bypass to either artery.

METHODS

From 1985 to 1993 we performed a total of 175 pedal and 77 peroneal autogenous vein bypasses for rest pain (n = 75, 30%) and tissue loss (n = 177, 70%). One hundred ninety-six (78%) in situ saphenous vein and 56 (22%) reversed or composite vein bypasses were performed. One hundred fifty-two of these 252 bypasses were performed in extremities with both the pedal and peroneal arteries patent by arteriography. The vascular surgeon chose to perform 99 pedal and 53 peroneal vein bypasses in these 152 extremities.

RESULTS

The angiogram score of the outflow arteries were similar for pedal and peroneal bypasses with the Society for Vascular Surgery and the International Society for Cardiovascular Surgery and modified scoring systems. At 2 years the primary and secondary patency rates for pedal bypasses (70% and 77%) were not significantly different compared with those for peroneal bypasses (60% and 72%). Limb salvage rates at 2 years were similar for pedal and peroneal bypasses for all patients (74% and 73%), patients with both pedal and peroneal arteries patent (83% and 72%), diabetics (76% and 66%), and patients with tissue necrosis (77% and 71%).

CONCLUSIONS

Pedal and peroneal artery bypasses with equivalent angiogram scores have similar long-term graft patency and limb salvage. The choice between pedal or peroneal artery bypass should be based on the quality of vein and the surgeon's preference.

Pulmonary infection complicating intra-abdominal sepsis: clinical and experimental observations

Pulmonary infection complicating intra-abdominal abscess is a major clinical problem. One hundred and forty-three patients with abdominal abscesses were reviewed; 41 had associated pneumonia by strictly defined criteria. The causative organisms for the pneumonia were Pseudomonas (35), Klebsiella (20), and Enterobacter (16), while abdominal infections were caused by Escherichia coli (22), Klebsiella (21), and Enterococcus (18). The temporal and bacteriologic relationship between the abdominal and pulmonary infection suggested that decreased pulmonary host defenses might be operative in the high incidence of pneumonia observed. An experimental model for intra-abdominal abscess was created using cecal ligation in the rat. Animals with an abdominal abscess had a marked depression of their ability to clear E. coli and Pseudomonas aeruginosa that were injected into the airway. Macrophages from infected animals did not differ in quantity or viability when compared with those in control animals. The ability to ingest bacteria appeared to be normal or enhanced in infected animals, but there was a significant decrease in the ability of the macrophage to kill the ingested organisms. Such macrophage defects may be partially responsible for the infected animals' inability to clear bacteria in a normal manner.

Mechanisms of malignant ascites production

The accumulation of malignant ascites is determined primarily by the obstruction of diaphragmatic lymphatics with tumor inhibiting the outflow of peritoneal fluid. An abnormal increase in peritoneal fluid production has been shown to contribute to ascites formation by a marked neovascularization of the parietal peritoneum. Cell-free malignant ascitic fluid obtained from rats with intra-abdominal Walker 256 carcinoma when infused into the peritoneal cavities of normal animals causes an increase in edema formation and an increase in the permeability of protein from normal omental vessels. Protamine sulfate, a known inhibitor of angiogenesis when infused into the peritoneal cavity along with cell free malignant ascitic fluid, significantly reduces the leak of protein from the intravascular space when compared to ascites alone. Persistent permeability changes continue to exist even after the inhibition of vessel proliferation. These results indicate that angiogenesis is responsible for a major portion of the increase in permeability caused by malignant ascitic fluids. Other tumor-induced factors may be present which alter vascular permeability by other mechanisms which remain to be elucidated.

Pentoxifylline but not saralasin restores hepatic blood flow after resuscitation from hemorrhagic shock

After determining that hepatic blood flow remains impaired after resuscitation from hemorrhagic shock, we used the angiotensin II receptor antagonist saralasin and pentoxifylline to investigate their respective effects on hepatic blood flow responses after resuscitation from hemorrhagic shock. Rats were bled to 50% of baseline blood pressure for 60 min and resuscitated with shed blood and an equal volume of lactated Ringer's solution. Saralasin [10 micrograms/kg per min (n = 6)], pentoxifylline [25 mg/kg bolus and 12.5 mg/kg per hr (n = 7)], or saline (n = 11) were started with the onset of resuscitation. Total hepatic blood flow measured by ultrasonic transit time flow meter, effective nutrient hepatic blood flow measured by galactose clearance, mean arterial pressure, and cardiac output were recorded at 15-min intervals for 2 hr after resuscitation. Hemorrhage decreased cardiac output 57% below baseline and decreased total hepatic blood flow 64% below baseline. Resuscitation restored cardiac output to baseline levels in all three groups. Despite restoration of cardiac output, total hepatic and effective hepatic blood flow remained significantly below baseline in the saline control and saralasin groups but was restored to baseline levels in the pentoxifylline group. These data indicate that angiotensin II does not contribute significantly to the hepatic blood flow impairment after resuscitation from hemorrhagic shock. Improvement in flow with pentoxifylline implies that hemorrhage and resuscitation impair hepatic microvascular hemorrheology and that addition of pentoxifylline to standard resuscitation corrects the impairment.