Role of FDG-PET in the evaluation and staging of hepatocellular carcinoma with comparison of tumor size, AFP level, and histologic grade

Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has proven to be a valuable tool in the initial diagnosis, staging, and restaging of a variety of cancers. The potential use of FDG-PET in the evaluation and management of hepatocellular carcinoma (HCC) continues to evolve. The purpose of this study was to investigate the effectiveness of FDG-PET for the detection and staging of HCC. In addition, we also assessed the correlation between FDG-PET positivity, tumor size, a-fetal protein level (AFP), and histologic grade. All patients on the hepatobiliary and liver transplant service with biopsy proven HCC that underwent FDG-PET between January 2000 and December 2004 were selected for a retrospective review. Results of the FDG-PET scan were compared with other imaging studies [computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography], intraoperative findings, tumor size, AFP levels, and histologic grade. Of the 20 patients who underwent 18F-FDG PET, increased FDG uptake was noted in 14 scans (70%). These 20 patients fell into 2 groups: 1 for detecting HCC (Group A) and 1 for staging HCC (Group B). There were 7 patients in Group A; only 2 scans (28.6%) showed increased uptake. There were 13 patients in Group B; 12 scans (92.3%) showed increased uptake. In Group B, 11 of the 13 scans (84.6%) provided an accurate representation of the disease process. Two scans failed to accurately portray the disease; one scan failed to show any increase in uptake, and the other scan failed to detect positive nodes that were found during surgery. FDG-PET detected only 2 of 8 tumors (25%) < or = 5 cm in size. All 12 PET scans (100%) in tumors > or = 5 cm and/or multiple in number were detected by FDG-PET. FDG-PET scans with AFP levels < 100 ng/ml were positive in 5 of 9 patients (55.6%). In patients with levels > 100 ng/ml, 6 of 7 patients (85.7%) had positive scans. Histologically, there were 6 well-differentiated, 6 moderately differentiated, and 2 poorly differentiated HCCs. FDG-PET detected 4 of 6 for both well- and moderately differentiated HCCs. Both poorly differentiated HCCs were detected. The intensity was evenly distributed between the different histologic grades. There was a strong correlation of FDG uptake with tumor size. There were 5 HCCs with primary tumors >10 cm in size; 4 showed intense uptake on the scan. In contrast, of the 8 tumors < or = 5 cm in size, 6 were negative for uptake. The sensitivity of FDG-PET in detecting HCC < or = 5 cm in size is low and therefore may not be helpful in detecting all of these tumors. For larger tumors, there is a strong correlation of sensitivity and uptake intensity with tumor size and elevated AFP levels. FDG-PET sensitivity and uptake intensity did not correlate with histologic grade. In the setting of extrahepatic disease, FDG-PET seems to be an effective accurate method for HCC staging; however, whether PET offers any benefit over traditional imaging has yet to be determined.

Comparison of surgical outcomes between teaching and nonteaching hospitals in the Department of Veterans Affairs

OBJECTIVE

To determine whether the investment in postgraduate education and training places patients at risk for worse outcomes and higher costs than if medical and surgical care was delivered in nonteaching settings.

SUMMARY BACKGROUND DATA

The Veterans Health Administration (VA) plays a major role in the training of medical students, residents, and fellows.

METHODS

The database of the VA National Surgical Quality Improvement Program was analyzed for all major noncardiac operations performed during fiscal years 1997, 1998, and 1999. Teaching status of a hospital was determined on the basis of a background and structure questionnaire that was independently verified by a research fellow. Stepwise logistic regression was used to construct separate models predictive of 30-day mortality and morbidity for each of seven surgical specialties and eight operations. Based on these models, a severity index for each patient was calculated. Hierarchical logistic regression models were then created to examine the relationship between teaching versus nonteaching hospitals and 30-day postoperative mortality and morbidity, after adjusting for patient severity.

RESULTS

Teaching hospitals performed 81% of the total surgical workload and 90% of the major surgery workload. In most specialties in teaching hospitals, the residents were the primary surgeons in more than 90% of the operations. Compared with nonteaching hospitals, the patient populations in teaching hospitals had a higher prevalence of risk factors, underwent more complex operations, and had longer operation times. Risk-adjusted mortality rates were not different between the teaching and nonteaching hospitals in the specialties and operations studied. The unadjusted complication rate was higher in teaching hospitals in six of seven specialties and four of eight operations. Risk adjustment did not eliminate completely these differences, probably reflecting the relatively poor predictive validity of some of the risk adjustment models for morbidity. Length of stay after major operations was not consistently different between teaching and nonteaching hospitals.

CONCLUSION

Compared with nonteaching hospitals, teaching hospitals in the VA perform the majority of complex and high-risk major procedures, with comparable risk-adjusted 30-day mortality rates. Risk-adjusted 30-day morbidity rates in teaching hospitals are higher in some specialties and operations than in nonteaching hospitals. Although this may reflect the weak predictive validity of some of the risk adjustment models for morbidity, it may also represent suboptimal processes and structures of care that are unique to teaching hospitals. Despite good quality of care in teaching hospitals, as evidenced by the 30-day mortality data, efforts should be made to examine further the structures and processes of surgical care prevailing in these hospitals.

FAK induction in keratinocytes in an in vitro model of reepithelialization

During reepithelialization, keratinocytes must become activated in order to migrate over the provisional extracellular matrix of the wound. Previously we have shown that focal adhesion kinase (FAK) is induced in activated keratinocytes. The mechanisms responsible for keratinocyte activation are unknown. Here we use an organ culture system to investigate FAK up-regulation and regulation of keratinocyte activation. Normal human skin was cultured on type I collagen. Keratinocytes migrated out of the explant onto the supporting collagen. Immunostaining for FAK showed induction in the migrating epithelium and also in the center of the explant some distance from the cut edge. Cells from the center of the explant expressed FAK and showed the activated phenotype as defined by their ability to spread on collagen. Since FAK is a tyrosine kinase, the tyrosine kinase inhibitors genistein or herbimycin A were added to the explant medium for 24 h. Inhibition of tyrosine kinase activity delayed epithelial migration, but keratinocytes were able to begin migrating after removal of the inhibitors. We conclude that FAK is up-regulated in keratinocytes in this whole skin explant model. Furthermore FAK up-regulation and keratinocyte activation are not confined to the migrating cells but are found in cells some distance from the skin margin. These data suggest that (1) cell migration, contact with wound matrix molecules, loss of cell-cell contact, or loss of basement membrane contact is not necessary for FAK up-regulation or keratinocyte activation; and (2) tyrosine kinase signaling pathways are important for reepithelialization.

The diagnostic accuracy of mammography in the evaluation of male breast disease

BACKGROUND

The role of mammography in the evaluation of male patients presenting with breast disease is controversial. This controversy is a function of the lack of specific data concerning the diagnostic accuracy of mammography when used in this clinical setting. The purpose of this study was to define the diagnostic accuracy of mammography in the evaluation of male breast disease.

METHODS

One hundred and four prebiopsy mammograms from 100 patients with tissue diagnoses were read blindly by two independent radiologists, and placed into one of five predetermined categories: definitely malignant, possibly malignant, gynecomastia, benign mass, and normal. Radiologic/pathologic correlation was performed and the sensitivity (Sn), specificity (Sp), positive (Ppv) and negative predictive value (Npv), and accuracy (Ac) for each of the mammographic diagnostic category determined.

RESULTS

The pathologic diagnoses were 12 cancers, including 1 patient with bilateral breast cancer, 70 cases of gynecomastia, 16 benign masses, and 6 normals. The accuracy data for the mammographic diagnostic categories are as follows: malignant (combined definitely and possibly malignant), Sn 92%, Sp 90%, Ppv 55%, Npv 99%, Ac 90%; and overall benignity (combined gynecomastia, benign mass, and normal), Sn 90%, Sp 92%, Ppv 99%, Npv 55%, Ac 90%. Six cancers (50%) coexisted with gynecomastia.

CONCLUSIONS

Mammography can accurately distinguish between malignant and benign male breast disease. Although not a replacement for clinical examination, its routine use could substantially reduce the need for biopsy in patients whose mammograms and clinical examination suggest benign disease.

Burn-activated neutrophils and tumor necrosis factor-alpha alter endothelial cell actin cytoskeleton and enhance monolayer permeability

BACKGROUND

This study examined the hypothesis that exposure of an endothelial cell (EC) monolayer to tumor necrosis factor-alpha (TNF-alpha) and that burn-activated neutrophils alter EC actin cytoskeleton and enhance the permeability of the monolayer.

METHODS

Neutrophils were harvested from rats that had undergone a 45% surface area burn (BURN-neutrophil) or uninjured control rats. ECs were grown on polyester filters or fibronectin-coated glass slides and exposed for 4 hours to media, TNF-alpha (100 ng/mL), or TNF-alpha plus BURN-neutrophil or uninjured control rats (10(7) cells). Monolayer permeability was assessed by measuring the flux of albumin across the cells. EC surface area and microfilament number and length were determined by the staining of actin microfilaments with rhodamine phalloidin followed by fluorescent microscopy.

RESULTS

The amount of albumin that moved across the monolayer in response to TNF-alpha plus BURN-neutrophil was twice that of media alone (P <.05) or TNF-alpha alone (P <.05). The number and length of actin microfilaments in ECs exposed to TNF-alpha plus BURN-neutrophil were significantly less than that of cells exposed to media alone or TNF-alpha alone.

CONCLUSIONS

These data are consistent with a hypothesis that TNF-alpha plus BURN-neutrophil affect endothelial monolayer permeability by altering EC actin cytoskeletal organization.

Identification of high-risk residents

BACKGROUND

Identification of high-risk residents allows remediation and support for administrative action when necessary. This study characterizes differences in documentation of marginally performing residents in a general surgery residency.

METHODS

High-risk residents were identified by the former program director. Twenty-four of one hundred fifteen residents over a 10-year period had one to four problematic areas: cognitive, synthetic, family/health, and interpersonal skills. Outcomes included finished (18), voluntary withdrawal (1), and involuntary withdrawal (5). A case-control study matching controls to cases by date of entry into the training program was used. Records were reviewed for demographics, preentry qualifications, American Board of Surgery In-Training Exam (ABSITE) scores, letters of complaint or praise, events of counseling, and monthly ratings. The records of 48 residents were reviewed. Ward evaluations were on eight categories with a 5-point Leikert scale (3-unacceptable to 7-outstanding). The evaluation score assigns points only to low ratings. High scores represent progressively poorer performance. A Wilcoxon signed ranks test was used to compare the cases and controls for continuous variables. The McNemar test was used in comparisons of categorical data with binary outcomes. Exact P values are reported.

RESULTS

Objective data were similar for both groups. Study residents tended to score higher on monthly evaluations at Year 2 and by Year 3 this achieved significance (0.026). Study residents were more likely to have negative faculty letters (0.016) and events of counseling by a faculty member (0.017) and the program director (0.005).

CONCLUSIONS

Identification of residents at risk should begin as early as possible during training. A combination of faculty evaluations and evidence of letters of counseling can detect high-risk residents. Programs may use such indicators to support decisions regarding remedial work or administrative action.

Focal adhesion kinase up-regulation and signaling in activated keratinocytes

BACKGROUND

During wound healing keratinocytes undergo a process called "activation" that enables the cells to spread and migrate on wound matrix molecules. Focal adhesion kinase (FAK) is a key component of integrin-mediated intracellular signaling. We investigated the induction of FAK and its signaling activity during keratinocyte activation.

MATERIALS AND METHODS

Keratinocytes were harvested from normal human skin. Previous work has shown that culture of keratinocytes causes activation in a manner similar to reepithelialization. Freshly isolated, unactivated cells were compared with cultured, activated cells. Activated cells were further examined either as growing colonies or after replating on type I collagen. FAK content was assessed by Western blotting. FAK distribution was shown using indirect immunofluorescence. FAK signaling activity was assessed using an antiphosphotyrosine antibody.

RESULTS

FAK was not detectable by Western blotting in freshly isolated cells. In contrast FAK was detected in activated cells. FAK was up-regulated between Days 2 and 4 after cell isolation from skin. Immunostaining of activated, growing keratinocyte colonies in vitro showed a diffuse, cytoplasmic pattern. When these cells were replated on collagen, FAK became concentrated in focal adhesions. Lysates from replated cells showed increased tyrosine phosphorylation of FAK.

CONCLUSIONS

In summary FAK is induced in keratinocytes in a time course comparable to that of activation. FAK is phosphorylated and undergoes redistribution to focal adhesions when cells are plated on the beta(1) integrin ligand collagen. These data suggest that induction of FAK and subsequent FAK-induced signaling may be responsible for changes in integrin-mediated behavior of activated keratinocytes during reepithelialization.

Prostaglandins potentiate U-46619-induced pulmonary microvascular dysfunction

The induction of cyclooxygenase is an important event in the pathophysiology of acute lung injury. The purpose of this study was to examine the synergistic effects of various cyclooxygenase products (PGE(2), PGI(2), PGF(2alpha)) on thromboxane A(2) (TxA(2))-mediated pulmonary microvascular dysfunction. The lungs of Sprague-Dawley rats were perfused ex vivo with Krebs-Henseleit buffer containing indomethacin and PGE(2) (5 x 10(-8) to 1 x 10(-7) M), PGF(2alpha) (7 x 10(-9) to 5 x 10(-6) M), or PGI(2) (5 x 10(-8) to 2 x 10(-5) M). The TxA(2)-receptor agonist U-46619 (7 x 10(-8) M) was then added to the perfusate, and then the capillary filtration coefficient (K(f)), pulmonary arterial pressure (Ppa), and total pulmonary vascular resistance (RT) were determined. The K(f) of lungs perfused with U-46619 was twice that of lungs perfused with buffer alone (P = 0.05). The presence of PGE(2), PGF(2alpha), and PGI(2) within the perfusate of lungs exposed to U-46619 caused 118, 65, and 68% increases in K(f), respectively, over that of lungs perfused with U-46619 alone (P < 0.03). The RT of lungs perfused with PGE(2) + U-46619 was approximately 30% greater than that of lungs exposed to either U-46619 (P < 0.02) or PGE(2) (P < 0.01) alone. When paired measurements of RT taken before and then 15 min after the addition of U-46619 were compared, PGI(2) was found to attenuate U-46619-induced increases in RT (P < 0.01). These data suggest that PGE(2), PGI(2), and PGF(2alpha) potentiate the effects of TxA(2)-receptor activation on pulmonary microvascular permeability.

Factors affecting recurrence following incisional herniorrhaphy

The purpose of this study was to determine the influence of chronic illness, obesity, and type of repair on the likelihood of recurrence following incisional herniorrhaphy. The medical records of 77 patients who underwent elective repair of a midline incisional hernia at the Dallas Veterans Affairs Medical Center between 1991 and 1995 were reviewed. Demographic data, presence of chronic illnesses, type of repair, and presence of recurrence were noted. Ninety-six percent of the patients were men, with an average age of 59 years. More than 50% of the patients had chronic lung or cardiac diseases and more than 40% weighed > or = 120% of their ideal body weight and had a body mass index (BMI) > or = 30. Sixty-two percent of the patients underwent primary reapproximation of the fascia (tissue repair), whereas 38% underwent repair with prosthetic material (prosthetic repair). The overall recurrence rate was 45%, with a median follow-up of 45 months (range 6-73). Seventy-four percent of the recurrences presented within 3 years of repair. The recurrence rate for those patients undergoing a tissue repair was 54%, whereas the recurrence rate following prosthetic repair was 29%. The incidence of recurrence for patients with pulmonary or cardiac disease or diabetes mellitus was similar to that of patients without these illnesses. The percent ideal body weight and BMI of patients who developed a recurrent hernia, particularly following a prosthetic repair, were significantly greater than those of patients whose repairs remained intact. These data strongly support the use of prosthetic repairs for incisional hernias, particularly in patients who are overweight.

A clinical pathway for inguinal hernia repair reduces hospital admissions

BACKGROUND

Clinical pathways have been advocated as a means to improve and standardize patient care while reducing costs through improved efficiency. This study examines the hypothesis that development of a clinical pathway reduces hospital admissions in a Veterans Affairs (VA) medical center.

MATERIALS AND METHODS

For the year prior to June 1997, 168 elective inguinal herniorrhaphies were performed. This constituted the prepathway (pre-P) group. One hundred ninety-six elective inguinal herniorrhaphies were performed during the year following institution of the clinical pathway-the postpathway (post-P) group.

RESULTS

Hospital admissions were compared between the two groups. In the pre-P group 61 of the 168 patients (36%) were admitted while 29 of the 196 patients (15%) in the post-P group were admitted (P < 0.001). In the pre-P group 27 of the 53 patients reviewed (51%) had either no justification or inadequate justification for admission. In the post-P group 8 of the 29 patients admitted (28%) had inadequate justification (pre-P vs post-P, P = 0.124). Common reasons for admission included pain, perioperative complications, and concurrent medical problems or surgical procedures. The most common single cause other than pain was urinary retention. The average age of patients requiring admission was greater both pre-P and post-P.

CONCLUSIONS

We conclude that institution of a clinical pathway for inguinal herniorrhaphy decreased hospital admissions. The reasons for this decrease are probably multifactorial and include improvements in physician and staff awareness. The decrease in unnecessary admissions should result in more efficient use of hospital resources.

Effect of diabetes mellitus on endotoxin-induced lung injury

OBJECTIVE

To examine the effects of diabetes mellitus on lipopolysaccharide (LPS)-induced pulmonary edema and alveolar neutrophil recruitment and activation.

HYPOTHESIS

Zucker diabetic fatty rats are resistant to the effects of intratracheal LPS on the extravasation of plasma proteins into the lungs.

DESIGN

Zucker diabetic fatty (ZDF) rats (genotype fa/fa) were used as a model of diabetes mellitus, while their normoglycemic heterozygous littermates served as controls. Lipopolysaccharide (Escherichia coli 0111: B4; 100-200 microg) or vehicle (0.25 mL of isotonic sodium chloride solution) was instilled into the airways of ZDF and control rats. Four hours later, pulmonary microvascular dysfunction was assessed by measuring the extravasation of Evans blue dye into the lung. Lipopolysaccharide-induced neutrophil recruitment was assessed by counting the number of neutrophils within the bronchoalveolar lavage fluid and measuring their expression of CD11b/CD18 by fluorescence-activated cell analysis sorting.

RESULTS

The LPS (200 microg) induced a 32% increase in Evans blue dye extravasation into the lungs of controls (P = .008) but had no such effect in diabetic animals. Pulmonary extravasation of Evans blue dye in controls was greater than that of ZDF rats both at baseline (P = .002) and in response to 200 microg of LPS (P<.001). The LPS upregulated neutrophil CD11b/CD18 expression in diabetic and nondiabetic groups and induced a greater than 50-fold increase in the number of neutrophils within the airways of both control and diabetic groups (P<.001).

CONCLUSION

Despite the recruitment of a large number of neutrophils into the lung, the LPS-induced change in pulmonary microvascular permeability in diabetic animals is substantially less than that of nondiabetic controls.

Nitric oxide and thromboxane A2-mediated pulmonary microvascular dysfunction

OBJECTIVES

To examine whether the lung releases nitric oxide (NO) in response to thromboxane A2 and to examine the local release of NO as a protective compensatory mechanism by which the lung responds to the proinflammatory and vasoactive effects of thromboxane A2.

DESIGN

The lungs of anesthetized Sprague-Dawley rats were perfused in vitro with Krebs-Henseleit buffer that contained an inhibitor of NO synthase (nitroglycerinenitro-L-arginine methyl ester [L-NAME]) (10(-4) mol/L), an NO donor (sodium nitroprusside) (10(-8) mol/L), or perfusate alone. Following equilibration, the thromboxane A2 receptor agonist 9,11-dideoxy-11alpha, 9alpha-epoxymethanoprostaglandin F2alpha(U-46619) (7.1 X 10(-8) mol/L) was added to the perfusate. Fifteen minutes later, the capillary filtration coefficient, pulmonary arterial pressure, and vascular resistance were measured. Pulmonary NO release was assessed by quantitating the release of cyclic guanosine monophosphate into the perfusate.

RESULTS

The capillary filtration coefficient of lungs exposed to U-46619 was 3.5 times greater than that of lungs perfused with buffer alone (P<.05). The addition of sodium nitroprusside reduced the increase in capillary filtration coefficient associated with U-46619 by 50% (P<.05) whereas L-NAME had no effect. The addition of U-46619 to the perfused lung caused a 3.0+/-0.4 mm Hg increase in pulmonary artery pressure (P<.01) with a corresponding rise in total vascular resistance (P<.05). This effect was exacerbated by L-NAME (P<.05) and inhibited by sodium nitroprusside (P<.05). Exposure of the isolated lungs to U-46619 caused a 4-fold increase in cyclic guanosine monophosphate levels within the perfusate.

CONCLUSION

These data are consistent with the hypothesis that NO release may be an important protective mechanism by which the lung responds to thromboxane A2.

Physiologic basis of pulmonary edema during intestinal reperfusion

This study quantitates the physiologic forces governing the movement of fluid and protein into the lungs during intestinal reperfusion (IR) and describes the anatomic pattern of protein extravasation. Sprague-Dawley rats underwent IR after which pulmonary microvascular dysfunction was assessed in vivo by measuring the concentration of protein within the airways and by quantitating the extravasation of Evans blue dye (EBD). Pulmonary microvascular dysfunction was quantitated in vitro by determining the capillary filtration coefficient (Kf), protein reflection coefficient (final sigma), and vascular resistance (Rt) using an isolated, perfused lung model. The morphologic pattern of protein extravasation into the lung was qualitatively assessed by fluorescence microscopy following the intravenous administration of fluorescent-labeled proteins of varying molecular weight. Sham-operated animals served as controls. The EBD content of lungs of IR animals was 48% greater than that of controls (P = 0.02). There was no difference in the protein concentration within the airways of these two groups. IR was associated with changes in pulmonary microvascular function favoring the movement of plasma fluid and protein into the interstitium (Kf = 0.02 +/- 0.006 vs 0.005 +/- 0.0005 g/min/mm Hg/100 g body wt; final sigma = 0.95 +/- 0.02 vs 0.99 +/- 0.005; and Rt = 0.94 +/- 0.08 vs 0. 53 +/- 0.04 mm Hg/ml/min/100 g body wt; IR vs SHAM, respectively, P < 0.05). Fluorescence microscopy demonstrated the focal extravasation of labeled proteins into the lungs of animals sustaining IR. These data suggest that both enhanced microvascular permeability and increased hydrostatic pressure contribute to the pulmonary edema associated with IR. Furthermore, the extravasation of protein is relatively focal in nature in contrast to the diffuse leak that characterizes more severe models of lung injury.

Intestinal reperfusion-induced pulmonary edema is related to increased pulmonary inducible nitric oxide synthase activity

BACKGROUND

This study examines the hypothesis that specific inhibition of the inducible isoform of nitric oxide synthase (iNOS) will attenuate intestinal reperfusion-induced pulmonary microvascular dysfunction.

METHODS

Sprague-Dawley rats underwent intestinal ischemia-reperfusion (IR) or sham operation (SHAM). Before injury, the animals received a selective inhibitor of iNOS (S-methylisothiourea sulfate, SMT: L-N6-[1-iminoethyl] lysine L-NIL), a nonselective inhibitor of NOS (NG-nitro-L-arginine methylester, L-NAME) or vehicle (0.9% saline). IR-induced changes in pulmonary microvascular permeability were assessed by quantitating the extravasation of Evans blue dye (EBD)-bound protein into the lung. Pulmonary iNOS activity and content were assessed by radiochemical analysis and Western blot, respectively.

RESULTS

There was 60% more EBD within the lungs of animals sustaining IR when compared with controls (P < .05). Pretreatment with SMT or L-NIL totally prevented the increase in EBD extravasation associated with IR. In contrast, pretreatment with L-NAME resulted in a 10% increase in dye extravasation in those animals sustaining IR when compared with similarly injured animals receiving saline (P > .05). There was significantly greater iNOS activity and enzyme content within the lungs of animals sustaining IR compared with controls.

CONCLUSIONS

These data are consistent with the hypothesis that the release of nanomolar quantities of nitric oxide generated by iNOS contributes to IR-induced pulmonary microvascular dysfunction.

The effect of sequential injuries on splanchnic perfusion and eicosanoid release

BACKGROUND

This study examines the hypothesis that sequential burn injury followed by intraabdominal sepsis induces significantly greater splanchnic hypoperfusion and reduced intestinal PGI2 release than either injury independently.

MATERIALS AND METHODS

Anesthetized Sprague-Dawley rats were randomized to one of four groups: BURN (45% body surface area scald burn) + cecal ligation and puncture (CLP); BURN alone; CLP alone; or uninjured controls (SHAM). Twenty-four hours following injury, superior mesenteric artery (SMA) blood flow was measured with a doppler flow probe. Splanchnic eicosanoid release (6-keto-PGF1alpha, metabolite of PGE2; TxB2, metabolite of TxA2; and PGE2) was measured in mesenteric venous effluent utilizing an isolated, perfused bowel preparation.

RESULTS

SMA blood flow was no different than that of controls 72 h following BURN injury alone; whereas CLP alone resulted in a 80% reduction in splanchnic blood flow when compared with controls (P < 0.001). SMA blood flow in animals sustaining BURN + CLP was only modestly reduced from controls (P = 0.04) and 3.6 times greater than that of animals sustaining CLP alone (P < 0.001). PGI2 was the dominant eicosanoid released by the intestine with levels 10 times greater than TxB2 and nearly 50 times greater than PGE2. CLP either alone or when combined with BURN was associated with a 60% decrease in splanchnic PGI2 release when compared to controls (P < 0.05).

CONCLUSIONS

These data suggest that moderate BURN injury in rats attenuates the severe reduction in splanchnic perfusion associated with intraabdominal sepsis and that this occurs despite profound reductions in the release of the endogenous splanchnic vasodilator PGI2.

Gender-related attrition in a general surgery training program

BACKGROUND

Attracting and retaining highly qualified applicants to careers in surgery is a goal of residency training programs. Few studies of attrition in residency exist. This study examines the hypothesis that reasons for attrition during general surgery training are different for male and female trainees.

MATERIALS AND METHODS

NRMP matching information was used to evaluate attrition rates in a categorical general surgery (CGS) residency program from 1984 through 1996. The records of all matched residents were examined to determine the association between gender and attrition outcomes. Outcome variables included: voluntary vs involuntary withdrawal and the reasons for withdrawal.

RESULTS

During the study period 132 candidates matched (103 men and 29 women) into CGS positions. Of that group, 18 residents, 11 (10.7%) from the male and 7 (24.1%) from the female cohorts withdrew. Only three involuntary withdrawals occurred. Women were 2.26 times more likely to withdraw than men, a finding that is not statistically significant (P = 0. 073). Women rarely left for preference of other specialty (relative risk 0.25), whereas men were 4 times more likely to leave for this reason.

CONCLUSION

These numbers suggest that women are at higher risk of leaving general surgery training than men. When women do leave, it is more likely for family reasons such as lifestyle considerations or to join a spouse in another geographic location. Such findings support the conclusion that fundamental differences exist in decisions regarding attrition between genders. National studies of attrition and the reasons for leaving are needed to develop specific strategies promoting retention for both genders.

Integrin alpha v promoter activity in keratinocytes

BACKGROUND

During reepithelialization keratinocytes show increased expression of the integrin subunit alpha-v. We have investigated the promoter region of the alpha-v integrin subunit to learn more about its regulation.

METHODS

The promoter region of the human integrin alpha-v gene was cloned into a luciferase reporter vector. Deletional mutants were created using PCR. Computerized sequence analysis was performed using the Wisconsin Package. Gel-shift analysis was performed using keratinocyte nuclear extracts and oligonucleotides spanning th regions of interest.

RESULTS

Deletion from -522 bp to -235 resulted in no discernible effect on promoter activity. In contrast deletion of the next 22 bp, which included a putative ets binding site, reduced activity by approximately half. Further deletion to -139 bp essentially abolished promoter activity. Computer searching of this region of the integrin alpha-v promoter revealed two tandemly repeated motifs, TCCTCCTCC, that had previously been implicated in the function of the epidermal growth factor receptor (EGFR) promoter. Comparison of the alpha-v integrin promoter to the EGFR promoter revealed an area of high homology in this region. Gel-shift analysis revealed binding of a single-strand specific DNA binding protein to single stranded oligos comprising these motifs, but no binding of factors to the double- stranded oligo containing the ets binding site.

CONCLUSIONS

In keratinocytes alpha-v integrin expression is controlled by a region of the promoter with high homology to the epidermal growth factor receptor promoter This region binds single-strand specific DNA binding proteins that are likely to be important in controlling transcription.

Alveolar macrophage response to remote organ injury

Intestinal reperfusion (IR)-induced pulmonary edema has been related to endogenous pulmonary thromboxane A2 (TxA2) release. This study examines the hypothesis that alveolar macrophages (aMphis) activated during IR are an important cellular source of TxA2 in this model. Anesthetized Sprague Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IR) or sham operation (Sham). aMphis were isolated by bronchoalveolar lavage and incubated in Krebs buffer for 30 min, after which the supernatant was analyzed for TxB2 (metabolite of TxA2) and prostaglandin E2. Other parameters of aMphi activation measured included lysosomal enzyme release (beta-glucuronidase), superoxide (O2-) release, and procoagulant activity. aMphis from animals sustaining IR generated more than twice as much TxA2 and prostaglandin E2 as did those isolated from controls (p < .05). Other evidence of aMphi activation included a nearly 100-fold increase in procoagulant activity, a 7-fold increase in beta-glucuronidase release, and a 2.5-fold increase in O2- release over that of controls (p < .05). These data suggest that TxA2 is a major eicosanoid product of aMphis during IR and that aMphis may be an important cellular participant in IR-induced pulmonary microvascular injury, either directly by releasing O2-, lysosomal enzymes, and pro-coagulant factors, or indirectly by generating TxA2.

Abdominal aortic aneurysms and malignant neoplasia: double jeopardy

BACKGROUND

This study was performed to determine whether there is a significant association between abdominal aortic aneurysms (AAAs) and malignancy and to determine the impact of malignancy on late survival in patients with AAA.

METHODS

We studied 126 men undergoing AAA repair and compared them with 99 men undergoing aortofemoral bypass (AFB) for occlusive disease and with 100 men undergoing herniorrhaphy during the same period.

RESULTS

Fifty-one (40%) patients with AAA, 23 (23%) patients undergoing AFB, and 21 (21%) patients undergoing herniorrhaphy were diagnosed with cancer (p = 0.002). By life table analysis the proportion of subjects remaining cancer free at 5 years was 0.60 +/- 0.05 for AAA, 0.83 +/- 0.04 for AFB, and 0.81 +/- 0.04 for herniorrhaphy (p = 0.004). Multivariate analysis selected four independent risk factors for cancer: presence of AAA (p = 0.003, odds ratio 1.4, confidence interval [CI] 1.2 to 1.7), age (p = 0.001, odds ratio per year 1.1, CI 1.0 to 1.1), smoking (p = 0.04, odds ratio 1.5, CI 1.0 to 2.2), and hypertension (p = 0.04, odds ratio 0.73, CI 0.5 to 1.0). Cancer deaths accounted for 32% of late deaths in patients with AAA, which was not different compared with 26% of late deaths in patients undergoing AFB and 36% of late deaths in patients undergoing herniorrhaphy. Five-year cancer-free survival was 0.44 +/- 0.05 for patients with AAA, 0.64 +/- 0.05 for patients undergoing AFB, and 0.70 +/- 0.05 for patients undergoing herniorrhaphy (p < 0.001, AAA versus herniorrhaphy only).

CONCLUSIONS

Cancer is more prevalent in men with AAA than in men undergoing AFB or herniorrhaphy. The presence of AAA appears to be an independent risk factor for cancer. Despite the higher cancer prevalence in patients with AAA, cardiovascular disease accounted for the largest number of late deaths in this series, minimizing differences in cancer-free survival between patients with AAA and patients undergoing AFB.

Downstream effects of splanchnic ischemia-reperfusion injury on renal function and eicosanoid release

This study examines the hypothesis that intestinal ischemia-reperfusion (I/R) injury contributes to renal dysfunction by altered renal eicosanoid release. Anesthetized Sprague-Dawley rats underwent 60 min of sham or superior mesenteric artery (SMA) occlusion with 60 min of reperfusion. The I/R groups received either allopurinol, pentoxifylline, 1-benzylimidazole, or carrier before SMA occlusion. In vivo renal artery blood flow was measured by Transonic flow probes, the kidneys were then perfused in vitro for 30 min, and the effluent was analyzed for eicosanoid release and renal function. Intestinal I/R caused a twofold increase in the ratio of renal release of thromboxane B2 to prostaglandin E2 and to 6-ketoprostaglandin F1alpha compared with the sham level, with a corresponding 25% decrease in renal sodium and inulin clearance and renal blood flow. Pentoxifylline or allopurinol pretreatment restored renal eicosanoid release and renal sodium and inulin clearance to the sham level but did not alter renal blood flow. Pretreatment with 1-benzylimidazole restored renal function, eicosanoid release, and renal blood flow to sham levels. These data suggest that severe intestinal I/R contributes to the downregulation of renal function. The decrease in renal function is due in part to toxic oxygen metabolites, which occur in the milieu of altered renal eicosanoid release, reflecting a decrease in vasodilator and an increase in vasoconstrictor eicosanoids.

Perianal mucinous adenocarcinoma

BACKGROUND

Perianal mucinous adenocarcinoma is a rare variant of anal canal epithelioid tumors. Our objective in this report is to examine the clinical features, pathology, treatment, and outcome for patients with perianal mucinous adenocarcinoma.

METHODS

A retrospective review identified four patients with histologically proven perianal mucinous adenocarcinoma. The medical records of these patients were reviewed for presentation, therapy, and outcome.

RESULTS

Pain and bleeding were present in all cases. In three of four patients, chronic perirectal disease was present, including two abscesses and one fistula. All patients had extensive local disease at presentation. One patient presented with bilateral inguinal nodal metastases. Two patients received neoadjuvant chemotherapy and radiation, with a third patient receiving radiation alone. Two of these three patients underwent abdominoperineal resection. Three patients subsequently died (all of progression and/or recurrence) 2-48 months after diagnosis. The fourth patient (who was treated with chemotherapy and radiation followed by abdominoperineal resection) is alive and disease free at 12 months.

CONCLUSIONS

Perianal mucinous adenocarcinoma is a rare disease with a poor prognosis, mostly due to its advanced nature at the time of diagnosis. Chemoradiation followed by surgery may improve outcome in selected individuals.

Thromboxane A2 mediates increased pulmonary microvascular permeability after intestinal reperfusion

This study examines the hypothesis that intestinal reperfusion (IR)-induced pulmonary thromboxane A2 (TxA2) release increases local microvascular permeability and induces pulmonary vasoconstriction. Sprague-Dawley rats underwent 120 min of intestinal ischemia and 60 min of IR. Sham-operated animals (Sham) served as controls. After IR or Sham, the pulmonary vessels were cannulated, and the lungs were perfused in vitro with Krebs buffer. Microvascular permeability was quantitated by determining the filtration coefficient (Kf), and pulmonary arterial (Ppa), venous (Ppv), and capillary (Ppc) pressures were measured to calculate vascular resistance (Rt). After baseline measurements, imidazole (TxA2 synthase inhibitor) or SQ-29,548 (TxA2-receptor antagonist) was added to the perfusate; then Kf, Ppa, Ppv, and Ppc were again measured. The Kf of lungs from IR animals was four times greater than that of Sham (P = 0.001), and Rt was 63% greater in the injured group (P = 0.01). Pc of IR lungs was twice that of controls (5.4 +/- 1.0 vs. 2.83 +/- 0.3 mmHg. IR vs. Sham, respectively; P < 0.05). Imidazole or SQ-29,548 returned Kf to baseline measurements (P < 0.05) and reduced Rt by 23 and 17%, respectively (P < 0.05). IR-induced increases in Pc were only slightly reduced by 500 micrograms/ml imidazole (14%; P = 0.05) but unaffected by lower doses of imidazole (5 or 50 micrograms/ml) or SQ-29,548. These data suggest that IR-induced pulmonary edema is caused by both increased microvascular permeability and increased hydrostatic pressure and that these changes are due, at least in part, to the ongoing release of TxA2.

The effect of intestinal reperfusion on renal function and perfusion

This study examines the effect of intestinal reperfusion injury (IIR) on renal blood flow and relates this temporally to changes in renal ATP levels and renal tubular function. Sprague-Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IIR). Renal blood flow was measured with radiolabeled microspheres and a Doppler flow probe. Renal dysfunction was quantitated by measuring inulin clearance and fractional excretion of sodium (FENa) in the isolated perfused organ. Renal tissue ATP levels were measured using a luciferase-luciferin assay. Sham-operated animals served as controls (SHAM). Renal blood flow was reduced by > 80% in the animals sustaining IIR when compared to baseline measurements (P < 0.05) or SHAM (P < 0.05). Temporally this reduction in renal blood flow was associated with a 25% reduction in tissue ATP levels (P < 0.05). The kidneys of animals sustaining IIR had a significantly greater FENa than did those of controls. These data support the notion that IIR is associated with a profound reduction in renal blood flow which is temporally related to reduced renal tissue ATP levels and renal tubular dysfunction.

Estrogen increases male rat aortic endothelial cell (RAEC) PGI2 release

Estrogen has been proposed as a negative risk factor for development of peripheral vascular disease yet mechanisms of this protection are not known. This study examines the hypothesis that estrogen stimulates rat aortic endothelial cell (RAEC) release of PGI2. Male Sprague-Dawley rat abdominal aortic 1-mm rings were placed on 35 mm matrigel plates, and incubated for 1 week. The cells were transferred to a Primaria 60-mm dish and maintained from passage 3 in RAEC complete media and experiments performed between passages 4-10. Cells were incubated with Krebs-Henseleit buffer (pH 7.4) containing carrier or increasing concentrations of beta-estradiol or testosterone for 60 min. The effluent was analyzed for eicosanoid release of 6-keto-PGF1 alpha (6-keto, PGI2 metabolite), PGE2 and thromboxane B2 (TXB2) by EIA (hormone stimulated-basal). Cells were analyzed for total protein by the Bradford method and for cyclooxygenase-1 (COX-1) and prostacyclin synthase (PS) content by Western blot analysis and densitometry. Testosterone did not alter RAEC 6-keto-PGF1 alpha release, whereas estrogen increased RAEC 6-keto-PGF1 alpha release in a dose-related manner. Estrogen preincubation (10 ng/ml) decreased COX-1 and PS content by 40% suggesting that the estrogen-induced increase in male RAEC PGI2 release was not due to increased synthesis of COX-1 or PS. These data support the hypothesis that estrogen stimulation can increase endogenous male RAEC release of PGI2.

Long-term resuscitation of hemorrhage/reperfusion injury (H/R) stimulates renal PGE2 release

This study examines the hypothesis that long-term resuscitation with hyperalimentation (TPN) following acute hemorrhage/reperfusion (H/R) injury stimulates renal release of PGE2. Male Sprague-Dawley rats were anesthetized and subjected to sham or hemorrhage to 30 mmHg for 30 min followed by reperfusion. All rats were placed on TPN for 5 days, then underwent laparotomy for in vivo renal artery and aortic blood flow for 60 min. The kidney was perfused in vitro with Krebs-Henseleit buffer at 3 ml/min (pH 7.4, 37 degrees C) and venous effluent was collected for analysis of PGE2, 6-keto-PGF1 alpha and thromboxane B2 by EIA. Hemorrhage/reperfusion followed by TPN for 5 days increased renal PGE2 2-fold and decreased in vivo renal artery blood flow by 50% compared to the sham group. Hemorrhage/reperfusion followed by TPN did not alter release of the other eicosanoids measured. These data suggest that the kidney has a limited capacity to maintain renal blood flow by increasing release of PGE2 when the animal is subjected to long-term resuscitation with TPN following mild hemorrhage/reperfusion injury.

Autoregulation of renal and splanchnic blood flow following infra-renal aortic clamping is mediated by nitric oxide and vasodilator prostanoids

OBJECTIVE

This study examines the hypothesis that nitric oxide and vasodilator prostanoids contribute to the autoregulation of renal artery and superior mesenteric artery (SMA) blood flow following infra-renal aortic clamping.

EXPERIMENTAL DESIGN

Renal and SMA artery blood flow were measured in anesthetized rats. The rats received bolus injection of saline carrier, L-NAME (25 mg/kg) or indomethacin (15 mg/kg) prior to sham or infra-renal aortic occlusion. In vivo blood flow was measured 1, 30 and 60 minutes during aortic occlusion and 1, 30, and 60 minutes following release of the aortic cross clamp.

RESULTS

Aortic occlusion transiently increased SMA blood flow but did not alter renal artery blood flow. Aortic clamp release resulted in a 40% decrease in both SMA and renal artery blood flow. L-NAME or indomethacin pretreatment decreased both SMA and renal artery blood flow at 60 minutes following infrarenal aortic occlusion. Indomethacin decreased SMA blood flow at 1 minute following unclamping of the aorta and L-NAME decreased SMA blood flow at 30 and 60 minutes following aortic clamp release. Both L-NAME and indomethacin markedly decreased renal artery blood flow at all time periods following aortic clamp release.

CONCLUSIONS

These data suggest that renal and splanchnic vascular beds utilize endogenous vasodilator eicosanoids and nitric oxide to maintain blood flow during cross clamping and unclamping of the infra-renal aorta.

Hepatic hypoperfusion after intestinal reperfusion

BACKGROUND

Intestinal ischemia-reperfusion injury (IIR) induces hepatic and pulmonary dysfunction and thus has been used as a model of multiple organ failure syndrome. This study examines the hypothesis that hepatic blood flow is markedly reduced in this injury model.

METHODS

Sprague-Dawley rats underwent 120 minutes of intestinal ischemia and 60 minutes of reperfusion (IIR). Hepatic blood flow was measured with radiolabeled microspheres and Doppler flow probes. Hepatic dysfunction was quantitated by measuring bile flow and serum alanine aminotransferase and hepatic tissue adenosine triphosphate levels. Sham-operated animals served as controls.

RESULTS

Intestinal ischemia reduced portal flow by 66% when compared with sham-operated animals (p = 0.0001) but had no effect on hepatic arterial flow. In contrast, reperfusion reduced hepatic artery flow by 80% when compared with controls (p = 0.002) with most of this change occurring within 5 minutes of reperfusion. IIR induced a 63% reduction in bile flow (p < 0.05), a fivefold rise in serum alanine aminotransferase level (p < 0.0002), and a 33% reduction in hepatic adenosine triphosphate level (p < 0.05).

CONCLUSIONS

These data suggest that IIR induces profound hepatic hypoperfusion, which is temporally related to acute hepatic dysfunction. This observation suggests that hepatic ischemia may contribute to IIR-induced liver injury.

Intestinal reperfusion up-regulates inducible nitric oxide synthase activity within the lung

BACKGROUND

This study examines the hypothesis that pulmonary inducible nitric oxide synthase (iNOS) activity is up-regulated during intestinal reperfusion and that inhibition of NO generation exacerbates pulmonary microvascular dysfunction.

METHODS

Sprague-Dawley rats underwent intestinal ischemia and reperfusion (IIR) or sham operation (SHAM). Pulmonary iNOS activity was measured by quantitating the conversion of L-arginine (L-Arg) to L-citrulline. Another set of animals undergoing IIR or SHAM received an inhibitor of NOS (NG-nitro-L-arginine methylester; L-NAME; 20 mg/kg intravenously), substrate for NO generation (L-Arg; 300 mg/kg intravenously), or vehicle (normal saline solution; 3 ml). Pulmonary microvascular dysfunction was then quantitated by measuring the extravasation of Evans blue dye (EBD) into the lung.

RESULTS

Inducible NOS activity was six times greater in the lungs of animals sustaining IIR when compared with SHAM (p = 0.0005). The concentration of EBD within the lungs of animals sustaining IIR was 30% greater than SHAM (p < 0.05). Inhibiting NOS with L-NAME significantly increased pulmonary EBD concentration of both IIR and SHAM groups when compared with normal saline solution-treated animals (p < 0.0001). Treatment with L-Arg prevented this IIR-induced increase in pulmonary dye extravasation.

CONCLUSIONS

These data suggest that pulmonary iNOS activity is up-regulated in animals sustaining IIR and that this may serve as a compensatory protective response to remote organ injury.

In vitro evidence of neutrophil-mediated lung injury after intestinal reperfusion

This study examines the hypothesis that neutrophils isolated from animals sustaining intestinal reperfusion (IIR) induce pulmonary microvascular dysfunction. Lungs were isolated from normal Sprague-Dawley rats and perfused with a physiologic buffer in vitro. Neutrophils (2 x 10(6)) isolated from animals sustaining IIR (n = 5) or sham operation (SHAM; n = 6) were infused into the isolated lung model. A third group of lungs underwent in vitro perfusion without exposure to neutrophils (n = 5). Lung injury was assessed by measuring wet to dry weight ratios and pulmonary artery pressure (PAP). Pulmonary ultrastructure was assessed by electron microscopy. The wet:dry ratio of lungs from animals sustaining IIR was greater than that of lungs exposed to SHAM neutrophils (p = .03) or perfusate alone (p = .02). The PAP of lungs exposed to IIR neutrophils was nearly 10 times greater than that of lungs exposed to SHAM neutrophils (p = .003) or buffer alone (p = .006). Ultrastructural examination of lungs exposed to IIR neutrophils demonstrated interstitial edema with occasional focal disruptions in the alveolar capillary endothelial cell membrane whereas lungs exposed to SHAM neutrophils were normal. These experiments provide important in vitro correlation of prior in vivo studies suggesting that neutrophils are important pathogenic mediators of IIR-induced lung injury.

Neutrophil regulation of splanchnic blood flow after hemorrhagic shock

OBJECTIVE

This study examines the hypothesis that neutrophils impair splanchnic blood flow during resuscitation from hemorrhage by inhibiting the release of the compensatory vasodilator PGI2 from the bowel.

SUMMARY BACKGROUND DATA

Resuscitation from hemorrhagic shock is associated with neutrophil infiltration into the intestine, reduced splanchnic perfusion, and reduced release of PGI2 from the intestine.

METHODS

Sprague-Dawley rats received either vinblastine (VIN) to deplete circulating neutrophils or normal saline (NS). These animals then underwent either hemorrhage and resuscitation (SK + R) or sham operation (SHAM). Superior mesenteric artery flow and splanchnic 6-keto PGF1a (metabolite of PGI2) release were measured.

RESULTS

Superior mesenteric artery blood flow was significantly greater in VIN-treated animals sustaining SK + R than in those treated with NS (p < 0.05). Neutrophil depletion preserved 6-keto PGF1a release after SK + R, whereas 6-keto PGF1a release in the NS-treated, SK + R group was significantly reduced (p < 0.05).

CONCLUSION

These data are compatible with the hypothesis that neutrophils may influence splanchnic perfusion after SK + R by inhibiting splanchnic PGI2 release.

Pulmonary thromboxane release following intestinal reperfusion

Microvascular dysfunction is a prominent feature of the lung injury associated with intestinal reperfusion (IR). This study examines the hypothesis that IR induces pulmonary thromboxane A2 (TxA2) release, which contributes to pulmonary microvascular dysfunction. Sprague-Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IR). Sham-operated animals served as controls (SHAM). Following IR or SHAM, the lungs were perfused in vitro with a modified Krebs buffer and ventilated with room air. Eicosanoid levels within the pulmonary venous effluent and bronchoalveolar lavage (BAL) fluid were determined (TxB2, 6-keto-PGF1a, and PGE2). Pulmonary artery pressure (PAP) was measured continuously and expressed as change from baseline in mm Hg. The dominant eicosanoid generated by the lungs in response to IR was TxB2. TxB2 levels in the pulmonary venous effluent of IR lungs were 75% greater than controls (P = 0.005). Similarly, TxB2 levels in the BAL were more than 2.5 times controls (P = 0.001). The change in PAP of lungs from IR animals was significantly greater than that of controls (4.1 +/- 1.5 vs 0.3 +/- 0.54 mm Hg, IR vs SHAM, P = 0.01). The increased PAP associated with IR lungs was prevented by cyclooxygenase inhibition with indomethacin (-1.28 +/- 0.29 mm Hg, P < 0.05) and thromboxane synthetase inhibition with imidazole (-1.75 +/- 0.95 mm Hg, P < 0.05). These experiments support the hypothesis that IR up-regulates endogenous pulmonary TxA2 release. Furthermore, the local release of TxA2 by the lung may contribute to the microvascular dysfunction characteristic of IR-induced lung injury.

Splanchnic PGI2 release and "no reflow" following intestinal reperfusion

This study examines the hypothesis that reduced splanchnic blood flow during intestinal reperfusion (IR) is associated with impaired release of the vasodilatory prostanoid PGI2. Sprague-Dawley rats underwent occlusion of the superior mesenteric artery (SMA) for 120 min and reperfusion for up to 60 min. SMA blood flow was measured by transonic flow probe and radiolabeled microspheres (141Ce and 103Ru). Sham-operated animals served as controls (SHAM). Splanchnic eicosanoid release was quantitated by measuring thromboxane B2 (TxB2, stable metabolite of TxA2), 6-keto-PGF1a (6-keto, stable metabolite of PGI2), and PGE2 within the portal vein (PV) and inferior vena cava (IVC) of animals sustaining IR and SHAM. SMA flow in IR animals was < 10% of baseline and 27% of SHAM when measured by transonic flow probe (8 +/- 2% and 29 +/- 3%, IR and SHAM, respectively, P < 0.05). Similar results were obtained when intestinal blood flow was measured with microspheres (0.33 +/- 0.12 vs 1.34 +/- 0.13 ml/min/g, IR vs SHAM, P < 0.05). The greatest change in IR-induced splanchnic eicosanoid release occurred with 6-keto. Following ischemia, 6-keto levels in the PV were twice those of SHAM (P < 0.05). Five minutes after reperfusion, PV 6-keto levels were 22 times those of controls (P < 0.05) and 4 times greater than those of the IVC (P < 0.05). By 60 min of reperfusion, levels of 6-keto were reduced to those in the IVC. These data support the hypothesis that splanchnic blood flow is critically reduced by severe IR.(ABSTRACT TRUNCATED AT 250 WORDS)

Resuscitation of ischemia/reperfusion with hyperalimentation increases intestinal PGI2 synthase (PS) content and PGI2 release

Normal rat splanchnic blood flow and eicosanoid synthesis were compared to sham (Sham) and hemorrhage/reperfusion (SK + R) animals treated with 5 days of total parenteral nutrition (TPN). After in vivo measurement of superior mesenteric artery (SMA) blood flow, the splanchnic bed was perfused in vitro and venous effluent assayed for eicosanoid release by EIA. Aortic, SMA, ileal muscularis/serosa, and mucosa homogenates were analyzed for cyclooxygenase (COX) and prostacyclin synthase (PS) content by Western blot and for COX activity by radiochromatography. SK + R + TPN decreased SMA blood flow 33% and increased splanchnic PGI2 release twofold (p < .05) compared with the Sham +TPN and normal groups. groups SK + R + TPN did not alter COX activity in any of the tissues but Western blot analysis showed a twofold increase in COX and PS content in ileum muscularis/serosa (p < .05). These data show that SK + R + TPN induced a decrease in SMA blood flow and a compensatory increase in release of splanchnic PGI2. The mechanism for increased splanchnic PGI2 release after SK + R + TPN was an increase in PS and COX content (not activity) in the ileal muscularis/serosa.

Complement activation by the hydroxyl radical during intestinal reperfusion

This study examines the hypothesis that hydroxyl radical (OH.) generation during intestinal reperfusion activates the complement system forming the potent chemotaxin C5a. Anesthetized Sprague-Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IIR). Complement (C) activation was assessed by measuring total plasma C activity and C5a-related chemotaxis and leukoaggregation. Dimethylthiourea and the iron chelator deferoxamine were utilized to assess the role of the OH. in the activation of C in this model. Sham-operated animals served as controls. Total plasma C activity of animals sustaining IIR was 64% of controls (p < .05). Plasma of animals sustaining IIR induced greater chemotaxis and leukoaggregation than plasma from sham-operated groups (p < .05). Treatment of IIR plasma with anti-C5a antibody ameliorated the enhanced leukoaggregation characteristic of IIR plasma. Pretreatment with dimethylthiorea and deferoxamine prevented reperfusion-induced activation of complement and inhibited the chemotactic activity of plasma from IIR animals. These data are consistent with the hypothesis that IIR activates complement and that the OH. generated during reperfusion may be one mechanism by which C is activated in this injury model.

Pulmonary microvascular injury following intestinal reperfusion

Multiple organ failure is the most common cause of death in critically ill patients in the United States. Acute respiratory failure is the most important single component of this clinical scenario, with a mortality risk > 50%. Key pathophysiologic events occur in the pulmonary microvasculature at the interface between circulating elements and the external environment. In particular, the response of the alveolar capillary endothelial cell is of fundamental importance in this injury process. A variety of clinical stimuli initiate a systemic inflammatory response that contributes to acute microvascular lung injury. Sepsis, trauma, thermal injury, acute pancreatitis, and ischemia-reperfusion injury are among these stimuli. The particular emphasis of this review is on events associated with intestinal ischemia-reperfusion, a common and important clinical event. The pathogenic mechanisms that lead to acute lung injury in this setting are not completely understood, although it is clear that neutrophil-endothelial interactions regulated by both humoral and local mediators are crucial. Oxygen-derived free radicals, proteases, cytokines, eicosanoids, endotoxin, complement activation products, and probably platelet activating factor and nitric oxide are involved as either signalling or effector molecules. The key cellular participants during the acute phase of injury are the polymorphonuclear neutrophil (PMN) and the microvascular endothelial cell. Each of these participants is considered with regard to phlogistic behavior and the potential for therapeutic intervention. Adherence of the neutrophil to the endothelium creates a microenvironment in which PMN-derived oxidants, proteases, and cationic proteins are discharged under conditions that lead to cellular injury. Loss of microvascular integrity results and pulmonary dysfunction follows. At present, we offer only nonspecific supportive care for patients with this problem. However, investigations into relevant molecular and cellular regulatory events offer important opportunities for directed therapy. We are now approaching the threshold for utilization of several new and specific approaches. While no single pharmacologic therapy is likely to be curative for this complex problem, it is probable that certain approaches will be of clinical benefit in the near future. This review is designed to provide a basis for understanding this evolution.

The effect of polyethylene glycol gavage on plasma volume

This study examines the hypothesis that whole gut irrigation with polyethylene glycol-electrolyte gavage solution (PEG-ELS) increases intravascular volume. Seventeen patients drank 6 to 8 liters of PEG-ELS in preparation for elective colonoscopy. The patients were weighed and serum electrolytes, albumin, hematocrit, blood urea nitrogen, and creatinine were obtained prior to the gavage and 8 hr following gavage. Plasma volume was measured before and after gavage using an isotope dilution technique involving 125I-human serum albumin. No patients developed symptoms of intravascular volume excess or depletion following gavage. There was no significant change in body weight, serum sodium, chloride, potassium, bicarbonate, blood urea nitrogen, or creatinine following gavage with PEG-ELS. When measured by the isotope dilution technique, the mean plasma volume increased from 3174 +/- 117 ml before gavage to 3365 +/- 160 ml following gavage (P = 0.03). This represented a mean percentage change in plasma volume of 5.88 +/- 2.4%. The percentage change in plasma volume associated with gavage ranged from -9.8 to +29.8%. This data supports the hypothesis that gavage with polyethylene glycol-electrolyte solution is associated with an increase in plasma volume. Although in most patients the increase in plasma volume is minimal, there is significant variability in this response, with some patients experiencing substantial increases in plasma volume.

Endotoxemia and remote organ injury following intestinal reperfusion

This study addresses the hypothesis that endotoxin (LPS) is an important proximal mediator of remote organ dysfunction following intestinal reperfusion. Sprague-Dawley rats underwent intestinal ischemia for 120 min followed by 60 min of reperfusion (IIR). Animals underwent pretreatment with polymyxin B (PMB, 200 micrograms, sc) or the induction of tolerance to LPS prior to assignment to the IIR or sham group. Controls received equal volumes of normal saline. Lung and intestinal injury was quantitated using an edema index. Bile flow was quantitated by measuring the volume of bile produced per 15 min. The intestinal edema index of IIR animals pretreated with PMB was nearly 50% less than that of saline-treated animals sustaining the same injury (P < 0.05). The induction of LPS tolerance reduced the edema index of IIR animals by 28% compared to the saline-treated IIR group (P < 0.05). Neither treatment reduced this parameter to that of sham-operated controls (P < 0.05). The lung edema index of animals pretreated with PMB was 50% of that of saline-treated IIR animals (P < 0.05). This remained significantly greater than that of sham-operated controls (P < 0.05). LPS tolerance did not affect the lung edema index of animals sustaining IIR. Bile flow rates following IIR were not significantly affected by PMB or LPS tolerance. These data do not support the hypothesis that LPS is an important proximal mediator of the remote organ injury associated with IIR. However, they do suggest that LPS may be one of many mediators responsible for this injury.

The effects of hypovolemia on multiple organ injury following intestinal reperfusion

This study examines the relationship between hypovolemia and remote organ injury following intestinal reperfusion. Sprague-Dawley rats underwent intestinal ischemia (120 min) and reperfusion (90 min, IIR) or sham operation (CTL). The animals received normal saline (NS) at 0, 30, or 40 ml/kg/h intravenously. Lung and intestinal injury was quantitated using an edema index, and liver injury was assessed by measuring bile flow rates. The infusion of 40 ml/kg/h of NS attenuated the intestinal edema index of IIR animals nearly 50% (p < .05). Despite this improvement, this parameter remained nearly 10-fold greater than that of CTL (p < .05). The lung edema index was 70% greater in IIR animals receiving 30 and 40 ml/kg/h of NS than those not receiving NS. The infusion of 40 ml/kg/h of NS restored bile flow rates in IIR animals to that of CTL. These data suggest that hypovolemia may contribute to the intestinal and hepatic injury in this model. The lung injury is independent of hypovolemia.

Pulmonary endothelial cell ATP depletion following intestinal ischemia

Multiple organ failure (MOF) is known to follow systemic inflammatory mediator activation associated with intestinal ischemia-reperfusion injury. In particular, the pulmonary microvasculature appears to be susceptible to MOF-related injury. This study was designed to evaluate the hypothesis that non-cellular plasma factors associated with intestinal ischemia without reperfusion also mediate pulmonary endothelial cell injury. Male Sprague-Dawley rats had intestinal ischemia induced by microvascular clip occlusion of the superior mesenteric artery for 30, 60, 90, or 120 min. Following each period of ischemia, plasma samples were obtained from the protal vein. Time-matched sham-operated animals served as controls. Monolayers of cultured rat pulmonary artery endothelial cells were then incubated with the plasma samples and ATP levels determined using a luciferin-luciferase assay. A 51Cr-release assay using labeled endothelial cells was performed under identical conditions to assess cytotoxicity. Endothelial cell ATP levels were 1.99 +/- 0.23 x 10(-11) mole/micrograms DNA in sham preparations. After a 4-hr incubation in plasma from the 90 and 120 min ischemia groups, cellular ATP levels fell significantly to 1.07 +/- 0.23 x 10(-11) mole/micrograms DNA, respectively (P less than 0.005). No significant cytotoxic injury resulted from incubation with plasma from the 120 min group (1.0 +/- 0.4% versus 0.8 +/- 0.4% in sham group, P = NS). All animals survived 24 hr in the sham, 30, and 60 min groups. However, survival was 40 and 0% in the 90 and 120 min groups, respectively (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocellular oxidant stress following intestinal ischemia-reperfusion injury

Reperfusion of ischemic intestine results in acute liver dysfunction characterized by hepatocellular enzyme release into plasma, reduction in bile flow rate, and neutrophil sequestration within the liver. The pathophysiology underlying this acute hepatic injury is unknown. This study was undertaken to determine whether oxidants are associated with the hepatic injury and to determine the relative value of several indirect methods of assessing oxidant exposure in vivo. Rats were subjected to a standardized intestinal ischemia-reperfusion injury. Hepatic tissue was assayed for lipid peroxidation products and oxidized and reduced glutathione. There was no change in hepatic tissue total glutathione following intestinal ischemia-reperfusion injury. Oxidized glutathione (GSSG) increased significantly following 30 and 60 min of reperfusion. There was no increase in any of the products of lipid peroxidation associated with this injury. An increase in GSSG within hepatic tissue during intestinal reperfusion suggests exposure of hepatocytes to an oxidant stress. The lack of a significant increase in products of lipid peroxidation suggests that the oxidant stress is of insufficient magnitude to result in irreversible injury to hepatocyte cell membranes. These data also suggest that the measurement of tissue GSSG may be a more sensitive indicator of oxidant stress than measurement of products of lipid peroxidation.

Redo fundoplication in infants and children with recurrent gastroesophageal reflux

The Nissen fundoplication is well established as the surgical treatment for medically refractory gastroesophageal reflux (GER) in childhood. Recurrent GER following fundoplication is a challenging problem with a reported incidence ranging from 0% to 12%. From January 1974 to January 1989, 286 children have been treated for GER with Nissen fundoplication and gastrostomy tube placement at the University of Michigan C.S. Mott Children's Hospital; 242 of these children have been followed for an average of 30 months, the remaining 44 have been lost to follow-up. Twenty-nine children (12%) have developed recurrent reflux following fundoplication. Medical management with thickened upright feelings, gastrostomy feedings, or gastrojejunostomy tube feedings has been successful for 11 children with control of reflux symptoms. Five additional children who were treated nonoperatively died of coexistant medical problems within 2 months following documentation or recurrent reflux. The remaining 13 children have required redo fundoplication for wrap disruption or herniation, and an additional six children, initially treated at other institutions, have also undergone redo fundoplications. One other child treated at this hospital required redo fundoplication for a postoperative partial gastric volvulus causing gastric outlet obstruction. Of the 20 children who have undergone a second Nissen fundoplication, 16 (80%) are doing well without recurrent GER. Four children have developed recurrent GER with wrap disruption; 1 is doing well following a third fundoplication, 2 have been managed successfully with continuous feedings via gastrojejunostomy feeding tubes, and a fourth child died of complications related to a recurrent tracheoesophageal fistula. Conservative management with gastrojejunal tube feedings should be considered in the initial management of children with recurrent GER following fundoplication.(ABSTRACT TRUNCATED AT 250 WORDS)

The value of intestinal myotomy and myectomy in improving the reservoir capacity of the endorectal pull-through

In laboratory models of massive small bowel resection and colectomy, intestinal myotomy has been shown to decrease stool frequency and malabsorption. Using physiologic and anatomic parameters of gastrointestinal function, we assessed the ability of three types of ileal myotomies to improve outcome after total abdominal colectomy, mucosal proctectomy, and endorectal pull-through (ERPT) without an enteric reservoir. Twenty puppies underwent ERPT. These dogs were randomly assigned to three experimental groups or a control group consisting of animals without a myotomy. The myotomies were performed by excising the serosa and muscularis propria of the ileal wall in three different patterns. There was no difference between any of the groups with respect to general health, postoperative weight gain, stool frequency, intestinal transit time, water absorption, electrolyte absorption, barium enemas, neorectal capacity and dimensions, and histology.

Late results of fundoplication for gastroesophageal reflux in infants and children

The Nissen fundoplication (NFP) for the management of severe gastroesophageal reflux (GER) in infants and children has become one of the most frequently performed operations in pediatric surgical centers in the United States. Short-term outcome, morbidity, and mortality are consistently favorable in several large series. The long-term success of this procedure is presumed but has not been established objectively. To examine the late results of this operation, 46 infants and children were carefully evaluated more than 5 years after NFP (mean, 6.7 years). Evaluation included parental interview, physical examination, upper gastrointestinal series, and esophageal pH monitoring. The mean age at the time of operation was 4.13 years. Fifty-seven percent of the patients had significant neurologic impairment, and 80% had at least one serious additional medical problem. Twenty-four percent of the children died during the period of follow-up--all but one death related to serious underlying medical problems. Of the 35 survivors, 26 (74.3%) have no symptoms; five (14.3%) have mild symptoms potentially referable to GER that necessitate little if any treatment; four (11.5%) have had symptomatic recurrence of GER necessitating repeat fundoplication. Three of these patients now have no symptoms. Forty-five percent of the patients had at least one postoperative complication. NFP provides efficacious, long-term treatment of GER in infants and children, with acceptable morbidity. Mortality in this group of children is related primarily to associated diseases rather than to GER.

Long-term radiographic follow-up of the Nissen fundoplication in children

This study examined 46 children 5-9 years (mean 6.7) after Nissen fundoplication surgery for gastroesophageal reflux (GER). Eleven were deceased and ten of the 35 families declined objective evaluation. The remaining 25 children (71%) had a barium swallow examination. In 16 of the 25 patients the fundoplication was intact. In 2 patients a small portion of the fundoplication was displaced above the diaphragm. In 5 patients there was residual esophageal disease. In 3 patients (one with esophageal disease), with a hiatus hernia prior to surgery, despite immediate postoperative reduction, the barium swallow examination done for this study revealed recurrent hiatus hernia but no GER. Long-term results of the Nissen fundoplication reveal success in eliminating clinically significant gastroesophageal reflux. Those patients with esophageal disease prior to the surgery need close interval follow-up to monitor continuing problems.