Access to Health Care Improves COVID-19 Vaccination and Mitigates Health Disparities Among Medicare Beneficiaries

Background

COVID-19 disproportionately impacts the elderly, particularly racial/ethnic minorities and those with low socioeconomic status (SES). These latter groups may also have higher vaccine hesitancy. We aim to evaluate if access to care improves COVID-19 vaccination rates and improves health disparities.

Methods

We conducted a retrospective cohort study of Medicare patients receiving care in a high-touch capitated network across ten states. We collected type and date of COVID-19 vaccine and demographic and clinical data from the inpatient and outpatient electronic health records and socioeconomic status from the US census. Our primary outcome was completing vaccination using logistic regression.

Results

Our cohort included 93,224 patients enrolled in the network during the study period. Sixty nine percent of all enrolled patients completed full vaccination. Those who completed vaccination did it with Pfizer (46%), Moderna (49%), and Jannsen (4.6%) vaccines. In adjusted models, we found that the following characteristics increased the odds of being vaccinated: being male, increasing age, BMI, and comorbidities, being Black or Hispanic, having had the flu vaccine in 2020, and increasing number of office primary care visits. Living in a neighborhood with higher social deprivation and having dual Medicaid/Medicare enrollment decreased the odds of completing full vaccination.

Conclusions

Increasing office visit in a high-touch primary care model is associated with higher vaccination rates among elderly populations who belong to racial/ethnic minorities or have low socioeconomic status. However, lower SES and Medicaid populations continue to have difficulty in completing vaccination.

Key points

• High COVID-19 vaccination rates of minorities enrolled in Medicare can be achieved.

• Lower socioeconomic status is associated with completing vaccination.

• Increasing office visits can lead to higher vaccination rates.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40615-022-01343-1.

High Pressure Thermal Sterilization and ε-Polylysine Synergistically Inactivate Bacillus subtilis Spores by Damaging the Inner Membrane

ABSTRACT

This study was conducted to determine the sterilization effect of a combination of high pressure thermal sterilization (HPTS) and ε-polylysine (ε-PL) on Bacillus subtilis spores. The spores were treated with HPTS (550 MPa at 25, 65, and 75°C) and ε-PL at 0.1 and 0.3%. HPTS and ε-PL synergistically decreased the number of surviving spores and increased the release of the intracellular components in the spore suspension, with the maximal effects from treatment with 550 MPa at 75°C plus 0.3% ε-PL. Maximum fluidity and permeability of the cell inner membrane were observed with 550 MPa at 75°C plus 0.3% ε-PL. Changes in membrane lipids were detected from 3,000 to 2,800 cm-1 by Fourier transform infrared spectroscopy. The results provide new insights into the mechanism by which HPTS and ε-PL synergistically sterilize B. subtilis spores.

HIGHLIGHTS

Attitudes and Beliefs of Pediatric Surgical Specialists on Costs of Care and High Deductible Health Plans

Health care consumers are burdened with rising out-of-pocket medical expenses. Surgical specialists' experience and attitude towards patients' out-of-pocket costs and the influence of these factors on healthcare utilization are unknown. Our aim was to define the pediatric surgeons' experience with the financial concerns of their patients. Members from the American Academy of Pediatrics Sections on Plastic Surgery, Surgery and Urology were surveyed. Analysis of variance was used to investigate practice differences. Two hundred and eighteen out of 973 surgeons representing 38 states completed the survey. Nearly half of the surveyed surgeons did not know if cost was a determinant for their patients' choice in surgical facility, or if parents compared costs prior to the visit. Eighty four per cent of the surgeons would consider patient costs if medically appropriate, to entertain less costly alternatives, and adjust surgical scheduling to decrease economic burden. Most pediatric surgical specialists are unaware if out-of-pocket costs influenced patients' preoperative decisions. Nonetheless, they are sympathetic to the issue. As the financial burden of health care shifts to consumers, our survey indicates that surgeons are open to candid discussion surrounding finances and may alter recommendations accordingly if appropriate.

Attitudes and Beliefs of Pediatric Surgical Specialists on Costs of Care and High Deductible Health Plans

Health care consumers are burdened with rising out-of-pocket medical expenses. Surgical specialists’ experience and attitude towards patients’ out-of-pocket costs and the influence of these factors on healthcare utilization are unknown. Our aim was to define the pediatric surgeons’ experience with the financial concerns of their patients. Members from the American Academy of Pediatrics Sections on Plastic Surgery, Surgery and Urology were surveyed. Analysis of variance was used to investigate practice differences. Two hundred and eighteen out of 973 surgeons representing 38 states completed the survey. Nearly half of the surveyed surgeons did not know if cost was a determinant for their patients’ choice in surgical facility, or if parents compared costs prior to the visit. Eighty four per cent of the surgeons would consider patient costs if medically appropriate, to entertain less costly alternatives, and adjust surgical scheduling to decrease economic burden. Most pediatric surgical specialists are unaware if out-of-pocket costs influenced patients’ preoperative decisions. Nonetheless, they are sympathetic to the issue. As the financial burden of health care shifts to consumers, our survey indicates that surgeons are open to candid discussion surrounding finances and may alter recommendations accordingly if appropriate.

Amoxicillin and clavulanate potassium in treating children with suppurative tonsillitis

To evaluate clinical effects of amoxicillin and clavulanate potassium in the treatment of children with suppurative tonsillitis, 146 children with suppurative tonsillitis were randomly divided into a ceftezole sodium group and an amoxicillin and clavulanate potassium group. The two groups were given anti-infection treatment using different drugs. Symptomatic treatment was carried out once symptoms such as fever appeared. Five to seven days were taken as one treatment course. Blood routine examination and the detection of C-reactive protein (CRP) were performed three days after treatment. Indexes such as the time to the relief of symptoms, the count of white blood cells, the proportion of neutrophil and CRP levels and the incidence of adverse reactions were compared between groups to evaluate the curative effect. The overall response rate of the amoxicillin and clavulanate potassium group was 94.52%, while that of the ceftezole sodium group was 78.08%; the difference was statistically significant (P<0.05). The improvement of white blood cells and CRP levels of the amoxicillin and clavulanate potassium group was more obvious than that of the ceftezole sodium group (P<0.05). The difference of the time to the improvement of symptoms between the two groups had statistical significance; the amoxicillin and clavulanate potassium group was superior to the ceftezole sodium group (P<0.05). No severe drug-related adverse reactions were observed. Amoxicillin and clavulanate potassium dispersible tablet is effective in treating children with suppurative tonsillitis as it can rapidly relieve the clinical symptoms without increasing incidence of adverse reactions.

[Analysis and evaluation of droplet digital PCR for H.pylori infections in chronic tonsillitis]

Objective:To investigate the measurement effect of droplet digital PCR(dd-PCR) for H.pylori infections in chronic tonsillitis and explore the correlations between H.pylori infections and chronic tonsillitis.Method:The subjects consisted of 48 chronic tonsillitis patients aged between 7 and 52 years scheduled for tonsillectomy.Core biopsy samples from resected tonsillary tissue was tested for H.pylori detection using both RT-PCR and dd-PCR for the CagA and VacA genes.Preoperative patient venous blood samples were also tested for H.pylori antibodies by Enzyme-linked immunosorbent assay(ELISA).ELISA,RT-PCR and dd-PCR were also used to detect expression of CagA and VacA genes in plasma and tissue of 30 cases of obstructive sleep apnea syndrome(OSAHS) and 35 cases of plasma from healthy subjects.Result:The expression of H.pylori antibodies is tested in plasma:48 chronic tonsillitis patients(10.12±3.23)ng/ml, OSAS(9.87±2.43)ng/ml, healthy subjects(9.34±3.38) ng/ml.There was no significant difference between groups in the plasma.The VacA and CagA gene sequences were detected by RT-PCR:48 chronic tonsillitis patients VacA(27.1%),CagA(16.7%),VacA+CagA(16.7%);30 OSAHS,VacA(23.3%),CagA(20.0%),VacA+CagA(16.7%);all of which were also positive by dd-PCR,thus were considered H.pylori infected.Moreover,The expression of VacA and CagA increased in tissues testing by dd-PCR:48 chronic tonsillitis patients VacA(72.9%),CagA(52.1%),VacA+CagA(39.6%);30 OSAHS,VacA(33.3%),CagA(23.3%),VacA+CagA(16.7%).Conclusion:Our study supports the possible role of H.pylori in chronic tonsillitis.H.pylori maybe one of the risk factors of chronic tonsillitis.dd PCR had bettersensitivity and specificity compare to H.pylori serological and RT PCR.Feasible anti H.pylori treatment maybe used for H.pylori associated chronic tonsillitis.

Subspecialization within pediatric surgical groups in North America

PURPOSE

The purpose of this study was to assess the current status of subspecialization in North American pediatric surgical practices and to evaluate factors associated with subspecialization.

METHODS

A survey was sent to each pediatric surgical practice in the United States and Canada. For each of 44 operation types, ranging in complexity and volume, the respondents chose one of the following responses: 1. everyone does the operation; 2. group policy--only some surgeons do the operation; 3. group policy--anyone can do it but mentorship required; 4. only some do it due to referral patterns; 5. no one in the group does it. Association of various factors with degree of subspecialization was analyzed using nonparametric statistics with p<0.05 considered significant.

RESULTS

Response rate was 70%. There was significant variability in subspecialization among groups. Factors found to be significantly associated with increased subspecialization included free-standing children's hospitals, pediatric surgery training programs, higher number of surgeons, higher case volume, and greater volume of tertiary/quaternary cases.

CONCLUSIONS

There is wide variation in the degree of subspecialization among North American pediatric surgery practices. These data will help to inform ongoing debate around strategies that may be useful in optimizing pediatric surgical care and patient outcomes in the future.

Asymptomatic malrotation: Diagnosis and surgical management: An American Pediatric Surgical Association outcomes and evidence based practice committee systematic review

OBJECTIVE

Patients with malrotation, or an intestinal rotation abnormality (IRA), can experience serious adverse events. Increasingly, asymptomatic patients are being diagnosed with malrotation incidentally. Patients with symptomatic malrotation require surgery in an urgent or semiurgent manner to address their symptoms. The treatment of asymptomatic or incidentally discovered malrotation remains controversial.

METHODS

Data were compiled from a broad search of Medline, Cochrane, Embase and Web of Science from January 1980 through January 2013 for five questions regarding asymptomatic malrotation.

RESULTS

There is minimal evidence to support screening asymptomatic patients. Consideration may be given to operate on asymptomatic patients who are younger in age, while observation may be appropriate in the older patient. If reliably diagnosed, atypical malrotation with a broad-based mesentery and malposition of the duodenum can be observed. Regarding diagnostic imaging, the standard of care for diagnosis remains the upper gastrointestinal contrast study (UGI), ultrasound may be useful for screening. A laparoscopic approach is safe for diagnosis and treatment of rotational abnormalities. Laparoscopy can aid in determining whether a patient has true malrotation with a narrow mesenteric stalk, has nonrotation and minimal risk for volvulus, or has atypical anatomy with malposition of the duodenum. It is reasonable to delay Ladd procedures until after palliation on patients with severe congenital heart disease. Observation can be considered with extensive education for family and caregivers and close clinical follow-up.

CONCLUSIONS

There is a lack of quality data to guide the management of patients with asymptomatic malrotation. Multicenter and prospective data should be collected to better assess the risk profile for this complex group of patients. A multidisciplinary approach involving surgery, cardiology, critical care and the patient's caregivers can help guide a watchful waiting management plan in individual cases.

Postoperative Regimentation Of Treatment Optimizes Care and Optimizes Length of Stay (PROTOCOL) after pyloromyotomy

BACKGROUND/PURPOSE

A non-standardized approach to caring for infants after pyloromyotomy for pyloric stenosis was associated with prolonged postoperative length of stay (pLOS) at our institution. We studied the impact of a standardized postoperative care protocol on pLOS, patients' clinical course, and nursing care.

METHODS

A retrospective chart review identified that 27% of infants who underwent uncomplicated pyloromyotomy had prolonged pLOS, defined as more than one postoperative midnight. A comprehensive postoperative care protocol was developed for infants undergoing pyloromyotomy. Patients were recruited prospectively and those with complications were excluded. A sample size of 70 in each cohort (historic and prospective) allowed 80% power to detect a 50% reduction in the proportion of patients with prolonged pLOS (α=0.05). The prospective group and historic cohort were compared using nonparametric statistics.

RESULTS

The historic cohort had 70 patients and the prospective cohort had 66. Protocol implementation resulted in fewer patients with prolonged pLOS, shorter time to feeds, fewer feeds to discharge, less emesis, and improved nursing documentation.

CONCLUSION

Implementation of a postoperative care protocol improved various aspects of patient care and nursing care studied. Protocols outline a patient's course and serve as a common platform for communication among care providers; they can facilitate, expedite, and enhance patient care.

Prevention of infectious complications after elective colorectal surgery in children: an American Pediatric Surgical Association Outcomes and Clinical Trials Committee comprehensive review

OBJECTIVE

This goal of this review was to examine the clinical evidence in support of commonly utilized measures intended to reduce complications following elective colorectal surgery.

DATA SOURCE

Literature searches were performed to identify relevant studies from Medline, PubMed, and Cochrane databases.

STUDY SELECTION

The American Pediatric Surgery Association Outcomes and Clinical Trials Committee selected eight questions to address this topic systematically in the context of three management areas: 1) appropriate utilization of systemic antibiotics for colorectal procedures, 2) reduction of stool burden through mechanical bowel preparation, and 3) intraluminal gut decontamination through use of enteral nonabsorbable antibiotics. Primary outcomes of interest included the occurrence of infectious and mechanical complications related to stool burden and intraluminal bacterial concentration (incisional surgical site infection, anastomotic leakage, and intraabdominal abscess).

RESULTS

The evidence in support of each management category was systematically reviewed, graded, and summarized in the context of the review's primary outcomes. Practice recommendations were made as deemed appropriate by the committee.

CONCLUSIONS

Clinical evidence in support of interventions to reduce infectious complications following colorectal surgery is derived almost exclusively from the adult literature. High-quality evidence to guide clinical practice in children is sorely needed, as the available data may have only limited relevance to pediatric colorectal diseases.

Systematic literature review of imaging features of spinal degeneration in asymptomatic populations

BACKGROUND AND PURPOSE

Degenerative changes are commonly found in spine imaging but often occur in pain-free individuals as well as those with back pain. We sought to estimate the prevalence, by age, of common degenerative spine conditions by performing a systematic review studying the prevalence of spine degeneration on imaging in asymptomatic individuals.

MATERIALS AND METHODS

We performed a systematic review of articles reporting the prevalence of imaging findings (CT or MR imaging) in asymptomatic individuals from published English literature through April 2014. Two reviewers evaluated each manuscript. We selected age groupings by decade (20, 30, 40, 50, 60, 70, 80 years), determining age-specific prevalence estimates. For each imaging finding, we fit a generalized linear mixed-effects model for the age-specific prevalence estimate clustering in the study, adjusting for the midpoint of the reported age interval.

RESULTS

Thirty-three articles reporting imaging findings for 3110 asymptomatic individuals met our study inclusion criteria. The prevalence of disk degeneration in asymptomatic individuals increased from 37% of 20-year-old individuals to 96% of 80-year-old individuals. Disk bulge prevalence increased from 30% of those 20 years of age to 84% of those 80 years of age. Disk protrusion prevalence increased from 29% of those 20 years of age to 43% of those 80 years of age. The prevalence of annular fissure increased from 19% of those 20 years of age to 29% of those 80 years of age.

CONCLUSIONS

Imaging findings of spine degeneration are present in high proportions of asymptomatic individuals, increasing with age. Many imaging-based degenerative features are likely part of normal aging and unassociated with pain. These imaging findings must be interpreted in the context of the patient's clinical condition.

Optimizing resources for the surgical care of children: an American Pediatric Surgical Association Outcomes and Clinical Trials Committee consensus statement

The United States' healthcare system is facing unprecedented pressures: the healthcare cost curve is not sustainable while the bar of standards and expectations for the quality of care continues to rise. Systems committed to the surgical treatment of children will likely require changes and reorganization. Regardless of these mounting pressures, hospitals must remain focused on providing the best possible care to each child at every encounter. Available clinical expertise and hospital resources should be optimized to match the complexity of the treated condition. Although precise criteria are lacking, there is a growing consensus that the optimal combination of clinical experience and hospital resources must be defined, and efforts toward this goal have been supported by the Regents of the American College of Surgeons, the members of the American Pediatric Surgical Association, and the Society for Pediatric Anesthesia (SPA) Board of Directors. The topic of optimizing outcomes and the discussion of the concepts involved have unfortunately become divisive. Our goals, therefore, are 1) to provide a review of the literature that can provide context for the discussion of regionalization, volume, and optimal resources and promote mutual understanding of these important terms, 2) to review the evidence that has been published to date in pediatric surgery associated with regionalization, volume, and resource, 3) to focus on a specific resource (anesthesia), and the association that this may have with outcomes, and 4) to provide a framework for future research and policy efforts.

Pediatric surgery on YouTube™: is the truth out there?

BACKGROUND/PURPOSE

In 2000, we described the variability of pediatric surgical information on the Internet. Since then, online videos have become an increasingly popular medium for education and personal expression. The purpose of this study was to examine the content and quality of videos related to pediatric surgical diagnoses on the Internet.

METHODS

YouTube™ was searched for videos on gastroschisis, congenital diaphragmatic hernia, pediatric inguinal hernia, and pectus excavatum. The first 40 English language videos for each diagnosis were reviewed for owner and audience characteristics, content and quality.

RESULTS

A small majority of videos were made by medical professionals (50.63%, vs. 41.25% by lay persons and 8.13% by fundraising organizations). Eighty percent of videos were intended for a lay audience. Videos by medical professionals were more accurate and complete than those posted by lay persons.

CONCLUSIONS

The YouTube™ videos varied significantly in content and quality. Videos by lay persons often focused on the emotional aspect of the diagnosis and clinical course. Videos by members of the medical profession tended to be more complete and accurate. These findings underscore the continued need for high quality pediatric surgical information on the Internet for patients and their families.

Inflammatory myofibroblastic tumor of the urinary bladder in a patient with the left renal cell carcinoma: A case report

This case report describes an inflammatory tumor of the urinary bladder along with left renal cell carcinoma which occurred in a 73-year-old male with a narrowed orificium urethrae internum and severe hyperplasia of the prostate gland. A biopsy was not obtained prior to surgery. An inflammatory myofibroblastic tumor (IMT) of the urinary bladder is a rare benign lesion, particularly in the elderly. To the best of our knowledge, there are no studies concerning IMTs of the urinary bladder in patients with unilateral renal cell carcinoma. A bladder lesion due to an IMT may be easily misdiagnosed as metastasis from left renal cell carcinoma due to the hypervascularity of the tumor. In this case, radical surgery of the cancer of the left kidney was performed by laparoscopy. Subsequently, after three weeks and according to the examination of the intraoperative frozen-sections, a partial cystectomy was performed. Thus, radical resection of the bladder and the associated complications were avoided.

Risk-adjusted hospital outcomes for children's surgery

BACKGROUND The American College of Surgeons National Surgical Quality Improvement Program-Pediatric was initiated in 2008 to drive quality improvement in children's surgery. Low mortality and morbidity in previous analyses limited differentiation of hospital performance.

METHODS

Participating institutions included children's units within general hospitals and free-standing children's hospitals. Cases selected by Current Procedural Terminology codes encompassed procedures within pediatric general, otolaryngologic, orthopedic, urologic, plastic, neurologic, thoracic, and gynecologic surgery. Trained personnel abstracted demographic, surgical profile, preoperative, intraoperative, and postoperative variables. Incorporating procedure-specific risk, hierarchical models for 30-day mortality and morbidities were developed with significant predictors identified by stepwise logistic regression. Reliability was estimated to assess the balance of information versus error within models.

RESULTS

In 2011, 46 281 patients from 43 hospitals were accrued; 1467 codes were aggregated into 226 groupings. Overall mortality was 0.3%, composite morbidity 5.8%, and surgical site infection (SSI) 1.8%. Hierarchical models revealed outlier hospitals with above or below expected performance for composite morbidity in the entire cohort, pediatric abdominal subgroup, and spine subgroup; SSI in the entire cohort and pediatric abdominal subgroup; and urinary tract infection in the entire cohort. Based on reliability estimates, mortality discriminates performance poorly due to very low event rate; however, reliable model construction for composite morbidity and SSI that differentiate institutions is feasible.

CONCLUSIONS

The National Surgical Quality Improvement Program-Pediatric expansion has yielded risk-adjusted models to differentiate hospital performance in composite and specific morbidities. However, mortality has low utility as a children's surgery performance indicator. Programmatic improvements have resulted in actionable data.

Retrograde jejunoduodenal intussusception: a rare cause of acute pancreatitis after surgery for duodenal atresia

Duodenojejunostomy is a surgical treatment option in the repair of duodenal atresia. This case describes the heretofore unreported phenomenon of retrograde jejunoduodenal intussusception causing acute pancreatitis in a patient who underwent duodenojejunostomy in infancy.

Rapid growth in infancy: balancing the interests of the child

Low birth weight is associated with a number of immediate adverse consequences, and it has been assumed that "catch-up" growth is a "good thing" because "better" nutritional status is associated with greater childhood health and survival. The same thinking applies to infants who suffer malnutrition and growth faltering during weaning. Recent studies suggest that the rapid postnatal growth of babies is associated with an enhanced risk for obesity, diabetes, hypertension, cardiovascular disease and osteopenia in later life. If this is true, it has implications for our recommendations for infant feeding. Insights from evolutionary biology, life cycle theory, animal husbandry, epidemiology and comparative zoology suggest that the energetic feeding of underweight infants should be considered in the context of the whole life cycle and balance the interests of the child with its likely fortunes in adulthood. Before we revise our current recommendations, we must consider the meaning of catch-up growth, what it involves in terms of tissues gained (fat, muscle and bone) and to what degree association represents causation. In the meantime, it will be prudent to balance the short- and long-term interests of the child by endeavoring to (1) optimize maternal nutrition and health, to avoid low birth weight, (2) breast-feed ideally, (3) consider birth weight, gestation and future "nutritional environment" when making decisions about infant feeding, (4) use appropriate growth charts, (5) avoid excessive postnatal weight gain, (6) think about the whole life span and (7) extrapolate from animal studies cautiously.

Trauma stat and trauma minor: are we making the call appropriately?

OBJECTIVES

Trauma accounts for a significant number of pediatric emergency room visits and is the leading cause of death in pediatric patients over 1 year of age. To provide quality care, protocols are used to mobilize personnel to treat injured patients. We reviewed our experience at a level 1 pediatric trauma center, where a 2-tiered trauma activation protocol is used in treating children with significant injuries.

METHODS

We analyzed data in our trauma registry from 1994 to 1999 of patients with Injury Severity Score > or = 9 in whom trauma activations were called. Data reflected demographics, severity of injury, hospital course and outcome. Trauma activations were based on standard protocols that took physiologic status, anatomic area of injury, and mechanism of injury into account. Nineteen personnel were notified in a Trauma Stat Activation, and 8 were notified in a Trauma Minor Activation.

RESULTS

There were 470 trauma activations: Trauma Stat = 220 and Trauma Minor = 250. As a group, Trauma Stat patients were more hemodynamically unstable, had a lower GCS and a higher Injury Severity Score than Trauma Minor patients. Patients in the Trauma Stat group were also more likely to require intensive care and have a prolonged hospitalization. The Trauma Stat group had a mortality rate of 20%. There were no deaths in the Trauma Minor group.

CONCLUSIONS

Trauma activations result in heavy resource utilization and must be appropriate. The 2 trauma activation levels were associated with differences in injury severity, medical resource utilization, and outcome. With no deaths in the Trauma Minor group and a 20% mortality rate in the Trauma Stat group, we conclude that the protocol used was neither too conservative, nor too liberal.

An analysis of pediatric gunshot wounds treated at a Level I pediatric trauma center

BACKGROUND

We reviewed the incidence and injury severity of children with gunshot wounds (GSWs) at our hospital.

METHODS

We compared trauma registry, emergency unit (EU), and admissions data from January 1993 to June 1996 (period I) and July 1996 to December 1999 (period II). Outcome measures included EU disposition (death, immediate operation, pediatric intensive care unit, ward), injury severity, mortality, and injury cause (accidental, intentional).

RESULTS

We treated 437 children for GSWs in the EU, with 238 (54%) admissions and 199 discharges. Comparing period I versus period II, patients treated declined from 288 to 149 (-52%, p < 0.001), and admissions decreased from 159 to 79 (-50%, p < 0.001). Injury severity increased from 35% to 57% (p < 0.001). Patients requiring immediate operations increased from 20% to 42% (p < 0.001). Direct ward admissions declined from 65% to 43% (p < 0.001). Deaths occurred in 3% of patients in both time periods. Accidental and intentional GSWs were evenly divided.

CONCLUSION

An alarming number of children, an average of 62 children annually, were treated for GSWs at our hospital. Despite a 52% reduction in GSWs, the percentage of severely injured patients increased by 63%. These data emphasize the importance of prevention, education, early assessment, and operative treatment.

Cut it out: Managing hepatic abscesses in patients with chronic granulomatous disease

BACKGROUND

Hepatic abscesses develop in patients with chronic granulomatous disease (CGD) because the liver is a site of constant bacterial challenge. The authors investigated the roles of drainage and hepatic resection in the management of liver abscesses in CGD patients.

METHODS

Medical records of CGD patients with hepatic abscesses from 1990 to 2001 were reviewed.

RESULTS

There were 6 patients. Mean age of initial abscess was 7.2 years (range, 3 weeks to 18.9 years). All abscesses involved the right lobe of the liver (2 single, 4 multiple). All patients received appropriate antibiotics. Four patients were treated with one to 6 drainage procedures over one to 4 admissions before ultimately undergoing resection. The other 2 patients underwent primary resection without preliminary drainage. Of the 6 resections, 4 were nonanatomic, and 2 were anatomic. There was one major postoperative complication (bleeding) requiring reoperation. There were no recurrences after resection (mean follow-up 4.3 yr). Mean total days in hospital for the treatment of liver abscess was 49 in the preliminary drainage group and 8.5 in the primary resection group. Three patients required admission into the intensive care unit, one after a drainage procedure and 2 after resection.

CONCLUSIONS

For CGD patients with hepatic abscesses, drainage procedures are associated with recurrence and prolonged hospitalization. Primary hepatic resection removing all involved tissue is safe and definitive for the management of this problem.

Management of late-stage parapneumonic empyema

PURPOSE

Despite the reported value of early video-assisted thoracoscopic surgery (VATS) for empyema, many children are still referred to the surgeon late in the disease process. The authors wished to determine the optimal management strategy for this group of children.

METHODS

Medical records of all children (n = 70) from 1990 to 2000 with late-presenting empyema (stage II or III) were reviewed. Patients were grouped as (G1) successful management with chest tube (CT), (G2) surgery after initial CT, (G3) thoracentesis followed by surgery, and (G4) surgery alone.

RESULTS

There were no significant differences with respect to age, gender, pleural cultures or fluid analysis. Fifty-one (73%) patients required surgical intervention. Treatment using CT (G1, G2) or thoracentesis (G3) was associated with prolonged length of stay (LOS) when compared with surgery alone (G4; 12 v 8 days). For G2, G3, and G4, rapid clinical improvement and early discharge (6 days) was seen after surgery. For all surgery groups (G2, G3, G4), video-assisted thoracoscopic surgery (n = 19) was associated with a longer postoperative fever (4 v 2 days; P <.05), but a shorter total LOS (12 v 15 days; P <.05) when compared with open decortication (n = 32).

CONCLUSIONS

Over 70% of children with late presenting empyema required surgery, including more than half of the children who received initial chest tube drainage. Delay in surgery was associated with more procedures, more radiographs, and an increased LOS. Despite later intervention, patients undergoing surgery as an initial approach had the shortest length of stay. Early surgical intervention is indicated for most children referred with established empyema.

Gene and protein expressions of nitric oxide synthases in ischemia-reperfused peripheral nerve of the rat

This study examined mRNA and protein expressions of neuronal (nNOS), inducible (iNOS), and endothelial nitric oxide synthases (eNOS) in peripheral nerve after ischemia-reperfusion (I/R). Sixty-six rats were divided into the ischemia only and I/R groups. One sciatic nerve of each animal was used as the experimental side and the opposite untreated nerve as the control. mRNA levels in the nerve were quantitatively measured by competitive PCR, and protein was determined by Western blotting and immunohistochemical staining. The results showed that, after ischemia (2 h), both nNOS and eNOS protein expressions decreased. After I/R (2 h of ischemia followed by 3 h of reperfusion), expression of both nNOS and eNOS mRNA and protein decreased further. In contrast, iNOS mRNA significantly increased after ischemia and was further upregulated (14-fold) after I/R, while iNOS protein was not detected. The results reveal the dynamic expression of individual NOS isoforms during the course of I/R injury. An understanding of this modulation on a cellular and molecular level may lead to understanding the mechanisms of I/R injury and to methods of ameliorating peripheral nerve injury.

Comparison of continuous and interrupted suture techniques in microvascular anastomosis

We evaluated the efficacy of the continuous suture technique (CST) in arteries and veins with varying external diameters (ED). In study 1 a direct end-to-end anastomosis was performed in 5 groups of animals (n = 15 in each group): group 1, rabbit carotid artery (ED, 1.8-2.0 mm); group 2, rabbit femoral artery (ED, 1.4-1.6 mm); group 3, rat femoral artery (ED, 0.7-0.9 mm); group 4, rabbit femoral vein (ED, 2.0-2.2 mm); and group 5, rat femoral vein (ED, 1.0-1.2 mm). In study 2 a graft from the femoral vein was interposed into the carotid artery, with a ratio of the diameter of graft to artery of 1.3:1 in the rats (group 6, n = 12) and 1:1 in the rabbits (group 7, n = 12). In each animal the vessel on one side was repaired using CST and the opposite vessel using the interrupted suture technique. Vessel samples were harvested 1, 2, and 4 weeks after anastomosis. The CST significantly reduced anastomosis time by up to 47% in arteries and 41% in veins. Bleeding time and blood loss were also significantly reduced with CST. Similar results were found in study 2. The total thrombosis rate was 8%, but no significant patency difference was noted between the CST and the interrupted suture technique in any vessel category. We conclude that the CST is a reliable and time-saving procedure in microvascular anastomosis of arteries with diameters greater than 0.7 mm and of veins with diameters greater than 1.0 mm.

Pediatric surgery on the Internet: is the truth out there?

BACKGROUND

The enormous amount of unmonitored medical information on the Internet prompted this investigation into the quality of pediatric surgery information on the Internet.

METHODS

The Internet was searched for information on diaphragmatic hernia (CDH), abdominal wall defects (AWD), pediatric inguinal hernia (IH), and pectus excavatum (PE). Websites were characterized, classified, and evaluated for completeness, accuracy and bias toward or against the medical profession.

RESULTS

A total of 141 websites were evaluated (N(CDH) = 37, N(AWD) = 49, N(IH) = 26, N(PE) = 29). A total of 59.6% targeted medical professionals, and 46.8% targeted the lay population. A total of 58.2% described symptoms and diagnosis. Etiology, pathology, surgery, postoperative course, and prognosis each were addressed by under 40%. A total of 58.2% were accountable for the information presented. A total of 93.1% were incomplete, 75.7% contained accurate information, and 97.7% were positive or neutral toward medical treatment. Among diagnoses, CDH had the highest percentage of websites owned by academic institutions. PE had the highest percentage of websites owned by lay people. PE websites also were the least accurate.

CONCLUSIONS

Internet information on pediatric surgery varies significantly in quality. Lay people own most websites targeted at the lay audience, and the information may not reflect the opinions of most pediatric surgeons. Increasing use of the Internet by parents seeking medical information warrants an organized approach to ensure complete and accurate information online.

Functional effects of lymphotoxin on crushed peripheral nerve

The effect of lymphotoxin (LT) on the functional recovery of crushed peripheral nerves was studied. Using a specially designed compression device, a 5 mm segment of the right sciatic nerve of rats was subjected to a 100 g crush load with a 2 hr duration. The rats in the experimental and control groups received two doses of LT (20 micrograms/kg each) or the same volume of saline, respectively, administered intraperitoneously 24 hr and 1 hr before the procedure. Walking track tests and histologic examinations were performed at intervals up to 56 days after the crush. Motor functional recovery in the LT pretreated group started at day 7 while the crushed limb in the control group remained totally dysfunctional. The sciatic functional index improved faster in the LT group than in the control group during the second week after the crush and reached a significant difference (P < 0.05) at day 18. Subsequently, both groups had a similar evolution. Histologic results paralleled the functional findings. In conclusion, LT can promote motor functional recovery of crushed rat peripheral nerve in the early stage of regeneration.

S-nitroso-N-acetylcysteine protects skeletal muscle against reperfusion injury

The effects of a nitric oxide (NO) donor on microcirculation and contractile function of reperfused skeletal muscle were studied. Rat cremaster muscles underwent 5 hours of ischemia and 90 minutes of reperfusion and were divided into two groups systemically infused with S-nitroso-N-acetylcysteine (SNAC, 100 nmol/min) and phosphate-buffered saline (PBS), respectively. The results showed that the vessels in the SNAC group had more rapid and complete recovery than that in controls. A significant difference was found from 10 to 40 minutes and at 90 minutes in 10-20-microm arterioles, from 10 to 90 minutes in 20-40-microm arterioles, and at 10 and 90 minutes in 40-70-microm arteries. When compared to controls, SNAC-treated muscles showed larger fluorescein filling areas at 15, 30, 60, and 90 minutes and greater isometric tetanic contractile forces in response to stimulation frequencies of 40, 70, 100, and 120 Hz. The data indicate that supplementation of exogenous NO could effectively improve microcirculation and contractile function of skeletal muscle during early reperfusion.

Actions of glucocorticosteroids on ischemic-reperfused muscle and cutaneous tissue

Ischemia-reperfusion injury represents a complex series of vascular and cellular events that resembles an acute inflammatory reaction within the reperfused tissue. This article provides an overview of glucocorticosteroid effects on cells and tissues involved in inflammatory reaction following ischemia-reperfusion of muscle and cutaneous tissue. Glucocorticosteroids exert a variety of effects that influence the microcirculation. These effects include leukocyte recruitment, reduction of vascular permeability, inhibition of formation of cytokines or other mediators, and modulation of enzyme systems involved in inflammation. The current view is that glucocorticosteroids act through cytoplasmic receptors by controlling the transcription of certain genes encoding regulatory proteins, but the exact mechanisms of glucocorticoid action on ischemia-reperfusion are not completely understood. Potential mechanisms may involve modulation of neutrophil and endothelial function, inhibition of formation of arachidonic acid products, and attenuation of lipid peroxidation of biological membranes through membrane stabilization and scavenging of toxic free radicals.

Effects of dexamethasone on the contractile function of reperfused skeletal muscle

This study evaluated the effects of dexamethasone (DXM) on contractile function of reperfused extensor digitalis longus (EDL) muscles following 3-hour ischemia and 24-hour reperfusion. The rats were divided into four groups: normal muscle, ischemia with saline treatment, ischemia/reperfusion with saline treatment, and ischemia/reperfusion with DXM treatment groups. DXM (0.6 mg kg[-1]) or saline (3.0 ml kg[-1]) was administered at 3 hours prior to ischemia. Results showed that although contractile force in all three treated groups was significantly lower than that of normal EDL, the average isometric tetanic contractile force in the DXM-treated group was significantly greater than that in the saline-treated ischemia and ischemia/reperfusion groups. A significant difference was also seen at the peak force and at 5 seconds of the fatigue trains, and with a longer fatigue half-time (FT1/2) in the DXM-treated group than in the other two groups. Histologically, edema, inflammation and necrosis of muscle fiber were less severe in the DXM-treated group than in the saline-treated group. The results indicate that pretreatment with DXM appears to attenuate, but does not completely reverse, the contractile function deficit of ischemic skeletal muscle during the first 24 hours of reperfusion.

Blockade of L-selectin attenuates reperfusion injury in a rat model

Ischemia/reperfusion (I/R) injury appears to be a significant neutrophil-dependent component and may be ameliorated by blocking leukocyte-endothelial adhesion. Using a rat extensor digitorum longus (EDL) muscle model, the present study tested the hypothesis that in vivo administration of the function-blocking monoclonal antibody (mAb) LAM1-116 which recognizes L-selectin, a cell-surface adhesion receptor, could decrease I/R injury. In 46 rats, one EDL served as a normal control and the opposite EDL underwent 3 hr of ischemia followed by 3 hr of reperfusion after pretreatment with LAM1-116 mAb, control IgG, or saline. Myeloperoxidase (MPO) activity showed only a two-fold increase from normal in LAM1-116-treated I/R EDL while a 27-fold increase occurred in the IgG2a and saline groups, with a statistically significant (p < 0.001) difference. A significantly (p < 0.05) lower wet weight ratio, improved fatigue contractile force, and less neutrophil infiltration were found in LAM1-116-treated EDL, when compared to those in control IgG- or saline-treated EDL. The results indicate that blockade of L-selectin by LAM1-116 mAb can effectively reduce neutrophil infiltration in reperfused skeletal muscle, thereby decreasing tissue edema and improving muscle fatigue contractile force. These findings may be important in understanding I/R injury.

End-to-side nerve repair. A review

In recent years, there has been a resurgence of end-to-side peripheral nerve repair. This technique offers a management of a peripheral nerve defect in the absence of a suitable proximal stump. Although numerous animal laboratory investigations demonstrate motor and sensory functional recovery without deleterious effects to the donor nerve, clinical outcomes are yet to be determined.

Interleukin-1 beta promotes functional recovery of crushed peripheral nerve

This study was conducted to elucidate the role of the cytokine interleukin-1 beta on peripheral nerve recovery following crush injuries of two different magnitudes. Eighty-eight female rats were divided into four groups. A 5-mm segment of the right sciatic nerve was subjected to a 100-g crush load for 2 hours in the rats in Groups A1 and B1 or to a 15,000-g crush load for 10 minutes in the rats in Groups A2 and B2. The rats in Groups A1 and A2 received 10 microg/100 g body weight human recombinant interleukin-1 beta intraperitoneally 48, 24, and 1 hours before the nerve injury. The rats in Groups B1 and B2 were treated with an equal volume of normal saline solution with identical schedule guidelines. Walking-track tests (sciatic functional index) performed at intervals until 56 days after the crush and measurements of the contractile force of the extensor digitorum longus muscle made until 28 days were used to evaluate functional recovery of the nerve. During the second week after injury, the rats treated with interleukin-1 beta (A1) had an earlier recovery on the walking track than did those treated with saline solution (B1); this difference reached significance (p < 0.05) at day 11. Although Group A2 demonstrated a trend toward earlier recovery compared with Group B2, there was no significant difference between the two groups. After low or high-load crush injury, tetanic contractile forces were greater in the rats treated with human recombinant interleukin-1 beta than in those treated with saline solution. The results suggest that treatment with human recombinant interleukin-1 beta before crush injury can promote function in the peripheral nerve after the injury. However, the mechanisms that underlie the observed beneficial effects are not completely understood and only speculations can be made.

Influences of inflation rate and duration on vasodilatory effect by intermittent pneumatic compression in distant skeletal muscle

Previous study has demonstrated that application of intermittent pneumatic compression on legs can cause vasodilation in distant skeletal muscle at the microcirculation level. This study evaluated the influence of inflation rate and peak-pressure duration on the vasodilatory effects of intermittent pneumatic compression. The cremaster muscles of 50 male rats were exposed and divided into five groups of 10 each. A specially designed intermittent pneumatic-compression device was applied in a medial-lateral fashion to both legs of all rats for 60 minutes, with an inflation rate and peak-pressure duration of 0.5 and 5 seconds, respectively, in group A, 5 and 0 seconds in group B, 5 and 5 seconds in group C, 10 and 0 seconds in group D, and 10 and 5 seconds in group E. Diameters of arterial segments were measured in vessels of three size categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed that the greatest increase in diameter was produced by intermittent pneumatic compression with the shortest inflation rate (0.5 seconds). A moderate increase resulted from compression with an inflation rate of 5 seconds, and no effective vasodilation occurred during compression with the longest inflation rate (10 seconds). When the groups with different inflation rates but the same peak-pressure duration were compared, there was a significant difference between any two groups among groups A, C, and E and between groups B and D. When the groups with different peak-pressure durations but the same inflation rate were compared, compression with a peak-pressure duration of 5 seconds caused a generally similar degree of diameter change as did compression without inflation at peak pressure. The findings suggest that inflation rate plays an important role in the modulation of distant microcirculation induced by intermittent pneumatic compression whereas peak-pressure duration does not significantly influence the vasodilatory effects of the compression. This may be due to the fact that rapid inflation produces a significant increase in shear stress on the vascular wall, which stimulates vascular endothelium to release nitric oxide, causing systemic vasodilation.

Motor functional and morphological findings following end-to-side neurorrhaphy in the rat model

Nerve repair cannot always be achieved by the conventional end-to-end technique. This study evaluated the functional recovery of nerves repaired with end-to-side neurorrhaphy in a rat model. The right peroneal nerves of 80 female rats were transected and divided into four groups. In group A, the nerve ends were separated and remained unrepaired; in group B, the distal peroneal ends were directly sutured to the epineurium of the tibial nerves in end-to-side fashion; in group C, the distal ends were sutured through an epineurial window at the repair site in end-to-side fashion; and in group D, the nerve ends were reconnected by the traditional end-to-end technique. Evaluation included gait analysis by calculation of a peroneal functional index, measurement of contractile function of the extensor digitorum longus muscle, wet weight of the extensor digitorum longus, and histological examination. The findings of this study suggested the following: (a) end-to-side neurorrhaphy allows effective motor functional recovery, demonstrated by earlier improvement of the peroneal functional index, stronger muscle contractile function, greater muscle weight, and higher density of regenerated axons compared with unrepaired nerves; (b) removal of the epineurium of the donor nerve at the nerve coaptation site increases the effectiveness of end-to-side neurorrhaphy, but the epineurium appears to be a partial barrier to axonal regeneration; (c) removal of the epineurium does not affect the structure and function of the donor nerve; and (d) end-to-end repair achieved the best functional recovery among the four groups; therefore, end-to-side repair should be considered as a potential alternative only when no proximal nerve is available.

Effect of a NOS inhibitor, L-NMMA, on the contractile function of reperfused skeletal muscle

The authors investigated the effect of NG-monomethyl-L-arginine acetate (L-NMMA), a nitric oxide synthase (NOS) inhibitor, on the contractile function of skeletal muscle following ischemia/reperfusion (I/R) injury. The extensor digitorum longus (EDL) muscles of 50 rats were divided into seven groups. Contractile function in non-ischemic EDL did not change statistically significantly with L-NMMA infusion. I/R (1.5 hr I and 3 hr R) significantly decreased EDL contractile function, with an average maximal twitch force of 56 percent of the contralateral normal muscle force and isometric tetanic contractile forces between 47 and 84 percent at four different stimulation frequencies. Following L-NMMA administration at three different dosages, contractile function of I/R muscle decreased in a dose-dependent manner. The highest dosage of L-NMMA (10 micromol/min) reduced the average maximal twitch force to 15 percent and the isometric tetanic contractile forces to between 10 to 23 percent. Histologic evaluation revealed increased edema, neutrophil infiltration, and muscle-fiber necrosis in L-NMMA-infused EDL, compared to the controls. 1) Skeletal muscle contractile function was dose-dependently decreased with the administration of L-NMMA during I/R. 2) The concentrations of L-NMMA used in this study did not influence the function of non-ischemic EDL. These findings suggest that reduction of NO production during I/R is damaging to skeletal muscle function and would impair successful functional outcomes in microsurgical replantation.

Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle

Intermittent pneumatic compression has been established as a method of clinically preventing deep vein thrombosis, but the mechanism has not been documented. This study observed the effects of intermittent pneumatic compression of legs on the microcirculation of distant skeletal muscle. The cremaster muscles of 80 male rats were exposed, a specially designed intermittent pneumatic-compression device was applied to both legs for 60 minutes, and the microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed significant vasodilation in arterial and venous vessels during the application of intermittent pneumatic compression, which disappeared after termination of the compression. The vasodilation reached a maximum 30 minutes after initiation of the compression and could be completely blocked by an inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine (10 micromol/min). A 120-minute infusion of NG-monomethyl-L-arginine, beginning coincident with 60 minutes of intermittent pneumatic compression, resulted in a significant decrease in arterial diameter that remained at almost the same level after termination of the compression. The magnitude of the decrease in diameter in the group treated with intermittent pneumatic compression and NG-monomethyl-L-arginine was comparable with that in the group treated with NG-monomethyl-L-arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermittent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilation.

Recombinant human glial growth factor 2 (rhGGF2) improves functional recovery of crushed peripheral nerve (a double-blind study)

This in vivo double-blind study evaluated the effect of recombinant human glial growth factor 2 (rhGGF2), a Schwann cell mitogen, on the recovery of motor function of rat sciatic nerve following crush injury. Seventy three rats were divided into three groups. Group I (n=5), sham operated; Groups II (n=34) and III (n=34) received a 100 g crush load for 2 h over a 5 mm segment of the sciatic nerve. Group III was treated with 1 mg/kg rhGGF2, via subcutaneous injection one day before nerve crush and daily for the following four days. Group II received an equivalent volume of saline as a control. Motor functional recovery was assessed by calculating the sciatic functional index (SFI) and the recovery rate of tetanic contractile force of the extensor digitorum longus (EDL) muscle. Recovery of nerve function was evident at day 11 after crush in the rhGGF2-treated animals, whereas the nerves in controls were still paralyzed. The rhGGF2-treated animals showed a significant improvement of the SFI between days 11-21 postoperatively when compared to controls. The isometric tetanic contractile force was stronger in the rhGGF2-treated group than in controls, with a significant difference at 40 to 70 Hz stimulus frequencies on day 4. Correlation analysis showed that tetanic contractile force had a linear correlation with the SFI. Histologic assessment indicated that the rhGGF2-treated animals showed less severe degeneration and earlier robust remyelination of axons than controls. The results suggest that treatment with rhGGF2 is effective in promoting nerve regeneration as seen in measurements of functional recovery and qualitative assessment of nerve morphology. The mechanism of GGF's protective effect may be related to its direct action on Schwann cells, stimulating their mitosis as well as inducing neurotrophic factors essential to neuronal maintenance and repair.

Effects of S-nitroso-N-acetylcysteine on contractile function of reperfused skeletal muscle

The ultimate goal of replantation and microsurgical reconstructive operations is to regain or improve impaired function of the tissue. However, the data related to the influence of NO on tissue function are limited. This study evaluated the effects of the NO donor S-nitroso-N-acetylcysteine (SNAC) on contractile function of skeletal muscle during reperfusion. Forty-nine rats were divided into six groups. The extensor digitorum longus (EDL) muscles in groups I and II were not subjected to ischemia-reperfusion but were treated with a low (100 nmol/min) or high (1 mumol/min) dose of SNAC. In groups III-V, the EDL underwent 3 h of ischemia and 3 h of reperfusion and was also treated with low (100 nmol/min) or high doses (1 or 5 mumol/min) of SNAC. Group VI was a phosphate-buffered saline (PBS)-treated control group. Twenty additional animals were used to document systemic effects of SNAC and PBS only. SNAC or PBS was infused for 6.5 h, beginning 30 min before ischemia and continuing throughout the duration of reperfusion. Contractile testing compared the maximal twitch force, isometric tetanic contractile forces, fatigue, and fatigue half time of the experimental EDL and the contralateral nontreated EDL. The findings indicate that 1) SNAC does not influence contractile function of EDL muscle not subjected to ischemia-reperfusion, 2) SNAC significantly protects the contractile function of ischemic skeletal muscle against reperfusion injury in the early reperfusion period, and 3) the protective role of SNAC is critically dosage dependent; protection is lost at higher doses. The conclusion from this study is that supplementation with exogenous NO exerts a protective effect on the tissue against reperfusion injury.

Studies of ischemia-reperfusion injury in skeletal muscle: efficacy of 21-aminosteroids on microcirculation and muscle contraction after an extended period of warm ischemia

The present study was conducted to elucidate the effects of tirilazad mesylate (U-74006F), a potent inhibitor of lipid peroxidation, on vessel diameter, capillary perfusion, and contractile function of rat cremaster muscle during a 90-minute reperfusion period that followed 4 hours of warm ischemia. Two groups of 32 animals were treated with either 3 mg/kg U-74006F or the vehicle (citrate buffer) alone 30 minutes before ischemia, 90 minutes after ischemia, and immediately before reperfusion. With use of intravital videomicroscopy, the internal luminal diameters of preselected vessels were measured prior to ischemia and during reperfusion. The area that filled with fluorescein was determined at 15-minute intervals for as long as 90 minutes of reperfusion, and contractile function was examined in vitro in an organ bath at that point. In the U-74006F group, after 90 minutes of reperfusion the vessel diameters returned completely to baseline and the diameters of all three categories of vessels at every time point from 10 to 90 minutes of reperfusion had significantly more rapid recovery than the controls. Although some evidence of more rapid fluorescence was noted in the U-74006F group, the two groups did not differ significantly at any time period of reperfusion. In response to tetanic stimulation, the muscles treated with U-74006F had a significantly greater contractile force at all stimulation frequencies than the control muscles. Our findings indicate that pretreatment with U-74006F can effectively decrease the rise of vascular resistance and preserve the contractile function of skeletal muscle during early reperfusion, thereby attenuating ischemia-reperfusion injury.

Antithrombotic potencies of enoxaparin in microvascular surgery: influence of dose and administration methods on patency rate of crushed arterial anastomoses

This study evaluated the influence of the dose and administration methods of enoxaparin, a low-molecular-weight heparin, on the patency rate of crushed rat femoral arteries following anastomosis. An impact crush with a 25-kg magnitude was applied to a 2-mm segment of 100 rat femoral arteries, followed by anastomosis. The arteries were divided into five groups: group 1 received systemic enoxaparin alone with a relatively high dose (45 IU) twice a day for 3 days; groups 2 and 3 received topical irrigation with a lower (15 IU/mL) concentration and a higher (45 IU/mL) concentration, respectively; group 4 received systemic and topical application at a lower (15 IU) dose and concentration (15 IU/mL); and group 5 received systemic and topical application at a higher (45 IU) dose and concentration (45 IU/mL). The results of this study demonstrate the following: (1) topical irrigation with enoxaparin at a concentration of 45 IU/mL-three times higher than that recommended for clinical use adjusted by body weight (15 IU/mL)-is effective for antithrombotic action; (2) a combination of systemic and local application does not offer additional benefit in the patency rate when compared to local irrigation alone; (3) systemic administration alone does not prevent thrombus formation; and (4) enoxaparin is potentially useful to enhance the patency rate in compromised microvessels.

Calcitonin gene-related peptide and reperfusion injury

Calcitonin gene-related peptide is a potent intrinsic vasodilator, can induce prostacyclin release, and may inhibit membrane lipid peroxidation. This study examines the effect of calcitonin gene-related peptide on vessel diameters, capillary perfusion, and contractile function of skeletal muscle after 4 or 5 hours of ischemia and during immediate reperfusion using the rat cremaster muscle model. Forty-two male rats were used; half of these received 0.2 ml of 10(-7) M calcitonin gene-related peptide after 0, 15, and 30 minutes of reperfusion, while the other half received normal saline as a control. By means of intravital videomicroscopy, the diameters of 10 vessels per muscle were measured prior to ischemia and during reperfusion. The fluorescein filling area was determined at 15, 30, and 60 minutes of reperfusion. After 1 hour of reperfusion, muscle function was examined in vitro by quantifying the contractile response to electric field stimulation of the muscles in an organ bath system. There was a significant increase in the diameter of the arterioles, but not the small arteries, at every time point from 10 to 60 minutes of reperfusion. The fluorescein filling area was increased in treated muscles at every time point. Contractile function was not significantly preserved. In light of the ability of calcitonin gene-related peptide to relieve vasospasm and improve capillary perfusion, it may be useful in reducing reperfusion injury in the future.

Assessment of ischemia and reperfusion injury

Direct videomicroscopy of the rat cremaster muscle microcirculation supplemented by animal models of replantation, vascular crushing, and muscle function after injury and recovery were used to investigate the occurrence of reperfusion failure. It is evident that failure of blood reflow may be induced by multiple factors that can be grouped into categories of ischemia, intimal damage, and systemic or local responses, which are referred to as the no reflow triad. The components comprising the 3 sides of the no reflow triad can interact with one another in an intricate manner, and any single factor or combination of factors is capable of triggering the events leading to reperfusion failure. The pronounced regional nature of reperfusion injury and the direct relationship between the severity of the observed vascular alterations and increasing duration of ischemia have been documented. The dynamic changes and histopathology of the microcirculation included constriction of the arteries, swelling of endothelial and leukocytes, and erythrocyte rouleaux formation during ischemia. As ischemia duration was lengthened, the degree of these changes increased correspondingly. The changes on reperfusion were disruption of blood flow patterns, vortex formation, regional stasis, adhesion and migration of leukocytes, focal hemorrhage, edema, vasospasm, and platelet aggregation. The deleterious effects of systemic acidosis, interstitial hemorrhage, denervation, and prolonged venous occlusion were subsequently documented. The application of information gained from this series of laboratory experiments has resulted in continued improvement in the success rate in clinical microvascular surgery.

Protective effect of 21-aminosteroid pretreatment in peripheral nerve low-load crush injury in mature and immature rats

The effects of U-74006F (tirilazad mesylate), a 21-aminosteroid antioxidant, on injured peripheral nerve were studied. Twenty-two immature and 44 mature rats were divided equally into two groups. The experimental group received two injections of 3 mg/kg of U-74006F at a 2 hour interval. The control group received the same volumes of a citrate buffer. A 5 mm segment of the sciatic nerve was subjected to a crush load of 100 g for 2 hours. Motor function (sciatic functional index) was assessed to day 48 postoperatively. There was total paralysis of the crushed limb in all rats the first week after crushing. The experimental group had a statistically significant improvement in motor function compared with the controls on days 14, 21, 25, and 28 for the mature rats and on days 11 and 14 for the immature rats. The mature controls attained complete recovery on day 42 and had a significantly slower recovery rate than the immature controls, which had recovered fully by day 25. The recovery rates were almost similar among mature and immature groups pretreated with U-74006F, both of which had fully recovered motor function by day 28. The results indicate that pretreatment with U-74006F can significantly promote peripheral nerve function after low-load crush injury and that the age of the animal influences the rate of peripheral nerve recovery.

Tumor necrosis factor promotes motor functional recovery in crushed peripheral nerve

The potential benefits of tumor necrosis factor pretreatment in promoting motor functional recovery of peripheral nerve following low load crush injury were examined. Using a specially designed crush device, rat sciatic nerve was subjected to a low load crush injury of 2-h duration. Recombinant murine tumor necrosis factor and saline were intraperitoneally injected into the experimental and control animals, respectively, prior to nerve crushing. Subsequent motor function was evaluated at intervals by measurement of the sciatic functional index. There was significantly (P < 0.05 to < 0.01) more rapid recovery in the tumor necrosis factor pretreated group as compared to the controls between day 14 and day 28. The sciatic functional index in the tumor necrosis factor group improved to -69.3 +/- 5.3 at day 14 and to nearly normal at day 21. In contrast, the sciatic functional index in the control group was -95.5 +/- 3.1% at day 14 and did not approach normal until day 42. Histological results paralleled the functional findings. The results suggest that tumor necrosis factor pretreatment has the potential to attenuate neurostructural damage and promote motor functional recovery in rat peripheral nerve.

Protective effect of hypothermia on contractile force in skeletal muscle

The clinical success of limb replantation and tissue transfer is partly dependent on the duration of ischemia experienced by the amputated part. This study focused primarily on the damage that occurs during this ischemic period. An experimental system was implemented that allowed the observation of contractile function in totally isolated skeletal muscle after ischemia. Contractile function was selected as an indicator of ischemic damage because normal function is the ultimate goal of replantation. All experiments were performed on the rat extensor digitorum longus. The muscles were subjected to ischemic periods of 1.5, 3.0, and 5.0 hours and were stored in either a hypothermic (4 degrees C) or a room-temperature (23 degrees C) environment during the ischemic interval. After the ischemic period, all muscles were transferred to a tissue bath and were subjected to contractility testing, followed by fatigue testing. In both groups, muscle function decreased as the ischemic interval was increased. A significant difference in function between the normal control and the muscles of both ischemic groups implied that ischemic injury had occurred in the hypothermic and room-temperature muscles, even with the relatively short 1.5-hour ischemic interval. After each ischemic interval however, the hypothermic muscles produced significantly greater contractile force than the room-temperature muscles in both the contractility and the fatigue tests. After 1.5 hours of ischemia, the contractile force in the hypothermic group was about three times as great as that observed in the room-temperature group. These results indicated that muscle function after a period of totally isolated ischemia is protected by hypothermic preservation. They also support the advisability of storage of amputated parts and free muscle flaps in hypothermic environments before replantation even after relatively brief intervals of ischemia.

Thrombosis and thrombolysis in crushed arteries with or without anastomosis: a new microvascular thrombosis model

This study introduces a new rat thrombosis model in which a 2-mm segment of femoral artery is crushed by an impact load. Ninety-five femoral arteries were divided into five groups. The vessels in Groups I and 2 underwent only crush injuries with a 15-kg and 25-kg load, respectively. Group 3 vessels were not crushed, but did undergo vessel anastomosis by a standard microsurgical technique. The vessels in Groups 4 and 5 were crushed by a 25-kg load, and then divided and anastomosed. During the procedure, the vessel lumina were topically irrigated with saline (Group 4) or heparin solution (Group 5). Thrombosis and thrombolysis were evaluated at set time points up to 56 days after operation. While all vessels in Groups 1 and 3 remained patent, the rate of occlusive thrombus formation in Group 2 significantly (p < 0.001) dropped from 85 percent at day 1 to 11 percent at day 7. The intima and media in Groups 4 and 5 were severely disrupted and often occluded the lumen, Group 5 had a significantly (p < 0.01 to 0.001) lower rate of occlusive thrombus formation (40 to 45 percent) at days 1 and 7 than Group 4 (90 percent). Histology in Groups 2, 4, and 5 at day 1 showed no intimnal and almost no medial tissue left in the crushed area. The adventitia and remaining external elastic lamina were adherent to thrombus in the occluded vessels or covered by fibrin and platelet mesh in the patent vessels. The results documented that spontaneous thrombolysis occurs in thrombosed arteries following crush injury alone, but not in thrombosed arteries after crush injury followed by suture anastomoses. The degree of disruption of the internal elastic lamina and the presence of sutures appear to contribute to occlusive thrombus formation following crush injury and anastomoses. Topical irrigation with heparin solution, at the concentration routinely used clinically, significantly reduces the thrombosis rate at the anastomosis site in crushed vessels, but does not promote thrombolysis.

The effect of exposure time on microsurgical anastomoses of experimentally crushed arteries

Replantation after crushing amputation has a relatively low success rate. Although the mechanism of trauma is a major factor in failure, the time lapse before vessel anastomosis may also be a contributing factor. In this study, we observed the influence of the interval between vessel injury and surgical treatment on thrombus formation and healing after controlled crushing. Seventy-five Sprague-Dawley rats were used. A segment of femoral artery was clamped to create warm ischemia for 8 hours and crushed with a 15 kg load for one hour. After the loading device was removed the crushed segments were transected and the vessel ends exposed to the adjacent tissues and blood for 0, 2, 4 and 6 hours (groups II-V, respectively) prior to being anastomosed with standard microsurgical technique. The vessel samples were harvested at days 1, 2 and 7, respectively, and evaluated by light microscopy and scanning electron microscopy (SEM). The patency rate of the anastomoses was 97.3% at harvest and reendothelialization was completed at day 7. Three anastomoses with 4 or 6 hours exposure showed thrombosis, or clotting. The results indicated that up to 6 hours exposure time did not have a significant influence on thrombus formation or the healing process of vessels under the controlled conditions of this study.

Efficacy of recombinant human manganese superoxide dismutase compared to allopurinol in protection of ischemic skeletal muscle against "no-reflow"

A growing body of experimental data indicates that the "no-reflow" phenomenon is a type of reperfusion injury in skeletal muscle which may, in part, be mediated by oxygen free radicals, and thus may be attenuated by using agents that scavenge or inhibit formation of these reactive oxygen metabolites. This study was undertaken to assess the efficacy of recombinant human manganese superoxide dismutase (rhMnSOD) in reducing reperfusion injury in skeletal muscle. The specific advantage of this agent over other SOD types is a much longer plasma half-life (5 to 7 hr), allowing better equilibration between extra- and intracellular compartments. The rat cremaster model was used to study "no-reflow" in skeletal muscle. Reperfusion injury in the muscle was assessed by fluorescein dye perfusion, myocyte creatine phosphokinase (CPK) release, and contractile function in response to electrical field stimulation. Compared with untreated saline control animals, those treated with rhMnSOD after 5 hr of cremasteric ischemia, had a significantly higher percentage area of blood reflow (78 percent +/- 6 percent of normal), a greater percentage tetanic (66 percent +/- 9 percent of normal) and twitch (56 percent +/- 9 percent of normal) contractile strength, and less CPK release (21.5 percent higher than pre-reperfusion baseline CPK levels) (p < 0.05). Untreated saline control CPK release (21.5 percent higher than the prereperfusion level. Animals treated with allopurinol also had a significantly higher percentage twitch contraction (47 percent +/- 14 percent of normal) and a lower CPK release (11.1 percent of the prereperfusion value) 45 min after reperfusion than untreated saline controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology and related studies of the no reflow phenomenon in skeletal muscle

Although the success rate of microvascular replantation and revascularization procedures has increased steadily since the 1960s, some replanted tissues do not reperfuse despite technically adequate arterial anastomoses. This failure of microvascular perfusion is termed no reflow. Much research has been directed toward discovering the etiology of no reflow since it was first described 25 years ago. Three pathophysiologic processes have been identified as playing a central role in the development of no reflow: intracellular calcium overload, oxygen-free radical medicated damage, and altered arachidonic acid metabolism. The first tissue believed to be injured irreversibly by these processes is the endothelium, which leads to dysfunction of the parenchymal cells. All 3 pathways are interrelated extensively, which allows for pharmacologic intervention at many different steps. Agents that have been shown to be beneficial in preventing no reflow include calcium channel blockers, prostaglandin analogs, thromboxane synthesis inhibitors, vasodilators, thrombolytics, and many antioxidants. Although they have been shown to be effective in various laboratory models, additional investigation is necessary before these treatments can be established in clinical use.