Infants tolerate spinal anesthesia with minimal overall autonomic changes: analysis of heart rate variability in former premature infants undergoing hernia repair

Unlike adults, neonates tolerate high thoracic spinal anesthesia with minimal changes in heart rate (HR) and arterial blood pressure. To examine the potential autonomic regulatory mechanisms which may account for these findings, the relation between short-term heart rate variability (HRV) and respiratory activity was analyzed in a group of eight ASA grade II former premature infants undergoing high thoracic spinal anesthesia for inguinal hernia repairs. Quantitative measures of sympathetic (As) and parasympathetic (Ap) modulation of HR were derived. HR, arterial blood pressure, and a calibrated respiratory signal were recorded during 4.4-min stable epochs in eight subjects 1) preoperatively, 2) postincision after high thoracic spinal anesthesia, and 3) during an active sleep state in the postoperative period. Power spectral analysis of HRV and respiratory power yielded measures of low-frequency power (LFP: 0.02-0.15 Hz) and high-frequency power (HFP: 0.15-0.8 Hz). Transfer function analysis between respiratory activity and HR were used to quantify As and Ap. All subjects had successful high thoracic spinal anesthesia with highest levels ranging from C7-T4. Mean HR, blood pressure, and respiratory power did not change significantly with high thoracic spinal anesthesia. LFP and HFP both decreased significantly, whereas the LFP/HFP ratio remained stable. Group mean As and Ap both decreased, but the changes were not significant. Despite overall cardiovascular stability, HRV decreased with high thoracic spinal anesthesia, but the balance between LFP and HFP remained stable, suggesting that the reflex response to high thoracic spinal anesthesia was predominantly diminished parasympathetic modulation of cardiac function. The expected decrease in HR and blood pressure from the sympatholysis which results from high thoracic spinal anesthesia were apparently offset by withdrawal of cardiac vagal activity.

Measurement of prostate movement over the course of routine radiotherapy using implanted markers

PURPOSE

To measure the range and frequency of occurrence of intertreatment movement of the prostate gland over the course of radiotherapy, and to demonstrate that the prostate may move independently of the surrounding bones of the pelvis.

METHODS AND MATERIALS

Ten patients underwent implantation of radiopaque markers around the prostate. Orthogonal portal films were taken at multiple stages during the course of treatment and digitized. An image registration tool was used to solve for film detector placement and, subsequently, to determine positional changes between structures on a reference portal image pair and all subsequent pairs for each patient. Transformations describing prostate movement were measured independently of those describing setup variations of the pelvic girdle.

RESULTS

Translation and/or rotation of the prostate was detected in 70% of the treatments for which films were taken. The maximum measured displacement was 7.5 mm along a major axis. Typical translations of the prostate were between 0-4 mm. The translation and rotation had a predominant direction, suggesting a natural axis for prostate movement.

CONCLUSION

Although significant prostate displacement can occur between treatments, the typical range of movement seen along a major axis was less than 5 mm. Proper treatment planning should consider the movement of the target independent of surrounding bony anatomy. Advances in online portal imaging, image registration, and dynamic field shaping may permit shaped fields that encompass the prostate gland in its position at the time of treatment, allowing for the use of smaller fields while ensuring proper target coverage.

Mechanism of electrical enhancement of efficacy of antibiotics in killing biofilm bacteria

The bioelectric effect, in which electric fields are used to enhance the efficacy of biocides and antibiotics in killing biofilm bacteria, has been shown to reduce the very high concentrations of these antibacterial agents needed to kill biofilm bacteria to levels very close to those needed to kill planktonic (floating) bacteria of the same species. In this report, we show that biofilm bacteria are readily killed by an antibiotic on all areas of the active electrodes and on the surfaces of conductive elements that lie within the electric field but do not themselves function as electrodes. Considerations of electrode geometry indicate that very low (< 100 microA/cm2) current densities may be effective in this electrical enhancement of antibiotic efficacy against biofilm bacteria, and flow experiments indicate that this bioelectric effect does not appear to depend entirely on the possible local electrochemical generation of antibacterial molecules or ions. These data are expected to facilitate the use of the bioelectric effect in the prevention and treatment of device-related bacterial infections that are caused by bacteria that grow in biofilms and thereby frustrate antibiotic chemotherapy.

Multifocal nature of adenolymphoma of the parotid

The multifocal nature of adenolymphoma of the parotid salivary gland was studied in 24 patients who underwent parotidectomy. Twenty-six resected specimens were examined by a step-serial whole-organ sectioning technique; multiple adenolymphoma was found in 13. The maximum number of synchronous tumours in any gland was four. Salivary epithelial elements were found embedded within lymph nodes in nine resected specimens. Synchronous or metachronous bilateral tumours were found in eight patients. The multifocal nature of adenolymphoma of the parotid gland is demonstrated.

Recurrence of laryngeal or hypopharyngeal primary tumor after radical neck dissection for postradiotherapy neck nodal metastases

BACKGROUND

When the primary tumor in the larynx or hypopharynx responds well to radiotherapy, nodal metastasis in the neck may persist or recur. The primary site is usually left alone when no lesion is evident, but its long-term control is uncertain.

METHODS

Radical neck dissection was performed in 23 patients who had nodal metastasis, while the primary tumor in the larynx or hypopharynx was controlled after radiotherapy. The primary site was left alone and kept under surveillance.

RESULTS

Seven patients (30%) had recurrence at the primary site on follow-up. Two significant risk factors for development of recurrences at the primary site were identified; the neck node staging at presentation (p < 0.03) and presentation with persistent neck lymph nodes (p < 0.03). The 2-year survival of those patients with recurrences at the primary site was 29%.

CONCLUSION

Radical neck dissection alone was justified, but close surveillance of the primary site after surgery is mandatory, especially for those patients with high-risk factors.

The phosphatidylinositol 3-kinase serine kinase phosphorylates IRS-1. Stimulation by insulin and inhibition by Wortmannin

Phosphatidylinositol 3-kinase (PI 3-kinase) is a heterodimer composed of an 85-kDa subunit that binds tyrosyl-phosphorylated proteins via its SH2 domains and a 110-kDa catalytic subunit. Expression and mutagenesis experiments have shown that the 110-kDa subunit is a dual specificity kinase that possesses both lipid and serine kinase activities. Except for the 85- and 110-kDa subunits of PI 3-kinase, however, no endogenous substrates for the serine kinase have been identified. The results of the present study show that another target of this kinase is the insulin receptor substrate, IRS-1. Serine phosphorylation of IRS-1 as well as the 85-kDa subunit of PI 3-kinase was demonstrated in immunoprecipitates of PI 3-kinase and IRS-1 isolated from rat adipocytes incubated with insulin. In adipocytes incubated in the absence of insulin, only the serine phosphorylation of p85 was observed in immunoprecipitates of PI 3-kinase. Both the serine and lipid kinase activities of PI 3-kinase were abolished by the fungal metabolite Wortmannin. Wortmannin also partially inhibited the ability of insulin to stimulate glucose transport and inhibit lipolysis in fat cells. These data raise the possibility that the serine kinase activity of PI 3-kinase is involved in insulin signaling. They also suggest that inhibition of the lipid or serine kinase activities of PI 3-kinase could explain the effect of Wortmannin to diminish insulin action.

Degradation and intrahepatic compatibility of albumin-heparin conjugate microspheres

The in vitro degradation properties of glutaraldehyde cross-linked albumin and albumin-heparin conjugate microspheres (AMS and AHCMS respectively) were evaluated using light microscopy, turbidity measurements and heparin release determinations, showing that the microspheres are degraded by proteolytic enzymes such as trypsin, proteinase K and lysosomal enzymes. The degradation rate was inversely related to the cross-link density of the microspheres. After intrahepatic administration of AHCMS, cross-linked with 0.5% glutaraldehyde, to male Wag/Rij rats by injection into a mesenteric vein (intravenoportal: i.v.p.), the microspheres were entrapped in the hepatic vascular system. The AHCMS were entrapped within terminal portal veins predominantly at the periphery of the liver. The AHCMS were degraded by cellular enzymatic processes within 2 wk after injection, with a half life of approximately 1 d. Biocompatibility of AHCMS and adriamycin-loaded AHCMS was evaluated by histological assessment of the mitotic activity of liver parenchyma and inflammatory response, and by determination of liver damage marker enzymes during 4 wk after administration. Liver damage marker enzymes were not increased compared with controls, nor were adverse effects observed upon histological examination. There was no difference in response between empty and adriamycin-loaded AHCMS.

Decreased bone mineral density in premenopausal asthma patients receiving long-term inhaled steroids

Inhaled corticosteroids have become a key element in the maintenance treatment of bronchial asthma. It is well-known that long-term systemic steroid use causes osteoporosis, whereas its inhaled counterpart has been believed to be devoid of such a side-effect. However, recent studies showed that administration of inhaled corticosteroids was associated with biochemical evidence of derangement in bone turnover. We therefore studied bone mineral density (BMD) by dual energy x-ray absorptiometry in 30 patients (18 females, 12 males) with bronchial asthma treated with steroids, essentially by the inhaled route only (both nasal and tracheobronchial), and compared them with healthy subjects individually matched for age, sex, menopausal status, and body mass index (BMI). There was a significant decrease in BMD in the patient group at the hip (neck of femur, p = 0.007; trochanter of femur, p = 0.034; Ward's triangle, p = 0.016) and the lumbar area of the spine (L2-4, p = 0.041). Further analysis showed that this difference from control subjects was mainly seen in the female patients and not in the male patients (neck of femur, p = 0.049; Ward's triangle, p = 0.025; lumbar spine, p = 0.039). In the female patients, there was significant negative correlation of BMD of the lumbar area of the spine and the trochanter of femur with daily inhaled steroid dose and positive correlation of BMD of the trochanter with BMI.

Outmigration of foreign-born members in Canada

"This paper studies the partial effect of various socio-economic characteristics on the rate of outmigration of the foreign-born from the Canadian population. The data sets used are based on the microdata of the 1971 and 1981 censuses of population. It is found that migrants with high school education have the highest propensity to outmigrate, while those with less than high school education have the lowest. The propensity to outmigrate is positively related to the age of the migrant. Males tend to have a higher propensity to outmigrate, while having a command of official languages reduces the propensity to outmigrate." (SUMMARY IN FRE)

Hydrophobic bile salt inhibits bacterial adhesion on biliary stent material

Blockage of indwelling biliary stents is caused by biliary sludge, which forms as a result of bacteria adhering to the surface of the stent material and forming adherent biofilm. As the adherence of bacteria on plastic surface involves hydrophobic interaction of the plastic polymer and the bacterial cell wall, we tested if the detergent property of bile salts might retard bacterial adherence. Three common biliary pathogens isolated from the bile of patients suffering from acute suppurative cholangitis were used in this experiment: E. coli (O21:H25) which form pili and a glycocalyx; E. coli (O101:H9), non-piliated but with a glycocalyx, and Enterococcus fecalis without either pili or a glycocalyx. Polyethylene disks (1 cm2 diameter) were used for the in vitro adhesion study. They were continuously perfused by the bacterial suspension, flowing at 50 ml/hr at 37 degrees C for 24 hr. The suspending media used were sterile human bile and tryptic soy broth. Two different bile salts, taurocholate and taurodeoxycholate, were added to the perfusion media. The number of bacteria adhering to the surface was assessed by viable bacterial count, epifluorescence microscopy, and scanning electron microscopy. The results showed that E. coli (O21:H25) exhibited better adherence than the nonpiliated E. coli (O101:H9), which in turn was better than the non-pili-, non-glycocalyx-producing Enterococcus fecalis. When a more hydrophobic bile salt, taurodeoxycholate, was added at 25 or 50 mM to the tryptic soy broth or to the human bile, the adherence of the two E. coli strains were reduced 100- to 1000-fold (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Tracheostomal stenosis after total laryngectomy: an analysis of predisposing clinical factors

Stenosis of the terminal tracheostome is a distressing complication of total laryngectomy. A retrospective analysis of 207 patients who underwent total laryngectomy is presented; an overall incidence of tracheostomal stenosis of 13% is reported. The incidence of tracheostomal stenosis is higher in females (26%), patients having immediate tracheoesophageal puncture (19%), pectoralis major myocutaneous flap pharyngeal reconstruction (26%), and tracheostomal infection (50%) which is shown to be significant (P < .05). However, on multivariate analysis, only female sex and tracheostomal infection are independent determinants. Recognition of these clinical factors identifies patients at increased risk of developing this complication and thus allows appropriate perioperative planning to minimize its incidence.

The effect of phagocytosis of poly(L-lactic acid) fragments on cellular morphology and viability

The aim of this study was to investigate the effect of phagocytosed poly(L-lactic acid) particles on the morphology and viability of phagocytes, mainly macrophages. Therefore, predegraded poly(L-lactic acid) (P-PLLA) and nontreated PLLA (N-PLLA) particles, both having diameters not exceeding 38 microns, were injected intraperitoneally in mice. P-PLLA particles were obtained by 25 kGy gamma-irradiation of N-PLLA particles. N-PLLA and P-PLLA particles were injected using an 0.3% ethanol/0.9% saline solution intraperitoneally to the mice. We also studied the release of the absorbed ethanol as a possible model for the release of low molecular weight, potentially toxic products. As control, nondegradable polytetrafluoroethylene (PTFE) particles and the carrier solution were used. After 1, 2, 3, 4, 5, and 7 days, the cells of the abdominal cavity were harvested to study the effect of phagocytosis of polymer particles on phagocytic cell morphology and viability. Studies with transmission electron microscopy indicated that, upon injection of particles in the peritoneal cavity, macrophages demonstrated signs of cell damage, cell death, and cell lysis due to phagocytosis of a large amount of P-PLLA particles. The morphology of the cells that had phagocytosed the N-PLLA and PTFE particles did not differ substantially from those of control animals in which only the solution was injected. Also, in the controls, hardly any cell death and no debris was observed. When the PLLA particles were injected as a suspension in a 0.3% ethanol/0.9% saline solution, no difference was observed between N-PLLA and P-PLLA. After phagocytosis, both cause cell damage, sometimes leading to cell death.(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of multiple forms of peptidase inhibitors in rat milk

Peptides such as somatostatin (SS14), epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha), and insulin-like growth factors (IGF-I and IGF-II) are present in breast milk from various species, and their significance in the developing gastrointestinal tract has been suggested. Our recent studies have indicated that rat milk soluble fraction (RMSF) protects SS14 in the gastrointestinal lumen by inhibiting in vitro the luminal peptidolysis. In the present studies, we have shown that RMSF inhibited in vitro degradation by midjejunal luminal flushings of suckling rats of 125I-labeled somatostatin 14[Tyr11], EGF, TGF alpha, IGF-I and IGF-II, as well as trypsin activity in vitro against benzoyl-L-arginyl-p-nitroanilide. The inhibitory factors present in the RMSF were further fractionated by gel filtration on Sephadex G100, ion-exchange chromatography on DEAE-Sephadex, and fast protein liquid chromatography (FPLC). Gel filtration of Sephadex G100 separated RMSF into three peaks of proteins: G1, G2, and G3; peptidase inhibitor activities were present exclusively in G1. Ion-exchange chromatography on DEAE-Sephadex column resolved peptidase inhibitory activity (G1) into three different peaks, D1, D2, and D3, eluted at sodium chloride concentrations of 0.05 M, 0.1 M, and 0.2 M, respectively. Further purification of D2 by FPLC resulted in a fraction rich in peptidase inhibitory activity, which was essentially free of trypsin inhibitory activity. Results indicate the presence of at least three peptidase inhibitors in rat milk, which may play a role in the protection of milk-borne peptides in the gastrointestinal lumen.

Squamous cell carcinoma of the hypopharynx--analysis of treatment results

The results of surgical treatment and causes of failure in 109 patients with squamous cell carcinoma of the hypopharynx were analyzed. The 5-year survival was significantly related to the stage of the disease (stage I, 74%; stage II, 63%; stage III, 32%; and stage IV, 14%) and the preoperative nodal staging (N0, 57%; N1, 28%; N2, 6%; and N3, 0%), but not related to the extent of tumor resection. The local control rate was 86% and the majority of the local recurrences occurred at the upper resection margin. There was no significant difference in the local recurrence rate between those patients who had pharyngolaryngoesophagectomy and those who had pharyngolaryngectomy. However, the resection-associated complications (bleeding, cardiac arrhythmia, pulmonary complications) were more frequent when total esophagectomy was performed. Reconstruction-associated complications such as wound infection and anastomotic leakage occurred less often after gastric pull-up reconstruction as compared with the use of myocutaneous flap, but was associated with more serious outcome after pharyngo-gastric anastomosis. Thirty-seven patients (34%) had neck node recurrences and these were significantly related to the preoperative nodal staging (N0, 20%; N1, 37%; N2, 48%; and N3, 83%). Additional primary cancers occurred in 17% of the patients and was a significant cause of death in those patients who survived more than 2 years.

Resistance of Pseudomonas pseudomallei growing as a biofilm on silastic discs to ceftazidime and co-trimoxazole

We have examined the resistance of Pseudomonas pseudomallei biofilm cells to ceftazidime and cotrimoxazole. A large number of these biofilm cells remained viable at 12 and at 24 h, except in the biofilm treated with 200 times the MIC of ceftazidime. The inherent resistance of P. pseudomallei biofilms to conventional antibiotics may explain the lack of success in the treatment of the chronic manifestations of this bacterial infection.

Pneumogastrogram in the diagnosis of perforated peptic ulcer

Early diagnosis and surgical intervention is important in the management of peptic ulcer perforation. This study looks at the value of a pneumogastrogram in the diagnosis of patients suspected of having a perforated peptic ulcer. One hundred and twenty-nine patients were studied. Pneumogastrogram increased the diagnostic yield of pneumoperitoneum from 66% following plain erect X-ray examination to 91%. The procedure was free of complications.

Regional chemotherapy for recurrent squamous head and neck cancers through a saphenous vein interposition graft

Regional chemotherapy for head and neck cancers is effective, but the intra-arterial catheter is not without problems. We interposed a segment of saphenous vein within the carotid system to administer chemotherapeutic agents percutaneously via the arterialized venous segment. From 1983 to 1990, saphenous vein interposition graft was performed after radiotherapy in 24 patients with persistent or recurrent squamous head and neck cancers, which were also considered unresectable. There was no operative mortality. Two patients developed thrombosed vein graft; another two had wound infection; and one patient had a neck hematoma. Cisplatin was administered percutaneously every week via the saphenous vein graft. The response rate was 64% (complete response, 23%; partial response, 41%), and the 5-year actuarial survival rate was 31%. The 1-year survival rates for patients with complete, partial, and no response were 80%, 33%, and 13%, respectively. Saphenous vein interposition graft is a safe and convenient way of delivering intra-arterial chemotherapy, and it provides significant palliation for patients with recurrent nonresectable squamous head and neck cancers after radiotherapy.

Therapeutic efficacy of fleroxacin for eliminating catheter-associated urinary tract infection in a rabbit model

The efficacy of fleroxacin as therapy for experimentally induced catheter-associated urinary tract infection (CAUTI) was examined. A rabbit model of CAUTI using a closed urinary catheter drainage system and the mutant strain of Escherichia coli (WE 6933) were used to examine three dosage regimens (30 mg/kg q8h i.v.; 20 mg/kg q8h i.v.; and 10 mg/kg q8h++i.v.) of fleroxacin administered intravenously for 4 days. Quantitative bacterial counts, urinary concentrations of fleroxacin and desmethylferoxacin, histopathologic changes, and electron microscopic evaluation of catheter-associated biofilm and mucosal biofilm were performed. The results indicated that the bacterial biofilm on the urinary catheter could be eliminated by fleroxacin at 30 mg/kg q8h i.v. and 20 mg/kg q8h i.v. Fleroxacin concentrations in urine exceeded the levels necessary to destroy E. coli. Viable bacteria were eliminated with the third regimen (10 mg/kg q8h i.v.), but electron microscopy demonstrated remnants of bacterial biofilm. Histopathologic changes were significantly reduced in all fleroxacin-treated rabbits, and scanning electron microscopy showed deterioration of the bacterial biofilm on the surface of the Foley catheter in treated animals. These data suggest that fleroxacin may be useful for treating catheter-related infections because these therapeutic dosages limited ascending infections of the urethra and bladder, eliminated catheter-associated biofilms, and killed planktonic bacteria in urine.

Obturator hernia: a continuing diagnostic challenge

BACKGROUND

The rare obturator hernia has a high incidence of potentially lethal complications. This report reviews this condition and stresses the dangers of unrecognized obturator hernia.

METHODS

Thirteen patients with 14 obturator hernias were seen during a 5-year period. All the patients were emaciated and elderly, and 12 were women. They all had clinical features of small bowel obstruction. The classic Howship-Romberg sign was present in only three patients. The diagnosis was made before surgery in five patients.

RESULTS

All hernial sacs contained small bowel. Ileum were present in 11 instances. Richter-type hernia was present in 10 cases. Bowel resection for gangrenous loop was required in seven instances. Apart from associated poor medical conditions, delay in presentation and operation also contributed to the high morbidity and mortality rates. Five patients (38.5%) had postoperative complications, and two patients (15.4%) died of chest infections.

CONCLUSIONS

The need for awareness of the condition is stressed and the diagnosis of obturator hernia should be strongly suspected in a thin, elderly woman who has small bowel obstruction and no previous abdominal surgery.

Bacterial biofilm, brown pigment stone and blockage of biliary stents

Bacterial pathogens gain access into the biliary system by descending via the portal venous circulation or ascending through the sphincter of Oddi in duodenal-biliary reflux. Bacteria thrive as glycocalyx-enclosed microcolonies, coalescing to form an adherent biofilm. The establishment of biofilm is a key event in the formation of biliary sludge and pigment gallstones, and the blockage of biliary stents. The biofilm mode of growth is very effective because it provides bacteria with a measure of protection from antibacterial agents and phagocytic leucocytes. Calcification of the matrix confers further protection for the micro-organisms living inside the biofilm. To date, attempts to prevent blockage of biliary stent have employed physical methods by using large self-expandable stents and stents without side hole. Incorporation of antibiotics within stents has not been successful presumably because bacteria once living in their biofilm are quite resistant to antimicrobial agents. Even the most toxic bile salts have no effect on the biofilm bacteria. Yet, hydrophobic bile salts reduce bacterial adhesion on biomaterial, suggesting that incorporation of such bile salts might prevent the formation of bacterial biofilm.

Pathological basis of surgery in the management of postradiotherapy cervical metastasis in nasopharyngeal carcinoma

Radical neck dissection was performed on 43 patients with nasopharyngeal carcinoma in whom persistent or recurrent cervical metastasis developed after radiotherapy. The pathologic nature of the tumor in the cervical lymph nodes was studied with step serial sectioning of the entire radical neck dissection specimen at 3-mm intervals. In 70% of patients, more tumor-harboring lymph nodes were detected in the specimen when compared with clinical examination. The extensive behavior of the tumor in the cervical metastases was reflected by the presence of extracapsular spread in 70% of the lymph nodes and the existence of isolated clusters of tumor cells in 35% of the specimens studied. Tumor tissue lying in close proximity to the spinal accessory nerve was demonstrated in 27.5% of the specimens, and 72% of the tumor-bearing lymph nodes were located in the posterior triangle. Radical neck dissection is recommended as the salvage procedure for these patients.

Occult lymph node metastasis in small oral tongue cancers

The need to treat the neck in patients with a small primary cancer in the tongue remains controversial. Twenty-eight patients with stage I or II oral tongue squamous carcinomas were retrospectively reviewed. They had not received previous treatment. The tongue primary was excised via the transoral route and the neck was observed closely during follow-up. Thirteen patients developed ipsilateral nodal metastases during follow-up, three of whom also had simultaneous recurrence at the primary site. An additional patient had recurrence at the primary site alone. The incidence of occult neck metastasis was 42% (10 of 24). No tumor-related death occurred in the group without nodal metastasis. The salvage rate after appearance of nodal metastasis was 30%. In oral tongue cancers, elective neck treatment should be considered regardless of a small primary and negative neck examination because of the high incidence of occult nodal metastasis and the poor outcome after salvage treatment.

Prevention and control of bacterial infections associated with medical devices

Bacteria that grow in association with medical devices always form slime enclosed biofilms, within which they are protected, to a large extent, from the bactericidal activity of chemical biocides and antibiotics. Mature biofilms (> 7 days) are demonstrably resistant to 500-5,000 times the concentrations of these agents than are necessary to kill free floating (planktonic) cells of the same organism. The authors have discovered that this well established inherent resistance of biofilm bacteria to antibacterial agents can be completely obviated if these agents are applied to these adherent populations within an electric field. The killing of biofilm bacteria by antibiotics can be dramatically enhanced by relatively weak electric fields (1.5 V/cm and 15 microA/cm2) that, in themselves, have no deleterious effects on these slime protected populations adherent to plastic or metal surfaces. This bioelectric technology can readily be used to enhance the preimplantation sterilization of medical devices by biocides. The authors suggest that it may also be used to control biofilm formation and consequent infection by electrically enhanced perioperative antibiotic prophylaxis and by electrically enhanced penetration of antibiotics to kill the biofilm bacteria that form the inherently resistant nidus of chronic device related infections.

Magnetic resonance imaging using a clinical whole body system: an introduction to a useful technique in small animal experiments

A clinical whole body magnetic resonance imaging (MRI) system with high resolution coils was used to obtain non-invasive images of the living rat. The results demonstrate the feasibility of the set-up and the advantages of this new imaging technique: detailed information, no extra costs, longitudinal studies without killing animals and simple anaesthesia. It is concluded that in small animal experimentation, this use of high resolution coils in whole body magnetic resonance systems may be particularly helpful in establishing effects of experimental procedures. Whenever non-invasive visualization is required, especially in longitudinal animal studies, e.g. biomaterial research or tumour investigation, this use of MRI will offer challenging possibilities.

Evaluation of strategies for central venous catheter replacement

OBJECTIVES

To assess the consequences of leaving a bacterially colonized central venous catheter in place and to compare the effects of three catheter replacement strategies for catheter repair control in an animal model.

DESIGN

Prospective study.

SETTING

Laboratory and animal facility of a large university.

SUBJECTS

Eighteen healthy, female, adult sheep.

INTERVENTIONS

Radiopaque-siliconized elastomer central venous catheters were inserted into the jugular veins and colonized with either Escherichia coli or Staphylococcus epidermidis. After 7 days of infection, the catheters were either: a) exchanged using a guidewire; b) removed and replaced with a new catheter in a new jugular vein site after a 48-hr interval; or c) exchanged using a guidewire and antibiotics (tobramycin, cephaloridine) injected into the catheter. Animals were euthanized 7 days after insertion of the new catheter. Quantitative microbiology was performed on blood samples collected daily from the catheters and a peripheral vein, as well as from catheters and tissue recovered from the sheep at the time of autopsy.

MEASUREMENTS AND MAIN RESULT

When catheters were changed using a guidewire, they became colonized by bacteria within 48 hrs, and the sheep had embolic pneumonia and vegetative endocarditis at autopsy. Similar consequences were observed when antibiotics were administered into the catheter lumen. If colonized catheters were removed and a new catheter was inserted after a 48-hr interval, recolonization, pneumonia, and endocarditis were not observed.

CONCLUSIONS

Replacement of a biofilm-colonized central venous catheter over a guidewire is associated with rapid colonization of the replacement catheter and production of detached, slime-enclosed, antibiotic-resistant aggregates that colonize other catheters or initiate endocarditis or pneumonia by dissemination in the bloodstream.

Mechanism of persistent infection associated with peritoneal implants

The ability of rabbits to clear an intraperitoneal injection of Pseudomonas aeruginosa in the presence or absence of a surgically implanted peritoneal device was investigated. Sham-operated rabbits without an implant eliminated a P. aeruginosa challenge of 5 x 10(6) cfu/ml; lavage fluid and peritoneal tissues became culture-negative within 96 h. However, peritonitis developed in rabbits that were given the same number of bacteria in the presence of an implant; high bacterial counts were recovered from the lavage fluid and the device itself. Scanning and transmission electronmicroscopy revealed bacterial biofilms on the surface of the device. Insertion of pre-colonised devices demonstrated a rapid multiplication of sessile organisms within the resulting bacterial biofilm. Counts reached a plateau of about 1 x 10(7) cfu/cm2 of Silastic by day 16 and fluctuated around this level until the end of the study. Pre-immunisation with formalin-killed whole cells of P. aeruginosa did not reduce this bacterial growth despite high levels of specific IgG. The results confirm the failure of peritoneal defences to clear an infection in the presence of an implant following either challenge with planktonic bacteria or insertion of a pre-colonised device, and demonstrate the rapid development of bacterial biofilms on the surface of the implant which appear to protect the bacteria from host defences, even when primed by pre-immunisation.

Ascending infection of the biliary tract after surgical sphincterotomy and biliary stenting

It has been widely accepted that there is an ascending route of bacterial infection of the biliary tract but there is a lack of direct evidence. This hypothesis was tested in an animal experiment using the cat as an animal model. The implantation of biliary stents and surgical sphincterotomy were performed in these animals, with sham controls. Stents bypassing the sphincter of Oddi with the tip in the duodenal micro-organisms and the biliary tract was heavily contaminated. Blockage of these stents resulted in biliary obstruction. Stents implanted within the common bile duct, proximal to the sphincter were largely unaffected by biofilm formation. After surgical sphincterotomy the biliary tract was also contaminated but, in the absence of obstruction, the animals did not develop any symptoms. It was concluded that ascending infection by duodenal biliary reflux, via the sphincter of Oddi, is an important route of infection in the biliary system.

Biofilms on indwelling vascular catheters

BACKGROUND AND METHODS

Some bacteria have a natural tendency to adhere to available surfaces and to form biofilms. Biofilms have been demonstrated on right heart flow-directed catheters, endocardial pacemaker leads, urinary catheters, and other medical devices. In this study, we examined arterial and central venous catheters that had been in place in ICU patients between 1 and 14 days for the presence of bacterial biofilms by scanning electron microscopy, transmission electron microscopy, and a special scraping/sonication bacterial recovery technique. The data taken from these processes were compared with skin entry site swabs and blood cultures and correlated with patient data on infection, bacterial colonization, and antibiotic use.

RESULTS

Extensive biofilm formation was demonstrated by scanning electron microscopy on all 42 arterial and 26 central venous catheters. Bacteria were seen within the biofilms on 69% (29/42) of the arterial and 88% (23/26) of the central venous catheters. These two direct methods for the detection of biofilm bacteria on the catheter surfaces demonstrated the presence of adherent organisms on 81% of devices examined. Some catheters that had been in place for only 1 day were colonized by bacterial biofilms. Biofilm scraped from catheter surfaces and dispersed by mixing and sonication yielded cultures (32% of catheters) of predominantly skin bacteria. In a few instances, the recovery of bacteria from biofilms on vascular catheters coincided with positive cultures from skin entry site swabs and/or from the blood of the patient, but there was no significant correlation between bacterial recovery from the catheter surface, entry site, and/or patients' blood.

CONCLUSIONS

Direct microscopic examination of 68 vascular catheters that had been in place 1 to 14 days showed that most (81%) were colonized by bacteria growing in slime-enclosed biofilms. In many cases, this colonization of catheter surfaces could be confirmed by special biofilm culture recovery methods. Although the clinical importance of bacterial biofilms on catheter surfaces is speculative, their presence and potential to serve as a nidus for infection and bacteremia in critically ill immunocompromised hosts are cause for concern.

Mirizzi syndrome with cholecystocholedochal fistula: preoperative diagnosis and management

Gallstone obstruction of the cystic duct with resulting repeated attacks of inflammation and pressure necrosis leads to the formation of cholecystocholedochal fistulas (Mirizzi syndrome type II). Obstructive jaundice and cholangitis are the common presentations of the condition. These fistulas are often not recognized before operation and constitute a high risk of damage to the common duct during a formal cholecystectomy. A high index of suspicion is required to diagnose the condition. We report five patients with cholecystocholedochal fistulas diagnosed by endoscopic retrograde cholangiography that delineated the fistula and the obstructing stone. The plan of management was formulated before surgery, and persistent attempt to dissect the Calot's triangle was avoided. In three patients the common duct defect was closed with the use of a gallbladder flap. Hepaticojejunostomy was required for the two difficult cases with large common duct defects and inflamed tissue.

Treatment of neck nodes in oral cancer

In a review of 98 patients who were operated upon for squamous oral cancer, a high proportion of them (48%) developed recurrence after a minimum follow-up of 2 years. Nodal status significantly affected the nodal recurrence rate and survival. For N0, N1, N3 tumours, the 2-year nodal recurrence-free rates were 79, 83, 18%, and the 2-year survival rates were 58, 59 and 10%. For small tumours with N0 neck, the group with elective neck dissection and the observed group did not have statistically different nodal recurrence-free rate and overall survival. The 2-year nodal recurrence-free rate was 92% versus 77% (P value > 0.3) and the 2-year survival rate was 56% versus 72% (P value > 0.6). In patients with N1 neck, radical neck dissection was reasonably effective in controlling neck metastasis. Radical neck dissection in an attempt to treat fixed neck nodes (N3) was not successful in controlling the neck disease.

Radical neck dissection in nasopharyngeal carcinoma

We report a series of 37 patients who had radical neck dissection for residual or recurrent lymph node metastasis from nasopharyngeal carcinoma after radiotherapy. The operation was performed despite high doses of pre-operative radiotherapy. There was no operative mortality and the morbidity was 13% (2 prolonged chylous drainage, 3 sloughing of neck flap). The risk of sloughing of neck flap was significantly related to previous lymph node biopsy, which should be avoided if at all possible. In 35% of patients, the lymph node was densely adherent to neighbouring structures. In the 28 patients who had single lymph node clinically, 29% had multiple neck node involvement noted during operation; another 14% were documented only on histological examination. Radical neck dissection rather than excision alone is justified for the clinically solitary lymph node.

Guidewire catheter change in central venous catheter biofilm formation in a burn population

This study was designed to assess the risk of colonization and biofilm formation of central venous catheters left in situ for seven days vs those changed over a guidewire at three days and removed at seven days. Colonization was determined using scanning and transmission electron microscopy and compared to a special scraping/sonication culture method. Thirty-one catheters were examined, and no difference was found between catheters left in situ (9 of 16 colonized) and those changed over a guidewire (11 of 15 colonized). Colonization rates rose significantly from 4 of 15 catheters at the time of guidewire change to 11 of 15 at 7 days (p less than 0.001). Of the catheters defined as colonized by SEM, the special culture technique showed bacterial growth in only 35 percent, making a negative culture result of dubious value in ruling out catheter colonization. No beneficial effect of guidewire changes in reducing colonization could be demonstrated.

Bacteriologically stressed animal model of new closed catheter drainage system with microbicidal outlet tube

We have used a catheterized rabbit model to test a newly developed catheter drainage system that incorporates a microbicidal outlet tube. In these tests, this new system was compared with a currently marketed closed drainage system, with daily challenge at the outlet tube using an auxotrophically marked uropathogenic strain of Escherichia coli. In the control series (silicone catheter connected to a standard drainage bag via a tamper-evidence seal) the challenge organism developed upstream biofilm colonization of the luminal surfaces of the catheter and drainage system that was complete in 4.6 +/- 2.1 days in 11 animals, while in 1 animal a rapid overgrowth of the system with Streptococcus faecalis developed. The presence of organisms other than the marked E. coli strain on the luminal surfaces of these control catheters showed that down stream colonization was also operative. In the test catheter drainage series, the microbicidal outlet tube insert precluded upstream colonization by the challenge organism in 12 of 16 catheters and significantly delayed (7.2 +/- 1.0 days) this colonization in the remaining 4 animals. When upstream colonization by exogenous bacteria was precluded by this effective device, downstream colonization of the drainage system by mixed populations of bacteria that probably migrated into the bladder via the extraluminal urethral route developed in some animals (6 of 16).

Bacterial invasion of the biliary system by way of the portal-venous system

It has been suggested that bacteria in the intestine gain access into the biliary tract by entering the portal-venous blood. We have tested the hypothesis of hematogenous infection of the biliary system in cats. The animals were treated in three different groups: group A (no biliary obstruction), group B (acute biliary obstruction) and group C (chronic biliary obstruction). A mutant strain of Escherichia coli was infused into the splenic vein of cats at three different dosages (10(7), 10(5) and 10(3) with sham controls. In the unobstructed biliary system, the mutant E. coli was isolated from the bile 30 min and 90 min after the infusion of 10(7) and 10(5) E. coli, respectively. No bacteria were found in the bile with the infusion of 10(3) E. coli and in the control animals. Bile flow was significantly reduced with the infusion of bacteria. The biliary excretion of E. coli in group B was similar to that in group A. In group C, the bile output in the first hour was very high but declined rapidly. E. coli was excreted into the bile at all three dosages of infusion after 30 min. Histological sections of the liver showed that the infused bacteria entered the sinusoidal blood and that some were phagocytosed by Kupffer cells. The portal-venous blood was considered an important route of bacterial invasion into the biliary system, and the penetration of bacteria was facilitated in biliary obstruction.

Tracheostomal stenosis after immediate tracheoesophageal puncture

The incidence of tracheostomal stenosis in a group of patients after total laryngectomy with or without pharyngectomy plus immediate tracheoesophageal or tracheogastric puncture was compared with that of a control group without puncture. The stenosis rate of the puncture group was significantly higher than that of the control group (19% vs 6%). The other probable etiologic factors for stomal stricture were similar in both groups. Analysis of the risk factors in the puncture group suggested a higher tendency of stenosis in females (43% vs 16%) and in patients receiving postoperative radiotherapy (29% vs 14%), although the difference failed to reach statistical significance.

New approach to the nasopharynx: the maxillary swing approach

A new approach to expose the nasopharynx and the paranasopharyngeal space is described. The maxilla, severed from its bony connections, is swung laterally to provide exposure of the nasopharynx. Tumors in the nasopharynx and the paranasopharyngeal space can be adequately resected and tubings for afterloading brachytherapy can be positioned accurately during surgery. The blood supply of the maxilla is from the attached cheek flap and masseter muscle. Three illustrative cases are presented. The wounds in all of them healed primarily with minimal morbidity. The only disadvantage is the development of mild trismus, which responded to conservative treatment.

Use of a grooming and foraging substrate to reduce cage stereotypies in macaques

We examined the effects of a synthetic fleece pad on cage stereotypies in individually housed cynomolgus monkeys. Animals which received the fleece alone engaged in grooming which was associated with an increase in time spent resting. Monkeys given fleece pads sprinkled with morsels of food did not groom the fleece, but rather foraged for long periods (up to 27 min/h). Stereotyped behaviours were reduced by up to 73% by use of the fleece pad both alone and with foraging crumbles.

Maxillary swing approach to the orbit

A new surgical approach to the inferior half of the orbit is described and 2 cases are presented. The approach involves releasing the roof and the anterior wall of the maxillary antrum by osteotomies, keeping their blood supply via the attached masseter muscle, and swinging the osteoplastic flap away from the orbit. With the wide exposure gained, the retrobulbar tumor or large orbital floor tumor is dealt with, and the mobilized bone is replaced and wired into position. There is no postoperative disturbance of cosmetic appearance.

Plea for selective operative cholangiography

A prospective study was carried out to evaluate the use of routine operative cholangiography in 382 patients undergoing elective cholecystectomy. Operative cholangiography was performed in 356 patients. In each patient, the presence or absence of clinical and operative indications for common duct exploration was correlated with the result of the operative cholangiography. In 114 patients (32%) there were one or more indications for exploration and only 34 patients showed positive cholangiographic findings and were explored. Ductal stones were found in 25 patients and nine patients had negative explorations. In the remaining 242 patients who had no indication for common duct exploration, normal cholangiogram was obtained in 234 patients and eight had false positive cholangiograms and were explored unnecessarily. No unsuspected common duct stones were detected in the whole series. Based on these results, a plea is made for selective operative cholangiography.

Modified jet ventilation during total laryngectomy: a prospective study using pulse oximetry and a pressure regulator

A method of jet ventilation during total laryngectomy is described. During the construction of the terminal tracheostomy, a small metal tube is used, instead of the traditional tracheostomy tube, to provide intermittent jet ventilation down the distal trachea. A pressure regulator is also employed to choose a driving pressure best suited to the chest and lung compliance of each patient. Excellent surgical access for tracheo-cutaneous anastomosis is achieved. Satisfactory ventilation during the jet period is also confirmed by unaltered PaCO2 and increased PaO2 levels. The use of pulse oximetry as a non-invasive and continuous monitor of arterial oxygenation is a simple alternative to arterial blood sampling.

Whole organ sectioning of mixed parotid tumors

A pathologic study involving 15 standard formal parotidectomy specimens was carried out using the whole organ sectioning technique. Histopathologic characteristics noted included the presence of exposed capsule, breaks of the capsule, capsular incompleteness, tumor ingrowth and thickness, cellularity, and lymphocytic infiltration. Tracings of histopathology slides were used to reconstruct the three-dimensional configuration of each tumor as viewed from different angles. No tumor had a smooth surface. At the extreme, two tumor lumps were connected by just a narrow waist. Separated tumors were not seen. In only one specimen did a lymph node contain an additional tumor in the form of an adenolymphoma. All tumors showed some exposed capsule or "bare area" to a degree affected mainly by the position of the tumor. Capsular damage was occasionally seen and was usually minor. Capsular incompleteness and tumor ingrowth make global capsular dissection unsafe. It is concluded that formal parotidectomy remains the operation of choice for pleomorphic adenoma of the parotid gland, although capsular dissection (otherwise termed enucleation) cannot be entirely avoided during the procedure.

Efficacy of radical neck dissection for the control of cervical metastasis after radiotherapy for nasopharyngeal carcinoma

Fifty-one patients who had persistent or recurrent neck disease from nasopharyngeal carcinoma after radiotherapy underwent radical neck dissection. The follow-up period ranged from 0.5 to 9 years (median: 2 years). Multiple cervical lymph node involvement was present in 51% of the patients (26 of 51). Malignant cells were detected in 88% of the resected specimens (45 of 51). The clinical sign of fixation of lymph node is the only factor that affects the successful control of neck disease (p = 0.04). Extracapsular extension of the nodal disease was present, and 35% of the lymph nodes were adherent to surrounding structures at operation (18 of 51). There was one hospital mortality and the overall morbidity was minimal. The actuarial survival at 5 years was 38%, and the probability of control of neck disease was 66%. Radical neck dissection is effective in controlling post-irradiation cervical metastasis from nasopharyngeal carcinoma.