Study of the effects of tissue reactions on the function of implanted glucose sensors

The relationship between tissue reactions to a subcutaneously implanted glucose sensor and the function of the sensor was evaluated over a period of 4-weeks using tubular, porous polyvinyl alcohol (PVA) sponges implanted subcutaneously in rats. The PVA sponges were used as scaffolds in which the foreign body response could develop. Coil-type glucose sensors were then placed in the center of the PVA sponges and tested on day 3, and weekly thereafter. In the first approach, the sensors were placed in the sponges still implanted in the rats and tested. In vivo glucose sensor sensitivity peaked at day 7 and steadily decreased until day 35. In the second approach, the sensors were placed in the explanted sponges and then tested. This test showed no sensor function after day 7, indicating that functional blood vessels are critical in maintaining any function whatsoever. In both cases the sensors themselves were never implanted to eliminate any potential in vivo degradation of the sensors that could have affected the outcome of this study. Sensors were then tested in absence of sponges and found to be working properly with no change from preimplantation sensitivity. Once sensor testing was concluded, the PVA sponge/tissue samples were prepared for quantitative histological analysis. It was determined that the increase in collagen deposition within the sponge correlated with the decrease in sensor sensitivity. It was also observed that natural angiogenesis (peak at day 14) did not overcome the barrier to glucose diffusion created by the fibrous capsule.

Sponge pieces as retractors in neurosurgical interventions

BACKGROUND

Different retractors including high-technology products were proposed for neurosurgical interventions. The sponge, having characteristics of deformability and resistance to compression, might be an alternative retractor for the neurosurgical era.

METHODS

Sponge obtainable from the ordinary market was broken into pieces and sterilized by ethylene oxide. During intervention, the appropriate sponge pieces were applied inside the dissected sulci for the purpose of retraction.

RESULTS

The sponge pieces were easily applied and supplied optimal retraction during operations. Proximal application to the dissected sylvian fissure enabled the exposure of the inner distal part including the insular surface, whereas application between the frontobasal surface and the orbital roof provided satisfactory exposure of the suprachiasmatic area. The retraction capacity of the sponge was less than that of self-retaining Leyla retractors, but the postoperative appearance of cortical surfaces was fine without any bruising or hyperemia.

CONCLUSION

The sponge material, with its inner mechanical characteristics and ease of application like cotton pads, seems to be an alternative retractor in neurosurgical interventions, and these characteristic may inspire development of new high-technology retractors.

Diagnostic fine-needle aspiration in postoperative wound infections is more accurate at predicting causative organisms than wound swabs

INTRODUCTION

Postoperative wound infections are common. Antibiotics are often prescribed empirically, usually in the absence of any microbiological sensitivity data. This study demonstrates the role of fine-needle aspiration microbiology (FNAM) in determining the causative organisms in these wounds compared to wound swabs taken from the same patients.

PATIENTS AND METHODS

A total of 20 patients with clinical signs of soft tissue infection were tested using wound swabs and fine-needle aspiration.

RESULTS

Six of the wound swabs yielded a single organism but 16 out 20 of the FNAM group yielded a single organism (P = 0.002).

CONCLUSIONS

The FNAM approach allows antibiotic sensitivities to be obtained enabling specific antimicrobial therapy to be implemented early. FNAM also has a higher yield of cultures than wound swabs. Cellulitic areas can be sampled even when use of wound swabs is not possible.

Method for measuring sinus and vein pressure during surgery: technical note

BACKGROUND

Measurement of dural sinus or drainage vein pressure is useful for determining the appropriate treatment for some patients. We report a novel measurement procedure that reduces bleeding from the needle puncture site as well as further tearing of the wall.

METHODS

The vessel is punctured through the patch by gelatin sponge with fibrin sealant and a siliconized elastic needle is introduced. After obtaining the desired measurements, the needle is withdrawn through the fibrin sealant-bearing patch whose presence facilitates sealing of the puncture site. To further decrease the incidence of complications due to incomplete hemostasis, an additional identically prepared path is placed over the site.

RESULTS

We have used this method in several operations and have encountered no complications. Our method also makes it possible to safely approach the drainers of pial arteriovenous malformations.

CONCLUSIONS

Our method is easy and convenient and prevents the leakage of blood from the puncture site and further tearing of the venous wall.

Double-blind randomised controlled trial comparing Merocel with Rapid Rhino nasal packs after routine nasal surgery

INTRODUCTION

Nasal packing after routine nasal surgery is commonly practiced in the UK. The most popular pack appears to be Merocel, however this can be associated with significant pain on its removal.

AIM

To test the efficacy of a relatively new nasal pack--the Rapid Rhino Goodman pack--introduced to our department, which claims to reduce pain and bleeding after nasal surgery.

METHODS

Fourteen patients undergoing routine nasal surgery were recruited into a randomised controlled trial. One nasal cavity was packed with a Merocel pack and the other with a Rapid Rhino Goodman pack. Patients were asked to record pain levels on each side using a visual analogue scale.

RESULTS

We found no difference between packs whilst in-situ, with all patients recording low to moderate pain scores. There were significantly higher pain levels associated with Merocel pack removal than with Rapid Rhino pack removal (average pain scores 5.64 vs 1.64, p < 0.001) and less bleeding overall.

CONCLUSIONS

Rapid Rhino (Goodman pack) is associated with significantly less pain on removal than Merocel pack, causes less bleeding and is not more painful whilst in-situ. We therefore recommend its use in routine nasal surgery.

A novel method for controlling the quantity of mitomycin-C applied during filtering surgery for glaucoma

The use of a sponge impregnated with mitomycin-C is an increasingly common practice in glaucoma surgery. The appropriate antibiotic concentration and exposure time have been considered in the literature, but not the exact amount to be used or the size of the sponge. The purpose of this study was to estimate the quantity of mitomycin-C contained in sponges prepared by different surgeons as compared to that in applicators of the type used in Schirmer's test graduation (5 x 5 mm). Four surgeons each cut and prepared 10 sponges for intraoperative use according to their usual method. The same procedure was performed with 10 Schirmer's test graduations. Each sponge and each graduation was immersed in a solution of mitomycin-C 0.2 mg/ml, and the quantity of antibiotic (microg) in each was calculated as the difference between wet and dry weight. The mean quantity (+/- SEM) of mitomycin-C contained in cut sponges was 9.6 +/- 4.4 microg (range 1.9-17.3), and the differences between surgeons were statistically significant (p<0.0001). The mean quantity of antibiotic in Schirmer's test graduation was 1.7 +/- 0.3 microg (range 1.1-2.5), and the differences between surgeons were not statistically significant (p=0.79). The quantities of mitomycin-C contained in sponges prepared for glaucoma surgery differed for a given surgeon and between surgeons. Thus, variations in the doses applied to the sclera could account for certain complications due to mitomycin-C. The use of a Schirmer's test graduation improves predictability for the quantity of mitomycin-C applied to the sclera.

In vivo chondrogenesis in collagen sponge sandwiched by perichondrium

In order to increase the cartilage synthesis of the perichondrium, we combined auricular perichondrium with a collagen sponge as a template (perichondrium-sandwiched collagen sponge) and implanted the assembly as an autograft into the back of rabbits. Microscopic examination revealed that cartilaginous tissue was produced in the collagen sponge and chondrosynthesis was accelerated in the collagen sponge implants in comparison with that in materials containing perichondrium alone.

Porosity and biological properties of polyethylene glycol-conjugated collagen materials

Collagen-based materials can be designed for use as scaffolds for connective tissue reconstruction. The goal of the present study was to evaluate the behavior of collagen materials as well as cell and tissue reactions after the conjugation of activated polyethylene glycols (PEGs) with collagen. It is known that proteins conjugated with PEGs exhibit a decrease in their biodegradation rate and their immunogenicity. Different concentrations and molecular weights of activated PEGs (PEG-750 and PEG-5000) were conjugated to collagen materials (films or sponges) which were then investigated by collagenase assay, fibroblast cell culture, and subcutaneous implantation. PEG-conjugated collagen sponge degradation by collagenase was delayed in comparison to untreated sponges. In culture, fibroblasts with a normal morphology reached confluency on PEG-conjugated collagen films. In vivo, the porous structure of non-modified sponges collapsed by day 15 with a few observable fibroblasts between the collagen fibers. In PEG-modified collagen sponges, the porous structure remained stable for 30 days. Cell infiltration was particularly enhanced in PEG-750-conjugated collagen sponges. In conclusion, PEGs conjugated onto collagen sponges stabilize the porous structure without deactivating the biological properties of collagen. These porous composite materials could function as a scaffold to organize tissue ingrowth.

Evaluation of a new non-woven theatre swab

A new non-woven theatre swab was compared with traditional gauze in laboratory and clinical studies. Results of both clinical and laboratory-based studies showed the non-woven swab to be as effective as traditional gauze in terms of softness, conformability, ability to pad or pack, resistance to snagging and shredding, and ease of counting when wet. The non-woven swabs were also superior to gauze with regard to their ability to retain fluid. Manufactured from polyester and hemisynthetic viscose, the non-woven swabs can be produced to a uniform standard and are less expensive. It is concluded that the new non-woven material has practical and economic advantages over traditional gauze.

Swabs: the forgotten item of nursing care?

Swabs are items used every day in every operating room where invasive procedures are performed. How often do scrub nurses hand surgeons swabs, and how often is thought given to their shape, size and composition and their suitability for use inside our patients?

Clinical trial of calcium alginate haemostatic swabs

The influence of a new haemostatic material on surgical bleeding was evaluated in 100 patients who were prospectively randomized to either normal surgical gauze or calcium alginate swabs used throughout cholecystectomy (n = 40), simple mastectomy (n = 18) or inguinal hernia repair (n = 42). Overall, median (range) blood loss was 91 (3-329) ml for gauze and was significantly reduced by calcium alginate swabs to 72 (2-181) ml (P less than 0.05). Unexpectedly, operation times were also shortened from 45 (17-95) min for gauze to 35 (13-70) min with calcium alginate swabs (P less than 0.02). This reduction in blood loss and operating time was greatest for mastectomy, was still statistically significant for cholecystectomy, but was unimportant in inguinal hernia repair. Calcium alginate haemostatic swabs may become routine in major surgery, particularly where blood loss leads to the need for transfusion.