Failure mode and effects analysis of the universal anaesthesia machine in two tertiary care hospitals in Sierra Leone

Background

Anaesthesia care in developed countries involves sophisticated technology and experienced providers. However, advanced machines may be inoperable or fail frequently when placed into the austere medical environment of a developing country. Failure mode and effects analysis (FMEA) is a method for engaging local staff in identifying real or potential breakdowns in processes or work systems and to develop strategies to mitigate risks.

Methods

Nurse anaesthetists from the two tertiary care hospitals in Freetown, Sierra Leone, participated in three sessions moderated by a human factors specialist and an anaesthesiologist. Sessions were audio recorded, and group discussion graphically mapped by the session facilitator for analysis and commentary. These sessions sought to identify potential barriers to implementing an anaesthesia machine designed for austere medical environments—the universal anaesthesia machine (UAM)—and also engaging local nurse anaesthetists in identifying potential solutions to these barriers.

Results

Participating Sierra Leonean clinicians identified five main categories of failure modes (resource availability, environmental issues, staff knowledge and attitudes, and workload and staffing issues) and four categories of mitigation strategies (resource management plans, engaging and educating stakeholders, peer support for new machine use, and collectively advocating for needed resources).

Conclusions

We identified factors that may limit the impact of a UAM and devised likely effective strategies for mitigating those risks.

Activating CTL precursors to reveal CTL function without skewing the repertoire by in vitro expansion

Detection of the functional CD8(+) CTL response usually requires in vitro restimulation. The differences between the CD8(+) CTL repertoire in freshly isolated precursor cells and CD8(+) CTL after short-term in vitro expansion have been generally assumed to be minimal, but have never been defined experimentally. Using staining with P18-I10/H-2D(d) tetramers and monoclonal antibodies (mAb) against Vbeta, we show the surprising result that there was significant skewing of the CD8(+) CTL repertoire after just 7 days of stimulation. In contrast, we found that overnight incubation of precursor cells with peptide allows the functional assessment of CD8(+) CTL (which cannot be detected ex vivo from freshly isolated cells) without changing the absolute number of antigen-specific CTL as measured by tetramer staining or the repertoire of TCR analyzed with mAb. This study affords a better understanding of the differences between the ex vivo and in vitro stimulated CTL repertoire, and provides an approach to reveal a more faithful representation of the functional in vivo CTL response without skewing of the repertoire of T cells detected.

Dall-Miles cable and plate fixation for the treatment of peri-prosthetic femoral fractures-analysis of results in 13 cases

We present a retrospective review of 13 patients with periprosthetic femoral fractures treated with the Dall-Miles cable and plate fixation system between 1995 and 1999. Of these, 12 fractures were in relation to hip arthroplasty and one was proximal to the femoral component of a total knee replacement. Mean age at presentation was 77 years (range 66-87) with the male female ratio of 6:7. All patients were followed up until there was evidence of clinical and radiological union. The average follow-up period was 6.5 months (range 2.5-24). We achieved satisfactory results in ten patients with average time to union of 4.4 months. The results were unsatisfactory in three patients who required further revision procedures due to failure of fixation or non-union. Internal fixation of the fracture with the loose femoral component left in-situ led to failure of union in one patient. Varus mal-alignment of the femoral component to the shaft of more than 6 degrees was associated with unsatisfactory outcome in two patients. The Dall-Miles cable and plate system is a useful method of internal fixation for majority of periprosthetic femoral fractures. This method may not be suitable if the femoral component is loose or if it is in varus angulation of more than 6 degrees to the shaft of the femur.

Quantification of functional recovery following rat sciatic nerve transection

Functional recovery following experimental nerve injury has been notoriously difficult to quantify precisely. The current gold standard in the rat sciatic nerve model involves analysis of footprints of the recovering animal, and computation of the sciatic function index (SFI). We performed transection injuries and measured recovery both by walking track analysis and by a newer, simpler, more quantitative test of motor recovery, the extensor postural thrust (EPT). We demonstrate a high correlation between both testing modalities and suggest a role for EPT measurements as an easier, more consistent measure of motor recovery following experimental rat sciatic nerve transection.

Solid-phase capture of proteins, spores, and bacteria

Current methods for the detection of pathogens in food and water samples generally require a preenrichment step that allows selective enrichment of the test organism. The objective of this research was to eliminate an enrichment step to allow detection of bacteria directly in food and water samples in 30 min. A high-flow-rate, fluidized bed to capture and concentrate large (bacteria and spores) and small (protein) molecules was developed. This format, ImmunoFlow, is volume independent and uses large beads (greater than 3 mm in diameter) when capturing bacteria to prevent sample clogging when testing food samples. Detection of bound targets was done using existing enzyme-linked immunosorbent assay (ELISA) protocols. Four antibodies (anti-Escherichia coli O157:H7, -Bacillus globigii, -bovine serum albumin [BSA], and -ovalbumin [OVA]) were covalently coupled to various glass and ceramic beads. Very small amounts of BSA (<1 ng) and OVA (0.2 to 4.0 microg) were detected. Various industrial and environmental samples were used to observe the effect of the sample composition on the capture of anti-B. globigii and anti-E. coli O157:H7 modified beads. The lower limit of detection for both E. coli O157:H7 and B. globigii was 1 spore/cell independent of the sample size. The activity of anti-B. globigii modified beads declined after 3 days. Anti-E. coli O157:H7 modified beads declined in their capture ability after 2 days in various storage buffers. Storage temperature (4 and 25 degrees C) did not influence the stability. The ImmunoFlow technology is capable of capturing bacteria and spores directly from samples, with subsequent detection in an ELISA format in 30 min.

Fetal tissue engineering: diaphragmatic replacement

BACKGROUND/PURPOSE

Prosthetic repair of congenital diaphragmatic hernia has been associated with high complication rates. This study was aimed at applying fetal tissue engineering to diaphragmatic replacement.

METHODS

Fetal lambs underwent harvest of skeletal muscle specimens. Once expanded in vitro, fetal myoblasts were suspended in a collagen hydrogel submitted to controlled radial tension. The construct was then placed in a bioreactor. After birth, all animals underwent creation of 2 diaphragmatic defects. One defect was repaired with the autologous-engineered construct placed in between 2 acellular supporting membranes and the other with an identical construct but without any cells. Each animal was its own control (graft, n = 10). Animals were killed at different time-points postimplantation for histologic examination. Statistical analysis was by analysis of variance (ANOVA).

RESULTS

Fetal myoblasts expanded up to twice as fast as neonatal cells. Hydrogel-based radial tension enhanced construct architecture by eliciting cell organization within the scaffold. No eventration was present in 4 of 5 engineered constructs but in 0 of 5 acellular grafts (P<.05). At harvest, engineered constructs were thick and histologically resembled normal skeletal muscle, whereas acellular grafts were thin, floppy, and showed low cell density with increased fibrosis.

CONCLUSIONS

Unlike acellular grafts, engineered cellular diaphragmatic constructs are anatomically and histologically similar to normal muscle. Fetal tissue engineering may be a viable alternative for diaphragmatic replacement.

The use of distraction osteogenesis to induce new suprabony periodontal attachment in the beagle dog

Using a technique called distraction osteogenesis (DO), orthopedic surgeons are capable of reconstructing 4 to 5 cm of bone and soft tissue without bone grafts or pedicle flap procedures. DO has been used recently to generate maxillofacial bone as an alternative to maxillary and mandibular osteotomies. Using DO methodology, this study attempted to regenerate supraalveolar buccal periodontium on the mandibular second, third, and fourth premolars of beagle dogs. A small but statistically significantly greater amount of new cementum was generated in experimental teeth, with no difference found between experimental and control groups with respect to regenerating alveolar bone. Further studies using modifications of this technique are warranted to explore the potential of DO as an alternative to conventional regenerative approaches.

Isolation and characterization of a protease from Pseudomonas fluorescens RO98

Pseudomonas fluorescens RO98, a raw milk isolate, was inoculated into McKellar's minimal salts medium and incubated at 25 degrees C for 48 h to allow production of protease. A zinc-metalloacid protease was purified from the cell-free concentrate by anion exchange and gel filtration chromatography. The purified protease was active between 15 and 55 degrees C, and pH 4.5 and 9.0, and was stable to pasteurization. The enzyme had pH and temperature optima for activity of 5.0 and 35 degrees C, respectively. It was heat stable with a D55 of 41 min and a D62.5 of 18 h. Molecular weight of the enzyme was estimated to be 52 kDa by SDS PAGE and size exclusion chromatography. Values for kM of 144.28, 18.73, 110.20 and 35.23 micromol were obtained for whole, alpha-, beta- and kappa-casein, with a Vmax of 8.26, 0.09, 0.42 and 0.70 micromol mg-1 min-1, respectively. The enzyme hydrolysed kappa-casein preferentially when incubated with artificial casein micelles.

Soft-tissue augmentation with injectable alginate and syngeneic fibroblasts

Tissue engineering, a field that combines polymer scaffolds with isolated cell populations to create new tissue, may be applied to soft-tissue augmentation-an area in which polymers and cell populations have been injected independently. We have developed an inbred rat model in which the subcutaneous injection of a hydrogel, a form of polymer, under vacuum permits direct comparison of different materials in terms of both histologic behavior and their ability to maintain the specific shape and volume of a construct. Using this model, we compared three forms of calcium alginate, a synthetic hydrogel, over an 8-week period-standard alginate that was gelled following injection into animals (alginate post-gel), standard alginate that was gelled before injection into animals (alginate pre-gel) and alginate-RGD, to which the cell adhesion tripeptide RGD was linked covalently (RGD post-gel). Parallel groups that included cultured syngeneic fibroblasts suspended within each of these three gels were also evaluated (alginate post-gel plus cells, alginate pre-gel plus cells, and RGD post-gel plus cells). The study used 54 inbred Lewis rats (n = 9 for each of the six groups). Construct geometry was optimally maintained in the alginate post-gel group in which 58 percent of the original volume was preserved at 8 weeks and increased to 88 percent at 8 weeks when syngeneic fibroblasts were included within the gel. Volume was not as well preserved in the RGD post-gel group (25 percent of original volume at 8 weeks), but again increased when syngeneic fibroblasts were included (41 percent of original volume at 8 weeks). Maintenance of volume was poorest in the alginate pre-gel group (31 percent of original volume at 8 weeks) and failed to be augmented by the addition of fibroblasts (19 percent of original volume at 8 weeks). Histologically, the gel remained a uniform sheet surrounded by a fibrous capsule in the alginate post-gel groups. In the alginate pre-gel and RGD post-gel groups, there was significant ingrowth of a fibrovascular stroma into the gel with fragmentation of the construct. In constructs in which syngeneic fibroblasts were included, cells were visualized throughout the gel but did not extend processes or appear to contribute to new tissue formation. Material compression testing indicated that the alginate and RGD post-gel constructs became stiffer over a 12-week period, particularly in the cell-containing groups. Our results suggest that calcium alginate could be a suitable agent for soft-tissue augmentation when gelled subcutaneously following injection. The addition of syngeneic fibroblasts enhanced the ability of the gel to maintain the volume of a construct; this seems to be mediated by increased gel stiffness rather than by de novo tissue formation. Our animal model, in combination with material testing data, permits rigorous comparison of different materials used for soft-tissue augmentation.

Silicon micromachining to tissue engineer branched vascular channels for liver fabrication

To date, many approaches to engineering new tissue have emerged and they have all relied on vascularization from the host to provide permanent engraftment and mass transfer of oxygen and nutrients. Although this approach has been useful in many tissues, it has not been as successful in thick, complex tissues, particularly those comprising the large vital organs such as the liver, kidney, and heart. In this study, we report preliminary results using micromachining technologies on silicon and Pyrex surfaces to generate complete vascular systems that may be integrated with engineered tissue before implantation. Using standard photolithography techniques, trench patterns reminiscent of branched architecture of vascular and capillary networks were etched onto silicon and Pyrex surfaces to serve as templates. Hepatocytes and endothelial cells were cultured and subsequently lifted as single-cell monolayers from these two-dimensional molds. Both cell types were viable and proliferative on these surfaces. In addition, hepatocytes maintained albumin production. The lifted monolayers were then folded into compact three-dimensional tissues. Thus, with the use microfabrication technology in tissue engineering, it now seems feasible to consider lifting endothelial cells as branched vascular networks from two-dimensional templates that may ultimately be combined with layers of parenchymal tissue, such as hepatocytes, to form three-dimensional conformations of living vascularized tissue for implantation.

A comparison of assessments of functional recovery in the rat

Assessment of functional recovery following any peripheral nerve manipulation is critical. While quantitative neurobehavioral testing has been developed in the anesthesia literature for the assessment of neural function, the surgical literature relies mainly on walking track analysis for evaluation of motor recovery. The latter method is both cumbersome to perform and difficult to quantify. We compared standard walking track analysis with the quantitative neurobehavioral tests recently developed for anesthetic testing. We found a close correlation between the recovery predicted by walking track analysis and that suggested by neurobehavioral testing. In addition, the neurobehavioral test battery offered information regarding the rate of return of pure motor function, complex integrated function, proprioceptive function, and sensation. The tests are easier to perform and less susceptible to interpretative error. Neurobehavioral testing may be an effective substitute for walking track analysis in the assessment of functional recovery following manipulation of the rat sciatic nerve.

A novel, biodegradable polymer conduit delivers neurotrophins and promotes nerve regeneration

OBJECTIVE/HYPOTHESIS

A wide variety of substances have been shown to promote neuritic extension after nerve injury. An obstacle to achieving the maximal benefit from these substances has been the difficulty in effectively delivering the substances over a protracted time course that promotes maximal, directed growth. In this study the delivery of a growth-promoting substance through a biodegradable conduit, using materials originally designed for drug delivery applications, was hypothesized to promote more robust neural regeneration than through conduits lacking the substance. The objectives of this study were to create a growth factor-loaded biodegradable nerve guidance conduit, and to assess in vivo nerve regeneration through the conduit compared with that through conduits lacking the substance.

MATERIALS/METHODS

Inosine, a purine analogue thought to promote axonal extension following neural injury, was loaded into cylindrical polymer foams composed of a polylactide-co-glycolide copolymer. First, in vitro extravasation of inosine was measured over a several week period using spectrophotometry. Second, the foams were fashioned into single-channel cylindrical nerve guidance conduits via a novel, low-pressure injection molding technique. The conduits were then used to bridge 7-mm defects in the rat sciatic nerve (n = 8). Control conduits lacking inosine were implanted into another set of animals as controls (n = 12).

RESULTS

In vitro spectrophotometric measurements indicated appreciable leaching of inosine from the loaded foams over a period of at least 9 weeks. In the in vivo model, after 10 weeks, a higher percentage cross sectional area composed of neural tissue existed through the inosine-loaded conduits compared with controls (mean 44%, SD 7.5% vs. 36%, SD 8.6%, respectively). A difference was also found in mean fiber diameter between the two groups, with the inosine-loaded tubes showing a statistically significantly larger diameter than controls (P < .05).

CONCLUSIONS

A nerve regeneration conduit was successfully created that delivers growth promoting substances over a protracted time course. In an in vivo model, the presence of inosine, a purine analogue, yielded neural regeneration whose histological features suggest possible superior long-term motor function.

The tourniquet in total knee arthroplasty. A prospective, randomised study

We assessed the influence of the use of a tourniquet in total knee arthroplasty in a prospective, randomised study. After satisfying exclusion criteria, we divided 77 patients into two groups, one to undergo surgery with a tourniquet and one without. Both groups were well matched. The mean change in knee flexion in the group that had surgery without a tourniquet was significantly better at one week (p = 0.03) than in the other group, but movement was similar at six weeks and at four months. There was no significant difference in the surgical time, postoperative pain, need for analgesia, the volume collected in the drains, postoperative swelling, and the incidence of wound complications or of deep-venous thrombosis. We conclude that the use of a tourniquet is safe and that current practice can be continued.

The tourniquet in total knee arthroplasty

We assessed the influence of the use of a tourniquet in total knee arthroplasty in a prospective, randomised study. After satisfying exclusion criteria, we divided 77 patients into two groups, one to undergo surgery with a tourniquet and one without. Both groups were well matched. The mean change in knee flexion in the group that had surgery without a tourniquet was significantly better at one week (p = 0.03) than in the other group, but movement was similar at six weeks and at four months. There was no significant difference in the surgical time, postoperative pain, need for analgesia, the volume collected in the drains, postoperative swelling, and the incidence of wound complications or of deep-venous thrombosis.

We conclude that the use of a tourniquet is safe and that current practice can be continued.

The non-operative management of radial head fractures: a randomized trial of three treatments

Ninety-eight consecutive patients with Mason type 1 and 2 radial head fractures were randomized into three treatment groups to compare early mobilization with immobilization in flexion and extension. Eighty-one patients were reviewed on average 25 months following fracture and assessed for pain, disability and range of movement. Loss of full extension was the most frequent restriction of movement and was found in 17 patients. Two patients had restricted flexion without limited extension. Patients immobilized in a flexion cast had a significantly reduced range of movement compared with patients immobilized in extension (P = 0.02). Nineteen patients had residual pain and again the flexion group fared worse than the extension group (P = 0.06). Results from early mobilization in a sling were not significantly different from the other two groups. Treatment of radial head fractures in flexion casts should be avoided.

Stabilisation of the wrist in rheumatoid disease

Internal splintage was undertaken of fifteen wrists for pain and instability, using an intramedullary Rush nail. The patients were examined at an average of thirty-three months after operation. Spontaneous fusion in a useful position had occurred in all but one. The operation is simple and external immobilisation is unnecessary.

Stabilisation of the Wrist in Rheumatoid Disease

Internal splintage was undertaken of fifteen wrists for pain and instability, using an intramedullary Rush nail. The patients were examined at an average of thirty-three months after operation. Spontaneous fusion in a useful position had occurred in all but one. The operation is simple and external immobilisation is unnecessary.