Groin hernia repair in Scotland

BACKGROUND

The use of mesh for groin hernia repair has dramatically changed the way this common operation is performed. The aim of this study was to survey the methods of groin hernia repair in Scotland and to assess patient satisfaction with the operation.

METHODS

Between 1 April 1998 and 31 March 1999 all patients who underwent groin hernia repair in the National Health Service in Scotland were identified. As well as looking at the type of hernia repair performed and postoperative morbidity, patients were sent a Short Form-36 about 3 months after the operation to assess satisfaction and return to normal activity.

RESULTS

Information was obtained on 5506 (97 per cent) of patients who underwent groin hernia repair during the study period. Eighty-five per cent of patients had an open mesh repair and 4 per cent had a laparoscopic repair. Most operations (85 per cent) were performed using general anaesthesia on an inpatient basis (78 per cent), and 8 per cent were for repair of a recurrent hernia. Potentially serious intraoperative complications were rare (seven patients), although they were significantly (P < 0. 001) more likely to be associated with a laparoscopic approach or repair of a femoral hernia: relative risk compared with open inguinal hernia repair 33 (95 per cent confidence interval (c.i.) 6-197) and 22 (95 per cent c.i. 3-152) respectively. Wound complications were common and 10 per cent of patients required a district nurse to attend the wound. Patients expressed a high degree of satisfaction; 94 per cent would recommend the same operation to someone else if required.

CONCLUSION

An open mesh repair using general anaesthesia has become the repair of choice for a groin hernia in Scotland. Despite a high incidence of wound complications, patients are satisfied with this operation.

Two new mechanisms of macrolide resistance in clinical strains of Streptococcus pneumoniae from Eastern Europe and North America

Resistance to macrolides in pneumococci is generally mediated by methylation of 23S rRNA via erm(B) methylase which can confer a macrolide (M)-, lincosamide (L)-, and streptogramin B (S(B))-resistant (MLS(B)) phenotype or by drug efflux via mef(A) which confers resistance to 14- and 15-membered macrolides only. We studied 20 strains with unusual ML or MS(B) phenotypes which did not harbor erm(B) or mef(A). The strains had been isolated from patients in Eastern Europe and North America from 1992 to 1998. These isolates were found to contain mutations in genes for either 23S rRNA or ribosomal proteins. Three strains from the United States with an ML phenotype, each representing a different clone, were characterized as having an A2059G (Escherichia coli numbering) change in three of the four 23S rRNA alleles. Susceptibility to macrolides and lincosamides decreased as the number of alleles in isogenic strains containing A2059G increased. Sixteen MS(B) strains from Eastern Europe were found to contain a 3-amino-acid substitution ((69)GTG(71) to TPS) in a highly conserved region of the ribosomal protein L4 ((63)KPWRQKGTGRAR(74)). These strains formed several distinct clonal types. The single MS(B) strain from Canada contained a 6-amino-acid L4 insertion ((69)GTGREKGTGRAR), which impacted growth rate and also conferred a 500-fold increase in MIC on the ketolide telithromycin. These macrolide resistance mechanisms from clinical isolates are similar to those recently described for laboratory-derived mutants.

Effects of methylprednisolone and MK-801 on functional recovery after experimental chronic spinal cord injury

STUDY DESIGN

An experimental study was conducted to evaluate the effects of methylprednisolone and MK-801 after the compressive injury of spinal cord in rats.

OBJECTIVES

To investigate the effect of methylprednisolone and non-competitive NMDA antagonist MK-801 in long-term functional outcome after spinal cord injury (SCI).

METHODS

A randomized group A of Sprague-Dawley rats were treated with MK-801 (1.0 mg/kg, n=10; Group A) after a compression injury. A group of methylprednisolone (MP)-treated (30 mg/kg, n=10; Group B) and non-treated animals (n=9; Group C) were included for comparison. The functional motor outcome such as inclined plane (IP), toe spreading reflex (TSR), and modified Tarlov scale (TS) were measured in each animal at regular time points up to 8 weeks post-treatment. Histologically the injury site was scored in four groups and immunohistochemically Wallerian Degeneration (WD), astrocytosis and expression of beta-amyloid protein was identified.

RESULTS

In examining the IP data, no significant difference was recognized between the group means (P-value>0.5). For the TSR, there were no differences in the group responses. For the TS, the differences were not statistically significant. Only group B showed significance in cavitation scores compared to group A (P>0.0094), WD was significantly different than group C (P>0.03), astrocytosis was significantly higher than group A (P>0.001) and modest presence of beta-amyloid protein.

CONCLUSION

Our data indicate that one time bolus administration of MK-801 lacks any significant effect on axonal function in chronically injured rats. Daily bolus administration of MP at 30 mg/kg also did not ensure a better functional outcome. Immunohistochemically we have been able to show significant differences in WD, astrocytosis and small insignificant changes in beta-amyloid protein.

Effectiveness of a clinical pathway for inpatient asthma management

BACKGROUND

Clinical pathways for asthma are tools that have the potential to improve compliance with nationally recognized management guidelines, but their effect on patient outcomes has not been documented.

OBJECTIVES

To determine the effect of an asthma clinical pathway on patients' length of stay, use of nebulized beta-agonist therapy while hospitalized, and use of acute care clinics for 2 weeks after discharge.

DESIGN/METHODS

The study was a randomized, controlled trial. Patients between the ages of 2 and 18 years admitted with an asthma exacerbation and not under the care of an asthma specialist were eligible for the study. Patients were randomized either to a conventional ward (control group) or to a ward using the clinical pathway (intervention group). For 2 weeks after discharge, we collected data to determine whether patients visited a health care provider for worsening asthma.

RESULTS

One hundred ten patients (26%) were enrolled. Control and intervention groups had similar demographic and asthma severity profiles. The intervention group had an average length of stay 13 hours shorter than did the control group. In addition, at every dosing interval, the intervention group received less nebulized beta-agonist therapy. There were no deaths in either group.

CONCLUSION

A clinical pathway for inpatient asthma decreased the length of stay and beta-agonist medication use with no adverse outcomes or increased acute-care encounters through 2 weeks after discharge.

Isolation and characterization of 23 carbofuran-degrading bacteria from soils from distant geographical areas

The aim of this work was to isolate, identify and type carbofuran-degrading bacteria from two geographically distant soils. Restriction Fragment Length Polymorphism (RFLP) patterns of the 16S rRNA gene and partial 16S rRNA sequence analysis were used to classify the 23 isolates obtained. Nine of them showed high similarity to Pseudomonas strains, seven showed similarity to the Flexibacter/Cytophaga/Bacteroides group and the remainder showed similarity to other bacterial genera. Isolates within the same group were sub-typed by comparing partial 16S rRNA sequences and SDS-PAGE analysis of their total protein profiles. Many of the UK isolates showed similarity to the Pseudomonas genera, while most of the Greek isolates showed similarity to the Flexibacter/Cytophaga/Bacteroides group. Only two Chrysobacterium strains isolated from both the UK and Greek soils were identical.

How do patients perceive support from nurses?

Patients found support in the clinical friendship of nurses. The nurses instilled a sense of normality into their activities, creating a supportive atmosphere. Patients expressed a need for reciprocity in their relationship with the nurses. This relationship should be balanced and sustainable.

Temperature-dependent arrest of neutrophil apoptosis. Failure of Bax insertion into mitochondria at 15 degrees C prevents the release of cytochrome c

Apoptosis is essential for the resolution of neutrophilic inflammation. To define the mechanisms triggering the execution phase of apoptosis we developed and utilized a model in which culture of human neutrophils at 15 degrees C for 20 h arrested apoptosis and subsequent warming to 37 degrees C triggered a synchronous burst of apoptosis. Treatment of 15 degrees C cultured neutrophils with the pan-caspase inhibitor zVAD-fmk just before warming to 37 degrees C inhibited the morphological changes associated with apoptosis, but did not prevent the insertion of the proapoptotic protein Bax into mitochondria nor the inhibition of secretion and the externalization of phosphatidylserine, indices of neutrophil apoptosis. In both intact neutrophils and a cell-free extract, cytochrome c released from mitochondria induced proteolytic cleavage of procaspase-3. At 15 degrees C the binding of Bax to mitochondria was uncoupled from Bax insertion into the mitochondrial membrane required for the release of cytochrome c. Apoptosis was also inhibited by low pH during warming to 37 degrees C, suggesting that changes to the conformation of Bax, necessary for membrane insertion, were being inhibited. Bax insertion was only sensitive to zVAD-fmk when added at the start of the 15 degrees C culture period, suggesting that a cytoplasmic substrate of the effector caspases may mediate in the mechanism of Bax insertion into mitochondria.

Distributional impact of higher patient contributions to Australia's Pharmaceutical Benefits Scheme

This paper uses NATSEM's Pharmaceutical Benefits Model to analyse the effects of a hypothetical 25 per cent rise in patient contributions to prescribed medicines under Australia's Pharmaceutical Benefits Scheme (PBS). The model, based on microsimulation techniques, is able to provide a much broader range of outcomes information, at a much greater level of detail, than is possible with traditional methods. Higher patient contributions are analysed in terms of their impact on the government to patient split in PBS costs, as well as the distribution of such costs across age groups, family incomes, family types and 36 prescribed medicine types. Also considered are changes in the shares of family disposable incomes spent on prescribed drugs arising from the higher patient contributions.

Isolation and characterisation of ethoprophos-degrading bacteria

An enrichment culture technique was used to isolate bacteria responsible for the enhanced biodegradation of ethoprophos in a soil from Northern Greece. Restriction fragment length polymorphism patterns of the 16S rRNA gene, partial 16S rRNA sequence analysis, and sodium dodecylsulfate-polyacrylamide gel electrophoresis total protein profile analysis were used to characterise the isolated bacteria. Two of the three ethoprophos-degrading cultures were pure and both isolates were classified as strains of Pseudomonas putida (epI and epII). The third culture comprised three distinct components, a strain identical to P. putida epI and two strains with 16S rRNA sequence similarity to Enterobacter strains. Isolate epI effectively removed a fresh ethoprophos addition from both fumigated and non-fumigated soil when introduced at high inoculum density, but removed it only from fumigated soil at low inoculum density. Isolates epI and epII degraded cadusafos, isazofos, isofenphos and fenamiphos, but only at a slow rate. This high substrate specificity was attributed to minor (cadusafos), or major (isazofos, isofenphos, fenamiphos) structural differences from ethoprophos. Studies with (14)C-labelled ethoprophos indicated that isolates epI and epII degraded the nematicide by removing the S-propyl moiety.

Oral dietary supplements in pre- and postoperative surgical patients: a prospective and randomized clinical trial

It has been suggested that the routine provision of oral dietary supplements (ODS) in postoperative surgical patients is of benefit in terms of morbidity and length of hospital stay. The aim of this study was to evaluate the effects of both pre- and postoperative ODS in patients undergoing an elective laparotomy. Patients requiring elective major gastrointestinal surgery were prospectively randomized into one of four groups: Group I received ODS in addition to normal diet both pre- and postoperatively, Group II were given ODS in the preoperative period only, Group III received ODS only in the postoperative period, and Group IV did not receive any supplements. Assessments of nutritional status, voluntary food intake, weight loss, serum albumin, morbidity and mortality, anxiety and depression, and postoperative activity levels were performed, and comparisons made between the groups. One hundred patients were included in the study. The mean daily energy intake from preoperative ODS was 507 +/- 140 kcal, significantly more than the 252 +/- 195 kcal in the postoperative period (P < 0.001). The postoperative voluntary food intake in patients receiving ODS was not significantly different from that in patients receiving normal diet alone (1090 versus 1268 kcal, 46.2 versus 49.1 g protein, P > 0. 05). All groups demonstrated an overall weight loss, with no significant differences between the groups, and there was no demonstrable effect on clinical outcome. At 6 mo postoperatively there were no differences between the study groups in terms of levels of activity. These results suggest that the routine use of perioperative ODS in well-nourished patients undergoing major gastrointestinal surgery confers no clinical or functional benefit.

Structural displacements in normal swallowing: a videofluoroscopic study

Dynamic videofluoroscopic swallow studies were performed on 60 normal adult volunteers to establish normative data for displacement of upper aerodigestive tract structures during deglutition. Variables evaluated included hyoid bone displacement, larynx-to-hyoid bone approximation, pharyngeal constriction, and the extent of pharyngoesophageal sphincter (PES) opening during liquid swallows of 1, 3, and 20 cc. Results showed direct relationships between bolus size and hyoid displacement, between bolus size and PES opening, and between bolus size and pharyngeal constriction. Only hyoid-to-larynx approximation remained unchanged across bolus sizes. Sex differences were noted for all variables except PES opening. Reliability for most measurement variables was excellent. To our knowledge, normative data for pharyngeal constriction and larynx-to-hyoid approximation have not previously been described.

The cost effectiveness of larval therapy in venous ulcers

The treatment of necrotic ulcers involves considerable nursing time and expense. The current standard treatment involves repeated application of hydrogels. Larval debridement therapy (LDT) has been shown anecdotally to clear ulcers of necrotic slough but has never been compared directly with 'modern' therapies. The aim of this study has been to compare LDT with hydrogel dressings in the treatment of necrotic venous ulcers. 12 patients with sloughy venous ulcers were randomised to receive either LDT or the control therapy--a hydrogel. Effective debridement occurred with a maximum of one larval application in 6/6 patients. 4/6 patients [corrected] in the hydrogel group still required dressings at one month. The median cost of treatment of the larval group was 78.64 Pounds compared with 136.23 Pounds for the control treatment group (p < 0.05). The study confirms both the clinical efficacy and cost effectiveness of larval therapy in the debridement of sloughy venous ulcers.

Factors influencing the ability of Pseudomonas putida strains epI and II to degrade the organophosphate ethoprophos

Two strains of Pseudomonas putida (epI and epII), isolated previously from ethoprophos-treated soil, were able to degrade ethoprophos (10 mg 1(-1)) in a mineral salts medium plus nitrogen (MSMN) in less than 50 h with a concurrent population growth. Addition of glucose or succinate to MSMN did not influence the degrading ability of Ps. putida epI, but increased the lag phase before rapid degradation commenced with Ps. putida epII. The degrading ability of the two isolates was lost when the pesticide provided the sole source of phosphorus. Degradation of ethoprophos was most rapid when bacterial cultures were incubated at 25 and 37 degrees C. Pseudomonas putida epI was capable of completely degrading ethoprophos at a slow rate at 5 degrees C, compared with Ps. putida epII which could not completely degrade ethoprophos at the same time. Pseudomonas putida epI was capable of degrading ethoprophos when only 60 cells ml(-1) were used as initial inoculum. In contrast, Ps. putida epII was able to totally degrade ethoprophos when inoculum densities of 600 cells ml(-1) or higher were used. In general, longer lag phases accompanied the lower inoculum levels. Both isolates rapidly degraded ethoprophos in MSMN at pHs ranging from 5.5 to 7.6, but not at pH 5 or below.

Ethanol-glycine irrigating fluid for transurethral resection of the prostate in practice

OBJECTIVE

To evaluate the usefulness of a tracer of 1% ethanol in 1. 5% glycine in the early detection of irrigation fluid absorption during transurethral resection of the prostate (TURP).

PATIENTS AND METHODS

Patients (120) undergoing TURP were irrigated with 1% ethanol in 1.5% glycine solution and their expired air tested for alcohol every 10 min during the procedure.

RESULTS

In all, 112 patients were assessed; over half of the patients absorbed the irrigation fluid and they had a significantly lower postoperative serum sodium concentration (P < 0.002). Fourteen patients (12.5%) absorbed over 500 mL and two (1.8%) developed clinical features of the TUR syndrome. The experience of the surgeon, the weight of resected chips and the operative duration were not significantly predictive of absorption.

CONCLUSION

A tracer amount of ethanol in the irrigant is reliable for detecting absorption. Irrigating fluid absorption was unpredictable, thus supporting the case for routine monitoring.

Strategies for improving comorbidity measures based on Medicare and Medicaid claims data

Claims-based measures of comorbid illness severity have generally relied on the diagnoses listed for a single hospitalization. Unfortunately, such diagnostic information is often limited because patients have not been hospitalized during periods of interest, because of incomplete coding of diagnoses on claims forms, or because listed diagnoses represent complications of the hospitalization rather than pre-existing comorbid conditions. To address these limitations, we developed and tested four comorbidity index scores for patients with breast cancer, each based on different sources of health services claims from Medicare and Medicaid: hospitalization for breast cancer surgery; outpatient care prior to the hospitalization; other inpatient care prior to the hospitalization; and all sources combined. Varying the number and type of sources of diagnostic information yielded only very small improvements in the prediction of mortality at 1 and 3 years. Surprisingly, even simpler measures of comorbidity (crude number of diagnoses) and of prior health care utilization (total days spent in the hospital) performed at least as well in predicting mortality as did the more complex index scores which assigned points and weights for specific conditions. The greatest improvement in explanatory power was observed when another source of clinical information (cancer stage derived from a population-based cancer registry) was used to supplement claims information. Expanding the source of claims diagnoses and focusing on time periods prior to an index hospitalization are insufficient for substantially improving the explanatory power of claims-based comorbidity indices. Other improvements suggested by our results should include: increasing the completeness and accuracy of claims diagnoses; supplementing diagnoses with health care utilization information in claims data; and supplementing claims data with other sources of clinical information.

Measuring the costs and benefits of heart disease monitoring

OBJECTIVE

To evaluate the costs and benefits of alternative systems of coronary heart disease monitoring in Scotland.

DESIGN

An option appraisal was conducted to evaluate the costs and benefits of implementing a coronary heart disease monitoring system. This involved a review of existing Scottish datasets and relevant reports, specification of options, definition and weighting of benefit criteria by key stakeholders, assessment of options by experts, and costing of options. The options were assessed by 33 stakeholders (grouped as cardiologists, patient representatives, general practitioners, public health physicians, and policy makers), plus 13 topic experts.

SETTING

Scotland (population 5.1 million).

RESULTS

Between group mean benefit weights were: mortality rates and case fatality (10.6), quality of life (9.8), patient function (8.8), hospital activity (7.8), primary care activity (9.25), prescribing (5.72), socioeconomic impact (4.0), risk factors (7.4), prevalence (5.0), incidence (6.0), case registration (6.82), international comparability (4.2), breadth of coverage (8.8), and frequency (5.8). Differences between group weights were significant for prevalence (p = 0.048) and international comparability (p = 0.032). Four monitoring options were identified: a community epidemiology model, based on MONICA (monitoring trends and determinants in cardiovascular disease) study methodology applied to a series of eight representative communities, had the highest benefits, at an average annual discounted cost of approximately pound 360,000; models based on the Australian cardiovascular disease monitoring scheme and on enhanced routine data offered fewer benefits at discounted average annual costs ranging from pound 165,000 to pound 195,000; finally, a coronary heart disease registry modelled on the Scottish Cancer Registry scheme would have had fewer benefits and substantially higher costs than the other options.

CONCLUSIONS

The most beneficial coronary heart disease monitoring system is the community epidemiology model, based on MONICA methodology. Option appraisal potentially offers an explicit and transparent methodology for evidence based policy development.

Timing of events in normal swallowing: a videofluoroscopic study

Dynamic videofluoroscopic swallow studies were performed on 60 normal adult volunteers to establish normative data for clinically useful timing measures. The relation of swallowing gesture timing to the timing of actual bolus transit was of particular interest because it provides insight into the physiology of larger bolus volume accommodation. Parameters evaluated include the timing of bolus pharyngeal transit, soft palate elevation, aryepiglottic fold elevation and supraglottic closure, arrival of the bolus in the vallecula, hyoid bone displacement onset and duration, arrival of the bolus at the pharyngoesophageal sphincter, maximum pharyngeal constriction, and pharyngoesophageal sphincter opening. These parameters represent events required for normal deglutition, can be used to identify abnormalities in dysphagic patients, and provide a basis for comparison of swallowing performance both within and between patients. In addition, our experience has shown them to be reliably obtained. Other investigators have reported some of the measurements. However, to our knowledge, normative data for timing of aryepiglottic fold elevation, soft palate elevation and closure, and maximum pharyngeal constriction have not been described. Other measures included in the present study may provide alternatives when conventional measures cannot be obtained in selected patients. The relevance and clinical utility of new and alternative measures, in particular, are discussed.

It's a knockout: survey of the management of avulsed teeth

Avulsion of a tooth is a not uncommon childhood injury, with up to 16% of dental injuries involving the loss of a tooth. Although this is an apparently 'minor' injury, for a child there may be long-term psychological and treatment problems. Correct advice in the early stages of this injury, and the recognition that prompt treatment may allow a tooth to be successfully reimplanted are vital in the management of these injuries. Often, nursing staff in the accident and emergency or paediatric department may be asked for advice either professionally or informally, and can influence the long-term dental health for these patients. This paper looks at the knowledge of parents and healthcare professionals in the management of these injuries.

Hypertrophic defect unmasked by calcineurin expression in asymptomatic tropomodulin overexpressing transgenic mice

OBJECTIVE

Dilation and hypertrophy often occur concurrently in cardiomyopathy, yet the interaction between these two functionally distinct conditions remains unknown.

METHODS

Combinatorial effects of hypertrophy and dilation were investigated by cross-breeding of two cardiomyopathic transgenic mouse lines which develop either hypertrophy (calcineurin-mediated) or dilation (tropomodulin-mediated).

RESULTS

Altering the intensity of signals driving hypertrophy and dilation in cross-bred litters resulted in novel disease phenotypes different from either parental line. Augmenting the calcineurin-dependent hypertrophic stimulus in tropomodulin overexpressing transgenics elevated heart:body weight ratios, increased ventricular wall thickness, and significantly accelerated mortality. These effects were evident in calcineurin cross-breeding to tropomodulin backgrounds of transgene homozygosity (severe dilation) or heterozygosity (mild dilation to asymptomatic). Molecular analyses indicated that tropomodulin and calcineurin signaling events in the first week after birth were critical for determination of disease outcome, substantiated by demonstration that temporary neonatal inhibition of tropomodulin expression prevents dilation.

CONCLUSIONS

This study shows that postnatal timing of altered signaling in cardiomyopathic transgenic mouse models is a pivotal part of determining outcome. In addition, intensifying hypertrophic stimulation exacerbates dilated cardiomyopathy, supporting the concept of shared molecular signaling between hypertrophy and dilation.

Altered focal adhesion regulation correlates with cardiomyopathy in mice expressing constitutively active rac1

The ras family of small GTP-binding proteins exerts powerful effects upon cell structure and function. One member of this family, rac, induces actin cytoskeletal reorganization in nonmuscle cells and hypertrophic changes in cultured cardiomyocytes. To examine the effect of rac1 activation upon cardiac structure and function, transgenic mice were created that express constitutively activated rac1 specifically in the myocardium. Transgenic rac1 protein was expressed at levels comparable to endogenous rac levels, with activation of the rac1 signaling pathway resulting in two distinct cardiomyopathic phenotypes: a lethal dilated phenotype associated with neonatal activation of the transgene and a transient cardiac hypertrophy seen among juvenile mice that resolved with age. Neither phenotype showed myofibril disarray and hypertrophic hearts were hypercontractilein working heart analyses. The rac1 target p21-activated kinase translocated from a cytosolic to a cytoskeletal distribution, suggesting that rac1 activation was inducing focal adhesion reorganization. Corroborating results showed altered localizations of src in dilated cardiomyopathy and paxillin in both cardiomyopathic phenotypes. This study, the first examination of rac1-mediated cardiac effects in vivo, demonstrates that dilation and hypertrophy can share a common molecular origin and presents evidence that both timing and concurrent signaling from multiple pathways can influence cardiac remodeling.

Domiciliary occupational therapy for patients with stroke discharged from hospital: randomised controlled trial

OBJECTIVE

To establish if a brief programme of domiciliary occupational therapy could improve the recovery of patients with stroke discharged from hospital.

DESIGN

Single blind randomised controlled trial.

SETTING

Two hospital sites within a UK teaching hospital.

SUBJECTS

138 patients with stroke with a definite plan for discharge home from hospital.

INTERVENTION

Six week domiciliary occupational therapy or routine follow up.

MAIN OUTCOME MEASURES

Nottingham extended activities of daily living score and "global outcome" (deterioration according to the Barthel activities of daily living index, or death).

RESULTS

By eight weeks the mean Nottingham extended activities of daily living score in the intervention group was 4.8 points (95% confidence interval -0.5 to 10.0, P=0.08) greater than that of the control group. Overall, 16 (24%) intervention patients had a poor global outcome compared with 30 (42%) control patients (odds ratio 0.43, 0.21 to 0.89, P=0.02). These patterns persisted at six months but were not statistically significant. Patients in the intervention group were more likely to report satisfaction with a range of aspects of services.

CONCLUSION

The functional outcome and satisfaction of patients with stroke can be improved by a brief occupational therapy programme carried out in the patient's home immediately after discharge. Major benefits may not, however, be sustained.

Mathematic modeling of forces associated with shoulder dystocia: a comparison of endogenous and exogenous sources

OBJECTIVE

A mathematic model was developed to estimate the compressive pressure on the fetal neck overlying the roots of the brachial plexus by the symphysis pubis during a shoulder dystocia event. The induced pressure was calculated for both exogenous (clinician applied) and endogenous (maternal and uterine) forces during the second stage of labor.

STUDY DESIGN

Intrauterine pressure and clinician-applied force data were taken from the existing literature. A free-body diagram was generated and equilibrium equations were used to calculate the contact pressure between the base of the fetal neck and the symphysis pubis during a shoulder dystocia event.

RESULTS

Clinician-applied traction to the fetal head (exogenous force) led to an estimated contact pressure of 22.9 kPa between the fetal neck and the symphysis pubis. In contrast, uterine and maternal expulsive efforts (endogenous forces) resulted in contact pressures that ranged from 91.1 to 202.5 kPa. The estimated pressures resulting from endogenous forces are 4 to 9 times greater than the value calculated for clinician-applied forces.

CONCLUSION

Neonatal brachial plexus injury is not a priori explained by iatrogenically induced excessive traction. Spontaneous endogenous forces may contribute substantially to this type of neonatal trauma.