Third and fourth generation ceramic-on-ceramic total hip arthroplasty at a minimum of ten years

BACKGROUND

Ceramic on Ceramic bearings in Total Hip Arthroplasty (THA) afford a low friction coefficient, low wear rates and extreme hardness. Significant complications include hip squeak, ceramic fracture and poor polyethylene performance in revision procedures due to imbedding of abrasive microscopic ceramic fragments. We report on the results of this bearing at a minimum of 10 years.

METHODS

A single-centre retrospective review of 449 THAs was performed. Primary outcome measures included aseptic revision and all-cause revision rates at a minimum of 10 years post operatively. Evaluation of functionality was performed with WOMAC and SF-36 scores which were performed pre-operatively and at intervals of 6 months, one year, 2 years, 5 years and 10 years post operatively.

RESULTS

There was a 6.2% (n = 28) all-cause and 5.3% (n = 24) aseptic revision rate for ceramic on ceramic total hip arthroplasty at minimum of 10 years with a mean time to revision 4.8 years (range 2 months-11.6 years). Notably, there were 2 revisions for ceramic head fracture, one for ceramic liner fracture, 3 for aseptic loosening and 3 revisions for squeaking. Pain of unknown origin was the most common reason for revision. There was an improvement in postoperative WOMAC scores from a mean of 59.8 (range 15-95) pre-operatively to a mean of 15.6 (range 0-78) at 10 years.

CONCLUSION

This study showed good functional outcomes but high revision rates for CoC THA at a minimum of 10 years. Our rates of ceramic fracture were consistent with other studies.

Assessment of previous fracture and anti-osteoporotic medication prescription in hip fracture patients

INTRODUCTION

Hip fracture prevention is an essential component in elderly patient care. History of prior fracture is a significant risk factor for subsequent hip fracture. There are variable rates of treatment for these groups of patients. The aims of this study were to make an assessment of how many hip fracture patients over a 1 year period had a previous fracture and to assess whether or not these patients were on anti-osteoporotic medication.

METHODS

Assessment on whether or not patients had a prior fracture using the national radiology imaging system checking radiology reports for all previous imaging performed. Checking patients bone health status using the hip fracture database for our hospital.

RESULTS

There were 225 hip fractures in 221 patients over a 1-year period. About 42.6% of females and 35.9% of males had a history of previous fracture. Vertebral fractures were the most common type of fracture. We found 7% of patients had a contralateral hip fracture. There were 81% of patients with prior fracture, and 71% of those without prior fracture were on anti-osteoporotic medication.

DISCUSSION

Vertebral fractures were the most common preceding fracture in hip fracture patients. There were many patients with a history of fragility fractures that were not on preventative medication. Overall there were good prescription rates of anti-osteoporotic medication. There were significantly higher rates of prescription amongst females compared with males.

The effect of indirect admission via hospital transfer on hip fracture patients in Ireland

BACKGROUND AND AIMS

Current best practice states that hip fracture patients should undergo surgery within 48 hours to minimise perioperative complications. There are 10 emergency departments (EDs) in Ireland that receive hip fracture patients without a trauma and orthopaedic surgery unit on site. Idle periods and duplicated preoperative investigations can lead to a prolonged time to surgery. The aim of this study was to identify the effect of admission route on the time to surgery, length of stay and pressure ulcer development in patients who sustain a hip fracture in Ireland.

METHODS

A retrospective cohort study was performed, using 2013 and 2014 data from the Irish Hip Fracture Database. Age, gender and ASA grade were identified as confounders and adjusted for accordingly.

RESULTS

Of the 3893 hip fractures identified, indirect admissions via hospital transfer occurred in 8.6% of cases. Surgery was performed within 48 h in 72.0% of indirect admission and 73.7% of direct admission cases (p = 0.502). The length of stay was significantly prolonged for patients admitted via hospital transfer (25.6 compared to 19.6 days, p < 0.001).

CONCLUSION

Delayed discharges post hip fracture have been shown to expose patients to increased perioperative morbidity and mortality rates, as well as reduced rehabilitation potential and less chance of returning home on discharge. This has significant cost implications for the health service and justifies the introduction of hospital bypass protocols for patients with hip fractures.

Serum N-Terminal Type III Procollagen Propeptide: An Indicator of Growth Hormone Excess and Response to Treatment in Feline Hypersomatotropism

Background

N‐terminal type III procollagen propeptide (PIIINP) is a biomarker of soft tissue proliferation. Hypersomatotropism (HS) is associated with soft tissue proliferation.

Hypothesis

Serum PIIINP is increased in cats with HS and decreases with effective treatment, and may be an additional tool in the diagnosis and treatment of feline HS.

Animals

Cats with uncomplicated diabetes mellitus (DM; n = 30) and with HS‐induced DM (HSDM; n = 30). Pre‐ and posttreatment samples were available from 5 cats undergoing radiotherapy (RT) and 16 cats undergoing hypophysectomy (HPX).

Methods

Retrospective and prospective cross‐sectional study. Analytical performance of a serum PIIINP ELISA was assessed and validated for use in cats. PIIINP and insulin‐like growth factor 1 (IGF‐1) radioimmunoassays (RIA) were performed pre‐ and post‐treatment in cats with DM and HSDM. PIIINP and IGF‐1 were compared between cats treated by RT and HPX.

Results

Serum PIIINP concentrations were significantly higher (P < .001) in HSDM cats (median, 19.6 ng/mL; range, 1.7–27.9) compared to DM cats (median, 5.0 ng/mL; range, 2.1–10.4). A cut‐off of 10.5 ng/mL allowed differentiation between DM and HSDM cats with 87% sensitivity and 100% specificity (area under the curve [AUC], 0.91; 95% confidence interval [CI], 0.82‐1). After RT, PIIINP increased significantly (P = .043) with no significant change in IGF‐1 concentrations. After HPX, serum PIIINP (P = .034) and IGF‐1 concentrations (P < .001) decreased significantly.

Conclusion and clinical importance

PIIINP concentrations are increased in cats with untreated HSDM compared to those with DM, demonstrating the effect of excess GH on soft tissue. PIIINP concentrations decreased after HPX in most HSDM cats.

Risk factors for early post-operative neurological deterioration in dogs undergoing a cervical dorsal laminectomy or hemilaminectomy: 100 cases (2002-2014)

Early post-operative neurological deterioration is a well-known complication following dorsal cervical laminectomies and hemilaminectomies in dogs. This study aimed to evaluate potential risk factors for early post-operative neurological deterioration following these surgical procedures. Medical records of 100 dogs that had undergone a cervical dorsal laminectomy or hemilaminectomy between 2002 and 2014 were assessed retrospectively. Assessed variables included signalment, bodyweight, duration of clinical signs, neurological status before surgery, diagnosis, surgical site, type and extent of surgery and duration of procedure. Outcome measures were neurological status immediately following surgery and duration of hospitalisation. Univariate statistical analysis was performed to identify variables to be included in a multivariate model. Diagnoses included osseous associated cervical spondylomyelopathy (OACSM; n = 41), acute intervertebral disk extrusion (IVDE; 31), meningioma (11), spinal arachnoid diverticulum (10) and vertebral arch anomalies (7). Overall 54% (95% CI 45.25-64.75) of dogs were neurologically worse 48 h post-operatively. Multivariate statistical analysis identified four factors significantly related to early post-operative neurological outcome. Diagnoses of OACSM or meningioma were considered the strongest variables to predict early post-operative neurological deterioration, followed by higher (more severely affected) neurological grade before surgery and longer surgery time. This information can aid in the management of expectations of clinical staff and owners with dogs undergoing these surgical procedures.

Expectations of General Practitioners for Patients Undergoing Elective Total Knee Arthroplasty

Most patients undergoing total knee arthroplasty (TKA) in Ireland are referred to orthopaedic services by their general practitioners (GPs). We aimed to evaluate Irish GPs' expectations for their patients' perioperative experience and post-operative return to function. A questionnaire was mailed to 350 GPs in all provinces. This included questions relating to GPs' expectations for their patients and their knowledge and sources of information on TKA. 111 completed questionnaires were returned (response rate 31.7%). Overall expectations for functional and psychological outcomes were high, especially regarding pain relief (108 (97.3%)) expected relief from most or all pre-operative pain), mobility (108 (97.3%)) expected patients to walk medium or long distances) and psychological wellbeing (95 (85.5%) considered this somewhat or very important). Only 22 (20.2%) reported receiving any relevant information or training within the previous year. Overall expectations for functional outcomes were high, however greater communication between surgeons and GPs may improve GP information,

Clinical reasoning in canine spinal disease: what combination of clinical information is useful?

Spinal disease in dogs is commonly encountered in veterinary practice. Numerous diseases may cause similar clinical signs and presenting histories. The study objective was to use statistical models to identify combinations of discrete parameters from the patient signalment, history and neurological examination that could suggest the most likely diagnoses with statistical significance. A retrospective study of 500 dogs referred to the Queen Mother Hospital for Animals before June 2012 for the investigation of spinal disease was performed. Details regarding signalment, history, physical and neurological examinations, neuroanatomical localisation and imaging data were obtained. Univariate analyses of variables (breed, age, weight, onset, deterioration, pain, asymmetry, neuroanatomical localisation) were performed, and variables were retained in a multivariate logistic regression model if P<0.05. Leading diagnoses were intervertebral disc extrusion (IVDE, n=149), intervertebral disc protrusion (n=149), ischaemic myelopathy (IM, n=48) and neoplasms (n=44). Multivariate logistic regression characterised IM and acute non-compressive nucleus pulposus extrusions as the only peracute onset, non-progressive, non-painful and asymmetrical T3-L3 myelopathies. IVDE was most commonly characterised as acute onset, often deteriorating, painful and largely symmetrical T3-L3 myelopathy. This study suggests that most spinal diseases cause distinctive combinations of presenting clinical parameters (signalment, onset, deterioration, pain, asymmetry, neuroanatomical localisation). Taking particular account of these parameters may aid decision making in a clinical setting.

Consultant and trainee attitudes towards supervision of operative procedures in the UK and Ireland

The e-logbook is used to monitor progression through training and to assess training within teaching units. We document consultant and trainee opinions with regards to supervision status, and to inform guidelines for trainees and trainers using the e-logbook. A questionnaire was sent to consultants and trainees in the UK and Ireland. Eight theatre scenarios were described and respondents were asked to state what they felt was the appropriate supervision status for the trainee. Significantly more consultants in the UK use the e-logbook than those based in Ireland (58.5%:14.5%). There were differences in consensus response to the scenarios between consultants and trainees, and between Irish and UK based surgeons. We have documented the opinions of consultants and trainees from across the UK and Ireland with regards to supervision status for trainees under certain theatre situations. This information should support formal guidelines for all users of the logbook.

The conundrum of calcaneal spurs: do they matter?

BACKGROUND

Chronic plantar heel pain is a common and potentially debilitating condition, often caused by plantar fasciitis. Plantar calcaneal spurs were originally considered the cause of plantar fasciitis but are now regarded as an incidental finding by most authors. We aimed to test this hypothesis and to investigate predisposing factors for the development of spurs.

METHODS

We reviewed all lateral ankle X rays taken in our institution over a 6-month period and identified all X rays demonstrating calcaneal spurs. Then, we identified a similar number of age- and sex-matched controls without spurs. We contacted both groups by telephone and compared symptoms of heel pain, plantar fasciitis, associated comorbidities, and foot and ankle outcome scores (FAOSs).

RESULTS

We reviewed the X rays of 1103 consecutive patients and found a spur prevalence of 12.4%, more common in women and older patients. Questioning of the spur group and control group found a higher body mass index in the spur group. Patients with spurs were 4 times more likely to have diabetes mellitus and 10 times more likely to have lower-limb osteoarthritis. Patients with spurs had more foot pain and poorer FAOS than the control group, even when patients with plantar fasciitis were excluded.

CONCLUSION

Our results demonstrate that the presence of a plantar calcaneal spur may be an indicator of foot pain independent of plantar fasciitis. Although spurs may not cause foot pain themselves, they may be an indication of other associated conditions.

CLINICAL RELEVANCE

We have demonstrated the relevance of a radiographic finding once considered irrelevant.

Publication rates of presentations at the Irish Orthopaedic Association annual meeting

BACKGROUND

Presentation of scientific research at national and international meetings is an important forum for the dissemination of knowledge. Subsequent publication of a full-text paper in a peer-reviewed journal is the expected outcome of such presentations. The publication rate from these meetings is highly variable.

AIMS

To determine the publication rate of abstracts presented at the Irish Orthopaedic Association's Annual Conference and to determine which factors are associated with progression to full-text publication.

METHODS

We reviewed the proceedings from the Irish Orthopaedic Association's National Meeting over a 4 year period. We searched the Pubmed database using author names, institution names, and keywords from each abstract's title, to determine how many presented articles progressed to full-text publication.

RESULTS

Sixty-six of 203 were published, 97 % within 5 years of presentation. Laboratory based studies presenting novel or innovative findings were more likely to be published than clinical studies. Clinical studies were more likely to be published if they were prospective and had a longer period of follow-up. Retrospective audits were less likely to be published, even with a large cohort size. Changes in authorship of presented papers were related to a longer delay in time to full-text publication.

CONCLUSIONS

Thorough planning of research studies is essential to ensure a timely progression to full-text publication in a peer-reviewed journal. Most studies will be published within 5 years of initial presentation.

Biomarkers for smoking cessation

One way to enhance therapeutic development is through the identification and development of evaluative tools such as biomarkers. This review focuses on putative diagnostic, pharmacodynamic, and predictive biomarkers for smoking cessation. These types of biomarkers may be used to more accurately diagnose a disease, personalize treatment, identify novel targets for drug discovery, and enhance the efficiency of drug development. Promising biomarkers are presented across a range of approaches including metabolism, genetics, and neuroimaging. A preclinical viewpoint is also offered, as are analytical considerations and a regulatory perspective summarizing a pathway toward biomarker qualification.

The effect of inclement weather on ankle fracture management in an Irish trauma unit

INTRODUCTION

Ireland is unfamiliar with extreme weather conditions. Such conditions occurred in winter 2009-2010 and 2010-2011, with much of the country being affected by snow and ice. We reviewed the effect that these conditions had on the treatment of ankle fractures in our trauma unit.

MATERIALS AND METHODS

The study period was from November until February for four consecutive years from 2008-2009 until 2011-2012. We compared two winters with extreme weather with two winters with regular weather conditions. Information from Met Eireann was compared with demographics from patient records to differentiate ice-related injuries from non-ice-related injuries. Ankle fractures were classified using the Lauge-Hansen classification. We compared waiting times in A&E, waiting times for theatre, delays relating to injury severity, and overall length of stay for both groups.

RESULTS

We identified 44 ice-related injuries and 67 non-ice-related injuries. Ice-related injuries trended towards more severe fracture configurations using the Lauge-Hansen classification. Patients sustaining ankle injuries during inclement weather were significantly younger than patients sustaining injuries during regular weather conditions. There were no other significant differences between the two groups.

DISCUSSION

Ice-related injuries trended towards a greater severity of fracture configuration. We identified no significant increase in the time to treatment or overall length of stay of patients sustaining ankle fractures during these times. Ice-related injuries did not have greater rates of complications. These results are a testament to the trauma staff in this unit who absorbed the increased workload without compromising patient care.

Femoral impaction grafting in revision total hip arthroplasty: a follow-up of 540 hips

Between 1987 and 1999, 540 revision total hip arthroplasties in 487 patients were performed at our institution using the femoral impaction grafting technique with a cemented femoral stem. All patients were prospectively followed up for 2 to 15 years postoperatively with no loss to follow-up. A total of 494 hips remained successfully in situ at an average of 6.7 years. The 10-year survival rate was 98.0% (95% confidence interval, 96.2-99.8) with aseptic loosening as the end point and 84.2% (95% confidence interval, 78.5-89.9) for reoperation for any reason. Indication for surgery and the use of any kind of reinforcement significantly influenced outcome (P < .001). This is the largest known series of revision THA with femoral impaction grafting, and the results support continued use of this technique.

Intramedullary versus extramedullary alignment of the tibial component in the Triathlon knee

Background

Long term survivorship in total knee arthroplasty is significantly dependant on prosthesis alignment. Our aim was determine which alignment guide was more accurate in positioning of the tibial component in total knee arthroplasty. We also aimed to assess whether there was any difference in short term patient outcome.

Method

A comparison of intramedullary versus extramedullary alignment jig was performed. Radiological alignment of tibial components and patient outcomes of 103 Triathlon total knee arthroplasties were analysed.

Results

Use of the intramedullary was found to be significantly more accurate in determining coronal alignment (p = 0.02) while use of the extramedullary jig was found to give more accurate results in sagittal alignment (p = 0.04). There was no significant difference in WOMAC or SF-36 at six months.

Conclusion

Use of an intramedullary jig is preferable for positioning of the tibial component using this knee system.

The threshold force required for femoral impaction grafting in revision hip surgery

BACKGROUND AND PURPOSE

Femoral impaction grafting requires vigorous impaction to obtain adequate stability without risk of fracture, but the force of impaction has not been determined. We determined this threshold force in a preliminary study using animal femurs.

METHODS

Adult sow femurs were used because of their morphological similarity to human femurs in revision hip arthroplasty. 35 sow femurs were impacted with morselized bone chips and an increasing force was applied until the femur fractured. This allowed a threshold force to be established. 5 other femurs were impacted to this force and an Exeter stem was cemented into the neomedullary canal. A 28-mm Exeter head was attached and loaded by direct contact with a hydraulic testing machine. Axial cyclic loading was performed and the position sensor of the hydraulic testing machine measured the prosthetic head subsidence.

RESULTS

29 tests were completed successfully. The threshold force was found to be 4 kN. There was no statistically significant correlation between the load at fracture and the cortex-to-canal ratio or the bone mineral density. Following impaction with a maximum force of 4 kN, the average axial subsidence was 0.28 mm.

INTERPRETATION

We achieved a stable construct without fracture. Further studies using human cadaveric femurs should be done to determine the threshold force required for femoral impaction grafting in revision hip surgery.

Irish National Joint Registry: a concept

Despite the well-documented benefits, some countries have yet to agree on the establishment of a national joint register. A questionnaire study was undertaken to ascertain the opinions of the consultant orthopaedic surgeons and specialist registrars, regarding establishment of an Irish National Joint Register. The aim was to find out the possible reasons why a national joint register has not been established in Ireland. A 69% first response rate was recorded. Ninety-seven percent believe it is time to set up a registry and 81% say it should be made compulsory for unwilling surgeons and hospitals to participate. Despite the overwhelming support, privacy and liability issues were major concerns. Fifty-eight percent agree that access to registry report by general public can expose surgeons and hospitals to medico-legal implications. Legislation may be required to protect the integrity of a national joint replacement registry to ensure that the data are used as intended.

Neurobiology of the nicotine withdrawal syndrome

The aversive aspects of withdrawal from chronic nicotine exposure are thought to be an important motivational factor contributing to the maintenance of the tobacco habit in human smokers. Much emphasis has been placed on delineating the underlying neurobiological mechanisms mediating different components of the nicotine withdrawal syndrome. Recent studies have shown that both central and peripheral populations of nicotinic acetylcholine receptors (nAChRs) are involved in mediating somatic signs of nicotine withdrawal as measured by the rodent nicotine abstinence scale. However, only central populations of nAChRs are involved in mediating affective aspects of nicotine withdrawal, as measured by elevations in brain-stimulation reward thresholds and conditioned place aversion. Nicotine interacts with several neurotransmitter systems, including acetylcholine, dopamine, opioid peptides, serotonin, and glutamate systems. Evidence so far suggests that these neurotransmitters play a role in nicotine dependence and withdrawal processes. The available evidence also suggests that different underlying neurochemical deficits mediate somatic and affective components of nicotine withdrawal. The aim of the present review is to discuss preclinical findings concerning the neuroanatomical and neurochemical substrates involved in these different aspects of nicotine withdrawal.

The dorsal raphé nucleus is a crucial structure mediating nicotine's anxiolytic effects and the development of tolerance and withdrawal responses

RATIONALE

Smokers frequently report that they obtain anxiety-reducing (anxiolytic) effects from smoking, and this may be one factor which contributes to nicotine dependence.

OBJECTIVE

The aim of this study was to investigate the role of the dorsal raphé nucleus (DRN) in mediating the acute anxiolytic effect of nicotine, the development of tolerance to this effect and the anxiogenic response observed on withdrawal from chronic nicotine.

METHODS

The social interaction test of anxiety was used to investigate the effects of a range of doses of (-)-nicotine (2.5-4000 ng) following DRN infusion, and whether co-administration of the specific 5-HT1A receptor antagonist WAY 100635 could antagonise the anxiolytic action of nicotine. We then examined the effects of intra-DRN nicotine (2.5-7 ng) following six daily injections of subcutaneous (s.c.) (-)-nicotine (0.1 mg/kg). Finally, we examined whether s.c. or intra-DRN (-)-nicotine could antagonise the anxiogenic response seen 72 h after the termination of 7 days of nicotine treatment.

RESULTS

Acute nicotine administration into the DRN produced dose-related effects: low doses (2.5-10 ng) induced an anxiolytic effect, intermediate doses were behaviourally silent (100-1000 ng), and an anxiogenic effect was seen following administration of a high dose (4 micrograms). The anxiolytic effect of (-)-nicotine (5 ng) was reversed by co-administration of a behaviourally inactive dose of WAY 100635 (200 ng). Following 6 days of treatment with s.c. 0.1 mg/kg per day (-)-nicotine, tolerance developed to its anxiolytic action in the DRN. Rats withdrawn for 72 h following this chronic treatment showed an anxiogenic response which was reversed by (-)-nicotine injected s.c. (0.1 mg/kg) or into the DRN (5 ng).

CONCLUSIONS

The present findings therefore suggest that the DRN plays an important role in mediating the acute effects of nicotine on anxiety, as measured in the social interaction test, and that the anxiolytic effect is mediated by activation of somatodendritic 5-HT1A autoreceptors. The DRN is also concerned with mediating the development of tolerance to nicotine's anxiolytic effects and because there is an anxiogenic response 72 h after withdrawal from chronic nicotine, this suggests that an oppositional, compensatory mechanism is mediating the tolerance.

Nicotine regulates 5-HT(1A) receptor gene expression in the cerebral cortex and dorsal hippocampus

The 5-HT(1A) receptor has previously been shown to be important in mediating the behavioural effects of nicotine. It is possible that nicotine administration might regulate the levels of 5-HT receptors in limbic and cortical regions, and such regulations may underlie adaptive responses to nicotine in the central nervous system. The effects of acute and chronic systemic (--)-nicotine administration on 5-HT(1A) receptor gene expression were measured by in situ hybridization, in the rat cerebral cortex, dorsal hippocampus and lateral septum. In the cortex, acute nicotine (0.5 mg/kg i.p.) significantly increased the expression of 5-HT(1A) receptor mRNA 2 h and 24 h after injection. Similarly, acute nicotine significantly increased 5-HT(1A) receptor mRNA in the dentate gyrus (DG), CA3 and CA1 regions of the dorsal hippocampus 2 h and 24 h after injection. Acute nicotine was without effect in the lateral septum. Chronic nicotine (0.5 mg/kg i.p; twice daily for 7 days) significantly decreased 5-HT(1A) receptor mRNA in the cortex 2 h after the final injection, but was without effect at 24 h or 72 h. Chronic nicotine caused no changes in 5-HT(1A) mRNA in the lateral septum or dorsal hippocampus. These data demonstrate that nicotine regulates 5-HT(1A) receptor gene expression in the cortex and hippocampus. The rapid regulation of expression of 5-HT(1A) receptor mRNA leads to the hypothesis that nicotine-induced 5-HT release may alter the postsynaptic sensitivity to 5-HT.

Acute nicotine decreases, and chronic nicotine increases the expression of brain-derived neurotrophic factor mRNA in rat hippocampus

Acute nicotine administration (0.5 mg/kg i.p.) significantly decreased BDNF mRNA levels in dentate gyrus, CA3 and CA1 subfields of the rat hippocampus 2 h and 24 h after administration. However, with 7 days nicotine treatment, tolerance developed to the inhibitory effect of nicotine on BDNF mRNA expression and there was a significant increase in BDNF expression 2 h after the final injection in the CA1 region. These data suggests that changes in expression of hippocampal BDNF may be involved in the behavioural effects of nicotine observed after acute and chronic treatment.

Evidence for a complex influence of nicotinic acetylcholine receptors on hippocampal serotonin release

The effects of nicotine on 5-hydroxytryptamine (5-HT) release from serotonergic nerve endings in rat dorsal hippocampal slices were studied. Nicotine (50-500 microM:) caused a concentration-dependent increase in 5-HT release. This effect was antagonised by mecamylamine (0.5 microM:), indicating an action at nicotinic receptors. Nicotine-evoked 5-HT release was not affected by tetrodotoxin (3 microM:), cadmium chloride (0.1 mM:), or the absence of Ca(2+) or Na(+) in the superfusion medium. Unexpectedly, higher concentrations of mecamylamine alone (1-50 microM:) increased 5-HT release. This suggested the presence of inhibitory input to 5-HT neurones and that these inhibitory neurones possess tonically active nicotinic receptors. The effect of mecamylamine (50 microM:) on 5-HT release was reduced by the muscarinic M(1) receptor agonist, McN-A-343 (100 microM:), but pirenzepine (0.005-1 microM:), which blocks M(1) receptors, alone increased 5-HT release. Hippocampal serotonergic neurones are known to possess both excitatory nicotinic receptors and inhibitory M(1) receptors. Although there may be several explanations for our results, one possible explanation is that nicotine stimulates 5-HT release by activating nicotinic heteroreceptors on 5-HT terminals. Mecamylamine (0.5 microM:) antagonises this effect, but higher concentrations increase 5-HT release indirectly by blocking the action of endogenous acetylcholine on nicotinic receptors situated on cholinergic neurones that provide muscarinic inhibitory input to 5-HT neurones.

Hippocampal and septal injections of nicotine and 8-OH-DPAT distinguish among different animal tests of anxiety

1. Different animal tests model different anxiety disorders. Thus, the social interaction test is a model of generalised anxiety disorder, plus-maze Trial 1 models elements of panic disorder and Trial 2 in the elevated plus-maze is a model of specific phobia. 2. Studies of the neuroanatomical and neurochemical pathways controlling behaviour in these different tests provides information on the neurobiological mechanisms modulating anxiety disorders. 3. In the social interaction test, nicotine and 8-OH-DPAT had anxiogenic effects when injected into the dorsal hippocampus or the lateral septum. 4. These ligands were without effect on Trial 1 in the plus-maze when injected into the dorsal hippocampus, but had anxiogenic effects when injected into the lateral septum. 5. On Trial 2 in the elevated plus-maze, nicotine had an anxiolytic effect, but 8-OH-DPAT had an anixiogenic effect when injected into the dorsal hippocampus.

The role of 5-HT1A receptors in mediating the anxiogenic effects of nicotine following lateral septal administration

The purpose of the present study was to determine the role of the 5-HT1A receptors in the lateral septum in the mediation of the anxiogenic effects of nicotine in the social interaction and elevated plus maze tests of anxiety in the rat. Bilateral infusion of (-)-nicotine (4 and 8 microg) and of the 5-HT1A receptor agonist 8-OH-DPAT (200 and 500 ng) into the lateral septum decreased the time spent in social interaction, indicating anxiogenic effects. The anxiogenic effect of 8-OH-DPAT (500 ng) was completely reversed by coadministration of a behaviourally inactive dose of the 5-HT1A receptor antagonist, WAY 100635 (200 ng). The anxiogenic effect of the lower dose of (-)-nicotine (4 microg) was completely reversed by WAY 100635 (200 ng), but the reversal was only partial following administration of 8 microg nicotine. In a second test of anxiety, the elevated plus maze, lateral septal administration of 8-OH-DPAT (500 ng) and nicotine (4 microg) induced anxiogenic effects. In this test, the anxiogenic effect of nicotine (4 microg) was completely reversed by coadministration of WAY 100635 (200 ng). The effects of 8-OH-DPAT demonstrate that stimulation of 5-HT1A receptors in the lateral septum has anxiogenic effects in two animal tests and that the anxiogenic effects of nicotine are mediated at least in part by these 5-HT1A receptors.

The role of the dorsal hippocampal serotonergic and cholinergic systems in the modulation of anxiety

A review of the literature suggests that the dorsal hippocampal serotonergic system, and, in particular, the postsynaptic 5-HT(1A) receptor, mediates an anxiogenic response, whereas endogenous dorsal hippocampal cholinergic tone mediates an anxiolytic response. Accordingly, it has been shown that direct dorsal hippocampal administration of the 5-HT(1A) receptor agonist, 8-OH-DPAT, the nicotinic receptor antagonist, mecamylamine, and the M(1) muscarinic receptor antagonist, pirenzepine, all have anxiogenic effects in rats tested in the social interaction test. It is therefore surprising that nicotine also has an anxiogenic effect in this test following dorsal hippocampal administration. However, the anxiogenic effects of mecamylamine and nicotine in the dorsal hippocampus are blocked by coadministration of the 5-HT(1A) receptor antagonist, WAY 100635, suggesting that both of these compounds act by enhancing hippocampal serotonergic transmission, thereby stimulating postsynaptic 5-HT(1A) receptors. This conclusion is supported by the observation that both nicotine and mecamylamine stimulate basal [3H]-5-HT release from dorsal hippocampal slices. A possible mechanism by which nicotinic receptor ligands modulate hippocampal 5-HT release is discussed, and it is proposed that the dorsal hippocampal serotonergic and cholinergic systems are tightly coupled and function antagonistically in the modulation of anxiety, as measured in the social interaction test. These systems are relatively unimportant in controlling behaviour on trial 1 in the plus-maze. On trial 2 in the elevated plus-maze, a model of specific phobia, the endogenous cholinergic system, nicotine, and the M(1) receptor agonist, McN-A-343, all mediate an anxiolytic effect, whereas stimulation of 5-HT(1A) receptors mediates an anxiogenic effect. It is proposed that the hippocampus may predominantly control the avoidance components of phobic anxiety, with other regions, such as the dorsomedial hypothalamus, controlling the escape components.

Neurobiological mechanisms by which nicotine mediates different types of anxiety

The effects of nicotine administration into the dorsal hippocampus and lateral septum provide further evidence that different neurochemical and neuroanatomical substrates control behaviour in different animal tests. Thus, in the social interaction test (a model of generalised anxiety disorder), bilateral administration of nicotine (1-4 microg) into both regions has anxiogenic effects in test conditions that generate moderate anxiety. The anxiogenic effects are mediated by a nicotine-evoked increase in 5-hydroxytryptamine (5-HT) release and are reversed by co-administration of the 5-HT(1A) receptor antagonist, N-(2-(6-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridyl)-cyclohex -ane carboxamide trichloride (WAY 100,635). On trial 1 in the elevated plus-maze (which models the escape components of panic disorder), nicotine is without effect when administered to the dorsal hippocampus, but has anxiogenic effects after lateral septal administration. On trial 2 in the elevated plus-maze (a model of specific phobia), nicotine (1 microg) has anxiolytic effects when administered to the dorsal hippocampus, but is ineffective (4 and 8 microg) in the lateral septum.

Anxiogenic effects of nicotine in the dorsal hippocampus are mediated by 5-HT1A and not by muscarinic M1 receptors

After direct administration into the dorsal hippocampus nicotine decreased the time spent in social interaction, without changing locomotor activity, indicating an anxiogenic effect. The possibility that post-synaptic M1 muscarinic receptors mediated this effect was examined by determining whether dorsal hippocampal administration of a specific M1 receptor agonist (McN-A-343) had anxiogenic effects, and whether the anxiogenic effect of nicotine could be reversed by co-administration of the M1 receptor antagonist, pirenzepine. McN-A-343 (0.3, 1.6, 3.2, 15.8 nmol) was without effect on social interaction, and pirenzepine (0.7 and 2.4 nmol) injection into the dorsal hippocampus failed to reverse the decrease in social interaction caused by nicotine (6.3 nmol) injection into this area. However, the decrease in social interaction after nicotine (50 nmol) was completely reversed by the specific 5-HT1A receptor antagonist, WAY 100635 (0.4 nmol) after co-administration of both drugs into the dorsal hippocampus. Thus, the anxiogenic effect of nicotine in this brain region seems to be mediated by 5-HT1A, but not M1, receptors. In contrast to the effect of nicotine in naive animals, those retested after a second injection of 50 nmol did not show a significant anxiogenic effect. The theoretical implications of this are discussed and from a practical point of view this suggests caution in the retesting of animals after central injections.

Stimulation of nicotinic receptors in the lateral septal nucleus increases anxiety

The present study investigated the role of nicotinic receptors in the lateral septum in the modulation of anxiety. The effects of direct injections of nicotine into the lateral septum were first investigated in two tests of anxiety, social interaction and elevated plus-maze tests. Intra-septal injection of nicotine (1 and 4 microgram) induced consistent anxiogenic effects in both tests. The reversal of nicotinic effects with mecamylamine was then studied in the social interaction test. Intra-septal injection of mecamylamine at a low dose (15 ng) induced an anxiolytic effect, suggesting the presence of intrinsic cholinergic tone increasing anxiety. At higher doses (30-50 ng), mecamylamine was without effect in the social interaction test, but blocked the anxiogenic effects of nicotine (4 microgram). These findings provide further evidence for the role of the lateral septum in the modulation of anxiety and suggest that cholinergic projections to this brain area facilitate anxiety through nicotinic receptors.

Modulation of behaviour on trials 1 and 2 in the elevated plus-maze test of anxiety after systemic and hippocampal administration of nicotine

RATIONALE

The elevated plus-maze provides a test situation in which distinctive states of anxiety are elicited on trials 1 and 2 and the dorsal hippocampus has previously been shown to mediate the anxiogenic effects of (-)-nicotine in the social interaction test.

OBJECTIVE

To determine the effects of a wide dose range of (-)-nicotine on trial 1 and 2 in the plus-maze after systemic administration and whether the dorsal hippocampus is a site mediating the anxiogenic effect of nicotine.

METHODS

(-)-Nicotine (0.001, 0.005, 0.01, 0.05, 0.1, 0.5 and 1 mg/kg) was injected IP 30 min before testing for 5 min in the plus-maze. Rats receiving dorsal hippocampal infusions received bilateral infusions of 0.5 microl of artificial CSF or (-)-nicotine (0.1, 1, 4 or 8 microg). The needle was left in place for 50 s after injection and testing took place 3 min later. Rats tested on trial 1 were naive to the plus-maze, those tested on trial 2 had received a previous 5-min undrugged exposure to the maze 48 h earlier.

RESULTS

Low doses of (-)-nicotine (0.001, 0.005, 0.01, 0.05 and 0.1 mg/kg, IP) were without effect on either trial, but higher doses (0.5 and 1 mg/kg, IP) had anxiogenic effects on both trials, as shown by decreases in percentage time spent and percentage entries onto the open arms. Infusion of (-)-nicotine (0.1, 1, 4 and 8 microg) bilaterally into the dorsal hippocampus was without effect on trial 1, but 1 microg had an anxiolytic effect on trial 2, shown by an increased percentage time spent on the open arms.

CONCLUSIONS

The results on both trials in the plus-maze after systemic administration of nicotine add to previous reports from the social interaction test that high doses of nicotine have anxiogenic effects. However, the effects of nicotine in the dorsal hippocampus are different in all three anxiety tests (anxiogenic in social interaction, ineffective on trial 1, anxiolytic on trial 2) showing that nicotinic cholinergic control in this brain region may vary depending on the state and/or type of anxiety generated by the test. The brain region(s) underlying the anxiogenic effects of IP nicotine on both trials in the plus-maze remain to be identified.

Bimodal modulation by nicotine of anxiety in the social interaction test: role of the dorsal hippocampus

In conditions generating moderate levels of anxiety in the social interaction test (low light, unfamiliar arena or high light, familiar arena), parenteral administration of nicotine had bimodal actions, low doses (0.01 and 0.1 mg/kg i.p.) had anxiolytic effects and high doses (0.5 and 1.0 mg/kg i.p.) had anxiogenic effects. In test conditions where anxiety was lowest (low light, familiar arena) and highest (high light, unfamiliar arena), nicotine was without effect after intraperitoneal or hippocampal administration. Thus, nicotine plays a modulatory role in which the activity of other neurotransmitters is crucial to its expression. After bilateral administration to the dorsal hippocampus, nicotine (0.1-8.0 microg) had anxiogenic effects in conditions of moderate anxiety; mecamylamine (30 ng) was silent in these conditions, indicating no intrinsic tone. Our results show that the dorsal hippocampus is one area that can mediate anxiogenic effects in the social interaction test, but the brain region mediating anxiolytic effects remains to be identified.

Bimodal modulation by nicotine of anxiety in the social interaction test: role of the dorsal hippocampus

In conditions generating moderate levels of anxiety in the social interaction test (low light, unfamiliar arena or high light, familiar arena), parenteral administration of nicotine had bimodal actions, low doses (0.01 and 0.1 mg/kg i.p.) had anxiolytic effects and high doses (0.5 and 1.0 mg/kg i.p.) had anxiogenic effects. In test conditions where anxiety was lowest (low light, familiar arena) and highest (high light, unfamiliar arena), nicotine was without effect after intraperitoneal or hippocampal administration. Thus, nicotine plays a modulatory role in which the activity of other neurotransmitters is crucial to its expression. After bilateral administration to the dorsal hippocampus, nicotine (0.1-8.0 microg) had anxiogenic effects in conditions of moderate anxiety; mecamylamine (30 ng) was silent in these conditions, indicating no intrinsic tone. Our results show that the dorsal hippocampus is one area that can mediate anxiogenic effects in the social interaction test, but the brain region mediating anxiolytic effects remains to be identified.

Reflex sympathetic dystrophy associated with extraforaminal disc herniation at the L5-S1 level

We report an association between an extraforaminal disc herniation at the L5-S1 level causing an L5 radiculopathy and a reflex sympathetic dystrophy (RSD) in the affected foot. This is only the second reported case of a disc herniation at this level causing an RSD syndrome. We opted to treat both problems through a retroperitoneal approach involving a discectomy and a surgical sympathectomy. There was immediate and lasting relief from all symptoms, which has been maintained at 18 months' follow-up. The possible mechanisms for this condition are discussed as well as the various treatment options.

Caring for the confused geriatric surgical patient

Postoperative confusion in elderly patients is generally a temporary and reversible condition. The causes and contributing factors are numerous. The number of elderly surgical patients will continue to increase as this age group continues to grow. Our role as nurses is to provide the care that will not only focus on early recognition, assessment, and treatment of postoperative confusion, but will also recognize factors that preoperatively place a patient at increased risk and provide care that will prevent or minimize postoperative confusion.

Quantitative ECT: Comparison of Recovery Coefficient and Linearity of Detector Response for Single Photon and Coincidence Detection (F-18, B+ 511 keV)

The response characteristics of two tomographic systems were compared for imaging of positron emitters: a) a SPECT system with a 3/8 in crystal and 511 keV detector shielding, equipped with a specially designed 511 keV collimator, and b) a PET V system using coincidence detection. SPECT transverse plane resolution was 19 mm FWHM and 35 mm FWTM for a radius of rotation of 16 cm. Corresponding resolution for PET was 14 mm FWHM and 28 mm FWTM. Transverse images through a phantom containing cylindrical sources of various cross sections and uniform activity were obtained for each detector. The measured count density or recovery coefficient was found to decrease with source size, the dependence being similar for both systems. The theoretical values for recovery coefficients were calculated by convolution of a Gaussian fit to the SPECT resolution (FWHM, FWTM) values with the uniform cross section of each source. This simple mathematical model confirmed that the recovery coefficient dependence on source size was primarily related to the limited resolution of the detector. Experimental measurements demonstrated that the SPECT resolution for volume sources was sufficient for quantitation, although some limitations exist with respect to source sizes smaller than the detector resolution.

A quantitative model for the measurement of cerebral vascular extraction fraction in vivo following intravenous injection: simulation studies

A mathematical method has been developed by which the cerebral vascular extraction fraction of flow- and diffusion-limited tracers injected intravenously can be measured quantitatively. Successive injections of three tracers are required: a test tracer such as 15O-labeled water; a completely diffusible tracer as a reference tracer and also as a flow tracer; and a tracer for cerebral blood volume (CBV). The arterial tracer concentration curves and total integrated head counts of the test and reference tracers, as well as CBF and CBV values, are required to calculate the extraction fraction. No calibration is required between the head counts and arterial curves. No decay correction of the head and arterial activity is required, because isotopic decay is explicitly included in the equation. The effect of nonextracted test tracer can be corrected. Simulation studies have shown that the calculated extraction fraction values are not sensitive to measurement error in CBF, CBV, partition coefficient, change in measurement time, or time shift effect between the arterial and head data. If there is mixing of two different tissues in the brain, the calculated extraction fraction values are close to the weighted mean values of extraction fraction by relative weight of the tissues. It is concluded that it is possible to apply this method to human studies with a positron emission tomograph scanner and to animal studies with external coincidence detectors.

Measurement of cerebral blood flow in the rat with intravenous injection of [11C]butanol by external coincidence counting: a repeatable and noninvasive method in the brain

No method has been reported for measuring CBF, repeatedly and noninvasively, in the rat brain. A new method is described, which is noninvasive to the brain, skull, or cervical large vessels. Two pairs of coincidence detectors were positioned, one over the rat brain and the other at the loop of a catheter inserted into the femoral artery. The coincidence head curve and arterial curve were recorded after intravenous injection of 1-[11C]butanol in 15 rats. CBF was calculated by one-compartment curve fitting ( CBFo ) from 1-min data and with the recirculation corrected height/area method from 3-min data ( CBFh X 3 min) and 5-min data ( CBFh X 5 min). CBFo agreed well with CBFh X 5 min, although a slight overestimation was observed in CBFh X 3 min. The normal CBFo in the normocapnic group (n = 6, paCO2 36.7 +/- 2.3 mm Hg) was 1.76 +/- 0.49 ml/g min (mean +/- SD). A good correlation was observed between CBFo (y) and PaCO2 (x), and the regression line was y = 0. 0629x -0.715 (r = 0.88, p less than 0.0001). We concluded that this method gives the stable blood flow values noninvasively and with a minimum loss of blood (less than 0.28 ml per measurement). Applications of this method include activation studies, studies on the effect of drugs and treatments, and water and oxygen extraction fraction studies using different tracers in the same rat.

Serial measurements of positron-emitting isotope activity in rat brain

This report describes the construction and performance characteristics of a device capable of making rapid serial measurement of rat brain radioactivity following the administration of a positron emitting isotope. Two bismuth germanate oxide (BGO) scintillation detectors in a coincidence detection circuit are used to achieve the necessary degree of collimation. Data from the device can be used to characterize cerebral biochemical and physiological processes using computer-assisted mathematical models.