Hospital Cost Savings for Sequential COPD Patients Receiving Domiciliary Nasal High Flow Therapy

Purpose

To estimate the 5-year budget impact to Aotearoa New Zealand (NZ) hospitals of domiciliary nasal high flow (NHF) therapy to patients with chronic obstructive pulmonary disease (COPD) who require long term oxygen therapy.

Methods

Hospital admission counts along with length of stay were obtained from hospital records of 200 COPD patients enrolled in a 12-month randomized clinical trial of NHF in Denmark, both over a 12-month baseline and then in the study period while on randomized treatment (control or NHF). NZ costings from similar COPD patients were estimated using data from Middlemore Hospital, Auckland and were applied to the Danish trial. The budget impact of NHF was estimated over the predicted 5-year lifetime of the device when used by patients sequentially.

Results

Fifty-five of 100 patients in the NHF group and 44 of 100 patients in the control group were admitted to hospital with a respiratory diagnosis during the baseline year. They had 108 admissions in the treatment group vs 89 in the control group, with 632 vs 438 days in hospital, and modeled annual costs of $9443 vs $6512 per patient, respectively. During the study period there were 38 vs 44 patients with 67 vs 80 admissions and 302 vs 526 days in hospital, at a modeled annual cost of $6961 vs $9565 per patient respectively. Taking into account capital expenditure and running costs, this resulted in cost savings of $5535 per patient-year (95% CI, -$36 to -$11,034). With 90% usage over the estimated five-year lifetime of the NHF device, amortized capital costs of $594 per year and annual running costs of $662, we estimate a 5-year undiscounted cost saving per NHF device of $18,626 ($16,934 when discounted to net present value at 5% per annum). There would still be annual cost savings over a wide range of assumptions.

Conclusion

Domiciliary NHF therapy for patients with severe COPD has the potential to provide substantial hospital cost savings over the five-year lifetime of the NHF device.

GA4GH: International policies and standards for data sharing across genomic research and healthcare

The Global Alliance for Genomics and Health (GA4GH) aims to accelerate biomedical advances by enabling the responsible sharing of clinical and genomic data through both harmonized data aggregation and federated approaches. The decreasing cost of genomic sequencing (along with other genome-wide molecular assays) and increasing evidence of its clinical utility will soon drive the generation of sequence data from tens of millions of humans, with increasing levels of diversity. In this perspective, we present the GA4GH strategies for addressing the major challenges of this data revolution. We describe the GA4GH organization, which is fueled by the development efforts of eight Work Streams and informed by the needs of 24 Driver Projects and other key stakeholders. We present the GA4GH suite of secure, interoperable technical standards and policy frameworks and review the current status of standards, their relevance to key domains of research and clinical care, and future plans of GA4GH. Broad international participation in building, adopting, and deploying GA4GH standards and frameworks will catalyze an unprecedented effort in data sharing that will be critical to advancing genomic medicine and ensuring that all populations can access its benefits.

Primary prevention of rheumatic fever in the 21st century: evaluation of a national programme

Background

Acute rheumatic fever (ARF) has largely disappeared from high-income countries. However, in New Zealand (NZ) rates remain high in indigenous (Māori) and Pacific populations. In 2011, NZ launched an intensive and unparalleled primary Rheumatic Fever Prevention Programme (RFPP). We evaluated the impact of the school-based sore throat service component of the RFPP.

Methods

The evaluation used national trends of all-age first episode ARF hospitalisation rates before (2009-11) and after (2012-16) implementation of the RFPP. A retrospective cohort study compared first-episode ARF incidence during time-not-exposed (23 093 207 person-days) and time-exposed (68 465 350 person-days) with a school-based sore throat service among children aged 5-12 years from 2012 to 2016.

Results

Following implementation of the RFPP, the national ARF incidence rate declined by 28% from 4.0 per 100 000 [95% confidence interval (CI) 3.5-4.6] at baseline (2009-11) to 2.9 per 100 000 by 2016 (95% CI 2.4-3.4, P <0.01). The school-based sore throat service effectiveness overall was 23% [95% CI -6%-44%; rate ratio (RR) 0.77, 95% CI 0.56-1.06]. Effectiveness was greater in one high-risk region with high coverage (46%, 95% CI 16%-66%; RR 0.54, 95% CI 0.34-0.84).

Conclusions

Population-based primary prevention of ARF through sore throat management may be effective in well-resourced settings like NZ where high-risk populations are geographically concentrated. Where high-risk populations are dispersed, a school-based primary prevention approach appears ineffective and is expensive.

Psychological, behavioral and social effects of disclosing Alzheimer's disease biomarkers to research participants: a systematic review

BACKGROUND

Current Alzheimer's disease (AD) research initiatives focus on cognitively healthy individuals with biomarkers that are associated with the development of AD. It is unclear whether biomarker results should be returned to research participants and what the psychological, behavioral and social effects of disclosure are. This systematic review therefore examines the psychological, behavioral and social effects of disclosing genetic and nongenetic AD-related biomarkers to cognitively healthy research participants.

METHODS

We performed a systematic literature search in eight scientific databases. Three independent reviewers screened the identified records and selected relevant articles. Results extracted from the included articles were aggregated and presented per effect group.

RESULTS

Fourteen studies met the inclusion criteria and were included in the data synthesis. None of the identified studies examined the effects of disclosing nongenetic biomarkers. All studies but one concerned the disclosure of APOE genotype and were conducted in the USA. Study populations consisted largely of cognitively healthy first-degree relatives of AD patients. In this group, disclosure of an increased risk was not associated with anxiety, depression or changes in perceived risk in relation to family history. Disclosure of an increased risk did lead to an increase in specific test-related distress levels, health-related behavior changes and long-term care insurance uptake and possibly diminished memory functioning.

CONCLUSION

In cognitively healthy research participants with a first-degree relative with AD, disclosure of APOE ε4-positivity does not lead to elevated anxiety and depression levels, but does increase test-related distress and results in behavior changes concerning insurance and health. We did not find studies reporting the effects of disclosing nongenetic biomarkers and only one study included people without a family history of AD. Empirical studies on the effects of disclosing nongenetic biomarkers and of disclosure to persons without a family history of AD are urgently needed.

TRIAL REGISTRATION

PROSPERO international prospective register for systematic reviews CRD42016035388 . Registered 19 February 2016.

Hospital admissions for chronic obstructive pulmonary disease in New Zealand

AIM

To determine the number, distribution and cost of hospital admissions for chronic obstructive pulmonary disease (COPD) in New Zealand.

METHODS

National patient-level routine data on admissions with a principal diagnosis of COPD (mostly ICD-10- AN J440 and J441) were obtained for the period July 1st 2008 to June 30th 2013. Admissions with length of stay (LOS) = 90 days were excluded.

RESULTS

There were 61,516 admissions in 5 years. Admission rates and budget impact (in 2012/13 dollar values) were stable but the average length of stay (ALOS) declined from 5.09 to 4.37 days. In FY2012/13 the admission rate was 2.82 per 1000 population, with age standardised rate (ASR) 4.4- and 3.6-fold higher for Maori and Pacific peoples respectively than for European/others. For age = 15 years the ASR was 2.55 per 1000. Admission rates were higher for men than women and increased steeply with age and socioeconomic deprivation (NZDep06). The mean age at discharge was lower for Maori and Pacific peoples than for European/Others (63.4, 67.1 and 72.3 years). The mean 30-day readmission rate was 6.7%. The average LOS increased with age and was shorter for Maori (3.6 days) and Pacific peoples (3.5 days) than for European/Others (4.7 days). Admission rates varied widely across District Health Boards, and were higher in rural than urban regions. The estimated cost of admissions in FY2012/13 was $NZ59.6m.

CONCLUSIONS

Hospital admissions for COPD are costly and are over-represented in high risk groups including rural, elderly, socioeconomically deprived and Maori and Pacific peoples. Effective interventions that are targeted to high risk groups are required to improve equity and reduce the burden of COPD.

Long-term air humidification therapy is cost-effective for patients with moderate or severe chronic obstructive pulmonary disease or bronchiectasis

OBJECTIVE

To establish the cost-effectiveness of long-term humidification therapy (LTHT) added to usual care for patients with moderate or severe chronic obstructive pulmonary disease or bronchiectasis.

METHODS

Resource usage in a 12-month clinical trial of LTHT was estimated from hospital records, patient diaries, and the equipment supplier. Health state utility values were derived from the St. Georges Respiratory Questionnaire (SGRQ) total score. All patients who remained in the trial for 12 months and who had at least 90 days of diary records were included (87 of 108).

RESULTS

Clinical costs were NZ $3973 (95% confidence interval [CI] $1614-$6332) for the control group and NZ $3331 (95% CI $948-$6920) for the intervention group. The mean health benefit per patient was -6.9 SGRQ units (95% CI -13.0 to -7.2; P < 0.05) or +0.0678 quality-adjusted life-years (95% CI 0.001-0.135). With the intervention costing NZ $2059 annually, the mean cost per quality-adjusted life-year was NZ $20,902 (US $18,907) and the bootstrap median was NZ $19,749 (2.5th percentile -$40,923, 97.5th percentile $221,275). At a willingness-to-pay (WTP) threshold of NZ $30,000, the probability of cost-effectiveness was 61%, ranging from 49% to 72% as the cost of LTHT was varied by ±30%. At a WTP of NZ $20,000, the probability was 49% (range 34%-61%).

CONCLUSIONS

LTHT is moderately cost-effective for patients with moderate to severe chronic obstructive pulmonary disease or bronchiectasis at a WTP threshold that is acceptable for public funding of medicines in New Zealand. These findings must be interpreted with caution because of the modest size of the clinical study, necessary lack of blinding in the clinical trial, and uncertainty in estimating health state utility from the SQRQ.

Effect of fixed dose combination treatment on adherence and risk factor control among patients at high risk of cardiovascular disease: randomised controlled trial in primary care

OBJECTIVE

To evaluate whether provision of fixed dose combination treatment improves adherence and risk factor control compared with usual care of patients at high risk of cardiovascular disease in primary care.

DESIGN

Open label randomised control trial: IMPACT (IMProving Adherence using Combination Therapy).

SETTING

54 general practices in the Auckland and Waikato regions of New Zealand, July 2010 to August 2013.

PARTICIPANTS

513 adults (including 257 indigenous Māori) at high risk of cardiovascular disease (established cardiovascular disease or five year risk ≥ 15%) who were recommended for treatment with antiplatelet, statin, and two or more blood pressure lowering drugs. 497 (97%) completed 12 months' follow-up.

INTERVENTIONS

Participants were randomised to continued usual care or to fixed dose combination treatment (with two versions available: aspirin 75 mg, simvastatin 40 mg, and lisinopril 10 mg with either atenolol 50 mg or hydrochlorothiazide 12.5 mg). All drugs in both treatment arms were prescribed by their usual general practitioners and dispensed by local community pharmacists.

MAIN OUTCOME MEASURES

Primary outcomes were self reported adherence to recommended drugs (antiplatelet, statin, and two or more blood pressure lowering agents) and mean change in blood pressure and low density lipoprotein cholesterol at 12 months.

RESULTS

Adherence to all four recommended drugs was greater among fixed dose combination than usual care participants at 12 months (81% v 46%; relative risk 1.75, 95% confidence interval 1.52 to 2.03, P<0.001; number needed to treat 2.9, 95% confidence interval 2.3 to 3.7). Adherence for each drug type at 12 months was high in both groups but especially in the fixed dose combination group: for antiplatelet treatment it was 93% fixed dose combination v 83% usual care (P<0.001), for statin 94% v 89% (P=0.06), for combination blood pressure lowering 89% v 59% (P<0.001), and for any blood pressure lowering 96% v 91% (P=0.02). Self reported adherence was highly concordant with dispensing data (dispensing of all four recommended drugs 79% fixed dose combination v 47% usual care, relative risk 1.67, 95% confidence interval 1.44 to 1.93, P<0.001). There was no statistically significant improvement in risk factor control between the fixed dose combination and usual care groups over 12 months: the difference in systolic blood pressure was -2.2 mm Hg (-4.5 v -2.3, 95% confidence interval -5.6 to 1.2, P=0.21), in diastolic blood pressure -1.2 mm Hg (-2.1 v -0.9, -3.2 to 0.8, P=0.22) and in low density lipoprotein cholesterol -0.05 mmol/L (-0.20 v -0.15, -0.17 to 0.08, P=0.46). The number of participants with cardiovascular events or serious adverse events was similar in both treatment groups (fixed dose combination 16 v usual care 18 (P=0.73), 99 v 93 (P=0.56), respectively). Fixed dose combination treatment was discontinued in 94 participants (37%). The most commonly reported reason for discontinuation was a side effect (54/75, 72%). Overall, 89% (227/256) of fixed dose combination participants' general practitioners completed a post-trial survey, and the fixed dose combination strategy was rated as satisfactory or very satisfactory for starting treatment (206/227, 91%), blood pressure control (180/220, 82%), cholesterol control (170/218, 78%), tolerability (181/223, 81%), and prescribing according to local guidelines (185/219, 84%). When participants were asked at 12 months how easy they found taking their prescribed drugs, most responded very easy or easy (224/246, 91% fixed dose combination v 212/246, 86% usual care, P=0.09). At 12 months the change in other lipid fractions, difference in EuroQol-5D, and difference in barriers to adherence did not differ significantly between the treatment groups.

CONCLUSIONS

Among this well treated primary care population, fixed dose combination treatment improved adherence to the combination of all recommended drugs but improvements in clinical risk factors were small and did not reach statistical significance. Acceptability was high for both general practitioners and patients, although the discontinuation rate was high.

TRIAL REGISTRATION

Australian New Zealand Clinical Trial Registry ACTRN12606000067572.

Incidence of acute rheumatic fever in New Zealand children and youth

AIM

  To estimate acute rheumatic fever (ARF) incidence rates for New Zealand children and youth by ethnicity, socioeconomic deprivation and region.

METHODS

  National hospital admissions with a principal diagnosis of ARF (ICD9_AM 390-392; ICD10-AM I00-I02) were obtained from routine statistics and stratified by age, ethnicity, socioeconomic deprivation index (NZDep2006) and District Health Board (DHB).

RESULTS

  The mean incidence rate for ARF in 2000-2009 peaked at 9 to 12 years of age. Incidence rates for children 5 to 14 years of age for Māori were 40.2 (95% confidence interval 36.8, 43.8), Pacific 81.2 (73.4, 89.6), non-Māori/Pacific 2.1 (1.6, 2.6) and all children 17.2 (16.1, 18.3) per 100 000. Māori and Pacific incidence rates increased by 79% and 73% in 1993-2009, while non-Māori/Pacific rates declined by 71%. Overall rates increased by 59%. In 2000-2009, Māori and Pacific children comprised 30% of children 5-14 years of age but accounted for 95% of new cases. Almost 90% of index cases of ARF were in the highest five deciles of socioeconomic deprivation and 70% were in the most deprived quintile. A child living in the most deprived decile has about one in 150 risk of being admitted to the hospital for ARF by 15 years of age. Ten DHBs containing 76% of the population 5 to 14 years of age accounted for 94% of index cases of ARF.

CONCLUSIONS

  ARF with its attendant rheumatic heart disease is an increasing public health issue for disadvantaged North Island communities with high concentrations of Māori and/or Pacific families.

Mortality and hospitalisation costs of rheumatic fever and rheumatic heart disease in New Zealand

AIMS

  To estimate the annual mortality and the cost of hospital admissions for acute rheumatic fever (ARF) and rheumatic heart disease (RHD) for New Zealand residents.

METHODS

  Hospital admissions in 2000-2009 with a principal diagnosis of ARF or RHD (ICD9_AM 390-398; ICD10-AM I00-I099) and deaths in 2000-2007 with RHD as the underlying cause were obtained from routine statistics. The cost of each admission was estimated by multiplying its diagnosis-related group (DRG) cost weight by the national price for financial year 2009/2010.

RESULTS

  There were on average 159 RHD deaths each year with a mean annual mortality rate of 4.4 per 100, 000 (95% confidence limit 4.2, 4.7). Age-adjusted mortality was five- to 10-fold higher for Māori and Pacific peoples than for non-Māori/Pacific. The mean age at RHD death (male/female) was 56.4/58.4 for Māori, 50.9/59.8 for Pacific and 78.2/80.6 for non-Māori, non-Pacific men and women. The average annual DRG-based cost of hospital admissions in 2000-2009 for ARF and RHD across all age groups was $12.0 million (95% confidence limit $11.1 million, $12.8 million). Heart valve surgery accounted for 28% of admissions and 71% of the cost. For children 5-14 years of age, valve surgery accounted for 7% of admissions and 27% of the cost. Two-thirds of the cost occurs after the age of 30.

CONCLUSIONS

  ARF and RHD comprise a burden of mortality and hospital cost concentrated largely in middle age. Māori and Pacific RHD mortality rates are substantially higher than those of non-Māori/Pacific.

Rotavirus infections and vaccines: burden of illness and potential impact of vaccination

Rotaviruses are the most common cause of severe gastroenteritis in children. By 5 years of age virtually every child worldwide will have experienced at least one rotavirus infection. This leads to an enormous disease burden, where every minute a child dies because of rotavirus infection and another four are hospitalized, at an annual societal cost in 2007 of $US2 billion. Most of the annual 527 000 deaths are in malnourished infants living in rural regions of low and middle income countries. In contrast, most measurable costs arise from medical expenses and lost parental wages in high income countries. Vaccines are the only public health prevention strategy likely to control rotavirus disease. They were developed to mimic the immunity following natural rotavirus infection that confers protection against severe gastroenteritis and consequently reduces the risk of primary healthcare utilization, hospitalization and death. The two currently licensed vaccines--one a single human strain rotavirus vaccine, the other a multiple strain human-bovine pentavalent reassortant rotavirus vaccine--are administered to infants in a two- or three-dose course, respectively, with the first dose given at 6-14 weeks of age. In various settings they are safe, immunogenic and efficacious against many different rotavirus genotypes. In high and middle income countries, rotavirus vaccines confer 85-100% protection against severe disease, while in low income regions of Africa and Asia, protection is less, at 46-77%. Despite this reduced efficacy in low income countries, the high burden of diarrheal disease in these regions means that proportionately more severe cases are prevented by vaccination than elsewhere. Post-licensure effectiveness studies show that rotavirus vaccines not only reduce rotavirus activity in infancy but they also decrease rates of rotavirus diarrhea in older and unimmunized children. A successful rotavirus vaccination program will rely upon sustained vaccine efficacy against diverse and evolving rotavirus strains and efficient vaccine delivery systems. The potential introduction of rotavirus vaccines into the world's poorest countries with the greatest rates of rotavirus-related mortality is expected to be very cost effective, while rotavirus vaccines should also be cost effective by international standards when incorporated into developed countries immunization schedules. Nonetheless, cost effectiveness in each country still depends largely on the local rotavirus mortality rate and the price of the vaccine in relation to the per capita gross domestic product.

Burden and cost of hospital admissions for vaccine-preventable paediatric pneumococcal disease and non-typable Haemophilus influenzae otitis media in New Zealand

INTRODUCTION

Streptococcus pneumoniae (Sp.) is a leading cause of paediatric bacterial meningitis, pneumonia and acute otitis media, as is non-typable Haemophilus influenzae (NTHi) for acute otitis media. In 2008, a 7-valent conjugated pneumococcal vaccine (PCV7) was included in the New Zealand (NZ) childhood immunization schedule.

OBJECTIVE

To estimate the potentially vaccine-preventable annual hospital admissions and cost to the NZ Government of paediatric admissions for pneumococcal disease and NTHi otitis media prior to the immunization programme.

METHODS

Admissions (2000-7) and deaths (2000-5) in children aged<20 years with pneumococcal meningitis or bacteraemia, pneumonia or otitis media were identified in national datasets and linked by unique patient identifiers. New episodes of illness were defined as admissions occurring >30 days after discharge from a previous admission. Informed by the literature, pneumococcal pneumonia episodes were estimated at 33% of all-cause pneumonia admissions; Sp. and NTHi otitis media episodes were estimated jointly at 72% of otitis media admissions. Each episode was assigned a single diagnosis according to the following hierarchy: meningitis>bacteraemia>pneumonia>otitis media. Incidence rates for episodes were determined for 2000-7 (meningitis, bacteraemia and pneumonia) and 2006-7 (otitis media). Annual DRG-based costs for pneumococcal meningitis, bacteraemia, pneumonia and otitis media were estimated as (episode rate)x(DRG cost weight per episode)x(2007 population)x(national price per cost weight).

RESULTS

Episode rates for pneumococcal meningitis, bacteraemia and pneumonia were stable in 2000-7, highest in the second 6 months of life and declined steeply over the first 5 years of life. Mean rates per 100000 in 2000-7 were 18.4, 27.6 and 464 for pneumococcal meningitis, bacteraemia and pneumonia, respectively, for children aged<2 years; 8.4, 14.9 and 295 for children aged<5 years (including those aged<2 years); and 2.2, 4.4 and 97 for children aged<20 years (including those aged<5 years). Mean rates per 100000 in 2006-7 for Sp. and NTHi otitis media combined were 631 (surgical) and 197 (medical) for children aged<2 years; 691 and 116 for children aged<5 years; and 281 and 35 for children aged<20 years. Pacific Island and indigenous Māori children generally had higher rates than European/other children. Rates increased with socioeconomic disadvantage, across all diagnoses. The annual cost to Government of pneumococcal disease and NTHi otitis media admissions for children aged<20 years was estimated at New Zealand dollars ($NZ)9.95 million (range 7.7-12.2 million) [about $US7.1 million]. Most of this cost was shared between pneumococcal pneumonia (48%) and otitis media (45%), and 78% was incurred in the first 2 years of life. Estimated annual paediatric mortality rates per 100 000 for children aged<5 years were 0.48, 0.30 and 0.54 for pneumococcal meningitis, bacteraemia and pneumonia, respectively. The analysis predicted four or five pneumococcal deaths per year (range 1-8) for children aged<5 years.

CONCLUSIONS

Prior to the introduction of a national Sp. immunization programme, hospital admissions for Sp. disease and NTHi otitis media in NZ cost about $NZ10 million annually, mostly for children aged<2 years and particularly for those living in relative socioeconomic deprivation and for Pacific Island and Māori children. There were about five pneumococcal deaths annually. With adjustment for local serotypes, vaccine serotype coverage and uptake, immunization with any of the three available pneumococcal vaccines would reduce this burden substantially.

Budget impact and cost-effectiveness of including a pentavalent rotavirus vaccine in the New Zealand childhood immunization schedule

OBJECTIVES

To estimate: 1) rotavirus disease burden in New Zealand children aged under 5 years, and 2) health benefits, budget impact, and cost-effectiveness of incorporating a pentavalent rotavirus vaccine (PRV) into the national immunization schedule.

METHODS

A static equilibrium model was developed to evaluate health benefits and budget impact of vaccinating five successive birth cohorts with PRV at $50 per dose and 85% coverage (three doses). Cost-effectiveness was estimated from the societal perspective in year 5 of the program, with future health benefits discounted at 3.5% per annum.

RESULTS

By the age of 5 years, one in five children will have sought medical advice for rotavirus gastroenteritis and one in 43 will have been hospitalized. In 2009, we estimate 1506 hospitalizations (476 per 100,000; 95% confidence interval 451, 502), 3086 Emergency Department (ED) presentations not requiring hospitalization, plus 10,120 cases of rotavirus gastroenteritis managed solely in primary care. The annual societal cost is $7.07 million, including 41% from hospitalization and 25% from caregiver income loss. Health benefits will increase and the cost of illness will decline by 78% in year 5 as successive birth cohorts are immunized. In the fifth year, 1191 hospitalizations, 2442 ED treated cases, 9762 primary care consultations, and 0.8 deaths will be averted. It requires six vaccinated children to avoid one primary care consultation, 49 to avert one hospitalization, and 73,357 to prevent one death. The incremental cost is $2.99 million and the break-even price per vaccine dose is $32.39 at 2006 prices. The cost is $2509 to avert one hospitalization and $305 to prevent one case seeking health-care assistance. The cost per life-year gained in year 5 is $143,097 and the cost per quality-adjusted life-year (QALY) gained is $46,092 (US$26,774). The cost per QALY is sensitive to incidence rates, vaccine price and efficacy, loss of quality of life by the child, case fatality, and caregiver income loss.

CONCLUSIONS

From a societal perspective, addition of PRV to the New Zealand childhood immunization schedule would confer important clinical gains at a modest cost per QALY gained.

Quality-of-life valuations of advanced breast cancer by New Zealand women

OBJECTIVES

To obtain health-related quality-of-life (HR-QOL) valuations (or 'utilities') from New Zealand women for four health states representative of advanced (metastatic) breast cancer, suitable for use in cost-utility analysis, and to compare four valuation methodologies.

METHODS

Written case descriptions of four health states representative of advanced breast cancer (hormonal therapy, chemotherapy, radiotherapy and hypercalcaemia) were developed in consultation with nine oncology professionals. Time trade-off (TTO) and visual analogue scale (VAS) valuations were obtained via interviews from a sample of 50 women, aged 25-69 years, randomly selected from the New Zealand general public and through informal networks. Representations of the four health states on the EQ-5D health state classification system were also obtained from the respondents and later valued using New Zealand and UK EQ-5D social tariffs.

RESULTS

The four valuation methods ranked the four states' mean valuations identically: hormonal therapy > chemotherapy > or = radiotherapy > hypercalcaemia. All methods except the TTO distinguished between chemotherapy and radiotherapy. In order of the VAS and TTO methods and the EQ-5D with NZ and UK tariffs, respectively, the valuations [mean (95% CI)] were: hormonal therapy 0.54 (0.48, 0.59); 0.65 (0.57, 0.73); 0.54 (0.51, 0.58); 0.60 (0.54, 0.65); chemotherapy 0.46 (0.41, 0.51); 0.49 (0.40, 0.57); 0.48 (0.43, 0.53); 0.51 (0.43, 0.59); radiotherapy for severe bone pain 0.35 (0.30, 0.40); 0.45 (0.37, 0.54); 0.31 (0.27, 0.35); 0.25 (0.18, 0.33); and moderate to severe hypercalcaemia 0.13 (0.09, 0.17); -0.17 (-0.29, -0.05); -0.05 (-0.07, -0.03); -0.52 (-0.56, -0.48). The four valuation methods gave similar results for chemotherapy, but for the three other states the TTO valuations differed from those obtained from the VAS method and the NZ and UK EQ-5D tariffs. There were significant pairwise correlations between the four methods across all four health states, although the valuation for hypercalcaemia obtained from the UK EQ-5D tariff was very low compared with the three other methods, and the VAS valuation was positive rather than negative.

CONCLUSION

Our study suggests that women in the New Zealand general public are able to consistently evaluate and value case descriptions of advanced breast cancer using either direct methods (VAS or TTO) or the EQ-5D health state classification system. Some of the valuations elicited using the four methods differ quantitatively, especially for hypercalcaemia. As our sample size was modest (50) and it turned out to be unrepresentative of the New Zealand female population, this study serves as a pilot study.

Treatment with drugs to lower blood pressure and blood cholesterol based on an individual's absolute cardiovascular risk

In this review, we outline the rationale for targeting blood pressure and blood cholesterol lowering drug treatments to patients at high absolute cardiovascular risk, irrespective of their blood pressure or blood cholesterol levels. Because the specific levels of blood pressure and cholesterol are of little clinical relevance when considered in isolation from other risk factors, terms such as hypertension or hypercholesterolaemia have limited value. Separate management guidelines for raised blood pressure and blood cholesterol need to be replaced by integrated cardiovascular risk management guidelines, and absolute cardiovascular risk prediction scores should be used routinely. Since cardiovascular risk factors interact with each other, moderate reductions in several risk factors can be more effective than major reductions in one. An affordable daily pill combining low doses of various drugs could be useful for the many individuals with slightly abnormal cardiovascular risk factors.

Communication of socioeconomic research findings

Socioeconomics is research that identifies, measures and compares the costs and the clinical, economic and humanistic consequences of diseases and healthcare interventions. Research findings must be communicated to be valuable. Publication moves research findings into the public domain and exposes hard won ideas to critical appraisal. The analyst or researcher informs the decision process by defining an answerable question, applying standard economic methodology, developing a credible study, and using appropriate analytical and communication tools. The decision-maker is more likely to listen if the message is relevant, clear, simple and timely, and if he/she has influence over the relevant budget. Traditional print media provide a standardised process for quality control, whereas electronic media can provide speed of publication and wide access, usually at the expense of quality. The quality of both published medical and socioeconomic research articles varies widely. Published checklists can greatly assist in determining the structural quality of a study, but they cannot guarantee that the content of an article is useful to a decision-maker. Barriers to communication include perceived lack of study credibility, lack of relevance to the decision under consideration, suspicion of bias and inadequate training of the readers. Journal editors aim to improve the readability and clarity of articles and to bring them into conformance with journal policies. Recommendations for effective communication include the following: determine the target audience(s) and develop the appropriate perspective; set the study in its clinical context; keep the language simple where possible and use multiple communication media. Well conducted and well communicated studies can influence policy and outcomes.

A predictive model of the health benefits and cost effectiveness of celiprolol and atenolol in primary prevention of cardiovascular disease in hypertensive patients

This study compares the antihypertensive and lipid modifying effects of treatment of mild to moderate hypertension with celiprolol or atenolol. It also models the 5-year cardiovascular risk reduction and the cost effectiveness of monotherapy from a partial societal perspective. The effects of celiprolol and atenolol on systolic blood pressure (SBP), total serum cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) were obtained from a pooled analysis of published studies. Although celiprolol and atenolol had similar effects on SBP, celiprolol reduced the ratio of TC to HDL-C by 10.2% [95% confidence intervals (95% CI) -16.4%, -4.0%) but atenolol increased the ratio by 7.7% (95% CI of 3.4%, 12.0%). The 5-year absolute risks of an initial coronary or cerebrovascular event or cardiovascular death were computed for cohorts of patients treated with either agent or remaining untreated, using an accelerated failure time (AFT) model, based on Framingham Heart Study data. Inputs to the model were age, gender, smoking status, SBP, TC and HDL-C. The change in absolute risk was estimated using the changes in SBP and TC: HDL-C obtained from the pooled analysis. Average life-months gained by therapy were computed as differences between the Kaplan-Meier survival curves estimated from the model plus differences in 5-year cardiovascular death rates multiplied by average life expectancy obtained from life tables. Direct medical costs included drug treatment, and the costs of acute care for initial coronary and cerebrovascular events deferred by therapy over the 5-year treatment period. The model shows that in the lowest-risk base case (60-year-old men who are nondiabetic and nonsmokers with SBP of 160 mm Hg and a 5-year absolute cardiovascular risk of 12%), celiprolol (271 mg/day) is 2-fold more effective than atenolol (77.4 mg/day) in reducing coronary event risk, and equally effective in reducing cerebrovascular event risk. The number of individuals that would have to be treated for 5 years to avoid 1 coronary event is about 30 for celiprolol versus 70 for atenolol. Therapy with celiprolol yields more life-months and at current prices, the cost per life-year gained by therapy is significantly lower. Both drugs are cost effective by international standards in the treatment of patients with 5-year absolute cardiovascular risk greater than 10%, and are more cost effective in those patients at higher levels of absolute cardiovascular risk. The direct medical costs of treatment for 5 years with celiprolol are the same or slightly less than treatment with atenolol at the dosages used in the clinical trials, despite a 19% higher tablet price. Both drugs are more cost effective in patients at higher levels of absolute cardiovascular risk. These findings are sensitive to the drug dosages, tablet prices and the discount rate. Based on epidemiological and clinical data, replacing atenolol with celiprolol in patients with mild to moderate hypertension, but without overt cardiovascular disease, is predicted to have similar effects on stroke risk, but to be substantially more effective in reducing the risk of coronary events at no additional direct medical cost over a 5-year treatment period.

Costs, innovation and efficiency in anti-infective therapy

This paper provides an overview of issues related to the emerging discipline of pharmacoeconomics and its relationship to the outcomes movement. The focus is upon the evolving Management Care Organisation (MCO) and the demands placed upon the pharmaceutical industry as it attempts to provide new innovative anti-infective treatments. Similarly, the challenge is to meet the ever increasing requirements for approval and reimbursement of new anti-infective pharmaceutical products. Outcomes research is playing an increasingly important role in such decisions throughout the world, including the United States. Unfortunately, most decisions and analysis at the national level and within MCOs regarding the adoption and utilisation of pharmaceuticals are rather unsophisticated in terms of the proper utilisation of pharmacoeconomic data. There is a prevalent need to better utilise this information to develop cost-effective disease and therapy intervention models and guidelines. Also, information on the application of pharmacoeconomics for the evaluation of pharmaceutical care services that enhance the cost effectiveness of drug therapy needs to be seriously considered. Specifically, this should include a consideration of the economic consequences of drug-related problems and the potential impact of pharmaceutical care on drug-related morbidity/mortality associated with the treatment of infectious disease.

Ondansetron: a pharmacoeconomic and quality-of-life evaluation of its antiemetic activity in patients receiving cancer chemotherapy

Ondansetron is more effective than high-dose metoclopramide in the prevention of acute nausea and vomiting due to highly emetogenic chemotherapy, and, unlike metoclopramide, is rarely associated with extrapyramidal effects. Pharmacoeconomic analyses have demonstrated that, in specified clinical settings, ondansetron (8mg 4-hourly for 3 doses or 8mg followed by 1 mg/h for 24 hours) is equally cost-effective as high-dose metoclopramide (3 mg/kg followed by 0.5 mg/kg/h for 8 hours) in the prophylaxis of emesis in patients receiving highly emetogenic chemotherapy, at an acquisition cost 4- or 5-fold higher than that of the metoclopramide regimen. Furthermore, the combination of dexamethasone plus ondansetron has been shown to be more effective than ondansetron monotherapy in controlling emesis. In patients receiving high-dose ( greater than 50 mg/m2) cisplatin-based chemotherapy, antiemetic therapy with ondansetron (8mg intravenously as a single dose) plus dexamethasone (16mg total intravenous dose) was shown to be more cost-effective than the combination of high-dose metoclopramide (11 mg/kg total intravenous dose), dexamethasone (8mg intravenously as a single dose) plus lorazepam (1 to 1.5mg intravenously as a single dose). In a limited number of studies, quality-of-life scores, as assessed using the Rotterdam Symptom Checklist or the Functional Living Index--Emesis instrument, were significantly higher with ondansetron than with other antiemetic agents, including metoclopramide. Together, these results suggest that ondansetron, as an alternative to antiemetic regimens including high-dose metoclopramide, is appropriate cost-effective therapy for the prevention of acute nausea and vomiting in patients receiving highly emetogenic chemotherapy. Ondansetron is effective in controlling acute emesis associated with moderately emetogenic chemotherapy, and its use in this clinical setting may best be reserved for patients who have not responded well to previous antiemetic therapy with more traditional agents. However, poorly controlled emesis can lead to anticipatory nausea and vomiting in subsequent courses of chemotherapy, thus, consideration should also be given to the use of ondansetron in patients receiving moderately emetogenic chemotherapy, although further pharmacoeconomic investigations are required to clarify its use in this clinical setting.

Selegiline: an appraisal of the basis of its pharmacoeconomic and quality-of-life benefits in Parkinson's disease

Selegiline (deprenyl) is a selective, irreversible cerebral monoamine oxidase type B inhibitor (MAO-B) that is used in the treatment of Parkinson's disease. It has a relatively mild adverse effect profile without risk of the tyramine ('cheese') reaction at normal therapeutic doses. In about half to two-thirds of patients with mild levodopa response fluctuations, selegiline improves overall disability and 'end-of-dose' fluctuations, with a levodopa-sparing effect. Selegiline thus may improve patient quality of life, although formal cost-utility analyses are required to establish the costs of these benefits. Cost-effectiveness studies may help characterise the relative pharmacoeconomic benefits of selegiline and the dopamine agonists, agents which can also be administered as adjuvant therapy at this stage of the disease. There is also evidence to suggest that selegiline may delay the need for levodopa therapy by up to 11 months in patients with early Parkinson's disease, although the relative contribution of neuroprotective and symptomatic effects of selegiline in these patients has yet to be clarified. From a societal perspective, a theoretical analysis indicates that the economic benefits of selegiline therapy are likely to be substantial. An agent which slowed progression of disability by around 10% would realise savings, through reduction in both direct and indirect costs, in the order of $US330 million per annum in the United States. Available data suggest that selegiline slows progression of symptoms well in excess of 10%. Further, if a simple and inexpensive method is developed to identify preclinical Parkinson's disease before nigrostriatal damage is advanced, selegiline may be useful in a broader patient population with possible financial benefits to society through reduction of the considerable indirect costs of Parkinson's disease.

Recombinant granulocyte colony-stimulating factor (rG-CSF): pharmacoeconomic considerations in chemotherapy-induced neutropenia

Recombinant granulocyte colony-stimulating factor (rG-CSF) therapy is associated with a dose-proportional reduction in the frequency, duration and severity of neutropenia associated with cytotoxic chemotherapy. This is associated with a decrease in the incidence of infection, with subsequent reductions in the number of hospitalisations, days of hospitalisation and antibiotic requirements. These effects produce marked reductions in costs, and could contribute substantially towards offsetting the costs of rG-CSF, although the magnitude of the savings will vary between institutions and with the chemotherapy regimen used. Other benefits include a reduction in the frequency and severity of mucositis, and an improved patient quality of life. However, further research is required to evaluate other potentially important considerations including the targeting of specific patient populations (e.g. those receiving regimens with a curative intent), and additional improvements in patient quality of life and, perhaps, mortality. Thus, although specific pharmacoeconomic analyses are limited, preliminary evidence indicates that rG-CSF, administered prior to the onset of neutropenia in patients receiving cytotoxic chemotherapy, can provide cost reductions both from an institutional and a payor perspective, with even greater potential savings from a societal viewpoint.

Simvastatin: a pharmacoeconomic evaluation of its cost-effectiveness in hypercholesterolaemia and prevention of coronary heart disease

Epidemiological and intervention study results support reduction of coronary heart disease (CHD) risk, and hence direct and indirect costs, by lowering plasma lipids. Cost-effectiveness of a lipid-lowering strategy thus depends significantly on the extent of plasma lipid decrease achieved. The 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor simvastatin is a well tolerated and highly effective antihyperlipidaemic agent. Despite a current lack of direct evidence that simvastatin reduces CHD incidence, the cost-effectiveness of the drug {in terms of years of life saved (YOLS)} has been studied, based on findings of epidemiological trials. Simvastatin 20 mg/day is more cost-effective than cholestyramine 4g 3 times daily, particularly in men and in those with a higher pretreatment cholesterol level ( greater than 8 mmol/L) and other risk factors. Cost-effectiveness is also enhanced if treatment is started at a younger age (35 to 45 years) and maintained for a defined period rather than lifelong. Thus, while additional direct comparative studies are needed to confirm this finding, present evidence suggests simvastatin is a cost-effective intervention in appropriately selected patients.

Habituation to repeated painful and non-painful cutaneous stimuli: a quantitative psychophysical study

Repeated stimuli elicit progressively smaller responses and elevated sensory and/or pain thresholds (habituation). The present experiments were designed to determine the rate of habituation of perceptual responses to supraliminal painful and non-painful cutaneous stimuli. Changes in the perceived intensity of electrical stimuli applied to the digital nerves of the index finger were determined by a matching procedure in which subjects set the current applied to the index finger of one hand to match the perceived intensity of a stimulus train (5 pulses at 20 Hz) applied to the other index finger. Twenty-five volunteers took part in 7 experiments in which both non-painful (2.5 times the sensory threshold Ts) and painful (1.2 times the pain threshold Tp) stimulus trains were presented. Subjects were required to match the stimuli at 30 s intervals over a period of 7.5 min. The percentage change in matching current (Y) was fitted by the function Y = -20.7*[1-exp(-0.56*t)] for both painful and non-painful stimuli repeated at 2 Hz. Responses recovered completely within 2 min of cessation of the stimulation. The degree of habituation increased or decreased with the rate of stimulus presentation. These results did not depend on changes in afferent fibre recruitment or fatigue because the afferent volley on the median nerve remained constant throughout the period of stimulation. Thus perceptual responses to the perceived intensity of supraliminal painful and non-painful stimuli delivered to the index finger habituate to the same extent, and the extent of the habituation is a function of the frequency of presentation of the stimulus.

Celiprolol. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in cardiovascular disease

Celiprolol is a hydrophilic, beta 1-selective adrenoceptor antagonist with mild selective beta 2-agonist as well as weak vasodilator properties. Celiprolol 200 to 400mg once daily by mouth is similar in antihypertensive efficacy to usual doses of propranolol, atenolol, metoprolol and pindolol in patients with mild to moderate systemic hypertension. Similar doses of celiprolol are as efficacious as propranolol and atenolol in improving exercise tolerance and reducing the frequency of anginal attacks in patients with angina pectoris. Further clinical experience suggests that celiprolol does not produce bronchoconstriction and may have mild bronchodilating activity in asthmatic patients; it may also enhance the effects of bronchodilator drugs. Celiprolol has a slightly beneficial effect on serum lipid profiles, and does not appear to exert adverse effects on carbohydrate metabolism. If the apparent pharmacodynamic advantages of celiprolol translate into clinical benefits and are confirmed in well designed long term clinical trials, then celiprolol should represent a definite advance in beta-blocker therapy.

Ondansetron. Therapeutic use as an antiemetic

Ondansetron (GR 38032F) is a highly selective 5-HT3 receptor antagonist, one of a new class of compounds which may have several therapeutic applications. Animal and clinical studies show that ondansetron reduces the 24-hour incidence and severity of nausea and vomiting induced by cytotoxic drugs, including cisplatin, and by single exposure, high dose radiation. Ondansetron is more effective than high dose metoclopramide in the 24 hours following chemotherapy, and preliminary clinical evidence suggests that it is equally effective in the following 4 days. It is also more effective than the 'moderate' doses of metoclopramide used to suppress emesis following radiotherapy. The antiemetic efficacy of ondansetron is enhanced by dexamethasone in cisplatin-treated patients. Importantly, extrapyramidal effects have not been reported with ondansetron. Further comparisons are required with standard combination antiemetic therapy to complement the data presently available. Thus, ondansetron is a promising new agent for prophylaxis against nausea and vomiting in chemotherapy and radiotherapy. It may be particularly useful in young and elderly patients who are more susceptible to extrapyramidal symptoms induced by high dose metoclopramide. With its improved tolerability and clinical response profiles, ondansetron represents an important advance in a difficult area of therapeutics.

Citalopram. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in depressive illness

Citalopram is an antidepressant belonging to a new class of drugs which enhance serotoninergic neurotransmission through potent and selective inhibition of serotonin reuptake. Preliminary trials suggest that its short term therapeutic efficacy is significantly greater than that of placebo and mianserin, and comparable to that of amitriptyline, maprotiline and imipramine. It appears to be a weaker antidepressant agent than clomipramine, but better tolerated. Its elimination half-life of 33 hours permits once daily oral administration. Symptomatic improvement obtained with short term treatment has been maintained when therapy has been extended for up to 1 year; in the few patients studied for this extended period, the relapse rate was lower than with fluvoxamine, fluoxetine or imipramine. Compared to standard antidepressant agents, citalopram is well tolerated. It does not appear to be cardiotoxic, has not been associated with seizures in humans, and is relatively nonsedating. Unlike the tricyclic antidepressants, citalopram has minimal anticholinergic effects. Mild and transient nausea, with or without vomiting, is the most frequent adverse effect--occurring in 20% of patients--and increased perspiration, headache, dry mouth, tremor and insomnia are experienced by 15 to 18% of patients. Citalopram thus offers similar therapeutic efficacy and a more favourable tolerability profile than the tricyclic antidepressants. Preliminary data suggest that it may be particularly useful in patients who cannot tolerate the anticholinergic or cardiovascular side effects of tricyclic antidepressants and in those for whom sedation is not indicated.

Quaternary naloxone blocks morphine analgesia in spinal but not intact rats

Quaternary derivatives of naloxone and other compounds are assumed not to enter the central nervous system following systemic administration. We report that i.p. naloxone methylbromide (5 mg/kg) completely reversed the antinociceptive effect of systemically administered morphine (6 mg/kg) in acutely spinalised rats, although it had no effect in the same animals prior to the transection. Naloxone hydrochloride was effective both before and after transection. Nuclear resonance spectra confirmed the purity of both compounds. These results suggest that acute spinal transection allows rapid entry of quaternary naloxone into the spinal cord. Quaternary compounds therefore may need to be used with caution in spinalised animals.

Behavioural modification of bulbospinal serotonergic inhibition and morphine analgesia

Habituation to the stress of sham nociceptive testing enhances a rat's sensitivity to noxious thermal stimuli and reduces the antinociceptive effect of a subsequent acute dose of morphine. Since serotonin (5-hydroxytryptamine, 5-HT) mediates stress responses, experiments were designed to elucidate the role of 5-HT in these phenomena. Intrathecal methysergide or 5,7-dihydroxytryptamine (5,7-DHT) reduced baseline tail-flick latencies of novice rats to those of habituated animals. Morphine dose-response relationships were fitted to a 4 parameter sigmoidal function. Baseline latencies of novice animals were increased by 5-hydroxytryptophan (5-HTP) and reduced by parachlorophenylalanine (PCPA) in both reflex tests and in the hot-plate test, but latencies of habituated animals were unchanged by either treatment. In both reflex tests, the maximum effect due to morphine was increased by 5-HTP and reduced by PCPA in novice but not in habituated animals. We conclude that the serotonergic component of morphine's bulbospinal action represents the stress of the testing environment rather than an essential part of morphine's action.

Hypercapnia depresses nociception: endogenous opioids implicated

Hypoventilation produces hypercapnia which can elevate pain thresholds. Hypercapnia is a potent stressor which releases catecholamines and activates the sympathetic nervous system. Some stressors produce analgesia by releasing endogenous opioids. To determine the roles of endogenous opioids and catecholamines in hypercapnic analgesia, we administered CO2 in the inspired gas mixture to conscious rats. CO2 in the range 5-10% elevated tail flick and leg flexion latencies 2- to 3-fold in both intact and spinalised animals. The effects on reflex latencies but not on paCO2 or pHa were blocked by naloxone (2 mg/kg), and were not present in morphine-tolerant animals. The effects were reduced by dexamethasone but were not changed either by adrenalectomy or by systemic guanethidine, propanolol or phentolamine. Hypercapnia delayed the onset of the late phase of behavioural responses to formalin injected into the plantar surface of the hindpaw. We conclude that moderate hypercapnia powerfully depresses flexor withdrawal responses to noxious stimuli, by a mechanism involving release of endogenous opioids but not systemic catecholamines. This effect may account in part for the elevation in pain threshold during hypoventilation.

Habituation to sham testing procedures modifies tail-flick latencies: effects on nociception rather than vasomotor tone

Habituation of rats to the testing environment and procedures reduces flexor withdrawal latencies to those of spinalised animals. We have now recorded surface temperatures at 3 sites on the tail and tail-flick latencies simultaneously in experimentally naive (novice) rats and in habituated rats. At usual ambient temperatures (20 +/- 1 degree C), tail temperatures fluctuated in accordance with the predictions of an on-off controller. There was an inverse correlation between the tail-flick latency and the temperature at the site of noxious stimulation. A similar correlation was found when the pre-stimulus temperature of the tip of the tail was held at temperatures ranging from 21 degrees C to 35 degrees C. Habituated animals exhibited a similar linear regression slope factor but lower latencies than novice animals at each temperature. We conclude (1) that tail-flick latency is determined partly by the pre-stimulus temperature at the site of noxious thermal stimulation, and (2) that the effects of habituation on tail-flick latency are more likely to be explained by differences in nociception than in regional vasomotor tone.

Behavioural tolerance to morphine analgesia is supraspinally mediated: a quantitative analysis of dose-response relationships

Repeated exposure of a rat to a nociceptive testing environment ('habituation') enhances its sensitivity to noxious thermal stimuli20 and reduces the antinociceptive effect of a subsequent acute dose of morphine ('behavioural tolerance'). The present study quantitatively characterises the effects of habituation upon morphine antinociception using hot-plate (50 and 55 degrees C) and reflex withdrawal tests (dipping the tail and hindpaws into water at 49 degrees C). Dose-response relationships were modeled with the empirical function; E = Eo + (EMAX*DN)/(ED50N + DN) where E is the time-integrated response, EMAX is the response attributable to morphine, Eo is the baseline response, D is the dose and N is a steepness parameter. Habituation reduced EMAX in both hot-plate tests and also reduced Eo on the 50 degrees C hot-plate. In both reflex tests, habituation reduced Eo to that of spinal animals and EMAX to a value intermediate between that of intact and spinal animals. Neither the ED50 nor the value of N was altered by habituation. Acute spinal novice and habituated animals had similar dose-response curves and parameters. Sham spinalisation had no significant effect on any of the parameters. It is concluded that habituation to the nociceptive testing environment substantially reduces the bulbospinal contribution to morphine analgesia but has no effect upon the spinal component.

Repeated exposure to sham testing procedures reduces reflex withdrawal and hot-plate latencies: attenuation of tonic descending inhibition?

Five days' repeated exposure of experimentally naive rats to the experimental environment and to sham nociceptive testing procedures ('habituation') reduced the latency for reflex withdrawal of the hindpaw from hot water (49 degrees C) by 43%, to that of spinalised habituated or novice animals. Hot-plate (50 degrees C) paw lick latencies were reduced equally (40%) by habituation or parachlorophenylalanine, and were increased 32% by D,L-5-hydroxytryptophan. Neither drug affected hot-plate latencies of habituated animals. Naloxone had no effect on flexor withdrawal or hot-plate latencies in either novice or habituated animals. These results suggest that habituation substantially attenuates tonic serotonergic inhibition of spinal nociceptive transmission.

Reduction in perceived intensity of cutaneous stimuli during movement: a quantitative study

The effect of movement of the index finger on the perceived intensity of trains of electrical stimuli to the digital nerves of the same finger was studied quantitatively using a novel intramodality stimulus-matching task. Subjects consistently were able to match reliably the perceived intensity of stimuli delivered on the 'reference' side with that of stimuli delivered simultaneously to the digital nerves of the index finger on the other ('matching') side. Both active and passive movement of the index finger (on the reference side) in the palmar plane reduced the matched stimulus voltage by about 10% of its control value for stimuli at twice the sensory threshold. This reduction in perceived intensity did not persist beyond the period of stimulation. An isometric contraction of first dorsal interosseous muscle produced a smaller, but statistically significant, reduction in perceived intensity. Non-noxious electrical stimulation of the digital nerves of the ipsilateral thumb or little finger also reduced the perceived intensity of stimuli to the index finger. Perceived intensity of stimuli during movement was also reduced, but to a lesser extent, when the index finger was stimulated at painful levels. Psychophysical studies using open magnitude scaling indicated that the relationship between stimulus intensity and perceived magnitude of electrical stimuli could be described by a power law with an exponent close to 1.0. Therefore, the percentage reduction in matching voltage accurately represents the percentage decline in perceived intensity. These results suggest that the perceived intensity of cutaneous stimuli to the index finger over a range of intensities can be reduced by afferent activity from the hand. The motor command appears to play a relatively minor role in modulating the perceived intensity.

Changes in perceived heaviness and motor commands produced by cutaneous reflexes in man

1. This study examined the relationship between the perceived heaviness of a weight and reflexes acting on the motoneurones required for the contraction. The perceived heaviness of low (100 g) and high (500 g) reference weights lifted by the first dorsal interosseous muscle was estimated using a matching task. Weights were also lifted during stimulation of the digital nerves of the index finger at two times and four times sensory threshold (T). Averages of force and EMG were also made when isometric forces of 100 and 500 g were maintained. 2. Stimuli at 4T produced a significant increase in perceived heaviness in each subject for both reference weights. Averages of EMG made under isometric conditions showed a short-latency inhibition with a reflex reduction in force following single stimuli. This inhibition was also observed during weight lifting when trains of stimuli were given. 3. Stimuli at 2T produced less-marked changes in EMG, averaged force, and perceived heaviness for individual subjects. However, for the group of subjects, perceived heaviness declined significantly with 2T stimuli for the 500 g but not the 100 g weight. This decrease in perceived heaviness was associated with evidence of short-latency facilitation within the motoneurone pool. 4. Inhibition of the motoneurone pool was associated with an increase and facilitation with a decrease in perceived heaviness. These observations favour a role for a signal of centrally generated motor command in the sensation of heaviness and provide insight as to how this signal must change when reflex inputs change and when high-threshold motoneurones are recruited.

Contralateral intramuscular acupuncture-like electrical stimulation differentially changes the short-latency responses to muscle stretch

Measurements were made from the human first dorsal interosseous and extensor digitorum communis muscles of the surface electromyographic activity reflexly produced by brief stretch of the muscle. For the first dorsal interosseous muscle, reflex EMG activity was also produced by electrical stimulation of the ulnar nerve at the wrist. The procedures were carried out before, during, and after 25 min of nonspecific, low-frequency electrical stimulation to the contralateral arm delivered through intramuscular electrodes. Control stimulation was delivered subcutaneously. The EMG recorded during a maintained contraction was rectified, filtered, and averaged. Two reflex components (M1 and M2) of the EMG response to muscle stretch or ulnar nerve stimulation were investigated. During nonspecific intramuscular stimulation to the contralateral arm, M1 responses of the extensor digitorum communis were depressed, initially by 37%. The effect began to fade during stimulation but extended beyond it. Reflex responses were elicited alternately by brief stretch of the first dorsal interosseus muscle and by electrical stimulation of the ulnar nerve in the same experiment. Nonspecific intramuscular stimulation to the contralateral arm depressed the M1 response to stretch, but had no effect on the M1 response to electrical stimulation. It is concluded that nonspecific intramuscular electrical stimulation reduces the amplitude of the M1 component of the response to brief stretch of contralateral muscle, either through depression of fusimotor activity or inhibition of oligosynaptic pathways that contribute to the early reflex response.

Intramuscular acupuncture-like electrical stimulation inhibits stretch reflexes in contralateral finger extensor muscles

Electro-acupuncture is one of many physical measures used to relieve musculoskeletal pain and to improve the associated restricted range of motion. Experiments were designed to determine whether or not acupuncture-like stimulation inhibits stretch reflexes in an arm extensor muscle in human volunteers. Surface electromyographic recordings were made on the right extensor digitorum communis muscle and averaging techniques were used to study the reflex responses to brief deflection of the finger with a solenoid-driven probe. The ratio M1:M2 of two components of the reflex was reduced during continuous acupuncture-like stimulation of the contralateral first dorsal interosseus and extensor digitorum communis muscles near their motor points (acupuncture points LI 4 and LI 11). Concomitant changes in skin temperature were observed on the forehead and in the arm in which acupuncture-like stimulation was used. In control experiments, when the acupuncture needles were inserted subcutaneously and stimulated with the same current parameters at distinctly uncomfortable intensities, no change in the reflexes occurred. These findings show that acupuncture-like stimulation exerts physiologic effects on the central nervous system, mediated presumably by muscle afferent fibers. The effects may be relevant to relief of muscle spasm and musculoskeletal pain, and restoration of mobility.

Responses of primate spinothalamic neurons located in the sacral intermediomedial gray (Stilling's nucleus) to proprioceptive input from the tail

Extracellular an intracellular recordings were obtained from 24 spinothalamic neurons located in the intermediomedial gray (Stilling's nucleus) in the S2 and S3 spinal segments of anesthetized adult monkeys (Macaca fascicularis). Most units were spontaneously active. They lacked cutaneous receptive fields but could be excited by subcutaneous receptors. Bending the tail to one side of the animal's body axis excited cells located on the contralateral side of the cord an inhibited ipsilateral cells. The firing rate of each cell was a reproducible function of the angle of the portion of the tail distal to the innervated segment. Cells responded with a burst of spikes to electrical stimulation of low threshold ipsilateral primary afferent fibers in the homosegmental dorsal root. The latency of the underlying synaptic potential was 0.5-0.7 ms from the time of arrival of the afferent volley at the cord, indicating monosynaptic input. Low intensity stimulation of the contralateral homosegmental dorsal root inhibited back-ground activity. The latency of the underlying inhibitory synaptic potential was 0.8-1.1 ms, suggesting crossed disynaptic inhibition. We conclude that sacral spinothalamic tract neurons located in the intermediomedial gray participate in signalling the spatial orientation of the animal's tail.

Parasympathetic preganglionic neurons in the sacral spinal cord

Two types of preganglionic neurons have been identified in the sacral parasympathetic nucleus (SPN) of the cat. These neurons could be differentiated by various characteristics including axonal conduction velocities, morphology, location in the nucleus, organ of innervation and central reflex mechanisms controlling their activity. Neurons having myelinated axons (B-PGNs) with conduction velocities between 3.3 and 13 m/s were located in the lateral band of the SPN and innervated the urinary bladder. Neurons with unmyelinated axons (C-PGNs) with conduction velocities of 0.5-1.4 m/s were located in the dorsal band of the nucleus and innervated the large intestine. B-PGNs were excited by distention of the bladder and inhibited by distension or mechanical stimulation of the intestine, whereas C-PGNs exhibited the opposite responses to these stimuli. C-PGNs often exhibited a low level of spontaneous discharge in absence of stimulation but exhibited marked firing (3.5-10 spikes/s) during a defecation reflex elicited by mechanical stimulation of the rectum-anal canal. The excitatory responses were elicited by C-fiber afferents via a spinal reflex pathway. B-PGNs were inactive when intravesical pressure was below the threshold for inducing micturition (5 cm H2O) but raising the pressure above the threshold induced firing consisting of repetitive bursts of action potentials occurring at relatively high frequencies (15-60 spikes/s). These bursts coincided with rhythmic bladder contractions. The frequency of bladder contractions and associated bursts of PGN-firing and the mean PGN-firing rate (2-8 spikes/s) increased as intravesical pressure was increased in steps between 5 and 30 cm H2O. However, as indicated by interspike interval histograms, the frequency of firing within a burst of action potentials was unchanged. It is concluded that the micturition reflex pathway is organized as a simple on-off switching circuit and that B-PGNs receive a maximal synaptic input when intravesical pressure exceeds the micturition threshold. This circuit was triggered by vesical A delta afferents via a spinobulbospinal pathway. Transection of the spinal cord interrupted the reflex pathway and blocked micturition. However, in chronic spinal animals a spinal reflex mechanisms emerged which contributed to the recovery of bladder function. This mechanism, which was weak or non-existent in animals with an intact neuraxis, exhibited a number of important differences from the normal micturition reflex, most notably being activated by a C-fiber afferent rather than a A delta afferent limb. The mechanism underlying the emergence of C-fiber evoked bladder reflexes in spinal animals is uncertain.

Convergence of cutaneous and pelvic visceral nociceptive inputs onto primate spinothalamic neurons

The responses of 66 primate spinothalamic neurons to natural stimulation the the urinary bladder and testicle were studied with extracellular recording techniques in order to elucidate the neural basis for referral of visceral pain. Thirty-eight out of 53 cells located at the thoraco-lumbar junction or in sacral segments responded to noxious cutaneous stimuli, and 84% of these also exhibited phasic and/or tonic excitatory responses to distension of the urinary bladder. Seventeen out of 20 of these units, all located at the thoraco-lumbar junction, were excited by compression of the ipsilateral testicle. The response was graded with the compressive force. Excitatory responses to noxious heat and an irritant chemical (KC1) applied to the exposed testicular surface were also observed. Twelve sacral units having inputs from deep receptor of the tail exhibited mixed excitatory and inhibitory responses to bladder distension. A further 2 cells located at the thoracolumbar junction responded only to cutaneous tactile stimuli, and 13 cells located at the lumbosacral enlargement were tonically inhibited by bladder distension. It is concluded that spinothalamic neurons that convey nociceptive input from the skin may also respond to noxious visceral stimuli. Such viscero-somatic convergence provides a neural substrate for the phenomenon of cutaneous referral of visceral pain.

Organization of the sacral parasympathetic reflex pathways to the urinary bladder and large intestine

Electrophysiological and horseradish peroxidase (HRP) techniques have provided new insights into the organization of the sacral parasympathetic reflex pathways to the large intestine and urinary bladder. The innervation of the two organs arises from separate groups of sacral preganglionic cells: (1) a dorsal band of cells in laminae V and VI providing an input to the intestine; and (2) a lateral band of cells in lamina VII providing an input to the bladder. These two groups of cells were separated by an interband region containing tract cells and interneurons. Neurons in the interband region received a visceral afferent input and exhibited firing correlated with the activity of intestine and urinary bladder. It seems reasonable therefore to consider the interband region as a third component of the sacral parasympathetic nucleus. Anterograde transport of HRP revealed that visceral afferents from the intestine and bladder projected into the parasympathetic nucleus. Most of the projections were collaterals from afferent axons in Lissauer's tract that passed in lamina I laterally and medially around the dorsal horn. These afferent collaterals were located in close proximity to preganglionic perikarya and dendrites in laminae I, V and VI. The proximity of visceral afferents and efferents in the sacral cord probably reflects the existence of polysynaptic rather than monosynaptic connections since electrophysiological studies revealed that both the defecation and micturition reflexes occurred with very long central delays (45-70 msec). The reflex pathways mediating defecation and micturition in cats with an intact neuraxis were markedly different. Defecation was dependent upon a spinal reflex with unmyelinated (C-fiber) peripheral afferent and efferent limbs. On the other hand, micturition was mediated by a spinobulbospinal pathway with myelinated peripheral afferent (A-fiber) and efferent axons (B-fiber). Transection of the spinal cord at T12-L2 blocked the micturition reflex but only transiently depressed the defecation reflex. In chronic spinal cats the micturition reflex recovered 1-2 weeks after spinalization; however, in these animals bladder-to-bladder micturition reflexes were elicited by C-fiber rather than A-fiber afferents. The C-fiber afferent-evoked reflex was weak or undetectable in animals with an intact neuraxis. Transection of the spinal cord also changed the micturition reflex in neonatal kittens (age 5-28 days). In neonates with an intact neuraxis bladder-to-bladder reflexes occurred via a long latency spinobulbospinal pathway (325-430 msec). The long latency is attributable to the slow conduction velocity in immature unmyelinated peripheral and central axons. In chronic spinal kittens (3-7 days after spinalization) the long latency reflex was abolished and a shorter latency (90-150 msec) bladder reflex was unmasked. The emergence of this spinal pathway may reflect axonal sprouting and the formation of new reflex connections within the sacral parasympathetic nucleus.

Effects of 2,4-dinitrophenol amylobarbitone and certain other drugs on the rate of oxygen consumption and force of contraction of isolated curarized diaphragm muscle of the rat

1 A technique has been developed for studying over periods of 10 min or longer the effects of drugs on both the force of electrically-induced contractions and the oxygen consumption of an isolated, curarized, mammalian, skeletal muscle preparation.2 The resting oxygen consumption of the muscle was increased substantially by 2,4-dinitrophenol in concentrations (0.02 mM and higher) that eventually produced contracture. Two other uncoupling agents, 4,6-dinitro-o-cresol and carbonylcyanide-p-trifluoromethoxyphenylhydrazone, behaved similarly.3 The oxygen consumption over 10 min of the stimulated muscle was also increased by 2,4-dinitrophenol (0.05 mM), although the strength of the ;maximal' contractions was lessened.4 Amylobarbitone increased the strength of contraction at a concentration (0.2 mM) that did not affect oxygen consumption significantly. Amylobarbitone and pentobarbitone also increased it at a concentration (1 mM) that depressed oxygen consumption. They decreased both strength of contraction and oxygen consumption at a concentration of 5 mM. Phenobarbitone had a weaker action.5 S-n-decyl-thiouronium increased oxygen consumption when given at a concentration (1 mM) that diminished strength of contraction and eventually produced contracture of the muscle.6 Both S-methyl-thiouronium (1 mM) and 4-aminopyridine (0.1 mM and 0.5 mM) increased strength of contraction without increasing oxygen consumption. Neither strength of contraction nor oxygen uptake was affected by ouabain (up to 0.01 mM) or by phenformin (0.1 mM).7 It is concluded that the response to 2,4-dinitrophenol is due mainly, if not wholly, to its known ability to uncouple oxidative phosphorylation; that the response to the barbiturates is due to a combination of a known metabolic action (viz., blocking of the respiratory chain) and a stimulant action on muscle; and the response to S-n-decyl-thiouronium to a disruptive action on cell membranes. The disproportionate actions of 4-aminopyridine and S-methyl-thiouronium on strength of contraction relative to oxygen consumption are also attributed to a non-metabolic action.