The Hobart Salt Study 1995: few meet national sodium intake target

OBJECTIVE

To estimate 24-hour sodium and potassium excretion in an urban Australian population.

DESIGN AND SETTING

Cross-sectional survey of an urban population in Hobart, Tasmania, in 1995.

PARTICIPANTS

Systematic sample (87 men, 107 women) from the Commonwealth Electoral Roll of people aged 18-70 years on 30 June 1995 whose residential address was within 10 km of the Hobart General Post Office.

MAIN OUTCOME MEASURE

Conformity with the national target for sodium intake for the year 2000 of < or = 100 mmol/day.

RESULTS

The target was met by 6% of men and 36% of women. This difference between the sexes was significant (P < 0.001), while differences between age groups and socioeconomic levels were not significant.

CONCLUSION

Our findings confirm the low level of conformity with the national sodium target reported by the handful of Australian studies over the past decade. Given the major community costs associated with hypertension, our results highlight the need for effective and properly monitored action to reduce sodium intakes.

Maternal selenium levels and sudden infant death syndrome (SIDS)

BACKGROUND

The possibility is tested that low anti-oxidant status and/or low levels of selenium (Se) might predispose to Sudden Infant Death Syndrome (SIDS).

AIM

This study was undertaken to collect evidence on the Se status of pregnant and non-pregnant women and newborn babies and to establish whether babies who later died of cot death had significantly divergent levels of blood Se at birth.

METHODOLOGY

Aliquots of blood were collected from all newly pregnant mothers in Tasmania and from the cords of all newborn babies. These were analysed for Se and glutathione peroxidase (GPx) content and compared by season and with non-pregnant, age standardised blood donors in three areas of Tasmania and three mainland Australian States.

RESULTS

Cot death babies' cordbloods were not significantly different in Se or GPx-status, in this small sample, from those of other babies, nor was a seasonal variation in these parameters demonstrated among 390 randomly selected Tasmanian mothers. Mothers-to-be showed a decrease in enzyme levels during pregnancy and Tasmanian blood donors had significantly lower levels than donors from other States.

CONCLUSION

While no evidence can safely be drawn about a relationship between Se or GPx-status and SIDS, this study provides base level measures for populations showing that Tasmanian residents have low levels of these anti-oxidants.

Clinical response in epilepsy in relation to total and free serum levels of phenytoin

The relationships between total and free serum concentrations of phenytoin and the clinical control of seizures were investigated retrospectively in 114 patients. Total phenytoin levels were measured by enzyme-modified immunoassay (EMIT), and the free fraction by ultrafiltration at 37 degrees C using 14C-labelled phenytoin as a tracer. The median free fraction in 188 serum samples was 13.7% (range 8.9-27.0%). The free fraction was greater than 18% in 34 (18.1%) of the serum samples. In all but 5 samples, a likely reason for the elevated free fraction could be determined. The identifiable reasons were commonly hypoalbuminaemia and the presence of liver or renal disease. There was a significant negative correlation between serum albumin level and free fraction of phenytoin (n = 90, r = -0.68, p less than 0.001). The free phenytoin concentration was strongly correlated with the total phenytoin concentration in serum (n = 188, r = 0.94, p less than 0.001). The total phenytoin concentration provided as good an indication of clinical response as the free concentration in 91 patients (85.8% of the patients for whom response could be reliably determined). In the other 15 (14.2%) patients, free phenytoin concentrations were better related to clinical effect. These patients generally had significant reductions in the serum protein binding of phenytoin. The relationship between phenytoin toxicity and free serum concentrations was particularly strong--in 14 patients with toxicity, the total serum concentration of phenytoin was greater than 80 mumol/L in only 42.9% of cases, while the free phenytoin concentration was greater than 8 mumol/L in 85.7% of the cases (p less than 0.05 by chi-square test).(ABSTRACT TRUNCATED AT 250 WORDS)

Dosage prescribing and plasma oxipurinol levels in patients receiving allopurinol therapy

This study examined dosage prescribing patterns and steady-state oxipurinol plasma concentrations in 66 patients receiving chronic allopurinol therapy. Most patients (65%) were taking 300 mg allopurinol daily, although renal impairment was common. Using published guidelines, it was estimated that 35% of patients were receiving excessive dosages of allopurinol. Consequently, the plasma oxipurinol concentrations were often very high (mean (SD) was 156 (109) mumol.l-1). Accumulation of oxipurinol was inversely related to renal function. Plasma concentrations of oxipurinol and urate were not significantly related. However, most patients with oxipurinol concentrations of up to 100 mumol.l-1 had urate concentrations within the normal reference range.

Audit of a monitoring service for free phenytoin

This study assessed the value of introducing the measurement of free phenytoin levels in a public hospital. After publicising the availability and purpose of the assay, free phenytoin levels were determined either (a) on the doctor's request or (b) when the total level was requested and the patient's record showed evidence of factors predisposing to an elevated unbound fraction. Total phenytoin was measured by EMIT, and the unbound fraction by ultrafiltration at 37 degrees C using [14C]-phenytoin as a tracer. During a 9 month period, 70 free level determinations were performed on 46 patients. These comprised 20% of all phenytoin assays. The median free phenytoin fraction was 13.6% (range 9.3-28.6%). While total phenytoin levels were below the normal optimum range in 61% cases, free levels were probably therapeutic or above in 70% cases. Dosage adjustments were recommended on the basis of the free level, and were followed more often when the doctor had requested the free level assay (P less than 0.05). The results suggest that a free phenytoin level assay can improve the usefulness of therapeutic drug monitoring, particularly when the doctor understands the purpose of the assay.

An audit of therapeutic drug monitoring procedures--use of theophylline assay services

Monitoring therapy involving drugs exhibiting high intersubject variation and/or narrow therapeutic index has become more generally accepted in hospitals. This paper describes an audit conducted jointly by clinical pharmacists and clinical biochemists into the use and therapeutic value of a drug monitoring service in a general hospital using theophylline as a model. Assay values were categorized as 'subtherapeutic', 'therapeutic' or 'potentially toxic'. The reporting procedures involving the two departments were evaluated along with action taken by the requesting clinicians. The study showed that 60% of the theophylline assay results fell within the therapeutic range at the time of sampling. However only 38% of samples were considered to have been taken under steady state conditions. There was a significant delay in relaying the results to the clinicians. Procedural changes involving sampling times, analytical techniques, recording and conveying results to clinicians and co-operative policies between the departments of pharmacy and clinical chemistry have been implemented as a result of this study.