Biomedical subjects

H Wastell

Publications and source records attributed to H Wastell.

4 recordsLinked to original sources

PubMed2007

A study to determine the minimum volume of blood necessary to be discarded from a central venous catheter before a valid sample is obtained in children with cancer.

BACKGROUND: The objective of this study was to determine the minimum volume of blood that should be discarded from a range of different types of central venous catheter (CVC), such that the subsequent blood sample was not diluted or contaminated by the residual intra-luminal fluid. PROCEDURE: Seventy children aged 1-19 years with central venous access inserted as part of their standard clinical treatment were recruited to this prospective study. Statistical comparison of the extent of variation in biochemical and haematological parameters observed between two blood samples taken following routine 5 ml discard blood volumes, as compared to the extent of variation between samples drawn following a 5 ml discard volume and <5 ml volumes, was carried out. RESULTS: Data indicate that the measurement error in a clinical sample obtained following a 3 ml discard volume is no different to the measurement error obtained when using a standard 5 ml discard volume. Comparable results were obtained from patients with various different types of CVC or portacath access. CONCLUSIONS: The withdrawal of a 3 ml discard volume is sufficient to ensure that the subsequent blood sample is not diluted or contaminated by residual intra-luminal fluid. This may have a significant clinical impact in paediatric oncology, where patients frequently require blood transfusions due to the haematological toxicities associated with chemotherapy. It is hoped that these results will impact on hospital policies concerning specified discard volumes taken from CVCs prior to the withdrawal of blood samples for research purposes and routine clinical analysis.

Adolescent↗

PubMed1999

An investigation into the need for supplementary steroids in organ transplant patients undergoing gingival surgery. A double-blind, split-mouth, cross-over study.

Organ transplant patients are frequently medicated with triple immunosuppressive therapy that includes both cyclosporin and the corticosteroid, prednisolone. Many of these patients experience gingival overgrowth that necessitates surgical intervention. Chronic dosing with corticosteroids can lead to suppression of the hypothalamic-pituitary axis, and subsequent adrenocortical suppression. To circumvent possible suppression, supplementary steroids are administered to such patients prior to so-called "stressful events". We have examined the need for supplementary steroids in 20 organ transplant patients undergoing gingival surgery under local anaesthesia to correct their drug-induced gingival overgrowth. All patients were operated upon in the first half of the morning. Prior to gingival surgery, resting blood pressure (BP) and serum ACTH concentrations were determined. Immediately before surgery patients received either intravenous hydrocortisone 100 mg or placebo in random, double-blind order. Each patient required 2 gingivectomies and thus acted as their own placebo control. BP was measured at various time points throughout surgery and upto 2 h postoperatively. On completion of surgery, a further blood sample was taken to determine ACTH concentration. There was no significant difference (p>0.05) between placebo and hydrocortisone treatments for BP and ACTH measurements. No patient experienced any symptoms that were suggestive of adrenocortical suppression. One patient did experience postural hypotension prior to gingival surgery, but this is attributed to his antidepressant medication. We can conclude from this study that immunosuppressed organ transplant patients taking the maintenance dose of prednisolone (5-10 mg/day) do not require corticosteroid cover prior to gingival surgery under local anaesthesia. We would however, advocate monitoring of their blood pressure throughout the procedure.

Adrenocorticotropic Hormone↗

PubMed1985

Enzyme studies in biotin-responsive disorders.

There appear to be at least two underlying aetiologies for combined carboxylase deficiency; firstly, a failure of biotinylation of apocarboxylases due to a mutation of holocarboxylase synthetase (EC 6.3.4.10) which results in an enzyme with a high Km with respect to biotin and secondly, a failure of biotinylation due to a lowered availability of biotin due to biotinidase deficiency (EC 3.5.1.12). In both these disorders secondary defects of all four biotin-dependent carboxylases result which in turn causes the excretion of the metabolites characteristic of the isolated carboxylase deficiencies. In addition, both disorders respond biochemically and clinically to the administration of large amounts of biotin.

Acetyl-CoA Carboxylase↗

PubMed1984

A sensitive fluorimetric rate assay for biotinidase using a new derivative of biotin, biotinyl-6-aminoquinoline.

The previously reported method for the estimation of biotinidase (EC 3.5.1.12) is an endpoint colorimetric assay based on the hydrolysis of biotinyl-4-aminobenzoate, followed by diazotization, and is not suitable for our studies of biotinidase. A fluorimetric rate assay of biotinidase which uses a newly synthesized derivative biotinyl-6-aminoquinoline is described here.

Amidohydrolases↗