St Thomas' Hospital

About: St Thomas' Hospital is a healthcare organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Pregnancy. The organization has 12105 authors who have published 15596 publications receiving 624309 citations. The organization is also known as: St Thomas's Hospital & St. Thomas's.

ABC of oxygen: Assessing and interpreting arterial blood gases and acid-base balance

Abstract: One of the main factors determining oxygen delivery to cells is the oxygen content of the blood. Blood gas tensions are measured by direct blood sampling or transcutaneous diffusion and oxygen saturation of haemoglobin from pulse oximetry. Arterial blood gas analysis is widely available in hospitals and the direct measurements (pH, PaO2, paCO2) are among the most precise in medicine. The value of such measurements, however, depends on the ability of doctors to interpret the results properly. Taking arterial blood sample Arterial puncture may result in spasm, intraluminal clotting, or bleeding and haematoma formation, as well as a transient obstruction of blood flow. These factors may decrease the arterial flow in distal tissues unless adequate collateral arterial vessels are available. The brachial and femoral arteries do not have adequate collateral supplies. The radial artery at the wrist is the best site for obtaining an arterial sample because it is near the surface, relatively easy to palpate and stabilise, and usually has good collateral supply from the ulnar arteries. This can be confirmed by a modified Allen's test. ### Problems of taking arterial blood samples Allen's test. The radial and ulnar arteries are occluded by firm pressure while the fist is clenched. The hand is opened and the arteries released one at a time to check their ability to return blood flow to the hand It is kinder to patients to use local anaesthesia over the radial artery before puncture. Analgesic patches can be used for children. Use a 20 or 21 gauge needle with a preheparinised syringe. Express the heparin from the syringe before taking the sample; adequate heparin will remain in the 0.2 ml dead space of the barrel and needle. At least 3 ml of blood is required to avoid a dilution effect from the heparin. Any sample with more than fine …

Glycopeptide tolerance in Staphylococcus aureus.

Abstract: Treatment failures with vancomycin prompted us to investigate the phenomenon of tolerance to glycopeptides in recent clinical isolates of Staphylococcus aureus. We used both MBC/MIC determinations and time-kill measurements to study tolerance to vancomycin and teicoplanin in 35 blood or heart valve isolates of S. aureus from patients with endocarditis or bacteraemia. There was generally good agreement between vancomycin tolerance indicated by an MBC:MIC ratio of > or =32 and by < or =90% kill after 6 h incubation in the presence of 20 mg/L vancomycin. However, two isolates were tolerant according to their MBC:MIC ratios but non-tolerant as judged by time-kill measurements. Seven of 15 methicillin-resistant S. aureus (MRSA) isolates but only two of 20 methicillin-susceptible ones were tolerant as judged by time-kill experiments (chi2 = 4.27 with Yates' correction, P = 0.04). Seven of the 16 isolates from patients with endocarditis were tolerant, compared with only two of the 19 isolates from patients with other conditions (chi2 = 3.43 with Yates' correction, P = 0.06). Within the endocarditis and non-endocarditis subgroups, tolerance was associated more frequently with methicillin resistance than with susceptibility, but the numbers were too small for the differences to be statistically significant. Most of the vancomycin-tolerant isolates were also tolerant to teicoplanin. We conclude that glycopeptide tolerance is a real phenomenon in S. aureus, particularly amongst MRSA isolates, and can be reliably determined by our method of time-kill analysis. Tolerance may compromise glycopeptide therapy of serious S. aureus infection and should be taken into account when deciding treatment.

Cardiovascular effects of growth hormone treatment in growth-hormone-deficient adults: stimulation of the renin-aldosterone system

Abstract: 1. In adult humans with growth hormone deficiency, treatment with growth hormone has recently been shown to have major anabolic effects and to improve exercise performance. The cardiovascular effects of growth hormone in adults with growth hormone deficiency were examined in 24 patients treated with recombinant human growth hormone (0.07 units/kg at night) in a double-blind, placebo-controlled trial lasting 6 months. 2. Compared with placebo, resting M-mode echocardiography showed increases in left ventricular end-diastolic dimension and stroke volume in the group treated with recombinant human growth hormone. No differences were noted between the groups with respect to left ventricular end-systolic dimension, fractional shortening, wall thicknesses or mean arterial blood pressure. Left ventricular myocardial mass increased in the group given recombinant human growth hormone. 3. The supine plasma renin activity was increased and remained elevated over the 6 months, whereas the plasma aldosterone concentration was unchanged, after treatment with recombinant human growth hormone. Clinical signs of sodium retention were evident during the first 3 months of treatment with recombinant human growth hormone. 4. We conclude that treatment with recombinant human growth hormone in adults with growth hormone deficiency resulted in small increases in left ventricular pre-load, due to the sodium-retaining action of growth hormone. Activation of the renin-aldosterone system was involved in such changes. Myocardial hypertrophy was observed without changes in mean arterial pressure, reflecting the anabolic action of growth hormone.

Chronic Urticaria: Recent Advances

Abstract: Chronic urticaria is an umbrella term, which encompasses physical urticarias, chronic “idiopathic” urticaria and urticarial vasculitis. It is important to recognize patients with physical urticarias as the investigation and treatment differs in important ways from patients with idiopathic chronic urticaria or urticarial vasculitis. Although relatively uncommon, urticarial vasculitis is an important diagnosis to make and requires histological confirmation by biopsy. Underlying systemic disease and systemic involvement, especially of the kidneys, should be sought. It is now recognized that chronic “idiopathic” urticaria includes a subset with an autoimmune basis caused by circulating autoantibodies against the high affinity IgE receptor (FceR1) and less commonly against IgE. Although the autologous serum skin test has been proven useful in prompting search for and characterization of circulating wheal-producing factors in chronic urticaria, its specificity as a screening test for presence of functional anti-FceR1 is low, and confirmation by demonstration of histamine-releasing activity in the patient’s serum must be the benchmark test in establishing this diagnosis. Improved screening tests are being sought; for example, ability of the chronic urticaria patient’s serum to evoke expression of CD 203c on donor human basophils is showing some promise. The strong association between autoimmune thyroid disease and autoimmune urticaria is also an area of ongoing research. Drug treatment continues to be centered on the H1 antihistamines, and the newer second-generation compounds appear to be safe and effective even in off-label dosage. Use of systemic steroids should be confined to special circumstances such as tapering regimens for acute flare-ups. Use of leukotriene antagonists is becoming popular, but the evidence for efficacy is conflicting. Cyclosporin is also effective and can be used in selected cases of autoimmune urticaria, and it is also effective in non-autoimmune cases, although less so.