Antihypertensive therapy and circadian blood pressure profiles: a retrospective analysis utilising cumulative sums

The results of previous studies on the effects of antihypertensive agents on circadian blood pressure patterns are inconclusive, possibly due to the lack of a simple, objective, universally accepted method of quantifying circadian blood pressure profiles. In order to investigate for differences in the effects of antihypertensive drugs on circadian changes we utilised a recently described modified cumulative sums technique to quantify circadian alteration magnitude (CAM). CAM is simply calculated as the difference between crest and trough blood pressures, the mean blood pressures of the 6-h periods of highest and lowest sustained pressures respectively. The records from all 24-h ambulatory blood pressure monitoring performed over a 7 year period on subjects either on no medication (1208), or on treatment with a single first-line antihypertensive agent (578), were examined retrospectively. A sample (n = 40) stratified for trough diastolic blood pressure, age and sex was randomly selected from each of the following 5 groups: subjects on no medication, and subjects being treated with bendrofluazide, atenolol, class 2 calcium-channel blockers or captopril alone. Untreated subjects, those on bendrofluazide and those on a class 2 calcium channel blocker had similar circadian patterns. Subjects on atenolol therapy (25.9 +/- 1.7/18.3 +/- 1.3, systolic CAM +/- SE/diastolic CAM +/- SE) had attenuated circadian changes (p < 0.05) when compared to the untreated group (29.8 +/- 1.8/23.6 +/- 1.1), while those on captopril (34.9 +/- 2.4/25.7 +/- 1.8) exhibited markedly increased systolic and diastolic circadian blood pressure swings, which differed from those of the atenolol treated group (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The diurnal blood pressure profile. A population study

This population study included 399 subjects, of whom 370 (93%) showed a significant diurnal blood pressure (BP) rhythm. The nocturnal BP fall was normally distributed and averaged 16 +/- 9 mm Hg systolic and 14 +/- 7 mm Hg diastolic (mean +/- SD). The amplitude of the diurnal BP curve followed a positively skewed distribution, with a mean of 16 +/- 5 mm Hg for systolic BP and 14 +/- 4 mm Hg for diastolic BP. The daily BP maximum occurred at 15:54 +/- 4:47 for systolic BP and at 15:11 +/- 4:20 for diastolic BP. Thirty-four subjects were reexamined after a median interval of 350 days. The test for the presence of a significant diurnal rhythm was discordant in only two subjects. Repeatability (twice the standard deviation of the differences between paired recordings expressed as a percentage of the mean) varied from 11 to 25% for the 24 h, daytime, and overnight BP, and from 76 to 138% for the parameters describing the diurnal BP rhythm. In nine subjects with an initial night/day ratio of mean BP less than 0.78, the nighttime BP was significantly increased at the repeat examination, whereas the opposite tendency was observed in nine subjects with an initial ratio greater than 0.87. In conclusion, the distribution of the nocturnal BP fall is unimodal. The reproducibility of the ambulatory BP is satisfactory for the level of BP and for the presence of a diurnal BP rhythm, but not for the parameters of the diurnal BP curve. Thus, one 24 h recording is insufficient to fully characterize an individual's diurnal BP profile.

Collaboration in nursing education

The process of development of a collaborative link between the United Midlands College for Nursing and Midwifery and Coventry Polytechnic is described. The process, which began early in 1990, has already brought benefits for the staff and students of both institutions. Evaluation of the arrangement will be ongoing, and will take into account national and regional developments in funding and organising nursing and midwifery education.

Algorithm for patient management of acute manic states: lithium, valproate, or carbamazepine?

Lithium remains the mainstay of pharmacologic therapy for the majority of patients with bipolar disorder; however, significant numbers of patients with both classical bipolar disorder and syndromal variants fail to respond to lithium therapy. The discussion that follows outlines subgroups of patients who are likely to be nonresponsive to or have poor tolerance for lithium therapy either because of disease type (rapid cyclers and schizoaffectives) or patient characteristics (the elderly or those with psoriasis or organic brain syndrome). Alternate therapy with valproate and carbamazepine is discussed. The relative efficacy of lithium versus valproate is briefly evaluated through a retrospective review of current case material. Algorithms for patient management are presented based on experience in our center for mood disorders. Valproate and carbamazepine were found to have an important clinical role for the treatment of bipolar spectrum disorders with the initial preference for treatment based on broad clinical phenomena.

Cumulative sums in quantifying circadian blood pressure patterns

The plotting of cumulative sums (cusums), a technique of proven value in the detection of trends in data collected at intervals of time, may be modified to analyze circadian blood pressure patterns quantitatively. Mean 24-hour ambulatory blood pressure is taken as the reference value and is subtracted from each pressure value. The products of the remainders and the corresponding time intervals are summed in sequence and are plotted against time to form a modified cusum plot. The slope of the plot over any given time period equals the difference between mean blood pressure during that period and mean 24-hour blood pressure. Crest and trough blood pressures (the mean blood pressures of the 6-hour periods of highest and lowest pressures) may be identified as the 6-hour periods where plot slopes are most steeply ascending and descending, respectively. The magnitude of the circadian blood pressure change, defined as the difference between crest and trough blood pressure, is calculated from the difference between crest and trough plot slopes. The height of the cusum plot, which reflects pressure alteration extent and duration, may also be used as a measure of circadian pattern. The modified cusums technique and cusum-derived statistics are illustrated using ambulatory blood pressure profiles of hypothetical and actual hypertensive subjects. Independence from fixed time periods improves precision and reproducibility. Cusum-derived statistics are simply calculated from raw ambulatory data and should prove useful in the quantitative analysis of circadian blood pressure profiles.

Ambulatory blood pressure monitoring in the evaluation of drug efficacy

Conventional clinic measurement of blood pressure is influenced by many factors that make the technique unsuitable for the assessment of antihypertensive drug efficacy. The major drawback of conventional measurement is that it cannot indicate the duration of drug effect or the influence of antihypertensive drugs on nocturnal blood pressure. Noninvasive 24-hour ambulatory blood pressure measurement has a number of advantages over conventional measurement: it provides a profile of blood pressure over the 24-hour period; it detects white coat responders; it is free of regression to the mean and the placebo response, thereby making it possible to consider efficacy studies which need not have a placebo phase; it enables considerably more observations than is possible with clinic measurement by increasing the power of studies, which may reduce significantly the numbers of patients needed for antihypertensive drug studies. Twenty-four-hour ambulatory blood pressure measurement offers the opportunity to study antihypertensive drugs in fewer patients with greater accuracy than is possible with conventional clinic measurement and should be a mandatory requirement for such studies.

Improved treatment results for lymphoblastic lymphoma in adolescents and adults using a doxorubicin-based (APO) protocol

A multi-drug chemotherapy (APO) protocol incorporating doxorubicin was used to treat 12 patients (median age 19 years) with lymphoblastic lymphoma. The APO protocol consisted of intensive induction and consolidation phases, prophylactic CNS treatment, and 24 months of maintenance therapy. Eleven patients had an anterior mediastinal mass, while T cell markers were found on the lymphoma cells in eight of the nine cases tested. Two patients had initial CNS involvement, with one also having bone marrow replacement. Complete remission was obtained in all patients, with no deaths due to treatment toxicity. There have been four relapses, one in the patient with initial CNS and leukemic disease, two in abdominal sites, and in the mediastinum in one patient. With a median follow-up time of 30 months from diagnosis, 67% of patients remain alive in first remission. These results indicate that the APO protocol provides a highly effective approach to the management of this high grade lymphoma in adolescents and adults.

Rapid viral diagnosis of acute respiratory infections: comparison of enzyme-linked immunosorbent assay and the immunofluorescence technique for detection of viral antigens in nasopharyngeal secretions

Nasopharyngeal secretions from adults and children were obtained in Stockholm, Sweden, for routine diagnosis of influenza A virus, influenza B virus, respiratory syncytial (RS) virus, parainfluenza type 3 virus, and adenovirus infections by demonstration of viral antigens directly in the specimens. The cells in nasopharyngeal secretions were pelleted by centrifugation for preparation of cell deposits for diagnosis by the immunofluorescence technique (IF) in London, England, and in Stockholm, whereas the supernatants were used to diagnose infection by the enzyme-linked immunosorbent assay (ELISA) in Stockholm. Titrations of the various purified viruses showed that ELISA could detect viral antigens in amounts corresponding to 1 to 10 ng of virus protein per test well. In a series of 73 specimens tested for influenza A, RS, and parainfluenza type 3 viruses by IF in London and by ELISA in Stockholm, 15 of 18 RS, 14 of 15 influenza A, and 2 of 2 parainfluenza type 3 viral infections were diagnosed by ELISA as compared with IF, giving sensitivities for RS and influenza A viral diagnosis of 83 and 93%, respectively, and a specificity of 100%. In another series of specimens from 35 patients tested for influenza B virus and adenovirus, five influenza B virus and four adenovirus infections were diagnosed by both methods; one additional influenza B infection was detected only by IF and another only by ELISA. Comparisons of diagnostic results between the two methods performed in Stockholm gave nonagreement of results for 37 of 1,593 tests (2.5%) for the five viruses. The conclusion reached was that the described ELISA, although a satisfactory test, had somewhat less sensitivity than did IF for the detection of respiratory viral infections. This could possibly be explained by unnecessary dilutions of specimens at the time of collection; transportation, processing, and storage of specimens were less complicated than for IF.

Clavulanate-potentiated amoxycillin: activity in vitro and bioavailability in the dog

Clavulanic acid is an inhibitor of beta-lactamase (penicillinase) and when used with amoxycillin the resulting combination becomes active against most bacteria resistant to amoxycillin through production of beta-lactamase. A total of 551 bacterial isolates from dogs and cats were examined by disc sensitivity testing, which showed that there was amoxycillin resistance particularly among staphylococci (50 per cent), Klebsiella species (97 per cent) and Escherichia coli (28 per cent). A combination of potassium clavulanate and amoxycillin reduced the incidence of resistance to 0.3, 3 and 7 per cent, respectively. Minimum inhibitory concentrations were determined for a number of the isolates and showed marked reductions in the presence of potassium clavulanate. A formulation containing amoxycillin trihydrate and potassium clavulanate (4:1) was dosed to beagles at 12.5 mg/kg. Concentrations of the drugs in blood, tissue fluid and skin showed that both drugs were sufficiently well absorbed and distributed to allow a prediction of efficacy against infections caused by beta-lactamase producing bacteria.

Is laterally-situated ectopic thyroid tissue always malignant?

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Absorption in calves of amoxicillin, ampicillin, and oxytetracycline given in milk replacer, water, or an oral rehydration formulation

Oxytetracycline, amoxicillin or ampicillin suspended in milk replacer, water, or a glucose-glycine-electrolyte solution (GGES) was orally given to calves (n = 64). Oxytetracycline suspended in milk replacer gave lower relative bioavailability than when suspended in water (P less than 0.01) or in GGES (P less than 0.001). Seemingly, the 63% binding (only partly reversible) of oxytetracycline suspended in milk replacer was responsible for low serum concentrations, whereas the greater water absorption from the GGES was responsible for improved uptake of antibiotic. Amoxicillin suspended in milk replacer had a delayed absorption, compared with that suspended in water, but the relative bioavailabilities from milk replacer and water were similar. In contrast, peak serum concentration and bioavailability were higher (P less than 0.05) when amoxicillin was suspended in GGES than when suspended in water. Binding of amoxicillin with milk replacer was comparatively low (16%) and was reversible. Ampicillin suspended in GGES gave a higher peak serum concentration (P less than 0.05) than when suspended in milk replacer. It, therefore, appeared that these antibiotics were more bioavailable when suspended in GGES than when suspended in water or especially in milk replacer. Oxytetracycline was bound particularly strongly to milk replacer.

Learned helplessness and the detection of contingency: a direct test

Two studies tested a basic hypothesis of the learned helplessness model: That performance deficits associated with exposure to uncontrollable outcomes are directly mediated by an individual's perception of response-outcome independence. In the first experiment 48 subjects were exposed to noise bursts. For one experimental group, the termination of the noise was response-contingent. For five other groups, noise-burst termination was independent of subjects' responses. These five groups varied in the number of trials on which they received positive feedback: As predicted, subjects over-estimated the amount of control they had over noise termination as a positive linear function of the amount of noncontingent positive feedback they received. Although subjects exposed to either noncontingent positive or negative feedback showed subsequent performance deficits on an anagrams task, the expected relation between perceived control and subsequent performance failed to emerge. These findings were replicated in a second experiment. In addition, subjects' locus, stability, and globality attributions failed to predict subsequent performance. These results call into question the central premises of helplessness theory: That perceived uncontrollability and causal attributions mediate learned helplessness.

Adenosine deaminase activity in lymphoid subpopulations and leukemias

Adenosine deaminase has been measured by the indirect spectrophotometric method in lymphoblasts from adult and pediatric lymphoblastic leukemias, peripheral T- and B-cells, mature T-cell leukemia (Sézary cell), and mitogen-stimulated peripheral control T- and B-cells. It was found that, if the specific activity of the enzyme is expressed in terms of cell cytoplasmic protein concentration rather than cell number, null-cell leukemia has enzyme levels markedly higher than T-cell lymphoblastic leukemic or Sézary cells. The range in values is far less than those reported by other authors using the direct spectrophotometric assay and cell number prior to lysis. Non-leukemic T- and B-cells from control individuals show minor differences as do T gamma-enriched cells. Lymphocytes from female oriental control populations were significantly lower. Both mitogen-stimulated lymphoblasts and control lymphocytes show similar elevations in adenosine deaminase activity so that no effect per se can be ascribed to lymphoblastic transformation.