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Biomedical subjects

J Watkins

Publications and source records attributed to J Watkins.

At least 127 records · Page 7Linked to original sources
PubMed1984

The systolic arterial pressure/end-systolic volume relationship in patients with severe left ventricular dysfunction.

Performance of the intact left ventricle is well-defined by the end-systolic pressure/end-systolic volume relationship that appears independent of preload and afterload. To determine whether noninvasive measurements of this relationship could distinguish normal from abnormal subjects, we evaluated the relationship between arterial systolic pressure (determined by cuff sphygnomanometry) and radionuclide estimates of end-systolic volume in 12 normal subjects and 24 patients with severe left ventricular dysfunction. Data were acquired at rest, after atropine injection, and then during at least three increments of arterial pressure (average total increase approximately 45 mm Hg) using phenylephrine. The relationship between peak-systolic pressure (SP) and end-systolic volume (ESV) was found to be linear in all subjects (r greater than or equal to 0.91). The slope of this line was steeper in normal subjects than in myopathic patients (73 +/- 21.7 vs 20.8 +/- 8.7 mm Hg/volume unit/m2, P less than 0.001) and the zero pressure intercept also was greater (49.8 +/- 30 mm Hg vs 27.1 +/- 44.2 mm Hg, P less than 0.01). Similarly, resting ejection fraction (EF) was greater in the normals (0.71 +/- 0.88 vs 0.21 +/- 0.07% P less than 0.001) and end-diastolic volume (EDV) was smaller (4.14 +/- 0.88 vs 6.58 +/- 0.65 volume units, P less than 0.01). Systolic pressure/end-systolic volume relationship determined by these noninvasive methods was linear in both patients with severely reduced cardiac function and normal control subjects, clearly distinguishing normal from severely impaired left ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Step tests of cardiorespiratory fitness suitable for mass testing.

Step tests have been widely used to assess cardiorespiratory fitness. Work rate is determined by step height and step frequency, whereas the total amount of work done depends upon the number and duration of work periods. In all step tests which are suitable for mass testing, performance is based on heart rate during recovery. A review of the literature strongly suggests that step tests can give reliable and valid measures of cardiorespiratory fitness provided that (a) the subjects have received adequate instruction and practice in taking the test prior to the criterion test performance, and (b) the work load is above a certain threshold.

Adolescent↗
PubMed1984

Late strut fracture in a Björk-Shiley valve prosthesis (current series).

Fracture of the short strut of the latest series of Björk-Shiley mitral valve prostheses occurred 12 months after implantation. The patient died despite emergency surgery to excise and replace the prosthesis. Björk-Shiley 29-33 mm valves with a 60 degree opening angle manufactured between February 1981 and March 1982 have a predicted strut fracture rate of 0.3% (three times greater than that of valves produced outside these dates). Unimplanted valves from this batch have now been recalled by the manufacturers.

Atrial Fibrillation↗
PubMed1983

Radionuclide evaluation of the systolic blood pressure/end-systolic volume relationship: response to pharmacologic agents in patients with coronary artery disease.

To assess the response of the relationship between systolic blood pressure and end-systolic volume to pharmacologic agents with known cardiac effects, we studied 21 patients with known coronary heart disease by means of gated radionuclide angiograms during the infusion of phenylephrine. Each individual was studied during the infusion of phenylephrine twice, once as a control and the second time after the administration of either intravenous dobutamine, topical nitroglycerin ointment, or intravenous propranolol. Eight individuals received 10 micrograms/kg/min of dobutamine, which reduced resting cardiac volumes (p less than 0.01), raised ejection fraction (p less than 0.01), and shifted the slope (1.38 +/- 0.50 to 2.03 +/- 0.69, p less than 0.01) and pressure intercept received 2 inches of nitroglycerin ointment. Nitroglycerin increased ejection fraction (p less than 0.05) and reduced volumes (p less than 0.05) but did not alter either the slope (1.46 +/- 0.68 to 1.49 +/- 0.61, p = NS) or intercept (10.6 +/- 5.4 to 10.1 +/- 6.4 mm Hg, p = NS) of the relationship. Eight patients received 15 mg of intravenous propranolol. Propranolol reduced resting ejection fraction (p less than 0.05), increased volumes (p less than 0.05), and reduced both the slope (1.67 +/- 0.58 to 1.51 +/- 0.53, p less than 0.05) and the intercept (13.8 +/- 2.5 to 7.5 +/- 2.3 mm Hg, p less than 0.05) of the pressure-volume relationship. Thus the systolic blood pressure/end-systolic volume relationship can be assessed from radionuclide angiograms.

Blood Pressure↗
PubMed1983

Etomidate: an 'immunologically safe' anaesthetic agent.

A review of the important aspects of immunity and its disturbance by drugs is given, together with a resumé of the various immunological pathways involved in adverse anaesthetic reactions. Etomidate is unique amongst anaesthetic drugs in that it does not release plasma histamine. Between 1978 and 1982, five cases of possible reactions involving the use of etomidate were investigated. All involved only immediate widespread cutaneous flushing or urticaria, which was followed in two cases by extensive perioperative vomiting. The direct involvement of etomidate was uncertain. In 1982 two further cases were investigated which also involved hypotension. In both, suxamethonium and/or alcuronium had been used. The first case was repeated uneventfully when etomidate was used with pancuronium. The second case is as yet unresolved but the reaction was again probably caused by the muscle relaxants. The absence of severe reactions, and particularly cardiovascular effects, to etomidate leads the author to recommend its use in high risk patients, such as those with allergy or atopy and in those who have previously exhibited severe anaphylactoid responses.

Adult↗
PubMed1983

Physical working capacity and mile run performance in adolescent boys.

The degree of generality between the endurance characteristics of the one mile run and PWC170 tests was examined with a group of fifteen year old boys who performed both tests once a week for three weeks. A significant improvement in performance of both tests was found between trials 1 and 2, which was sustained between trials 2 and 3. These results suggest that norm scales regarding performance in both tests should be based on the average of at least two trials following a practice trial. The results of the present study also suggest that when average scores are used, rather than single scores, the amount of generality between the endurance characteristics of the one mile run and PWC170 test is high enough to allow physical working capacity to be predicted fairly accurately from performance in the one mile run.

Adolescent↗
PubMed1983

Aging attitudes to home accidents.

Twenty-six people over the age of 65 living in Exeter and Seaton (Devon) were interviewed to determine their attitudes to prevention of home accidents. All had positive attitudes to accepting advice. The majority preferred a familiar person to give the advice.

Accidents, Home↗
PubMed1982

Immunological and non-immunological mechanisms involved in adverse reactions to drugs.

This communication reviews the mechanisms involved in anaphylactic and anaphylactoid reactions to intravenous drugs used in anaesthesia. Although the mechanisms involved are pertinent to other drugs and substances used in clinical practice, the use of the intravenous route makes this a particularly worrying problem in anaesthetic practice. Despite the similarity of the clinical manifestations to those expected from immediate immunological hypersensitivity (anaphylaxis), relatively few reactions involve antibodies. Instead, a variety of mechanisms occur where activation of the blood inflammatory response systems, particularly complement, may be either primary or secondary to activation of the coagulation or fibrinolytic cascades of the blood clotting mechanisms. Immediate anaphylactoid reactions, manifest in the release of vasoactive substances such as histamine, may therefore pose very minor problems compared with coagulation problems arising in the peri- and post-operative period. It is important to discover the mechanism of all adverse reactions not only if these are to be avoided in the reactants in the future but also because of the necessity for devising suitable prophylactic and therapeutic measures for general use. The practical problems of such investigations are explored with particular reference to the laboratory investigation of subclinical reactions in terms of plasma histamine release and changes in blood leucocyte distribution.

Adult↗
PubMed1982

[The practical assessment of complement involvement in anaphylactoid reactions].

While no single test is entirely satisfactory for the investigation of anaphylactoid response to intravenous anaesthetic drugs, changes in plasma chemistry are particularly easy to measure and may be carried out at centres remote from the clinical incident. Analysis should be carried out on a sequence of blood samples taken into EDTA over the 24 hours following such reaction. Few reactions are classical Type I, IgE antibody mediated, reactions and most involved the complement proteins in some specific manner. By measuring changes in the levels and activity of the complement proteins, particularly C3, C4 and C5, between samples, it is possible to deduce the likely mechanism of a reaction and thus to advise more wisely on future treatment of the patient. Although levels of any plasma protein may be readily measured by single radial immunodiffusion (Mancini technique) using appropriate specific antisera, one assessment of complement activity (degree of conversion) has until now largely been restricted to technically exacting Laurell immunoelectrophoresis. Two simple immunoelectrophoretic techniques are described here which do not require such expertise.

Anaphylaxis↗