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Biomedical subjects

M Stokes

Publications and source records attributed to M Stokes.

At least 37 records · Page 2Linked to original sources
PubMed1996

Premature failure of battery-powered syringe pumps.

Failure of battery-powered equipment during the interhospital transfer of patients is potentially life threatening. The time to failure of 60 fully-charged identical syringe pumps (20 from each batch purchased in 1992, 1994 and 1995) was measured. Older pumps were associated with less predictable charge capacity, with 40% of the 1992 pumps failing within 60 min. The premature failure of these pumps is most likely due to poor battery care. It is unsafe to assume that a fully-charged, battery-powered pump will continue to function throughout a long transfer. The routine carriage of spare pumps or a backup power supply is recommended.

Electric Power Supplies↗
PubMed1994

Audit of complete axillary dissection in early breast cancer.

The role of complete axillary dissection (CAD) in the management of breast cancer is controversial and largely unresolved. Acceptance of the results of trials incorporating CAD assumes that the axillary dissection is truly complete. To address this point, and also to define quality control criteria for this operation within our unit, we audited 100 consecutive axillary dissections as follows: the primary surgeon performed what he/she felt to be a thorough CAD and submitted separately the contents of level I, II and III for pathological evaluation; a second surgeon then independently assessed the dissection and arbitrarily labelled any further excised tissue as level IV. Level IV nodes were retrieved in 38% of cases. Tumour involvement of level IV nodes was noted in 5% (2/38) of dissections where lymph nodes were retrieved, but in neither instance was pathological staging altered. There was a significant decrease in the incidence of level IV node retrieval from 47% (28/60) in the first 6 months of audit to 20% (8/40) subsequently. This novel approach to our continuing audit identified quality control criteria for this procedure in our unit and suggested that audit of this kind benefits training.

Breast Neoplasms↗
PubMed1994

Evoked potential monitoring of the upper extremities during thoracic and lumbar spinal deformity surgery: a prospective study.

We prospectively investigated the usefulness of somatosensory evoked potential (SEP) monitoring to detect clinically significant peripheral nerve or brachial plexus compression in the upper extremities during spinal deformity surgery. All patients had bilateral median and ulnar nerve SEPs evaluated as a baseline, both intermittently throughout the surgical procedure and at termination of surgery. This information was correlated with pre- and postoperative upper extremity neurologic examinations. Twenty-five upper extremities in 21 patients had intraoperative SEP changes consisting of at least a 60% decline in amplitude or a 10% increase in latency. On many occasions, repositioning of the upper extremities improved the SEP responses to acceptable baselines. Overall, SEP monitoring of the upper extremities was 78% sensitive for detecting upper extremity sensory deficits, 100% sensitive for detecting combined sensory and motor deficits, and 98.5% specific for predicting normal postoperative upper extremity function. We recommend the simultaneous electrophysiologic monitoring of the upper and lower extremities during spinal surgery to allow identification of brachial plexus and/or peripheral nerve stretch/compression that may be amenable to intraoperative correction.

Adolescent↗
PubMed1992

High-performance liquid chromatographic monitoring of metabolic products resulting from the treatment of mouse hepatoma cells with N6-cycloalkylated nucleosides.

High-performance liquid chromatography was used to analyze cell lysates and growth medium of mouse hepatoma cells, separately treated with N6-cyclopropyl-, N6-cyclobutyl-, and N6-cyclopentyladenosines, in an effort to gain insight into the mechanism by which these modified nucleosides exert their cytotoxic effect(s). The corresponding 5'-monophosphate of the respective modified nucleoside was detected in the separate cell lysate samples. Both the modified nucleoside and its corresponding 5'-monophosphate were detected in the separate growth medium samples and their relative concentrations therein were determined. These results indicate that the cytotoxicity of these N6-cycloalkylated nucleosides may be attributed to their 5'-monophosphates within the cells.

Animals↗
PubMed1990

Reflex actions of knee joint afferents during contraction of the human quadriceps.

(1) The spinal reflex actions of afferents stimulated by knee joint distension have been investigated in man. (2) Cannulation of the knee and infusion of saline raised intra-articular pressure, especially during quadriceps contraction. High pressures did not induce any sensation of pain. Pressure was taken as an index of joint proprioceptor activation. (3) Increased pressure progressively depressed the quadriceps H-reflex, both at rest and during quadriceps contraction. There was no indication of a threshold pressure for this inhibitory action. (4) It is concluded that joint distension inhibits quadriceps motoneurons through spinal pathways that still operate during voluntary contraction. These pathways could thus contribute to pathological weakness after joint injury. (5) Joint distension produced spatial facilitation of non-reciprocal inhibition of quadriceps H-reflexes from afferents in the tibial nerve.

Adult↗
PubMed1989

Selenium metabolism and supplementation in patients with muscular dystrophy.

We studied selenium metabolism in patients with Duchenne muscular dystrophy and in contrast to previous reports found no significant abnormalities in these patients. Supplementation of muscular dystrophy patients and control subjects with sodium selenite (1 mg selenium/day) induced a variable rise in the activity of the selenium-dependent enzyme glutathione peroxidase in plasma and red cells, but no significant change in muscle glutathione peroxidase activities. There was no effect of selenium supplementation on disease activity in the patients with muscular dystrophy. Thiobarbituric acid-reacting substances (an index of free radical-mediated lipid peroxidation) were elevated in the muscle of patients with Duchenne muscular dystrophy in contrast to patients with other forms of muscular dystrophy and control subjects. This elevation was unaffected by selenium supplementation.

Clinical Trials as Topic↗
PubMed1987

Effects of joint pathology on muscle.

The muscle wasting associated with joint damage may be highly selective; knee disorders produce quadriceps wasting but little change in the size of the hamstrings. This causes isolated quadriceps weakness, so predisposing to a position of knee flexion. Nociceptors and other receptors in and around the joint can have flexor excitatory and extensor inhibitory actions. At the knee, these receptors are likely to excite hamstrings and inhibit quadriceps. Although other actions could occur, quadriceps inhibition may be favored by a position of knee extension. Quadriceps inhibition will weaken voluntary contraction, reduce tone, and contribute to wasting of the muscle, further predisposing to a position of knee flexion. The potency of quadriceps inhibition may be considerable, even in the absence of perceived pain. A small, apparently trivial effusion (or even a clinically undetectable effusion) may cause important inhibition. In order to improve the orthopedist's ability to prevent flexion contracture of the injured or operated joint, he must look not only for ways of reducing joint pain, but also for ways of preventing activity in other joint afferents. For example, he must consider the possible effects of joint position, intraarticular pressure, suture-line tension, and afferent blockade.

Animals↗
PubMed1985

Reflex inhibition of the quadriceps after meniscectomy: lack of association with pain.

We have examined the severity and duration of reflex inhibition of quadriceps activation after arthrotomy and meniscectomy, its relationship with pain, and the effect of local anaesthesia on this relationship. Fourteen men, on completion of medial meniscectomy by arthrotomy, received either 10 ml (B10 group) or 15 ml (B15 group) of 0.5% bupivacaine hydrochloride ('Marcaine Plain') into the knee, or no injection (control group). Reflex inhibition of quadriceps was measured as the percentage reduction, from the ipsilateral preoperative value, in the integrated surface electromyogram recorded during maximal voluntary isometric contractions with the knee in extension. Pain during each contraction was recorded on a linear analogue scale. Unoperated limbs showed no evidence of quadriceps inhibition. In the operated limbs, at 1-2 h post-operatively, controls had both severe inhibition (median = 62%) and severe pain on attempting a maximal quadriceps contraction. The B10 group had similar inhibition but less pain (P less than or equal to 0.005, Wilcoxon 2-sample, 1-tailed test). In the B15 group both inhibition (P less than or equal to 0.05) and pain (P less than or equal to 0.01) were less than in the controls. These effects of bupivacaine had been lost by 4-5 h post-operatively. At 3-4 days, inhibition was still severe (median = 75%) in all three groups of patients but pain was only mild or absent. At 10-15 days, median inhibition was still 35%, but there was little or no pain. We conclude that postmeniscectomy inhibition is not simply due to perceived pain but is due, at least in part, to stimuli from the knee.

Adult↗
PubMed1985

The size and strength of the quadriceps muscles of old and young men.

The mean isometric strength of the stronger quadriceps muscles of 12 healthy men in their seventies was 39% less than that of 12 healthy men in their twenties (P less than 0.001). The cross-sectional area of the quadriceps was measured at mid-thigh, by ultrasound scanning; the older men's stronger quadriceps were 25% smaller (P less than 0.001). The ratio of the stronger quadriceps' strength to its cross-sectional area was very similar in the old men to values obtained previously for both old and young women, but averaged 19% less than in the young men (P less than 0.02). Quadriceps size and strength were correlated in the old men (r = 0.77, P = 0.03) but not in the young men (r = 0.15). The principal axis of the relationship between quadriceps size and strength in the old men was very similar to those previously reported for both old and young women. The quadriceps strength of some young men is greater than would be expected from the size of the muscle.

Adult↗
PubMed1984

Hypophosphataemic osteomalacia and myopathy: studies with nuclear magnetic resonance spectroscopy.

A patient with familial adult-onset hypophosphataemia, whose myopathy was closely related to the plasma phosphate concentration, was investigated by phosphorus nuclear magnetic resonance spectroscopy (31P n.m.r.) in vivo of the right flexor digitorum superficialis muscle. During hypophosphataemia induced by stopping oral phosphate a significant reduction in measured muscle strength occurred, but the ratios of the intramyocellular levels of phosphocreatine (PCr), adenosine triphosphate (ATP) and inorganic phosphate (Pi) remained unchanged at rest. During exercise these levels changed, as did the intramyocellular pH, but they did not differ from the pattern previously recorded in normal subjects. In four adults with inherited infantile-onset hypophosphataemia (vitamin D-resistant rickets, VDRR) without myopathy, the n.m.r. measurements were normal at rest and during exercise. In one patient with inherited hyperphosphataemia (tumoral calcinosis) the resting PCr: Pi ratio was significantly reduced.

Adenosine Triphosphate↗
PubMed1984

Size and strength of the quadriceps muscles of old and young women.

Muscle weakness and wasting may be evaluated objectively by dynamometry and compound ultrasound imaging. We have measured the voluntary isometric strength of the quadriceps muscles of healthy women in their 70s (n = 25) and in their 20s (n = 25) and have compared it with the mid-thigh cross-sectional area of the same muscles. The two groups of women showed similar variability when strength was measured on consecutive days (coefficients of variation: 8%). The older women were 35% weaker than the young women (P less than 0.001) and their quadriceps cross-sectional area was 33% less (P less than 0.001). Quadriceps strength and cross-sectional area were correlated (r = 0.66, P less than 0.001, elderly; r = 0.53, P less than 0.01, young) and the principal axis of the relationship was closely similar for the two groups of women. There is therefore no difference in the intrinsic strength of the quadriceps muscles of healthy women in their third and eighth decades. This report also provides normative data for the objective evaluation of quadriceps weakness and/or wasting in female patients. The techniques involved are straightforward, the dynamometer is easily made, and compound ultrasound imaging is widely available.

Adult↗