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Biomedical subjects

A J Mearns

Publications and source records attributed to A J Mearns.

At least 19 recordsLinked to original sources
PubMed1992

Periodic posture stimulation of the baroreceptors and the local vasomotor reflexes.

In a supine subject, lowering of the foot from heart level to 50 cm below is known to stimulate the local reflex response and the baroreceptor outflow. We lowered and raised the leg of a supine subject periodically, with the leg stationary between movements (square wave). The Traube-Hering-Mayer wave (THM congruent to 0.1 Hz) was captured by or locked on to the leg movement over a certain frequency range, this is usually called the entrainment range. Square wave periodic leg movement in this manner on 10 male subjects, mean age 22 years, demonstrated that the THM frequency can be entrained. The lower limit of the entrainment bandwidth is 0.0841 (SD 0.0030) Hz and the upper limit is 0.1176 (SD 0.0013) Hz. Further examination showed that this phenomenon is independent of the breathing input. Comparison with the Traube-Hering-Mayer entrainment techniques of breathing and periodic neck suction using the Eckberg collar which stimulates the baroreceptors showed similar results. This work supports the hypothesis that the local reflex response and the baroreceptor outflow entrain the THM frequency.

Adult↗
PubMed1991

Reversed-phase and chiral high-performance liquid chromatographic assay of bupivacaine and its enantiomers in clinical samples after continuous extraplural infusion.

A previously unreported coupled achiral-chiral high-performance liquid chromatographic method has been developed to assay the levels of bupivacaine and its enantiomers in plasma samples, after the local anaesthetic had been given as a continuous extrapleural intercostal nerve block for 4 days, to relieve postoperative pain following thoracotomy. The method has been used to determine maximum, individual enantiomer and steady state levels in conjunction with an assessment of whether accumulation of bupivacaine occurs. An off-line extraction sample preparation is involved before determination of the "total" levels and final sample clean-up on a cyanopropyl silica column prior to "heart cutting" of the bupivacaine peak to a Chiral-AGP column for assay of the enantiomeric ratio. For an initial 5 patient number the mean maximum level was 5.43 micrograms/ml against a reported toxic level of around 5 micrograms/ml, which was reached in 72 h and the S-enantiomer gave slightly increased concentrations over the R-enantiomer for which there is some evidence of higher toxicity.

Adult↗
PubMed1991

Quantitative measurement of sympathetic neuropathy in patients with diabetes mellitus.

Vasoconstriction occurs in the skin capillary blood flow of the healthy subject when posture changes from supine to standing. Using frequency analysis of the optical photoplethysmograph signal, a statistically significant difference (P less than 0.01) may be demonstrated between supine and standing positions in the lower frequency band (0.01-0.5 Hz) in the foot of normal subjects. This allowed us to develop a simple index: sympathetic power band change (SPBC). Patients with diabetes mellitus often suffer from degeneration in the sympathetic nervous system. This impairs the normal vasoconstrictor response to standing. We have applied the SPBC 'blind' to a group of diabetic patients. Such patients may be divided into three groups according to their SPBC indices: normals with SPBC greater than 2.6 (group A), intermediates with 2.6 greater than or equal to SPBC greater than or equal to 0.26 (group B) and poor with SPBC less than 0.26 (group C). All patients with retinopathy were in group C and five out of the six patients with electrophysiologically confirmed peripheral neuropathy were in group C. Frequency analysis of the photoplethysmograph signal has produced an index of sympathetic tone change when subjects move from supine to standing position. The application of this index to patients with diabetes mellitus shows some patients to have sympathetic vascular tone failure.

Adult↗
PubMed1991

Continuous extrapleural intercostal nerve block after pleurectomy.

A randomised, double blind trial was carried out in 16 patients undergoing pleurectomy to assess the effect of continuous extrapleural intercostal block on postoperative pain and pulmonary function. Subjective pain relief was assessed on a linear visual analogue scale. Pulmonary function was measured on the day before operation and daily for five days after surgery. Eight patients received bupivacaine and eight placebo (saline). The mean pain scores at 4, 8, 16, and 24 hours were 13.3, 8.5, 6.1, and 10 mm respectively in the bupivacaine group compared with 56.3, 41, 46.7, and 35 in the control group; in addition, the bupivacaine group required less papaveretum. Twenty four hours after surgery mean values of peak expiratory flow, forced expiratory volume in one second, and forced vital capacity were reduced to 82%, 76%, and 76% of preoperative control values in the bupivacaine group, and to 39%, 32%, and 36% in the control group. The speed of recovery of pulmonary function was superior in the bupivacaine group. There were no complications related to the infusion. Continuous extrapleural intercostal nerve blockade with bupivacaine provides safe and effective postoperative analgesia and improves respiratory mechanics after pleurectomy.

Adolescent↗
PubMed1991

Fine needle aspiration biopsy of pulmonary lesions: a 2-year experience in a district general hospital with a literature review.

During the 2 years of 1987 and 1988, 74 patients with suspected malignant lung lesions underwent fine needle aspiration biopsy at the Bradford Royal Infirmary. Using a 20Fr needle, sufficient specimen (smear and clot) was obtained in 70 (95%) patients for histological examination. The indications for the procedure were: failure to make a diagnosis at bronchoscopy and bronchial lavage in 32 (43%) patients, peripherally located lesion in 28 (38%) patients, poor anaesthetic risk in 20 (27%) patients, negative bronchoscopy and mediastinostomy in five (7%) patients and three (4%) patients refused operative intervention. There were no deaths and complications were few. Seven patients developed pneumothorax, three of whom required intercostal drainage. Transient haemorrhage as shown by haemoptysis occurred in one patient and one patient complained of pleuritic chest pain. Of the 60 patients with malignant disease eventually proven, 50 were diagnosed correctly. The overall sensitivity and specificity of the test were 81 and 100% respectively based on histological and/or clinical outcome of the lung lesion. The test was cost-effective, diagnostic yield was high and complications were few. The use of fine needle aspiration biopsy as part of the management policy in peripheral lung lesions is realistic in a district general hospital.

Adult↗
PubMed1990

Efficacy of continuous extrapleural intercostal nerve block on post-thoracotomy pain and pulmonary mechanics.

To assess the efficacy of continuous extrapleural intercostal nerve block on postoperative pain and pulmonary function, a prospective, randomized, double-blind, placebo-controlled trial was conducted on 56 patients undergoing elective thoracotomy. Infusion was started before closing the chest and was continued for 5 days. Subjective pain relief was assessed on a linear visual analogue scale. Pulmonary function was measured on the day before operation and daily for 5 days. There were 29 patients in a group which received bupivacaine and 27 in a control group which received saline. The bupivacaine group had lower pain scores (P less than 0.01) and required less papaveretum (P less than 0.01) than the control group. Forced vital capacity, forced expiratory volume in 1 s and peak expiratory flow rate were maximally reduced at 24 h to median values of 56, 60 and 57 per cent, respectively, of preoperative control values in the bupivacaine group, and to 25, 30 and 32 per cent in the control group. These differences are highly significant (P less than 0.01). Restoration of pulmonary function was superior in the bupivacaine group (P less than 0.01). There were no infusion-related complications. After thoracotomy, continuous intercostal blockade with bupivacaine is a safe and effective method of pain relief which reduces the early loss of postoperative pulmonary function significantly and more rapidly restores respiratory mechanics.

Adult↗
PubMed1990

Pulmonary complications after lung resection: the effect of continuous extrapleural intercostal nerve block.

To assess the efficacy of continuous extrapleural intercostal nerve block (CEINB) with 0.5% bupivacaine on postoperative pain, pulmonary function and pulmonary complications, a prospective, randomised, double blind controlled trial was conducted on comparable patients undergoing lung resections; n = 21 (control), n = 25 (bupivacaine). The bupivacaine group required less papaveretum in the first 24 h (P less than 0.01) and had lower pain scores over 5 postoperative days (P less than 0.01). Pulmonary function recovered earlier in the bupivacaine group. Pulmonary complications occurred in 1 patient with normal lung function and 12 patients with obstructive airways disease (COAD): FEV1/FVC less than 70%. There were no infusion-related complications. CEINB has been shown to be safe and effective in reducing postoperative pain and pulmonary complications. CEINB minimises the loss of lung function after thoracotomy and restores impaired pulmonary mechanics more rapidly.

Bupivacaine↗
PubMed1990

Chest wall reconstruction after resection of primary malignant chest wall tumours.

In order to review the development of chest wall reconstruction, 37 cases of primary malignant skeletal chest wall tumours treated since 1958 were studied. These included chondrosarcomas (20), Ewing's tumours (7) and solitary plasmacytomas (10). Skeletal reconstruction was performed in 24 patients. Before 1972, Marlex mesh alone was used. Since then, a sandwich of two layers of Marlex mesh with a filler of methyl methacrylate was utilised successfully producing better functional and cosmetic results. Primary soft tissue closure was possible in all but 5 cases in whom latissimus dorsi myocutaneous flaps were used. All but one patient had an uneventful postoperative recovery with none requiring postoperative ventilatory support. The overall survival of 46% at 5 years and 27% at 10 years was encouraging. Familiarity with the techniques of chest wall reconstruction enables wide excision of primary chest wall tumours and the palliation and treatment of other malignant, infective and degenerative conditions since even large defects can be reconstructed with little functional disturbance.

Adolescent↗
PubMed1990

Alterations in respiratory mechanics following thoracotomy.

Major alteration in respiratory mechanics occur in all patients following anaesthesia and thoracotomy because of a decrease in the functional residual capacity with minimal change in the closing volume leading to airway closure during tidal breathing and atelectasis. Diminished pulmonary reserve, because of non-pulmonary and pulmonary risk factors before operation, and/or restrictive ventilation and abnormal pattern of breathing due to postoperative pain sustain and aggravate these changes. These can proceed to postoperative pulmonary complications in some normal, and in many high risk, patients. Detection and correction of pre-existing pulmonary disease, smoking, sepsis and obesity is essential to reduce postoperative morbidity and mortality. Effective postoperative regional analgesia minimizes impairment of pulmonary function, aids in its recovery, and prevents postoperative pulmonary complications. The adjuvant use of chest physiotherapy and incentive spirometry should also help in decreasing the adverse affects of anaesthesia and surgery on the chest and thereby reduce the frequency and severity of postoperative complications.

Anesthesia, General↗
PubMed1990

Primary bony chest wall tumours.

A retrospective review of 81 cases of primary chest wall tumours was carried out to analyse their clinical, radiological and surgical features. There were 37 malignant and 44 benign lesions; 72 were found in the ribs and nine in the sternum, of which five were malignant and four benign. Benign tumours of the ribs outnumbered malignant ones by a ratio of 5:4. The distinction between benign and malignant lesions is difficult clinically and radiologically unless cortical destruction and soft tissue swelling are present. The pathological differentiation is also not possible in all cases. All the patients with benign tumours were treated by excision with no recurrences or deaths. The overall 5-year survival for primary malignant chest wall tumours was 43% and 10-year survival was 27%. These were the results of radical en bloc excisions. Based on our experiences we believe that all tumours of the bony chest wall should be considered potentially malignant and wide excision should be performed, not only to provide adequate tissue for diagnosis but also to allow the best chance of cure in malignant lesions.

Adolescent↗
PubMed1979

Levamisole and surgery in bronchial carcinoma patients: increase in deaths from cardiorespiratory failure.

Life table analysis of early entry to this randomised blind trial of 318 patients has shown a significantly poorer survival for resected lung cancer patients treated with levamisole for three days before operation and three days a fortnight thereafter than for placebo-treated controls. This excess was largely due to deaths that had been attributed to operation or other causes (non-cancer deaths), most occurring in the six weeks after operation. In the 99 resected patients treated with levamisole there was a 15% excess of deaths in this category, compared with the placebo-treated controls. Extensive analysis excluded maldistribution of patients between the groups as a cause of this difference. Many more died in respiratory distress, mostly without clear cause, in the levamisole group. Antibody (lgG) reacting with myocardial sarcolemma or sarcoplasm was found in the only serum samples available for testing which were drawn from patients during the syndrome. The findings are in keeping with a primary effect on the heart, possibly involving an autoimmune mechanism. The effect has not been noted in other trials.

Adenocarcinoma↗
PubMed1978

Environmental significance of fin erosion in southern California demersal fishes.

The Dover sole was the species most often affected with eroded fins. Prevalence of the disease was highest on the Palos Verdes shelf, the site of a major municipal waste water discharge. Fin lesions in this species were characterized by a minimal inflammatory response and by the absence of associated microorganisms. The fins most frequently affected were those most often in contact with bottom sediments. Diseased specimens from the shelf had higher levels of total DDT and a tendency toward higher levels of total PCB in muscle tissue and a greater liver to body weight ratio than did unaffected specimens from the same area. Laboratory exposure of M. pacificus to contaminated sediments from the shelf resulted in the development of fin erosion. Chlorinated hydrocarbon levels and liver weight to body weight ratios in the exposed fish approached those measured in fish from the shelf. These studies suggest that fin erosion in M. pacificus is caused by exposure to contaminated sediments and that the role of chlorinated hydrocarbons should be tested directly in future experiments.

Animals↗
PubMed1978

The potassium status of patients prior to open-heart surgery.

The dysrhythmia that happens after open-heart surgery has at times been attributed to potassium depletion. Therefore, in some centers, patients scheduled for open-heart surgery are routinely given potassium supplements. We have assessed the potassium status of 32 patients prior to cardiac surgery (1) by measurements of plasma, red cell, and leukocyte potassium levels and total body potassium before and after administration of potassium supplements (144 mmoles daily for 3 days) and (2) by the changes in urine potassium during the supplementation. On admission none of the patients showed evidence of a large potassium deficit, and none of them retained much of the supplemental potassium. The observations that have previously been taken as evidence of potassium depletion in such patients are discussed, and alternative explanations are suggested for all these observations.

Body Weight↗