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Biomedical subjects

D G Wells

Publications and source records attributed to D G Wells.

At least 19 recordsLinked to original sources
PubMed1992

Isomorphic activation of astrocytes in the somatosensory thalamus.

Structural recovery in the rat somatosensory thalamus after the loss of one of its major inputs provided a model for studying the changes in astrocytes associated with reactive synaptogenesis. The temporal separation of the initiation of Wallerian degeneration and reactive synaptogenesis permitted astrocytic changes to be correlated either with the removal of degeneration, early in the recovery sequence, or with synaptogenesis, later in recovery. Over a period of post-lesion times ranging from 3 days to 13.5 months, GFAP-positive astrocytic fibers were quantified and the population density of S-100-positive astrocytic cell bodies was determined in the ventral posterolateral nucleus (VPL). The relative area of astrocytic cell bodies was measured at an early peak of the increased GFAP immunoreactivity (4-5 days post-lesion). The normal side of VPL (c-VPL) was compared to the deafferented side of VPL (d-VPL) and the ratio d-VPL/c-VPL was determined. Astrocytes in d-VPL underwent a minimal isomorphic activation with little or no hypertrophy or proliferation but with a large increase in GFAP immunoreactivity. Prior to the initiation of synaptogenesis, there was a decrease both in GFAP immunoreactivity and in the population density of VPL astrocytes. The decreases in the recovery curves suggested that a suppression of the influence of astrocytes may have been important for sprouting and/or synaptogenesis. In other systems, where synaptogenesis was initiated early in the recovery sequence, the suppression of astrocytes that was related to synaptogenesis may have been masked by astrocytic changes related to the removal of degeneration.

Afferent Pathways↗
PubMed1992

Platelet-leukocyte plasmapheresis attenuates the deleterious effects of cardiopulmonary bypass.

A method of harvesting a high yield of concentrated platelet- and leukocyte-rich plasma was developed with the goal of attenuating some of the deleterious effects of cardiopulmonary bypass. The study involved 32 patients who underwent coronary artery bypass grafting with plasmapheresis before cardiopulmonary bypass and a control group of 32 patients who did not have plasmapheresis. A volume of 857 +/- 359 mL of platelet- and leukocyte-rich plasma was concentrated from 4.6 +/- 1.5 L of blood, and red cells and plasma were returned to the patient. The platelet- and leukocyte-rich plasma contained yields of 3.5 +/- 1.4 x 10(11) platelets and 3.4 +/- 1.9 x 10(9) leukocytes. There were no differences in age, sex, duration of cardiopulmonary bypass, and major risk factors between groups. However, total mediastinal chest tube drainage was 788 +/- 542 mL in the controls and 425 +/- 207 mL in the plasmapheresis group (p less than 0.01). Homologous units transfused were 3.9 +/- 2 in controls and 1.6 +/- 2 in the plasmapheresis group (p less than 0.01). Arterial oxygen tension on extubation was 94 +/- 32 mm Hg in controls and 119 +/- 25 mm Hg in the plasmapheresis group (p less than 0.01). This technique of platelet and leukocyte protection results in reduced postoperative bleeding, a decreased need for homologous blood products, and improved pulmonary function.

Aged↗
PubMed1989

Attenuation of electroconvulsive therapy induced hypertension with sublingual nifedipine.

Five patients known to be previously hypertensive but not currently receiving anti-hypertensive medications were studied for a total of twenty-six administrations of electroconvulsive therapy. Patients randomly received sublingual nifedipine 10 mg, 20 minutes prior to half of their treatments, and for the remaining treatments acted as their own controls. The use of nifedipine resulted in significant attenuation of the blood pressure response to therapy. Systolic pressure increase was 24 mmHg (SD 14) versus 62 mmHg (SD 24) (P less than 0.01). There was no difference in heart rate between the two groups. It is concluded that nifedipine reduces the pressor response to electroconvulsive therapy in individuals with a history of hypertension.

Administration, Sublingual↗
PubMed1988

Cell-sized microspheres in the hippocampus show cleavage planes and passive displacement.

Fluorescent microspheres (6 or 10 micron in average diameter) dispersed in fluid were injected into the hippocampus, neocortex or striatum. In the hippocampus the microspheres were located in one of three cleavage planes. Cleavage planes were found above the alveus, in the obliterated hippocampal fissure and on the hilar side of the dentate granule cells. When the injections were made into the infragranular cleavage plane, the adjacent granule cells degenerated, presumably because the cavity separated the axons from their cell bodies. Some microspheres were passively displaced beyond the boundary of the injection site. If the microspheres gained access to the subarachnoid space, some of the displaced microspheres were found at considerable distances from the injection site. There were no cleavage planes in neocortex or striatum but there was passive displacement of microspheres into the host parenchyma. In cell suspension transplants, the passive displacement of cells should be distinguished from migration and the possibility of a widespread distribution of transplanted cells needs to be considered.

Animals↗
PubMed1987

Precipitous bradycardia induced by laryngoscopy in cardiac surgical patients.

We present three patients with severe ischaemic heart disease who developed profound bradycardia (heart rates of 15 beats.min-1, 10 beats.min-1 and asystole) at the time of laryngoscopy and spraying of the trachea with topical lidocaine. All patients had received fentanyl 20-30 micrograms.kg-1 and pancuronium 0.1-0.13 mg.kg-1 and in each case laryngoscopy was performed three minutes after the administration of these agents. We believe that in these cases the dosage of fentanyl was inadequate and since increasing the dosage of fentanyl to at least 50 micrograms.kg-1 and eliminating the manoeuvre of laryngeal spraying with topical anaesthesia, we have not encountered this problem.

Aged↗
PubMed1987

Anaesthesia and Marfan's syndrome: case report.

An 18-year-old male with Marfan's syndrome underwent surgery for repair of an ascending aortic dissection. The clinical features of this congenital syndrome and the acute management of its complications are described. As elective surgery is frequently required for ocular, musculo-skeletal or cardiovascular problems in people with Marfan's syndrome, patients must be carefully assessed preoperatively for specific complications. Significant pulmonary problems include restriction of lung function due to pectus excavatum or kyphoscoliosis and intrinsic pulmonary involvement with emphysema, bronchogenic cysts and "honeycomb lung." This leads to a significant incidence of spontaneous pneumothorax and the danger of tension pneumothorax with positive pressure ventilation. The commonest causes of sudden death are cardiovascular complications, in particular rupture and dissection of the ascending aorta. Preoperative assessment should include echocardiography to determine the size of the aortic root. The anaesthetic technique chosen should both decrease myocardial contractility and avoid sudden increases in contractility, in order to minimise the risk of aortic dissection or rupture.

Adolescent↗
PubMed1987

Anaesthetic-related recovery room complications.

A prospective survey was conducted over a one-month period in all surgical patients admitted to the recovery room of a university-affiliated teaching hospital. Complications arising in the recovery room were documented by the nursing staff according to predefined criteria and were critically evaluated. A total of 443 patients were admitted to the recovery room and in 133 (30%) of these, some form of complication was noted. There were 86 patients with complications referable to the central nervous system, 68 with abnormal cardiovascular parameters, 24 with nausea and/or vomiting and 10 with abnormalities referable to the respiratory system. Many patients had more than one complication. The results are discussed, with emphasis on their relevance to current anaesthetic practice. It is concluded that many patients exhibit recovery room complications when they are specifically sought. The recovery period remains a time of great potential danger to patients.

Adult↗
PubMed1987

Nitrous oxide and cerebrospinal fluid markers of ischaemia following cardiopulmonary bypass.

Twenty patients with good ventricular function undergoing coronary artery bypass surgery were studied to determine whether the pre-bypass use of nitrous oxide resulted in any differences in cerebrospinal fluid markers indicative of cerebral ischaemia. All patients were anaesthetised with diazepam, fentanyl and pancuronium, after which ten patients received 50-60% nitrous oxide in oxygen until commencement of bypass, and the remaining patients 100% oxygen. Because of the known effect of nitrous oxide in expanding gaseous bubbles, any neurological dysfunction of gaseous microembolic origin may be worsened in the presence of nitrous oxide. Patients were lumbar punctured 24 hours after cardiopulmonary bypass and cerebrospinal fluid analysed for the following markers of central nervous system ischaemia: creatine kinase, lactate, total protein, noradrenaline, adrenaline and adenylate kinase. There was a statistically significant difference in cerebrospinal fluid lactate between the two groups. There were no statistically significant differences in the other cerebrospinal fluid markers of ischaemia.

Adenylate Kinase↗