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Biomedical subjects

R D Page

Publications and source records attributed to R D Page.

10 recordsLinked to original sources
PubMed1992

The use of thalamotomy in the treatment of levodopa-induced dyskinesia.

Peak dose dyskinesia is a major problem in the treatment of parkinsonian patients with levodopa and yet this remains the best pharmacological agent for treating the condition. The hypothesis which this research set out to test was that thalamotomy in the area of the thalamus which receives the input from the medial segment of the globus pallidus would decrease or prevent the dyskinesia. A well established primate model of parkinsonism was used. Eight monkeys (Macaca fascicularis) were rendered parkinsonian with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Regular dosing with levodopa or apomorphine reliably resulted in peak dose dyskinesia. Thalamotomy was carried out using a radiofrequency electrode. To ensure that the appropriate area of the thalamus was targeted, that is the area receiving the pallidal input, an anatomical tracing study was carried out. The anterograde anatomical tracer horseradish peroxidase, covalently bound to wheatgerm agglutinin, was injected into the medial segment of the globus pallidus bilaterally in three monkeys. The target site for thalamotomy was accurately worked out from the tracings obtained. Chorea was usually abolished and always reduced by a thalamotomy in the pallidal terminal territory. This result was obtained after 10 thalamotomies: 4 animals receiving bilateral lesions, with an interval between operations, and 2 animals undergoing unilateral surgery. Lesions in three control sites were carried out and had no permanent effect on chorea. The effect of lesions in other areas was also assessed. Dystonia was not relieved by any thalamic lesion. Thalamotomy is a long established procedure used to help parkinsonian tremor. Appropriately placed thalamotomy should be considered for the relief of disabling peak dose dyskinesia, which is predominantly choreic, in parkinsonian patients on otherwise successful levodopa therapy.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Normothermic arrest with continuous hyperkalaemic blood: initial experience.

The requirement for hypothermia in myocardial protection has recently been questioned. Between October 1990 and May 1991, diastolic arrest was achieved using continuous perfusion with normothermic, hyperkalaemic blood in 257 consecutive patients undergoing cardiac surgery. The mean age was 59.8 +/- 9.3 years (range 28-84 years). Coronary artery surgery was performed in 210 patients, valve replacements in 18, combined procedures in 22, and 7 patients had miscellaneous procedures. Eleven patients (4.3%) had undergone previous cardiac surgery, and 65 (25.3%) required urgent or emergency operations. Hyperkalaemic blood (7-20 mmol/l) was delivered antegradely in 190 (72.8%) patients (mean aortic root pressure 60-80 mmHg), retrogradely in 62 (25.3%) patients (mean coronary sinus pressure less than 40 mmHg), and by a combined route in 5 (1.9%). Sinus rhythm returned immediately after removal of the aortic clamp in 235 (91.4%) patients. Weaning from bypass was achieved without circulatory support in 207 (82.5%) patients. Of 233 patients undergoing non-emergency coronary artery surgery, single valve or combined procedures, 11 died, giving an operative mortality of 4.7%. Of 155 patients with good left ventricular function requiring coronary artery surgery, 3 (1.9%) died. The in-hospital mortality for the group as a whole was 7.3%. Sixteen (6.2%) patients sustained perioperative myocardial infarctions; of these 6 died. We conclude that continuous, normothermic, hyperkalaemic arrest is a simple and safe method of myocardial protection. It may avoid the damage associated with hypothermia, ischaemia and reperfusion.

Adult↗
PubMed1992

Endoscopy assisted microthoracotomy: initial experience.

BACKGROUND: Although thoracoscopy has been used for diagnostic and minor therapeutic procedures for many years, there have been few reports of its use in performing major intrathoracic procedures, which have traditionally required formal thoracotomy. METHODS: Twenty one patients (M:F 1.2:1; mean (SD) age 47.1 (18.8), range 17-75 years) underwent endoscopic intrathoracic surgery. Eight had unidentified peripheral masses on the chest radiograph, eight required lung biopsy, and five had recurrent or persisting pneumothoraces. Under general anaesthesia a laparoscope attached to a video monitor was introduced into the chest. One or two additional stab incisions were made as needed for the introduction of standard surgical or endoscopic instruments and staplers. RESULTS: There were no complications or deaths, though one patient developed a second pneumothorax seven days after endoscopic pleurectomy, necessitating open pleurodesis. All patients were discharged home from two to six days after surgery (mean (SD) 3.7 (1.2) days). CONCLUSION: Endoscopic thoracic surgery is a safe and useful technique for certain cases. It merits further investigation and assessment.

Adolescent↗
PubMed1992

Ultra-pure polymerized bovine hemoglobin blood substitute: effects on the coronary circulation.

The effects of stroma-free hemoglobin (SFHgb) on the coronary circulation remain unclear. An intact canine model utilizing intracoronary adenosine to abolish the confounding effect of autoregulation was used to study maximal myocardial oxygen delivery during progressive hemodilution with polymerized bovine SFHgb. The circumflex coronary artery was instrumented with a flow probe, hydraulic constrictor, and proximal and distal catheters for adenosine infusion and distal pressure measurement, respectively. This preparation was used to generate diastolic coronary pressure-flow relations during maximal vasodilation. Maximal coronary conductance and maximal myocardial oxygen delivery were determined in two groups of 7 dogs each following hemodilution, first with 6% hetastarch (Control), followed by further hemodilution with ultra-pure, polymerized, bovine SFHgb. After hemodilution with SFHgb, maximal coronary flow increased slightly without evidence of coronary vasoconstriction. Since hemodilution with this material increases oxygen carrying capacity, maximal oxygen delivery is greater than Control, despite the very low canine hematocrit. These findings suggest: 1) SFHgb can provide adequate oxygen delivery to the myocardium despite extreme degrees of hemodilution, and 2) in this intact model, there is no evidence of adverse coronary vasomotion.

Animals↗
PubMed1991

Early rupture of a saphenous vein graft.

Early rupture of a saphenous vein graft used for coronary artery surgery has not been previously reported. In a 69-year-old man having a third coronary by-pass procedure, one of the saphenous vein grafts ruptured on the 8th postoperative day. The other vein graft showed marked aneurysm formation at two sites. Histological examination of the ruptured graft revealed that this was due to a bacterial infection within the wall of the vein. Although he survived an emergency operation to control the haemorrhage and replace the ruptured graft, he died some days later of mediastinitis. It appeared that both the rupture of the graft and the ensuing mediastinitis were due to a primary infective process within the saphenous vein used for the graft.

Aged↗
PubMed1991

Prostaglandin regulation of H+ secretion in amphibian epithelia.

The role of prostaglandins in regulating H+ excretion in amphibian epithelia was investigated. The abdominal skin of the southern leopard frog Rana pipiens and the urinary bladder of the toad Bufo marinus were used to measure proton excretion across their mucosal surface. Prostaglandin F2 alpha (PGF2 alpha) produced a dose-dependent inhibition of H+ excretion across the frog skin. Frogs pretreated with ibuprofen (30 mg.kg-1.day-1 for 3 days) showed an enhanced proton excretion similar to that observed when frogs are placed in chronic metabolic acidosis. The number of mitochondria-rich cells, the cells responsible for proton excretion, was also increased in frog skins after chronic metabolic acidosis or ibuprofen treatment. Mezerein and the phorbol ester 4 beta-phorbol 12-myristate 13-acetate (4 beta-PMA), activators of protein kinase C (PCK), decreased H+ excretion in frog skin, whereas the inactive phorbol 4 alpha-PMA was without an effect. The inhibition of proton excretion was similar to that observed with PGF2 alpha and suggested that the effects of PGF2 alpha and activation of PKC were mediated through a common pathway. Frogs pretreated with ibuprofen not only had an enhanced proton excretion rate but also had a decrease in cytosolic PKC activity. In another amphibian tissue, the toad urinary bladder, PGE2 inhibited proton excretion at low doses but enhanced H+ excretion at higher doses. Toads maintained under chronic metabolic acidosis had enhanced proton excretion rates and also had a threefold increase in cellular PGE2 concentration, which was consistent with the observation that PGE2 enhanced proton excretion at high doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphibians↗
PubMed1979

Efficacy of a three- versus a five-week alcohol treatment program.

Eighty-six male alcoholic inpatients were randomly assigned to comparable 3- or 5-week treatment progrrams. Psychometric testing at the beginning and the end of treatment was supplemented by follow-up data 6 months after discharge. While both the 3- and 5-week groups demonstrated significant improvement on both MMPI and follow-up data, few differences between the groups were revealed. The comparable results obtained offer little justification for prolonging inpatient treatment beyond 3 weeks. It is suggested that the inpatient phase of alcohol treatment be brief and oriented to developing a well-structured extended outpatient program.

Alcoholism↗
PubMed1978

EMG biofeedback applicability for differing personality types.

Divided thirty-two male alcoholics into two groups on the basis of their MMPI profile. Group 1 consisted of Ss determined to be tense and anxious, while Group 2 included a more heterogeneous sample of personality types. Eight Ss from each group received 14 days of progressive relaxation training and EMG biofeedback; the remainder received control sessions of taped music and EMG monitoring. Group 1 experimental S achieved greater levels of relaxation than either their matched controls or Group 2 Ss. POMS scores revealed a significant difference over time for all Ss in the direction of improved mood states. No significant between-groups difference was found. Generally, these results suggest the following: (1) patients may be selected credibly for relaxation-biofeedback treatment by use of the MMPI; (2) patients who exhibit significant anxiety and tension may achieve lower levels of tension during training than patients with lower levels of pretreatment anxiety.

Adult↗
PubMedDate not supplied

Determinants of maximal right ventricular function.

After heart transplantation, right ventricular failure can occur because of increased afterload. Previous studies have suggested that the maximal pressure the right ventricle can develop is determined primarily by right ventricular perfusion pressure. However, the interaction of the left ventricle and the pericardium as functional co-determinants of maximal right ventricular function is unknown. This study was undertaken to determine the interaction of the pericardium, left ventricular pressure, and right coronary artery perfusion pressure as potential determinants of maximal right ventricular function. In an acute canine preparation, with progressive pulmonary artery constriction, maximal generated right ventricular pressure was determined over a range of left ventricular systolic pressures. Additional groups of dogs were studied with the right coronary artery cannulated and were maintained at constant perfusion pressure. In all preparations, the maximal pressure the right ventricle could generate was linearly related to left ventricular systolic pressure. Having a closed pericardium markedly enhanced this effect; some effect was present with an open pericardium, although the magnitude of the influence of left ventricular pressure on maximal right ventricular pressure was much less. Maintaining constancy of right coronary artery perfusion pressure, either at high or low values, did not alter these findings nor did it alter the influence of the pericardium. These results suggest that right ventricular perfusion may not be the sole determinant of maximal right ventricular function. Furthermore, with the pericardium open, such as in the posttransplantation state, the left ventricular contribution to maximal right ventricular function may be diminished, increasing vulnerability for right ventricular failure caused by increased afterload.

Animals↗