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Biomedical subjects

A R Forbes

Publications and source records attributed to A R Forbes.

At least 19 recordsLinked to original sources
PubMed1984

Radiation therapy in the treatment of meningioma: the Joint Center for Radiation Therapy experience 1970 to 1982.

The standard treatment for meningioma is complete resection. However, complete resection is often not possible because of tumor location and extent. To evaluate the usefulness of radiation therapy in patients with unresected or residual tumor, we reviewed the Joint Center for Radiation Therapy experience from 1970 to 1982 (n = 31). Histologic diagnosis was available in 27 patients. The patients were treated with megavoltage radiation to a mean dose of 5,280 rad (3,780 to 6,050 rad) in 180- to 200-rad daily fractions using multiple static or rotational fields. The median follow-up period was 45 months, with a range of four to 156 months. The overall four-year relapse-free survival (RFS) rate was 72%. All relapses occurred within the first 37 months; the mean time to relapse was 31 months. The four-year RFS was the same whether patients were treated at initial presentation or after recurrence (74% v 67%, respectively). There was no difference in RFS for patients treated after partial resection or those patients with no resection (76% v 64%). No patients with malignant meningioma were relapse free three years after radiation therapy. Complications included decreased auditory acuity in three patients and retinopathy in one patient. These data suggest that moderate dose radiation therapy can offer long-term symptom-free survival with few complications in patients having unresected or partially resected benign meningioma.

Combined Modality Therapy↗
PubMed1982

Induction of anesthesia with halothane increases plasma norepinephrine concentrations.

In seven unstimulated, unmedicated patients given halothane/O2 via face mask, plasma norepinephrine concentration increased 15 min after induction and returned to control at 45 to 60 min. Changes in plasma norepinephrine levels did not correlate with changes in cardiovascular variables. In 10 additional awake, unpremedicated patients, plasma norepinephrine concentration did not change during 5 min of application of 100 per cent oxygen via face mask, but rose with subsequent administration of halothane and nitrous oxide. Again, changes in plasma norepinephrine did not correlate with changes in cardiovascular variables. The authors perfused seven isolated cat spleens with a Krebs-Ringer's lactate solution. Addition of 0.01 atm halothane to the perfusate initially increased release of norepinephrine into the effluent. The authors conclude that halothane or halothane-nitrous oxide initially increases plasma norepinephrine during induction of anesthesia. This increase is not due to the placement of a face mask, but may relate to an effect of halothane at sympathetic nerve endings.

Adolescent↗
PubMed1981

Bronchographic features of chronic bronchitis in normal men.

As part of a study of mucous transport in the airways, tantalum bronchography was performed on 13 normal, asymptomatic men who had normal findings on pulmonary function studies. Most of the subjects demonstrated some of the bronchographic features which have been regarded as specific for chronic bronchitis. Eight men showed opacification of the ducts of mucous glands; 12 had visible secretions in the airways; three had moderate-to-marked irregularity of airways. The clearance of tantalum from the airways in all but two subjects was more rapid than anticipated and thus could not be correlated with the bronchographic features of chronic bronchitis. Two subjects who previously had symptoms of respiratory tract infection showed markedly delayed peripheral airway clearance of tantalum. The bronchographic features of chronic bronchitis can be seen in normal subjects or may indicate airway abnormalities that are not manifested functionally.

Adult↗
PubMed1979

Mucociliary clearance in the canine lung during and after general anesthesia.

Central and peripheral pulmonary mucociliary clearance was assessed by tantalum bronchography and serial chest roentgenograms in dogs. Thiopental, 25 mg/kg, did not change clearance from awake values. Halothane 1.2 MAC, for six hours, delayed both central and peripheral clearance by at least three hours. After halothane or diethyl ether, 1.2 MAC, for two hours, recovery of mucociliary clearance was delayed for approximately three and a half hours

Anesthesia, General↗
PubMed1979

Morphine decreases peripheral vascular resistance and increases capacitance in man.

The response of the human peripheral circulation to morphine in large doeses independent of cardiac and respiratory influences has not been delineated. In 28 patients during cardiopulmonary bypass, alterations of peripheral vascular resistance (PVR) and capacitance in response to rapid arterial injection of morphine, 0.5 mg/kg or 1 mg/kg alone, or preceeded by promethazine, 1 mg/kg, naloxone, 10 mug/kg, or naloxone, 20 mug/kg, were recorded over 15 min at a constant perfusion rate. Both doses of morphine decreased PVR by 46 percent at 2 min, with values returning to control at 9 min. When promethazine preceded morphine, the decrease in PVR after morphine was 25 percent. Naloxone did not alter the response. An increase in capacitance of 600 ml observed 5 min after morphine administration did not revert to control after 15 min, and was unaltered by prior administration of naloxone.

Blood Pressure↗
PubMed1979

Lung mucociliary clearance after anesthesia with spontaneous and controlled ventilation.

Anesthesia and controlled ventilation for 2 h delays mucociliary clearance from the lung. To elucidate the contribution of controlled ventilation, mucociliary clearance was assessed by tantalum bronchography and serial chest roentgenograms in 6 dogs. After an induction dose of 25 mg of thiopental/kg of body weight, tantalum insufflation, and immediate recovery from anesthesia, 7 +/- 7 per cent of the tantalum remained in peripheral airways at 6 h. This was not significantly different from the 16 +/- 7 per cent remaining at 6 hours when the dogs had breathed humidified air spontaneously through an endotracheal tube during 2 hours of anesthesia with thiopental (total, 40 mg/kg of body weight). However, when ventilation was controlled during 2 h of anesthesia with 40 mg of thiopental/kg, with a tidal volume of 10 ml/kg or 30 ml/kg, and with a partially deflated endotracheal tube cuff, 43 +/- 11 per cent and 48 +/- 9 per cent of the tantalum, respectively, remained in peripheral airways at 6 h. We conclude that peripheral lung mucociliary clearance is delayed by mechanical ventilation through an endotracheal tube, even with an inspiratory air leak, independent of the tidal volume chosen.

Anesthesia, Intravenous↗
PubMed1977

Mucociliary flow in the trachea during anesthesia with enflurane, ether, nitrous oxide, and morphine.

Tracheal mucociliary flow rates in dogs were measured with a radioactive droplet technique during thiopental anesthesia, and subsequently during enflurane, either, and nitrous oxide-morphine anesthesia on different occasions. Enflurane, at 0.6, 1.2, 1.8 MAC, produced a dose-dependent, reversible depression of mucociliary flow equal to that previously reported for halothane. Nitrous oxide-halothane and nitrous oxide-morphine depressed mucociliary flow to the same extent as halothane at equivalent MAC levels. Ether did not depress mucociliary flow significantly from the thiopental control at any MAC level.

Anesthesia, Inhalation↗
PubMed1976

Halothane depresses mucociliary flow in the trachea.

Tracheal mucociliary flow rates in dogs were measured with a radioactive droplet technique during thiopental anesthesia, and subseqently during halothane anesthesia. Body temperature and inspired gas temperature and humidity were held constant. Ventilation was controlled with 25 per cent oxygen in nitrogen to produce PaCO2 30 torr. Mucociliary flow rate remained constant when halothane concentration was held constant at 1.2 MAC halothane. Mucociliary flow rates at 0.6 MAC halothane were comparable to those after thiopental, 25 mg/kg. Increases in concentration from 0.6 to 1.2 to 1.8 to 2.4 MAC halothane progressively depressed mucociliary flow. Flow at 2.4 MAC halothane was 27 per cent of the control (thiopental) value. Flow returned to previous values as end-tidal halothane concentration was reduced. The depression produced by halothane may represent impairment of an important pulmonary defense mechanism.

Animals↗