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Biomedical subjects

G B Drummond

Publications and source records attributed to G B Drummond.

At least 19 recordsLinked to original sources
PubMed1979

Pattern of respiration and responses to carbon dioxide during trichloroethylene anaesthesia in the cat.

Tidal volume (VT), minute ventilation (VE), the duration of inspiratats anaesthetized with 0.7%, 1% and 1.5% (inspired) trichloroethylene (TCE). The tracheal cannula was occluded at intervals at the start of inspiration and the tracheal pressure was measured to assess the force of contraction of the respiratory muscles. Anaesthesia with TCE 0.7% was associated with an increase in VE, a reduction in VT, and a marked increase in respiratory frequency and mean inspiratory flow rate, but PaCO2 values did not differ significantly from those in conscious animals. Ventilation was also greater than in conscious animals during anaesthesia with TCE 1%. TCE 1.5% caused a significantly greater PaCO2 than in conscious animals. All concentrations of TCE caused a reduction in the ventilatory response to carbon dioxide, measured by the steady-state method. Cervical vagal section did not abolish the tachypnoea caused by TCE.

Anesthesia, Inhalation↗
PubMed1979

Metabolic effects of induced hypotension with trimetaphan and sodium nitroprusside.

In two groups of patients undergoing induced hypotension with sodium nitroprusside or trimetaphan blood concentrations of lactate, pyruvate and standard bicarbonate did not differ significantly between the groups. In the nine patients who received trimetaphan there was a progressive, but statistically non-significant, decrease in mean lactate. Nitroprusside (15 patients) was associated with a small increase in mean lactate, but at low dosage there was a small decrease. No relationship to dose rate of nitroprusside was found with these short-term infusions. It is concluded that sodium nitroprusside can be used safely for induced hypotension at doses less than 1.5 mg kg-1 and that simple blood-gas analysis is adequate for the assessment of toxic effects when greater doses are given.

Adolescent↗
PubMed1978

Impairment of oxygen transfer in the lung by increasing oxygen concentration during halothane and trichloroethylene anaesthesia.

Two groups of 10 patients were studied during artificial ventilation with a mixture of oxygen, nitrogen and either halothane or trichloroethylene. Arterial blood and respiratory gas smapling was performed at FIO2 values of 0.33, 0.5 and 0.75. The efficiency of oxygen transfer, expressed as the difference between pulmonary end-capillary and arterial oxygen content, was found to decrease progressively in most patients as the alveolar partial pressure of oxygen increased. This pattern of response may be explained by the effect of oxygen on regulatory reflexes in the lung.

Adult↗
PubMed1978

Pressure-volume relationships in the lung during laparoscopy.

Pressure-volume relationships for the total respiratory system and for the lung were recorded in anaesthetized and paralysed patients, during deflation from an airway pressure of 3 kPa to FRC at a rate of 2 litre min-1. Pleural pressure was estimated by means of an oesophageal balloon. A group of nine female patients (mean age 32.7 yr) about to undergo laparoscopy were each studied in four successive states: supine, 15 degrees head down tilt, tilt and lithotomy position, and again in this position after abdominal inflation with nitrous oxide to a pressure of 0.8(-1) kPa. Compliance values were calculated from the curves. Mean total compliance was increased significantly by moving to the lithotomy position, and reduced markedly after inflation of the abdomen, because of a large reduction in thoracic compliance. Mean lung compliance was unaltered, except for a slight but statistically significant increase on moving from the supine to the Trendelenburg position. Measurement of FRC by helium dilution in a group of seven patients showed that abdominal inflation caused a mean decrease of 19%. Airway closure manoeuvres were carried out using a helium bolus technique from FRC in five patients, but closing volume could be measured in only one patient, in the supine position. The absence of an inflexion in the slope of the pressure-volume curves for the other patients supported this negative finding.

Adult↗
PubMed1978

Circulatory effects of labetalol during halothane anaesthesia.

Labetalol is a drug possessing both alpha and beta adrenergic receptor blocking properties. Its possible use in induced hypotension during halothane anaesthesia has been investigated. It causes a satisfactory decrease in arterial pressure unaccompanied by tachycardia. The circulatory effects of the drug during halothane anaesthesia, both with spontaneous and controlled respiration, have been measured and compared with those of halothane alone. In patients anaesthetised with 1% halothane, labetalol, with both spontaneous and controlled ventilation, was associated with a reduction in MAP from 71.5 mmHg to 54.0 mmHg (P less than 0.001) and 66.8 mmHg to 50.4 mmHg (P less than 0.001) respectively. This reduction was associated with decreases in Qt of 18% and 12% respectively. In the presence of labetalol, with 3% halothane and spontaneous respiration, the depressant effects of the anaesthetic on the heart became rapidly apparent: Qt was reduced by a further 28%. In patients not receiving labetalol, the depressant effects of 3% halothane were frequently countered by the positive inotropic effects of hypercarbia.

Adult↗
PubMed1978

Propranolol in thyrotoxicosis. Cardiovascular changes during thyroidectomy in patients pre-treated with propranolol.

The cardiovascular changes during anaesthesia and thyroidectomy have been studied in seven thyrotoxic patients prepared with propranolol. The heart rate and cardiac rhythm remained very stable throughout surgery. A 20% increase in mean arterial pressure occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgery, reaching a maximum of 21% during ligation of the thyroid vessels and returning to pre-operative values by the end of surgery. The fall in cardiac output was accompanied by raised central venous pressure and raised total peripheral resistance.

Adult↗
PubMed1977

Respiratory effects of extradural analgesia after lower abdominal surgery.

Blood-gas tensions, FRC and volume of trapped gas (VTG) in the lung were measured in patients on the day before lower abdominal gynaecological surgery, and twice on the day following surgery, before and after establishing lumbar extradural block (EDB) using 0.5% bupivacaine to provide analgesia after operation. FRC and VTG were measured with the closed-circuit helium-dilution technique. Mean VTG was 175 ml before operation and 275 ml after operation. PaO2 decreased significantly after operation, and the changes in FRC and VTG that occurred were related qualitatively. EDB did not significantly alter FRC, VTG or PaO2. Individual changes in FRC could not be related to changes in VTG or PaO2. Although EDB provided effective analgesia, the variables measured did not indicate that EDB conferred an immediate respiratory advantage.

Adult↗
PubMed1977

Oxygen therapy after thoracotomy.

Arterial blood samples were taken from patients before thoracotomy, and on the 1st day after operation, with the patient breathing first air, and then 24%, 28% and 35% oxygen from a venturi-type mask. PaO2 was reduced markedly by operation, the reduction being related to the value before operation. Oxygen therapy restored PaO2 to a value greater than the value before operation in nine of 11 patients and was not associated with significant increases in PaCO2. The effect of administration of oxygen on PaO2 could be predicted from the PaO2 when breathing air. The pattern of response to oxygen suggested that the hypoxaemia was caused by ventilation/perfusion mismatch in most of the patients.

Adult↗
PubMed1977

Oxygen therapy after abdominal surgery.

Arterial blood was sampled from 10 patients, on the day after upper abdominal surgery, breathing air, and during oxygen therapy from 24, 28 and 35% venturi masks. PaO2 during breathing each concentration of oxygen correlated with PaO2 during air breathing. The difference between pulmonary end-capillary and arterial oxygen content was used as an index of the impairment of oxygen transfer in the lung. This difference was reduced by oxygen therapy. The response to oxygen therapy did not correspond to predictions based on an iso-shunt lung model. These findings suggest that hypoxaemia in these patients is predominantly caused by ventilation/perfusion mismatching.

Adult↗
PubMed1977

Modification of the circulatory effects of extradural block combined with general anaesthesia by the addition of adrenaline to lignocaine solutions.

The cardiovascular changes associated with extradural block were measured in two groups of patients who were also receiving light general anaesthesia. In the first two group (five patients) 2% plain lignocaine 20 ml was used and decreases occurred in mean arterial pressure, cardiac output, stroke volume and peripheral resistance. In the second group (10 patients) 2% lignocaine 20 ml to which adrenaline 1:200,000 had been added was used. Decreases in arterial pressure and peripheral resistance occurred in all patients, but the responses of the cardiac output and heart rate were variable, decreasing in three patients and remaining stable or increasing in seven patients. A high segmental block was presumed to have occurred in those patients who developed bradycardia and a decreased cardiac output. The differences between these studies in anaesthetized patients and those previously reported in conscious volunteers are discussed.

Adult↗
PubMed1977

Forced expiratory flow-volume relationships. Changes after upper abdominal surgery.

Forced expiratory flow-volume relationships have been used to investigate changes in lung mechanics caused by upper abdominal operations. The slope of the 'effort independent' portion of the flow-volume curve increases after operation, suggesting that restriction of respiratory movement is associated with an increase in lung recoil.

Abdomen↗
PubMed1976

Plasma lignocaine concentrations following endotracheal spraying with an aerosol.

Plasma concentrations of lignocaine were measured in three groups of anaesthetized patients following spraying of the trachea and larynx with a lignocaine 10% aerosol spray. Greater venous plasma concentrations occurred in patients who were paralysed with suxamethonium. A mean plasma concentration of 0.1 mug/ml of lignocaine resulted from each 10 mg of lignocaine used in spontaneously breathing patients, and 0.15 mug/ml in paralysed patients. In individual patients a concentration 50% in excess of the mean value may occur. The use of lignocaine 100 mg as a 10% aerosol spray can be considered safe.

Aerosols↗
PubMed1976

Cardiovascular effects of labetalol during halothane anaesthesia.

1 The circulatory effects of labetalol 25 mg intravenously in six patients during 1% halothane anaesthesia were studied. 2Labetalol caused a marked decrease in arterial pressure and a consistent but modest (20%) decrease in cardiac output. Heart rate was slowed and stroke volume did not change significantly. Central venous pressure increased and peripheral resistance decreased. 3 Increasing the halothane concentration of 3% led to marked myocardial depression as evidenced by reduced cardiac output and increased central venous pressure with increasing arterial hypotension. 4 Labetalol may be a suitable drug for controlling induced hypotension under general anaesthesia, although high concentrations of halothane should be used with care.

Adult↗