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Biomedical subjects

C Thornton

Publications and source records attributed to C Thornton.

At least 109 records · Page 6Linked to original sources
PubMed1986

Selective effect of althesin on the auditory evoked response in man.

The auditory evoked response (AER) has been studied in six patients before the induction of general anaesthesia, during anaesthesia with nitrous oxide in oxygen and mechanical ventilation, then with a stepwise increasing rate of infusion of Althesin ranging from 18 micrograms kg-1 min 1 to 90 micrograms kg-1 min-1. The sections of the AER examined in this study were the brainstem waves I, III and V and the early cortical waves Pa and Nb. There were dose-related changes in latency and amplitude of waves Pa and Nb, latency increasing and amplitude diminishing with increasing concentrations of alphaxalone as measured in venous blood. In contrast, there were no changes in either latency or amplitude of the brainstem waves. This is consistent with other work suggesting that Althesin has little effect on neuronal function below the level of the superior colliculus.

Adolescent↗
PubMed1985

Effect of etomidate on the auditory evoked response in man.

The effect of etomidate on the auditory evoked response was examined in a double-blind study carried out before the start of surgery. Fourteen patients were anaesthetized with 70% nitrous oxide and oxygen after induction with thiopentone. Ventilation was controlled. Seven of the patients received a continuous infusion of etomidate, increasing in five equal steps from 0.01 mg kg-1 min-1 to 0.05 mg kg-1 min-1 over a period of 50 min. The other seven received similarly an equivalent volume of saline. The patients given etomidate were easily distinguishable from those given saline, solely on the basis of changes in the early cortical peaks Pa and Nb. In the etomidate group the latencies of these peaks increased and their amplitudes decreased. These changes were linearly related to serum etomidate concentration. There was no effect of etomidate on the brainstem response.

Adolescent↗
PubMed1985

Pronounced, episodic oxygen desaturation in the postoperative period: its association with ventilatory pattern and analgesic regimen.

The respiratory effects of two postoperative analgesic regimens were compared in two groups of 16 patients each, recovering from general anesthesia and major surgery. One group received a pain-relieving dose of iv morphine (mean, 18.1 mg), with the same dose repeated as a continuous intravenous infusion over the subsequent 24 h. The other group received regional anesthesia using bupivacaine. The patients were monitored for 16 h after surgery. The two analgesic regimens provided patients with comparable analgesia throughout the study period, but there were quite different respiratory effects in the two groups. Ten patients receiving morphine infusions had a total of 456 episodes of pronounced oxygen desaturation (SaO2 less than 80%). These occurred only while the patients were asleep, and all were associated with disturbances in ventilatory pattern, namely, obstructive apnea (144 episodes in eight patients), paradoxic breathing (275 episodes in six patients), and period of slow ventilatory rate (37 episodes in one patient). In contrast, in patients receiving regional anesthesia, oxygen saturation never decreased below 87%. Central apnea, obstructive apnea, and paradoxic breathing occurred more frequently in patients in the morphine group (12, 10, and 10 patients, respectively) than patients in the regional anesthesia group (4, 3, and 5 patients, respectively). The interaction of sleep and morphine analgesia produced disturbances in ventilatory pattern, causing profound oxygen destruction. These results suggest that postoperative pain relief using regional anaesthesia has a greater margin of safety in terms of respiratory side effects than does the continuous administration of opiates.

Adult↗
PubMed1984

Effects of halothane or enflurane with controlled ventilation on auditory evoked potentials.

The effects of increasing concentrations of halothane and enflurane on selected components of the auditory evoked response were studied in 12 patients; six received halothane and six enflurane. After the induction of anaesthesia with thiopentone, anaesthesia was maintained with 70% nitrous oxide in oxygen. Ventilation was controlled. The inspired concentration of the inhalation agent was increased incrementally, halothane in steps of 0.5% up to 2.5%, and enflurane in steps of 1% up to 5%. With both agents, linear dose-related increases were seen in the latencies of waves III, V, Pa and Nb and the interpeak intervals I-V and III-V, with decreases in the amplitudes of Pa and Nb. In five of the patients the inhalation agent was discontinued at the end of the test period, resulting in reversal of the changes in some or all of these waves. End-tidal carbon dioxide tension was controlled and variations of temperature and arterial pressure were insufficient to produce the observed changes. The results show that halothane and enflurane delay neural transmission along the brainstem and cortical sections of the auditory pathway and that the effects of these agents are approximately related to their known anaesthetic potencies.

Adolescent↗
PubMed1984

EEG electrode positions outside the hairline to monitor sleep in man.

This study investigated the use of electroencephalographic (EEG) electrode placements outside the hairline to monitor sleep. Six subjects slept for 1 night during which the EEG was recorded from "standard" electrode placements and simultaneously from the "test" placements outside the hairline where adhesive pregelled electrodes could be used. Each subject's EEG record was scored independently by two observers. The standard and test electrode placements were assessed separately. Cohen's kappa (kappa) was used to quantify the agreement in the sleep scores (a) between observers when both scored the standard placements and (b) between the test and standard placements when scored by the same observer. The agreement for all stages between observers (a) was excellent (kappa = 0.82); and the agreement within observers, between placements (b) was even better [kappa = 0.86 for the six sleep stages considered separately; when stages awake/1 and 3/4 were combined (a) kappa = 0.88 and (b) kappa = 0.09]. It is concluded that EEG electrode placements outside the hairline can be used effectively to record sleep EEGs. The adoption of these electrode placements would simplify the monitoring procedure for many applied physiological studies especially when usual laboratory techniques for EEG are precluded.

Adult↗
PubMed1983

Enflurane anaesthesia causes graded changes in the brainstem and early cortical auditory evoked response in man.

The effect of increasing end-tidal enflurane concentration on the auditory evoked response was studied in six patients. After a standard induction, anesthesia was maintained with 70% nitrous oxide in oxygen and the end-tidal enflurane concentration was increased gradually from 0 to 1% over a period of 30 min. The averaged auditory evoked response was derived from the electroencephalogram and measurements were made of the latencies and amplitudes of waves I, III, V, Pa and Nb within the auditory evoked response. The latencies of all waves and the interpeak latencies I to V and III to V showed significant linear increases and the amplitudes of Pa and Nb showed significant linear decreases with increasing end-tidal enflurane concentration. These results could not be explained by changes in deep body temperature or end-tidal carbon dioxide concentration. The study demonstrated a dose-related direct effect of enflurane on the brainstem and early cortical components of the auditory evoked response.

Adolescent↗
PubMed1980

The effect of deprenyl, a selective monoamine oxidase B inhibitor, on sleep and mood in man.

The effect of (-)-deprenyl, a rapidly acting selective monoamine oxidase (MAO) B inhibitor, on the sleep and mood of six healthy young male adults was investigated. The drug was administered double-blind in a balanced cross-over design. The dose (5-10 mg/day for 3 days) was chosen to cause complete inhibition of MAO, a process which usually takes 1-2 weeks with conventional MAO inhibitors. The inhibition was monitored by measuring platelet MAO activity and phenylethylamine excretion. Urinary phenylethylamine concentration was raised in all subjects. Subjects were unaware of any sleep disturbance due to the drug although the electroencephalogram (EEG) showed increased wakefulness. The onset of rapid-eye-movement (REM) sleep was delayed and the total amount reduced; the amount of stage 2 sleep was increased. The only effect of the drug on mood was to decrease the level of alertness prior to sleep. There was a slight but significant increase in the pre-sleep systolic blood pressure. There were no effects due to drug withdrawal.

Adult↗
PubMed1976

Blood flow through the calf during recovery from fractures of the lower limb.

1. Venous occlusion plethysmography has been used to measure the blood flow in the calves of nineteen patients with fractures of the lower limb and in six normal control subjects. 2. The resting blood flows were significantly higher in the injured legs than in uninjured legs, irrespective of the site of injury. Flows in the uninjured limbs were similar to those of the control subjects. 3. During reactive hyperaemia after 10 min arterial occlusion, the increase of flows in both legs of the patients was significantly lower than in the control subjects. Because of the increased resting flow, the maximal flow in the injured leg was similar to that in the control subjects, whereas the maximal flow in the uninjured leg was significantly lower than in the control group. 4. The changes in resting flow cannot be accounted for by a change in the proportions of tissues in the limb but they may be explained by an increase of the flow through muscle secondary to a relative increase in the mass of slow to fast muscle fibres.

Adipose Tissue↗