Snippet. (epidural anesthesia techniques).
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Anesthesia, Epidural↗
Biomedical subjects
P K Barnes
Publications and source records attributed to P K Barnes.
Glycopyrronium and hypotension following combined spinal-epidural anaesthesia for elective Caesarean section in women with relative bradycardia.
The ability of glycopyrronium to reduce the severity of hypotension following subarachnoid block in parturients with a relative bradycardia was evaluated in a double-blind randomised controlled study. Women with a resting heart rate of < or = 80 beat x min(-1) presenting for elective Caesarean section were randomly allocated to receive either glycopyrronium 2 microg x kg(-1) or normal saline intravenously once positioned for combined spinal-epidural anaesthesia. Following spinal injection of 2.6 ml hyperbaric bupivacaine 0.5% and fentanyl 15 microg, women randomly allocated to the saline group were given 6 mg ephedrine so that all parturients received some prophylaxis against hypotension other than the fluid preload. Further ephedrine and fluid boluses were administered if mean arterial pressure fell 20% or more from resting values. Using a sequential analysis technique, analysis after the first 20 subjects indicated the study should be stopped, with no difference in ephedrine requirements or hypotension between the groups. We conclude that pretreatment with glycopyrronium 2 microg x kg(-1) is no more effective than 6 mg ephedrine in preventing hypotension following subarachnoid block in parturients with relatively low resting heart rates.
Adult↗
Influence of an anaesthetist on nurse-led, computer-based, pre-operative assessment.
Trained nurses using a rule-based computer program can successfully carry out pre-anaesthesia screening. All medical problems and abnormal laboratory results need to be reviewed by an experienced anaesthetist. Following the introduction of this system, there was a reduction in the frequency of cancellations of patients from elective orthopaedic operating lists from 4.8% to 1.8%, a difference that was statistically significant (p = 0.03, CI = [0.6%, 5.5%]). To minimise cancellations from booked operating lists, a booked admissions policy is essential, so that the anaesthetist who will eventually be responsible for patients with medical problems can be identified. Cancellations cannot be avoided completely because some abnormal conditions arise or deteriorate after completion of the screening process. The anaesthetist responsible for the patient's anaesthetic may have different views of the risks involved from those of the anaesthetist undertaking the screening process.
Aged↗
The effect of prophylactic glycopyrrolate on maternal haemodynamics following spinal anaesthesia for elective caesarean section.
We conducted a randomised controlled trial to compare the severity of hypotension and ephedrine requirements following spinal anaesthesia for elective caesarean section in women pretreated with either i.v. glycopyrrolate 4.0 microg/kg (group G) or saline (group S). Data were analysed using sequential analysis which allowed us to terminate the study after data from 40 patients had been analysed (20 in each group). There were no differences between the two groups in the severity of hypotension (mean +/- SD decrease from baseline 35 +/- 14% in group G and 29 +/- 15% in group S) or ephedrine requirements (15 +/- 11 mg in group G and 18 +/- 12 mg in group S). Intra-operative heart rate increased by a greater amount in group G than in group S (58 +/- 26% vs 35 +/- 21% mean +/- SD;P = 0.002) and there was a greater incidence of dry mouth (75% vs 15%;P = 0.0006) but no difference in the incidence of nausea and vomiting (30% vs 50%;P = 0.33). Pretreatment with glycopyrrolate did not confer an advantage in this study.
Clinical Trial↗
Oxygen transport and haemodynamic changes during an anaphylactoid reaction.
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Adult↗
The chronotropic effect of acetylcholine in the presence of vecuronium and atracurium. A study in the isolated perfused rabbit heart.
The bradycardia produced by 1 microgram acetylcholine in the isolated perfused rabbit heart, in the presence of vecuronium and atracurium, was studied and compared with control. Vecuronium at a concentration of 2.5 micrograms/litre and atracurium 6 micrograms/litre did not enhance the negative chronotropic effect of acetylcholine. Atracurium produced a statistically significant inhibition of the negative chronotropic effect of acetylcholine.
Acetylcholine↗
Comparison of the Magill and Lack anaesthetic breathing systems in anaesthetized patients.
The Magill and Lack anaesthetic breathing systems were compared by measuring inspired and expired carbon dioxide concentrations and expired minute volumes in lightly anaesthetized, unstimulated subjects. There were no significant differences between the two breathing systems at fresh gas flow rates of approximately 50 and 70 ml kg-1 min-1. Inspired carbon dioxide concentrations increased in one of six subjects at the higher fresh gas flow rate using the Magill system and in two using the Lack system. Inspired carbon dioxide concentration did not increase in only one of six subjects at the lower fresh gas flow rate with both systems. Expired carbon dioxide concentrations and expired minute volume increased in the majority of subjects at both fresh gas flow rates using each system. We conclude that a fresh gas flow rate greater than 70 ml kg-1 min-1 (which approximated to alveolar minute volume in our subjects) should be supplied to the Magill and Lack breathing systems.
Adult↗
Controlled ventilation with a Mapleson A (Magill) breathing system: reassessment using a lung model.
We have used a lung model to reassess the efficiency of the Magill attachment during controlled ventilation in which the pattern of ventilation, tidal volume and fresh gas flows were varied. Adjustment of the inspiratory:expiratory ratio to ensure a prolonged expiratory phase is recommended, to improve efficiency and predictability of the system, if its use is necessary for short periods during controlled ventilation in clinical practice.
Carbon Dioxide↗
Oxygen analysers. An evaluation of five fuel cell models.
Five currently available fuel cell oxygen analysers were studied with a view to their use in anaesthesia. The accuracy, response time and safety features of these analysers are discussed. Fuel cell analysers appear to be suitable oxygen monitors for routine anaesthetic use.
Anesthesia, Inhalation↗
Plasma histamine levels following atracurium.
Plasma histamine levels were determined in 41 patients, 1.5 and 4 minutes after the intravenous administration of 0.6 mg/kg of atracurium. Clinical features of histamine release were sought at the time of blood sampling. Sixteen patients had elevation of plasma histamine 2.6 (SD 1.2) ng/ml 1.5 minutes after the injection of atracurium. Plasma histamine had returned to control levels at 4 minutes. There was a poor correlation between plasma histamine levels and the clinical manifestations observed. We conclude that atracurium has a low plasma histamine release potential and that cutaneous reactions after atracurium do not always indicate that plasma histamine levels are elevated.
Adolescent↗
Fixed performance oxygen masks: an evaluation.
Fixed performance oxygen masks operate by supplying mixtures of oxygen and air at rates exceeding the inspiratory flow rate of the patient. In this study the oxygen concentration delivered by three fixed performance oxygen masks was determined non-invasively at various inspiratory flow rates. At low inspiratory flow rates all the masks studied acted as fixed performance devices. When the peak inspiratory rate increased the performance of all the masks showed some variability. The change from fixed to variable performance depended on the relation between inspiratory flow rate and the total gas flow delivered by the mask and was independent of the volume of the mask. Hence the use of low volume masks and high oxygen flow rates should produce more consistent results than high volume masks and lower flow rates.
Carbon Dioxide↗
Comparison of the effects of atracurium and tubocurarine on heart rate and arterial pressure in anaesthetized man.
The effects of atracurium and tubocurarine on heart rate and arterial pressure were studied in anaesthetized patients. A bolus of 0.6 mg kg-1 of either atracurium or tubocurarine was administered. Following atracurium, the change in heart rate was minimal (mean +/- SEM: -1.6 +/- 1.3 beat min-1) whereas after tubocurarine heart rate was increased (mean +/- SEM: +9.9 +/- 1.9 beat min-1). Atracurium produced a transient decrease in arterial pressure in 28% of subjects; by the 4th min after its injection the change was minimal (mean +/- SEM: -1.5 +/- 1.1 mm Hg). Tubocurarine produced an initial decrease in mean arterial pressure in all patients, of up to 50% of control values. In the 4th min following its injection arterial pressure was still significantly different from control (mean +/- SEM: -10 +/- 1.5 mm Hg). Endotracheal intubation caused an increase in arterial pressure in all subjects. It is concluded that atracurium has minimal effects on heart rate and arterial pressure when compared with tubocurarine. It does not appear to have a vagal blocking action.
Adult↗
Comparison of the effects of Org NC 45 and pancuronium bromide on heart rate and arterial pressure in anaesthetized man.
The effects of Org NC 45 and pancuronium bromide on heart rate and arterial pressure were studied in anaesthetized man. A bolus of either Org NC 45 0.1 mg kg-1 or pancuronium 0.1 mg kg-1 was administered to lightly anaesthetized unstimulated subjects. Following Org NC 45 heart rate decreased in the majority of subjects (mean and SEM 3.78 +/- 1.36), whereas after pancuronium heart rate was increased (mean and SEM 11.91 +/- 1.9). The changes in mean arterial pressure observed were minimal. The effect of endotracheal intubation on mean arterial pressure was then studied. Increase of mean arterial pressure was observed in all subjects. The increase was more marked in those patients who had received pancuronium and was significantly higher than in those patients who had received Org NC 45 (P less than 0.01). We conclude that Org NC 45 is devoid of vagal blocking action, and that the difference in response to the stimulus of endotracheal intubation is a result of the different effects exerted on the sympathetic nervous system by Org NC 45 and pancuronium.
Adult↗
The Bain breathing system.
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Anesthesia, Inhalation↗
Aural thermometry during profound hypothermia.
External auditory canal temperature changes during profound hypothermia were studied experimentally in ten dogs and clinically in 20 patients undergoing open-heart surgery. The results were compared with nasopharyngeal and lower oesophageal temperatures. Tympanic membrane temperature provided a better approximation to brain temperatures measured in four dogs to below 20 degrees C than did either of the other two methods. In patients, auditory canal temperature showed less variability with respect to oesophageal temperature and fell at a faster rate than did nasopharyngeal temperature. It did not appear to be subject to positional or other artefacts but four patients showed evidence of auditory canal trauma. The precise relationship between auditory canal or tympanic membrane temperature and brain temperature during profound hypothermia is not established. Routine otoscopic examination should accompany the use of an ear probe.
Adolescent↗
Inhibition of neuronal uptake of noradrenaline in the isolated perfused rat heart by pancuronium and its homologues, Org. 6368, Org. 7268 and NC 45.
The cardiovascular effects of pancuronium may be caused partly by an interaction of this drug with the sympathetic nervous system. We examined one possible mechanism of interaction, the effect on the re-uptake processes for noradrenaline. Pancuronium and its closely related steroidal homologues, Org. 6368, Org. 7268 and NC 45, were studied at a high concentration (500 mumol litre-1) for inhibition of the uptake of tritiated noradrenaline into neuronal sites (Uptake1) and extraneuronal sites (Uptake2) in the isolated perfused rat heart. All drugs tested caused almost total inhibition of Uptake1. The bis-quaternary steroids pancuronium and Org. 6368 were selective for Uptake1 inhibition, the mono-quaternary steriods Org. 7268 and NC45 also produced significant inhibition of Uptake2. Uptake1 inhibition was investigated in detail using lesser concentrations of the compounds. All four steroids were found to cause a concentration-dependent inhibition of Uptake1. It seems likely, therefore, that inhibition of neuronal uptake of noradrenaline plays a significant role in the aetiology of the chronotropic actions of pancuronium in the rat.
Animals↗
The Lack anaesthetic system.
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Anesthesia↗