Biomedical subjects
Publications and source records attributed to R S Vaughan.
A patient with a tracheostomy and an iatrogenic tracheo-oesophageal fistula presented for diagnostic bronchoscopy and right upper lobectomy. The anaesthetic management is discussed with reference to the options available and, in particular, the use of a Brompton Pallister single lumen endobronchial tube.
We have studied 22 patients to examine whether or not cricoid pressure affects ventilation of the lungs via the laryngeal mask and its correct positioning. In a randomized, crossover design, the laryngeal mask was inserted with or without cricoid pressure applied with a standardized force of 30 N using a cricoid yoke. A standardized pillow (6 cm in height) was placed under the patient's occiput, but the neck was not supported. Ventilation of the lungs via the laryngeal mask was adequate in all patients when no cricoid pressure was applied, but in only three of 22 patients when cricoid pressure was applied (P << 0.001; 95% confidence interval (CI) 0.72-1.0). The mask was positioned correctly in 18 patients when no pressure was applied, and in none after application of cricoid pressure (P << 0.001; 95% CI 0.66-0.98). We had planned to study, in an additional 20 patients, the effect of cricoid pressure without a pillow under the occiput; placement of the mask, however, was difficult even when cricoid pressure was not applied and there was a high incidence of bleeding from the oropharynx. We thus abandoned that part of the study after eight patients. In those eight patients, the success rate of ventilation via the laryngeal mask was lower when cricoid pressure was applied. We conclude that when sufficient force was applied, cricoid pressure, regardless of the method of application, did impede placement of the laryngeal mask.
Twenty patients were studied in a double-blind manner to investigate whether magnesium sulphate, when given during a rapid-sequence induction of anaesthesia, lessens the side effects caused by suxamethonium. Patients were randomly allocated to two groups; equal volumes of either magnesium sulphate (40 mg.kg-1) or saline were given during rapid-sequence induction of anaesthesia, after thiopentone but before the administration of suxamethonium (1.5 mg.kg-1). The changes in the serum potassium concentration, the degree of muscle fasciculations and the presence of postoperative myalgia were recorded. The mean serum potassium concentration increased by 0.08 mmol.l-1 in the magnesium group and by 0.1 mmol.l-1 in the control group at 2 min after injection of suxamethonium; in neither group was there a significant increase from baseline values. The systolic blood pressure and heart rate increased in both groups after tracheal intubation. The incidence of fasciculations was significantly lower in the magnesium group. Magnesium did not clinically prolong muscle relaxation. There was no difference between the groups in the incidence of myalgia after surgery (one patient in each group). Since no significant increase in the serum potassium concentration was demonstrated, no assessment could be made of the effect of magnesium sulphate on the serum potassium concentration after administration of suxamethonium.
We have studied 40 patients to see if cricoid pressure affects the success rate of ventilation through, and the position of, the laryngeal mask and subsequent fiberscope-aided tracheal intubation. Adequate ventilation of the lungs was produced through the laryngeal mask in 19 of 20 patients in the control group, but in only 10 of 20 patients in the cricoid pressure group (P < 0.002). The laryngeal mask was positioned correctly in 16 patients in the control group, but in only two patients in the cricoid pressure group (P < 0.001). Tracheal intubation was accomplished in 19 patients in the control group, but in only three patients in the cricoid pressure group (P < 0.001). Release of cricoid pressure after placement of the laryngeal mask improved the view of the glottis, but tracheal intubation was still difficult because of laryngeal deviation. These results show that cricoid pressure impedes placement of the laryngeal mask and subsequent fiberscope-aided tracheal intubation.
Explore the source record for details and available documents.
A technique for teaching fibreoptic orotracheal intubation in patients under general anaesthesia is described and evaluated. A standard general anaesthetic was administered to 60 patients presenting for elective gynaecological surgery. Patients were randomly assigned to receive either alfentanil 10 micrograms.kg-1 or a placebo, and to be intubated either by a consultant experienced in the use of the fibreoptic bronchoscope or by an inexperienced trainee under instruction. Heart rate, arterial pressure and oxygen saturation were monitored continuously. The time to achieve tracheal intubation in the trainee group was significantly prolonged (p < 0.001), but no patient developed arterial desaturation. The hypertensive response to fibreoptic intubation was suppressed in those patients who received alfentanil (p < 0.001). The increase in heart rate was not suppressed, but was attenuated when these patients were compared with those who had received the placebo (p < 0.001). Alfentanil 10 micrograms.kg-1 minimises the haemodynamic response when teaching fibreoptic orotracheal intubation under general anaesthesia.
In 20 adult patients (18 male) who presented for thoracotomy, the trachea was intubated using Mallinckrodt disposable double-lumen tubes (18 large and two medium). The endobronchial cuff was inflated by a trained operating department assistant using an air-filled syringe. The volume of air and the initial endobronchial cuff pressure were measured. The minimum cuff pressure required to prevent respiratory gas leakage from the isolated lung was measured also and maintained using the Cardiff Cuff Controller. Mean initial cuff pressure was 69.3 (SEM 6.0) mm Hg, whereas the mean minimum cuff pressure was 29.5 (4.0) mm Hg (P < 0.0001). The results suggest that the method described of inflating the endobronchial cuff may lead to overinflation and subsequent excessive pressure on the endobronchial wall.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The distance between the grille of the laryngeal mask airway and the vocal cords was measured with a fibreoptic bronchoscope in 30 male and 30 female patients. The mean distance was 3.6 cm (SD 0.5 cm; range 2.5-4.7 cm) in males and 3.1 cm (SD 0.5 cm; range 2.0-4.2 cm) in females. These results suggest that the cuff of an uncut 6.0 mm tracheal tube would often lie between the vocal cords when the tube is fully inserted through a laryngeal mask airway. To avoid this complication, the tracheal tube must protrude more than 9.5 cm beyond the grille of the laryngeal mask airway. When either neck extension or flexion is required, the laryngeal mask airway should be removed as the margin of safety is small.
The forces required to break and to remove catheters from epidural spaces were investigated. Provided the patient's back is fully flexed and a slow steady pull is applied to the epidural catheter, the extraction forces required at both thoracic and lumbar levels are well below the minimum force required to break the same catheters.
We have studied the effects of phonation and posture on the Mallampati classification of view of the pharyngeal structures. Differences between observers were allowed for by the experimental design and log-linear modelling. Sixty-four patients were assessed on the ward, sitting upright, with and without phonation, by each of two observers. Another 64 patients were assessed without phonation, but both upright and supine, again by both observers. Phonation (the patient saying "Ah") produced a marked, systematic improvement of view; moving to the supine posture produced a small, systematic, non-significant worsening of the view. Differences between observers were non-systematic but substantial. About 25% of patients phonated spontaneously. It is recommended that anaesthetists make their own assessments of Mallampati classification, with the patient in either of the postures but always either with or without phonation, and thereby gradually "calibrate" their assessments against the degree of difficulty encountered in intubation.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effect of allowing patients unlimited access to oral water in the time up until 2 h pre-operatively was the subject of a randomised, blind, controlled trial. No effect was seen on gastric volume or pH, or on plasma osmolality, and allowing water pre-operatively was associated with a reduction in anxiety in the anaesthetic room.
OBJECTIVE: To determine the influence of general or regional anaesthesia on long term mental function in elderly patients. DESIGN: Prospective study of patients randomly allocated to receive general or regional anaesthesia. SETTING: The patients' homes and a large teaching hospital in Cardiff. SUBJECTS: 146 Patients aged 60 and over scheduled for elective hip or knee replacement. MAIN OUTCOME MEASURES: Scores achieved in tests of cognitive function and functional competence. RESULTS: 72 Patients were allocated to receive general anaesthesia and 74 regional anaesthesia. Anaesthetic technique did not influence the duration of the operation, time to mobilisation postoperatively, requirements for analgesia after the operation, or duration of stay in hospital. Three months after the operation there was an improvement in the score for the recognition component (76 ms, 95% confidence interval 9 to 144) and the response component (82 ms, 5 to 158) of the choice reaction time in the group receiving general anaesthesia compared with the group receiving regional anaesthesia. This was the only significant difference between the two groups in the assessments of cognitive and functional competence. Eleven patients receiving regional anaesthesia and 12 receiving general anaesthesia reported that their memory and concentration were worse than before the operation, but this was not confirmed by testing. CONCLUSION: Cognitive and functional competence in elderly patients was not detectably impaired after either general or regional anaesthesia when attention was paid to the known perioperative influences on mental function.