R. S. Vaughan

Simulated difficult intubation.: Comparison of the gum elastic bougie and the stylet

A randomised study was carried out to compare the efficacy of the gum elastic bougie and the stylet in a simulated difficult intubation. A laryngoscopy assessment, as described by Cormack and Lehane, was made in 100 patients. A Grade 3 view was then simulated. In the Bougie First Group (50 patients) two attempts were made to pass a gum elastic bougie and a tracheal tube into the trachea. If these first two attempts were not successful, two further attempts at intubation were allowed with a stylet placed in the tracheal tube. In the Stylet First Group (50 patients) the order was reversed. After two attempts the tube was correctly placed in the trachea in 96% of cases in the Bougie First Group compared to only 66% of cases in the Stylet First Group (p < 0.001). We recommend that a gum elastic bougie should be readily available and that anaesthetists should use it in preference to a stylet whenever a good view of the glottis is not immediately available.

Respiratory complications associated with tracheal extubation. Timing of tracheal extubation and use of the laryngeal mask during emergence from anaesthesia.

Sixty patients were randomly allocated to one of three groups and the incidences of respiratory complications which occurred during emergence from anaesthesia were compared under the following three circumstances: tracheal extubation after the patient had regained consciousness (awake group); tracheal extubation while the patient was still anaesthetised (anaesthetised group); and the use of the laryngeal mask during emergence from anaesthesia (mask group). In the mask group, the laryngeal mask was inserted under deep anaesthesia before tracheal extubation and the lungs were ventilated through the laryngeal mask after tracheal extubation. In the awake group, straining (bucking) occurred in 18 patients and desaturation (arterial oxygen haemoglobin saturation < 95%) in two patients. In the anaesthetised group, airway obstruction occurred in 17 patients and desaturation in one of these patients. In the mask group, ventilation through the laryngeal mask was temporarily difficult immediately after tracheal extubation in one patient and coughing occurred before removal of the mask in three patients. No respiratory complications occurred in two patients in the awake group, three patients in the anaesthetised group and 16 patients in the mask group. The incidence of respiratory complications during recovery from anaesthesia was significantly lower in the mask group than in the other two groups (pooled) (p << 0.001). Therefore, the use of the laryngeal mask after tracheal extubation decreases the incidence of respiratory complications during recovery from anaesthesia.

The distance between the grille of the laryngeal mask airway and the vocal cords Is conventional intubation through the laryngeal mask safe

The distance between the grille of the laryngeal mask airway and the vocal cords was measured with afibreoptic 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.

Effect of the size of a tracheal tube and the efficacy of the use of the laryngeal mask for fibrescope-aided tracheal intubation

We randomly allocated 60 patients with normal airways into three groups to compare the ease of fibrescope‐aided tracheal intubation using 8.0‐mm internal diameter (group F8) and 6.0‐mm (group F6) reinforced tracheal tubes and to evaluate the efficacy of the laryngeal mask as an aid for fibreoptic tracheal intubation (group L). In group F8 tracheal intubation was optimal in 2 of 20 patients and in two patients in whom intubation over the fibrescope was difficult the attempts resulted in inadvertent oesophageal intubation. In group F6 intubation was always successful and significantly easier than in group F8 (p < 0.005; 95% confidence interval for the difference in the proportion of the optimal intubation grade: 20–70%). In group L tracheal intubation was optimal in 18 of 20 patients and easier than in group F6 (p = 0.014; 95% confidence interval for difference: 10–60%). In both groups F6 and L tracheal intubation was completed within less than about 1 min. We conclude that conventional fibrescope‐aided tracheal intubation with a 6.0‐mm tracheal tube is easier than with an 8.0‐mm tube and that the laryngeal mask facilitates fibrescope‐aided tracheal intubation.

The control of post-thoracotomy pain: a comparative evaluation of thoracic epidural fentanyl infusions and cryo-analgesia

This is a comparative study of two methods to relieve postoperative thoracotomy pain. Continuous thoracic epidural infusion of fentanyl produced superior analgesia when compared with cryo‐analgesia of the relevant thoracic nerves. Linear analogue pain scores were consistently lower in the epidural group reaching significance (p < 0.05) at 32 and 40 hours after operation. All 36 patients in the cryo‐analgesia group required additional analgesia, while 12 out of the 32 patients in the epidural group did not. This difference was significant at p < 0.001. Respiratory and cardiovascular measurements were similar in both groups and the only side effect attributable to the epidural fentanyl was itching but this was not a problem.

Calcium and the anaesthetist

Calcium plays a central role in a large number of physiological actions that are essential for life. It is important therefore that the anaesthetist understands calcium pathophysiology. In this review, the physiology, regulation, clinical features, causes and treatment of alterations in circulating calcium will be discussed. In addition, the effects that acid–base status, massive blood transfusion and cardiopulmonary bypass may have on circulating calcium will be highlighted. Finally, the role that calcium plays in ischaemic/reperfusion injury and myocardial stunning will be summarised.

Cardiopulmonary bypass and complement activation. Involvement of classical and alternative pathways.

Complement is activated during cardiopulmonary bypass with consumption of the complement components C3, C4 and factor B. This takes place when either a bubble or membrane oxygenator is used and is not affected by steroid therapy. Complement activation is predominantly by the classical pathway and may be related to the aggregation of IgM found in bypass sera.

A jet nebuliser for delivery of topical anaesthesia to the respiratory tract A comparison with cricothyroid puncture and direct spraying for fibreoptic bronchoscopy

Topical anaesthesia of the respiratory tract for fibreoptic bronchoscopy was compared, in a single‐blind study, inhaled from a simple and inexpensive jet nebuliser, administered by cricothyroid injection or by a ‘spray‐as‐you‐go technique’. Each technique was supplemented by spraying lignocaine through the fibrescope and intravenous fentanyl‐droperidol sedation. Inhaled nebulisation was successfully used for 96% (46 of 48) of patients, was safe, effective and acceptable to the patient and bronchoscopist. The cricothyroid injection method produced better conditions than nebulisation in patients who had diagnostic bronchoscopy. The nebuliser technique is as satisfactory as the spraying technique in patients for diagnostic bronchial lavage in whom bleeding from a cricothyroid puncture is unacceptable. Patients who used the nebuliser were more satisfied. This technique may also be a useful method for ‘awake’ intubation.

Ease of insertion of the laryngeal mask airway by inexperienced personnel when using an introducer

The Portex introducer for the laryngeal mask airway was designed as an aid to successful insertion, acting as an idealised ‘artificial hard palate’ to guide the tip of the laryngeal mask into the correct position. A number of authors have investigated laryngeal mask insertion by unskilled personnel in certain situations, one example being nurses during in‐hospital cardiopulmonary resuscitation. We investigated whether the introducer had any effect on the incidence of first‐time successful LMA placement by unskilled personnel. These were nonanaesthetist doctors, randomly assigned to have one attempt at LMA insertion in an anaesthetised patient, with and without the introducer. In 44 patients with the LMA being inserted according to the manufacturers instructions, there was a 68% success rate (14 failures). In 45 patients with the LMA being inserted with the aid of a Portex introducer, there was a 96% success rate (two failures). This was a highly significant improvement (p < 0.001).

Intravenous enalaprilat and autonomic reflexes: the effects of enalaprilat on the cardiovascular responses to postural changes and tracheal intubation

Thirty healthy patients, who were to undergo surgery which required tracheal intubation, were given an intravenous injection of enalaprilat (either 0.5 mg, 1 mg, 2 mg or 4 mg; six patients, for each dose) or normal saline 17 minutes before induction of anaesthesia with thiopentone 3–5 mg/kg, and suxamethonium 1.5 mg/kg. Postural manoeuvres were performed 5 minutes before and 6, 11 and 16 minutes after enalaprilat or saline. Complete inhibition of angiotensin converting enzyme occurred with all doses of enalaprilat, which allowed the four different treatment groups to be considered as one large treated group. The mean arterial pressure was almost unchanged during the postural manoeuvres; the heart rate increased, mostly similarly (by approximately 10%) in both groups. Mean arterial pressure in the recumbent position decreased over the 17 minutes before induction in the enalaprilat group, and increased slightly in the control group (treated mean, −5.0%; controls mean, 1.8%; difference, −6.8%; 95% confidence intervals of difference, −2.3 to −11.3%, p < 0.01). This difference was again seen after induction (treated, − 8.0%; controls, 7.7%; confidence intervals of difference, −0.6 to −31%) and for a 5‐minute period shortly after tracheal intubation. The increases in mean arterial pressure produced by intubation itself were similar in both groups (treated, + 36%; controls, +35%; 95% confidence intervals of difference, −16% to +18%). Changes in heart rate after induction were also similar in both groups. It is concluded that intravenous enalaprilat acted as a hypotensive agent with a sparing effect on autonomic reflexes, both before and after induction of anaesthesia.