Development of a new system for guidewire-assisted tracheal intubation: manikin and cadaver evaluation.

Guided intubation using a tracheal tube and semi-rigid introducer is associated with technical difficulties, failure and traumatic complications. We describe the development of a new system of guidewire-assisted tracheal intubation that may circumvent these problems. A reinforced silicone tracheal tube was modified with a guide channel built inside its wall, and a nitinol non-kinking guidewire was matched to this channel. Both anterograde and retrograde tracheal intubation were evaluated in a test rig, an airway manikin and then in preserved and fresh cadavers. There was minimal resistance to passage of the guidewire through the guide channel when the modified tube was in an anatomical configuration, in contrast to moderate resistance when an Airway Exchange Catheter was passed through a PVC tracheal tube. Intubation using the new equipment required increased force in the manikin and preserved cadavers, but minimal force in fresh cadavers. Resistance to tracheal tube advancement in preserved cadavers was overcome by withdrawal followed by 90° rotation, but this manoeuvre was not required in fresh cadavers. We suggest that the combination of the modified tracheal tube and matching guidewire may allow easy and reliable single-step guided tracheal intubation when used in patients.

Retrograde tracheal intubation.

Summary Successful management of difficult tracheal intubation by retrograde intubation has been reported for almost 50 years and can be used whether or not it is anticipated. There are numerous reports of variations to the basic technique to enhance reproducibility of this guided blind procedure. A review and analysis of the equipment and techniques provides a better understanding of this effective technique.

High frequency jet ventilation through a supraglottic airway device: a case series of patients undergoing extra-corporeal shock wave lithotripsy.

High frequency jet ventilation has been shown to be beneficial during extra-corporeal shock wave lithotripsy as it reduces urinary calculus movement which increases lithotripsy efficiency with better utilisation of shockwave energy and less patient exposure to tissue trauma. In all reports, sub-glottic high frequency jet ventilation was delivered through a tracheal tube or a jet catheter requiring paralysis and direct laryngoscopy. In this study, a simple method using supraglottic jet ventilation through a laryngeal mask attached to a circle absorber anaesthetic breathing system is described. The technique avoids the need for dense neuromuscular blockade for laryngoscopy and the potential complications associated with sub-glottic instrumentation and sub-glottic jet ventilation. The technique was successfully employed in a series of patients undergoing lithotripsy under general anaesthesia as an outpatient procedure.

Monitored transtracheal jet ventilation using a triple lumen central venous catheter.

Two patients with nasopharyngeal carcinoma, radiotherapy treatment and 'difficult' airways were anaesthetised for oral surgery. A triple lumen central venous catheter was inserted through the cricoid membrane and transtracheal jet ventilation with an AMS 1000 jet ventilator was performed via the distal lumen. The middle and proximal lumens were connected to an airway pressure monitor and a capnograph, enabling breath-by-breath monitoring of ventilation.

Sevoflurane output from the Oxford Miniature Vaporizer in drawover mode.

The sevoflurane output from the Oxford Miniature Vaporizer (OMV) was measured in a series of bench tests in a drawover system. Using a range of settings on two OMVs in series, output ranged from 0.5 to 5.9% with a 600 ml tidal volume at a rate of 12 breaths/min produced by a Penlon Multivent. The OMVs' output was steady over 40 minutes. In tests with tidal volumes ranging from 300 ml to 1200 ml, the OMVs' output was lower at higher minute volumes. When continuous flow of carrier gas at 7.2 l/min was used, the output was lower than at the equivalent intermittent flow rate. Using two OMVs with a drawover system appears to be a feasible technique for the induction and maintenance of sevoflurane anaesthesia. Clinical tests of sevoflurane drawover anaesthesia are now required so that the advantages of sevoflurane can gain wider application in field and military anaesthesia.

A nonoccluding bag and closed scavenging system for the Jackson Rees modified T-piece breathing system.

We used the inner tube and its 22-mm connector from the patient end of a Bain breathing system to splint the double-ended bag of the Jackson Rees modification of the Ayre's T-piece breathing system. A paediatric airway pressure-limiting valve was connected to the distal end of the tube for closed scavenging. The resistance of the modified bags was similar to that of unmodified bags at gas flows below 11 l.min-1. The valve offered no resistance to gas flows below 5 l.min-1. During its use in 30 paediatric patients, analysis of carbon dioxide from inside the bag and from the expiratory port confirmed no loss of deadspace gas by preferential flow bypassing the bag into the scavenging system.

Sevoflurane anaesthesia with the Komesaroff vaporizer inside the circle system.

This study assessed the safety of sevoflurane anaesthesia using two Komesaroff vaporizers inside the circle with both spontaneous and controlled ventilation. Sevoflurane concentrations were continuously monitored using a mass spectrometer and the anaesthetic depth was easily controlled. Involuntary movements occurred in eight patients and breath-holding occurred in five patients after inhalational induction. With continuous monitoring of sevoflurane concentrations, induction and maintenance of anaesthesia using a vaporizer inside the circle is safe during both controlled and spontaneous ventilation. However the high incidence of involuntary movements may limit the feasibility of induction in spontaneously breathing patients.

Sevoflurane anaesthesia with an Oxford Miniature Vaporizer in vaporizer inside circle mode.

Anaesthesia was induced and maintained successfully with sevoflurane using an Oxford Miniature Vaporizer (OMV) in vaporizer inside circle (VIC) mode. With continuous monitoring using the Drager Narkomed 4 machine agent analyser, the expired sevoflurane concentration was monitored and controlled easily. During induction, there was no cardiovascular depression, apnoea or coughing, but involuntary movements and breath-holding were common.

Postoperative hypoxaemia during transport and in the recovery area.

This study was undertaken to ascertain the incidence of postoperative hypoxaemia in the recovery area and during transfer to the recovery area while adhering to the current practice of anaesthesia and recovery room care. Attempts were also made to determine some of the risk factors for the development of hypoxaemia. There were 546 patients who had general or regional anaesthesia observed in the recovery area and of these, 534 patients were also observed during transfer using Critikon Oxyshuttle pulse oximeters. The incidence of hypoxaemia (SpO2 < or = 90%) and severe hypoxaemia (SpO2 < or = 85%) during transfer were 10.11% and 2.06% respectively. The incidence of hypoxaemia and severe hypoxaemia in the recovery area were 8.42% and 2.2% respectively. No oxygen was given to patients during transfer. In the recovery area, 322 patients (58.97%) had oxygen therapy and 224 patients (41.03%) did not. The occurrence of hypoxaemia during transfer was significantly related to the duration of surgery. In the recovery area, age and weight were found to be statistically significant risk factors. The incidence of hypoxaemia in this study is much lower than that reported in other studies.

A multilumen catheter guide for difficult airway management. Its uses in anaesthesia and intensive care.

A multilumen catheter guide (jet stylet) with an adapter has been used for various manoeuvres in the upper airway. With the split length, procedures such as change of tracheal tube from oral to nasal nasal to oral position, are possible while the patient's lungs are ventilated by means of high frequency jet ventilation. During high frequency jet ventilation for longer periods of time, for example for microlaryngeal surgery, the central channel of the catheter is used as a conduit for jet delivery, whilst the other channels are used for continuous monitoring of airway pressure and concentration of carbon dioxide in the upper airway.

Preoperative plateletpheresis does not reduce blood loss during cardiac surgery.

Acute preoperative plateletpheresis has been reported to be effective in reducing blood loss and blood component transfusion while improving haematological profiles in patients undergoing open-heart surgery. However, in these studies, the concomitant use of cell saver techniques may have been responsible for the beneficial effects because they remove free haemoglobin and activated procoagulants and, therefore, could mask the deleterious effects of combined plateletpheresis and cardiopulmonary bypass (CPB). In the present study, 40 patients undergoing primary myocardial revascularization were randomly divided into two groups: a control group without plateletpheresis performed, and a second group in which preoperative platelet-rich plasma 10 ml.kg-1 (PRP group) was collected and later reinfused after reversal of heparin. Standardized surgery, anaesthesia and CPB without concomitant cell saver techniques were employed. In the PRP group, blood transfusion was reduced (1.5 +/- 1.3 vs 2.4 +/- 1.3 units, P < 0.05) but this was accompanied by lower postoperative haemoglobin concentrations. There were no differences in blood loss (992.6 +/- 327.4 vs 889.6 +/- 343.7 ml), fresh frozen plasma (2/19 vs 3/20 patients) or platelet requirements (1/19 vs 1/20 patients). Reinfusion of autologous PRP did not improve platelet count and function, nor tests of coagulation. Fibrinogen concentrations were lower in the PRP group on the operative day (P < 0.05), suggesting increased fibrinogen consumption; and more patients in the PRP group had low haptoglobin levels during CPB (8/19 vs 0/20 patients, P < 0.005), which indicated greater haemolysis in this group. We conclude that acute preoperative plateletpheresis offers no advantage in haemostasis during elective primary myocardial revascularization surgery.

Retrograde intubation--a facilitated approach.

The procedure of retrograde tracheal intubation has been facilitated by the use of a multilumen catheter guide. When used as an anterograde guide, it would easily follow the retrograde guide and would direct placement of the tracheal tube atraumatically. A new technique is described that allows stabilization of the anterograde catheter and its insertion deep inside the trachea to prevent dislodgement of the tracheal tube from the laryngeal inlet. This catheter guide may also be used as a conduit for high-frequency jet ventilation with monitoring of the airway pressure, thus providing wider margins of safety in patients with difficult upper airways.

High frequency jet ventilation for microlaryngeal laser surgery. An improved technique.

The use of a triple lumen central venous catheter, which can be shielded from laser irradiation by metal tape, as a conduit for high frequency jet ventilation in six children, is described. The problems of anaesthesia for laryngeal laser surgery and the advantages of the technique described in this paper are discussed.

Prediction of difficult laryngoscopy: an assessment of the thyromental distance and Mallampati predictive tests.

Two hundred and fifty patients were assessed preoperatively using the Mallampati classification and by measuring their thyromental distances. The ease or difficulty of direct laryngoscopy was assessed at the time of induction of anaesthesia. Retrognathia was seen in 15.6% of patients and the incidence of difficult laryngoscopy without external laryngeal pressure was 8.2%. It was found that both assessments predicted less than two in three difficult laryngoscopies and had high false positive rates. It was found that external laryngeal pressure often improved the view of the glottis in difficult laryngoscopies.