Musa Muallem

Minimum Alveolar Concentrations of Methoxyflurane, Halothane, Ether and Cyclopropane in Man: Correlation with Theories of Anesthesia

The minimum anesthetic concentration (MAC) required in man to prevent a muscular response to a skin incision in 50 per cent of the subjects was determined for cyclopropane, halothane, diethyl ether and methoxyflurane in man. These were (volumes per cent at one atmosphere pressure): cyclopropane 9.2, halothane 0.765, diethyl ether 1.92 and methoxyflurane 0.16. We believe these values, along with the previously determined MACs for fluroxene5 (3.4 per cent) and nitrous oxide4,5 (101 per cent), represent equipotent doses of these agents and provide a useful standard when comparing the circulatory, respiratory or other physiologic effects of one anesthetic with those of another.MAC as a measure of anesthetic potency correlates better with Iipid solubility than with any other physical constant. This correlation should be considered when the primary site of anesthetic action within the brain is sought.

Narcotic Properties of Carbon Dioxide in the Dog

PaCO2 ranging from 15 mm. to 95 mm. of mercury with arterial pH values from 7.64 to 7.10 bad no effect on the minimum anesthetic concentration (MAC) for halothane in dogs. PaCO2 levels above 95 mm. of mercury with arterial pH below 7.10 were progressively narcotic, and replaced the halothane required to maintain a constant depth of anesthesia. Anesthesia was achieved with CO2 alone at PaCO2 of 245 mm. of mercury. The mechanism of CO2 narcosis correlated well (P>0.05) with the pH changes in the brain as measured in the cisternal CSF, and appeared to be independent of arterial pH, PaCO2 and cerebrospinal fluid PCO2

Tracheal intubation using the GlideScope with a combined curved pipe stylet, and endotracheal tube introducer.

CAN J ANESTH 54: 1 www.cja-jca.org January, 2007 8 Hernandez-Diaz S, Varas-Lorenzo C, Garcia Rodriguez LA. Non-steroidal antiinflammatory drugs and the risk of acute myocardial infarction. Basic Clin Pharmacol Toxicol 2006; 98: 266–74. 9 Kearney PM, Baigent C, Godwin J, Halls H, Emberson JR, Patrono C. Do selective cyclo-oxygenase-2 inhibitors and traditional non-steroidal anti-inflammatory drugs increase the risk of atherothrombosis? Metaanalysis of randomised trials. BMJ 2006; 332: 1302–8.

Jet ventilation in a case of tracheal obstruction secondary to a retrosternal goitre

Intermittent jet ventilation was used during anaesthesia in a 66-yr-old woman who had severe tracheal narrowing secondary to compression by a retrosternal goitre. The trachea was intubated by a smallbore tube, which was placed above the site of narrowing. An injector was connected to the proximal end of the tracheal tube on one side and to the anaesthesia circuit on the other. Intermittent jets of 66% nitrous oxide in oxygen via the injector resulted in adequate oxygenation and carbon dioxide elimination. Arterial blood gas analysis during jet ventilation showed PaO2 150 mmHg, PaCO2 35 mmHg and pH 7.4. It is concluded that lowfrequency jet ventilation may provide adequate oxygenation and carbon dioxide elimination in the presence of tracheal narrowing.RésuméOn a utilisé la ventilation intermittente à jet pendant l’anesthésie d’une femme de 66 ans souffrant dun rétrécissement trachéal serré causé par un goitre rétrosternal. La trachée est intubée d’abord avec un tube de petit calibre placé au dessus du rétrécissement. Un injecteur est branché sur l’extrémité proximale du tube endotrachéal d’un côté et sur le circuit anesthésique de l’autre. Des jets intermittents de protoxyde d’azote 66% avec oxygène produisent une oxygénation et une élimination du gaz carbonique adéquates. L’analyse des gaz artériels montre une PaO2 de 150 mmHg, une PaCO2 de 35 mmHg et un pH de 7,4. Nous concluons que la ventilation par jet à basse fréquence peut procurer une oxygenation et une élimination du gaz carbonique adéquates en présence d’un rétrécissement serré de la trachée.

Bullard laryngoscopy for tracheal intubation in a neonate with Pierre‐Robin syndrome

In a newborn with Pierre‐Robin syndrome, repeated attempts using standard direct laryngoscopy failed to visualize the glottis or even the tip of the epiglottis. In contrast, a clear view of the glottis was seen when the Bullard fibreoptic paediatric laryngoscope was used. Tracheal intubation was facilitated by ‘rail‐roading’ the tube over a bougie which was threaded via the suction channel of the laryngoscope into the trachea. The report suggests that the Bullard fibreoptic laryngoscope can succeed to visualize the glottis in the newborn with Pierre‐Robin syndrome, whenever the glottis cannot be brought within line‐of‐sight by standard laryngoscopy.

The use of the GlideScope to facilitate nasotracheal intubation: in patients with a difficult airway.

Cooper RM, 2005, CAN J ANAESTH, V52, P191; Muallem Musa, 2000, Middle East Journal of Anesthesiology, V15, P687; Muallem M, 2007, CAN J ANAESTH, V54, P77; Pandian A, 2008, EUR J ANAESTH, V25, P511, DOI 10.1017-S0265021507002906

Oxygen Jet Ventilation of Patients with Tracheal T-Tube

To the Editor: A silicone rubber tracheal T-tube has been proposed by Montgomery (1) as a tracheal stent. Anesthesia and intermittent positive-pressure ventilation (IPPV) of patients having a tracheal T-tube pose a problem as a significant air leak can occur via the upper airway whenever the patient is anesthetized or ventilated via the extraluminal limb of the tube (2, 3) . Different procedures have been suggested to prevent the upward air leak, such as occluding the upper airway with a molded polyurethane pharyngeal pack (2) or blocking the upper intraluminal limb of the T-tube with a Fogarty embolectomy catheter (3) . We have successfully used intermittent oxygen jets as an alternative method of IPPV in two women undergoing insertion of tracheal Ttubes. In one patient the T-tube was placed for the management of tracheomalacia following thyroidectomy, whereas in the second patient the tube was placed following surgical excision of excessive tracheal granulations. In both cases, bronchoscopy was initially performed under intravenous thiopental-succinylcholine drip anesthesia, while ventilation was carried out by intermittent oxygen jets (50 psi) delivered via a Sanders Venturi injector adapted to the proximal head of the bronchoscope (4). Jet ventilation was controlled by an electronically operated solenoid switch. After the anatomic diagnosis had been confirmed, surgery proceeded while continuing jet ventilation via the bronchoscope. As soon as the Ttube was placed in the trachea, the bronchoscope was withdrawn and a

Awareness during anaesthesia due to a ventilator malfunction

usually due to either inadequate regional analgesia or an improper curve at the distal end of the endotracheal tube and stylet. This technique has been used successfully and without complications for cases of difficult intubation where the head could not be extended (burn strictures and unstable fractures of the neck), cases of oral and oronasal tumors where there was not room for a laryngoscope, or in larger children with congenital syndromes where visualization of the larynx was improbable or impossible (Treacher-Collins and Pierre-Robin syndromes). Since the ‘light wand’ will not go through a tube of less than 5.0 mm internal diameter, a smaller version of the ‘light wand’ was devised for small children (less than 2 years). This, however, was not as successful, probably because a greater curve to the light wand was necessary due to the more cephalad position of the larynx in small children, and the endotracheal tube would not pass off the end of the stylet into the trachea. For this reason, this technique is not recommended for smaller children. In older children maintenance of the airway by mask using a general anaesthetic and muscle relaxant, followed by the light wand intubation frequently works well for the intubation challenges mentioned above.

Automatic jet ventilation in children anaesthetized by the T-piece circuit

Investigation was carried out in ten children aged between one month and six years, who were anaesthetized by the T‐piece circuit. The volume of the reservoir tubing of the T‐piece was 250 ml. Ventilation was controlled automatically by oxygen jets which were delivered via an injector attached to the reservoir tubing. The oxygen jets were regulated by an electronically‐controlled solenoid valve. The children were ventilated by a tidal volume about 12 ml±kg−1 at a rate of 12‐20 per min depending on their age, while the FGF varied between 3 and 6 l min−1 depending on their body weight. The resulting FIO2 ranged between 0.32 and 0.34 which was expected from the oxygen:nitrous oxide mixture (1:2), denoting no mixing of the oxygen jets with the anaesthetic mixture. The PAco2 was ventilation‐dependent, and ranged between 4±6‐5±3 kPa (35‐41 mmHg). The results suggest that automatic jet ventilation facilitates controlled ventilation in children anaesthetized by the T‐piece circuit, while maintaining the original simplicity of the T‐piece.;

Dependent PEEP during two-lung ventilation in the lateral decubitus position.

In anesthetized patients in the lateral decubitus position, the dependent lung is less ventilated and more perfused than the nondependent lung, resulting in ventilation-perfusion mismatching (1-3). A physiologic solution to the adverse effects of anesthesia and surgery in the lateral decubitus position on the distribution of ventilation and perfusion would be the application of selective positive end expiratory pressure (PEEP) to the dependent lung (2,3). Selective PEEP to the lower lung may increase ventilation of this lung by moving it up to a steeper, more favorable portion of the lung pressure-volume curve; it may also increase vascular resistance in the lower lung and shift more blood flow to the upper lung. The present report investigates the effect of selective application of dependent PEEP in patients undergoing radical nephrectomy in the lateral decubitus position. The investigation compares the differential distribution of ventilation between the dependent and the nondependent lungs, as well as the arterial PO, and PCO, levels before and after application of the dependent PEEP.