High-frequency jet ventilation.

High-frequency jet ventilation is a useful new modality of ventilatory support that offers specific advantage in endoscopy, laryngeal surgery, or mechanically ventilating patients with airway leaks. The method produces lower airway pressures and less movement in the operative field and is well tolerated by the patients. It can be applied by transtracheal puncture as an alternative for emergency airway management.

Transtracheal high frequency jet ventilation prevents aspiration.

Aspiration is a potentially fatal complication of artificial ventilation. A cuffed tube is generally used now to prevent aspiration; however, it may lead to serious complications and has several disadvantages. High frequency jet ventilation (HFJV) is an innovative technique to prevent aspiration. The trachea of 6 anesthetized, paralyzed dogs was exposed and a catheter for jet ventilation introduced between the 1st and 2nd tracheal ring. Another catheter was used for measuring intratracheal pressure. An endoscope was inserted into the trachea about 2 inches lower down and directed upwards to give a view of the vocal cords from below. A mixture of saliva, saline, and cardiogreen was introduced into the mouth so as to form a pool. When observation confirmed that HFJV prevents aspiration at frequencies of 100/min and ratios of inspiration/expiration (I:E) equalling 1:1, observations were repeated at I:E, 1:2 and 1:3 and at rates of 60/min and 200/min. The depth of the pool was gradually increased to between 2 and 31/4 inches and observations were repeated. Endoscopy alone was used in 4 animals and endoscopic film in 2 to evaluate the efficacy of HFJV. The results showed convincingly that: (1) HFJV can prevent fluid from entering the larynx from above; (2) this effect is unreliable when the frequency is decreased to 60/min or inspiration becomes shorter than 33% of the cycle; (3) intratracheal end-expiratory pressures show values slightly higher than the fluid level above the cords; and (4) the cords are separated and the gas mixture bubbles through the fluid. We conclude that (a) valve mechanisms cannot account for our observations; and (b) at rates above 60/min and with duration of expiration of 66% or less, HFJV will prevent aspiration by causing a continuous gas flow outward through the larynx. This is associated with a low continuous positive airway pressure and excellent blood gases.

Tracheobronchial toilet without cardiorespiratory impairment.

Suctioning of the tracheobronchial tree during high frequency jet ventilation (HFJV) in two groups of apneic dogs could be prolonged to 2 min without producing significant drops in PaO2, slowing of the pulse or marked hypertension. Arrhythmias were also virtually absent. The controls reacted to suctioning like human patients. A sharp drop in PaO2, an increase in PaCO2 and a change in pulse rate and blood pressure (BP) as well as frequent premature ventricular contractions were observed.

Cardiovascular reactions to laryngoscopy and tracheal intubation following small and large intravenous doses of lidocaine.

The efficacy of intravenously administered lidocaine 0.75 mg/kg and 1.5 mg/kg to protect against cardiovascular reactions associated with laryngoscopy and tracheal intubation was studied in two comparable groups of ten patients and compared with a similar control group of ten patients given only saline. Following laryngoscopy and tracheal intubation, the 1.5 mg/kg dose afforded complete protection against cardiac arrhythmias of all types. The smaller dose was ineffectual in this respect. While the larger dose caused borderline protection against hypertension and tachycardia, the smaller dose prevented only the rise in systolic blood pressure. Possible mechanisms to account for these observations are discussed. These include a direct myocardial depressant effect, a central stimulant effect, a peripheral vasodilating effect and finally an effect on synaptic transmission.

[Effects of naloxone on postoperative analgesia]. / Etude des effets de la naloxone sur l'analgésie post-opératoire

Two comparable groups of ten patients were studied. After nitrous oxide-oxygen fentanyl-pancuronium anesthesia, half the patients were reversed with a titrated dose of naloxone. Even in titrated doses naloxone rapidly abolished residual post-operative fentanyl analgesia in 80 p. 100 of the patients. In the control group none of the patients complained of pain for an average of six to eight hours. Blood gases in the recovery room were practically the same in reversed and non-reversed patients and were satisfactory.

A method for prevention of cardiovascular reactions to laryngoscopy and intubation.

A technique of nebulizing lidocaine in the upper airways was developed and its effectiveness in preventing cardiovascular responses to laryngoscopy and intubation was documented. In ten pre-treated patients the average percentage-rise in systolic blood pressure was 10.3 per cent and there were no arrhythmias. The pulse rate increased by 16.8 per cent. In ten control patients, the systolic blood pressure increased by 56 per cent and the incidence of arrhythmias was 40 per cent. The pulse rate increased by 38.8 per cent. The significance and application of these results is discussed and compared to other available methods. The opinion is expressed that the effect of the aerosol, especially as it relates to the suppression of arrhythmias, is partly due to systemic absorption of lidocaine.