Overcoming laryngospasm by electrical stimulation of the posterior cricoarytenoid muscle

Difficult Airway Society Guidelines for the management of tracheal extubation

Tracheal extubation is a high-risk phase of anaesthesia. The majority of problems that occur during extubation and emergence are of a minor nature, but a small and significant number may result in injury or death. The need for a strategy incorporating extubation is mentioned in several international airway management guidelines, but the subject is not discussed in detail, and the emphasis has been on extubation of the patient with a difficult airway. The Difficult Airway Society has developed guidelines for the safe management of tracheal extubation in adult peri-operative practice. The guidelines discuss the problems arising during extubation and recovery and promote a strategic, stepwise approach to extubation. They emphasise the importance of planning and preparation, and include practical techniques for use in clinical practice and recommendations for post-extubation care.

Monitoring neuromuscular blockade at the vastus medialis muscle using phonomyography

PURPOSE

The vastus medialis muscle has been recently proposed as a new site for monitoring neuromuscular blockade (NMB). The purpose of this study is to compare NMB at the vastus medialis with the adductor pollicis muscle using phonomyography (PMG).

METHODS

Fifteen patients were enrolled in the study. Anesthesia was induced with remifentanil 0.25 to 0.5 microg x kg(-1) x min(-1), followed by propofol 2 to 2.5 mg(-1) x kg(-1) iv. Analgesia was provided by remifentanil 0.05 to 0.25 microg x kg (-1) x min(-1) iv throughout surgery. A small piezo-electric microphone was attached to the middle of the thenar mass of the right hand to record acoustic signals produced by the contraction of the adductor pollicis muscle. A second microphone was fixed to the medial part of the thigh, 10 cm over the patella, to record the response from the vastus medialis muscle. The ulnar nerve and the im branches of the femoral nerve were stimulated using train-of-four stimulation every 12 sec. Onset, maximum effect, and offset of neuromuscular block were measured after mivacurium 0.2 mg x kg(-1) iv and compared.

RESULTS

At the vastus medialis muscle, the onset of NMB was significantly shorter at 1.9 +/- 0.6 min vs 2.8 +/- 0.7 min, the maximum effect less pronounced at 85 +/- 11% vs 96 +/- 2% and recovery of NMB to 25%, 75%, 90% of twitch control height more rapid than at the adductor pollicis muscle at 17 +/- 2.2 min vs 21.6 +/- 4.2 min, 26.7 +/- 6.5 vs 21 +/- 4.1 min and 30.7 +/- 6.6 vs 35.9 +/- 7.1 min, respectively.

CONCLUSIONS

PMG can be used to measure NMB at the vastus medialis muscle. We found a shorter onset time, less pronounced maximum effect and more rapid recovery of NMB at the vastus medialis muscle than at the adductor pollicis muscle.

Correlation of laryngeal chemoreflex severity with laryngeal muscle response

OBJECTIVES

To examine the relationship between the severity of the laryngeal chemoreflex (LCR) and the pattern of laryngeal muscle activity during an LCR-induced apnea.

METHODS

The laryngeal mucosa of 20 piglets aged 17 to 20 days was stimulated under both hypoxic and normoxic conditions. Respiration, blood pressure, and activity of the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were monitored during the LCR-induced apnea.

RESULTS

Hypoxemia resulted in a shorter average apnea duration but a greater degree of hypotension. All piglets recovered spontaneously following normoxic LCR stimulation. Hypoxic stimulation resulted in two divergent apneic responses: transient with a spontaneous recovery (17 piglets) or profound requiring resuscitation (three piglets). An increase in TA muscle activity and a decrease in PCA muscle activity was the most common response to LCR stimulation. The response of the TA and PCA muscles was maintained in piglets destined for spontaneous recovery. Decreasing TA activity and increasing PCA activity correlated with the development of a profound response.

CONCLUSIONS

The piglet demonstrates two distinct responses to hypoxic laryngeal chemostimulation that correlate with the activity of the intrinsic laryngeal muscles. Failure to maintain the activity of the TA and PCA muscles during a profound response is associated with the development of severe cardiovascular instability. This study suggests that the critical event involving the LCR is the development of complications secondary to hypoxia.

Continuous positive airway pressure as a promoter of laryngospasm during halothane anesthesia

Twenty mongrel dogs were anesthetized with halothane 2.0%, 1.25%, 0.94%, and 0.63% in oxygen. Thyroarytenoid (TA) and posterior cricoarytenoid (PCA) electromyography (EMG) tracings were recorded with the animal at rest, following mechanical irritation of the glottis, and during 20 mm Hg continuous positive airway pressure (CPAP) following either airway occlusion or hyperventilation. Adductor laryngospasm was defined as continuous tonic TA EMG activity, silent PCA EMG, and vocal cord adduction. Abductor laryngospasm was defined as continuous tonic PCA EMG activity, silent TA EMG, and vocal cord abduction. Combined laryngospasm was defined as continuous tonic PCA and TA EMG activity, with variable vocal cord position. The incidence of adductor laryngospasm following mechanical irritation was 30% to 50%. The combined incidence of laryngospasm during application of CPAP following airway occlusion or hyperventilation was 25% to 50%, and differed from the incidence of irritation-induced adductor laryngospasm by 5% or less at the same anesthetic level. Continuous positive airway pressure appears to be a stimulant of laryngeal muscle spasm comparable to mechanical irritation of the glottis.

Postextubation laryngeal spasm in an unanesthetized patient with Parkinson's disease

We present a patient with Parkinson's disease who experienced laryngeal spasm after tracheal extubation without having been anesthetized. This patient's trachea was intubated because of respiratory arrest. We postulate that her postextubation laryngospasm was related to Parkinson's disease.

Abductor vocal cord spasm

The purpose of this study is twofold. First, to introduce a new phenomenon--abductor vocal cord spasm, or abductor laryngospasm. Second, to reconcile a longstanding discrepancy involving the effect of lung inflation on vocal cord position. Abductor laryngospasm was induced in six anesthetized, tracheotomized dogs by the administration of continuous positive airway pressure (CPAP) after occlusion of the trachea for 60 seconds. Abductor laryngospasm was characterized by sustained vocal cord abduction with concomitant massive, continuous posterior cricoarytenoid muscle (PCA) electromyography (EMG) activity and little or no laryngeal adductor muscle EMG activity. Vocal cord opening was sustained for up to 90 seconds. In the same dogs, administration of CPAP, after hyperventilation of the animal, resulted in adductor laryngospasm. Adductor laryngospasm was characterized by steady apposition of the vocal cords, massive laryngeal adductor muscle EMG activity, and silent PCA EMG activity. Abductor laryngospasm appears to be the physiologic converse of adductor laryngospasm. The results of this study show that lung inflation can produce either vocal cord abduction or adduction, depending on whether the dog is hypoventilated or hyperventilated before administration of CPAP.