CORRESPONDENCE |
Laryngospasm during subarachnoid block
E-mail: cmahindra{at}gmail.comEditor—The case report by Subramani and Paul was quite perplexing.1 The authors proposed that the laryngospasm was secondary to an increased parasympathetic tone resulting from the subarachnoid block.
There are a few points that the authors have not clarified. What was the method by which they tested the level of sensory blockade after injecting the drug in the subarachnoid space? Why did the patient recover rapidly after the stimulus (removal of dressing) was removed? How does an increased parasympathetic tone as a result of subarachnoid blockade explain the further uneventful course? It seems improbable that the laryngospasm responded to atropine and ephedrine.
I would like to put forth a rather simplistic explanation for the laryngospasm—a mere response to pain experienced by the patient. An apparently ‘adequate’ (in extent) spinal may fail because the block has been tested using a stimulus of significantly different modality or intensity than the planned surgery.2 A simple single stimulus such as pinprick or cold may be blocked, but spinal cord mechanisms may result in repeated stimuli (temporal summation) or stimuli from adjacent regions (spatial summation), evoking pain.2 The subarachnoid block was performed in the right lateral position. The onset of bilateral block has been shown to be slower with blocks performed in the lateral position.3 The authors have not made it clear if the block until T11 was bilateral. All these factors alone or in combination, can explain why the patient had laryngospasm.
Whitehaven, UK
References
1 Subramani K, Paul A. Laryngospasm during subarachnoid block. Br J Anaesth 2005; 94: 668–70
2 Hocking G, Wildsmith JAW. Intrathecal drug spread. Br J Anaesth 2004; 93: 568–78
3 Lewis NL, Ritchie EL, Downer JP, Nel MR. Left lateral vs. supine, wedged position for development of block after combined spinal–epidural anaesthesia for Caesarean section. Anaesthesia 2004; 59: 894–8[Medline]
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