Unilateral cervical plexus block for prosthetic laryngoplasty in the standing horse.

The research article presents a comparison between an ultrasound-guided cervical plexus block (loco-regional anaesthetic technique) and conventional local anaesthetic tissue infiltration in horses undergoing standing prosthetic laryngoplasty (a surgical procedure to correct laryngeal paralysis). The researchers found the cervical plexus block technique improved surgical conditions, though more studies with a larger sample size are recommended to fully determine its effectiveness.

Anatomical Basis & Cadaveric Study

• The study began with the dissection of an equine cadaver to understand the distribution of the second and third spinal cervical nerves (C2 and C3) to all lands of perilaryngeal structures. This process established that C2 and C3 are indeed responsible for sensory innervation in these structures.
• Then, a second cadaver was utilized to map these structures from ultrasound images, to establish the relationship between organ positioning and the ultrasound method. A tissue marker was injected to confirm the feasibility of an ultrasound-guided approach to the cervical plexus.

Clinical Trial

• Following the cadaveric study, a clinical double-blinded trial was conducted. It involved two groups of horses: the first group (CP) received the cervical plexus block and the second group (INF) received the traditional infiltration anaesthetic.
• Various variables such as time taken to complete the procedure, duration of sedation, surgical field conditions, and surgeon’s perception of the block quality were evaluated.
• The results showed that the cervical plexus block provided improved surgical field conditions (P<0.0002), although there were no significant differences in the other variables measured. The ultrasound revealed that the nerve root of C2 was located in a specific location between two major muscles and behind the parotid gland. This information helped the researchers perform the block accurately.

Conclusions

• The study concluded by stating that a larger sample size is needed in future studies to detect smaller differences in surgical procedure completion time based on improved surgical field conditions.
• The central finding of their investigation was that, for standing unilateral laryngeal surgery, cervical plexus block presents a viable alternative to tissue infiltration, and it even enhances the surgical field conditions. This way, surgical procedures can potentially be performed more accurately and efficiently.