Evaluation of frontal and infratrochlear nerve blocks for standing sedated frontonasal sinusotomy in horses.

The study aims to ascertain if blocking the frontal and infratrochlear nerves in horses can successfully provide anesthesia for a surgical procedure called frontonasal sinusotomy. The findings demonstrate that this method does indeed increase the mechanical nociceptive thresholds (MNTs) – a measure of the response to potentially painful stimuli – and enables the creation of skin incisions in most cases.

Research Methodology

• The research was divided into two parts, with 6 horses participating in each part of the study.
• Part 1 was a randomized crossover design study. Each horse was given nerve blocks in either the frontal and infratrochlear nerves or a line block using 2% mepivacaine hydrochloride, an anesthetic drug. MNTs were obtained at 5 different sites along the proposed frontonasal sinusotomy line before the injection, and then again at 10, 60, and 120 minutes after blocking. There was a washout period of 4 days between the two nerve block procedures.
• In Part 2, a proof-of-concept study, frontal and infratrochlear nerve blocks were performed on each horse, followed by the creation of skin and periosteal incisions. The area was sutured after 2 hours. The researchers recorded whether the incision site could be successfully created and sutured, as well as the size of the incision.

Findings

• Part 1 of the study found that both line and targeted blocks resulted in at least a two-fold increase in median MNT values at all tested sites in comparison to baseline MNT values.
• During Part 2, incisions were successfully completed in five of the six horses, with a median incision size of 6.5×5 cm.

Conclusions

• The study found that when frontal and infratrochlear nerves were blocked, MNTs increased along a proposed frontonasal sinusotomy line and skin incisions could be created successfully in most cases.
• The research concludes that the blocking of frontal and infratrochlear nerves provides an alternative anesthetic method to carry out a frontonasal sinusotomy, a surgical operation of the sinuses in a horse’s head.