Limiar nociceptivo mecânico no extrato laminar dorsal em cavalos submetidos à anestesia do nervo digital palmar

Abstract

The study aimed to investigate the effects of anesthesia of the palmar digital nerve or its dorsal branch on the mechanical nociceptive threshold (MNT) of the dorsal laminar region of the equine hoof. Eight mares without any clinical signs of lameness were used. The anesthetics effects of the palmar digital nerve blocks (PD) and dorsal digital nerve branch (DB) were compared by performing both procedures on the same animal only the forelimbs; however, at different times in cross-over design. The treated group was infiltrated with 2% lidocaine, whereas the control with 0.9% NaCl. The volume used was 1 mL for PD and 2 mL for DB. MNT was measured using a portable dynamometer. The evaluated areas were the dorsal laminar region of the hoof (2 and 4 cm distal to the coronary band), the bulbs (lateral and medial), the coronary band (lateral, dorsal and medial) and the sole (dorsal, palmarolateral and palmaromedial). The DP block promoted an increase in the MNT compared to baseline and to the control group in the same time (P<0.001) for the points tested in the bulbs, the sole and dorsal laminar region. The DB block promoted an increase in the MNT compared to baseline and to the control group at the same time (P<0.01) only for the points tested in the coronary band. The PD block, but not the DB block, desensitized the dorsal laminar region indicating that the palmar digital nerve is primarily responsible for the innervation of this region.