Cervicothoracic (stellate) ganglion block in conscious horses

Seven adult horses were used to compare the cardiovascular and respiratory effects of unilateral (right side) and bilateral cervicothoracic ganglion (CTG) blockade. An 18-gauge, 25-cm needle was placed midventrally between articulations of the 1st and 2nd ribs from a cranial and paratracheal site. One gram of lidocaine HCl in aqueous solution (100 ml) was used to infiltrate the CTG. Cervicothoracic sympathetic blockade was characterized by Horner's syndrome, increased skin temperature and profuse sweating over the face, neck, and thoracic limb. Comparison of base-line data with data obtained during unilateral and bilateral CTG blockades indicated a significant (P less than 0.05) decrease in respiratory rate, significant (P less than 0.05) increases in arterial oxygen, and carbon dioxide tensions, and a significant increase in subcutaneous temperature at the neck and shoulder. Systolic, diastolic, and mean aortic blood pressures, pulse pressure, rectal temperature, arterial pH, bicarbonate, PVC, and total solid concentration did not change significantly from base-line values. Arterial O2 tension was significantly (P less than 0.05) less in horses with bilateral CTG blockade than in horses with unilateral CTG blockade. In 4 horses without cervicothoracic sympathetic blockade that were given lidocaine (1 g in 100 ml) in the right cervicothoracic region, cardiovascular and respiratory values did not change significantly from base-line values. The nonsedated healthy horse tolerated unilateral CTG blockade well. Bilateral and unilateral injections of 100 ml of 1% lidocaine into the CTG at intervals of less than 2 hours induced bilateral recurrent nerve paralysis and airway obstruction.