Tourniquet-induced hypertension in a horse

Arterial hypertension developed in a horse anesthetized for arthroscopy and lavage of an inflamed right carpal joint. Anesthesia was induced with xylazine HCl, butorphanol, guaifenesin, and thiamylal Na and was maintained with halothane in oxygen. Arterial hypertension and tachycardia developed within 15 minutes after a pneumatic tourniquet was placed 8 to 10 cm proximal to the right carpus and inflated to 800 mm of Hg. The surgical procedure was expedited, halothane was discontinued and anesthesia was maintained with guaifenesin to facilitate bandaging. Heart rate decreased from 72 to 42 beats/min after the tourniquet cuff was deflated. Mean arterial pressure decreased from 260 mm of Hg to 128 mm of Hg. Differential diagnosis for a rapidly increasing arterial pressure during halothane anesthesia include inadequate plane of anesthesia, signs of pain, hypercapnia, hypoxemia, and/or hyperthermia.