Assessment of hydromorphone and dexmedetomidine for emesis induction in cats

A Comparative Study of the Antiemetic Effects of α2-Adrenergic Receptor Agonists Clonidine and Dexmedetomidine against Diverse Emetogens in the Least Shrew (Cryptotis parva) Model of Emesis

In contrast to cats and dogs, here we report that the α2-adrenergic receptor antagonist yohimbine is emetic and corresponding agonists clonidine and dexmedetomidine behave as antiemetics in the least shrew model of vomiting. Yohimbine (0, 0.5, 0.75, 1, 1.5, 2, and 3 mg/kg, i.p.) caused vomiting in shrews in a bell-shaped and dose-dependent manner, with a maximum frequency (0.85 ± 0.22) at 1 mg/kg, which was accompanied by a key central contribution as indicated by increased expression of c-fos, serotonin and substance P release in the shrew brainstem emetic nuclei. Our comparative study in shrews demonstrates that clonidine (0, 0.1, 1, 5, and 10 mg/kg, i.p.) and dexmedetomidine (0, 0.01, 0.05, and 0.1 mg/kg, i.p.) not only suppress yohimbine (1 mg/kg, i.p.)-evoked vomiting in a dose-dependent manner, but also display broad-spectrum antiemetic effects against diverse well-known emetogens, including 2-Methyl-5-HT, GR73632, McN-A-343, quinpirole, FPL64176, SR141716A, thapsigargin, rolipram, and ZD7288. The antiemetic inhibitory ID50 values of dexmedetomidine against the evoked emetogens are much lower than those of clonidine. At its antiemetic doses, clonidine decreased shrews' locomotor activity parameters (distance moved and rearing), whereas dexmedetomidine did not do so. The results suggest that dexmedetomidine represents a better candidate for antiemetic potential with advantages over clonidine.

Effects of pretreatment with medetomidine, midazolam, ketamine, and their combinations on stress-related hormonal and metabolic responses in isoflurane-anesthetized cats undergoing surgery

Objective:

The purpose of this study was to compare the effects of pretreatment with medetomidine (Me), midazolam (Mi), and ketamine (Ke) on stress-related neurohormonal and metabolic responses in isoflurane-anesthetized cats undergoing ovariohysterectomy and castration.

Materials and Methods:

We prospectively recruited 112 client-owned healthy mixed-breed cats. In both surgeries, we divided the cats into seven groups (eight cats per group): non-treatment (control), Me (50 μg/kg), Mi (0.5 mg/kg), Ke (5 mg/kg), Me + Mi, Me + Ke and Me + Mi + Ke administered intramuscularly. After pretreatments, we maintained anesthesia with isoflurane and oxygen. Venous blood was taken before pretreatment, pre- and post-operatively during anesthesia, and at early- and complete-recovery.

Results:

Both plasma adrenaline and noradrenaline were reduced during anesthesia in all groups. Plasma cortisol increased during anesthesia and at early recovery in non-Me-treated groups, whereas it decreased in Me-treated groups in both surgeries. Plasma insulin and non-esterified fatty acid (NEFA) decreased, and glucose increased during anesthesia in all groups, but hyperglycemia and decrease in NEFA were greater in Me-treated groups.

Conclusions:

In isoflurane-anesthetized cats undergoing surgeries, premedication with Me alone and in combination is useful for reducing the perioperative stress-related increase in cortisol and catecholamines except for hyperglycemia.