Analgesic, hemodynamic, and respiratory effects induced by caudal epiduraladministration of meperidine hydrochloride in mares

Objective-To determine the analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in ma res. Animals-7 healthy mares. Procedure-Each mare received meperidine (5%; 0.8 mg/kg of body weight) or s aline (0.9% NaCl) solution via caudal epidural injection on 2 occasions. At least 2 weeks elapsed between treatments. Degree of analgesia in response to noxious electrical, thermal, and skin and muscle prick stimuli was deter mined before and for 5 hours after treatment. In addition, cardiovascular a nd respiratory variables were measured and degree of sedation (head positio n) and ataxia (pelvic limb position) evaluated. Results-Caudal epidural administration of meperidine induced bilateral anal gesia extending from the coccygeal to S1 dermatomes in standing mares; degr ee of sedation and ataxia was minimal. Mean (+/- SD) onset of analgesia was 12 +/- 4 minutes after meperidine administration, and duration of analgesi a ranged from 240 minutes to the entire 300-minute testing period. Heart an d respiratory rates, rectal temperature, arterial blood pressures, Hct, Pao (2), Paco(2), pHa, total solids and bicarbonate concentrations, and base ex cess were not significantly different from baseline values after caudal epi dural administration of either meperidine or saline solution. Conclusions and Clinical Relevance-Caudal epidural administration of meperi dine induced prolonged perineal analgesia in healthy mares. Degree of sedat ion and ataxia was minimal, and adverse cardiorespiratory effects were not detected. Meperidine may be a useful agent for induction of caudal epidural analgesia in mares undergoing prolonged diagnostic, obstetric, or surgical procedures in the anal and perineal regions.