Analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares.

This research explores the pain-relieving, blood pressure, and breathing effects produced by administering a particular painkiller, meperidine hydrochloride, to mares via an epidural in the tail area. The study established that this method induced significant pain relief in the horses without any noticeable side effects.

Research Methodology

• The study involved seven healthy mares, each of which received an epidural injection of either meperidine (at a dose of 0.8 mg/kg body weight) or a saline solution. These treatments were administered on two separate occasions with at least a two-week gap in between.
• Pain responses to different stimuli were measured before and for five hours post-treatment. The variables for these stimuli included noxious electrical, thermal, skin, and muscle stresses.
• The experiment also considered cardiovascular and respiratory variables as well as the degree of sedation and ataxia (disconnected coordination of muscles).

Results

• The administration of meperidine led to bilateral analgesia, pain relief extending from the tailbone to the S1 dermatomes in the standing mares. It’s worth noting that the observed sedation and ataxia were minimal.
• The average onset of pain relief was relatively quick, within 12 minutes after the administration of meperidine. The duration ranged from 240 minutes to the full 300-minute testing period.
• Pertaining to cardiorespiratory variables, measurements of heart and respiratory rates, rectal temperature, arterial blood pressure, Hct (hematocrit), PaO2 (partial pressure of oxygen), PaCO2 (partial pressure of carbon dioxide), pHa (potential hydrogen ions), total solids and bicarbonate concentrations, and base excess were not significantly different from baseline values after the epidural administration of either meperidine or saline solution.

Conclusions

• The findings of the study demonstrated that the tail-end epidural administration of meperidine enforced prolonged perineal pain relief in healthy mares. The degree of sedation and ataxia was minimal, with no observable cardiorespiratory side effects.
• The results suggest that meperidine might be useful for inducing caudal epidural analgesia in mares that need to undergo longer diagnostic procedures, childbirth-related procedures, or surgeries in the anal or perineal region.