Effect of alkalinization on the local analgesic efficacy of ketamine in the abaxial sesamoid nerve block in horses.

This research aimed at investigating how alkalinization affects the efficiency of 1% ketamine as a local analgesic for the abaxial sesamoid nerve block in horses. It was found that the alkalinization of a 1% ketamine solution resulted in more consistent and durable pain relief compared to using 1% ketamine solution alone.

Study Design and Procedure

The research involved:

• Thirty-six mature, healthy horses were divided randomly into four groups. Each group was subject to different treatments.
• The treatments included an abaxial sesamoid block with either a saline solution, a 1% ketamine solution, a saline solution with sodium bicarbonate, or a 1% ketamine solution with sodium bicarbonate.
• All nerve blocks were done on a randomly chosen front leg.
• The analgesia level was determined by assessing the hoof withdrawal from the thermal stimulus from a radiant heat lamp.
• The time between lamp illumination and withdrawal of the hoof, called hoof withdrawal reflex latency (HWRL), was measured before and after the nerve block.
• The local analgesic effects were evaluated at multiple intervals during the hour following the injection, starting 2min after the injection.

Findings

The key discoveries of the study were:

• In the group treated with 1% ketamine solution, there were considerable increases in HWRL from the baseline measurements to the values from between 2 to 10 minutes following the block.
• For the group treated with the 1% ketamine solution and sodium bicarbonate, substantial increases in HWRL were noted between the baseline values and values from 2 to 25 minutes after the block.
• In the group treated with only the 1% ketamine solution, four out of nine horses didn’t respond successfully to the block, while in the group treated with both ketamine and sodium bicarbonate, only one horse had an unsuccessful block.
• The alkalinization of a 1% ketamine solution proved to create a more consistent and long-lasting local analgesia compared to the use of 1% ketamine solution alone.

Implications

This suggests that adding an alkalinizing agent, such as sodium bicarbonate, to ketamine can enhance its effectiveness as a local analgesic in horses. The procedure might prove beneficial in improving the outcome of local analgesia for veterinary practices.