Effects of high-dose gentamicin sulfate on neuromuscular blockade in halothane-anesthetized horses

Brent A. Hague From the Departments of Large Animal Medicine and Surgery (Hague) and Small Animal Medicine and Surgery (Martinez, Hartsfield), College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474.

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Elizabeth A. Martinez From the Departments of Large Animal Medicine and Surgery (Hague) and Small Animal Medicine and Surgery (Martinez, Hartsfield), College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474.

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Sandee M. Hartsfield From the Departments of Large Animal Medicine and Surgery (Hague) and Small Animal Medicine and Surgery (Martinez, Hartsfield), College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474.

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SUMMARY

Objective

To evaluate effects of a single high dose of gentamicin on neuromuscular function in horses anesthetized with halothane.

Animals

6 healthy adult horses.

Procedure

Halothane-anesthetized horses were positioned in left lateral recumbency, and the right hind limb was immobilized in a reusable fiberglass cast fixed to a steel frame. The hoof was attached to a force transducer, and resting tension of 0.93 ± 0.16 kg was maintained. A supramaximal train-of-four stimulus of 2 Hz for a duration of 0.25 millisecond was applied to the superficial peroneal nerve every 20 seconds by a square-wave stimulator. The force of the evoked digital extensor tension was recorded to determine first muscle twitch tension, compared with the baseline value (T1%) and the ratio of the force of the fourth twitch to the first twitch (T4/T1). Data were recorded at 5, 10, 15, 30, and 60 minutes after IV administration of vehicle or gentamicin (6 mg/kg of body weight).

Results

There was a significant (P = 0.04) treatment-time interaction for the effect of gentamicin on T1%; T1% associated with vehicle decreased from 100% to 92% during the 60- minute study period, but no decrease was associated with gentamicin. For T4/T1, there was no significant effect of treatment or time or treatment-time interaction between gentamicin and vehicle.

Conclusions

Gentamicin did not cause a decrease in initial muscular strength, nor did it impair the muscles’ ability to sustain strength.

Clinical Relevance

A single high dose of gentamicin does not cause significant neuromuscular blockade when administered alone to healthy horses anesthetized with halothane. (Am J Vet Res 1997;58:1324–1326)

SUMMARY

Objective

To evaluate effects of a single high dose of gentamicin on neuromuscular function in horses anesthetized with halothane.

Animals

6 healthy adult horses.

Procedure

Halothane-anesthetized horses were positioned in left lateral recumbency, and the right hind limb was immobilized in a reusable fiberglass cast fixed to a steel frame. The hoof was attached to a force transducer, and resting tension of 0.93 ± 0.16 kg was maintained. A supramaximal train-of-four stimulus of 2 Hz for a duration of 0.25 millisecond was applied to the superficial peroneal nerve every 20 seconds by a square-wave stimulator. The force of the evoked digital extensor tension was recorded to determine first muscle twitch tension, compared with the baseline value (T1%) and the ratio of the force of the fourth twitch to the first twitch (T4/T1). Data were recorded at 5, 10, 15, 30, and 60 minutes after IV administration of vehicle or gentamicin (6 mg/kg of body weight).

Results

There was a significant (P = 0.04) treatment-time interaction for the effect of gentamicin on T1%; T1% associated with vehicle decreased from 100% to 92% during the 60- minute study period, but no decrease was associated with gentamicin. For T4/T1, there was no significant effect of treatment or time or treatment-time interaction between gentamicin and vehicle.

Conclusions

Gentamicin did not cause a decrease in initial muscular strength, nor did it impair the muscles’ ability to sustain strength.

Clinical Relevance

A single high dose of gentamicin does not cause significant neuromuscular blockade when administered alone to healthy horses anesthetized with halothane. (Am J Vet Res 1997;58:1324–1326)

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