Muscular Causes of Poor Performance in the Horse: Managing the Case

Recurrent rhabdomyolysis leads to significant changes in the ultrastructure of muscle fibres. this in turn limits muscle function and likely performance of an individual. rapid intervention and the prevention of further muscle injury is therefore important to pre- vent more serious long-term sequalae. patients may be presented for treatment during an acute episode of rhabdomyolysis or between episodes/for the investigation of reduced performance.

Treatment of acute exertional rhabdomyolysis
The treatment required will depend on the severity of the rhabdomyolysis. as myoglobin is nephrotoxic particular attention should be paid to ensuring adequate diu- resis and assessing renal function using clinical chemistry and urinalysis. Large volumes of isotonic fluids (Lactated ringers solution 2-4 ml/kg/hr) may be indicated. if the patient remains anuric despite intravenous fluid therapy diuretic administration may be considered (frusemide 0.5-1 mg/kg iV) and fluid rates adjusted accordingly. Muscle damage often leads to systemic hyperkalaemia, hypocalcaemia and hypochloraemia, therefore measurement of plasma electrolytes in severe cases may be useful to guide supplementation.

Analgesia is very important in these patients, with non-steroidal anti-inflammatory drugs forming the mainstay of treatment (flunixin 0.5-1.1 mg/kg iV q12-24 hours or phenylbutazone 2.2-4.4 mg/kg q12 hours). Given the propensity for renal damage in these patients, monitoring of renal function is recommended if nSaiDs are adminis- tered. in severe cases additional analgesics such as opioids e.g. butorphanol (0.1 mg/kg q4-6 hours) or lignocaine infusions may be considered. acepromazine may be useful in reducing anxiety and has also been advocated for promoting muscle perfusion, how- ever care should be taken when using vasodilators in a hypovolaemic patient. [...]