Deep hypothermic low flow cardiopulmonary bypass in small dogs

To evaluate the feasibility of and morbidity and mortality associated with cardiopulmonary bypass (CPB) using deep hypothermia and low flow perfusion in adult dogs weighing less than 10 kg.

Prospective, descriptive study.

Two groups of three dogs underwent CPB. Group 1 dogs underwent deep hypothermia (15 to 18 degrees C), 45 minutes of low perfusion flow (20 mL/kg/min) and 1 hour of aortic cross clamp time. In group 2, ultrafiltration of perfusate before discontinuation of bypass was added to the standard treatment. Complete blood counts, serum biochemistry, urine output, ejection fraction, and cardiac output were monitored before and for 7 days after surgery.

All dogs were successfully weaned from bypass. Four of six dogs survived, three without major complications. One dog developed and recovered from septic pleuritis. Two dogs died or were euthanatized after surgery because of respiratory or gastrointestinal complications. Minor complications included anemia, hypoproteinemia, and electrolyte disturbances. Transfusion requirements and edema formation were reduced by ultrafiltration.

The observations in this study support the feasibility of low flow hypothermic CPB. Meticulous tissue handling, precise equipment, ultrafiltration, and aggressive postoperative potassium supplementation are recommended for smaller patients.

Increased sensitivity to adverse sequelae of CPB may be associated with small patient size. Further evaluation is necessary before routine clinical application of low flow hypothermic CPB in this patient population.