EFFECTS OF INTRAMUSCULAR OR INTERPLEURAL ADMINISTRATION OF MORPHINE AND INTERPLEURAL ADMINISTRATION OF BUPIVACAINE ON PULMONARY-FUNCTION INDOGS THAT HAVE UNDERGONE MEDIAN STERNOTOMY

Objective-To evaluate effects of interpleural or IM administration of morphine and interpleural administration of bupivacaine on pulmonary f unction in dogs that have undergone median sternotomy. Design-Experime ntal trial. Animals-18 healthy dogs. Procedure-Dogs underwent median s ternotomy and were randomly assigned to groups of 6 dogs each. Group-A dogs were given morphine (1.0 mg/kg of body weight) IM; group-B dogs were given 0.5% bupivacaine (1.5 mg/kg) interpleurally; and group-C do gs were given morphine (1.0 mg/kg) interpleurally. Heart rate; systoli c. diastolic, and mean arterial pressures; rectal temperature; pain sc ore; and arterial blood gas partial pressures were measured and pulmon ary function testing was performed immediately after extubation (time 0) and up to 48 hours later. Serum cortisol and morphine concentration s were measured at time 0 and up to 12 hours after surgery. Results-Th ere was a significant decrease in pH, Pa-o2, mean oxygen saturation of hemoglobin, and dynamic compliance; and a significant increase in Pa- co2, alveolar-arterial difference in partial pressure of oxygen, pulmo nary resistance, and work of breathing for dogs in all groups after su rgery. Serum cortisol concentrations were significantly increased, com pared with preoperative values, in all dogs. Serum cortisol concentrat ions were significantly higher in group-B dogs between 3 and 5 hours a fter surgery, compared with group-A dogs. Conclusions-Median sternotom y was associated with significant alterations in pulmonary function. E ffects of interpleural administration of bupivacaine and morphine were similar to effects of IM administration of morphine.