Paula F. Moon

OBJECTIVE: To evaluate the magnitude and mechanism of potential metabolic acidosis after resuscitation with 7.5% sodium chloride/6% dextran-70. DESIGN: Blinded, randomized, control trial. SETTING: Laboratory setting. SUBJECTS: Sixteen healthy Yorkshire swine. INTERVENTIONS: Anesthetized, mechanically ventilated swine underwent 90 mins of hemorrhagic hypotension (mean arterial pressure of 50 to 55 mm Hg), and a lactic acid infusion (1.5 to 2.4 mmol/kg) was given during the last 60 mins of hemorrhage to produce pretreatment acidosis. The pigs were then given either 4 mL/kg of intravenous normal saline (n = 8) or 7.5% sodium chloride/6% dextran-70 (n = 8). Groups then received isotonic lactated Ringer's solution to restore and maintain cardiac output for 120 mins. MEASUREMENTS AND MAIN RESULTS: There was no difference between groups during baseline or shock for any parameter. At the end of shock, arterial pH and base balance were below baseline values. During resuscitation, cardiac output was reached and maintained in both groups. One minute after infusion of hypertonic saline/dextran, there was a significant but transient decrease in arterial pH (from 7.407 +/- 0.015 to 7.339 +/- 0.025) and base balance (from -6.5 +/- 0.7 to -9.9 +/- 1.0 mmol/L). These changes returned to shock levels by 10 mins and then normalized to baseline levels. Hypertonic saline dextran resulted in an immediate hypernatremia, hyperchloremia, and hypokalemia, a decrease in inorganic strong ion difference (calculated as sodium plus potassium minus chloride concentrations), and no immediate change in anion gap. The normal saline group did not show an initial transient decrease in pH and base balance during resuscitation. Plasma lactate, total protein, and hemoglobin concentrations decreased equally in both groups, although they decreased more quickly with hypertonic saline/dextran. CO2 temporarily and insignificantly increased in arterial blood slightly more after the administration of hypertonic saline/dextran. By 120 mins, acid-base, electrolyte and protein changes were normalizing with hypertonic saline/dextran, while pH, base balance, and protein were decreasing below shock values in animals initially treated with normal saline. CONCLUSIONS: Hypertonic saline/dextran caused an immediate, transient acidemia, which was primarily due to a hyperchloremic, hypokalemic, metabolic acidosis with normal anion gap and decreased inorganic strong ion difference, but which was partially due to a mild transient respiratory acidosis. The acidemia was transient because of the offsetting alkalotic effects of decreasing serum protein, normalization of electrolytes, and transient nature of the increase in CO2. Lactic acidosis was not the cause of the acidemia. Over time, the acid-base status appeared to be improved more effectively with hypertonic saline/dextran than with isotonic saline resuscitation.

OBJECTIVE: To describe dogs undergoing cesarean section in the United States and Canada, to determine perioperative management, and to calculate survival proportions. DESIGN: Multicenter prospective case series. ANIMALS: 3,908 puppies from 808 dams. RESULTS: Survival rates immediately, 2 hours, and 7 days after delivery were 92, 87, and 80%, respectively, for puppies delivered by cesarean section (n = 3,410) and 86, 83, and 75%, respectively, for puppies born naturally (498). For 614 of 807 (76%) litters, all puppies delivered by cesarean section were born alive. Maternal mortality rate was 1% (n = 9). Of 776 surgeries, 453 (58%) were done on an emergency basis. The most common breeds of dogs that underwent emergency surgery were Bulldog, Labrador Retriever, Boxer, Corgis, and Chihuahua. The most common breeds of dogs that underwent elective surgery were Bulldog, Labrador Retriever, Mastiff, Golden Retriever, and Yorkshire Terrier. The most common methods of inducing and maintaining anesthesia were administration of isoflurane for induction and maintenance (n = 266; 34%) and administration of propofol for induction followed by administration of isoflurane for maintenance (237; 30%). CLINICAL IMPLICATIONS: Mortality rates of dams and puppies undergoing cesarean section in the United States and Canada are low. Knowledge of mortality rates should be useful to veterinarians when advising clients on the likelihood of puppy and dam survival associated with cesarean section.