Effect of Dobutamine on Lung Microvascular Fluid Flux in Sheep with “Sepsis Syndrome”: Experimental Protocol
Baseline studies were performed over a 120-minute period approximately three to four days after recovery from preliminary surgery. Pulmonary lymph was collected and measured for volume every 15 minutes; lymph was pooled at the end of the two-hour baseline period for measurement of total protein and albumin. At the midpoint of this baseline “nonseptic” study, we measured systemic and pulmonary arterial pressures, as well as cardiac output. Blood was drawn from the arterial line and distal port of the right-heart catheter for chemical analysis, hematologic studies, and measurement of arterial and central venous blood gas levels. Dobutamine (500 mg dissolved in 500 ml of 5 percent dextrose in water) was then sequentially administered at two doses (5μg/kg/min and 10μg/kg/ min) for a 60-minute infusion period with each. The first 15 to 30 minutes of infusion at each dose represented a period of equilibration. Pulmonary lymph was collected and measured for volume during each of the last two 15-minute periods of infusion; it was subsequently pooled for measurement of total protein and albumin. Blood was drawn for hematologic studies, chemical analysis, and blood gas levels at the end of each of the last two 15-minute periods of infusion. We also repeated measurement of the cardiac output, and systemic and pulmonary arterial pressures at the same time. Therefore, values reported during infusion of the drug at both doses represent the average of two measurements obtained during two timed 15-minute periods of collection.
Following the nonseptic study, an intra-abdominal source of sepsis was created in the sheep, as previously described. Under general anesthesia with halothane, a lower midline laparotomy was performed; the cecum and ileocecal valve were then identified, and approximately 6 to 8 cm of the distal cecum was devascularized. The bulk of fecal material was milked back into the proximal cecum and right colon. The distal cecum was circumferentially ligated with a No. 2 silk tie below the level of the ileocecal valve. After making a 2-cm perforation in the cecal tip, the compromised bowel was returned to the right lower quadrant. The gastrocolic omentum was then ligated and divided to prevent any early localization of the subsequent inflammatory process. The abdomen was closed in layers, and all animals were returned to their cages and allowed free access to food and water. my canadian pharmacy online
“Sepsis syndrome,” complicated by pulmonary microvascular injury, was defined as an increase in cardiac output and QL, the latter to levels at least 30 percent above preseptic measurements; this usually occurred between 24 and 48 hours after establishing intraabdominal contamination. At this time, baseline septic measurements were performed, as previously described for the nonseptic study. Dobutamine was then infused for 60 minutes at each of the two doses defined; all measurements previously detailed were repeated and averaged during the last two 15-minute periods of infusion at both the 5μg/kg/min and 10μLg/kg/min doses.