Parietal Analgesia Decreases Postoperative Diaphragm Dysfunction Induced by Abdominal Surgery A Physiologic Study

Background and Objectives: The postoperative analgesic strategy may influence the magnitude of the postoperative diaphragmatic dysfunction (PODD) induced by abdominal surgery. The purpose of this physiologic study was to evaluate the effect of continuous preperitoneal wound infusion (CPWI) of ropivacaine on PODD after open colorectal surgery. Methods: Twenty patient,; with American Society of Anesthesiologists physical status I or II undergoing open colorectal surgery were prospectively included during 2 consecutive 2-month periods. During the first period, we evaluated 10 consecutive patients who received conventional parenteral analgesia (intravenously administered morphine via patient-controlled analgesia and acetaminophen) without parietal analgesia (control group). These patients were compared with 10 consecutive patients who received conventional parenteral analgesia along with parietal analgesia using CPWI of 0.2% ropivacaine at 10 mL/hr for 48 hrs (CPWI group). Diaphragmatic function was assessed preoperatively and at 24 and 48 hrs postoperatively using the sniff nasal inspiratory pressure test (Psniff). Supplemental intravenously administered morphine boluses were administered as needed before Psniff assessments in the control group to reduce differences in pain intensity. Results: Demographic and surgical data did not differ between the 2 groups, nor did preoperative Psniff values (71 cm H2O [SD, 20 cm H2O] vs 65 con H2O [SD, 15 CM H2O] in the control and CPWI groups, respectively). Postoperative Psniff was significantly decreased in the 2 groups, but the reduction was significantly greater in the control group than in the CPWI group both at 24 hrs (-58% [SD, 18%] vs -24% [SD, 19%]; P = 0.001) and at 48 hrs (-44% [SD, 31%] vs -11% [SD, 32%]; P = 0.027). Conclusions: Parietal analgesia delivered via a CPWI of ropivacaine reduces PODD induced by open colorectal surgery.