Epidural ropivacaine concentrations for intraoperative analgesia during major upper abdominal surgery: a prospective, randomized, double-blinded, placebo-controlled study.

BACKGROUND: The postoperative beneficial effects of thoracic epidural analgesia (TEA) within various clinical pathways are well documented. However, intraoperative data are lacking on the effect of different epidurally administered concentrations of local anesthetics on inhaled anesthetic, fluid and vasopressor requirement, and hemodynamic changes. We performed this study among patients undergoing major upper abdominal surgery under combined TEA and general anesthesia.
METHODS: Forty-five patients undergoing major upper abdominal surgery were randomly assigned to one of three treatment groups receiving intraoperative TEA with either 10 mL of 0.5% (Group 1) or 0.2% (Group 2) ropivacaine (both with 0.5 microg/mL sufentanil supplement), or 10 mL saline (Group 3) every 60 min. Anesthesia was maintained with desflurane in nitrous oxide (60%) initiated at an age-adapted 1 minimum alveolar concentration (MAC) until incision. Desflurane administration was then titrated to maintain an anesthetic level between 50 and 55, as assessed by continuous Bispectral Index monitoring and the common clinical signs (PRST score). Lack of intraoperative analgesia, as defined by an increase in pulse rate, sweating, and tearing (PRST) score >2 or an increase of mean arterial blood pressure (MAP) >20% of baseline, was treated by readjusting the end-tidal concentration of desflurane toward 1 MAC, and above this level by additional rescue i.v. remifentanil infusion. Hypotension, as defined as a decrease in MAP >20% of baseline, was treated by reducing the end-tidal desflurane concentration to a Bispectral Index level of 50-55 and below that with crystalloid or norepinephrine infusion, depending on central venous pressure.
RESULTS: End-tidal desflurane concentration could be significantly reduced in Group 1 to 0.7 +/- 0.1 MAC (P < 0.001) and to 0.8 +/- 0.1 MAC (P < 0.001) in Group 2, but not in Group 3. Significant hypotension occurred within 20 min in all patients of Groups 1 and 2 (MAP from 80 +/- 10 to 56 +/- 5) (Group 1), 78 +/- 18 to 58 +/- 7 mm Hg (Group 2), P < 0.01, whereas MAP remained unchanged in Group 3 (74 +/- 12 to 83 +/- 15 mm Hg, P = 0.42). Heart rate did not change significantly over time within any of the groups. Furthermore, groups did not differ significantly regarding i.v. fluid and norepinephrine requirement. Patients in Group 3 received more remifentanil throughout the surgical procedure (7.2 +/- 4.9 mg x kg(-1) x h(-1)) when compared with Group 2 (1.6 +/- 2.2 mg x kg(-1) x h(-1)), P < 0.01. Remifentanil infusion among patients receiving ropivacaine 0.5% was not necessary at any time.
CONCLUSION: Epidural administration of 0.5% ropivacaine leads to a more pronounced sparing effect on desflurane concentration for an adequate anesthetic depth when compared with a 0.2% concentration of ropivacaine at comparable levels of vasopressor support and i.v. fluid requirement.

RCT Entities:   Population Interventions Outcomes