The analgesic efficacy of continuous presternal bupivacaine infusion through a single catheter after cardiac surgery

Background: Median sternotomy, sternal spreading, and sternal wiring are the main causes of pain during the early recovery phase following cardiac surgery. Aim: This study was designed to evaluate the analgesic efficacy of continuous presternal bupivacaine infusion through a single catheter after parasternal block following cardiac surgery. Materials and Methods: The total of 40 patients (American Society of Anesthesiologist status II, III), 45-60 years old, undergoing coronary - artery bypass grafting were enrolled in this prospective, randomized, double-blind study. A presternal catheter was inserted with continuous infusion of 5 mL/h bupivacaine 0.25% (Group B) or normal saline (Group C) during the first 48 postoperative hrs. Primary outcomes were postoperative morphine requirements and pain scores, secondary outcomes were extubation time, postoperative respiratory parameters, incidence of wound infection, Intensive Care Unit (ICU) and hospital stay duration, and bupivacaine level in blood. Statistical Methods: Student's t-test was used to analyze the parametric data and Chi-square test for categorical variables. Results: During the postoperative 48 h, there was marked reduction in morphine requirements in Group B compared to Group C, (8.6 +/- 0.94 mg vs. 18.83 +/- 3.4 mg respectively, P = 0.2), lower postoperative pain scores, shorter extubation time (117 +/- 10 min vs. 195 +/- 19 min, respectively, P = 0.03), better respiratory parameters (PaO2/ FiO(2), PaCO2 and pH), with no incidence of wound infection, no differences in ICU or hospital stay duration. The plasma concentration of bupivacaine remained below the toxic threshold (at T24, 1.2 ug/ml +/- 0.3 and T48 h 1.7 +/- 0.3 ug/ml). Conclusion: Continuous presternal bupivacaine infusion has resulted in better postoperative analgesia, reduction in morphine requirements, shorter time to extubation, and better postoperative respiratory parameters than the control group.