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Spinal (subarachnoid) morphine for off-pump coronary artery bypass surgery
Yatin Mehta1, Vinay Kulkarni, Rajiv Juneja
1Department of Anesthesiology and Critical Care, Escorts Heart Institute and Research Centre, New Delhi, India. yatimehta@hotmail.com
Objective:
To study the effects of 8 microg/kg preoperatively administered intrathecal morphine sulfate on extubation time, postoperative pulmonary function, and postoperative analgesia after off-pump coronary artery bypass grafting (OPCAB).
Design:
A prospective, randomized, double-blind, placebo controlled study.
Participants:
One hundred adult patients scheduled for elective primary OPCAB.
Interventions:
Patients were randomized to preoperative administration of 8 microg/kg intrathecal morphine sulfate (group 1) with a 25-gauge spinal needle or to receive sterile normal saline placebo subcutaneously (group 2). Anesthetic induction and maintenance were standardized to allow planning for facilitating early tracheal extubation. Multivessel OPCAB was performed with an Octopus stabilizer. Patients were extubated in the intensive care unit by a blinded observer using predefined extubation criteria.
Measurements And Main Results:
Postoperative times to extubation were 9.47 +/- 3.83 hours in group 1 versus 11.25 +/- 3.94 hours in group 2 (P = .025). Postextubation bedside spirometric lung volumes in percentage of preoperative lung volume showed significant differences in group 1 versus group 2 in forced vital capacity, 39.66% +/- 15.42% versus 31.85% +/- 11.65% (P = .016); forced expiratory volume in the first second, 44.8% +/- 16.18% versus 35.97% +/- 13.32% (P = .013); maximum voluntary ventilation, 39.40% +/- 13.57% versus 33.11% +/- 14.80% (P = .056); and expiratory flow rate, 47.76% +/- 24.61% versus 37.37% +/- 4.33% (P = .031). The visual analog pain scores at rest and during coughing at time intervals of 6, 12, 24, and 36 hours postoperatively showed significantly better results in group 1 compared with group 2. The total dose of fentanyl citrate required intraoperatively was significantly less in group 1 (P = .00). One patient in group 1 had a low respiratory rate, which responded to injection naloxone. There was no mortality or neurological complication in either group.
Conclusion:
Intrathecal morphine provided superior quality of analgesia that translated into better maintenance of postoperative lung volume determined by spirometry. This analgesic method also facilitated earlier tracheal extubation without any major respiratory or neurologic complications.