Background: Intrathecal opioids have long been used as analgesia for intractable cancer pain or as part of spinal anesthesia during obstetric operations. More recently, they have been used preoperatively as a pain management adjuvant for open cardiac and thoracic procedures.
Objective: This study aims to analyze the impact of administering intrathecal opioids before cardiac and thoracic surgeries on postoperative pain and mechanical ventilation.
Study design: Systematic review and meta-analysis.
Setting: University, School of Medicine, and several university-affiliated hospitals.
Methods: Five outcomes were studied, including the primary outcome of time to extubation, secondary outcomes of analgesia requirements at 24 and 48 hours, resting pain scores at 1 and 24 hours post-extubation, ICU length of stay in hours, and hospital length of stay in days. A search of multiple databases provided 28 studies reporting 4,000 total patients. Outcomes were measured using continuous mean difference with a 95% confidence interval, and the studies were examined for heterogeneity and sensitivity analysis.
Results: The primary outcome analysis suggested that time to extubation was 42 minutes shorter in the intrathecal opioid group (ranging from 82 to 1 minute, P = 0.04). There was also a decrease in postoperative analgesia requirements at both 24 hours (mean difference (MD) = -8.95 mg morphine equivalent doses (MED) [-9.4, -8.5], P < 0.001) and 48 hours (MD = -17.7 mg MED [-23.1, -12.4], P < 0.001) with I2 of 94% and 85% respectively, an improvement of pain scores at both 1 hour (MD = -2.24 [-3.16, -1.32], P < 0.001) and 24-hours (MD = -1.64 [-2.48, -0.80], P =< 0.001) I2 of 94% and 85%, no change in both ICU length of stay (MD = -0.27 hours [-0.55, 0.01], P = 0.06) I2 = 77% and hospital length of stay (MD = -0.30 days [-0.66, 0.06], P = 0.11) I2 = 32%.
Limitations: The major limitation of this meta-analysis was the inconsistent dosages of intrathecal opioids utilized. Some used the same dose for each patient, while other studies used weight-based doses. The differences in the outcomes observed may then be a result of the different amounts of opioids administered rather than the technique itself. Another limitation was the inconsistent timing of reports for pain scores and postoperative analgesic requirements. Further studies were analyzed at the 2 time periods for both secondary outcomes, making it difficult to attribute the 2 effects solely to the intervention.
Conclusions: We conclude that preoperative injection of intrathecal opioids is significantly associated with decreased time to extubation, decreased postoperative analgesia requirement, and improved pain scores. In controlled conditions with adequate staff education, this method of analgesia may make it possible to extubate the patients after the surgery in the operating room and fast-track their discharge from the hospital.
Keywords: cardiac surgery; extubation; fast-tracking; hospital stay; spinal; Analgesia.