Late-Onset Respiratory Depression Following Preoperative Intrathecal Morphine

Mark C. Allen, M.D., M.S.; Jason Buehler, M.D., Blake Moore, M.D.

Department of Anesthesiology, The University of Tennessee Graduate School of Medicine, Knoxville, Tennessee, United States

Discussion:

Intrathecal morphine-induced respiratory depression can occur early (within first 1 hour following administration) and late (up to 24 hours, highest at 3-12 hours) following administration. Risk peaks at 6 hours post-injection.

Contributing factors to respiratory depression following neuraxial opioid administration include age >65, high dose (>500 mcg) ITM, use of additional opioids, opioid-naïve patient, slowing of CSF dynamics with increased age, hypobaricity of ITM, Trendelenburg position, increased intra-abdominal pressure, positive pressure ventilation, and co-existing lung disease.

•