To the Editor

In the 2006-07 winter issue of the APSF Newsletter, the suggestion was made that pulse oximetry might be an acceptable monitor to assess and avoid opioid overdose—providing patients breathe only room air. We believe that all post-anesthesia care unit (PACU) patients and those given intravenous and neuraxial opioids should initially be given supplemental oxygen regardless of the monitor used. Hypoxia in the postoperative period is often multifactorial in nature (residual anesthetics, splinting, atelectasis, obesity, fluid overload, opioid medication). Patients can be in pain without significant respiratory depression, yet still be hypoxic. Supplemental oxygen can correct this hypoxia and possibly avoid a catastrophic event. To withhold pain medication from patients because their room air saturations are low would only serve to increase complications relating to the stress response. Patients on oxygen receiving opioids will usually have elevated pCO₂s; however, mild degrees of hypercarbia are well tolerated. It would be ideal to reliably monitor oxygen saturation and expired CO₂ in all patients, but until these monitors become widely available on the hospital wards, we must continue to rely on healthcare providers who are trained to recognize pending opioid toxicity.

Merlin D. Larson, MD
Andrew Itkin, MD
John W. Severinghaus, MD
San Francisco, CA