← Chapter 4
Medical-Surgical Nursing · Chapter 4

Sedation Watch

Opioid-induced respiratory depression is almost never sudden — advancing sedation comes first, every time. You have one opioid-naive patient on a PCA and six checks between 2100 and 0200. At each check, choose what you actually do. The bench keeps the trend, grades the call, and at the end tells you what a late escalation would have cost.
Room 412 · Delia Marsh, 68 — post-operative day 0, open colectomy. Hydromorphone PCA started at 2000, demand only, 8-minute lockout, verified with a second RN. Gabapentin 300 mg given at 2100. Lorazepam 1 mg PRN for sleep is on the order set. Continuous pulse oximetry and capnography are running per unit policy; oxygen 2 L nasal cannula was added at 0030.
Opioid-naiveAge 68BMI 34STOP-BANG 5 — high risk for OSAGabapentinoid on boardPRN benzodiazepine ordered
2100Check 1 of 6
What do you do?
2100 — two hours into the PCA
Read the sedation level first, the respiratory rate second. That order is the whole lesson.
Respiratory rate and end-tidal carbon dioxide trend Respiratory rate falls from 16 at 2100 to 8 at 0200 while end-tidal carbon dioxide rises from 38 to 61 millimetres of mercury. Oxygen saturation stays near normal until late because supplemental oxygen masks it.

Pasero Opioid-induced Sedation Scale (POSS)

LevelDescriptionNursing action
The monitoring trap
Supplemental oxygen masks desaturation. A patient on 4 L nasal cannula can hypoventilate to an end-tidal carbon dioxide of 60 mmHg (normal 35–45) while still reading a saturation of 96 percent. Capnography detects hypoventilation earlier than pulse oximetry. A respiratory rate below 8 to 10, shallow or irregular breathing, new snoring or airway obstruction, and falling saturation are all late relative to sedation.