Prospective Study of Postoperative Respiratory Depression Metrics After Cesarean Delivery Among Women Receiving Intrathecal Morphine
Authors' conclusion
We found no statistically significant differences in RR comparing 50 and 150 µg ITM, using continuous monitoring. Although the 150 µg group experienced a higher incidence of hypoxemia events, these were not clinically significant.
Study context
- Population
- Women undergoing non-emergency cesarean delivery with spinal anaesthesia
- Participants
- 80 women
- Exposure
- Intrathecal morphine (ITM) 50 µg vs 150 µg
- 50 µgn = 33reference
- 150 µgn = 46
- Transversus abdominis plane (TAP) blockn = 1
- Outcome
- Bradypnea (number of women with RR ≤ 8 breaths per minute) on continuous acoustic RR and SpO2 monitoring
- Follow-up
- Up to 12 hours postoperatively
Methodological detailssingle-centre
- Single-centre
Main finding
As reported in the abstract
Bradypnea
| Group | Value | Bradypnea events |
|---|---|---|
| 50 µg | 81.8% | 564 |
| 150 µg | 87.0% | 529 |
Value
50 µg81.8%
150 µg87.0%
Bradypnea events
50 µg564
150 µg529
Observational data: associations, not effects.
Further findings
| Outcome | 50 µg | 150 µg | P value |
|---|---|---|---|
| Duration of bradypnea per patient150 µg vs 50 µg · median | 1.58 (IQR 1.15–2.42) | 1.09 (IQR 0.83–1.70) | P < 0.001 |
| Bradypnea event rate150 µg vs 50 µg | 1.89 (95% CI 1.73–2.05) events per person-hour | 1.23 (95% CI 1.12–1.34) events per person-hour | P = 0.624 |
Timing of bradypnea
- Bradypnea occurred by 6 hours
- 62%
- Bradypnea events by 12 hours
- 86%
Safety
Median, sec
| Outcome | 50 µg | 150 µg | P value |
|---|---|---|---|
| Apnea and hypoxemia · up to 12 hours postoperatively150 µg vs 50 µg · hypoxemia duration significantly prolonged after 150 µg · per-group values are hypoxemia duration; order as printed | 48 (IQR 36–90) | 56 (IQR 40–106) | P = 0.001 |
Apnea and hypoxemia · up to 12 hours postoperatively
- Apnea and hypoxemia event rates similar
Respiratory events on nursing assessment; oxygen or naloxone requirement
- Nursing assessments per institutional protocol did not identify any respiratory events
- No woman required oxygen or naloxone administration
Original publication
Prospective Study of Postoperative Respiratory Depression Metrics After Cesarean Delivery Among Women Receiving Intrathecal Morphine. Anesth Analg. Published 5 March 2026. doi:10.
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